Coastal xeric scrub communities of the Treasure Coast region

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Title:
Coastal xeric scrub communities of the Treasure Coast region
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Book
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Fernald, Raymond T.

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University of Florida
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Table of Contents
    Cover
        Page i
        Page ii
    Executive summary
        Page iii
        Page iv
        Page v
    Table of Contents
        Page vi
        Page vii
    List of Tables
        Page viii
    List of Figures
        Page ix
    Acknowledgement
        Page x
    Preface
        Page xi
        Page xii
    Introduction
        Page 1
        Page 2
        Page 3
        Page 4
    Scrub community descriptions and ecology
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
    Endangered, potentially endangered, or endemic species
        Page 33
        Page 34
        Page 35
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
    Regulatory programs affecting scrub communities
        Page 45
        Page 46
        Page 47
        Page 48
    Criteria for scrub evaluation and preservation
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
        Page 58
        Page 59
        Page 60
    Current distribution and endangerment of scrub communities
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
    Preservation, restoration, and management of coastal scrubs
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
        Page 84
        Page 85
        Page 86
    Recommendations for implementation of a regional scrub preserve system
        Page 87
        Page 88
        Page 89
        Page 90
        Page 91
        Page 92
        Page 93
        Page 94
        Page 95
        Page 96
        Page 97
        Page 98
        Page 99
        Page 100
    Conclusion
        Page 101
    References
        Page 102
        Page 103
        Page 104
        Page 105
        Page 106
        Page 107
        Page 108
        Page 109
        Page 110
        Page 111
        Page 112
        Page 113
Full Text





COASTAL XERIC SCRUB COMMUNITIES OF THE
TREASURE COAST REGION, FLORIDA:

A Summary of Their Distribution and Ecology,
with Guidelines for Their Preservation and Management

NONGAME WILDLIFE PROGRAM TECHNICAL REPORT NO. 6


























UNIVERSITY OF FLaRTDA LIBRARIES

RAYMOND T. FERNALD
OFFICE OF ENVIRONMENTAL SERVICES
FLORIDA GAME AND FRESH WATER FISH COMMISSION
620 SOUTH MERIDIAN STREET
TALLAHASSEE, FLORIDA
32399-1600


JUNE 1989 ofy F:LORIDA LB0aPA









COASTAL XERIC SCRUB COMMUNITIES OF THE TREASURE COAST REGION,
FLORIDA: A SUMMARY OF THEIR DISTRIBUTION AND ECOLOGY, WITH
GUIDELINES FOR THEIR PRESERVATION AND MANAGEMENT.




NONGAME WILDLIFE PROGRAM TECHNICAL REPORT NO. 6


RAYMOND T. FERNALD
OFFICE OF ENVIRONMENTAL SERVICES
FLORIDA GAME AND FRESH WATER FISH COMMISSION
620 S. MERIDIAN STREET
TALLAHASSEE, FLORIDA
32399-1600


SCIENCE
LIBRARY


JUNE 1989




Suggested reference:


Fernald, R. T. 1989. Coastal xeric scrub communities of the Treasure Coast Region, Florida: A summary of their
distribution and ecology, with guidelines for their preservation and management. Florida Game and Fresh Water Fish
Commission, Nongame Wildlife Program Technical Report No. 6. Tallahassee, FL. 125 pp.






EXECUTIVE SUMMARY


The Treasure Coast Region encompasses four Atlan-
tic coastal counties of east-central Florida, including
Indian River, Saint Lucie, Martin, and Palm Beach.
These counties possess a great diversity of native
upland communities, many of which rapidly are being
displaced by land development or disturbed by other
human activities. Foremost among these endangered
upland habitats are the coastal scrub communities,
including scrubs and scrubby flatwoods.
Scrubs and scrubby flatwoods are found almost
exclusively in Florida on well-drained and infertile
sands of relict dunes, bars, and other marine or aeolian
features. The vegetation is typically two- or three-
layered, with sand pine often occupying the canopy,
and scrubby oaks and other shrubs, vines, and lichens
comprising the sparse to dense, often clumped, under-
story. Little herbaceous ground cover exists, and large
areas of bare sand occur frequently. Typical understory
plants include myrtle oak, scrub live oak, Chapman's
oak, scrub hickory, rosemary, staggerbush, hog plum,
prickly-pear cactus, muscadine grape, sand spikemoss,
and several lichens. Many scrub plant species are consi-
dered Endangered, Threatened, or Commercially Exploited
by state or federal agencies. Scrubby flatwoods are
comprised of predominantly the same species, but sand
pines are absent; they may be replaced by slash pine or
southern longleaf pine. Scrubby pine flatwoods may
also possess a greater complement of species more
characteristic of typical pine flatwoods such as three-
awn, fetterbush, tarflower, dwarf huckleberry, gall-
berry, and wax myrtle. Delineation between these
communities may be vague, as they are often inter-
mixed. Past timbering operations, drainage practices,
land clearing activities, or fire frequency often deter-
mine which community occupies a site. Invasion by
exotic species is common in some areas, and may
further complicate classification of an area as a scrub
community or simply as a disturbed site possessing
some vestiges of scrub vegetation.
The faunae of these habitats are diverse, and vary
greatly depending on site characteristics and the nature
of adjoining communities. Characteristic animals
include bobcat, raccoon, gray squirrel, Virginia opos-
sum, rufous-sided towhee, white-eyed vireo, Carolina
wren, great-crested flycatcher, red-bellied woodpecker,
eastern screech-owl, eastern diamondback rattlesnake,
southern black racer, eastern coachwhip, southeastern
five-lined skink, six-lined racerunner, green anole,
gopher tortoise, southern toad, and oak toad. Of par-
ticular interest are animals which are endemic to scrubs
and associated xeric habitats, including tht Florida
mouse, Florida scrub jay, scrub lizard, red widow
spider, and others. A significant number of scrub spe-
cies are officially listed as Threatened or as Species of


Special Concern including the Florida mouse, Florida
scrub jay, gopher tortoise, eastern indigo snake, Florida
pine snake, and gopher frog.
Scrubs are essentially fire-maintained communities.
Ground vegetation is generally sparse, leaf fall is min-
imal, and oxidation of dead plant material is extremely
rapid, thus reducing the chance of frequent ground
fires. As sand pines (where present) mature, however,
they retain most of their branches and build up large
fuel supplies in the crowns. Other scrub shrubs also
increase in height and density during long fire-free
intervals. This fuel supply, in combination with the
resinous sand pine needles and high stand density,
ensures a hot, fast-burning fire. Such fires occur about
every 20 to 70 years, and facilitate regeneration of the
community. Scrubby flatwoods are also fire-dependent
associations, but their burning interval is normally
about 3 to 15 years.
Historically, scrubs formed a virtually continuous
zone along the Atlantic Coastal Ridge throughout the
region. This habitat continuity facilitated long-term
preservation of the biota, with extirpated populations
being replaced via immigration from adjacent scrubs.
As portions of the scrub system were developed, this
habitat corridor was radically fragmented such that
these communities now persist as islands surrounded
by developed or disturbed lands. As a result, these
smaller, insular populations are more likely to suffer
local extirpation, and less likely to colonize suitable
habitat.
Currently, there is very little unthreatened scrub or
scrubby flatwoods habitat in the region, except for
existing preserves at Jonathan Dickinson State Park,
Hobe Sound National Wildlife Refuge, Savannahs
State Preserve, and the Loxahatchee Wild and Scenic
River corridor. These four preserves include approxi-
mately 5,000 acres of scrub and scrubby flatwoods
communities. The remainder of the region's scrub hab-
itat consists of seminatural tracts of undeveloped land
along the Atlantic Coastal Ridge, small tracts in utility
rights-of-way, vestiges of the native community left as
"natural areas" within major developments, and
smaller knolls or ridges along major river corridors or
in broad flatwoods. Along the Atlantic Coastal Ridge,
nearly all of the remaining significant scrub tracts are
currently proposed for development or are for sale.
This inventory revealed that, excluding the four
major preserves listed above, there are an estimated
10,673 acres of "viable" coastal scrub and scrubby
flatwoods remaining in the Treasure Coast Region.
This acreage is distributed among the counties as fol-
lows: Indian River - 3,263 acres; Saint Lucie - 1,452
acres; Martin - 3,611 acres; and, Palm Beach - 2,347
acres. Palm Beach County serves as a foreboding exam-








pie of scrub decline throughout the region: over 95
percent of that county's scrub resources have been
destroyed by human activities since the turn of the
century.
Human activities are responsible for virtually all of
the existing threat to these natural communities, with
land development exerting the most unrelenting pres-
sure. Treasure Coast scrubs are especially valuable as
development sites for several reasons. First, they are
predominantly located near the Atlantic coast, where
development pressure is greatest. Second, they offer
tremendous development potential since flooding is
not a significant threat and landfilling is unnecessary.
Finally, because they occupy the highest coastal ridges,
railroad and highway construction historically occurred
first in these communities, predisposing them to sub-
sequent development.
There are several other human activities which
severely impact these communities. Off-road vehicles
have criss-crossed many scrubs with impromptu trails,
and illegal dumping of excess or waste construction
materials, abandoned cars and appliances, or house-
hold garbage is widespread. Resulting elimination of
sprouting species through destruction of root and
underground stem systems, and changes in water and
light patterns accompanying such activities, may facili-
tate invasion by Brazilian pepper, cypress pine, Austral-
ian pine, and other exotic vegetation. Similarly, humans
are responsible for introduction of domestic dogs and
cats, black rats, greenhouse frogs, giant toads, Cuban
treefrogs, brown anoles, and a host of other exotic
animal species. Although many exotics simply occupy
disturbed sites which no longer provide suitable habitat
for native species, some actively prey upon, or compete
with, the native biota.
Another factor in the demise of scrub communities is
their dependence upon fire for community regenera-
tion. Because they are often partially developed or sur-
rounded by developed lands, suppression of wildfire is
the norm. Resulting overgrowth leads to decline of
herbaceous species diversity and abundance, and
reduction in the percentage of bare ground. These habi-
tat characteristics are important to Florida scrub jays,
scrub lizards, gopher tortoises, and other scrub species.
Fire exclusion also predisposes a tract to disastrous
wildfire due to the tremendous fuel buildup.
The regulatory structure regarding upland develop-
ment and environmental protection is essentially a
four-layer hierarchy involving federal, state, regional,
and local governments. At the federal level, there are
several regulatory programs of particular application to
upland development or protection of native wildlife.
Foremost among these are the National Environmental
Policy Act, the Endangered Species Act of 1973 and


amendments, the Migratory Bird Treaty Act, and the
Migratory Bird Conservation Act.
Major components of Florida law which directly
address scrub species or development activities in scrub
habitats include the Environmental Land and Water
Management Act of 1972, the State Comprehensive
Plan and the Growth Management Act of 1985, the
Wildlife Code of the State of Florida, the Florida
Endangered and Threatened Species Act, and the Pres-
ervation of Native Flora of Florida Act.
The most promising state program with regard to
scrub preservation includes the planning and policy
requirements mandated by the State Comprehensive
Plan, the Growth Management Act, and associated leg-
islation, much of which is implemented through
regional and local government. This regional control
over upland development and protection of native hab-
itats and wildlife is primarily vested in the Treasure
Coast Regional Planning Council via the Development
of Regional Impact review process. The council is an
extremely powerful force in determining the extent and
character of development permitted in, or protection
granted to, these natural communities. The Regional
Comprehensive Policy Plan contains significant policy
statements regarding natural resource protection.
At the local level, each comprehensive plan is replete
with policy statements and natural resource protection
objectives; but, unfortunately, these are ineffectual
unless implemented by county ordinances. To date,
local government has been ineffective in protecting
scrub habitats. If significant representative tracts of
these communities are to be preserved, local govern-
ment,must make a commitment to their preservation
and management.
Determining the best method of preserving and man-
aging scrub resources is a complex issue. Current
regional and local land use regulations seek to preserve
a percentage of valuable habitat on each development
tract. Unfortunately, such a piecemeal approach to
habitat preservation results in loss of viable scrub
communities; degradation of remaining scrubs which
were "preserved"; and local or regional extirpation of
Endangered, potentially endangered, or endemic spe-
cies. The recommended approach includes establish-
ment of a Regional Scrub Preserve System by local and
regional government. Scrub preserves would be estab-
lished throughout the region, and would be supported
by a comprehensive scrub management policy and pro-
gram, and by long-term monitoring and research. Pri-
mary duties of regional government would include
assisting with purchase or preservation of scrub tracts
as requested by local government, overseeing manage-
ment and restoration activities on established pre-
serves, and maintaining computerized maps and data-









bases for the preserve system. Local responsibilities
would include selection, acquisition, and management
of preserve tracts.
Selection of preserve tracts is perhaps the most criti-
cal component of establishing a scrub preserve system.
The species-area relationship, island biogeographic
theory, and concepts of minimum viable populations
often have been applied to conservation of natural
communities or populations with insular distribution.
There is much debate, however, over the merits of these
approaches to nature preserve design. Review of these
issues, and recognition of the pragmatic constraints of
fiscal responsibility and habitat management require-
ments, lead to the following conclusions regarding
preservation and management of scrub communities in
the Treasure Coast Region:

1. While many large refuges would be most
desirable, the most practical solution is to main-
tain a core of relatively large (greater than 500
acres) preserves, and establish as many smaller
refuges as possible to preserve Endangered, poten-
tially endangered, or endemic species; samples of
intact communities throughout the region; corri-
dors or "stepping stones" between relatively iso-
lated tracts; and genetic variation within scrub
species.
2. Minimum preserve size will vary exten-
sively with the species or community being pre-
served, down to a practical (for management pur-
poses) minimum of about 10-15 acres for botani-
cal preserves, 15-30 acres per territory for Florida
scrub jay preserves, and 50 acres for scrub com-
munity preserves.
3. Management implications may be the most
important factor in determining both the optimal
size of a preserve and its probability of success.
Individual refuges should be established based on
the specific needs of the taxa or community to be
managed.


Additional programs which could be effective in pre-
serving native scrub communities include comprehen-
sive land use planning, site planning, mitigation for
unavoidable adverse impacts of development, transfer
of development rights, and financial incentives for
preservation of privately owned scrub tracts. Effective
ordinances concerning zoning, land clearing, sand min-
ing, native landscaping, off-road vehicle use, litter dis-
posal, domestic animal control, and tree protection
could enhance local protection efforts for these habi-
tats. Additional conservation programs of potential
significance include posting of wildlife crossings,
"Champion Tree" programs, environmental educa-
tion, and more conservation-minded management of
publicly owned lands.
Continued land development and human population
growth in the Treasure Coast Region will be accommo-
dated, and a substantial percentage of that growth will
be targeted at the remaining coastal uplands. Regional
and local government and concerned citizens, within
the state and federal regulatory framework, will deter-
mine whether such growth permits steady deterioration
of resources and human lifestyle, or effects an enlight-
ened attitude of compromise which will preserve these
irreplaceable natural assets. Through adoption of a
substantial program to preserve, manage, and restore
scrub habitats, the natural uniqueness and beauty of
these communities can be preserved within the Trea-
sure Coast Region for many future generations of resi-
dents and visitors.






TABLE OF CONTENTS


EXECUTIVE SUMMARY ...................................................................... iii
LIST OF TABLES ............................................................................ viii
LIST O F FIGURES ............................................................................ . ix
ACKNOW LEDGEMENTS ...................................................................... x
PREFACE ..................................................................................... xi

INTRODUCTION .............................. ......... ....................................... 1

SECTION 1: SCRUB COMMUNITY DESCRIPTIONS AND ECOLOGY

GEO LOGY .................................................................................... 6
SO ILS ........................................................................................ 7
Excessively Drained Ridge Soils ................................................................ 9
Primary Scrub Soils ........................................................................... 9
Secondary Scrub Soils ......................................................................... 9
M inor Scrub Soils............................................................................ 10
VEGETATION ................................................................................ 11
Scrubs ...................................................................................... 11
Scrubby Flatwoods........................................................................... 13
Pine Flatwoods .............................................................................. 17
W ILDLIFE ................................................................................... 20
M amm als ................................................................................... 20
Birds ....................................................................................... 20
Reptiles and Amphibians................................................................... 22
ECOLOGY ................................................................................... 24
Distribution................................................................................. 26
Fire ........................................................................................ 27
Natural Succession ........................................................................... 28
Human Impacts.............................................................................. 30

SECTION 2: ENDANGERED, POTENTIALLY ENDANGERED, OR ENDEMIC SPECIES

VERTEBRATES....................................... ....................... ................ 34
Florida M ouse............................................................................... 34
Florida Scrub Jay ............................................................................ 34
Gopher Tortoise ............................................................................. 36
Scrub Lizard ................................................................................ 39
Eastern Indigo Snake ......................................................................... 40
Florida Pine Snake ........................................................................... 40
Gopher Frog ................................................................................ 41
INVERTEBRATES ............................................................................ 42
PLANTS ..................................................................................... 42

SECTION 3: REGULATORY PROGRAMS AFFECTING SCRUB COMMUNITIES

FEDERAL AUTHORITY...................................................................... 46
STATE AUTHORITY......................................................................... 46
REGIONAL AUTHORITY .................................................................... 47
LOCAL AUTHORITY ........................................................................ 47

SECTION 4: CRITERIA FOR SCRUB EVALUATION AND PRESERVATION

SPECIES-AREA RELATIONSHIPS AND ISLAND BIOGEOGRAPHIC THEORY ..................... 50
MINIMUM VIABLE POPULATION SIZE ........................................................ 52
GENERIC PRESERVE DESIGN ................................................................ 54








IMPLICATIONS FOR SCRUB PRESERVE DESIGN .............................................. 55
Minimum Area for Regional Scrub Preserves .................................................... 55
Minipreserves and Corridors................................................................... 57
SCRUB PRESERVE SELECTION .............................................................. 58
SUM M ARY .................................................................................. 59

SECTION 5: CURRENT DISTRIBUTION AND ENDANGERMENT OF SCRUB COMMUNITIES

M ETHODS ................................................................................... 62
Community Description Code ................................................................ 62
RESU LTS .................................................................................... 63
Indian River County.......................................................................... 65
Saint Lucie County........................................................................... 65
M martin County .............. ................................................................ 65
Palm Beach County .......................................................................... 76
INTERPRETATION OF SOIL AND SCRUB DATA ............................................... 76
DISCUSSION ................................................................................. 77

SECTION 6: PRESERVATION, RESTORATION, AND MANAGEMENT OF COASTAL SCRUBS

A REGIONAL SCRUB PRESERVE SYSTEM .................................................... 80
Government Authority and Responsibilities..................................................... 80
Scrub Preserve Classification................................................................... 81
Scrub Preserve Acquisition ................................................................... 81
Scrub Preserve Management .................................................................. 82
Research and Monitoring ................... .... .. ..... .......................... ............. 83
OTHER PROGRAMS FOR SCRUB CONSERVATION ........................................... 83
Government Planning and Policy .............................................................. 84
Local Ordinances ............................................................................ 85
Community Conservation Programs ........................................................... 86
Environmental Education .................................................................... 86

SECTION 7: RECOMMENDATIONS FOR IMPLEMENTATION OF A REGIONAL SCRUB
PRESERVE SYSTEM

POTENTIAL SITES FOR REGIONAL SCRUB PRESERVE ESTABLISHMENT ...................... 88
Indian River County .......................................................................... 88
Saint Lucie County........................................................................... 90
M martin County .............................................................................. 92
Palm Beach County .......................................................................... 95
GUIDELINE IMPLEMENTATION ............................................................. 99
Regional Implementation..................................................................... 99
Local Implementation ........................ ... ..... . ..... ................................ 99

CONCLUSION ............................................................................. 101
REFERENCES ............................................................................. .. 102






LIST OF TABLES


Table 1. Plants of coastal scrubs in the Treasure Coast Region ...................................... 11
Table 2. Mammals of coastal scrubs in the Treasure Coast Region ................................... 22
Table 3. Birds of coastal scrubs in the Treasure Coast Region ....................................... 22
Table 4. Reptiles of coastal scrubs in the Treasure Coast Region..................................... 25
Table 5. Amphibians of coastal scrubs in the Treasure Coast Region ................................. 2(
Table 6. Gopher tortoise commensal vertebrates which occur in coastal scrubs of the Treasure
Coast Region ........................................................................ 3E
Table 7. Distribution of scrub soils and habitats in the Treasure Coast Region ......................... 63






LIST OF FIGURES

Figure 1. General distribution of scrubs in Florida........................................... 2
Figure 2. The Treasure Coast Region ...................................................... 3
Figure 3. The coastal scrub study area ..................................................... 8
Figure 4. Sand pine scrub ............................................................... 12
Figure 5. Foliage and cones of sand pine .................................................. 12
Figure 6. Scrub live oak, and contrasting foliage of scrub oak species .......................... 13
Figure 7. Lichens, sand spikemoss, and bare sand typical of scrub ground cover .................. 7
Figure 8. Scrubby pine flatwoods ........................................................ 18
Figure 9. Scrubby oak flatwoods ......................................................... 18
Figure 10. Pine flatwoods ................................................................ 19
Figure 11. Fruits of characteristic scrub shrubs .............................................. 21
Figure 12. Osprey nest in a sand pine snag ................................................. 24
Figure 13. Overgrown scrubby flatwoods ................................................ 31
Figure 14. Human-related disturbances to scrub communities ................................. 32
Figure 15. Florida m house ................................................................ 34
Figure 16. Florida scrub jay .............................................................. 35
Figure 17. Tam e Florida scrub jays ........................................................ 35
Figure 18. Gopher tortoise ............................................................... 36
Figure 19. Foraging trail of a gopher tortoise............................................. 37
Figure 20. Active and inactive gopher tortoise burrow entrances ............................... 37
Figure 21. A gopher frog in an active tortoise burrow ........................................ 39
Figure 22. Scrub lizard .................................................................. 39
Figure 23. Eastern indigo snake ........................................................... 40
Figure 24. Florida pine snake ............................................................. 41
Figure 25. Florida gopher frog ............................................................ 41
Figure 26. Red widow spider ............................................................. 42
Figure 27. Federally Endangered plants which occur in Treasure Coast scrubs .................... 43
Figure 28. Threatened or Commercially Exploited plants which occur in Treasure Coast scrubs ....... 44
Figure 29. Potential scrub soils in the coastal study area ..................................... 64
Figure 30. Potential scrub soils in Indian River County ....................................... 66
Figure 31. Remaining scrub tracts in Indian River County .................................... 67
Figure 32. Potential scrub soils in Saint Lucie County ....................................... 68
Figure 33. Remaining scrub tracts in Saint Lucie County .................................... 69
Figure 34. Potential scrub soils in Martin County .......................................... 70
Figure 35. Remaining scrub tracts in Martin County ........................................ 71
Figure 36. Potential scrub soils in Palm Beach County....................................... 72
Figure 37. Remaining scrub tracts in Palm Beach County ..................................... 74
Figure 38. Contrasting examples of landscaping with native vegetation .......................... 84
Figure 39. Potential scrub preserves for Indian River County .................................. 89
Figure 40. Potential scrub preserves for Saint Lucie County ................................... 91
Figure 41. Potential scrub preserves for Martin County ...................................... 93
Figure 42. Potential scrub preserves for Palm Beach County.................................. 96
Figure 43. Juno Hills scrubby oak flatwoods - coastal strand ................................. 98
Figure 44. Sand pine scrub preserved on a privately owned golf course ........................ 100








ACKNOWLEDGEMENTS


Many individuals within and outside of the Florida Game and Fresh Water Fish Commission contributed
significantly to production of this report. I am especially indebted to the Treasure Coast Regional Planning Council
for their encouragement and recommendations throughout the project, and for provision of essential computer
equipment and personnel. The persistence and patience of Billie Dugger, Alan Levy, and Anne Cox, who transcribed
and digitized the entire scrub inventory from hardcopy into AutoCad format, are greatly appreciated. Consultation
with Dan Cary, Michael Busha, Dr. Peter Merritt, and Sally Black provided valuable feedback throughout this study.
Sally Black was especially helpful in refining the scrub plant species list.
I am also indebted to the South Florida Water Management District. Patrick Edmundson and Teresa McRorie, of
that agency's Division of Geographic Sciences, provided data processing services which were vital to completion of
this project.
Several individuals provided insight or advice concerning particular species of interest. Those discussions with Dr.
Jack Stout, Dr. Glen Woolfenden, Dr. James Layne, Paul Moler, and Jim Cox were especially informative.
Review and constructive criticism of project drafts were provided by several persons within the Commission,
including Randy Kautz, Brian Barnett, Jim Cox, Mark Robson, and Brian Toland. Reviewers of the completed
manuscript included Dr. Dan Austin, Dr. Don Richardson, Dick Roberts, Christopher Bove, Kay Brennan, Roland
DeBlois, and Daniel Saskowski, in addition to the previously mentioned personnel of the regional planning council.
The recommendations and comments of these reviewers were particularly valuable during editing of the final report.
Photographic credits are extended to Dr. Peter Merrit (Curtiss milkweed), Brian Toland (Florida pine snake and
Florida mouse), Richard Moyroud (four-petal pawpaw), and Anne Malsbary (Lakela's mint).
Finally, I appreciate the support and patience provided by my supervisors, Brian Barnett and Randy Kautz, during
this project. Their acceptance of significant delays associated with completion of this report is gratefully acknow-
ledged. Both persons were instrumental in development of the original project concept, and reviewed various project
drafts. Randy was project supervisor during my 2 years with the nongame wildlife program, and provided invaluable
recommendations regarding format and content of the final report.










PREFACE


Regulation of development activities in uplands is a
complex and politically volatile issue. The dilemma
perhaps was best summarized in background docu-
ments (Treasure Coast Regional Planning Council,
unpubl. ms: 10.1.3-4) drafted during preparation of the
Treasure Coast Regional Comprehensive Plan (Trea-
sure Coast Regional Planning Council 1987):

"Almost all arguments over natural system
preservation are based on property rights and
interests in deriving the maximum possible eco-
nomic return for privately owned lands.... this
problem might be best resolved by adoption of
stronger policies protecting natural systems and
through encouragement of supporting actions.
These actions might include developing current
habitat and wildlife inventories and manage-
ment guidelines, providing fiscal incentives
(i.e., tax breaks) to encourage private protec-
tion and restoration, and encouraging the use of
methods which transfer development from non-
suitable lands to suitable lands.




"Factors contributing to the reduction of natu-
ral system function and value include lack of
updated habitat and wildlife inventories, lack of
habitat and wildlife management guidelines,
lack of comprehensive protective actions and
ordinances, fragmentation of habitat distribu-
tion and wildlife corridors, lack of long-range
acquisition programs, lack of private protection
and restoration incentives, and lack of public
restoration programs."


This report is intended to address these needs with
regard to scrub habitats in coastal areas of the Treasure
Coast Region. It is primarily a synthesis of published
and unpublished research, an inventory of existing
scrub tracts in the region, and a guideline for preserva-
tion and management of remaining resources. It is not a
panacea: it is intended as a framework on which to
build a comprehensive program of scrub preservation
and management.
Some progress is being made. Palm Beach County
has endorsed a Wilderness Island Preservation Pro-
gram, and is compiling an inventory of remaining native
habitats, though no funds have been established to
acquire valuable tracts. Martin County has a relatively
new landscaping ordinance which addresses many habi-
tat preservation issues. Martin County also cooperated
with the Florida Game and Fresh Water Fish Commis-
sion, Treasure Coast Regional Planning Council, and a
private developer in establishing a 40-acre Florida
scrub jay preserve on a Development of Regional
Impact site. Indian River County recently declined to
purchase a 100-acre tract of scrub for a nature preserve,
and rejected a proposed Coastal Sand Ridge Protection
Ordinance, but remains open to discussion of scrub
preservation. Several scrub tracts in the Treasure Coast
Region have been proposed for acquisition via the
CARL (Conservation and Recreation Lands) program.
One tract (South Savannas) is currently 16th on the
prioritized list of 69 projects (Florida Department of
Natural Resources 1988a), and the Yamato and Sea-
branch scrubs have been approved for CARL project
design. These efforts are applauded, but they must be
expanded if scrub communities are to be preserved on a
regional basis. Scientists, politicians, conservationists,
and concerned citizens must unite in a common effort if
we are to protect these vital components of our natural
heritage.


































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INTRODUCTION


In his report on Florida dunes and scrub, Kurz
(1942) wrote: "While there is yet a choice of selection,
large coastal parks should be established in order to
preserve as samples for all time some of the very kind of
primeval beauty and things of nature that have helped
to make Florida." Unfortunately, his vision into the
future was not quite equal to his concern, as illustrated
by the following statement made a few paragraphs later:
"A special plea for the conservation of scrubs seems
superfluous. Remoteness from and disrelation to salt
water surf as well as undesirability for cultivation con-
stitutes ample protection."
Scrubs and scrubby flatwoods, as defined in this
report, are found almost exclusively in Florida (Figure
1). Historically, they formed a virtually continuous
zone along the Atlantic Coastal Ridge throughout the
Treasure Coast Region which includes Indian River,
Saint Lucie, Martin, and Palm Beach counties (Figure
2). During the last century this habitat corridor has
been radically fragmented such that these communities
now persist as islands surrounded by developed or
disturbed lands. In the Treasure Coast Region, they
constitute truly endangered upland habitats.
Human activities are singularly responsible for the
decline of these communities. Because scrubs and asso-
ciated xeric habitats occupy the highest coastal ridges,
railroad and highway construction historically dis-
placed them first, and predisposed adjacent areas to
subsequent development. Residential and agricultural
development has exerted the most unrelenting pres-
sure. Off-road vehicle use, illegal dumping, sand min-
ing, drainage practices, exotic species, and disruption of
the natural fire regime comprise other significant
threats attributable to modern man.


Consequently, there is very little unthreatened scrub
or scrubby flatwoods habitat in the region, except for
existing preserves at Jonathan Dickinson State Park,
Hobe Sound National Wildlife Refuge, Savannahs
State Preserve, and the Loxahatchee Wild and Scenic
River corridor. These preserves aside, most of the
region's remaining scrub habitat consists of seminatu-
ral tracts of undeveloped land along the Atlantic Coast-
al Ridge, small tracts in utility rights-of-way, vestiges of
the native community left as "natural areas" within
major developments, and smaller knolls or ridges along
major river corridors or in broad flatwoods. Along the
Atlantic Coastal Ridge, nearly all of the significant
privately owned scrub tracts are currently proposed for
development or are for sale.
This report provides recommendations for preserv-
ing and managing what remains of these natural resour-
ces. Major sections pertain to description of scrub
communities, criteria for nature preserve selection,
scrub distribution and endangerment, and options for
scrub preservation and management. The central theme
is establishment of a Regional Scrub Preserve System, for
only by preserving significant tracts of scrub can these
resources be managed as natural communities. The
other pivotal issue concerns local and regional accoun-
tability. State and federal government can contribute
significantly, but they have neither the resources nor
the authority to implement a comprehensive scrub
management program. Responsibility for
implementation of these guidelines must be borne by
area residents and elected officials.










































APPROXIMATE SCALE
1" = 70 MILES


Figure i. General distribution of scrubs in Florida (adapted from Davis 1967, Soil Conservation Service 198i).



















































APPROXIMATE SCALE
1" = 12.6 MILES


JUPITER

JUNO
BEACH





PALM
BEACH




BOYNTON
BEACH

DELRAY
BEACH


BOCA
RATON


Figure 2. The Treasure Coast Region.


































































4














SECTION 1.

SCRUB COMMUNITY

DESCRIPTIONS AND ECOLOGY







GEOLOGY


Scrub community distribution and characteristics
are entwined with Florida's geological history, which
has largely determined elevations, topography, and
poils.1Thus, to understand scrub distribution and com-
position, we must appreciate the geologic origins of the
study area.
//The Treasure Coast Region lies within the Atlantic
Coastal Lowlands physiographic region of Florida
(Cooke 1939, Puri and Vernon 1964, Florida Depart-
ment of Natural Resources 1975). The coastal study
area possesses less than 100 feet of topographic relief,
virtually all of which is expressed in the upper sedimen-
tary deposits of Pleistocene (Ice Age) or Holocene
(Recent) origin. These strata consist of various lime-
stones, sandstone, coquina, shell, marl, and sand with a
total depth of generally less than 300 feet. Undifferen-
tiated sands and soils of the coastal ridges are underlain
primarily by the Anastasia Formation, with the Miami
Limestone occurring in southern Palm Beach County.
These formations merge with the Fort Thompson and
Caloosahatchee formations to the wst, and are often
underlain by them in coastal areas. The composition
and areal extent of these for tions have been
reviewed, and often revised, in many geological studies
(Cooke 1939, Davis 1943, Schroeder et al. 1954,
Lichtler 1960, Puri and Vernon 1964, Land et al. 1973,
Brooks 1981, Tanner and Smith 1981, Missimer
1984). Generally, these sediments were deposited
through sedimentation and biogenesis during inunda-
tion by shallow seas associated with Pleistocene and
Holocene sea level fluctuations (except that the Caloo-
sahatchee Formation is considered to have originated in
both the Pliocene and Pleistocene epochs), though
there has been much debate concerning the delineation
and ages of various strata (Cooke 1939, Davis 1943,
MacNeil 1949, Lichtler 1960, Weigel 1962, Puri and
Vernon 1964, Alt and Brooks 1965, White 1970,
Missimer 1984).
The Pleistocene epoch, approximately 1.6 to 0.01
million years BP (Before Present), was characterized by
dramatic sea level fluctuations associated with circum-
polar glacial advances and recessions. During this
period, unconsolidated siliceous sands and clays were
transported from the Appalachians and Piedmont of
the Carolinas and Georgia. Easterly flowing rivers such
as the Savannah and the Altamaha carried these mate-
rials to the Atlantic Ocean, from whence southerly
longshore currents transported them to the peninsula
(Laessle 1958, Tanner and Smith 1981). There they
were deposited along with sediments of marine origin
(Laessle 1958, Missimer 1984).
The last (Wisconsin) glacial age is generally consi-
dered to have included three distinct substages, includ-
ing early and late glacial substages, and the Peorian
interglacial (Cooke 1939 [in part], Davis 1943 [in


part], MacNeil 1949, Puri and Vernon 1964, Richard-
son 1977). During the Peorian interglacial, the Pamlico
Sea reached an elevation about 25-30 feet above cur-
rent sea level. Much of the original deposition, and
erosional or aeolian restructuring, of coastal relict
ridges is attributed to this Pamlico Sea and the glacial
periods which immediately preceded and followed it,
though various researchers have debated the ages of the
"Pamlico Terrace" and other coastal sediments, and
whether the coastal ridges were submerged bars, barrier
islands, or mainland shorelines of Pamlico or pre-
Pamlico seas and lagoons (Cooke 1939, Davis 1943,
MacNeil 1949, Lichtler 1960, Weigel 1962, Puri and
Vernon 1964, White 1970, Richardson 1977, Missi-
mer 1984).
After the last glacial age peaked about 17,000 years
BP, sea level began to rise to its present level (Russell
1957, Fairbridge 1984). This rise was not a steady
curve, but a series of transgressions (sea level rises),
pauses, and regressions throughout the Holocene
(approximately 10,000 years BP to present). Again, the
rate of sea level rise, number of transgressions, and date
at which sea level reached its approximate current
height are debated (Scholl et al. 1969, Fairbridge 1984,
Robbin 1984). There is general agreement, however,
that the approximate current sea level was attained
within the last 6,000 years (Russell 1957, Tanner and
Smith 1981, Fairbridge 1984, Robbin 1984).
Mulvania (1931), Kurz (1942), Laessle (1942,
1958), and Davis (1943) all realized that many scrubs
occupy ancient dunes formed along Pleistocene shore-
lines, some as high as 100 feet to 150 feet above present
sea level. Kurz (1942) also pointed out that, with very
few exceptions, the plants distinctive of scrub are also
found on relatively recent coastal dunes, and that some
scrubs of flatwoods ridges in southern and eastern Flor-
ida might occupy old wave-formed bars or ridges.
These researchers reached essentially similar conclu-
sions regarding the origins and soils of scrub communi-
ties, i.e.: "Whatever the nature of these old topogra-
phic features, their white sands, all of Pleistocene seas,
are similar and consistently inhabited by scrub vegeta-
tion" (Kurz 1942); and, "that scrub is a typical stage in
dune succession or, at least, that it occurs on deposits of
marine sands that were strongly washed and sorted as
are bars and beaches" (Laessle 1942). Laessle
(1958:363-364) expounded on his position further by
proposing several potential means of development of
these sandy soils:

"... it is apparent that the soils supporting these
scrubs possess two common factors, (a) the
soils are nearly pure siliceous sand, and (b) that
these sands are extremely well-drained.'These
two conditions have apparently arisen in at least






the following ways: 1. Dune deposits back of
shore lines both Pleistocene and Recent, the
sands having previously been strongly washed
and sorted by marine currents and wave action.
2. Pleistocene beaches and bars associated with
marine shorelines of strongly washed and sorted
sands that attained and retained good drainage
after the recession of the sea. 3. Submerged
hilltops that were covered for considerable time
by water, shallow enough to allow strong wash-
ing, sorting, and leveling of the top by subsur-
face wave action. It has been shown that this
type of wave action has little effect on unconsol-
idated sediments at depths much over 6 fathoms
(Russell 1957). 4. Sand deposits washed and
sorted by deep marine currents, such sands hav-
ing good drainage after recession of the sea. 5.
Wave-washed shores of freshwater lakes - pro-
viding that such lake levels receded slowly due
to gradual lowering of the water table as by
solution of underlying limestone. There is pos-
sibly still another method - that of strongly
washed and sorted sands of fluvial origin - but
scrubs formed in this manner would be small
because of the lack of gradient and compara-
tively small volume of flow of streams in the
region studied."

Laessle (1958) stated that scrubs of dune origin are
the most widely recognized because they are readily
observed back of present shorelines, and because their
presence behind higher Pleistocene shorelines is readily
detected from the more or less parallel ridges of sand.
Though he acknowledged that a series of parallel off-
shore sand bars, on emergence from the sea, could
simulate a series of shallow dunes, Laessle (1958:365)
felt that scrubs formed on sand deposits of beach and
offshore bars were not as common as might be
expected, explaining their scarcity as follows:

"Many of these ancient shores, even when bor-
dering open seas, were on the lee shores to
strong prevailing winds and hence subject to
only the mildest type of wave action. Many of
the more exposed shores were subject to ero-
sion rather than accumulation. Also, as men-
tioned previously, excellent drainage must obtain
after old shore lines and bars are exposed by the
receding sea. Frequently there was not enough
topographic irregularity to insure good drainage
and many ancient bars and beaches of well-
washed and sorted sands are therefore occupied
by 'flatwoods' vegetation. However, some of
the better drained areas are occupied by
'scrubby flatwoods' (Laessle 1942) and similar
vegetation (Kurz 1942)."

Atlantic Coastal Ridge scrubs in the Treasure Coast
Region consist of such dunes, beaches, bars, and other


formations associated with Pleistocene and Holocene
inundations. Cooke.(1939) inferred that most dunes
near the east coast and south of Daytona Beach are
probably of Holocene origin. Laessle (1958) felt that
inland Pamlico dunes are extensive near the Atlantic
coast, and prominent from Jacksonville south at least as
far as West Palm Beach. He was insistent that at least
some of the very high dunes in Martin County, between
Hobe Sound and Jupiter, are of Pamlico origin. Lichtler
(1960) stated that the Atlantic Coastal Ridge in Martin
County was probably of pre-Pamlico origin, and was
dissected and otherwise modified by advance of the
Pamlico Sea. Richardson (1977) presented much the
same scenario for the ridges of Palm Beach County.
White (1970) convincingly argued that the Atlantic
Coastal Ridge represents the erosional, mainland beach
ridge which surmounts the crest of the Pamlico Sea
transgression. Austin et al. (1987) identified seven
major coastal ridges in Palm Beach County, and believe
the patterns and origins of these ridges may be much
more complex than formerly suspected.
In addition, two relatively minor ridges occur within
the Eastern Valley (Watts and Stankey 1980, Wett-
stein et al. 1987) and Eastern Flatlands (McCollum and
Cruz 1981) physiographic units of the study area. Ten
Mile Ridge branches off of the Atlantic Coastal Ridge
north of Eau Gallie in Brevard County, and diverges
southwesterly along the eastern margin of the Upper
Saint Johns River Marsh. This ridge gradually loses
elevation until it becomes indeterminate about 5 miles
south of the Indian River - Saint Lucie county line
(White 1970, Watts and Stankey 1980, Wettstein et
al. 1987). The Green Ridge lies along the eastern boun-
dary of Allapattah Flats in Saint Lucie and Martin
counties (Lichtler 1960, White 1970, Watts and Stan-
key 1980, McCollum and Cruz 1981). Lichtler (1960)
felt that the Green Ridge was probably an offshore bar
with its crest at about sea level during the Pamlico
epoch. White (1970), however, maintained that both
of these ridges are relict, erosional shorelines of pre-
Pamlico Pleistocene transgressions. These ridges, and
the wetlands west of them, delineate the western limits
of the study area (Figure 3). Thus, scrubs of western
Saint Lucie and Martin counties are not included.


SOILS

Scrub communities of the Treasure Coast are re-
stricted to deep sandy soils created during the Pleisto-
cene and Holocene epochs discussed-above. Through-
out these periods of sea level fluctuation, soils were so
dramatically altered by differential sorting, erosion,
sedimentation, translocation, additions of humic mate-
rials, and other processes that it is frequently impossi-
ble to determine their geologic origins (Davis 1943). As
a result, the study area supports a great number of soil
.types, many of which are of similar origin. Their pres-
ent characteristics are due to the types of materials





















































APPROXIMATE SCALE
1" = 12.6 MILES


JUPITER

JUNO
BEACH




0
PALM
BEACH




BOYNTON
BEACH

DELRAY
BEACH


BOCA
RATON


Figure 3. The coastal scrub study area.






deposited, soil hydrology, and soil maturation under
the influences of climatic conditions and vegetation.
All four counties in the region have been soil-
mapped by the United States Soil Conservation Service
(McCollum et al. 1978, Watts and Stankey 1980,
McCollum and Cruz 1981, Wettstein et al. 1987). The
predominant soils of scrub habitats, as reflected in
these surveys, possess a great many common character-
isticsTIhey are moderately to extremely well-drained,
permeable to very rapidly permeable, deep sands of
marine or aeolian origin. They are slightly to strongly
acidic, are of low natural fertility, and make relatively
poor agricultural landjExcept for Electra soils (South
Florida Flatwoods range site), these soils are in the Sand
Pine Scrub range site. For this report, these soils were
categorized into four groups on the basis of morphol-
ogy, hydrology, and native vegetation' as described
below. Information regarding soil morphology and
hydrology is from the referenced soil surveys.

Excessively Drained Ridge Soils

This group includes Astatula series and Welaka Var-
iant soils. These are nearly level to gently sloping,
excessively drained, very permeable soils of the Atlan-
tic Coastal Ridge in Indian River and Saint Lucie coun-
ties. They are often distinguishable from the primary
and secondary scrub soils in that they may possess a
brownish or blackish surface layer about 4 to 5 inches
thick, in contrast to the gray, white, or yellow surface
sands of other scrub soils. They often support a xeric
hammock, sandhill, or other dry upland community
which is successionally related to, but not representa-
tive of, a scrub community. Depending on location,
slope, exposure, and disturbance history these areas
may support sand pine scrub or scrubby flatwoods.
Astatula sand - Astatula sand is found in Indian River
and Saint Lucie counties, and commonly includes small
areas of Paola, Pomello, and Saint Lucie soils. The
water table is at a depth greater than 6 feet throughout
the year. Native communities include sand pine scrub,
scrubby oak flatwoods, and a variety of other xeric
forested associations.
Welaka Variant sand - This soil is found only in Saint
Lucie County (in the Treasure Coast Region), and
commonly possesses small inclusions of Paola, Pendar-
vis, and Saint Lucie soils. The water table is at a depth
greater than 80 inches throughout the year. Xeric
hammock associations dominate this soil type, but
sand pine scrub and scrubby oak flatwoods occur in
some areas.

Primary Scrub Soils

These include the deep sandy soils which are nor-
mally dominated by scrub communities. Sand pine
scrub is the most common association, but scrubby oak
flatwoods and scubby pine flatwoods also occur


depending on site characteristics, location, and distur-
bance history. Along major river corridors these soils
may support a hammock association with a mixed
forest canopy of oaks, cabbage palm, slash pine, long-
leaf pine, scrub hickory, and other hardwoods; and an
understory of lichens, rosemary, scrub live oak, myrtle
oak, fetterbush, staggerbush, saw palmetto, and other
"scrubby" species.' Hobe, Paola, and Saint Lucie series
soils are included in this group.
Hobe sand and Hobe fine sand - These are somewhat
excessively drained, nearly level to gently sloping soils
of ridges and knolls in flatwoods of Saint Lucie and
Martin counties. Inclusions of Electra, Jonathan, Net-
tles, Pendarvis, Pomello, Salerno, Satellite Variant, and
Saint Lucie soils occur within these map units. The
water table is between 50 and 60 inches deep for brief
periods following heavy rainfall. It is generally between
depths of 60 to 80 inches in wet seasons, and below a
depth of 80 inches during the dry season. Permeability
is rapid in the surface and subsurface layers, and mod-
erate in the subsoil. The forest canopy consists of long-
leaf pine or slash pine in lower areas, and sand pine at
higher elevations. The understory consists of scrub live
oak, running oak, rosemary, saw palmetto, fetterbush,
prickly-pear cactus, and threeawn grasses.
Paola sand - This excessively drained, nearly level to
moderately steep soil of the Atlantic Coastal Ridge and
isolated coastal knolls occurs in all four Treasure Coast
counties. Other soils found within the map units as
minor inclusions include Archbold, Astatula, Hobe,
Jonathan, Orsino, Pomello, Satellite, Satellite Variant,
Saint Lucie, and Welaka Variant. Paola sand is very
highly permeable, and the water table is below 6 feet
deep throughout the year. It occurs in higher land-
scapes and is dominated by sand pine scrub. Scrubby
flatwoods are also common, especially where alteration
by man, erosion, or disturbance of the natural fire
regime has occurred. Other xeric forest associations
may occur on this soil, particularly on elevated ridges
along major river corridors.
Saint Lucie sand - This is an excessively drained, nearly
level to moderately steep sand of the coastal ridge and
flatwoods knolls in all four Treasure Coast counties.
Among the typical inclusions are small areas of Arch-
bold, Astatula, Paola, Pomello, Satellite, Satellite Var-
iant, and Welaka Variant soils. This soil is very rapidly
permeable, and the water table is below a depth of 6 feet
throughout the year. Sand pine scrub dominates most
areas, with scrubby flatwoods occurring on some sites,
and other xeric associations occasionally occupying
elevated ridges along river corridors.

Secondary Scrub Soils

These include moderately well-drained to well-
drained sandy soils occurring along margins and exten-

'Scientific names are presented in Tables 1-5






sions of ridges dominated by primary scrub soils, along
major riverbanks, and as knolls and low ridges within
broad flatwoods. These soils are likely to support sand
pine scrub, scrubby pine flatwoods, or scrubby oak
flatwoods, depending on general location, elevation,
slope, exposure, and disturbance history. Where adja-
cent to larger areas of primary scrub soils, these soils
normally support scrub associations as well, at least in
part. On lower fringes of these ridges, and on lower
ridges or knolls, they are more likely to support
scrubby pine flatwoods which may merge impercepti-
bly with typical pine flatwoods. Along river corridors,
they often support a hammock community; and these
soils may even be dominated by pine flatwoods where
they represent the highest ground within a slough or
lower flatwoods region. This diverse group includes
Archbold, Jonathan, Pomello, Pomello Variant, Orsino,
and Satellite Variant (Martin County only).

Archbold sand - This is a nearly level to sloping, moder-
ately well-drained, very rapidly permeable soil found
on the Atlantic Coastal Ridge and elevated flatwoods
knolls in Indian River County. Small areas of Astatula,
Jonathan, Orsino, Pomello, and Satellite soils are
included in the map units. The water table occurs at
depths of 24 to 40 inches for 1 to 4 months during the
wet season, from 40 to 60 inches for at least 6 months
in most years, and at 80 inches or greater depth during
drought periods. Sand pine scrub, scrubby flatwoods,
sandhills, and xeric hammock associations dominate
these soils.

Jonathan sand - This nearly level to gently sloping, mod-
erately to somewhat excessively drained soil occurs on
the Atlantic Coastal Ridge and slightly elevated flat-
woods knolls in Indian River, Saint Lucie, and Martin
counties. Small areas of Hobe, Immokalee, Pendarvis,
Pomello, Pomello Variant, Salerno, Saint Lucie, Satel-
lite Variant, and Waveland soils are included in the
map units. Permeability is moderately rapid to very
rapid in the surface and subsurface layers, and slow to
very slow in the subsoil. The water table in most years is
between 40 and 60 inches deep for 1 to 4 months in the
wet season, and below 60 inches for the remainder of
the year. Scrubby pine flatwoods is the most character-
istic natural community, but sand pine scrub occurs in
some areas.

Pomello and Pomello Variant sands - These consist of
nearly level to gently sloping, moderately well-drained,
sandy soils that have a weakly cemented layer below a
depth of 30 inches. They occur on margins of major
coastal ridges, and on lower knolls and ridges in the
flatwoods of Indian River, Martin, and Palm Beach
counties. Included in the map units are small areas of
Archbold, Immokalee, Jonathan, Myakka, Orsino,
Satellite, Satellite Variant, and Waveland soils. Per-
meability is very rapid in the surface and subsurface
layers, and moderate to moderately rapid in the subsoil.


Under natural conditions, the water table is at a depth
of 24 to 40 inches during the wet season, and from 40
to 60 inches during the remainder of the year. Sand
pine scrub, scrubby flatwoods, or occasionally sandhill
vegetation occupies Pomello sands of the primary coast-
al ridges and higher flatwoods knolls, with lower flat-
woods ridges and knolls dominated by scrubby flat-
woods or pine flatwoods.

Orsino sand and Orsino fine sand - These are nearly level
to gently sloping, moderately well-drained soils along
the eastern shoreline ridge of Sebastian Creek in Indian
River County, and in transitional areas between ridges
and flatwoods of Martin County. Normal inclusions
are small areas of Electra, Immokalee, Jonathan, Olds-
mar, Paola, Pomello, Saint Lucie, Salerno, Satellite,
Satellite Variant, and Waveland soils. Permeability is
very rapid throughout the profile. The water table is
between 40 and 60 inches for 6 months or more during
normal years, and receeds to depths greater than 60
inches during drought periods. These soils support a
variety of natural communities including sand pine
scrub, xeric hammocks, and scrubby pine flatwoods.

Satellite Variant sand - This nearly level, moderately
well-drained soil occurs on slightly elevated ridges and
knolls in flatwoods of Martin County, and has been
separated from the Satellite sands of Indian River and
Saint Lucie counties because of its relatively xeric
nature, and greater likelihood of supporting scrub
communities. Small areas of Jonathan, Orsino, Pomello,
Salerno, Saint Lucie, and Waveland soils occur as nor-
mal inclusions. It is very rapidly permeable throughout
the profile, with a water table between 40 and 60 inches
for 6 to 9 months of most years. The water table rises to
depths of 30 to 40 inches for up to 60 days during wet
periods, and recedes below depths of 60 inches for 2 to
4 months in drier seasons. Scrubby pine flatwoods is
the most typical community, with pine flatwoods and
sand pine scrub occurring in some areas.

Minor Scrub Soils

This group represents moderately well-drained to
somewhat poorly drained soils found along lower
slopes of primary ridges and riverbanks, and as low
ridges and knolls within broad sloughs or flatwoods.
These soils may support sand pine scrub, but are likely
to support a scrubby pine flatwoods or mixed ham-
mock association with some scrub attributes. Where
they are not immediately adjacent to drier soils and
scrub communities, these soils are usually characterized
by a dry pine flatwoods community, with scrub species
most abundant on slightly elevated knolls or ridges.
This group includes Satellite soils of Indian River and
Saint Lucie counties, and Electra and Pendarvis soils.

Electra sand and Electra fine sand - These are somewhat
poorly drained, nearly level to gently sloping soils





found on low ridges and knolls, and adjacent to natural
drainageways. Small areas of Ankona, Hobe, Immoka-
lee, Jonathan, Nettles, Oldsmar, Pendarvis, Pomello,
and Waveland soils occur as inclusions. Permeability is
rapid to very rapid in the surface and subsurface layers,
and moderate to very slow in the subsoil. The water
table occurs between 25 and 40 inches for up to 4
months in most years, and receeds below 40 inches
during dry periods. Scrubby pine flatwoods occupy
drier areas, often merging imperceptibly with pine flat-
woods. Smaller areas of sand pine scrub or scrubby oak
flatwoods also occur, possibly on inclusions of better-
drained soils.
Pendarvis sand - This is a moderately well-drained,
nearly level to gently sloping soil found on low ridges
and knolls in pine flatwoods of Saint Lucie County.
Small areas of Ankona, Electra, Hobe, Jonathan,
Lawnwood, Satellite, and Waveland soils occur as
inclusions. Permeability is rapid in the surface and
subsurface layers, and moderately slow to slow in the
subsoil. This soil normally has a perched water table at
depths of 24 to 40 inches for 1 to 4 months in the rainy
season, and between 40 and 60 inches for the
remainder of the year. Scrubby pine flatwoods occupy
significant areas of Pendarvis sand, with small tracts of
sand pine scrub on elevated sites, and more extensive
pine flatwoods in broader flat areas.
Satellite sand and Satellite fine sand - These nearly level,
somewhat poorly drained soils occur on margins of the
Atlantic Coastal Ridge scrubs, and on low knolls and
ridges in flatwoods of Indian River and Saint Lucie
counties. Small areas of Archbold, Immokalee,
Myakka, Pomello, Pompano, and Saint Lucie soils are
found as inclusions. Permeability is very rapid through-
out the profile. The water table is normally at a depth of
10 to 40 inches for 2 to 6 months, and may range from
40 to 72 inches for 6 months or more. Sand pine scrub
or scrubby pine flatwoods occur on some relatively
well-drained areas along the Atlantic Coastal Ridge,
with more inland sites predominantly supporting
scrubby pine flatwoods or pine flatwoods communities.
As emphasized above, despite close correlation
between vegetative communities and soil types, several
distinct plant communities may occur within most soil
types (Davis 1943, Richardson 1977, Soil Conserva-
tion Service 1981, Abrahamson et al. 1984). Soil types
and vegetative communities are intimately related, and
each has a significant impact on the other (Davis 1943,
Richardson 1977). Man's ability to dramatically alter
the landscape and natural environment through fire
prevention or use, alteration of natural hydrologic
regimes, and destruction or replacement of entire
vegetative associations can completely alter the land-
scape in a very short time (Richardson 1977). These
disturbances further disguise the soil-vegetation rela-
tionships, since soil development is a long-term con-
tinuing process which reflects geological time, not just
the period of man's intervention.


VEGETATION


Scrubs
Scrub associations were recognized as distinct vegeta-
tion types in early floristic and soil studies of Florida.
According to Mulvania (1931), Vignoles (1823) was
probably the first to describe these communities. Over
the years they have been described under several differ-
ent names including scrub (Ives 1856; Nash 1895;
Austin 1976, 1977), sand pine (Harshberger 1914),
sand pine scrub (Harper 1927, Kurz 1942, Laessle
1942, Davis 1943), scrub forest (Davis 1943, Long
1974), sand pine -scrub oak (Harlow and Jones 1965),
and sand scrub (Craighead 1971). According to Laessle
(1967), Vignoles (1823) was among the first to com-
ment on the general similarity in appearance of scrubs
wherever found, and Mulvania (1931) presented the
first ecological survey of a scrub community.
Mulvania (1931) also distinguished between coastal
scrubs and interior scrubs. He stated that newer
(younger) associations occur along the coast, with the
soil revealing comparatively recent dune formation,
and often possessing intact calcareous shells. Older
scrubs, in contrast, occupy the central portion of the
peninsula, the shell component is completely disinte-
grated, and leaching has resulted in a nearly pure silica
sand with an acid soil reaction. He also stated that
coastal scrub vegetation is less uniform and stable than
that of the interior highlands.
Although scrub associations have been afforded
many community names, previous researchers showed
surprising unanimity in specifying the plants most
characteristic of these habitats. Davis (1943) described
the scrub community as supporting over 45 species of
shrubs and small trees. Long (1984) reported 76 spe-
cies from scrubs, and Austin (1976) reported a total
species number of about 75, if weedy species are
included. More recently Austin et al. (1987) reported
90 species to be either obligates (33 species) or charac-
teristic (57 species) of southeast Florida scrubs. The
percentage of species that occur only in scrubs or suc-
cessionally related xeric habitats is unusually high. The
33 obligate species reported by Austin et al. (1987)
comprise 37 percent of the total species number. For
comparison, only about 10 percent of the plants in
Florida are endemic to the state, and only 9 to 10
percent are endemics in south Florida (Austin 1976;
Long 1974, 1984).
Scrub often occurs as a three-layered association as
described by Abrahamson et al. (1984), including a
canopy, a well-defined shrub layer, and a lower stratum
consisting of low shrubs, lichens, spikemoss, and a
sparse herbaceous flora. The canopy and/or lowest
stratum may be greatly reduced or absent, however,
resulting in a one- or two-layered vegetative commu-
nity. The height and density of scrub shrubs are both
fire- and site-dependent, but can reach 10 or more feet
and 100 percent, respectively (Abrahamson et al.
1984).




































Figure 4. Sand pine scrub. Inclination of the canopy trees is characteristic of many coastal scrubs, and results from prevailing
winds.


Many scrub tracts (i.e., sand pine scrubs) are easily
identified by the presence of sand pines (Figure 4). This
species can be readily distinguished by the short needles
(2-4 in), small cones (2-3 in), and dark green foliage
(Figure 5). Sand pines in south Florida may grow 20 or
more feet in 10 years, with an average height of 29 feet
for 12-year-old trees (Austin 1976). Maximum height
attained is approximately 75 feet (Fowells 1965).
According to Austin (1976), ". . . while trees growing
under different conditions vary considerably, a dia-
meter of nine to 10 inches indicates a tree near 40 to 50
years old." Stand density and canopy height vary
greatly, depending on fire history and site characteris-
tics, with long-unburned stands often having a closed
canopy and height of 35 feet or more.
In a typical Treasure Coast scrub, beneath the can-
opy of sand pine (if present) is a sparse to dense shrub
community dominated by xerophytic oak species (Fig-
ure 6) including scrub live oak, myrtle oak, and Chap-
man's oak. Other shrubby species include rosemary,
saw palmetto, scrub hickory, silkbay, pawpaw, hog
plum, staggerbush, shiny blueberry, scrub mint, par-
tridge pea, prickly-pear cactus, and gopher apple (Table
1). Several vines are frequent, including muscadine,
Calusa grape, greenbrier, and love vine. Herbs are rela-
tively sparse, but they typically include beak rush, yel-
low buttons, blazing star, pinweeds, scrub mint, stipu-


Figure 5. Close-up of sand pine foliage and cones. Note
their length relative to the pen.
licida, blue-eyed grass, goldenasters, frostweed, pala-
foxia, jointweed, wireweeds, and hair sedge. The most
common grasses are threeawns, bluestems, and panic
grasses. Lichens often provide more ground cover than
the herbaceous flora, and sand spikemoss may com-
prise a significant component of this stratum (Fig. 7).
Bare ground may comprise up to 50 percent or more of
the basal area, often occurring in roughly circular areas
3 to 15 feet in diameter as described by Mulvania
(1931).







































Figure 6. Typical growth habit of scrub live oak (upper left); and contrasting foliage and acorns of scrub live oak, myrtle
oak, and Chapman's oak (clockwise from upper right).


Distinctions between various types of scrub com-
munities have been mentioned by several researchers,
with distinguishing characteristics including dominant
species (e.g., sand pine, rosemary) or soil color (i.e.,
"white" sands versus "yellow" sands) (Abrahamson et
al. 1984; Christman and Hardin 1987; Florida Natural
Areas Inventory, unpubl. data). No differentiation of
scrub types occurring in the Treasure Coast Region has
been published. For this reason, and because the nearly
imperceptible merging of various scrub "types" would
have greatly complicated the mapping effort, no further
scrub community differentiation was attempted in this
report.
There is little seasonal change in most scrub associa-
tions, except for spring leaf turnover of the oak under-
story, and winter leaf-fall from scrub hickory where
that deciduous species is present. Abrahamson et al.
(1984) found light levels beneath the tree canopy in
mature scrub to be the lowest of any association they
studied, with the exception of bayheads.


Scrubby Flatwoods

Scrubby flatwoods have not been distinguished as
separate vegetation types by many authors (e.g.,
Harshberger 1914, Harper 1927, Davis 1943), but
rather included with one of the habitats with which
they are transitional (sand pine scrub and pine flat-
woods). Their range is mainly coextensive with that of
scrub (Abrahamson et al. 1984). Laessle (1942) des-
cribed scrubby flatwoods on the Welaka Preserve in
Putnam County; Sweet (1976) described scrubby flat-
woods of Merritt Island; and Richardson (1977),
Richardson et al. (1986), and Austin et al. (1987)
discussed them briefly for Palm Beach County.
Scrubby flatwoods of the southern Lake Wales Ridge
were described by Woolfenden (1969), Westcott
(1970), and Abrahamson et al. (1984). Similar com-
munities have often been designated "oak scrub"
(Breininger 1981, Woolfenden and Fitzpatrick 1984,
Breininger et al. 1986).






Table 1. Plants of coastal scrubs in the Treasure Coast Region.'

Common Name Species Namez Scrub Indicator


Reindeer Moss, Lichen
Reindeer Moss, Lichen
British Soldier, Lichen
Lichen
Sand Spikemoss
Florida Arrowroot; Coontie
Slash Pine
Longleaf Pine
Sand Pine
Cypress Pine*
Florida Bluestem
Corkscrew Threeawn
Wiregrass
Hillsborough Threeawn
Panic Grass
Natalgrass
Hair Sedge
Bulbostylis
Galingale, Sedge
Galingale, Sedge
Beak Rush
Beak Rush
Nut Rush
Scrub Palmetto
Cabbage Palm
Saw Palmetto
Wild Pine
Cardinal Wild Pine
Twisted Air Plant
Wild Pine; Air Plant
Ball-moss
Spanish Moss
Giant Wild Pine
Day-flower
Roseling
Greenbrier; Catbrier
Blue-eyed Grass
Variegated Orchid
False Coco
Nodding-caps
Australian Pine*
Wax Myrtle
Scrub Hickory
Chapman's Oak
Scrub Live Oak
Bluejack Oak
Turkey Oak
Dwarf Live Oak
Myrtle Oak
Running Oak
Virginia Live Oak
Tallowwood; Hog Plum
Wireweed
Sandhill Wireweed


Cladina evansii
Cladina subtenuis
Cladonia leporina
Cladonia prostrata
Selaginella arenicola
Zamia pumila
Pinus elliottii
Pinus palustris
Pinus clausa
Callitris columellaris
Andropogon floridanus
Aristida gyrans
Aristida strict
Aristida tenuispica
Dichanthelium sabulorum
Rhynchelytrum repens
Bulbostylis ciliatifolia
Bulbostylis warei
Cyperus compressus
Cyperus retrorsus
Rhynchospora intermedia
Rhynchospora megalocarpa
Scleria ciliata
Sabal etonia
Sabal palmetto
Serenoa repens
Tillandsia balbisiana
Tillandsia fasciculata
Tillandsia flexuosa
Tillandsia paucifolia
Tillandsia recurvata
Tillandsia usneoides
Tillandsia utriculata
Commelina erecta
Cuthbertia ornata
Smilax auriculata
Sisyrinchium solstitiale
Oncidium bahamensis
Pteroglossappsis ecristata
Triphora gentianoides
Casuarina spp.
Myrica cerifera
Carya floridana
Quercus chapmanii
Quercus geminata
Quercus incana
Quercus laevis
Quercus minima
Quercus myrtifolia
Quercus pumila
Quercus virginiana
Ximenia americana
Polygonella ciliata
Polygonella fimbriata var. robusta





Table 1. Continued.

Common Name Species Name2 Scrub Indicator


Wireweed
Jointweed
Cottonweed
Lace Plant
Stipulicida
Pawpaw
Four-petal Pawpaw
Love Vine
Silkbay
Polanisia
Gopher Apple
Partridge-pea
Blue Peas
Rabbit-bells
Prairie Clover, Summer Farewell
Milk Peas
Milk Peas
Milk Peas
Sky-blue Lupine
Sand-dune Spurge
Tread Softly
Croton
Spurge
Phyllanthus
Queen's Delight
Rosemary
Winged Sumac
Brazilian Pepper*
Inkberry; Gallberry
Southern Fox Grape; Muscadine
Calusa Grape
Saint John's Wort
Frostweed
Frostweed
Nodding Pinweed
Pinweed
Pinweed
Prickly-pear Cactus
Fragrant Eryngium
Tarflower
Dwarf Huckleberry
Staggerbush
Fetterbush
Indian Pipe
Blueberry
Shiny Blueberry
Deerberry
Tough Bumelia
Curtiss Milkweed
Milkweed
Beautybush
Scrub Mint
Lakela's Mint
Pennyroyal


Polygonella gracilis
Polygonella polygama
Froelichia floridana
Paronychia americana
Stipulicida setacea
Asimina reticulata
Asimina tetramera
Cassytha filiformes
Persea humilis
Polanisia tenuifolia
Licania michauxii
Cassia chamaecrista
Clitoria mariana
Crotalaria rotundifolia
Dalea feayi
Galactia elliottii
Galactia regulars
Galactia volubilis
Lupinus diffusus
Chamaesyce cumulicola
Cnidoscolus stimulosus
Croton glandulosus
Euphorbia polyphylla
Phyllanthus abnormis
Stillingia sylvatica
Ceratiola ericoides
Rhus copallina
Schinus terebinthifolius
flex glabra
Vitis munsoniana
Vitis shuttleworthii
Hypericum reductum
Helianthemum corymbosum
Helianthemum nashii
Lechea cernua
Lechea deckertii
Lechea divaricata
Opuntia humifusa
Eryngium aromaticum
Befaria racemosa
Gaylussacia dumosa
Lyonia fruticosa
Lyonia lucida
Monotropa uniflora
Vaccinium darrowii
Vaccinium myrsinites
Vaccinium stamineum
Bumelia tenax
Asclepias curtissii
Asclepias pedicellata
Callicarpa americana
Conradina grandiflora
Dicerandra immaculate
Piloblephis rigida






Table 1. Continued.

Common Name Species Name2 Scrub Indicator

Forked Blue-curls Trichostema dichotomum
Ground Cherries Physalis viscosa
Hedge Hyssop Gratiola hispida
Scrub Toadflax Linaria floridana I
Seymeria Seymeria pectinata I
Poor Joe Diodia teres
Diamond-flowers Hedyotis nigricans
Innocence Hedyotis procumbens
Yellow Buttons Balduina angustifolia I
Deer's Tongue Carphephorus corymbosus
Goldenaster Chrysopsis scabrella I
Camphorweed Heterotheca subaxillaris
Blazing Star Liatris chapmanii I
Blazing Star Liatris tenuifolia
Palafoxia Palafoxia feayi I
Palafoxia Palafoxia integrifolia
Silk Grass Pityopsis graminifolia
Blackroot Pterocaulon virgatum
Goldenrod Solidago chapmanii

'Modified from Austin et al. (1987).
2Taxonomy from Wunderlin (1982) and Long and Lakela (1971).
* Exotic Species


Scrubby flatwoods are scrub-like associations often
occurring on drier ridges in typical flatwoods, or adja-
cent to sand pine scrub. Understory species are similar
to those of sand pine scrub, but the sand pine is
replaced by slash pine or longleaf pine. On some tracts,
pines may be absent. In describing scrubby flatwoods as
a predominantly evergreen, xeromorphic association,
Abrahamson et al. (1984) stated that the average height
of most shrubs is 3 to 6 feet, but varies with site
conditions (moisture and perhaps nutrients) and time
elapsed since the last fire. To distinguish sites which
possess a pine canopy from oak-dominated scrubs
without a significant pine component, two types of
scrubby flatwoods are identified here: scrubby pine flat-
woods (with a pine component) (Figure 8), and scrubby
oak flatwoods (Figure 9).
Floristically, scrubby flatwoods are intermediate
between the oak-understory phase of sand pine scrub
(Abrahamson et al. 1984), and pine flatwoods. At
Archbold Biological Station an endemic oak, Quercus
inopina (Johnson and Abrahamson 1982), is the most
characteristic species of scrubby flatwoods, though
scrub live oak or Chapman's oak may dominate partic-
ular sites (Abrahamson et al. 1984). Other representa-
tive shrub species, also found in less well-drained flat-
woods sites, include fetterbush, tarflower, dwarf
huckleberry, and Saint John's-wort.
Scrubby flatwoods also differ from typical sand pine
scrub associations in that their soils tend to have a


higher water table. Upper levels of scrubby flatwoods
soils, however, tend to get just as drought as those of
the sand pine scrubs (Abrahamson et al. 1984). These
associations differ from typical flatwoods associations
in that they occur on well-drained soils where there is
no standing water even under extremely wet conditions
(Abrahamson et al. 1984).
In the Treasure Coast Region, scrubby flatwoods
may be difficult to delineate because of extreme inter-
gradation with adjacent communities such as sand pine
scrub, sandhills, pine flatwoods, and dry prairie. For
this study, scrubby flatwoods include communities
where the understory consists primarily of species that
are representative of sand pine scrubs. Generally,
abundance of xerophytic oaks and other "scrub"
shrubs, and/or extensive lichen ground cover are
determining factors. Sites dominated by saw palmetto
are not included unless the remaining understory spe-
cies are more representative of scrub than of pine flat-
woods or dry prairies.
Abrahamson et al. (1984) reported that scrubby
flatwoods show slight seasonal change, with flowering
and leafing of the oaks staggered by species: "Each of
these species drops its leaves, flowers, and produces
new leaves within several weeks during March, April,
and May; thus there are never extended periods of
leaflessness, although during particularly drought
springs this association may have a barren, leafless
aspect."




































Figure 7. Lichens and sand spikemoss often dominate the ground cover community of early successional scrubs, but
gradually may be excluded by encroaching shrubs and closure of the canopy.


Pine Flatwoods

Pine flatwoods communities are briefly described to
distinguish them from the scrubby flatwoods discussed
above. They have been described by many researchers
using names including "middling pine" (DeBrahm
1773), "pines" (Ives 1856), "slash pine" (Harshberger
1914), "flatwoods" (Harper 1927), "pine flatwoods"
(Davis 1943, Sweet 1976, Richardson 1977), and
"slash pine - saw palmetto flatwoods" (Breininger et al.
1986). Furthermore, several variations of these flat-
woods have been recognized (Abrahamson et al. 1984).
They range from open savannah-like sites with saw
palmettos, threeawn grasses, and scattered slash pines
or longleaf pines; to dense pine stands with thick shrub
cover (Figure 10). In the Treasure Coast Region, com-
mon species of pine flatwoods include slash pine, saw
palmetto, fetterbush, gallberry, wax myrtle, gopher
apple, running oak, tarflower, pennyroyal, threeawn,
and Coreopsis spp.
Compared to scrubby flatwoods, pine flatwoods
occur on more poorly drained soils which, depending
on rainfall, may vary from very dry to inundated. At
Archbold Biological Station they occur over approxi-
mately the same range of elevation as scrubby flat-
woods, although in the same area they invariably


occupy lower sites (Abrahamson et al. 1984). Davis
(1943, 1967) depicted much of the southeast Florida
coastal flatlands to have been dominated by pine flat-
woods, but cautioned that these areas were actually a
mosaic of pine flatwoods, wet prairies, dry prairies, and
other communities. Richardson (1977) and Steinberg
(1980) reported that pine flatwoods were not extensive
in southeast Florida near the turn of the century, but
have since increased greatly by invading wet or dry
prairies.
In summary, the scrub habitats under consideration
have certain plant species in common, and others (e.g.,
sand pine, slash pine) which may serve to distinguish
them from one another. Also, there are many species
(e.g., oaks, muscadine, saw palmetto) which frequently
occur in scrubs or other plant communities. In their
analyses of scrub, scrubby flatwoods, pine flatwoods,
and several other vegetative associations occurring on
Archbold Biological Station, Abrahamson et al. (1984)
utilized Horn's indices to determine similarities and
differences in these communities (Horn's index is
based on species occurrence and relative abundance;
ranging from 1.0 if all species are common to both
associations and their abundances are equal, to 0.0 if no
species are common to both samples). Using this index,
two clusters of vegetative associations appeared in their




































Figure 8. Scrubby pine flatwoods. Slash pine (pictured) is most common in scrubs of the Treasure Coast Region, but longleaf
pine also occurs.


Figure 9. Scrubby oak flatwoods xericc oak scrub).































































Figure io. Pine flatwoods. Understory and ground cover vary significantly, from an open, savannah-like community
dominated by wiregrass and saw palmetto (top), to a shrubby mosaic of saw palmetto, gallberry, fetterbush, and other shrubs
(bottom).





analysis: (1) those of well-drained sites (scrubs,
scrubby flatwoods, and southern ridge sandhills); and
(2) those of poorly drained sites (flatwoods, swales,
and bayheads). Scrubby flatwoods bridged the gap
between these clusters, reflecting, in part, the transi-
tional topographic position of scrubby flatwoods
between the better-drained scrubs and sandhills and the
more poorly-drained flatwoods, swales, and bayheads
(Abrahamson et al. 1984). The clusters also revealed
striking similarity between the sand pine scrub - oak
understory phase, and the scrubby flatwoods.


WILDLIFE

Early researchers (Harper 1927, Mulvania 1931)
were impressed by the apparent lack of animals in the
scrub. During the last several decades the unique fauna
of the scrub has gradually become appreciated, with
particular emphasis on Endangered, potentially endan-
gered', or endemic species.(/crub animals can be
grouped into several major categories: (1) animals
which are endemic to scrubs and other xeric habitats
(e.g., Florida mouse, Florida scrub jay, Florida scrub
lizard, gopher frog); (2) animals which often are asso-
ciated with scrubs, but which may be found in other
vegetative associations (e.g., rufous-sided towhee,
gopher tortoise, oak toad); (3) ubiquitous or wide-
ranging species which reside in many different habitats
including scrubs (e.g., bobcat, Virginia opossum,
northern cardinal, mourning dove, blue jay, green
anole, six-lined racerunner, southern black racer,
squirrel treefrog, southern toad); (4) animals which are
not characteristic of scrubs, but occasionally occur by
virtue of their mobility or habitat juxtaposition (e.g.,
hispid cotton rat, osprey, box turtle); (5) migratory
birds which seasonally or temporarily occupy scrubs
(e.g., yellow-bellied sapsucker, ruby-crowned kinglet,
yellow-throated warbler, palm warbler); and, (6) spe-
cies which only occur due to disturbances of the natural
community by man such as dumping, land develop-
ment, or introduction of exotic species (e.g., domestic
dogs and cats, black rat, house sparrow, European sta-
rling, brown anole, greenhouse frog). Almost any ter-
restrial species, however, may occasionally utilize
scrubs, depending on habitat juxtaposition or distur-
bances, season, or changing habitat conditions. \
Many of these species rely on the acorns of xeric
oaks, other fruits such as hog plums and muscadine
grapes, or insects for the bulk of their diets (Figure 11).


'The term potentially endangered, as used throughout
this report, includes all plants or animals listed as
Threatened or as Species of Special Concern by the U.S.
Fish and Wildlife Service or the Florida Game and
Fresh Water Fish Commission, and all plants listed as
Threatened or Commercially Exploited by the Florida
Department of Agriculture and Consumer Services.


For example, rosemary fruits are juicy yellow drupes
containing two seeds, often eaten by harvester ants,
mice, rufous-sided towhees, and scrub jays; and acorns
are a primary food of scrub jays and white-tailed deer.
A significant number of scrub species are accomplished
burrowers (e.g., Florida pine snake, gopher tortoise),
or they often cohabit with burrowing animals in scrubs
(e.g., Florida mouse, eastern diamondback rattlesnake,
eastern indigo snake, Florida pine snake, gopher frog).

Mammals

Mammalian scrub inhabitants are, for the most part,
ubiquitous, or species which reside in a variety of
upland shrubby or forested habitats (Rand and Host
1942) (Table 2). Layne et al. (1977) reported 22
mammalian species from sand pine scrub or scrubby
flatwoods of a seven-county area in central Florida,
with five considered common or abundant. Of those,
only the southeastern pocket gopher (Geomys pinetus)
does not occur in the Treasure Coast Region, having
been extirpated from its nearest former range in south-
east Brevard County. Typical carnivores include gray
fox and bobcat, while bats, eastern moles, and least
shrews comprise the most common insectivores. Rela-
tively ubiquitous omnivores include raccoon, Virginia
opossum, striped skunk, and spotted skunk; and char-
acteristic herbivores include white-tailed deer, oldfield
mouse, cotton mouse, eastern cottontail, southern fly-
ing squirrel, and gray squirrel. The only Florida mam-
mal which is endemic to scrubs and other xeric habitats
is the Florida mouse. Larger mammals including the
Florida panther (Felis concolor coryi) and black bear
(Ursus americanus floridanus) may be encountered in
scrubs where these species have not been extirpated
from their historic range.

Birds

The avifauna of Treasure Coast scrubs (Table 3)
includes a modest number of regularly breeding species
such as rufous-sided towhee, chuck-will's-widow,
Carolina wren, northern mockingbird, blue jay, mourn-
ing dove, northern cardinal, and white-eyed vireo.
Many species are occasional nesters, requiring specific
habitat conditions or proximity to other habitats to
render the scrub a suitable nesting site. For example,
great horned owls typically utilize pre-existing nests of
other birds or squirrels; eastern screech-owls, great-
crested flycatchers, and red-bellied woodpeckers
require nesting cavities; and ospreys are likely to nest in
tall sand pine snags adjacent to major rivers (Figure 12).
Some species (e.g., northern bobwhite) prefer early
successional habitats such as recently burned scrubby
flatwoods, while others (e.g., Cooper's hawk) prefer
mature forest sites. A few breeding species (e.g., north-
ern mockingbird, blue jay) often are most conspicuous
in scrubs surrounded by suburban residential or park
settings. Exotics (e.g., European starling, house spar-
























































Figure 1 . Characteristic fruiting shrubs of scrub communities include (clockwise from upper left) scrub live oak, hog plum,
greenbrier, gopher apple, pawpaw, and scrub hickory.





Table 2. Mammals of coastal scrubs in the Treasure Coast Region.'

Characteristic or
Common Name Species Name Common Species

Virginia Opossum Didelphis virginiana X
Least Shrew Cryptotis parva X
Eastern Mole Scalopus aquaticus X
Seminole Bat Lasiurus seminolus X
Yellow Bat Lasiurus intermedius X
Evening Bat Nycticeius humeralis X
Nine-banded Armadillo* Dasypus novemcinctus X
Eastern Cottontail Sylvilagus floridanus X
Gray Squirrel Sciurus carolinensis X
Fox Squirrel Sciurus niger shermani
Southern Flying Squirrel Glaucomys volans X
Oldfield Mouse Peromyscus polionotus X
Cotton Mouse Peromyscus gossypinus X
Florida Mouse Podomys floridanus X
Hispid Cotton Rat Sigmodon hispidus X
Black Rat* Rattus rattus
House Mouse* Mus musculus
Gray Fox Urocyon cinereoargenteus X
Raccoon Procyon lotor X
Long-tailed Weasel Mustela frenata
Eastern Spotted Skunk Spilogale putorius X
Striped Skunk Mephitis mephitis X
Bobcat Felis rufus X
Wild Pig** Sus scrofa
White-tailed Deer Odocoileus virginianus X

'Taxonomy from Brown (1987). Subspecific epithets from Layne (1984).
* Exotic Species
** Feral Species


Reptiles and Amphibians


row) are only abundant as breeding species in severely
disturbed or fragmented scrubs surrounded by urban
or suburban development. Woolfenden (1969)
reported 9 nesting species from his sand pine scrub site,
13 species from mature scrubby pine flatwoods, and 12
species from a recently burned scrubby flatwoods. The
Florida scrub jay, endemic to scrubs and similar xeric
habitats (i.e., coastal strand), is a particularly note-
worthy member of the breeding avifauna.
Nonbreeding birds of the scrub include migratory
transients (e.g., barn swallow, American redstart,
yellow-throated warbler) and a larger component of
wintering species such as American robin, yellow-
bellied sapsucker, ruby-crowned kinglet, solitary vireo,
yellow-rumped warbler, and palm warbler. Layne et al.
(1977) reported 72 avian species from scrubby flat-
woods or sand pine scrub in their seven-county central
Florida study area, including 23 species judged to be
common or abundant.


The herpetofauna (Tables 4 and 5) of sand pine
scrubs has been studied by Campbell and Christman
(1982a,b) who found that sand pine scrub with 22
species, and scrubby oak flatwoods (their "evergreen
oak scrub") with 21 species, supported more species of
amphibians and reptiles than any other Florida com-
munity they studied. For comparison, their data
revealed 17 species for hydric hammock, 10 for xeric
hammock, 7 for slash pine flatwoods, and only 3 for
river swamp. This fauna is comprised of some xeric-
adapted species such as eastern coachwhip, scrub lizard,
and six-lined racerunner; a larger component of gener-
alists or wide-ranging species such as green anole,
southern black racer, eastern coral snake, eastern nar-
rowmouth toad, and southern toad; a few significant
gopher tortoise commensals (e.g., Florida pine snake,
eastern indigo snake, gopher frog); and some aquatic
species which occur in scrubs fortuitously surrounded
by the appropriate aquatic habitats (Campbell and
Christman 1982b).





Table 3. Birds of coastal scrubs in the Treasure Coast Region.1


Common Name


Species Name


Characteristic or
Season2 Common Species


Turkey Vulture
Black Vulture
Osprey
Bald Eagle
Cooper's Hawk
Sharp-shinned Hawk
Red-tailed Hawk
Red-shouldered Hawk
Broad-winged Hawk
Northern Harrier
Merlin
Peregrine Falcon
American Kestrel
Southeastern American Kestrel
Northern Bobwhite
Wild Turkey
Common Ground-Dove
Mourning Dove
Eastern Screech-Owl
Great Horned Owl
Chuck-will's-widow
Whip-poor-will
Common Nighthawk
Northern Flicker
Pileated Woodpecker
Red-bellied Woodpecker
Red-headed Woodpecker
Downy Woodpecker
Hairy Woodpecker
Yellow-bellied Sapsucker
Eastern Wood Pewee
Eastern Phoebe
Great Crested Flycatcher
Barn Swallow
Northern Rough-winged Swallow
Tree Swallow
Florida Scrub Jay
Fish Crow
Blue Jay
Carolina Wren
House Wren
Blue-gray Gnatcatcher
Ruby-crowned Kinglet
Hermit Thrush
American Robin
Gray Catbird
Northern Mockingbird
Brown Thrasher
Cedar Waxwing
Loggerhead Shrike
European Starling*
White-eyed Vireo
Solitary Vireo
Yellow-rumped Warbler
Prairie Warbler


Cathartes aura
Coragyps atratus
Pandion haliaetus
Haliaeetus leucocephalus
Accipiter cooperii
Accipiter striatus
Buteo jamaicensis
Buteo lineatus
Buteo platypterus
Circus cyaneus
Falco columbarius
Falco perigrinus
Falco sparverius
Falco sparverius paulus
Colinus virginianus
Meleagris gallopavo
Columbina passerina
Zenaida macroura
Otus asio
Bubo virginianus
Caprimulgus ridgwayi
Caprimulgus vociferus
Chordeiles minor
Colaptes auratus
Dryocopus pileatus
Melanerpes carolinus
Melanerpes erythrocephalus
Picoides pubescens
Picoides villosus
Sphyrapicus various
Contopus virens
Sayomis phoebe
Myiarchus crinitus
Hirundo rustica
Stelgidopteryx serripennis
Tachycineta bicolor
Aphelocoma coerulescens
Corvus ossifragus
Cyanocitta cristata
Thryothorus ludovicianus
Troglodytes aedon
Polioptila caerulea
Regulus calendula
Catharus guttatus
Turdus migratorius
Dumetella carolinensis
Mimus polyglottos
Toxostoma rufum
Bombycilla cedorum
Lanius ludovicianus
Sturnus vulgaris
Vireo griseus
Vireo solitarius
Dendroica coronata
Dendroica discolor
23




Table 3. Continued.


Characteristic or
Common Name Species Name Season2 Common Species

Yellow-throated Warbler Dendroica dominica W X
Blackburnian Warbler Dendroica fusca T
Palm Warbler Dendroica palmarum W X
Yellow Warbler Dendroica petechia T
Pine Warbler Dendroica pinus R X
Blackpoll Warbler Dendroica striata T
Black-throated Green Warbler Dendroica virens T
Common Yellowthroat Geothlypis trichas R+ X
Black-and-white Warbler Mniotilta varia W X
Northern Parula Parula americana W
Prothonotary Warbler Protonotaria citrea T
Ovenbird Seiurus aurocapillus W X
American Redstart Setophaga ruticilla T
Orange-crowned Warbler Vermivora celata W
House Sparrow* Passer domesticus R
Northern Cardinal Cardinalis cardinalis R+ X
Rufous-sided Towhee Pipilo erythrophthalmus R+ X
Bachman's Sparrow Aimophila aestivlis R
Chipping Sparrow Spizella passerina W
Field Sparrow Spizella pusilla W
American Goldfinch Carduelis tristis W

'Taxonomy from American Ornithologist's Union (1982).
2R = Resident; W = Winter; S = Summer; T = Transitory; + = Breeding
* Exotic Species


Figure 12. An osprey nest in a sand pine snag along the
Saint Lucie River.


The herpetofauna responds to a suite of physical
habitat features including well-drained soil and patches
of loose, dry sand, rather than to a specific vegetative
community (Campbell and Christman 1982b; Christ-
man et al., unpubl. ms.). Four species found in Trea-
sure Coast Region scrubs (i.e., eastern spadefoot, six-
lined racerunner, scrub lizard, and crowned snake) are
more abundant in early successional scrubs; whereas
green anoles, ground skinks, and southeastern five-
lined skinks are more frequent in older scrubs (Camp-
bell and Christman 1982b; Christman et al., unpubl.
ms.). Availability of temporary or permanent breeding
ponds strongly affects occurrence of many amphibian
species (e.g., gopher frog, eastern spadefoot, eastern
narrowmouth toad) which are found in scrub habitats
(Christman et al., unpubl. ms.).
Layne et al. (1977) reported 32 species of reptiles
and amphibians from scrubby habitats in their seven-
county study area, including seven reptiles and three
amphibians considered common or abundant.


ECOLOGY

The ecology of scrub habitats has been debated for
decades, and many aspects of these systems are still
poorly understood. Topics of major emphasis have
included the origin, distribution, succession, fire ecol-






Table 4. Reptiles of coastal scrubs of the Treasure Coast Region.-


Common Name

Florida Worm Lizard
Eastern Slender Glass Lizard
Island Glass Lizard
Eastern Glass Lizard
Green Anole
Brown Anole*
Florida Scrub Lizard
Peninsula Mole Skink
Southeastern Five-lined Skink
Ground Skink
Six-lined Racerunner
Florida Box Turtle
Gopher Tortoise
Florida Scarlet Snake
Southern Black Racer
Southern Ringneck Snake
Eastern Indigo Snake
Corn Snake
Yellow Rat Snake
Eastern Hognose Snake
Southern Hognose Snake
Florida Kingsnake
Scarlet Kingsnake
Eastern Coachwhip
Rough Green Snake
Florida Pine Snake
Pine Woods Snake
Coastal Dunes Crowned Snake
Eastern Garter Snake
Eastern Coral Snake
Eastern Diamondback Rattlesnake
Dusky Pigmy Rattlesnake


Species Name


Rhineura floridana X
Ophisaurus attenuatus longicaudus
Ophisaurus compressus X
Ophisaurus ventralis
Anolis carolinensis X
Anolis sagrei sagrei
Sceloporus woodi X
Eumeces egregius onocrepis X
Eumeces inexpectatus X
Scincella lateralis X
Cnemidophorus sexlineatus sexlineatus X
Terrapene carolina bauri
Gopherus polyphemus X
Cemophora coccinea coccinea X
Coluber constrictor priapus X
Diadophis punctatus punctatus X
Drymarchon corais couperi X
Elaphe guttata guttata
Elaphe obsoleta quadrivittata
Heterodon platyrhinos X
Heterodon simus X
Lampropeltis getulus floridana
Lampropeltis triangulum elapsoides X
Masticophis flagellum flagellum X
Opheodrys aestivus X
Pituophis melanoleucus mugitus X
Rhadinaea flavilata
Tantilla relicta pamlica X
Thamnophis sirtalis sirtalis X
Micrurus fulvius fulvius X
Crotalus adamanteus X
Sistrurus miliarius barbouri X


1Taxonomy from Collins et al. (1982) and Ashton and Ashton (1981, 1985).
* Exotic Species


ogy, and stability of these communities. According to
Webber (1935), the origin of large scrub areas is prob-
ably traceable in part to the poor, arid soils on which
scrub species can succeed better than any other group
of plants. Generally, the modern flora of peninsular
Florida is thought to have evolved about 5,000 years
ago, with scrubs being a modified relic of historically
extensive sclerophyllous oak forest and scrub associa-
tions (Watts 1971, 1980; Austin 1976; Abrahamson et
al. 1984; Long 1984). Webber (1935) postulated that:

". . . in the early formative period of plant
distribution in this part of Florida the scrub
oaks, because of their mode of spreading by
sprouts from the roots and their adaptability to
succeed in such arid soils, found in these areas


an opportunity to dominate the other vegeta-
tion and finally to extend their territory as natu-
ral conditions permitted."

Mulvania (1931) noted the occurrence of bare sandy
areas within scrubs, and explained their origin as
follows:

"Many of the scrub plants grow in clumps, as is
the case with Ceratiola ericoides and Xolisma
[Lyonia] ferruginea, and the clumps become of
considerable size. Now, if one of these commu-
nal groups should for any reason die, the space
covered would quickly become bare, and the
size of the group would determine the size of the
denuded spot. Oxidation takes place rapidly in


Characteristic or
Common Species






Table 5. Amphibians of coastal scrubs of the Treasure Coast Region.1

Characteristic or
Common Name Species Name Common Species

Eastern Spadefoot Scaphiopus holbrookii X
Giant Toad* Bufo marinus
Oak Toad Bufo quercicus X
Southern Toad Bufo terrestris X
Green Treefrog Hyla cinerea
Pine-woods Treefrog Hyla femoralis X
Barking Treefrog Hyla gratiosa X
Squirrel Treefrog Hyla squirella X
Cuban Treefrog* Osteopilus septentrionalis
Gopher Frog Rana areolata aesopus X
Eastern Narrowmouth Toad Gastrophryne carolinensis X
Greenhouse Frog* Eleutherodactylus planirostris planirostris X

'Taxonomy from Collins et al. (1982).
* Exotic Species


the porous sand. The dry organic matter is also
easily blown from the bare areas."

Barren areas may also result from killing of seeds, roots,
and rhizomes in localized "hot-spots" during scrub
wildfires or prescribed burns (Ron Myers, pers.
comm.), or from human disturbance of the scrub
community.

Distribution

The distribution of scrub communities has been sub-
ject to particularly intense debate, with primary
emphasis being the scrubs' radical demarcation from
sandhills which are the other dominant community of
deep, well-drained sands in peninsular Florida. Scrub
distribution has been attributed to lower available nu-
trients in scrub soils (Harper 1927; Kurz 1942; Laessle
1942, 1958), soil and water relations (Harper 1927,
Mulvania 1931, Kurz 1942, Richardson 1977, Abra-
hamson et al. 1984, Austin et al. 1987), chance (Whit-
ney 1898), mutual antagonism between the communi-
ties (Nash 1895), salt tolerance coupled with site
specific winds and topography (Laessle 1967), allelo-
pathy (Richardson 1985), and fire (Webber 1935;
Laessle 1958, 1967; Richardson 1977; Abrahamson et
al. 1984; Austin et al. 1987).
Soil differences relating to nutrients, moisture gra-
dients, and topography have been intensively studied as
they relate to the distribution of scrub habitats. Davis
(1943) discussed the importance of these factors in
determining habitat distribution in south Florida, and
Abrahamson et al. (1984) noted soil-vegetation rela-
tionships between sand pine scrubs, scrubby flatwoods,
and pine flatwoods on the Archbold Biological Station.
As stated by Richardson (1977), ". . . soils and topo-
graphy closely correlate to the vegetation in southern


Florida. Very slight changes in soil moisture, slope or
elevation can cause major shifts from one plant associa-
tion to another."
Researchers, however, differed on the nature of the
relationships between soil characteristics and scrub dis-
tribution. Harper (1927), Kurz (1942), and Laessle
(1942, 1958) attributed much of the noted habitat
delineation to soil chemistry, but Whitney (1898),
Webber (1935), Laessle (1967), and Abrahamson et
al. (1984) determined that there were no consistent
differences in soil chemistry which would account for
scrub distribution, as compared to other upland habi-
tats.
Mulvania (1931) placed particular emphasis on
availability of water in determining the nature of vege-
tation. He believed that distribution of sandhill and
scrub communities was attributable to soil type, with
water holding capacity of the sand being the dominant
factor:

"That water is one of the chief controlling fac-
tors in determining the character of the scrub
association is attested by the semixeric nature of
the entire population. Each species shows some
structural provision for the conservative use of
water. Pinus clausa has fine, short leaves and
close set scales on the younger twigs. Ceratiola
ericoides has short needle-like, bristly leaves, and
dense, dry, brittle wood. Xolisma [Lyonia] ferru-
ginea has thickly cutinized, densely tomotose
tomentosee], strongly revolute leaves, etc. The
stomata are often obscured and small on some
of the plants, and the leaves are greatly thick-
ened and seldom exposed horizontally."

Abrahamson et al. (1984) presented supporting evi-
dence for this argument in noting that many dominant





scrub species show convergent, xeromorphic adapta-
tions including small, sclerophyllous, revolute or linear
leaves; and that leaves of many scrub species (e.g., scrub
live oak, staggerbush, tough buckthorn, silkbay) have
pubescent undersides. Furthermore, they documented
the importance of soil moisture gradients as determi-
nant factors in the distribution of pine flatwoods,
scrubby flatwoods, and sand pine communities, stating
that the rosemary-phase sand pine scrub is associated
with the driest sites, while flatwoods soils were moister
than those of the scrubby flatwoods or sand pine
scrubs. The water table of scrubby flatwoods soils is
much shallower than that of sand pine scrubs, even
though the upper layers of both soils are subject to
drought conditions (Abrahamson et al. 1984).

Fire

South Florida has the highest frequency of lightning
strikes in the United States, with the peak number
occurring during the summer rainy season (Abraham-
son 1984a). Naturally occurring fires in south Florida
are virtually all associated with lightning strikes (Abra-
hamson 1984a, Hofstetter 1984). Abrahamson (1981,
cited by Abrahamson et al. 1984) reported that 84
percent of the recorded lightning strikes, and 97 per-
cent of the recorded lightning-caused fires in Highlands
County between 1967 and 1980 occurred between
May and September, with a peak of activity in July.
Nonetheless, a very low percentage of lightning strikes
result in fire, with only 30 out of the estimated 2,100 to
2,600 strikes known to have caused fires during those
14 years.
The importance of fire in maintaining south Florida
natural communities, including scrubs, has been recog-
nized for decades. Many researchers have noted that
scrubs burn infrequently, but once ignited, they burn
intensely (Nash 1895, Harper 1927, Webber 1935,
Davis 1943, Laessle 1967, Abrahamson et al. 1984).
Nash (1985) first noted the vulnerability of these habi-
tats to fire, and Webber (1935) and Laessle (1967)
both referred to sand pine scrub as a "fire-fighting
machine." This seeming contradiction is easily resolved.
Nash was referring to the individual scrub species' lack
of fire resistant bark or other protective features, while
Webber and Laessle were discussing scrub habitat
resistance to ground fires, in contrast to the sandhill
community. Webber explained his statement as follows:

"Nearly all scrub plants are evergreen and drop
old leaves throughout the year. Scrub bushes
and trees so fully occupy the soil that they
absorb available moisture and nutrition to the
extent that the flammable grasses and other
herbs are excluded. The soil surface is thus rela-
tively bare of flammable material except for
gradually falling leaves and old twigs which
rapidly rot and disappear. Furthermore, a natu-
ral fire break is maintained between the scrub


and adjacent sandhill vegetation as the extensive
root system of both communities probably
limit the growth of flammable grasses and herbs
between those communities."


Webber (1935), Laessle (1967), and Abrahamson et
al. (1984) all reported that fire frequently approaches
the scrub and dies without gaining entrance. After a
number of uninterrupted fire-free years, however, the
scrub accumulates dead limbs and branches, and the
firebreak margin becomes partially covered with grass.
Under these conditions, a fire may ignite the scrub.
Laessle (1967) stated that crown fires in the scrub
readily could be started in relatively dense stands of
sand pine through ignition of dense epiphytic growths
of Spanish moss [ball moss?] via lightning. He further
stated that Spanish moss could be an important factor
in allowing creeping ground fires to gain access to the
tops of sand pines and thus become crown fires. He
stated that multiple-aged stands of sand pine probably
thus developed after ground fires had partially opened
scrubs by killing back part of the shrubby understory
and canopy.
The frequency of fire under natural conditions in
scrub habitats has been debated. Harper (1927) indi-
cated that about one fire every 70 years was correct for
sand pine scrub. Abrahamson et al. (1984) felt that the
fire interval was probably greater than 30 years, and
Abrahamson (1984a) estimated a modal fire frequency
of 30 to 70 years. Austin (1976) suggested that a 20 to
40 year cycle is the norm. He reasoned that fires at less
than a 20-year cycle either damage the stand of pines
severely or kill them, the species needing 5 to 10 years
to mature and start producing seeds. Fires at longer
than optimal intervals would often become crown fires,
which may kill large expanses of pines. He stated that
this may cause a burst of growth by the palmettos and
oaks, due to the increased nutrients and opened space,
resulting in overshadowing and crowding out many or
all pine seedlings that may be present.
Whether or not fire is necessary for regeneration of
sand pine also has been somewhat controversial. Not-
ing the lack of pine regeneration within the sand pine
scrub - oak understory phase, Abrahamson et al.
(1984) suspected that sand pines require fire to release
large seed crops from the semiserotinous cones, and for
germination and seedling establishment. They also
reported a pronounced but variable lag of several years
in germination of sand pine following fire. Austin
(1976) stated that the idea that fire is essential for sand
pine seed dispersal is possibly attributable to Harper,
but disputed this "partial-truth," citing examples from
past fires in Jonathan Dickinson State Park. He con-
cluded that: "Fire is not absolutely necessary for seed
dispersal. It certainly aids the process in some cases, but
not in all." Many Treasure Coast sand pine scrubs
exhibit limited sand pine reproduction without fire.
Consequently, uneven-aged stands are fairly common.






The following summary of the fire ecology of sand
pine scrub was presented in the Florida Environmentally
Endangered Lands Plan (Florida Department of Natural
Resources 1975:104):
"The sand pine scrub is essentially a fire-based
community. . . . Ground cover is extremely
sparse and leaf fall is minimal, thus reducing the
chance of the frequent ground fires so impor-
tant in the sandhill community. As the sand
pines mature, however, they retain most of their
branches, thereby building up large fuel sup-
plies in the crowns. The thick understory vege-
tation and these retained branches provide
ready pathways to the highly combustible
crown. When a fire does occur (every twenty to
forty years) this fuel supply, in combination
with the sand pine's relatively low resistance to
fire and the high stand density, assure a hot, fast
burning fire. . . . Such fires allow for regenera-
tion of the sand pine community, which would
otherwise pass into a xeric hammock. This type
of fire regeneration usually results in even aged
stands of trees."
In a demographic study of rosemary scrubs, Johnson
(1982) found that rosemary scrubs often show a pat-
tern of older cohorts in the center and younger cohorts
on the edges where fires in adjacent scrubby flatwoods
have reached into the associations and died out. She
determined that even-aged rosemary stands result from
strong seed germination responses following severe
fire, and concluded that this species appears to be
adapted to a fire frequency of once every 10 to 40 years
(Johnson 1982:173):

"If fires occurred more frequently than every 10
years, there would be no seed store in the soil to
replace the shrubs killed. Seed productivity
peaks at 20 to 30 years and then declines. If fire
occurred at intervals longer than 4C years, there
would be selective pressure in favor of plants
which continued to produce large seed crops
past 40 years."

In their studies of Lake Wales Ridge vegetation,
Abrahamson et al. (1984:240-241) described the fire
ecology of scrubby flatwoods on Archbold Biological
Station as follows:

"In the sprouter-dominated scrubby flatwoods,
there is also a distinct lack of easily burned
vegetation due to low standing crop biomass
and patches of bare sand. When fire does occur
(with temperatures ranging from 66-482�C, it
can kill above ground vegetation, although it
usually passes through scrubby flatwoods in a
spotty manner leaving a mosaic of lightly to
intensely burned and unburned areas. However,
burn coverage and intensity in scrubby flat-


woods is appreciably increased with the pres-
ence of strong winds. Such fires do little to alter
the vegetation pattern, because the shrubs read-
ily sprout from their rhizomes (e.g., Quercus
spp.), or root crowns (e.g., Persia, Garberia),
restoring the community to its preburn compo-
sition (Abrahamson 1984a)."

Referring to the Archbold grounds, Abrahamson et
al. (1984) found that fire produces a complex pattern
of unburned and lightly to severely burned areas as it
travels through the mosaic of vegetative associations.
The associations vary considerably in flammability,
which appears related to the amount of grass, palmetto,
pine duff, and litter available. They ranked the associa-
tions under consideration here in the following order of
flammability from highest to lowest: flatwoods -
scrubby flatwoods - scrub.
Abrahamson (1984a,b) explained that associations
dominated by species that are killed by fire and regen-
erate by seeding (e.g., sand pine scrub and rosemary
scrub) burn less frequently than associations whose
dominants regenerate following fire by sprouting or
survive fire by resisting (e.g., flatwoods, scrubby flat-
woods). Keely and Zedler (1978) suggested that greater
availability of germination sites due to thinning during
longer cycles may favor the seederss." Acknowledging
that open rosemary stands present more germination
sites after fire than do the denser scrubby oak stands,
however, Johnson (1982) felt that success of seeders
was more attributable to initial site differences (water,
nutrients) preventing the oaks from establishing a
denser cover, than solely to thinning of the rosemary
seedlings. Johnson et al. (1986) suggested that scrubby
oaks (sprouters) and rosemary seederr) occupy the
same niche in their respective sites, and queried the
ability of species with such different responses to fire to
dominate adjacent sites.
In comparing the species or genetic turnover result-
ing from fire in seeding and sprouting associations,
Abrahamson (1984a,b) and Abrahamson et al. (1984)
explained that in seeding associations there is a major
turnover of individual genotypes as the dominants
(sand pine and/or rosemary) are killed by fire, but the
community is not invaded by a set of pioneer species
which later give way to an association similar to that
killed by fire. Thus, fire results primarily in a genetic
turnover, not a species turnover. Contrastingly,
although the above ground biomass of sprouting asso-
ciations can be removed by fire, it begins to regenerate
within days except under drought conditions, restoring
the community to near its preburn condition within 4
years. The post fire association is thus composed of
virtually the same genotypes as the preburn association.

Natural Succession

Successional relationships between scrubs and other
native communities are poorly understood. Most





research on scrub succession has concentrated on the
seral relationship between sand pine scrub and sandhill
communities. Harper (1921, 1927) thought that there
would be no successional change with fire once in a
lifetime. Webber (1935) thought that frequent fire
would destroy the scrub, to be succeeded by turkey oak
and bluejack oak; but, scrub would rarely succeed the
sandhill community. Kurz (1942) stated that the sand-
hill community could be succeeded by scrub after suffi-
cient leaching of the sands had occurred. Miller (1950)
thought that sand pine scrub was succeeded by high
pine - turkey oak (sandhill). Laessle first (1942, 1958)
felt that these two communities had no seral relation-
ship. Later (1967) he noted rapid spread of sand pine
into unburned sandhill communities; and felt that,
given time, scrubby oaks may also occupy the former
sandhill community, effecting a fairly complete habitat
transformation. Similar invasion of sandhills by sand
pine, scrub hickory, or evergreen oaks was noted by
Veno (1976), Abrahamson et al. (1984), Givens et al.
(1984), Myers (1985), and Peroni and Abrahamson
(1986) on sites protected from fire for several decades.
Givens et al. (1984), however, detected no convergence
of the two communities over a 10-year period. Veno
(1976) reported an increase in similarity between tur-
key oak sandhills and sand pine scrub over 21 years,
but felt that they were both succeeding toward a xeric
hammock community. Many researchers have felt that
fire plays a dominant role in the seral relationship
between sand pine scrub and sandhill communities
(Laessle 1958, 1967; Veno 1976; Myers 1985). Myers
(1985) further stated that disruption of the fire regime
could potentially result in displacement of either com-
munity by the other.
Austin (1976) stated that the normal succession
from a beach community to scrub involved the follow-
ing sequence: (1) beach pioneer stage; (2) scrub pine
(sand pine) dominance stage; (3) shrub stage with oaks,
rosemary, and palmettos (this stage appearing only
when fires are so frequent or hot that the pines and
seedlings are killed); and (4) hammocks dominated by
oaks, palms, hickory, and other temperate trees.
Richardson (1977) constructed a diagram of poten-
tial successional relationships between the communi-
ties native to Palm Beach County. He felt that, histori-
cally, scrub developed primarily from the beach
community; but could succeed, often via human inter-
vention, into scrubby flatwoods, low xericc) hammock,
strand, or palmetto - oak scrub. Scrubby flatwoods
could either precede or succeed dry prairie or pine
flatwoods communities. Many pine flatwoods in the
Treasure Coast Region are becoming more scrubby,
possibly due to excessive drainage and less frequent
fires. Richardson (1977) documented a shift in com-
munity structure from scrub to scrubby flatwoods: due
to increased fires and accelerated erosion, the sand
pines were being eliminated and were being replaced by
slash pines. A similar shift from sand pine scrub to
scrubby pine flatwoods was reported by Steinberg


(1980), Peroni and Abrahamson (1986), and Austin et
al. (1987), and has been indicated on many tracts
throughout the region during this study.
Because sand pine scrub is a fire-maintained associa-
tion, exclusion of fire from scrubs results in succes-
sional change. Citing several examples, Laessle (1967)
offered several possible outcomes from long-term
exclusion of fire: (1) sand pines could be eliminated
through death of the old trees and lack of regeneration,
while the overgrown understory resembles a hammock
comprised of typical scrub flora; (2) the scrub could
"run out," or reach a senescent condition where sand
pine and a few other scrub species persist indefinitely in
a depauperate association; or (3) succession toward a
coastal hammock community, with laurel oak (Quercus
laurifolia), red bay (Persea borbonia), southern magnolia
(Magnolia grandiflora), and other hammock species
invading the scrub community. The most widely-
supported scenario entails succession of scrub to a xeric
hammock association if fire is precluded for an exces-
sive period, though gradual invasion by mesic species
could facilitate succession to a mesic hammock (Kurz
1942; Laessle 1958, 1967; Monk 1968; Austin 1976;
Veno 1976; Richardson 1977; Steinberg 1980; Myers
1985). Soil fertility and moisture, proximity to seed
sources of potentially invading species, and isolation
from fire-prone communities such as sandhills, flat-
woods, and dry prairies are significant factors in deter-
mining the succeeding community on a given site (Laes-
sle 1958, 1967; Veno 1976; Richardson 1977;
Abrahamson et al. 1984; Myers 1985).
A number of researchers have considered scrub
associations to be extremely stable under natural condi-
tions. Harper (1927) thought that there would be little
change in the scrub community with fire occurring
about every 70 years. Mulvania (1931) addressed the
difficulty of seedling establishment in scrub sands,
relating this factor to stability and persistence of barren
sandy areas within scrub habitats. Allelopathic effects
of lichens and rosemary may partially explain the per-
sistence of "early successional" patches of scrub vege-
tation within maturing communities (Don Richardson,
pers. comm.). Webber (1935) felt that, "the present
limits of the large scrub areas became established cen-
turies ago and that a state of near equilibrium has
existed for many years." Kurz (1942) felt that many
scrubs represent an extremely stable edaphic climax
community. Laessle (1967) concurred with Webber
(1935), noting that lightning-caused fires should be
considered a natural part of scrub ecology, and adding
that he felt some scrubs had existed unchanged for
millions of years. Veno (1976), in a 21-year study of
community succession, considered sand pine scrub to
be a "pulsating steady state" which is adapted to main-
tain itself under a natural fire regime. In this scenario,
fire occurs at regular intervals, and the likelihood of fire
increases with time elapsed since the previous fire. In a
study of successional changes over a 10-year interval,
Givens et al. (1984) reported that changes were primar-





ily structural, with thinning of herb and shrub layers
and an increase in tree height and canopy coverage.
Analysis using Horn's index of community similarity
showed little change in species composition or relative
abundances. They acknowledged, however, that 10
years may be too short a period to realize measurable
succession. They determined that long-term succes-
sional changes in scrub associations are extremely slow,
with these natural communities being essentially stable.
Abrahamson (1984a) also was impressed by the stabil-
ity of scrub communities as evidenced by the brief
duration of fire disturbance, lack of post-fire invasion
by non-scrub species, and the resiliency of individual
scrub species. He stated that this stability is "the conse-
quence of an evolutionary history of these species
which involves natural selection by winter droughts,
acidic, nutrient-poor, sand substrates, and repeated
burning."


Human Impacts

Just as environmental forces discussed above affect
native vegetative associations, human activities pro-
foundly impact natural communities, including scrubs.
Davis (1943) discussed impacts of lowering the water
table on natural communities in south Florida. More
recently, Austin (1977), Richardson (1977), Steinberg
(1980), Abrahahamson et al. (1984), and Richardson
et al. (1986) noted vegetation changes in wet prairies,
dry prairies, pine flatwoods, scrubby flatwoods, and
scrubs which they attributed to drainage practices, ero-
sion, and other human-related disturbances.
Myers and Peroni (1983) felt that intentional, exten-
sive use of fire in altering natural vegetation may date
back at least 12,000 years. Abrahamson et al.
(1984:242) presented the following discussion of
modern man's impact on the natural fire regime in the
southern Lake Wales Ridge area, an analysis which is
equally applicable to the Treasure Coast Region:

"During the past half century, the effect has
been that of both direct and indirect fire sup-
pression. During the 1930s, intensive efforts
were made to extinguish all wildfires, regardless
of location or source. At the same time, devel-
opment activities resulted in establishment of
agricultural areas, roads, and housing com-
plexes which functioned as unintentional, albeit
effective, fire breaks. More recent cultural fea-
tures such as power lines and towers may even
alter lightning behavior, hence changing the
incidence of natural fires. In addition, fence
laws enacted in the early 1950s abolished the
open range and eventually put an end to the
widespread, uncontrolled burning which accom-
panied it. The overall result is the present situa-
tion where, although fires may be ignited more
frequently than during the period prior to the


mid 1930s, the total area burned on noncom-
mercial land over a given period of time
decreases."

Dependence of scrubs upon fire for community
maintenance is the crux of this issue. Because most
scrubs are at least partially developed, or are sur-
rounded by developed lands, suppression of wildfire is
the norm. The resulting overgrowth (Figure 13) leads
to decline of herbaceous species diversity and abun-
dance, and reduction in the percentage of bare ground.
These habitat characteristics are particularly important
to preservation of Florida scrub jays, scrub lizards,
gopher tortoises, and other scrub species. Overgrowth
may also predispose the tract to disastrous wildfire, due
to the tremendous fuel buildup.
In addition to fire and drainage manipulation, several
other human impacts can be significant. Richardson
(1977) emphasized that growth and use of technology
enable man to rapidly modify the environment in any
fashion, a capability which has resulted in massive dete-
rioration of the natural vegetation on the Atlantic
Coastal Ridge.
Activities which disturb the soil, such as bulldozing
of roads and firelanes, or land clearing in speculation of
future development, tend to permanently alter the
landscape. Off-road vehicles have criss-crossed many
scrubs with trails; undeveloped tracts are often utilized
as impromptu campsites or recreational areas; and ille-
gal dumping of excess or waste construction materials,
abandoned cars and appliances, or household garbage is
widespread (Figure 14). Resulting elimination of
sprouting species through destruction of root and
underground stem systems, and changes in water and
light patterns accompanying such activities, may facili-
tate invasion by non-native vegetation. Most exotic or
weedy plants found in scrubs occur along roads, fire-
lanes, in drainage ditches, and in other disturbed areas
created by man (Austin 1977, Abrahamson et al.
1984). Roads, firelanes, and drainage ditches may also
maintain populations of forbs that are characteristic of
periodically burned areas and which would otherwise
be eliminated by canopy closure (Abrahamson et al.
1984).
Similarly, humans are responsible for introduction
of black rats, domestic dogs and cats, greenhouse frogs,
giant toads, Cuban treefrogs, brown anoles, and a host
of other exotic animal species into native south Florida
ecosystems. Although most exotics simply occupy dis-
turbed sites which no longer provide suitable habitat
for native species, some actively prey upon, or compete
with, the native fauna (Wilson and Porras 1983).



































Figure 13. Overgrown scrubby flatwoods (background). Although scrub jays and gopher tortoises still occupy this tract, the
vegetation is too tall and dense to provide optimal habitat.




















- .. paw


Figure 14. In addition to land development, human-related disturbances to scrub communities include (clockwise from
upper left) establishment of campsites and makeshift recreational facilities, grazing, unauthorized dumping, off-road
vehicle use, and land clearing to "enhance" property salability.













SECTION 2.


ENDANGERED, POTENTIALLY ENDANGERED,
OR ENDEMIC SPECIES






Scrubs and scrubby flatwoods provide habitat for a
number of species which are listed by the Florida Game
and Fresh Water Fish Commission (FGFWFC), U.S.
Fish and Wildlife Service (USFWS), or Florida Com-
mittee on Rare and Endangered Plants and Animals
(FCREPA) as Endangered (E), Threatened (T), or Species
of Special Concern (SSC). Others are currently under
review (UR) for listing. In addition, the Florida
Department of Agriculture and Consumer Services
(FDACS) lists many scrub plant species as Endangered,
Threatened, or Commercially Exploited. Florida popula-
tions of these species are considered at significant risk
in the wild because of habitat destruction, persecution
or overcollection by man, or other factors. Listed spe-
cies which are often associated with scrubs are dis-
cussed below. The following general species descrip-
tions and biology are largely excerpted from Rare and
Endangered Biota of Florida (Pritchard 1978 - 1982), or
synthesized from other published works (Conant 1975;
Burt and Grossenheider 1976; Auffenberg and Iverson
1979; Behler and King 1979; Whitaker and Elman
1980; Ashton and Ashton 1981, 1985; Breininger
1981; Auffenberg and Franz 1982; Cox 1984, 1987;
Woolfenden and Fitzpatrick 1984; Breininger et al.
1986; Enge et al. 1986; Cox et al. 1987).

VERTEBRATES

Florida Mouse (Podomys floridanus) SSC/UR/T
(FGFWFC/USFWS/FCREPA)

The Florida mouse (Figure 15) generally resembles
mice of the genus Peromyscus, from which this species is
now distinguished (Jones et al. 1986, Brown 1987). It
has big, dark eyes and large, sparsely-haired ears. The
pelage is relatively long and soft. The upperparts of the
adult are brownish to brownish-gray shading to bright
orange-buff on the shoulders and lower sides. The
underparts are white, frequently with a tawny patch on
the breast. The tail is dusky above and light below, but
not sharply bicolored. Juveniles are clear gray above
and whitish below. Unlike Peromyscus, the Florida
mouse has five instead of six well-developed plantar
tubercles on the hind foot. It is about 7 to 8 inches in
total length, with a tail 3 to 3.5 inches long, and a hind
foot length of 0.9 inches. Adult weights range from
about 0.9 to 1.7 ounces.
The Florida mouse is the only species of mammal
entirely restricted to the state of Florida. Except for an
apparently isolated population along the Gulf coast in
Franklin County, the species is further confined to the
peninsula. It has one of the narrowest habitat ranges of
any Florida mammal, and thus is distributed in a
patchwork of relatively isolated populations that
reflect the distribution of those habitats. Early succes-
sional scrubs and scrubby flatwoods are the preferred
habitats, but the species also occurs in sandhill com-
munities. Richardson et al. (1986) reported that Flor-


ida mice evidently inhabit scrubs throughout the long
burning cycle, with early successional stands (the first
40 years) providing the best habitat conditions.
Optimal habitat characteristics include relatively xeric
conditions; an open tree stand; clumps of scrubby oaks
and other shrubs with scattered patches of bare ground;
and well-drained, sandy soils.
Florida mice are strongly nocturnal (Layne 1971a)
ground dwellers (Layne 1970, Klein and Layne 1978).
They typically nest in burrows of other animals (Layne
and Ehrhart 1970), favoring those of the gopher tor-
toise (Eisenberg 1983). Their diet consists of seeds,
nuts, fungi, and other plant materials, as well as insects
and other small invertebrates. Acorns are an important
food item. Breeding occurs mainly in the fall and early
winter, and litter size ranges from one to six, averaging
three or four. Predators of Florida mice include snakes,
birds of prey, and mammalian carnivores such as foxes,
bobcats, and raccoons. Not only is the Florida mouse
an endemic Species of Special Concern, but it also hosts a
species-specific endemic flea, Polygenis floridanus (Layne
1963, 1971b).
Florida mice are primarily threatened by widespread
habitat destruction. Habitat preservation and manage-
ment, and protection of gopher tortoise populations,
are keys to preserving this species.


. ^.L - - . .
.- "



Figure 15. The Florida mouse is the only full species of
mammal which is endemic to Florida.

Florida Scrub Jay (Aphelocoma coerulescens
coerulescens) T/T/T

The Florida scrub jay is a 12-inch-long, crestless jay
(Figure 16) which lacks the white-tipped wing and tail
feathers of the more common and widespread blue jay.
A necklace of blue feathers separates the whiter throat
from the gray underparts, and a white line over the eye
often blends into a whitish forehead. The tail is long
and loose in appearance, and the back is gray. Conspe-
cific jays range over much of the western United States
and Mexico, but the morphologically and behaviorally
unique Florida scrub jay is restricted to scattered, often




small and isolated patches of sand pine scrub, scrubby
flatwoods, and coastal strand in peninsular Florida.
Florida scrub jays have extremely specific habitat
requirements, and avoid wet habitats and forests,
including canopied sand pine stands. Cox (1984) des-
cribed optimal scrub jay habitat as follows: "1) oaks
1-3 m [3-10 feet] tall covering 50-75% of the area; 2)
open space (bare ground or vegetation less than 15 cm
[6 inches] tall) covering 10-30% of the area; and 3)
scattered trees, with no more than 20% canopy cover."
In such areas, scrub jay densities may be well over 1
bird per 2.5 acres, possibly reaching 1 bird per acre
(Breininger 1981). According to Cox (1984), habitats
with these features are usually in disturbed areas, where
construction of roads or buildings has created open
space next to dense thickets of 6- to 10-foot-tall oaks.
In undisturbed areas, it is unusual to find so much open
space where the oaks are of such height. Cox (1984)
stated that in undisturbed habitat, scrub jay densities
would seldom exceed 1 bird per 2.5 acres, even if the
tract were specifically managed for this species, and that
a density of about 1 bird per 5 acres is probably the
greatest that could be maintained on tracts managed for
scrub community preservation.
Florida scrub jays feed on a wide variety of terrestrial
invertebrates, and a few small vertebrates including
frogs, toads, lizards, small snakes, and even rodents.
Insects, especially orthopterans and lepidopteran lar-
vae, comprise a major food source during spring and
summer. In fall and winter, acorns are their primary
food. Other plant foods such as saw palmetto berries,
greenbrier berries, and tread-softly fruits are eaten but
seem to be relatively unimportant. Introduced foods
such as peanuts, cracked corn, and bread are readily
taken.
Florida scrub jays are extremely sedentary, they are
permanently monogamous, and they defend a perma-
nent territory (Woolfenden 1973; Woolfenden and
Fitzpatrick 1984, 1986). Territory size in suitable
scrubby oak flatwoods varies from about 3 to 52 acres,
with an average size of about 23 acres (Woolfendeihand
Fitzpatrick 1984). Their breeding seasorris short com-
pared with other Florida perching birds; nests with eggs
or young occur from early March to mid-June. Scrub
jays raise only one brood per year, but in case of nest
failures, they may lay three, rarely four clutches a sea-
son (Woolfenden 1973). Clutch size varies from 2 to 5
eggs, averaging 3.4 (Woolfenden 1973). Nest failure is
almost always due to predation (Woolfenden and Fitz-
patrick 1986). Breeding rarely occurs before 2 years of
age, and often not until the birds are 3 or 4 years old.
Nonbreeding individuals (especially males) remain in
their natal territory for up to 6 years (Woolfenden and
Fitzpatrick 1984). A well-defined dominance hierarchy
exists within these extended family groups (Wool-
fenden and Fitzpatrick 1977).
Cooperative breeding (Woolfenden and Fitzpatrick
1984) is the most significant and intriguing aspect of
scrub jay ecology. This dominant facet of their behav-


ior, however, has been widely recognized only in the
last 20 years. Most early researchers (e.g., Amadon
1944, Sprunt 1946) noted the possibility of "helpers,"
but attributed little importance to this behavior. In fact,
according to Woolfenden (1975), only one published
account of scrub jays having helpers existed prior to
1969 (i.e., Grimes 1940).


Figure i6. Florida scrub jays are endemic to scrub and
scrubby coastal strand communities of the Florida
peninsula.


Figure 17. Florida scrub jays are wary of humans where
they are harassed or persecuted, but otherwise are an
eminently tamable and "friendly" species.

Long-term demographic studies have since estab-
lished that helpers do indeed contribute to the nesting
effort: breeding pairs with helpers successfully raise
more young than do lone pairs (Woolfenden 1975,
Woolfenden and Fitzpatrick 1984). Helping behavior
is exhibited in a particular suite of activities. Helpers
participate in territory and nest defense, mobbing of
predators, and in certain phases of care for the young
(i.e., feeding nestlings and fledglings, and removing
fecal sacs) (Woolfenden 1975, 1978; Stallcup and
Woolfenden 1978; Woolfenden and Fitzpatrick 1984).
They do not, however, assist in nest building, incubat-
ing, or brooding activities (Woolfenden 1975, Wool-
fenden and Fitzpatrick 1984). There are also significant





sexual asymmetries in the behavior of both breeders
and helpers (Stallcup and Woolfenden 1978, Wool-
fenden and Fitzpatrick 1986).
Three features of the Florida scrub jay stand out as
unique, or nearly so: its extremely narrow habitat toler-
ances, its social system that includes cooperation in
breeding, and its tameness where not persecuted (Fig-
ure 17). These features make the Florida scrub jay an
ideal candidate for ecological and behavioral studies,
and an outstanding example for conservation. Where
protected from persecution, they are easily observed in
their native habitat by the public.
The original range of the jay, estimated at 7,000
square miles, has been reduced considerably by subur-
ban development and conversion of scrub habitats to
agricultural uses. Many isolated populations have been
eliminated, and the historically almost continuous
population along the Atlantic coast has been radically
fragmented by urban development. The species' seden-
tary nature may make natural repopulation of unoccu-
pied scrub areas unlikely, although reproductive suc-
cess of, and dispersal from, small isolated scrub jay
populations are poorly understood. Preservation of
existing populations is of paramount importance, as is
habitat management within designated sanctuaries.
Habitat management for scrub jays essentially con-
sists of periodically burning scrub tracts to maintain the
desired shrub height, canopy closure, and percentage of
bare ground. For optimal scrub jay management, Cox
(1984) recommended burning approximately 10 per-
cent of the total habitat area each year or two, in blocks
of a few hectares each (1 hectare equals approximately
2.5 acres). Obviously, this would entail extensive man-
agement activity and expense, and would not be practi-
cal on most preserves. Where the burning interval is
appreciably longer and firebreaks are necessary, as
would be the case with most preserves, Cox (1984)
recommended dividing the scrub jay habitat into
blocks of 25 to 50 acres each, thereby facilitating pre-
scribed burning and preserving intact territories in each
management unit. Cox (1984) inferred that optimal
fire frequency for scrub jay management would be once
every 5 to 15 years. Mechanical site renovation may
also prove satisfactory for scrub jay habitat manage-
ment where prescribed burning is inadvisable (Breinin-
ger 1981, Cox 1984, Breininger et al. 1986).


Gopher Tortoise (Gopherus polyphemus)
SSC/UR/T

The gopher tortoise (Figure 18) is a medium-sized
turtle, distinguishable from all other Florida species by
its flattened forelimbs, its lack of webbed feet, its dis-
tinct submaxillary gular glands, and its unhinged shell.
The back feet are stubby and elephantine with incon-
spicuous toes, and the tail is remarkably short. The
wide, muscular head is covered with scales. The upper
shell (carapace) ranges from light tan to dark gray, and


may possess light centers in each plate, particularly in
the young. The lower shell (plastron) may be clear
yellow, marbled with black or gray, or even totally
black in some populations (McDiarmid 1978, Landers
et al. 1982). Growth rings are evident on smaller tur-
tles, but the shells of old tortoises are often very
smooth and difficult to age. Adults average about 9 to
11 inches long, and weigh 8 to 10 pounds (Cox et al.
1987). There is significant geographical variation in
gopher tortoise growth rates, adult size, and coloration
throughout the species' range (Landers et al. 1982).
Sexual dimorphism is often evident though not infal-
lible. Mature females generally have greater shell dimen-
sions and longer anal notches, while males have more
concave plastrons, longer gular projections, thicker
anal shields, and greater anal width (McRae et al.
1981a, Cox et al. 1987).


Figure i8. Gopher tortoises have been called "wildlife
landlords" because of the many commensal species which
occupy their burrows.


Gopher tortoises are confined to the Southeastern
Coastal Plain of the United States, ranging from eastern
Louisiana to southeastern South Carolina and through-
out Florida. They occur in all 67 Florida counties,
though some areas, including the Treasure Coast
Region, support only disjunct populations (Auffen-
berg and Franz 1982, Cox et al. 1987).
Cox et al. (1987) identified three factors which char-
acterize suitable adult tortoise habitat: (1) well-drained,
sandy soils; (2) abundance of herbaceous ground
cover; and, (3) open canopy and sparse shrub cover.
Major xeric habitats utilized are coastal strand, sand
pine scrub, sandhills, scrubby flatwoods, and live oak
hammock, as well as old-field successional stages lead-
ing to any of these. Recently, Breininger et al. (1986)
reported that pine flatwoods also support large popula-
tions of tortoises. Though often associated with xeric
habitats, gopher tortoises are subject to desiccation and
temperature stress. Their ability to inhabit xeric habi-
tats and endure high seasonal temperatures appears to
be more related to behavioral patterns and burrow use





than to distinct physiological adaptations (Bogert and
Cowles 1947, Douglass and Layne 1978, Breininger et
al. 1986, Cox et al. 1987).
Gopher tortoises are essentially diurnal (Douglass
and Layne 1978, McRae et al. 1981 b), and feed prima-
rily on grasses and legumes. However, fallen leaves of
several tree species (especially pines and oaks) and
herbs are eaten, as are wild fruits and berries. Occasion-
ally, the diet may include insects or carrion. Grazing by
these tortoises is extremely habitual, with the result
that paths and small clearings are maintained by con-
stant cropping in an otherwise developed herbaceous
layer (Figure 19).


1987). Due to the late age of reproductive maturity,
small clutch size, single annual nesting, and high mortal-
ity of eggs and young, gopher tortoises are very slow to
reproduce. Landers et al. (1980) estimated that the
effective rate of reproduction is about 5.8 hatchlings
per mature female per 10 years. Adults have few natural
enemies, although feral dogs are potentially significant
predators (Causey and Cude 1978).


Figure I9. Gopher tortoises often develop well-worn
trails along their daily foraging routes.


Gopher tortoises exhibit a dominance hierarchy
among mature males (McRae et al. 1981b), and well-
defined courtship behavior including head-bobbing,
posturing, and biting (Auffenberg 1966, Cox et al.
1987). Courtship behavior by males has been observed
from March through October, but breeding is normally
restricted to spring, with nest construction peaking
during May or June (Iverson 1980, Landers et al. 1980,
Diemer 1986). Reported clutch sizes range from 1-15
eggs, averaging about six eggs (Iverson 1980, Landers et
al. 1980, Diemer 1986, Cox et al. 1987). They are laid
about 9 to 10 inches deep in the sand, in sunny areas
often near or in the sand mound at the burrow mouth.
The eggs hatch in about 80 to 90 days in north Florida
(Iverson 1980). The eggs and hatchlings are very sus-
ceptible to predation, with gray foxes, raccoons, striped
skunks, nine-banded armadillos, and Virginia opos-
sums being the most frequent predators (Douglass and
Winegarner 1977, Landers et al. 1980). Alford (1980)
reported 94.2 percent loss of eggs and young by 1 year
of age. Hatchlings are yellow-orange, and about 1.5 to
2.0 inches long when they emerge from their shells
(Cox et al. 1987). Growth averages about 0.4 to 0.8
inches per year before reaching maturity at 10-20 years
of age (Landers et al. 1982, Diemer 1986, Cox et al.


Figure 20. Active gopher tortoise burrows (top) typically
possess clean entrances and may reveal tortoise tracks,
while entrances to inactive burrows (bottom) bear no
tracks and are littered with debris.


Perhaps the most significant characteristic of this
species is that it excavates a long burrow which is used
by the tortoise and a host of other organisms for protec-
tion from enemies and unfavorable climatic conditions.
Burrows typically average about 15 feet long and 6 feet
deep, with maximum reported length and depth of 47.5
feet and 9.2 feet, respectively (Hansen 1963). Burrow
depth is determined largely by soil moisture, and its
conformation by obstacles encountered. The tunnel
typically descends at an average angle of about 30
degrees, but may vary from 15 to 45 degrees of descent
(Speake 1981). The burrow entrance is shaped like a
"half-moon" (Figure 20), and the burrow width is
generally correlated with the length of the tortoise





(Alford 1980). Normally there is one entrance, but two
entrances have been reported (Dietlein and Franz
1979) for a single burrow. Burrows which bifurcate
below the entrance, and burrows with side chambers,
also have been reported (Hansen 1963, Breininger et al.
1986). Individual tortoises normally construct more
than one burrow, and may occupy several burrows
during the course of a year, possibly selecting moister
or even flooded burrows during the dry winter months
(McRae et al. 1981b, Means 1982, Breininger et al.
1986, Cox et al. 1987).
At least 81 species of vertebrates (42) and inverte-
brates (39) are known to utilize gopher tortoise bur-
rows (Franz 1986a, Woodruff 1982, Cox et al. 1987).
Thirty-two vertebrate species (Table 6) found in Trea-
sure Coast scrubs have been identified as gopher tor-


toise commensals (Franz 1986a, Cox et al. 1987). The
Florida mouse, eastern indigo snake, Florida pine
snake, and gopher frog (Figure 21) are commensals
which have been listed as Threatened species (eastern
indigo snake) or Species of Special Concern by the Flor-
ida Game and Fresh Water Fish Commission (Wood
1987). Other vertebrates such as the spotted skunk
(Brian Toland, pers. comm.) and scrub lizard have been
observed using tortoise burrows, though their status as
commensals has not been fully determined. Common
invertebrate commensals include spiders, flies, moths,
beetles, and crickets (Milstrey 1986, Woodruff 1982,
Cox et al. 1987). This invertebrate fauna includes many
obligate commensals that have never been found out-
side of active burrows, and may include undescribed
species as well (Milstrey 1986, Woodruff 1982). Tor-


Table 6. Gopher tortoise commensal vertebrates which occur in coastal scrubs of the Treasure Coast
Region.'

Frequent or
Common Name Species Name Obligate Commensal


Virginia Opossum
Eastern Cottontail
Oldfield Mouse
Cotton Mouse
Florida Mouse
Hispid Cotton Rat
House Mouse*
Gray Fox
Raccoon
Striped Skunk
Northern Bobwhite
Carolina Wren
Green Anole
Southeastern Five-lined Skink
Ground Skink
Six-lined Racerunner
Box Turtle
Gopher Tortoise
Scarlet Snake
Eastern Indigo Snake
Eastern Hognose Snake
Coachwhip
Pine Snake
Garter Snake
Coral Snake
Eastern Diamondback Rattlesnake
Pigmy Rattlesnake
Eastern Spadefoot
Southern Toad
Gopher Frog
Eastern Narrowmouth Toad
Greenhouse Frog*


Didelphis virginiana
Sylvilagus floridanus
Peromyscus polionotus
Peromyscus gossypinus
Podomys floridanus
Sigmodon hispidus
Mus musculus
Urocyon cinereoargenteus
Procyon lotor
Mephitis mephitis
Colinus virginianus
Thryothorus ludovicianus
Anolis carolinensis
Eumeces inexpectatus
Scincella lateralis
Cnemidophorus sexlineatus
Terrapene carolina
Gopherus polyphemus
Cemophora coccinea
Drymarchon corais couperi
Heterodon platyrhinos
Masticophis flagellum
Pituophis melanoleucus
Thamnophis sirtalis
Micrurus fulvius
Crotalus adamanteus
Sistrurus miliarius
Scaphiopus holbrookii
Bufo terrestris
Rana areolata
Gastrophryne carolinensis
Eleutherodactylus planirostris planirostris


'Modified from Cox et al. (1987)
* Exotic Species





















Figure 21. The gopher frog, a Species of Special Figure 22. Scrub lizards, although not currently listed as
Concern, is among the more than 40 vertebrate species a potentially endangered species, are endemic to scrub
which occur as commensals in gopher tortoise burrows. habitats, and are under review for listing as Threatened
by the U.S. Fish and Wildlife Service.


toise dung provides a major food source for many of
these invertebrates (Milstrey 1986, Woodruff 1982),
which in turn comprise a significant food resource for
other commensals such as the Florida mouse and
gopher frog (Milstrey 1986, Cox et al. 1987).
Extensive land development and urbanization have
been cited as the greatest threats to gopher tortoise
populations in Florida (Cox et al. 1987). Other signifi-
cant threats include conversion of native habitats to
agriculture, mining, forest management practices, and
human predation (Taylor 1981, 1982; Auffenberg and
Franz 1982; Diemer 1984a, 1986). Auffenberg and
Franz (1982) predicted that tortoises will be extirpated
from 24 Florida counties, including Palm Beach
County, by the year 2000. They further predicted that,
except for populations on protected lands, gopher tor-
toises will be extirpated from the state by the year 2025.
In a comprehensive review of the ecology and habitat
protection needs of gopher tortoises in Florida, Cox et
al. (1987) determined that establishment and manage-
ment of habitat preserves could contribute to the long-
term protection needs of this species. In scrubs, main-
tenance of early successional stages which support a
relatively high percentage of herbaceous ground cover
is important to preservation of gopher tortoise popula-
tions. Roadsides, firebreaks, and other small clearings
may significantly increase the habitat value of more
mature scrubs for this species.




Scrub Lizard (Sceloporus woodi) NL/UR/Rare

This is a rough, spiny-scaled reptile (Figure 22)
which is generally pale brown or gray-brown, resem-
bling the fence lizard (Sceloporus undulatus) except for
its conspicuous dark lateral band from the neck to the
base of the tail. Males have a long blue area on each side


of the belly, bordered by black on the proximal side,
and a pair of blue spots at the base of the throat. The
rest of the throat is black except for a median white
stripe. The female has dark spots on the chest and
undersurface of the head, with traces of blue on the
throat and sides of an otherwise white venter. They
range from 3.5 to 5.3 inches in length.
Scrub lizards are endemic to Florida, occurring dis-
continuously in sand pine scrub and associated xeric
communities from Marion and Putnam counties south-
ward to Highlands County in the interior, and south-
ward to Collier and Dade counties on the coasts (Jack-
son 1973a). Essential habitat characteristics include
dry, well-drained, deep sandy soils with numerous
patches of open, unvegetated sand and high insolation
levels. There are, however, large tracts of seemingly
suitable habitat which are devoid of scrub lizards for no
obvious reasons. Jackson (1973a) suggested that poor
dispersal abilities may have prevented such areas from
ever being initially occupied, and that local population
extirpations are also likely. Where they do occur, den-
sities may exceed 12 lizards per acre (Jackson and Tel-
ford 1974); thus, relatively small tracts would be
required to maintain viable populations (Enge et al.
1986).
Scrub lizards are primarily ground dwelling, diurnal,
sit-and-wait predators. This has been described as a
behavioral adaptation which optimizes feeding effi-
ciency in the early successional scrubs preferred by this
species (Jackson 1973b). Ants, adult beetles, and
orthopterans comprise the bulk of their diet (Jackson
1973b).
The scrub lizard is characterized as an early maturing,
multiple-brooded, small-clutch species (Jackson and
Telford 1974). In other words, yearlings are sexually
mature, several clutches are normally produced each
year, and there are only 2-8 (averaging 4) eggs per
clutch. Mating occurs from March to September, with
egg deposition from early April to October. Incubation




































Figure 23. The eastern indigo snake, a Threatened
species, is a frequent commensal in gopher tortoise
burrows.

reportedly ranges from about 1 month (Jackson and
Telford 1974) to 75 days (Ashton and Ashton 1985,
Enge et al. 1986).
Scrub lizards are sporadically distributed throughout
the Treasure Coast Region (Jackson 1973a, Enge et al.
1986, this study). Exclusion of fire from scrub habitats,
competition or predatory pressure from naturalized or
introduced species (e.g., nine-banded armadillo, giant
toad, domestic cats and dogs), and their inability to
cross inhospitable areas to colonize suitable habitat are
probably primary factors in their distribution. To
maintain the requisite habitat conditions, periodic
major disturbances of the canopy and ground cover
vegetation are essential for preservation of scrub lizard
populations (Enge et al. 1986, Richardson et al. 1986).
Pesticide use could adversely impact scrub lizards
because of their reliance on arthropods as prey.

Eastern Indigo Snake (Drymarchon corais couperi)
T/T/SSC

The eastern indigo snake (Figure 23) is a large, heavy-
bodied serpent with smooth, shiny scales. Adults are
uniformly black or bluish-black above and below with
the chin, throat, and lips usually tinged with reddish or
orange pigmentation. Hatchlings are often marked with


light speckling on a darker ground color. The average
adult length of indigo snakes is approximately 5 to 6
feet, but individuals over 8 feet long have been
recorded.
The species is widely distributed throughout the
American tropics, with seven races ranging from south-
ern Texas to northern Argentina. This subspecies is
restricted to the southeastern United States, and is
completely isolated from the Texas race. It is wide-
spread, though not necessarily common, in Florida
(Moler 1985), and also inhabits much of southern
Georgia (Diemer and Speake 1981, 1983). Additional
populations may also occur in South Carolina and
southern Alabama.
Although the eastern indigo snake often inhabits dry,
sandy areas, it is actually characteristic of moister habi-
tats and is frequently encountered in pine flatwoods
and moist tropical hammocks. They are susceptible to
desiccation (Bogert and Cowles 1947), and in drier
environments indigo snakes often seek shelter in
gopher tortoise burrows. This behavioral trait, how-
ever, is more common in Alabama and Georgia than in
peninsular Florida, where pine snakes and other snake
species are more common burrow commensals than
indigo snakes (Campbell and Christman 1982b).
Indigo snakes are diurnal predators which feed on
small mammals, birds, frogs, lizards, and other snakes.
They capture their prey with their powerful jaws. Five
to 12 eggs are laid in May or June, usually hatching in
August or September. Little is known of the nesting
habits of indigo snakes.
Habitat destruction and specimen collection are
primarily responsible for the decline of indigo snake
populations. Indigo snakes are particularly docile,
rendering them popular in the pet industry, although
they are now legally protected from such exploitation.
Pouring gasoline into gopher tortoise burrows to drive
out commensal reptiles is known to be lethal to indigo
snakes. Home ranges of indigo snakes average about
400-600 acres in area (Paul Moler, pers. comm.), so
protection of viable populations solely on small, insu-
lar preserves is not feasible. Preservation and manage-
ment of the diverse habitats utilized by indigo snakes,
and protection of viable gopher tortoise populations,
are the most important management alternatives for the
species, apart from strict enforcement of the ban on
collecting.

Florida Pine Snake (Pituophis melanoleucus
mugitus) SSC/NL/NL

This is a large, stocky snake which is highly variable
in color and reaches a maximum length of about 90
inches (Figure 24). The background color is usually
ashy gray, the back being saddled with dark tan to
reddish blotches. In some individuals the blotches may
be nearly black, or absent. The underside is uniformly
smoky gray. This species has keeled scales, and a large
triangular scale which covers the snout.





















Figure 24. The Florida pine snake is an accomplished
burrower, and spends much of its time underground.



Pine snakes range throughout much of the United
States, southwestern Canada, and Mexico. The Florida
subspecies is restricted to Florida and southern Ala-
bama, Georgia, and South Carolina. They occur pri-
marily in sandhills, scrubs, and other sandy habitats,
including disturbed or agricultural areas. They are
accomplished burrowers, and may spend up to 85 per-
cent of their time underground (Franz 1986b). In
peninsular Florida, they are frequent commensals of
gopher tortoises. Franz (1986b) determined the min-
imum home ranges of three pine snakes monitored for
6 to 10 months to average over 130 acres.
Pine snakes are primarily diurnal, and constrict their
prey which consists of small mammals, birds, and
lizards. Little is known of their reproductive habits,
though they apparently lay about 4 to 8 eggs in pocket
gopher burrows or beneath large rocks or logs. Habitat
destruction is cited as the primary reason for their
apparent decline (Ashton and Ashton 1981). Other
significant threats may include decline of gopher tor-
toise populations (with a resultant decrease in burrow
availability), and pouring of gasoline into tortoise bur-
rows to drive out commensal reptiles.


Gopher Frog (Rana areolata aesopus) SSC/UR/T

This is a rather stubby frog with a short, plump body
(2.75 to 3.75 inches), a large head, and relatively short
legs (Figure 25). The males have lateral vocal pouches
which are enormous when inflated, approaching the
size of the frog's head. The coloration varies from
creamy white to brown. Irregular markings on the
smooth or slightly warty dorsum are black or dark
brown and not encircled by light borders. The chin and
throat are spotted and often the males have yellow on
the dorsolateral ridges, on the warts, along the upper
jaw, and in the armpits and groin. The tympanum is not
quite as large as the eye.


Figure 25. Gopher frogs are occasionally found in mouse
burrows, stump holes, and inactive gopher tortoise
burrows, but prefer to inhabit active tortoise burrows.


This species includes the gopher frogs and crawfish
frogs found in the coastal plain from North Carolina to
Florida, along the Gulf coast to eastern Louisiana, and
in drainage systems of the Arkansas, Missouri, Missis-
sippi, and Ohio rivers. The Florida subspecies is found
in sandhill and sand pine scrub habitats of Florida and
southern Georgia. Although they prefer active gopher
tortoise burrows, they will occupy inactive burrows as
well (Eisenberg 1983, Franz 1986b). They have also
been found in oldfield mouse burrows, stump holes,
post holes, and in the mouths of crawfish holes. Occa-
sionally, several gopher frogs have been recorded at a
single burrow (Eisenberg 1983). Gopher frogs are
generally nocturnal, but occasionally will venture from
the burrow on damp, dark days. Their diet consists
mainly of insects, but they readily prey on toads.
During the bimodal breeding season, which peaks in
late winter and early spring, with a subsequent breeding
period in September and October (Eisenberg 1983,
Franz 1986b), gopher frogs travel relatively great dis-
tances and congregate in shallow grassy ponds. Their
chorus is a very deep and distinctive snoring sound.
Gopher frogs transform at a snout-vent length of about
1.12 inches and grow slowly, requiring over 3.5 years
to reach maximum size in central Florida (Franz
1986b).
Habitat destruction is the primary threat to this spe-
cies, though there is evidence that exploitation as a
human food source may also be significant. The prac-
tice of pouring gasoline into tortoise burrows to drive
out rattlesnakes during snake hunts is lethal to gopher
frogs. Because they are gopher tortoise commensals,
protection of gopher tortoise populations is a primary
management objective for the gopher frog. They
require temporary grassy ponds for breeding, so this
habitat requirement must also be satisfied, though they
will cross golf courses and other unsuitable areas to
reach breeding ponds, and then disperse to more
appropriate upland habitats (Paul Moler, pers. comm.).





Franz (1986b) suggested that gopher frogs remain in
tortoise burrows adjacent to breeding ponds for an
extended period during their annual migrations, so it is
essential that tortoise populations be maintained adja-
cent to breeding areas. Pesticide use may detract from
the suitability of golf course roughs, "green spaces,"
and other recreational preserves. Extermination of the
frogs' food supply would render a tract uninhabitable
even if adequate gopher tortoise burrows and breeding
ponds were available.


Figure 26. The red widow spider is an endemic scrub
invertebrate.


INVERTEBRATES

Of the four invertebrate species currently listed by
Florida or Federal agencies (1 coral, 1 butterfly, and 2
snails) (Wood 1987), none occur in the Treasure Coast
Region. Over 70 species are currently under review for
listing, however, and at least four of these are likely to
occur in Treasure Coast scrubs (Franz 1982). All four
of these species are scarab beetles: Aphodius troglodytes,
Copris gopheri, Serica tantula, and Trigonopelastes flori-
dana (Franz 1982). Many other invertebrate species are
endemic to scrub habitats, including the red widow
spider (Lactrodectus bishop) (Figure 26) and the afore-
mentioned flea which is a Florida mouse commensal
(Austin 1976, Franz 1982). A systematic inventory of
the invertebrate fauna of Treasure Coast scrubs is
warranted.


PLANTS

Four plant species listed as Endangered by the U.S.
Fish and Wildlife Service may occur in study area
scrubs (Figure 27). Lakela's mint occurs on small, pri-
vately owned scrubs in southern Indian River and
northern Saint Lucie counties. The fragrant prickly
apple (Cereus eriophorus var. fragrans) occurs in scrubby
xeric hammocks of Saint Lucie and Martin counties,
including the Savannahs State Preserve. The four-petal
pawpaw occurs in Palm Beach, Martin, and southern
Saint Lucie counties. Carter's mustard (Warea carter)
was historically reported from Brevard County south
to Dade County (Channel and James 1964, Wunderlin
1982), and a confirmed specimen has recently been
reported from Brevard County (Margaret Haines, pers.
comm.). There are, however, no recent confirmed
sightings of this species in the Treasure Coast Region.
In addition to those discussed above, many plant
species are listed as Endangered (E), Threatened (T), or
Commercially Exploited (C) by the Florida Department
of Agriculture and Consumer Services (Figure 28). A
number of these species occur in scrubby habitats of
the Treasure Coast Region (Ward 1982, Wunderlin
1982, Austin et al. 1987), including Curtiss milkweed
(T), scrub palmetto (T), sand spikemoss (T), prickly-
pear cactus (T), and Florida arrowroot (C). Several of
these species are epiphytes, including cardinal wild pine
(C), giant wild pine (C), twisted air plant (T), Tillandsia
balbisiana (T), and T. pauciflora (T). Three orchids are
also among these listed species: false coco (T), varie-
gated orchid (E), and nodding-caps (T).
Data regarding distribution and abundance of
Endangered or potentially endangered plants are availa-
ble through university herbaria, the Florida Natural
Areas Inventory, and various federal, state, and
regional agencies. As a security precaution against
overcollecting, such information was not included in
this report. Readers with particular interest in these
species should consult the appropriate sources cited
above.
Although species lists for many scrub sites in the
study area have been compiled (Austin 1977, Richard-
son 1977, Popenoe 1981, Boss et al. 1984, Ecological
Consultants and Quantum Associates 1986, Richard-
son et al. 1986, Austin et al. 1987, plus many unpub-
lished lists), no comprehensive inventory of scrub
Endangered, potentially endangered, or endemic plants
has been conducted for the Treasure Coast Region. A
floristic study concentrating on endemic species is cur-
rently in progress for scrub communities of the Lake
Wales Ridge (Christman et al. 1986, Christman and
Hardin 1987), and a similar effort is warranted for the
Treasure Coast Region.





























































Figure 27. Federally Endangered plant species of scrub
communities include Lakela's mint (top), and four-petal
pawpaw (bottom; with three-, four-, and five-parted
flowers).







'I

II


Figure 28. Threatened (T) or Commercially Exploited (C) plants of Treasure Coast scrubs include (clockwise from
upper left) Curtiss milkweed (T), prickly-pear cactus (T), sand spikemoss (T), scrub palmetto (T), giant wild pine (C), and
nodding pinweed (under review for possible listing by the U.S. Fish and Wildlife Service).















SECTION 3.


REGULATORY PROGRAMS AFFECTING

SCRUB COMMUNITIES








Federal and state development restrictions are often
perceived as costly and burdensome intrusions on local
government authority and private property rights. By
the same token, local government is often viewed as
ineffective in dealing with natural resources of state or
federal significance. Therefore, it is appropriate to
briefly review the regulatory processes which affect
scrub preservation or destruction in the Treasure Coast
Region.


FEDERAL AUTHORITY

There are several federal regulatory programs of par-
ticular application to upland development issues or
protection of native wildlife. The National Envi-
ronmental Policy Act is administered by the U.S. Envi-
ronmental Protection Agency. This legislation is
intended to ensure that federally assisted or imple-
mented programs would not unnecessarily impact the
environment. All federal agencies and actions are sub-
ject to the Act. Enforcement is primarily exercised
through review of Environmental Impact Statements,
which must be prepared for any federally sponsored,
funded, or implemented action which could signifi-
cantly impact the environment. Project review, how-
ever, emphasizes impacts upon the "human" environ-
ment. Thus, project impacts upon native fish and
wildlife communities often are of secondary considera-
tion. Also, the Act does not apply to projects which do
not involve federal action or funding.
The Endangered Species Act of 1973 as amended is
of potential importance to the protection of many
scrub species, and is currently applicable to Florida
scrub jays, eastern indigo snakes, and the federally
listed plant species discussed above. The U.S. Fish and
Wildlife Service regularly updates a list of species
which are considered Endangered or Threatened. The
Act recognizes the need for habitat protection, and
provides for designation of critical habitat and for
acquisition of such lands. Listed animal species are
protected from killing or other harassment by the Act.
Plant species, however, are not protected from destruc-
tion by the landowner. This shortcoming, and the Act's
lack of generally applicable habitat protection measures
greatly reduce its effectiveness.
Several articles of federal legislation protect migra-
tory birds, including the Migratory Bird Treaty Act,
and the Migratory Bird Conservation Act.


STATE AUTHORITY

At the state level, there are several regulatory pro-
grams which address the protection of upland habitats


or species. Other than coastal dunes and beaches, how-
ever, there are no upland habitats which receive state-
wide, statutory protection. There are five major com-
ponents of Florida law which directly impact develop-
ment activities in scrubs.
The Florida Environmental Land and Water Manage-
ment Act of 1972 provides for designation of Areas of
Critical State Concern for areas "containing or having a
significant impact upon environmental, historical or
archaeological resources of regional or statewide
importance. ";Such designation has never been applied
to an area of tipland scrub habitats. This Act, however,
also requires review of Development of Regional Impact
(DRI) proposals by the appropriate regional planning
council, and provides for oversight of these functions
by the Department of Community Affairs. The Develop-
ment of Regional Impact review process is discussed
later as a regional regulatory function.
Under the State Comprehensive Plan and Growth
Management Act, regional and local governments are
required to prepare Comprehensive Growth Manage-
ment Plans for their respective areas of jurisdiction, and
all regional or local policies and ordinances must
comply with these plans. These comprehensive plans
must provide for protection of natural resources,
including vegetation and wildlife communities; and
must provide for planned and orderly development of
the region, county, or municipality. As with the Land
and Water Management Act, review of these plans and
oversight of their implementation remains a function of
state government.
The Florida Constitution, Article IV, Section 9, pla-
ces jurisdiction over terrestrial and freshwater animal
life with the Game and Fresh Water Fish Commission.
Chapter 372 of the Florida Statutes details the extent
and responsibility of this authority, and provides for
establishment of rules and regulations as necessary to
implement that authority. The Wildlife Code of the
State of Florida establishes rules regarding fish and
wildlife under Commission jurisdiction. Game species
and those listed as Endangered, Threatened, or Species of
Special Concern are managed via hunting or fishing regu-
lations or protective restrictions. Migratory nongame
birds and raptors are protected via inclusion of the
pertinent federal laws mentioned above. There are few
general regulations protecting habitats or other wildlife
such as nongame amphibians, reptiles, and mammals.
Under the Florida Endangered and Threatened Spe-
cies Act of 1977, responsibility for research and
management of freshwater and upland Endangered or
potentially endangered species is vested in the Florida
Game and Fresh Water Fish Commission, and respon-
sibility for marine species is delegated to the Florida
Department of Natural Resources. The Wildlife Code
prohibits killing, wounding, pursuing, molesting, harm-
ing, harassing, capturing, or possessing any Endangered





or Threatened species or parts thereof or their nests or
eggs without authorization by specific permit from the
Executive Director of the appropriate agency. Unfor-
tunately, as with the federal Act, there is little to pre-
vent habitat required by these species from being
destroyed.
The Preservation of Native Flora of Florida Act,
administered by the state Department of Agriculture
and Consumer Services, provides protection of native
plants listed as Endangered or Threatened from harvest
by persons other than the landowner, without the land-
owner's permission.,'While this might protect listed
plants from commercial exploitation, it provides no
protection from species eradication by landowners
intent on site development.


REGIONAL AUTHORITY

Regional control over upland development and pro-
tection of native habitats and wildlife is primarily
vested in the Treasure Coast Regional Planning Coun-
cil. This council is a powerful factor in determining the
extent and character of development permitted in, or
protection granted to, these natural communities.
The recently completed Regional Comprehensive
Policy Plan (Treasure Coast Regional Planning Coun-
cil 1987) contains a number of policy statements
regarding natural resource protection, many of which
directly affect scrub preservation. Some of the most
significant policies and implementing measures would:
(1) establish a regional preserve system to ensure pro-
tection of native plant and animal populations; (2)
require preservation of 25 percent of valuable upland
communities on project sites, with options for site-
specific mitigation; (3) establish impact fees to assist in
funding of nature preserve acquisition; (4) require local
governments to obtain advice from professional ecolo-
gists on land-use decisions which could adversely affect
natural resources; (5) require development of man-
agement plans for the region's natural systems; (6)
require ordinances regulating use of off-road vehicles in
native habitats; (7) require implementation of ordinan-
ces or other measures to direct development from
unsuitable lands (e.g., potential nature preserves) to
suitable lands; and, (8) prohibit activities which have a
reasonable likelihood of adversely affecting any popu-
lation of an Endangered or Threatened species.
These measures, when implemented via incorpora-
tion into county and municipal comprehensive plans
and ordinances, have the potential to provide a signifi-
cant degree of regional protection to scrub habitats and
their resident faunae. Because of the dearth of federal or
state protection of uplands, they are, in fact, the pri-
mary means of upland habitat protection in the region.
There are several shortcomings of the system, however.
(1) Regional planning councils are most directly
involved in developments of sufficient size or signifi-
cance to be considered Developments of Regional


Impact. Thus, piece-meal development of upland habi-
tats is often bereft of regional control. (2) Although a
regional planning council establishes performance
criteria and conditions that must be satisfied for a
project to proceed, the Development Order is issued by
the jurisdictional local government. Thus, discrepan-
cies may arise regarding interpretation of conditions
and performance criteria. (3) Regional planning coun-
cils are political entities, charged with balancing the
economic, social, and environmental benefits and
impacts of development. Despite policy statements to
the contrary, natural resource protection often is of
secondary importance compared to economic growth
and development.


LOCAL AUTHORITY

At the county level, each Comprehensive Plan is
replete with policy statements and objectives such as
the following:

"Environmentally sensitive lands and natural wild-
life habitats should be protected from land use
practices which would disrupt their natural func-
tions and reduce their contribution to the quality
of life and economic well being of the region"
(Saint Lucie County 1985:39).

"The county shall encourage the preservation of
native plant communities including: hardwood
hammocks, pine flatwoods, sand pine - scrub oak
associations, cabbage palm hammocks, mangrove
fringes and forests, estuarine marshes, forested
wetlands, prairies and sloughs by implementing the
following: 1. A native plant community, tree pro-
tection and land clearing ordinance. 2. The county
shall require that all new development preserve a
minimum of 25%, where possible, of the native
plant communities occurring on site as green space.
Mitigation for the loss of native plant communities
will be accepted to meet this requirement" (Indian
River County 1985:86).

"Native fish, vegetation and wildlife populations
and suitable habitats are important natural resour-
ces, especially within the St. Lucie River and Indian
River estuaries. . . . All endangered native species
of fish, vegetation, and wildlife and their respective
natural habitats shall be protected from adverse
development impacts" (Martin County
1982:VIII-4).

Unfortunately, such policy statements and objec-
tives are ineffectual unless implemented by county
ordinances. To that effect, Indian River County has a
tree ordinance which prohibits land clearing and pro-
tects most native trees over 8 inches dbh from being
removed unless a site development plan has been





approved. Site plan approval is based on appropriate-
ness of the proposed development with regard to the
county zoning ordinances and land use plan, neither of
which provides significant protection for scrub habi-
tats. The native plant community ordinance has never
been implemented, and the requirement that 25 per-
cent of native habitats be preserved is not strictly
enforced. Saint Lucie County has no ordinances pro-
tecting native trees or wildlife, nor is a permit required
prior to clearing of native habitats. Martin County
ordinances provide somewhat greater protection than
those of Indian River County, with the additional spe-
cific protection of sand pine scrub and pine flatwoods,
i.e., "... where these associations exist a minimum of
50% of the open space requirement of an affected
development shall consist of such native upland plant
preserve areas" (Martin County 1986).
Protection of scrub resources by city and town
governments is generally negligible. Landscaping ordi-
nances are common, but they pertain primarily to
maintenance of aesthetic conditions, with little rele-
vance to native habitats or wildlife preservation.
In summary, land use and development regulations
are inadequate to protect the natural resources of
upland habitats. Federal and state regulatory efforts are


strongly skewed in favor of wetland protection, and, by
default, have often encouraged upland habitat destruc-
tion. Furthermore, although those measures are poten-
tially valuable, their effectiveness is limited by: ".. . (1)
insufficient agency personnel to adequately monitor
violations, review plans, etc.; (2) problems with fund-
ing, administration and legal questions prevent many
programs from achieving full operational status; and
(3) general lack of public awareness and, in some cases,
acceptance of new programs" (Florida Department of
Natural Resources 1975). Regional control is signifi-
cant, and has potential to be much more effective in
these areas. Local ordinances covering such issues as
land-use planning, zoning, land clearing, tree protec-
tion, mining, pet control, littering, off-road vehicles,
and native landscaping offer significant potential for
protection of upland habitats and wildlife. To be effec-
tive, however, tremendous advances in appreciation of
natural resources and commitment to their preserva-
tion must be made by local government.













SECTION 4.


CRITERIA FOR SCRUB EVALUATION

AND PRESERVATION







Over the last two decades the concepts of species-
area relationships and island biogeographic theory
increasingly have been applied to habitat "islands" and
the design of nature preserves. Scrub communities of
the Treasure Coast Region, meanwhile, have become
fragmented, isolated, and reduced in area as a result of
land development. Thus, it is appropriate to review the
applicability of these theories to scrub preservation and
management.
Two additional topics, each of which has been in-
tensely debated, impinge on that discussion. The first
is: "How large must a population or preserve be in
order to protect a viable component of the natural
community or species?" The second is: "Assuming you
can determine these minimum viable population or
community sizes, is it better to create a single large
preserve or several smaller ones?"


SPECIES-AREA
RELATIONSHIPS AND ISLAND
BIOGEOGRAPHIC THEORY

Simply stated, the species-area relationship is the
tendency for large areas to support more species than
smaller areas. This phenomenon has been recognized
for over a century (Connor and McCoy 1979,
McGuinness 1984a), and has been reported for a va-
riety of taxa including plants (Arrhenius 1921; Gleason
1922, 1925; Williams 1943, 1964; Hopkins 1955;
Preston 1962a,b; Kilburn 1966; Johnson et al. 1968;
Johnson and Raven 1973; Johnson and Simberloff
1974; Harner and Harper 1976; Usher 1979; Buckley
1982, 1985; Game and Peterken 1984), invertebrates
(Culver et al. 1973, but see Culver 1970; Vuilleumier
1973 [in part]; Sepkoski and Rex 1974; Lassen 1975;
Abele 1976; Abele and Patton 1976; Simberloff 1976;
Shreeve and Mason 1980; Browne 1981; Rey 1981,
1984; Gunnill 1982; McGuinness 1984b), fish (Bar-
bour and Brown 1974, Browne 1981), reptiles (Levins
and Heatwole 1963, MacArthur and Wilson 1967,
MacArthur 1972, Case 1975, Wilcox 1978, Kitchener
et al. 1980a; but see Gibbons and Coker 1978), birds
(Preston 1960, 1962a,b; MacArthur and Wilson 1963,
1967; Hamilton and Armstrong 1965; Greenslade
1968; Diamond 1969, 1972, 1975; Vuilleumier 1970;
Power 1972; Terborgh 1973, 1974, 1975; Moore and
Hooper 1975; Diamond and Mayr 1976; Forman et al.
1976; Galli et al. 1976; Terborgh and Winter 1980;
Coleman et al. 1982; Kitchener et al. 1982; Opdam et
al. 1984), and mammals (Brown 1971, Dueser and
Brown 1980, Kitchener et al. 1980b, Lomolino 1982).
Four hypotheses have been proposed to account for
the species-area relationship (Connor and McCoy
1979, McGuinness 1984a). The first was the random
placement hypothesis, proposed by Arrhenius (1921)
and subsequently named by Coleman (1981), which


states that the species-area curve arises from random
placement of species, with larger areas thereby contain-
ing more species than smaller areas. This hypothesis has
been supported in studies of plants (Arrhenius 1921;
Gleason 1922, 1925; Williams 1943 [in part], 1964 [in
part]), marine algae and epifaunal invertebrates
(McGuinness 1984b [in part]), and birds (Coleman et
al. 1982). Other researchers, however, have rejected
this hypothesis (Simberloff 1976, Abbott 1981). Ran-
dom placement has been suggested as a null hypothesis
for current studies of the species-area relationship
(Connor and McCoy 1979, McGuinness 1984a,b; but
see Gilpin and Diamond 1984).
The second major explanation for the species-area
relationship was the habitat diversity hypothesis (Con-
nor and McCoy 1979) presented by Williams (1943,
1964). He proposed that, as the area sampled increases,
additional habitats and their respective species are
encountered; thus, the number of species increases
with area. Significantly, Preston (1960), MacArthur
and Wilson (1967), and MacArthur (1972), while
developing the Equilibrium Theory (discussed later),
emphasized the importance of habitat heterogeneity
and "edge effect" in species-area relationships. The
habitat diversity hypothesis was supported in studies of
flowering plants (Williams 1943 [in part], 1964 [in
part]; Hamilton et al. 1963, but see Johnson and Raven
1973; Johnson and Simberloff 1974, but see McCoy
and Connor 1976; Harner and Harper 1976; Buckley
1982; Westman 1983), alga-inhabiting invertebrates
(Gunnill 1982), decapod crustaceans on coral heads
(Abele 1974, 1976 [in part]), molluscs (Harman
1972), lizards (Kitchener et al. 1980a [in part]), birds
(Preston 1960, Johnson 1975), and small mammals
(Dueser and Brown 1980). This hypothesis, however,
has been rejected in studies of plants (Weaver and
Kellman 1981), decapod crustaceans (Abele and Pat-
ton 1976), terrestrial arthropods of mangroves and salt
marshes (Simberloff 1976 and Rey 1981, respec-
tively), and birds (Galli et al. 1976).
According to the disturbance hypothesis (McGuin-
ness 1984a,b), periodic events such as storms, mud-
slides, floods, fires, or ocean waves are responsible for
faunal extirpations. This hypothesis entails a gradient
of increasing disturbance rather than increasing area.
Frequently disturbed areas are only occupied by the
best colonizers or most tolerant species, and rarely
disturbed areas are eventually dominated by a few long-
lived or efficiently competing species. Thus, areas
which suffer intermediate levels of disturbance exhibit
the greatest species diversity. The hypothesis predicts a
species-area relationship in cases where the intensity of
disturbance is related to size of the "island" (e.g., small
rocks are overturned by waves more frequently than
are large rocks). This hypothesis has been supported
primarily in studies of marine algae and epifaunal inver-
tebrates (Osman 1977 [in part]; Sousa 1979a,b;
McGuinness 1984b). The relationship between distur-




bance events and plant species diversity has been dis-
cussed by Helliwell (1976) and Austin et al. (1987),
who felt that commercial timber management (Helli-
well) or frequent mowing (Austin et al.) decreased
species diversity, and by Weaver and Kellman (1981)
who concluded that periodic disturbance increased
forest species diversity.
The area - per se hypothesis (Conner and McCoy
1979) was developed by Preston (1960; 1962a,b) and
immortalized as a prediction and central concept of the
Equilibrium Theory of island biogeography (MacAr-
thur and Wilson 1963, 1967; MacArthur 1972).
Briefly, this theory states that the number of species on
an island tends toward an equilibrium number. This
number is the result of balance between: (1) the rate of
immigration (colonization), which decreases with dis-
tance from the source species pool but is relatively
independent of island size; and, (2) the rate of extinc-
tion, which is inversely proportional to population size
(which, in turn, is assumed to be directly proportional
to area), but is independent of distance from the
source. Thus, if distance from the source pool is held
constant, larger islands (supporting larger populations)
will possess lower rates of extinction, and support more
species at equilibrium than smaller islands. Because
immigration and extinction continue, change in species
composition (turnover) will occur, but at a constant
rate preserving the equilibrium number of species per
island. Data conforming to the predictions of Equili-
brium Theory have been reported for a variety of spe-
cies groups inhabiting oceanic or land-bridge island
systems including plants (Simpson 1974, McCoy and
Connor 1976, Buckley 1985), terrestrial arthropods
inhabiting salt marshes and mangroves (Simberloff
1969, 1976; Simberloff and Wilson 1969, 1970; Wil-
son and Simberloff 1969; Rey 1981, 1984), lizards
(Case 1975; Wilcox 1978, but see Faeth and Connor
1979; Kitchener et al. 1980a), birds (MacArthur and
Wilson 1963, 1967; Hamilton et al. 1964; Greenslade
1968 [in part]; Diamond 1969, 1972, 1975; Terborgh
1973, 1974, 1975; Diamond and Mayr 1976; Gilpin
and Diamond 1976: but see Lynch and Johnson 1974),
and mammals (Crowell 1973, Dueser and Brown 1980
[in part], Kitchener et al. 1980b, Lomolino 1982).
One of the theory's great attractions is its apparent
applicability to continental habitats possessing island-
like distribution (MacArthur and Wilson 1967;
MacArthur 1972; Simberloff 1974; Diamond 1975,
1978; May 1975; Terborgh and Winter 1980; Wilcox
1980; McGuinness 1984a). This concept was energeti-
cally received, fostering studies which reported data
consistent with predictions of the Equilibrium Theory
for flowering plants (Crowe 1979, but see Weaver and
Kellman 1981), cave fauna (Culver 1970 [in part],
Culver et al. 1973, Vuilleumier 1973 [in part]), cope-
pods (Hockin 1982), alga-inhabiting invertebrates
(Gunnill 1982), decapods on coral heads (Abele 1976
[in part], Abele and Patton 1976), molluscs (Sepkoski
and Rex 1974, Lassen 1975, Browne 1981), coral reef


fishes (Molles 1978), lizards (Kitchener et al. 1980a),
birds (Vuilleumier 1970; Moore and Hooper 1975;
Whitcomb et al. 1977, but see McCoy 1982) and
mammals (Kitchener et al. 1980b). Other studies of
fish (Barbour and Brown 1974, Browne 1981) and
mammals (Brown 1971) have discussed these faunae as
nonequilibrial due to extremely low rates of coloniza-
tion, without jeopardizing the validity of the Equili-
brium Theory. Smith (1979) refuted the applicability
of Equilibrium Theory to Gulf of Mexico reef fishes on
the basis of: (1) limited habitat insularization; and (2)
attainment of a stable climax community rather than a
dynamic equilibrium (but see Sale and Dybdahl 1975).
Equilibrium Theory has been invoked to postulate a
peninsular biogeographic effect by Simpson (1964),
Cook (1969, but see Robertson and Kushlan 1984),
and Taylor and Regal (1978), and has even been used to
explain the distribution and abundance of individual
species (Smith 1974, Fritz 1979, Godley et al. 1981). In
fact, to many researchers, Equilibrium Theory became
the cornerstone of island biogeographic theory.
The significance of this theory to nature preserve
design is immediately apparent. If we presume that
preservation of as many species as possible is one objec-
tive of preserve establishment (Cole 1981; but see
Diamond 1976, Simberloff and Abele 1982), and we
assume the validity of the Equilibrium Theory, we
arrive at the inescapable conclusion that nature pre-
serves should be as large as possible. Thus, a single large
refuge would generally be more valuable than several
smaller refuges with an equivalent total area (Diamond
1972, 1975, 1976; Terborgh 1974, 1975, 1976; May
1975; Moore and Hooper 1975; Forman et al. 1976;
Galli et al. 1976; Whitcomb et al. 1976; Faaborg 1979;
Shreeve and Mason 1980; Terborgh and Winter 1980;
Butcher et al. 1981; Cole 1981; Frankel and Soule
1981; Humphreys and Kitchener 1982).
It has been argued, however, that several smaller
refuges may often support more species than a single
large preserve (Simberloff and Abele 1976a,b, 1982;
Game and Peterken 1984; Soule and Simberloff 1986;
Miller et al. 1987; Woolhouse 1987). Circumstances
which may result in this condition include: (1) when
competitive exclusion indicates separate refuges for
distinct taxa (Abele and Patton 1976; Simberloff and
Abele 1976a,b; Abbott 1981); (2) when there are few
common species among the refuges (Cole 1981; Kitch-
ener et al. 1980a); (3) when the number of good dis-
persers is a small percentage of the species pool (Abele
and Patton 1976); or (4) when species being preserved
represent a small percentage of the total species pool
(Abele and Patton 1976; Simberloff and Abele
1976a,b; Cole 1981; Higgs 1981). In the last case,
Simberloff and Abele (1976a) argued that preservation
of a single large refuge could be the worst approach to
species preservation. Furthermore, Saunders et al.
(1985), in a synopsis of a workshop on managing
vegetative remnants, identified the following conserva-
tion values attributable to small tracts, emphasizing that






they should not be overlooked in preserve system
design:

"- they provide representative or selected sam-
ples of ecosystems that were once more extensive;

"- they often contain landscape and biotic ele-
ments, including rare species, that are not other-
wise protected;

"- they can provide multiple samples of species
throughout their former range, thus sustaining
genetic variability;

"- they provide stepping-stones and/or corri-
dors for many species, and enhance gene-flow;

"- they are important to surrounding lands by
affecting hydrology, nutrient cycling, and erosion;

"- they have aesthetic, educational, and recrea-
tional values; and,

"- they help to create a public awareness of
nature and nature conservation, especially
amongst rural people."

Another important prediction of Equilibrium The-
ory is that reduction in area of a habitat "island" (e.g.,
via destruction of a land-bridge, or fragmentation of a
contiguous tract via land development) would upset
the species-area equilibrium. "Relaxation" of the spe-
cies number, through species extirpations, would then
occur until a new, lower equilibrium number of species
was attained which better represented the appropriate
species-area curve (MacArthur and Wilson 1967;
Brown 1971; Diamond 1972, 1975; Simpson 1974;
Terborgh 1974, 1975, 1976; Case 1975; Pickett and
Thompson 1978; Wilcox 1978, 1980, but see Faeth
and Connor 1979; Terborgh and Winter 1980). Thus,
nature preserves established in recently fragmented
ecosystems could be expected to suffer future species
extirpations until the new species-area equilibrium is
established.
Despite their widespread popularity and application,
the species-area relationship and Equilibrium Theory
have not been universally accepted. Much of the con-
troversy results from four important features of natural
populations and the theory. (1) Area only rarely
directly influences the number of species. Usually, area
affects other factors (e.g., habitat diversity and popula-
tion sizes) which, in turn, affect the number of species
(MacArthur and Wilson 1967, MacArthur 1972,
Simberloff 1974). (2) Immigration (colonization) is
influenced not only by distance from the source, but
also by dispersal ability of the colonists, relative inhos-
pitality of the intervening terrain, and reproductive
capacity of the colonists. (3) Extinction probability, as
influenced by population size, is a function of popula-


tion genetics and demographics, interspecific competi-
tion, predation, and random catastrophic events. (4)
Categories of islands (e.g., oceanic, land-bridge, or ter-
restrial habitat "islands") are expected to behave dif-
ferently according to Equilibrium Theory. Considera-
tion of all these factors results in wide and variable
immigration and extinction bands, as opposed to dis-
crete, mathematically-derived curves. Thus, it is
extremely difficult to conclusively prove or disprove
Equilibrium Theory, or to invalidate the alternative
hypotheses. In fact, several researchers have discussed
the role of each hypothesis, and implicitly acknow-
ledged these factors as complimentary, rather than mutu-
ally exclusive, in their effect on species-area curves and
island equilibria (Connor and McCoy 1979, Gunnill
1982, McGuinness 1984b, Seagle and Shugart 1985).
Some researchers, including Diamond (1972, 1975,
1976), Simberloff( 1974; but see Simberloff and Abele
1976a,b), Terborgh (1974, 1975, 1976), May (1975),
and Whitcomb et al. (1976), have advocated use of
these theories in nature preserve design. Other recent
reviewers of species-area curves and their attendant
theories and statistics (Connor and McCoy 1979,
McGuinness 1984a), methodologies and statististical
analyses in the literature supporting the Equilibrium
Theory (Lynch and Johnson 1974, Slud 1976, Gilbert
1980, McCoy 1982, McGuinness 1984a), and theoret-
ical problems associated with using simplistic formulae
as models of complex ecological systems (Sauer 1969;
Simberloff and Abele 1976a,b; Wiens 1984; Shmida
and Wilson 1985) have urged extreme caution in
accepting the validity of these hypotheses, especially
with regard to nature preserve design. Indeed, the great-
est relevancy of these theories may be their acknow-
ledged heuristic value, rather than their deterministic
properties regarding species abundance, distribution,
and preservation.



MINIMUM VIABLE
POPULATION SIZE


The species-area relationship and island biogeogra-
phic theory suggest that as the area of a tract is reduced
by development, the number of species expected to
occur will decline. Although these theories enhance our
understanding of the number of species expected to
occur on the basis of area, they provide little guidance
concerning the fate of any given species as area is
reduced, though several researchers have attempted to
address this issue (Brown 1971; Terborg 1973; Dia-
mond 1975, 1978; Faaborg 1979). Continued pres-
ence of a species on a scrub habitat "island" is deter-
mined by the minimum viable population size of that
species, and whether or not sufficient area and other
resources are available to support a population of that
size.





A working definition of a viable population was
proposed by Marcot et al. (1986:11):

"A viable population is one whose likelihood of
continued existence in a planning area for a speci-
fied time is judged by responsible individuals to
meet the requirements pursuant to the mainte-
nance of biological diversity."

The concept of minimum viable population size is
entrenched in genetic theory as a function of the calcu-
lated rate of loss of genetic variability (Franklin 1980,
Lacava and Hughes 1984). In the long-term (evolution-
ary time), the probability that a population will go
extinct is a function of loss of genetic heterozygosity, a
process which reduces the ability of a species to adapt
to changes in its environment (Franklin 1980, Marcot
et al. 1986). Loss of genetic variation renders a species
more susceptible to extinction. In the short-term (eco-
logic time), however, the primary genetic concern with
regard to small population size is inbreeding depression
(Senner 1980, Chesser 1983, Lehmkuhl 1984). This is
the reduction in vigor and fecundity of a population
that results from increased numbers of matings by
closely related individuals.
In the case of scrub "islands" we are concerned with
ability of the habitat to support a sufficient number of
individuals of a given species to maintain the popula-
tion and prevent inbreeding depression. To determine
the smallest population size capable of avoiding
inbreeding depression, geneticists have developed the
concepts of effective population number (Wright 1931,
Kimura and Crow 1963) and minimum effective popu-
lation (Franklin 1980, Soule 1980). These refer to
"ideal" populations in which all individuals mate ran-
domly, there are equal numbers of sexes, there is no
variation in number of young per breeder, and genera-
tions do not overlap. Obviously, such conditions are
not common in nature (Lehmkuhl 1984, Shull and
Tipton 1987). Minimum effective population size is a
function of the rate of loss of heterozygosity which, as
applied by Franklin (1980), Soule (1980), and Lehm-
kuhl (1984), should not exceed 1% per generation for
wildlife populations. The calculated minimum effective
population size for an "ideal" population as described
is 50 breeding adults. Senner (1980) and Lehmkuhl
(1984) estimated that a minimum effective population
has an effective short-term interval of 90 generations.
In other words, an isolated "ideal" population of 50
breeding adults is subject to extirpation after about 90
generations, as a result of vigor and fecundity decline
associated with inbreeding depression.
There are several factors which could render min-
imum effective population size less critical with regard
to minimum preserve acreage. First, most species which
inhabit scrubs are not restricted to scrub habitats.
Thus, adjacent habitats could contribute significantly
to maintenance of the minimum effective population.
Secondly, species which have endured long-term low


levels of inbreeding or reduction of genetic diversity
(typically encountered in many endemic species) may
have gradually eliminated the deleterious alleles which
are of concern in the genetic aspects of extinction prob-
ability (Lehmkuhl 1984). Third, immigration of only
one or two individuals per generation may be sufficient
to preserve a sufficient level of genetic diversity (Brown
and Kodric-Brown 1977, Franklin 1980; but see
Chesser 1983). This easily could be achieved by species
with high dispersal abilities or, if necessary, might be
accomplished via transplanting of individuals between
populations (Lehmkuhl 1984).
Minimum viable population (MVP) was workably
defined by Shaffer (1983) as the "smallest isolated
population having at least a 95 percent probability of
surviving at least 100 years." This is obviously a tenta-
tive definition, as both the survival probability and
time frame are somewhat flexible. Shaffer (1983) also
included non-genetic factors which would significantly
affect population survival. Recent studies (Shaffer
1983, Samson et al. 1985, Shaffer and Samson 1985,
Marcot et al. 1986, Soule and Simberloff 1986, Cox et
al. 1987, Goodman 1987, Harris et al. 1987) have
emphasized the importance of stochastic or systematic
variation in demographic, environmental, and cata-
strophic factors which affect population viability, as
opposed to relying primarily on genetic considerations.
Lehmkuhl (1984) outlined the following procedure
for deriving the actual required population size for
short-term and long-term preservation of a species.

1. Start with the minimum short-term effective
number of 50 individuals.

2. Account for variance in progeny number (the
number of offspring surviving to reproduce).

3. Adjust for unequal sex ratios, including social
behavior or other factors which preclude breed-
ing by all members of the population.

4. Provide for overlapping generations, as discussed
by Hill (1973), Lehmkuhl (1984), Reed et al.
(1986), and Cox et al. (1987).

5. Adjust for anticipated population fluctuations,
based on documented levels of population fluc-
tuation for the species under consideration. This
step is intended to preclude an average popula-
tion from dropping below the size developed in
steps 1-4.

6. Adjust for the planning period. For long-term
preservation, the number from step 5 should be
multiplied by 10.

Without presenting the actual equations presented
by Lehmkuhl (1984), suffice it to note that each of
steps 2-5 could significantly increase the number of





animals required to achieve an effective population size
of 50 animals. Several authors have derived minimum
viable population sizes for preservation of selected spe-
cies (Shaffer 1983, Lacava and Hughes 1984, Lehm-
kuhl 1984, Shaffer and Samson 1985, Reed et al. 1986,
Richardson et al. 1986, Cox et al. 1987). In these
studies, short-term preservation has generally required
an actual population size of about 50 to 500 animals.
Lehmkuhl stressed that, "Populations with no foresee-
able expansion of habitat must be managed for long-
term MVPs. This is a critical concept that requires
extreme caution since the fate of local populations
depends on proper assessment of present and future
conditions." If multiplication by a factor of 10 is per-
formed as recommended in step 6 above (Franklin
1980, Lehmkuhl 1984), long-term preservation would
likely require a population of approximately 500 to
5,000 individuals.


GENERIC PRESERVE DESIGN

As discussed above, design of nature preserves has
emerged as a significant, albeit poorly deterministic,
application of genetic, ecological, and biogeographic
theory. Ecosystem processes (Kushlan 1979), patch
dynamics (Pickett and Thompson 1978), and integra-
tion of these various factors (Soule and Simberloff
1986) also are important considerations in preserve
design. In their proposal for establishment of a scrub
preserve in Palm Beach County, Richardson et al.
(1986:16-18) presented an excellent set of generic
guidelines for preserve establishment and management.
These recommendations are especially pertinent to the
problem of scrub preservation in the Treasure Coast
Region.

"1. WHEN AN OPTION IS AVAILABLE, LARGE
PRESERVES SHOULD BE FAVORED OVER
SMALLER ONES. Larger preserves can support
larger populations and therefore extinction is less
likely. Larger populations are more likely to sup-
port emigration to nearby suitable habitat. Like-
wise, larger populations will generate surplus
numbers which may be transplanted to unoccu-
pied but otherwise suitable habitat beyond the
range of natural dispersal. Immigration rates are
normally higher to larger reserves. The preserva-
tion of entire ecosystems with all trophic levels
represented requires large areas. Lastly, larger
preserves are more likely to be buffered against
disturbance by man and natural disasters (Whit-
comb et al. 1976, Frankel and Soule 1981,
Butcher et al. 1981).

2. TOP CARNIVORES MAY ONLY BE PRE-
SERVED IN LARGE PRESERVES. This is espe-
cially true for birds and mammals. Trophic posi-
tion and movement patterns (spatial require-


ments) largely explain this observation. Likewise,
the bottleneck of small effective population size
may be avoided on large preserves (Galli et al.
1976, Franklin 1980, Frankel and Soule 1981).

3. SEVERAL DISTINCT HABITAT TYPES
SHOULD BE INCLUDED IN A NATURE
PRESERVE. Patchiness promotes species diver-
sity. Marginal habitats, when juxtaposed with
optimal habitats, serve as dispersal sinks and
buffer population fluctuations. Marginal habitats
serve as corridors between preferred habitats and
promote population exchange (gene flow) and
recolonization. Larger preserves are more likely
to have a diversity of habitat types (Hooper 1971,
Diamond 1975, Dueser and Brown 1980).

4. CORRIDORS BETWEEN PRESERVES MAY
PERMIT POPULATION EXCHANGE AND
RECOLONIZATION IN THE CASE OF
LOCAL POPULATION DECLINES. Need for
corridors will depend on dispersal abilities of
species in question and the relative isolation of
similar reserves (Hooper 1971, Diamond 1975,
MacClintock et al. 1977).

5. THE SUCCESS OF PRESERVES DEPENDS IN
LARGE MEASURE ON OUR KNOWLEDGE
OF SPECIES BIOLOGY AND ECOSYSTEM
PATTERN AND PROCESS. Mere establish-
ment of a preserve does not ensure preservation
of an endangered species (Baker 1978, Massey
and Whitson 1980, Frankel and Soule 1981,
Shaffer and Samson 1985, Samson et al. 1985).

6. PRESERVE MANAGEMENT THAT
ATTEMPTS TO FAVOR ONE SPECIES IS
LIKELY TO INFLUENCE OTHER SPECIES. A
clear understanding of objectives and their rami-
fications should be established before the envi-
ronment is manipulated to favor one species
(Dempster 1977, White and Bratton 1980).

7. PRESERVES FOR ENDANGERED SPECIES
SHOULD BE SUFFICIENTLY ISOLATED
FROM ONE ANOTHER SO AS TO AVOID
WIDESPREAD LOSSES OWING TO EPIDEM-
ICS. Dispersal abilities of organisms in question
determine isolation distance (Frankel and Soule
1981).

8. NATURAL PRESERVES REMAIN DYNAMIC
AFTER ESTABLISHMENT. It is essential that
management objectives be established to avoid
the dilemma of ecological change from benign
neglect which is detrimental to the species or
ecosystem for which the preserve was originally
established (Pickett and Thompson 1978, White
and Bratton 1980).






9. THE SMALLER THE MANAGEMENT UNIT
THE MORE LIKELY OVERT MANAGE-
MENT WILL BE NECESSARY TO MAIN-
TAIN THE ORIGINAL CONSERVATION
VALUE OF THE UNIT. For example, rare spe-
cies might have to be artificially reintroduced
owing to local extinction (Hooper 1971, Pyle
1980)."

IMPLICATIONS FOR SCRUB
PRESERVE DESIGN

Minimum Area for Regional Scrub Preserves

Several researchers have pursued the relevancy of the
species-area relationship and Equilibrium Theory to
scrub habitats of southeast Florida, and have deter-
mined that the size of scrub "islands" does not deter-
mine the number of representative or endemic plant
species found per island (Richardson et al. 1986; Aus-
tin et al. 1987). Austin et al. (1987) reported that:
"Decrease in species richness is somewhat correlated
with reduction of habitat area, but not to the extent that
might be expected by island biogeographic theory . . .
modern size [area] is not a reliable estimate of the
probable species richness, and will not allow prediction
of the future changes in richness." Similarly, Connery
(1984) found that area was not a good predictor of
plant species richness in east-central Florida sand pine
scrubs. There are several possible explanations for
these findings including, but not necessarily limited to,
those following.

1. Due to relatively recent dissection of the "land-
bridge" of continuous coastal scrub habitat, these
scrubs are supersaturated with more species (but
not necessarily with more individual plants or
animals) than they could normally support.
Thus, they are in the initial stages of "relaxation"
as predicted by Equilibrium Theory (Austin et al.
1987).

2. Because most of the flora of scrub habitats are not
found exclusively in scrubs, they do not truly
represent a terrestrial archipelago which could be
expected to conform to island biogeographic
theory.

3. Non-random movements of animals from one
scrub "island" to another may upset the pre-
dicted rates of immigration of plant propagules,
and through this enhancement of population size
and genetic diversity, also influence the rate of
local extirpation.

4. Scrub plant population sizes are not determined
by area within the range of areas sampled; thus,
the extirpation rates are not adequately predicted
by area.


5. Habitat disturbance by man, invasion by exotic
plants and animals, and changes in adjoining hab-
itats have disrupted the anticipated equilibrium
to such an extent as to mask any actual effect of
the species-area relationship.

6. The endemic flora of scrubs is especially well
adapted to its environment, such that predicted
rates of extirpation do not occur.
Although apparently not a major factor in the pres-
ervation of most plant species, preserve size may be
more critical to management of animal species of spe-
cial interest. In a timely summary of genetic and ecolog-
ical aspects of refuge design, Soule and Simberloff
(1986) proposed a three-step process for determining
minimum preserve size: (1) identify target or keystone
species; (2) determine the MVP for these species; and
(3) estimate the area needed to sustain these popula-
tions. Although highest-order predators and other spe-
cies with large area requirements (e.g., Florida panther,
Florida black bear, gray fox, bobcat, raptors) are often
cited as such target species, they are inappropriate in
this situation because of extreme rarity (i.e., Florida
panther, Florida black bear), or because the area
requirements for viable populations greatly exceed the
acreage available for establishment of new scrub pre-
serves. Species groups (e.g, reptiles, breeding birds) or
ecological guilds (e.g, cavity-nesting insectivorous
birds) could also be utilized as selection criteria. These
methods also are inappropriate because most species
thus sequestered would not be especially characteristic
of scrubs. Consequently, such criteria would favor
preservation of generalist species over scrub specialists.
Since the impetus of this project is to preserve scrub
species, the most appropriate criteria include: (1) key-
stone species which are of value to many other scrub
species (i.e., gopher tortoise); (2) endemic species (i.e.,
Florida mouse, Florida scrub jay, scrub lizard); and (3)
typical scrub species which are listed as Endangered,
Threatened, or Species of Special Concern (i.e., Florida
mouse, Florida scrub jay, gopher tortoise, eastern
indigo snake, Florida pine snake, gopher frog).
There are only two published accounts specifically
oriented toward determining area requirements for sus-
taining minimum viable populations of these species.
Richardson et al. (1986) estimated area requirements
for viable populations of gopher tortoises (55.5 acres)
and Florida mice (50 acres) in support of their preserve
plan for the Yamato Scrub in Palm Beach County. They
assumed that populations of 50 breeding individuals
meet the established genetic criteria for reduction of
extinction probability to an acceptable level, and then
doubled that number to 100 animals to adopt a conser-
vative posture. The acreage required to sustain 100
animals of each species, coupled with the requirement
for habitat management to maintain several succes-
sional stages, then led to their recommendation of
approximately 56 acres being an acceptable size for a
specific scrub preserve (i.e., Yamato Scrub).





Richardson et al. (1986) reported early-spring Flor-
ida mouse population densities of 1.7 and 2.6 mice per
acre on their trapping sites. Other studies indicate that
Florida mouse densities in suitable scrub habitat may
range from less than 1 mouse per acre to over 10 mice
per acre (Dr. James Layne, pers. comm.). There is
tremendous variation in Florida mouse densities
between superficially similar scrubs, however, so it
would be extremely difficult to estimate population
sizes on a given tract without detailed site-specific
information (Dr. Jack Stout, pers. comm.). Polygyny
among Florida mice (Eisenberg 1983), and numerous
environmental factors (e.g., habitat quality, predator
abundance, availability of suitable burrows, and intro-
duction of exotic species), further complicate determi-
nation of minimum viable population sizes or acreage
required. An optimal scrub tract as small as 10 acres
may be adequate for short-term population survival,
but 40 to 50 acres is suggested as a more appropriate
scrub preserve size for sustaining a population of Flor-
ida mice (Dr. James Layne, pers. comm.).
The other study, by Cox et al. (1987), provides a
review of gopher tortoise biology and management
options. Cox et al. (1987) estimated the MVP for
gopher tortoises via two separate procedures. The first
method was derived from Reed et al. (1986), and paral-
lels the procedure of Richardson et al. (1986) and
Lehmkuhl (1984) in that it determines the required
actual population size as a function of an effective popu-
lation size equaling 50. This method resulted in a
required actual population of 50-80 gopher tortoises,
depending on the percentage of reproductively active
adults (50-75%). The other method utilized the com-
puter simulation model POPDYN (Perez-Trejo and
Samson, undated; cited by Cox et al. 1987) to analyze
population characteristics such as survivorship, fecun-
dity, and mortality for different age classes. The model
incorporates deterministic and stochastic variables,
reiterating them to simulate population responses to
inbreeding depression and changing environmental
conditions through time. This method resulted in pop-
ulations of 40 to 50 gopher tortoises having a 90 per-
cent chance of persisting for 200 years under favorable
habitat management conditions, satisfying the criteria
for a "viable" population.
Upon considering the shortcomings and inherent
risks of each method of determining the MVP, Cox et
al. (1987:29) concluded that while ". . . very small
gopher tortoise populations have good chances of per-
sisting for several decades when presented with favor-
able conditions," populations of 40 to 50 individuals
are required to satisfy the established criteria for popu-
lation viability. After reviewing the movement patterns
and home range requirements of gopher tortoises, they
further concluded (p. 31) that, ". . . an appropriate
guideline for the minimum area requirement of a
gopher tortoise population of 40-50 individuals found
on potential development sites is 25-50 acres (10-20
hectares), provided that proper preserve design and


habitat management accompanies such a recommenda-
tion." Although scrubs do not normally constitute
optimal habitat for gopher tortoises, approximately 50
acres is considered a reasonable minimum area for
preservation of a viable gopher tortoise population on a
managed scrub preserve (Jim Cox, pers. comm.).

Determining area requirements for Florida scrub jays
poses a particularly vexing problem. Woolfenden and
Fitzpatrick (1984) determined that, on the Archbold
Biological Station, scrub jay territory size averaged
approximately 23 acres in suitable habitat, ranging
from 3 to 52 acres in area. They reported newly estab-
lished territories to average about 10-11 acres, though
these normally expanded to near average size within a
couple of years. New territories as small as 5 to 7 acres
were successful, however, and this was their "best
guess" of the minimum size necessary for viable territo-
ries on their study area. Westcott (1970) determined
an average territory size of 6 acres, with a range of 3.8 to
7.5 acres. These differences in territory size may be
primarily due to habitat characteristics of the study
areas, or to the territory delineation methods utilized
by Westcott.
Woolfenden and Fitzpatrick (1984) reported that
average scrub jay territories are significantly larger than
would be necessitated by food availability. They dis-
cussed this tendency as arising from several factors: (1)
residence of more than two mature jays in most territo-
ries; (2) "land-banking" as an investment by non-
breeders for their future breeding potential (Wool-
fenden and Fitzpatrick 1978); and (3) advantages to
dispersers of having greater numbers of neighboring
territories. Thus, approximately 5-10 acres appears to
comprise the minimum territory size likely to support a
pair of scrub jays, with two or more times this acreage
being the average territory size in a relatively undis-
turbed and breeder-saturated population. Relevant to
this conclusion is Cox's (1984) estimate that 1 bird per
5 acres is probably the maximum density attainable on
scrub community preserves. Further complicating the
situation is evidence (Breininger 1981; Cox 1984,
1987; this study) that scrub jays may persist indefi-
nitely in residential or recreational developments, pro-
vided some patches of scrubby oaks remain as vacant
lots, hedgerows, or "green spaces."
Considering the territoriality of this species, and the
requirement for maintaining specific habitat condi-
tions, it is unlikely that a "viable" population can be
supported on any but the very largest scrub preserves.
Unfortunately, very little is known of the reproductive
success or dispersal characteristics of small, isolated
scrub jay populations. It is likely that such small popu-
lations scattered throughout the region actually func-
tion as a metapopulation or "population of popula-
tions" (Shaffer 1985). In this event, it is imperative that
scrub jays be preserved wherever they occur, with each
isolated population being recognized as an integral part
of a larger, regional scrub jay population.






Thus, it is apparent that there is no "minimum pre-
serve size" which would be universally applicable for
scrub jay management in the Treasure Coast Region.
While as little as 5 or 10 acres of suitable habitat may
support a mated pair, these isolated "populations"
would be extremely susceptible to extirpation, and
recolonization of the vacated habitat may be unlikely.
Management via prescribed burning or mechanical
renovation would require several habitat blocks, result-
ing in a recommended minimum preserve area of about
15 to 30 acres for a single territory. This acreage
approximates the normal territory size in scrubby oak
flatwoods, and the marginal value of earliest and later
successional stages (due to management activities) may
compensate for the minimal area of optimal habitat.
This minimum preserve acreage is recommended with
some reservation: until more definitive guidelines are
supported by research, each scrub jay population
should be studied to determine appropriate preserve
boundaries and management schemes on a case-by-case
basis, rather than relying on an "average" territory size.
Gopher frogs present a unique dilemma because they
are closely associated with gopher tortoise burrows,
and require temporary, grassy breeding ponds.
Although no data on gopher frog densities were found,
Franz (1986b) captured 100 gopher frogs, over a 16-
month period, on a 38-acre plot adjacent to known
breeding ponds. Because of their close association with
active tortoise burrows, we assume that a scrub which
provides adequate breeding ponds and food supplies,
and which supports a viable population of gopher tor-
toises, would be sufficient in area to sustain gopher
frogs.
The other vertebrates of special interest (eastern
indigo snake, Florida pine snake, and scrub lizard) are
less useful for determining the recommended min-
imum acreage regarding scrub preserve design. Eastern
indigo snakes and pine snakes require comparatively
large territories or home ranges, so viable populations
could not be wholly maintained on designated pre-
serves, with the possible exception of the Jonathan
Dickinson State Park - Hobe Sound National Wildlife
Refuge area. At the other extreme, scrub lizards may
attain densities of 12 individuals per acre or greater
(Jackson and Telford 1974), so minimum viable popu-
lations should be attainable on virtually any tract which
is otherwise suitable for a scrub preserve.
Perhaps the most critical factor in determining min-
imum preserve size for scrub communities is the impor-
tance of maintaining distinct successional stages within
the preserve area, each of which is large enough to
represent an intact unit of the scrub community and is
capable of being managed efficiently via prescribed
burning or mechanical renovation. Within their
recommended preserve, Richardson et al. (1986)
established three management units representing early,
middle, and mature successional stages. These units
would be burned on a rotational schedule, with each
section being burned at intervals of 15 to 60 years. We


concur with this approach, and agree that three man-
agement units would be sufficient to adequately reflect
normal scrub succession within a preserve. The only
existing minimum area guidelines for scrub manage-
ment units are the proposals by Ecological Consultants
and Quantum Associates (1986) and Richardson et al.
(1986), both of which recommended management
units of 10 to 20 acres. This would result in a minimum
scrub preserve size of 30 to 60 acres.
Richardson et al. (1986) stated that, "... no one has
suggested how large a sand pine scrub site should be to
maintain the integrity of the system." They also cau-
tioned that, "the greatly restricted amount of land
available for purchase, coupled with limited funds
available for procurement, makes it doubtly (sic)
important that preserves be no less than the so called
'minimum ecosystem size."' After consideration of (1)
minimum viable population sizes for scrub species of
primary concern, (2) consequences of habitat or popu-
lation isolation, (3) natural succession of scrub com-
munities, and (4) need for sufficient area to permit
effective site management, we conclude that 50 acres
is a generally acceptable minimum size for short-
term preservation of scrub communities, with
larger tracts being increasingly desirable. Smaller
tracts should only be considered where preservation of
an Endangered, potentially endangered, or endemic spe-
cies population is of singular importance, and where
intensive management is feasible. Obviously, this figure
may vary, depending on the species or communities to
be preserved, the need for buffering the preserve from
adjacent land-uses to ensure that a single catastrophic
event would not destroy the entire population or com-
munity, and the desire to accommodate significant
human use of the tract.

Minipreserves and Corridors

Despite this recommendation for a minimum
regional scrub preserve size of 50 acres, smaller tracts
should not be considered lightly. Tracts of 10 to 15
acres would be sufficient for establishing and managing
botanical preserves, and could provide adequate area
for scrub lizards and many invertebrate species. Small
tracts could easily serve as minipreserves for Endan-
gered or Threatened plant species, and could be incorpo-
rated into "green spaces," parks, and landscape buffers
within development projects.
Of particular relevance to this topic, Campbell and
Christman (1982b) demonstrated that the reptiles and
amphibians found in scrubs are primarily responsive to
habitat structure rather than plant species composition.
Thus, some disturbed sites may retain their habitat
value for these species. Also, Breininger (1981) and
Cox (1984, 1987) documented scrub jays utilizing
patches of scrub which were much smaller than their
normal territory size, and which were severely dis-
turbed and fragmented. The author has observed scrub
jays utilizing remnant scrub patches in suburban set-






tings, and pine flatwoods with a relatively minor com-
ponent of xerophytic oaks, compared to their preferred
scrub or coastal strand habitat (research in progress).
Furthermore, migrating or wintering birds and most
wildlife species which are able to exist in a relatively
developed setting utilize linear tracts of scrub habitat as
escape cover, nesting sites, or travel corridors.
Public easements and rights-of-way along highways,
major rivers, utility corridors, and railroad tracks may
constitute valuable scrub habitats or corridors. Where
these land uses occur on fragmented or disturbed linear
tracts of scrub (and even non-scrub) habitats, individu-
ally they may be of little preserve value. Collectively,
however, they comprise resources of regional impor-
tance. Not only do they provide travel corridors and
"stepping stones" for plant and animal movement
between larger preserves, but their disturbed and frag-
mented nature may belie their actual value (MacClin-
tock et al. 1977). Provision of corridors, however,
entails inherent risks and benefits. While the likelihood
of population extirpation is decreased, and chances of
recolonization are increased, the spread of epidemics of
disease or parasitism may also be enhanced. Similarly,
immigration of individuals from other preserves may
reduce inbreeding depression, but it could also result in
"pollution" of a small population's genetic structure.
Potential values and problems associated with corridor
establishment are further discussed by Cox et al.
(1987), and by Simberloff and Cox (1987).


SCRUB PRESERVE SELECTION


Individual preserve design and selection, as stated by
Richardson et al. (1986), "must begin with a clear
statement of the objective to be achieved by the action
of 'preservation' of a given landscape unit." Although
preserves likely will be created to protect various scrub
resources, it is possible to identify the variables which
will be most important in evaluating potential preserve
sites. Several researchers have pursued this task for
various preserve systems (Gehlbach 1975; Goldsmith
1975, 1987; Margules and Usher 1981; Miller et al.
1987), or have investigated the relative efficacy of
alternative preserve selection strategies (Game and
Peterken 1984, Goldsmith 1987, Miller et al. 1987).
Unfortunately, no simple strategy or consensus has
emerged from these studies, but they are useful in
providing guidelines for improving the selection pro-
cess. Attributes of greatest importance in scrub pre-
serve selection include preserve distribution, commun-
ity effects, area effects, species composition, habitat
quality, management implications, social values, and
logistic considerations. These may be subdivided as
follows to facilitate site evaluation.

1. Preserve distribution - The overall objective is to
protect samples of each major resource value


throughout the region. Thus, distribution and
character of previously established preserves
should be a major factor in selection of new
tracts.

2. Community effects - Tracts including manageable
areas of several different scrub community types
could be of greatest value, as would tracts within
large surrounding areas of native habitats or rela-
tively low levels of human disturbance. These
variables may be distinguished as follows:

(a) presence of distinct, manageable scrub
communities within the preserve tract;

(b) presence of substantial areas of other native
communities within the preserve tract, which
would contribute to the ecological value of the
preserve; and,

(c) location of the preserve tract within a larger
natural system, or area of low-intensity
disturbance.

3. Area effects - As discussed, size is an important
factor in preserve design. There are three primary
considerations with regard to individual preserve
selection:

(d) size of scrub communities within the pre-
serve tract;

(e) total area of the intended preserve, includ-
ing non-scrub habitats; and,

(f) shape, with circular or compact tracts pre-
ferred to linear ones. Also, contiguous scrub
tracts are preferred over several smaller tracts
within a proposed development site.

4. Species composition - Individual species are
obviously important considerations, and may be
evaluated as follows:

(g) species richness for various taxa (e.g.,
plants, invertebrates, amphibians, reptiles, birds,
mammals);

(h) number of endemic scrub species in various
taxa;

(i) number of species listed as Endangered,
Threatened, or Species of Special Concern; and

(j) abundance and diversity of species consid-
ered in (g) through (i) above.

5. Habitat quality - This feature may vary greatly,
depending on the community involved, past dis-





turbances, and successional stage. Even though it
may be significantly improved in many cases via
proper management, overall habitat quality
should be assessed, either quantitatively or sub-
jectively, by considering several factors
including:

(k) community "vigor," as determined by age
and condition of important species such as sand
pine, rosemary, and other endemic or indicator
scrub species;

(1) degree of invasion by exotic species; and,

(m) evidence of past human disturbance.

6. Management implications - Because habitat man-
agement will comprise the most important aspect
of preservation, several factors must be
considered:

(n) need for immediate management actions;

(o) potential for restoration of disturbed areas;
and,

(p) management potential (e.g., legal restric-
tions, safety hazards, or financial considerations).

7. Social values - These may be especially important
with regard to local government or community
endorsement of preserve establishment, and
include:

(q) nature-oriented recreational value (e.g.,
hiking, camping, birdwatching, nature
photography);

(r) recreational development potential (e.g.,
disturbed areas suitable for picnic areas or ball
fields);

(s) educational value as an outdoor laboratory
for public schools or civic organizations; and,

(t) scientific research value.

8. Logistic considerations - Obviously, not all tracts
will be equally suitable for inclusion in a preserve
system, even if their ecological and social values
are comparable. Additional considerations
include:

(u) relative degree of threat to the tract (i.e.,
development potential);

(v) willingness of the landowners to sell or lease
the tract;


(w) management or use restrictions imposed by
landowners (especially applicable to privately
owned preserves); and,

(x) total cost and cost-per-acre.

There is no satisfactory method of creating a single
index to incorporate these objective and subjective
measures of suitability for inclusion in a preserve sys-
tem, although some authors have advocated such indi-
ces (Gehlbach 1975, Goldsmith 1975; but see Gold-
smith 1987). Instead, comparison of these criteria
could be made as follows, and evaluated relative to the
objectives for the particular preserve. First, each varia-
ble could be given a subjective value of 1 to 4 based on
the following scale: 1 = low value; 2 = moderate value;
3 = high value; and 4 = conditions which warrant
serious consideration of the tract regardless of other
criteria (i.e., the only known population of an Endan-
gered, potentially endangered, or endemic species).
The average score for each major attribute (1-8) would
then provide one subjective evaluation of preserve
value. Another "index" would utilize the individual
scores for each variable considered (1, and a-x). This
would provide another value, indicative of the average
score if all variables were considered equal. In some
cases, certain attributes may be of greater importance
than others in assessment of a particular tract. Weight-
ing of each variable or attribute could be applied as
appropriate. These selection criteria present various
site characteristics which were considered in the selec-
tion of recommended preserve tracts (see POTEN-
TIAL SITES FOR REGIONAL SCRUB PRESERVE
ESTABLISHMENT). They should not be utilized as a
quantitative analysis or "habitat evaluation method"
per se, although they could serve as a starting reference
for construction and testing of such a method, in con-
junction with establishment of scrub preserves.
Final selection of preserve tracts is an unavoidably
subjective process. Thus, input from professional bio-
logists, affected governments, environmental and civic
organizations, and the public at large is crucial to the
selection process. Public workshops would be the most
appropriate forum for such input, with the final deci-
sion regarding preserve establishment resting with
county government.


SUMMARY


Despite the diversity of opinion on species-area re-
lationships, minimum viable population size, and the
relative value of large or small preserves, most
researchers agree that there is no simple solution or
universal best approach to the problem of nature pre-
serve design. Indeed, most researchers have concluded
that, while large preserves are essential to preservation
of some species, large or small preserves each may be





valuable, especially in context of a regional preserve
system (Terborgh 1974, 1976; Diamond 1976; For-
man et al. 1976; Galli et al. 1976; Simberloff and Abele
1976a,b; Whitcomb et al. 1976; Kitchener et al.
1980a,b, 1982; Wilcox 1980; Butcher et al. 1981;
Higgs 1981; Shaffer and Samson 1985; Soule and Sim-
berloff 1986; Miller et al. 1987). Higgs (1981:117)
aptly summarized the dilemma:

". . . theoretical and managerial considerations
give no clear decision as to the optimum strategy.
Predictions from the species-area relationships
depend upon the particular species involved and
on the scale of the proposed reserves. Other fac-
tors, namely the irreversibility of each strategy,
the effect of natural catastrophes, edge effects,
managerial considerations, and extinctions envis-
aged after the reserves are set up, are either poorly
supported empirically or again depend on partic-
ular circumstances and yield no clear, simple
empirical rules."

In the specific case of developing a scrub preserve
system, the discussions presented above lead to the
following general conclusions.

1. While many large refuges would be most
desirable, the most practical solution is to
maintain a core of relatively large (greater
than 500 acres) preserves, and establish as
many smaller refuges as possible to preserve
Endangered, potentially endangered, or
endemic species; samples of intact communi-
ties throughout the region; corridors or
"stepping stones" between relatively isolated
tracts; and genetic variation within scrub
species.

2. Minimum preserve size will vary extensively
with the species or community being pre-
served, down to a practical (for management
purposes) minimum of about 10-15 acres
for botanical preserves, 15-30 acres per terri-
tory for Florida scrub jay preserves, and 50
acres for scrub community preserves.

3. Management implications may be the most
important factor in determining both the
optimal size of a preserve and its probability
of success. Individual refuges should be
established based on the specific needs of the
taxa or community to be managed, as empha-
sized by Connor and McCoy (1979), Higgs
(1981), Simberloff and Abele (1976a,b;
1982), Weaver and Kellman (1981), and
McCoy (1982).

These minimum acreage thresholds for scrub pre-
serves are proposed with some hesitancy. There are few


published studies on species-area relationships, min-
imum viable populations, management techniques, or
minimum acreage requirements, which directly address
scrub communities or species. Any recommended
acreage, therefore, would be subject to debate. Based
on the best available information, however, these
guidelines are recommended unless detailed site-
specific information indicates otherwise. It is hoped
that these guidelines will be construed as impetus for
further research rather than as dogmatism.













SECTION 5.


CURRENT DISTRIBUTION AND ENDANGERMENT

OF SCRUB COMMUNITIES






METHODS


Distribution and condition of scrub habitats within
the study area were determined via interpretation of
published soil surveys (McCollum et al. 1978, Watts
and Stankey 1980, McCollum and Cruz 1981, Wett-
stein et al. 1987), literature review, and analysis of
false-color infared photographs (National High-
Altitude Photography [NHAP] 1984-1985), with sub-
sequent ground-truthing. Initially, all soils likely to
support scrub associations, as determined by soil and
community descriptions in the published soil surveys,
were delineated on copies of the soil maps at 1:20,000
scale. Next, the soil survey photographs and NHAP
aerials were examined to determine whether develop-
ment, agriculture, or mining activities had eliminated
the site's potential to support a scrub community. Field
surveys and limited aerial reconnaissance were then
conducted to determine on-site conditions. Nearly all
areas of scrub soil were field-truthed to determine site
conditions. Most unvisited scrubs consisted of small
(less than 5 acres) isolated sites which; (1) were near to
or surrounded by visited tracts likely to support similar
plant communities, and (2) were inaccessible without
inordinate delay. Time spent on a given site varied from
12 hour to several days, depending on the size and
apparent value of the tract. Field notes were recorded
on draft maps, and preliminary assessment codes were
assigned during these field surveys. Refinement of the
mapping process and code was a continuous process as
familiarity with scrub communities of the region
increased. Many sites were visited numerous times dur-
ing the study, to verify applicability of these code
refinements. The resulting maps were reconstructed
from field data and map interpretation.

Community Description Code

The scrub inventory includes a code comprised of
several elements which describe the site in terms of
community type, relative degree of disturbance, habitat
quality, and presence of certain species or ongoing
activities.

Vegetation - This element includes one or more designa-
tions. As previously discussed, the three scrub associa-
tions are scrubs (S), scrubby oak flatwoods (0), and
scrubby pine flatwoods (P). Pine flatwoods (F) are also
delineated, as are other xeric habitats (X). The X desig-
nation does not represent any single vegetative associa-
tion in these maps; rather, it serves to identify areas
which support relatively xeric communities which are
not "scrubs." Under more comprehensive mapping
procedures, these sites might be designated as coastal
hammock, sandhill, mixed upland forest, low ham-
mock, dry prairie, or a variety of other associations.
Thus, this designation should not be used to evaluate
distribution or abundance of any particular community.


Habitat area percentage - The second part of the code
consists of a single letter ranging from A to D, which
provides a rough estimate of the percentage of the tract
which has been disturbed to the point that it no longer
is considered an intact native community. A indicates
tracts of which less than 10 percent of the ground
surface has been disturbed by building construction,
paving, fill removal, land clearing, or other disturban-
ces which may preclude normal scrub regeneration. B
indicates that approximately 10 to 50 percent of the site
has suffered such disturbances. Scrubs which have been
altered by construction of a paved road network as a
precursor to development, and sites which consist of
improved campsites or other facilities within a scrub
community are examples of B tracts. C designates areas
where 50 to 90 percent of the ground surface has been
dramatically altered by such activities. This designation
is usually associated with ongoing construction or
completed development in residential or recreational
areas, where "green spaces" were left in native vegeta-
tion. Large tracts undergoing single-lot construction
where individual residential lots remain in native vege-
tation may be assigned this percentage code, as are
corridors along highways or railroads which are severely
fragmented by commercial development or other dis-
turbances. D represents tracts where over 90 percent of
the ground surface has been disturbed as described
above.

Habitat quality - The third component of the code indi-
cates subjective evaluation of the quality of habitat
remaining, exclusive of the non-habitat areas indicated
by the A-D code. A number ranging from i to 3 is used
to represent this evaluation. A i designates sites which
represent relatively undisturbed scrub habitats, though
nearly all scrubs in the region reflect past disturbances
such as timber harvest, land clearing, survey trails,
off-road vehicle use, limited sand excavation, invasion
of exotic species, unauthorized dumping, or distur-
bance of the natural fire regime. A 2 indicates sites
which exhibit moderate evidence of such disturbances,
and 3 reflects scrubs which are severely disturbed via
such actions. There is substantial overlap between these
designations.

Development codes - Two special indicators appear for
some tracts. The suffix U/C indicates tracts which are
currently under construction, either as a single devel-
opment project, or on a lot-by-lot basis. The suffix P/D
indicates tracts for which there are current develop-
ment plans, although no significant construction activ-
ity had occurred which would affect the remaining
portions of the site code.

Endangered, potentially endangered, or endemic species
-All observations of the vertebrates discussed in the
ENDANGERED, POTENTIALLY ENDANGERED,
OR ENDEMIC SPECIES section of this report were





mapped. Gopher tortoises, Florida scrub jays, and
scrub lizards are relatively easy to detect, at least during
certain seasons. Others including Florida mice, gopher
frogs, indigo snakes, pine snakes, and some Endangered
or Threatened plants normally require more intensive
searches than were conducted during this study. Sea-
sonal and daily variation in the activity or observability
of many species also affect the validity of making any
comparisons of species occurrence from these data.
The species indicator reveals the presence of the species
(or active burrows in the case of gopher tortoises) on
the site during field inspection. It provides no indica-
tion of species abundance or the presence of a viable
population, nor does lack of the species code assure
that the species does not occur on-site. Additional
occurrence records from Cox (1984, 1987), Enge et al.
(1986), and from unpublished data provided by the
Florida Natural Areas Inventory were reviewed, but
were not included unless species occurrence was veri-
fied during this study.

RESULTS

Because the scrub inventory exists primarily as a
computerized database and map system, and because
the detailed data are not important for most readers,
they are not included in this report. The figures and
tables are derived from the inventory to present salient


information. In discussions of "viable" scrub acreages,
only scrub habitats designated as A i, A2, Bi, or B2 are
included, since the other condition codes represent
tracts with little community preservation value. The
complete inventory is maintained by the Treasure
Coast Regional Planning Council and the Florida Game
and Fresh Water Fish Commission, and data are availa-
ble as needed.
This effort delineated approximately 64,670 acres of
potential scrub soils in coastal areas of the region,
including 40,545 acres of primary scrub soils, and
16,576 acres of secondary scrub soils (Figure 29, Table
7). Approximately 23,171 acres support scrub com-
munities (including mosaics of scrubs and non-scrub
habitats), of which 13,024 acres are in A i or A2 condi-
tion, and 16,004 acres satisfy the criteria for "viable"
scrub (A i, A2, Bi, or B2 condition). Approximately
5,331 acres of scrub and scrubby flatwoods occur
within Jonathan Dickinson State Park, Hobe Sound
National Wildlife Refuge, Savannahs State Preserve, or
the Loxahatchee Wild and Scenic River corridor.
Approximately 48,366 acres of identified potential
scrub soils wholly support non-scrub communities
such as xeric hammocks or pine flatwoods, have suf-
fered displacement of the native community by devel-
opment or agriculture, or have been disturbed to the
extent that they no longer represent a native scrub
community.


Table 7. Acreages of scrub soils and habitats in the study area.
Indian Saint Palm
River Lucie Martin Beach Total

Ridge soils 1,597 1,092 0 0 2,689
Primary soils 1,152 3,253 14,180 21,960 40,545
Secondary soils 3,241 288 6,637 6,410 16,576
Minor soils 2,056 2,422 380 0 4,858
Total potential soils 8,046 7,056 21,197 28,371 64,670


Existing preserves' 0 732 4,5933 6 5,331
Scrubs2 (AI-A2 condition) 2,709 1,148 7,4173 1,750 13,024
(excluding preserves) 2,709 416 2,824 1,744 7,693
Scrubs2 (Az, A2, Bi, B2) 3,263 2,184 8,2043 2,353 16,004
(excluding preserves) 3,263 1,452 3,611 2,347 10,673
Scrubs2 (all conditions) 4,708 4,350 10,6873 3,426 23,171
Developed lands, non-scrubs,
and scrubs in non-viable
condition 4,784 4,859 12,711 26,012 48,366
Total all habitats4 8,048 7,042 20,915 28,365 64,370

'Includes Jonathan Dickinson State Park, Hobe Sound National Wildlife Refuge, Savannahs State Preserve, and
the Loxahatchee Wild and Scenic River corridor.
2Includes tracts comprising mosaics of scrubs and non-scrub communities.
3Includes total acreage of potential scrub soils in Jonathan Dickinson State Park (3,935 acres). Actual scrub
acreage as mapped (Florida Department of Natural Resources, unpubl. data) is significantly lower.
4Acreage discrepancies between Total potential soils and Total all habitats are due to rounding errors and minor
digitizing errors. A '




















































APPROXIMATE SCALE
1" = 12.6 MILES


JUPITER

JUNO
BEACH





PALM
BEACH




BOYNTON
BEACH

DELRAY
BEACH


BOCA
RATON


Figure 29. Distribution of potential scrub soils in the coastal study area.






Indian River County

Scrub communities historically occurred along the
Atlantic Coastal Ridge, along the banks of the south
fork of the Sebastian River, and along the Ten Mile
Ridge (Figure 30). Approximately 8,046 acres of
potential scrub soils were identified, including 1,152
acres of primary scrub soils, and 3,241 acres of secon-
dary scrub soils (Table 7). Both the Atlantic Coastal
Ridge and the Ten Mile Ridge are primary highway,
railroad, or utility corridors. These impacts aside, resi-
dential and commercial development have displaced
most of the former scrub along the Atlantic Coastal
Ridge. Agriculture (primarily grazing and clearing for
pasture) has been the major disturbance factor along
the Ten Mile Ridge.
Approximately 3,263 acres currently support scrubs
and associated communities which satisfy the A 1-B2
condition criteria for "viable" scrub, with only 2,709
acres meeting the A i-A2 condition standards (Figure
31). There are about 1,500 acres of these habitats along
the Atlantic Coastal Ridge, all of which are considered
extremely vulnerable to development. Nine-hundred
acres occur along the south fork of the Sebastian River.
The 300 acres along the east bank are dominated by
xeric hammocks, and are undergoing sporadic devel-
opment. The 600-acre tract along the west bank is
likely to rapidly undergo development pressure if
highway access is provided: the southernmost parcel of
this tract is currently under development. Along the
Ten Mile Ridge, which also includes about 900 acres of
scrub communities, the extent of future development is
largely dependent upon desires of current landowners,
county land-use planning, and access to major highways.
There are no established scrub preserves in Indian
River County. Donald McDonald Park contains a sig-
nificant sand pine scrub tract which is developed as a
camping and picnic facility, and smaller publicly owned
scrubs occur on the Sebastian Municipal Airport site,
the Winter Beach landfill transfer station, the Sand
Ridge Golf Course, and other parcels. None of these,
however, is large enough to be considered for regional
preserve status. The only publicly owned tract which is
suitable for such designation is the Vero Beach Munici-
pal Airport property. Only one privately owned tract, a
Boy Scout camp (Camp Oklawaha) on the Sebastian
River, is considered to have any significant degree of
protection from immediate development.


Saint Lucie County

In Saint Lucie County, scrubs historically occurred
on the Atlantic Coastal Ridge and along the north fork
of the Saint Lucie River and its tributaries. The south-
ern extension of the Ten Mile Ridge into northern Saint
Lucie County possesses small tracts of secondary scrub
soils as well, but these all support pine flatwoods com-
munities, so they were not included in the inventory.


From the north county line southward to the Savan-
nahs State Preserve, scrubs along the Atlantic Coastal
Ridge are badly disturbed and fragmented, with virtu-
ally all tracts in Fort Pierce having been eliminated by
development. By far the largest nearly contiguous tract
of scrub in the county (732 acres) occurs along the
eastern fringes of the Savannahs State Preserve, though
sand mining, pineapple farming, and other historic dis-
turbances affect this area. Most scrubs along the north
fork of the Saint Lucie River and its tributaries (Ten-
mile Creek, SFWMD Canal C-24, Long Creek, Blakes-
lee Creek, Winters Creek, and Howard Creek) are
badly fragmented and are currently undergoing resi-
dential development.
Approximately 7,056 acres of potential scrub soils
were mapped, including 3,253 acres of primary scrub
soils, and 288 acres of secondary scrub soils (Table 7,
Figure 32). Approximately 1,148 acres of these soils
support scrub communities in A x-A2 condition, with
2,184 acres in the A r-B2 condition range (Figure 33).
Other than the Savannahs, which is the only publicly
owned scrub preserve in the county, there are few tracts
in public or private ownership which enjoy some
degree of protection, including Boy Scout camp Aba-
Lufa and the North Port Saint Lucie wastewater efflu-
ent irrigation site.

Martin County

Martin County possesses by far the greatest acreage
of scrub in the region. Approximately 21,197 acres of
scrub soils were delineated, including 14,180 acres of
primary scrub soils and 6,637 acres of secondary scrub
soils (Table 7, Figure 34). River drainages, topography,
and scrub distribution patterns in Martin County are
much more complex than in Indian River or Saint Lucie
counties. Scrub soils occur along several dominant
coastal ridges, occupying nearly all of the Sewall's Point
and Rocky Point peninsulas. They also occur along
many tributaries of the Saint Lucie River including the
North Fork and South Fork proper, Bessey Creek,
Poppleton Creek, Danforth Creek, Krueger Creek,
Willoughby Creek, Mapps Creek, Manatee Pocket and
Manatee Creek, Roebuck Creek, and numerous
unnamed branches. The corridor of the Loxahatchee
River and its tributaries also supports significant scrub,
scrubby flatwoods, and mixed forest communities.
Scrub formerly occurred along the Green Ridge as well,
but these soils are now devoted to agricultural uses.
Martin County includes two major scrub preserves:
Jonathan Dickinson State Park (including Boy Scout
Reservation Tanah-Keeta), and Hobe Sound National
Wildlife Refuge (including inholdings and proposed
acquisitions). In addition, the Savannahs State Preserve
extends 1 mile into northern Martin County, and
recently acquired portions of the Loxahatchee Wild
and Scenic River corridor lie immediately southwest of
Jonathan Dickinson State Park. Martin County por-
tions of these preserves include about 3,935 acres of










































S 4TH ST "


CR 606 OSLO RD 0_ �


















Figure 30. Distribution of potential scrub soils in Indian River County.








































\ 4TH ST G


CR 606 OSLO RD l'

















Figure 3 z. Remaining scrub tracts (A1-B2) in Indian River County.












L


FLORIDA
TURNPIKE \

ANGLE RD SR 607A


V
h -~r
V
~1'
V
C-'
V.


-a


SCALE 1" = 3 MILES





















I-k


Figure 32. Distribution of potential scrub soils in Saint Lucie County.











FLORIDA \
TURNPIKE
ANGLE RD SR\607A


V
V


V
.z.


4$
SCALE 1" = 3 MILES











7

^Y.-
V&


Figure 33. Remaining scrub tracts (A1-B2) in Saint Lucie County.


V









IA


SCALE 1" = 3 MILES


CR 714


BRIDGE RD CR 708


LOXAHATCHEE
RIVER


Figure 34. Distribution of potential scrub soils in Martin County.


,7
1\ *-








-V

0
m\0


SCALE 1" = 3 MILES


CR 714


0


$


5$1 __ BRIDGE RD CR 708 009












LOXAHATCHEE LP
RIVER















Figure 35. Remaining scrub tracts (A i-B2) in Martin County.


^--



























SR 786 PGA


SCALE 1" = 3 MILES


SR 704


MATCH LINE


Figure 36. Distribution of potential scrub soils in Palm Beach County.


-4
r

0
0


4






MATCH LINE


SCALE 1" = 3 MILES


LOXAHATCHEE
NATIONAL
WILDLIFE
REFUGE


HILLSBORO CANAL


Figure 36. Continued.



















SR 786 PGA


0
SCALE 1" = 3 MILES


SR 704


MATCH LINE


Figure 37. Remaining scrub tracts (A1-B2) in Palm Beach County.


O
\
0

































SCALE 1" = 3 MILES


LOXAHATCHEE
NATIONAL
WILDLIFE
REFUGE


MATCH LINE


SR 882


CANAL


Figure 37. Continued.






scrub soils in the state park, 300 acres in the wildlife
refuge, 350 acres in the Loxahatchee corridor outside
of the state park, and 8 acres in the Savannahs. Scrub
communities of Jonathan Dickinson State Park were
briefly field-truthed, but were not mapped in detail for
this inventory, because a thorough habitat map of the
park has recently been completed (Florida Department
of Natural Resources, unpubl. data). That map identi-
fies 2,355 acres of scrub and scrubby flatwoods in the
park, excluding the Boy Scout reservation (640 acres)
and Girl Scout camp (600 acres) (Dick Roberts, pers.
comm.). Except for the Savannahs, these preserves are
located in the southern third of the county. Smaller
publicly owned tracts include scrubs on the Witham
Field airport property, Tequesta Park, and other minor
parcels. The most significant privately owned scrub
with some degree of protection is the aforementioned
Boy Scout reservation.
Obviously, Martin County is well ahead of the rest of
the region with regard to scrub preservation. Unfortu-
nately, scrubs outside of the major preserves are suffer-
ing dramatic and increasing losses to residential devel-
opment. If scrub soils within the four major preserves
cited above are excluded (a total of 4,593 acres), there
remain only 3,611 acres of scrubs and scrubby flat-
woods in the county (Figure 35). Of this area, approx-
imately 2,824 acres are in the A x-A2 condition range.

Palm Beach County

This is the only county in the region for which a
historical analysis of scrub distribution exists (Richard-
son 1977). Scrub historically occurred along the Atlan-
tic Coastal Ridge in a rather complex series of parallel
ridges (Richardson 1977, Austin et al. 1987). Richard-
son (1977) stated that many coastal scrubs were cleared
for agriculture as early as the 1870's, and implied that
timber harvest was also a significant factor in natural
community decline by the turn of the century. Reanaly-
sis of those maps and current aerial photography indi-
cated that of 41,195 acres of scrub occurring about
1900, only 1,140 acres of sand pine scrub still existed
in 1984 (Treasure Coast Regional Planning Council
1987). This represents a 97 percent decrease in scrub
abundance.
This inventory revealed approximately 28,371 acres
of potential scrub soils in coastal Palm Beach County,
including 21,960 acres of primary scrub soils and
6,410 acres of secondary soils (Table 7, Figure 36).
Vast acreages of coastal Palm Beach County that histor-
ically supported scrub communities are no longer rec-
ognizable as scrub soils and are now designated as urban
lands or other unnatural substrates in the soil surveys.
Thus, these figures drastically underestimate the his-
toric abundance of scrub communities. Of the identifi-
able soils, however, only 2,353 acres currently support
scrubs or scrubby flatwoods in the A I-B2 condition
range, and only 1,750 acres meet the A i-A2 condition
criteria (Figure 37). Realization that some of these


tracts include mosaics of scrub and non-scrub com-
munities indicates that the 95+ percent loss of historic
scrub communities reported in the literature (based on
TCRPC analysis of Richardson's 1977 maps) is sub-
stantiated by the results of this inventory.
There are no major scrub preserves in Palm Beach
County, although minor tracts of scrub in the Loxahat-
chee Wild and Scenic River corridor extend into Palm
Beach County from Martin County. Existing publicly
owned tracts include the Jupiter Lighthouse Park,
Coast Guard Station, and missile data collection annex;
portions of the Tequesta wellfield site; Patch Reef Park;
Loggerhead Park; Rolling Green Scrub in Boynton
Beach (currently proposed for intensive development
as a recreational park); scrub remnants in the Radnor/
Diamondhead tract in Jupiter; the Bramalea tract (West
Camino Scrub) in Boca Raton; and other minor tracts.


INTERPRETATION OF SOIL
AND SCRUB DATA


A number of factors should be considered when
attempting quantitative comparisons between current
and past scrub distribution. (1) Large tracts of parents,
quartzipsamments, "pits," "urban land," and other
manmade landscapes or "soils" occur where develop-
ment has dominated recent land use. Along the coastal
ridges many of these tracts would have historically
supported scrub communities. Because the primary
intent of this project was to document existing resour-
ces and prepare guidelines for their protection and
management, it was not practical to pursue detailed
reconstruction of the historical scrub distribution in
the study area. Deletion of these areas from potential
scrub soil acreages results in inflated estimates of the
percentage of scrub remaining, compared to historical
abundance. The amount of inflation, of course, is
directly related to the extent of such urban lands. (2)
Many of the tracts identified in this study are mosaics of
pine flatwoods, scrubs, xeric hammocks, sandhills, and
other communities. As a result, acreage figures may be
significantly greater than actual acreage of "pure" scrub
communities. (3) The correlation between soil and
habitat type is not perfect. As described above, several
different communities may occur on any soil type. The
field truthing and community description code elimi-
nate most of these aberrations, but caution should be
excercised in compiling quantitative data from these
maps. (4) The soil maps are considered extremely reli-
able for construction of this inventory, but they do not
depict inclusions of other soil types which were too
small to be mapped. (5) Scrub community borders may
not perfectly coincide with the mapped soil units. Such
deviations could easily mask the quantitative impor-
tance of numerous, small scrub patches distributed
throughout the region. (6) This inventory represents
only one moment in time. Many scrub tracts are in





process of being displaced by development, and the
condition of any given tract may change virtually
overnight.
Because of dramatic changes which occur naturally
during scrub succession, and observed trends in species
diversity encountered from north to south and east to
west in the region (Austin et al. 1987), the code is best
utilized to compare sites which are relatively near one
another. It would not be appropriate, for example, to
infer that an A i scrub in northern Indian River County
would be equivalent to an A i scrub in Palm Beach or
southern Martin counties. Also, various sites were
visited during different seasons, dramatically affecting
the observability of some plant or animal species during
the relatively brief site visits. The code is intended to be
a guide to potential value of scrub tracts for preserve
establishment or other protective measures, rather than
a comparative evaluation of scrub communities
throughout the region.


DISCUSSION


Historically, scrubs formed a virtually continuous
zone along the Atlantic Coastal Ridge throughout the
region. As land development proceeded, this habitat
was radically fragmented such that these communities
now exist as islands surrounded by developed or dis-
turbed lands. The only major scrub preserves in the
Treasure Coast Region include Jonathan Dickinson
State Park, Hobe Sound National Wildlife Refuge,
Savannahs State Preserve, and the Loxahatchee Wild
and Scenic River corridor (portions of which are within
the aforementioned state park). Other remnant scrubs
include undeveloped tracts along the Atlantic Coastal
Ridge and river corridors; publicly owned recreational
parks, wellfields, airports, or other facilities; small
tracts in utility or transportation rights-of-way; vestiges
of the native community left as "natural areas" within
major residential developments; and smaller knolls or
ridges in broad flatwoods. Along the Atlantic Coastal
Ridge, nearly all of the remaining significant scrub
tracts are currently proposed for development, or are
for sale.
Richardson (1977:289,294) stated that large-scale
disruption of the environment by modern man began as
early as 1900 in Palm Beach County, involving such
impacts as drainage, lumbering, increased urban sprawl,
agriculture, and increased fires. Excerpts from his
assessment include:

"The southern Florida ecosystem is unique from
the standpoint that it received very little attention
until the late 1800's. Prior to the coming of the
Europeans, about the only artificial stress placed
on the vegetation was the burning practices of the
Indian tribes.... Early settlement in Palm Beach
County began during the 1860's in the West


Palm Beach area. The first thought at that time
was to drain the low lying areas so that the land
could be used for agricultural crops. Much of the
sand hill country was already flourishing with
pineapple fields in the late 1800's."

and;

"Many of the coastal scrub ridges were cleared
for agriculture in the 1870's and no longer show
direct signs of lumbering due to urbanization of
these areas.... By 1895 the Florida [East] Coast
Railroad, under the direction of Henry Flagler,
had begun surveys for an extension of the tracks
to West Palm Beach. In April, 1896, the road was
completed to Miami and Flagler's trains were
causing a rapid depletion of the timber supply."

As explained above and in the ECOLOGY: Human
Impacts discussion of this report, human activities are
responsible for virtually all of the existing threat to
these natural communities, with land development
exerting the most unrelenting pressure. Treasure Coast
scrubs are especially valuable as development sites.
Because they occupy the highest coastal ridges, railroad
and highway construction historically occurred first in
these communities, predisposing them to subsequent
development. Also, they offer tremendous develop-
ment potential since flooding is not a significant threat
and landfilling is unnecessary.
Another problem in maintaining these communities
is their insular nature. Historically, the continuity of
scrubs along the Atlantic Coastal Ridge facilitated long-
term preservation of the fauna, with extirpated popula-
tions being replaced via immigration from adjacent
scrubs. Decades of development have since fragmented
this corridor such that isolated populations of endan-
gered or endemic species are much less likely to be
replaced once extirpated.
Over 50 years ago, Webber (1935) stated that the
native Florida scrub community was in danger of
extinction as the result of human impacts. This study
emphasizes the scarcity of intact scrub communities,
existence of only four major preserves in the entire
region which include significant scrub acreage, and
impending development plans for many remaining
scrub tracts. In light of these threats, the statement by
Mulvania (1931) that, "economically, the plants, as
well as the soil, have almost no importance," is espe-
cially ironic. Indeed, it has been the economic value of
these sites for agricultural and residential development
which has rendered scrub habitats so critically endan-
gered in the Treasure Coast Region. There clearly is an
urgent need to implement a comprehensive regional
program of scrub preservation and management.

































































78















SECTION 6.


PRESERVATION, RESTORATION, AND
MANAGEMENT OF COASTAL SCRUBS





There are two potential approaches to preserving
scrub communities in the Treasure Coast Region. The
first is to further restrict development on each parcel of
land that supports scrub to preserve a percentage of
remaining scrub habitats or species populations. While
this may result in greater species and habitat preserva-
tion than currently exists, such a piecemeal approach to
habitat preservation, coupled with benign neglect
resulting from lack of habitat management programs,
would not prevent loss of valuable scrub habitats, con-
tinued degradation of scrubs which were "preserved,"
and local or regional extirpation of Endangered, poten-
tially endangered, or endemic species. Another draw-
back of this approach is that the entire burden of estab-
lishing and managing preserves would be borne by
landowners of the respective tracts. Furthermore, the
absence of regional perspective regarding scrub preser-
vation and management would render the entire pro-
cess less efficient.
Therefore, another scenario is recommended as the
most appropriate means of preserving these resources.
This proposal involves development of a regional pre-
serve system whereby reserves or corridors may be
established to protect selected habitats or taxa. Less
valuable, or less easily acquired tracts, would be com-
mitted to development after implementation of appro-
priate mitigation. This Regional Scrub Preserve System
would be supported by a comprehensive scrub manage-
ment policy and program, and by long-term monitoring
efforts.


A REGIONAL SCRUB
PRESERVE SYSTEM


The process of designing and implementing a
regional preserve system is fraught with pitfalls and
opportunities for counterproductive debate. As stated
by Higgs (1981) and reiterated by Richardson et al.
(1986), "The design of nature preserves, whether in
isolated or remote areas within undeveloped countries
or in urbanized settings within metropolitan areas, is
not yet an empirical science (Higgs 1981)... Existing
preserves regardless of size are often determined
because of economic and political realities, rather than
because of biological considerations."
The need for review of southeast Florida scrub biol-
ogy, biogeography, and potential preservation or man-
agement strategies has become widely recognized in
recent years. For example, Richardson et al. (1986)
recently summarized the theories of island biogeo-
graphy and nature preserve establishment; reviewed
literature pertinent to scrub habitats and selected
potentially endangered or endemic species found in
scrubs of southeast and east-central Florida; outlined
the origin, ecology, and peculiarities of scrub habitats;
and provided recommendations for establishment and
management of a scrub preserve. Though their report


was oriented toward study of a particular tract of scrub
in Palm Beach County (Yamato Scrub), their recom-
mendations for establishment and management of a
scrub community preserve, viewed in context of the
need for preservation of potentially endangered or
endemic species found in east-central Florida, were
without precedent.
Unfortunately, the scientific literature remains
inadequate to provide a suitable foundation for a scrub
preserve system. The extreme vulnerability of scrub
habitats, however, and their alarming scarcity com-
pared to historical abundance, permit no delay in the
implementation of such a program. We must act
quickly and conservatively to establish a system which
will safeguard those tracts and natural values we cur-
rently recognize, while providing a flexible framework
for incorporation of future preserve selection criteria
and management options.
The proposed Regional Scrub Preserve System is
designed as a three-phase program including: (1) a sys-
tem of Regional Scrub Preserves; (2) a network of mini-
preserves, rights-of-way, wildlife travel corridors, and
other minor scrub tracts; and (3) a comprehensive
management program including prescribed burning,
mechanical habitat renovation, species and habitat
monitoring and research, habitat restoration, and spe-
cies relocation where appropriate.
To be effective, the Regional Scrub Preserve System
must reflect unified commitment to a comprehensive
program of long-term habitat preservation and man-
agement. Therefore, the entire system must possess
several essential features: (1) each preserve must be
large enough to support viable scrub communities or
populations of the criteria species; (2) each tract must
be under public management authority, or under pri-
vate control which ensures its preservation through
conservation easements or management agreements
with state, regional, or local government; (3) each par-
cel's location and surroundings must facilitate long-
term management via prescribed burning or mechani-
cal renovation; and, (4) an adequately funded and
authorized management program must be established
for each tract.

Government Authority and Responsibilities

The regional planning council would maintain a
regional perspective on the entire preserve system to
advise the counties regarding the current status of
major scrub resources throughout the region. The
regional planning council staff primarily would be
involved in assisting with purchase or preservation of
these tracts if requested by local government; oversee-
ing management and restoration activities on each tract;
and maintaining computerized maps, databases, and
management records for each preserve in the system.
Recommending or contracting for research, restora-
tion, and monitoring efforts of regional importance
would also be a function of the regional planning coun-





cil. Logistical support of the Regional Scrub Management
Team and the Regional Scrub Acquisition Team (dis-
cussed under GUIDELINE IMPLEMENTATION)
would be provided by the council.
Selection of tracts for inclusion in the preserve sys-
tem, obtaining adequate funds for their acquisition and
management, and implementing a management plan for
each preserve will constitute the most significant duties
of local governments. To avoid confusion and conflict-
ing authority between local governments, and to max-
imize efficiency within the program, municipalities
should pool their local funds and authority over the
scrub preserve system, and vest this responsibility in
county government. This would provide county-wide
consideration of appropriate preserve sites and man-
agement issues without excessively infringing on local
government control over these natural resources which
transcend local importance.



Scrub Preserve Classification

Several types of scrub preserves would be differen-
tiated. Community designations include scrub, scrubby
oak flatwoods, and scrubby pine flatwoods; though in
all likelihood, each of these community types may be
represented in a single preserve. Other categories
include preserves which are established to protect par-
ticular Endangered, potentially endangered, or endemic
species.
Another delineator would be the ownership status of
a preserve. Publicly owned tracts are most desirable,
and should receive priority in management decisions.
Deed-restricted or privately owned tracts under an
approved management agreement are of secondary
priority, and other privately owned tracts are of lowest
priority. While this approach may seem to pay least
attention to the most threatened tracts, it would ensure
that the public's money and energy are spent in the
most efficient manner (i.e., on preserves which are
assured of continuing preservation and management).
Preserves would be considered natural areas if there is
no current human habitation (other than a designated
caretaker), or agricultural, mining, industrial, recrea-
tional, commercial or other development on the parcel.
Presence of railroads, powerlines, or occasional roads
would not necessarily eliminate a tract from considera-
tion as a natural area. Recreational preserves would
include those with picnic areas, other recreational facil-
ities, off-road vehicle use (if appropriate), or unlimited
public use. Mixed-use preserves would include non-
recreational uses that are precluded from natural area
preserves.
Each preserve's classification would indicate its nat-
ural communities, purpose, and ownership. Thus, clas-
sification will facilitate regional coordination of pre-
serve establishment for protection of particular scrub
resources.


Scrub Preserve Acquisition

The greatest cost associated with implementation of
these recommendations will be purchase or leasing of
Regional Scrub Preserve tracts. There are several
potential methods of acquiring valuable sites including
bond issues, state or federal recreational and environ-
mental land funds or grants, tax incentives for private
land included in preserves, or even donation of tracts
by large landowners or corporations. Funds derived
from Developments of Regional Impact through mit-
igation plans, local option taxes, impact fees designated
for environmental uses, or fines associated with illegal
activities which affect the environment could be util-
ized for acquisition, management, and research activi-
ties. Finally, transfer of development rights to sites
possessing low natural resource value, and direct
exchange of land parcels are additional methods of
acquiring particularly valuable preserve tracts.
Easements or setbacks associated with local devel-
opment and zoning ordinances, transfer of develop-
ment rights, native landscaping requirements, and pro-
vision of "green spaces" are potential means of securing
scrub habitat protection for minipreserves and wildlife
travel corridors.
Several Florida counties (e.g., Alachua, Brevard,
Indian River, Martin, Monroe) have established funds
for various environmental purposes, or have contrib-
uted financially to acquisition of endangered lands. A
leader in this regard, Volusia County passed a $20
million dollar bond issue for this purpose. An ongoing
study funded in part by the Florida Game and Fresh
Water Fish Commission, the Treasure Coast Regional
Planning Council, and the Northeast Florida Regional
Planning Council is addressing use of impact fees and
negotiated settlements to acquire natural upland areas
(Florida Atlantic University / Florida International
University 1988). Many of the issues being addressed
in that study are central to establishment of a Regional
Scrub Preserve System, and the final report should
prove invaluable to implementation of these guidelines.
Mitigation banking could be a significant tool in
providing sites and funds for scrub preservation and
management. An experimental mitigation bank (Wild-
life Resources Mitigation Fund) is currently under
development within the Northeast Florida Regional
Planning Council (Allen 1987) as the result of unper-
mitted taking of an Endangered species on a Develop-
ment of Regional Impact site. Similar mitigation bank-
ing has been successful in California (Martin 1986).
These efforts could provide valuable insight regarding
the establishment of such funds within the Treasure
Coast Region. Several options for utilization of a mit-
igation bank to acquire scrub preserves are identified as
follows:

1. A major developer or a unified group of land
users with common interest, such as sand min-
ers or residential developers, could pool their





resources and purchase or set aside tracts of
scrub habitat as preserves to be immediately
included in the regional system. The acreage or
environmental value of these lands could then
be utilized as a mitigation bank account, which
would gradually be amortized through the mit-
igation requirements of subsequent projects.

2. A valuable scrub tract could be identified as a
specific target for mitigation funds. Impact
fees could then be assessed on local developers
to pay for gradual purchase of the target prop-
erty. Conservation easements, purchase by a
public land trust, or options to purchase could
prevent development until sufficient funds
accrued to purchase the property.

3. Preserve lands could be purchased via bond
issue or by a third party (e.g., The Nature
Conservancy, Trust for Public Lands) and
subsequently acquired by the Regional Scrub
Preserve System as mitigation funds became
available.

4. Each county government could establish a mit-
igation fund, not necessarily targeted at a spe-
cific project, which would receive fines, dona-
tions, or mitigation payments, and provide a
long-term land acquisition and management
fund for the scrub preserve system.

Scrub Preserve Management

The following management options can be imple-
mented as necessary within scrub habitats to maintain a
desired vegetative stage, reduce environmental pollu-
tion or soil erosion, or increase habitat diversity and
interspersion.

Prescribed burning - As discussed in the ECOLOGY
section of this report, fire is an essential part of long-
term scrub management and protection. Scrub and
scrubby flatwoods habitats can be rejuvenated and
managed by periodic burning. Also, by eliminating
hazardous fuel loads, prescribed burning can diminish
the threat of catastrophic wildfire, and reduce the like-
lihood of a fire spreading to adjacent areas. Unfortu-
nately, prescribed burning methodologies and fire
ecology models for scrub communities are in their
infancy (Richardson et al. 1986, Doren et al. 1987).
Pioneering efforts in the use of fire to manage scrub
habitats appear to have been largely successful to date,
but there is insufficient experience with prescribed
burns on scrub habitats to establish a set of guidelines
which could be safely implemented by non-experts.
Temperature, humidity, fuel abundance and moisture,
and windspeed interact to determine whether a scrub
will burn at all, and whether the resulting fire will be
controllable. These interactions are so complex as to


relegate prescribed burning of scrub habitats to expe-
rienced personnel, particularly where smoke and/or
wildfire spread to adjacent areas are of significant con-
cern. Nonetheless, continued research and experimen-
tal prescribed burns are essential if a long-term scrub
preserve system is to be implemented. The Regional
Scrub Management Team, and especially those persons
who have participated in prescribed burns of scrub
habitats, would be indispensable to establishment of a
program of prescribed burns for the regional preserves.


Mechanical ground cover renovation - Where burning
programs are impractical or would threaten private
property, mechanical means may be preferred. Roller
choppers, web plows, or bar cutters can be utilized in
scrubs to reduce vegetative height or density, control
pest species, stimulate seed production or germination,
remove ground litter, recycle nutrients, or set natural
succession back to a more desirable stage. In most
cases, however, mechanical ground cover renovation
would be most desirable as a precursor to prescribed
burning, rather than as a separate management tool.
Mechanical renovation has not been demonstrated to
be a satisfactory primary tool for scrub community
management without associated prescribed burning,
and it may result in greater losses of wildlife (Tanner
and Terry 1981, Cox et al. 1987) or loss of habitat
heterogeneity through disturbance of naturally occur-
ring topographic and floristic variation. Web plowing
and roller chopping resulted in significant disturbance
or destruction of gopher tortoise burrows in south
Florida (Tanner and Terry 1981, Diemer and Moler
1982), although there is evidence that tortoises may
escape unharmed from these damaged burrows (Die-
mer and Moler 1982, Cox et al. 1987). Mechanical
renovation may be particularly useful in managing
scrub tracts for Florida scrub jays, gopher tortoises,
and other species characteristic of early successional
scrubs (Breininger et al. 1986).

Landscaping with native species - Being adapted to the
climate and biological environment of their natural
habitat, native species usually provide better wildlife
habitat while requiring less irrigation, fertilization, pes-
ticide treatment, and general maintenance than intro-
duced plants, especially in a harsh, xeric environment
such as a scrub community. Certain exotic species, such
as Australian pine, Brazilian pepper, natal grass, and
cypress pine may displace native species or pose other
threats to native communities, though most exotics
readily invade scrubs only following significant habitat
disturbance (Austin et al. 1987).

Practicing minimal landscape maintenance - Less-intensive
maintenance can improve habitat conditions of rights-
of-way, parks, vacant lots, and other open spaces main-
tained as scrub remnants. Less frequent mowing, trim-
ming, watering, fertilizing, and pesticide application





will also reduce environmental pollution, demand for
water and other natural resources, and maintenance
costs.

Supplemental food or habitat - Food plots, hedgerows,
feeding devices, tree or shrubbery planting, nesting
boxes, dusting or watering areas, "starter burrows"
(Lohoefener and Lohmeier 1986, Cox et al. 1987), and
other habitat deficiency enhancement measures may be
helpful on given tracts. The habits and needs of target
species must be thoroughly studied, however, because
supplements will be beneficial only if they address the
appropriate limiting factor.

Restoration of previously impacted areas - Scrubs which
have been seriously impacted by human activities such
as timber clearing, unnatural fire regimes, off-road veh-
icle use, land clearing, or mining activities may be res-
tored to provide valuable wildlife habitat. Though the
technology to restore entire scrub communities has not
been demonstrated, establishment of several character-
istic species such as sand pine, rosemary, prickly-pear,
and xeric oaks is possible. Furthermore, research on
establishing other native scrub species on disturbed
sites is being conducted (Ecolmpact, Inc. 1981; Gilbert
1987). Provision of an appropriate hydrological regime,
recontouring of the land surface, physical or chemical
treatment of soil or substrate, and removal of exotic
vegetation may all be necessary before planting, seed-
ing, mulching, or otherwise attempting to reestablish
native communities. On severely altered soils, the sur-
face may require substantial aging or leaching prior to
further restoration. Habitat diversity; self-maintaining
native communities; establishment of new populations
of Endangered, potentially endangered, or endemic spe-
des; and protection from future adverse development impacts
should be the goals of scrub restoration programs.

Species relocation - In recent years, developers have often
sought to relocate wildlife species which interfered with
development plans. Relocation of gopher tortoises has
been a particularly popular "mitigation" activity, and
would likely be considered as a means of restocking
potential preserve sites. Several papers (Diemer
1984a,b; Florida Game and Fresh Water Fish Commis-
sion 1984) have discussed potential problems asso-
ciated with species relocation, including spread of dis-
ease and parasites, disturbance of locally adapted gene
complexes, and disruption of social structure. Guide-
lines for relocation of gopher tortoises have been deve-
loped (Florida Game and Fresh Water Fish Commis-
sion 1988), and similar procedures and precautions
should be exercised where relocation of other scrub
species may be warranted.

Research and Monitoring

Many facets of scrub community or species ecology
are poorly understood. Research opportunities should


be pursued to increase our understanding of scrub
communities and to provide critical information on the
biology of species that are being preserved. In addition,
monitoring of endemic or endangered species popula-
tions is an essential component of an integrated pre-
serve management program (White and Bratton 1980,
Hinds 1984, Graves and Dittberner 1986). A signifi-
cant portion of funds raised for preserve system man-
agement should be committed to research through
grants to scientists representing area colleges, universi-
ties, and other well-established research agencies. The
following topics are particularly worthy of additional
research:

(1) distribution and abundance of Endangered,
potentially endangered, or endemic species;

(2) autecological studies of these species;

(3) synecology of scrub habitats;

(4) population genetics of Endangered, potentially
endangered, or endemic species;

(5) long-term monitoring of known Endangered,
potentially endangered, or endemic species
populations;

(6) long-term monitoring of species distribution
and abundance in established preserves;

(7) changes in community structure resulting from
management efforts and natural disturbances
such as wildfire, and from land-use changes on
surrounding lands;

(8) prescribed burning and mechanical means of
scrub habitat management;

(9) restoration of scrub habitats on disturbed
lands; and,

(10) development of a comprehensive scrub habitat
assessment method which would provide qual-
itative and quantitative evaluation of specific
scrub tracts.


OTHER PROGRAMS FOR
SCRUB COMMUNITY
CONSERVATION

Careful planning, conscientious standards, and an
effective management program can ensure preservation
of the Treasure Coast Region's native scrub communi-
ties for future generations. A sophisticated environ-
mental review program may exceed the capabilities of
some Treasure Coast counties, but local governments





are often capable of upgrading their environmental
authority and ability. Cooperation between regulatory
agencies, planners, developers, and the general public is
critical to achievement of long-term scrub preserva-
tion. Because they require mass participation, efficient
operation, and adequate funding, many conservation
practices are best implemented by local government.
These same programs, however, could be effective if
undertaken by individuals, citizen groups, or local
developers. A united concern can be implemented
through synergistic efforts including government plan-
ning and policy, effective land-use and habitat protec-
tion ordinances, community conservation programs,
and public environmental education.
The following paragraphs include issues and options
which could be addressed to protect and restore coastal
scrub habitat. Many of these are currently in effect in
various jurisdictions of the region. For more discussion
of these potential programs see Leedy et al. (1978).

Government Planning and Policy

Regional and local governments bear primary respon-
sibility for upland habitat preservation. Thus, natural
resource preservation needs'must be thoroughly con-
sidered in government policy and planning activities.
Specific areas of greatest impact upon scrub habitats
include the following.

Comprehensive land use planning - Preservation and
management of natural resources is an important com-
ponent of local government comprehensive plans which
are mandated by state law. Policies and recommenda-
tions of the Florida Game and Fresh Water Fish Com-
mission are available to guide development and imple-
mentation of these comprehensive plans (Florida Game
and Fresh Water Fish Commission 1987). A thorough
plan can direct growth to maximize land use efficiency
and minimize disturbance of sensitive habitats and spe-
cies. A comprehensive plan is necessary for zoning
ordinances to be equitably and wisely implemented.

Professional environmental planning - County or city
planning departments often have urban planners, traf-
fic engineers, landscape specialists, environmental
planners, and other critical personnel on their staff, but
a professional ecologist is less common in such depart-
ments. If local governments are to assume an active role
in resource management, they must have accurate, pro-
fessional input on development impacts. State and fed-
eral agencies often lack the manpower or jurisdiction to
address environmental issues of local significance.

Site planning - Site planning to eliminate or minimize
adverse impacts to scrub habitats and to incorporate
essential features of an upland tract into development
plans can greatly enhance the wildlife habitat value of
virtually any developed tract. Selective cutting and
clearing of native vegetation can retain much of the


Figure 38. Effective (top) and insignificant (bottom) use
of native vegetation in home landscaping.

natural beauty and benefits of an area while reducing
landscaping and maintenance costs (Figure 38). Partic-
ularly sensitive parcels can be incorporated into buffer
zones around wetlands or lakes; into windbreaks, hedge-
rows, "green spaces," or wildlife travel lanes in agricul-
tural or residential areas; or into roughs and out-of-
bounds areas on golf courses and other recreational
lands. Construction of multifamily housing with undis-
turbed open spaces, rather than single-family housing,
conserves native habitats. Similarly, locating less-
intensive uses, such as golf courses or adult housing
rather than family housing or children's playgrounds,
near scrub preserves can reduce disturbance to sensi-
tive wildlife and plant species. Providing habitat con-
tinuity via hedgerows or "green spaces" will enhance
the wildlife values of parks, vacant lots, and other
vegetated tracts. Land contouring, landscaping, and
stormwater runoff systems should be designed to min-
imize erosion from scrub remnants.

Mitigation for environmental impacts - Development of
many scrub tracts will involve unavoidable adverse
environmental impacts. If destruction or disturbance
of valuable tracts is inevitable, mitigation in the form of
habitat preservation, compensation for unavoidable





habitat disturbance, or reduction of adverse impacts
through site planning efforts should be pursued. Avoid-
ance of adverse environmental impacts through effi-
cient site planning, however, is generally less expensive
and more environmentally acceptable than large-scale
mitigation.
Developments of Regional Impact or projects involv-
ing significant scrub resources require special site plan-
ning considerations. Loss of intact scrub communities
is never desirable, but may be acceptable if mitigatory
measures are sufficient to ensure preservation and
management of other scrub communities of equal or
greater value. When reviewing site plans for a scrub
tract, local ordinances and normal site planning as dis-
cussed in this chapter should be utilized to establish
minipreserves or to maintain "green spaces," wildlife
travel corridors, and rights-of-way as scrub habitats.
This process, however, should be considered separately
from mitigation undertaken to compensate for losses of
regionally important scrub resources.
Accordingly, on-site mitigation for loss of regionally
significant scrub resources should be sought only if a
unique and preservable resource occurs on site (i.e., a
potential Regional Scrub Preserve or a manageable and
viable population of an Endangered or potentially
endangered species). Otherwise, mitigation should
consist of: (1) a financial contribution to the mitigation
bank, the size of the contribution being sufficient to
acquire an equivalent area of valuable scrub, or (2) a
donation of other scrub habitat as part of a new or
existing Regional Scrub Preserve. Financial contribu-
tions alone should not be permitted until target scrub
tracts are identified and protected from development
via purchase option or written agreement. Failure to
meet this requirement may result in a large mitigation
fund but no habitat available for purchase.

Transfer of development rights - Transfer of development
rights from scrub habitats to less critical areas, and
increasing residential densities on one tract in exchange
for preservation of another, are means of protecting
scrub habitats without unreasonably restricting use of
private property.

Tax incentives - Tax credits or adjustments can be util-
ized to encourage private landowners and developers to
enhance wildlife values on their property. They can be
offered as inducement for native tree planting, removal
of exotic or pest species, food plot establishment, res-
toration of disturbed habits, creation of scrub pre-
serves, and numerous other habitat enhancement
options.

Local Ordinances

The following is a list of ordinances that local
government can adopt to protect scrub habitats from
inappropriate disturbances.


Zoning ordinances - Zoning regulations are a direct
means of controlling local growth and land use. Zoning
can direct development in accordance with compre-
hensive plans by identifying scrub habitats to be pre-
served or developed with restrictions. Development of
protective zoning overlays is the most effective use of
zoning to prevent cumulative losses of valuable scrub
resources.

Land clearing ordinance - Requiring site plan approval
prior to land clearing or tree removal operations can
provide greater control over imprudent or unnecessary
habitat destruction.

Sand mining ordinance - Significant mining or on-site
relocation of sand should be discouraged in coastal
scrubs because of the critical importance of these areas
to recharge of the shallow aquifer, and their value as
wildlife habitat. Ordinances should be adopted to regu-
late sand mining activities.

Native landscaping ordinance - As discussed under man-
agement options, landscaping with native species can be
a valuable part of any native habitat protection pro-
gram. Ordinances requiring native species to be utilized
in any "green spaces," buffer zones, wildlife corridors,
or open space areas can increase the value of these tracts
to native wildlife. Exotic plant species which are sus-
pected of being detrimental to the native community by
competing with or supplanting native species, or by
providing preferred habitat for exotic fauna, should be
prohibited.

Off-road vehicle regulations - Restricting use of off-road
vehicles to relatively insensitive habitats and estab-
lished recreational trails can reduce impacts on scrub
flora and fauna.

Domestic animal control - Strictly enforced leash laws,
mandatory sterilization of free-roaming pets, public
programs providing inexpensive sterilization of pets,
restricting pets from scrub habitats, and feral animal
control can reduce domestic animal predation upon, or
competition with, native species.

Litter-disposal ordinance - Although nearly all local
governments have ordinances prohibiting littering or
unauthorized dumping, such laws are often ineffective
because of insignificant penalties or lax enforcement.
As discussed, unauthorized dumping is a significant
problem in many scrub tracts in the region, causing
aesthetic and environmental degradation of the native
community. Strict enforcement and environmental
education are necessary to prevent this form of habitat
degradation.

Tree ordinance - Restricting removal or severe trimming
of valued species can help preserve individual speci-
mens or tracts of ecological importance.





Community Conservation Programs


The following is a brief list of activities that local
governments or conservation organizations could pur-
sue to enhance and protect scrub resources within local
jurisdiction.

Public land management - Rather than maintaining
parks, rights-of-way, building landscapes, and undeve-
loped lands in a manicured "park-like" condition, such
areas could be effectively managed by utilizing less
intensive horticulture and emphasizing maintenance of
native communities.

Posting of wildlife crossings - In conjunction with speed
reduction, posting of wildlife crossings could reduce
wildlife road kills, and personal injury and property
losses associated with such accidents.

"Champion tree" program - Official recognition of the
largest tree of a given species within a county or other
region can increase public pride in the area's natural
resources, and encourage preservation of trees or habi-
tats which may otherwise be disturbed.


Most people who are unappreciative of natural
resources simply never have been properly exposed to
them, or they believe that conservation practices are
always costly and inefficient operations in conflict with
a progressive society. Informing the general public of
the economic and aesthetic benefits provided by natu-
ral resources can promote greater civic responsibility,
ecological awareness, and respect for natural heritage.
Primary avenues of increasing public consciousness
regarding the plight of scrub communities include
expanded environmental education curricula in public
and private schools; adult education films and media
presentations; and public involvement through partici-
pation in local political campaigns, public hearings, and
media events.


Environmental Education













SECTION 7.

RECOMMENDATIONS FOR IMPLEMENTATION OF

A REGIONAL SCRUB PRESERVE SYSTEM






POTENTIAL SITES FOR SCRUB
PRESERVE ESTABLISHMENT

Criteria for selection of Regional Scrub Preserves
already have been discussed. The following sites are
recommended as potential scrub community preserves,
minipreserves, suburban Florida scrub jay sanctuaries,
or golf course recreational preserves. Local government
policy and planning, public opinion, and landowner
consent will determine which sites, if any, are selected,
but these tracts should be seriously considered for
preservation and management. The following discus-
sions do not imply that other tracts offer no value as
scrub preserves. It is not practical, however, to review
in this report every scrub tract in each county which
offers some potential for management. Therefore, only
the most outstanding tracts in each county are dis-
cussed, bearing in mind the goal of distributing pre-
serves throughout the region.
Generally, only areas designated A i or A2 were con-
sidered for selection as community preserves. Some B
or C areas may offer preserve potential if the disturban-
ces reflect past land uses which can be incorporated
into site plans for a recreational or suburban preserve.
For example, an abandoned road system could be util-
ized for picnic ground access, patches of scrub could be
preserved in a golf course, or disturbed portions of a
tract could be used for construction of recreational,
educational, or water treatment facilities. Few C tracts
include unaltered areas greater than a few acres, how-
ever, so they have comparatively little potential as
community preserves without significant restoration.
Finally, D tracts offer no value as community preserves.
Their only resources consist of undeveloped lots, land-
scape buffers, and utility or highway easements. Even
these areas, however, may provide wildlife travel lanes
or isolated habitat for remnant populations of scrub
species with minimal habitat requirements. Note that
acreages provided refer to the area of viable native communi-
ties on mapped scrub soils, not to the total acreage of the
recommended preserve site inclusive of non-scrub soils.

Indian River County

Regional Scrub Preserves should be established in
the northern, central, and southern portions of the
county (Figure 39). Because they are the best and most
threatened examples of scrub, tracts along the Atlantic
Coastal Ridge should receive highest priority.

North county - The preferred tract (IR- , 193 acres) is a
mosaic of sand pine scrub, scrubby pine flatwoods,
scrubby oak flatwoods, depression marshes, and ponds
between US 1 and the Sebastian Municipal Airport,
just north of Main Street. This tract is far larger than
other scrubs in the north county area, and its diversity
of scrub and non-scrub communities increases its over-
all preserve value. Florida scrub jays, gopher tortoises,


and scrub lizards occur on the site. A Florida East Coast
Railroad track crosses the property from north to
south. There are several fill roads which could be util-
ized for nature trails or management purposes, and the
southwestern portion of the tract includes an aban-
doned road network which could be developed as a
limited-use recreation area.
Another tract (IR-2), dominated by scrubby pine
flatwoods, occurs east of Schumann Drive in the Sebas-
tian Highlands. This 130-acre parcel includes several
small sand pine scrubs within the scrubby flatwoods.
These communities grade into pine flatwoods to the
east, where they adjoin a large wetland and adjacent
residential development (Park Place). Residential areas
of the Sebastian Highlands occur to the north, and the
West Wabasso Cemetary and sparsely developed resi-
dential areas of Wabasso occur to the south. Florida
scrub jays, gopher tortoises, and scrub lizards occur on
the site. Most of this tract has been platted and sold to
individual lot owners, and road construction by General
Development Corporation (GDC) began in late 1987.
Although it is too late to preserve this tract as a
Regional Scrub Community Preserve, GDC has ex-
pressed interest in preserving vestiges of the natural
community through selective clearing of road rights-of-
way. Significant (15-25 acres each) remnants of scrub
occur south of the GDC development just east of the
West Wabasso Cemetery, and on and adjacent to the
Pelican Island Elementary School grounds, respec-
tively. Efforts are being made to preserve these tracts as
minipreserves, in conjuction with establishment of a
Sebastian Florida scrub jay sanctuary including recom-
mended preserve site IR-i, the Sebastian Municipal
Airport, the Sebastian Municipal Golf Course, por-
tions of the Sebastian Highlands, the Pelican Island
Elementary School grounds, and adjacent privately
owned lands.
The west bank of the south fork of the Sebastian
River (IR-3, 600 acres) should be considered for pres-
ervation. This area is not dominated by scrub commun-
ities, but represents a mosaic of xeric hammock,
scrubby flatwoods, sand pine scrub, dry prairie, pine
flatwoods, and forested wetlands. It is not under
immediate development pressure except for the parcel
immediately north of SR 512 (San Sebastian Springs)
which is currently being developed. Although this tract
is not the highest priority scrub preserve tract per se, it is
one of the most valuable natural areas remaining in the
county, and should be considered for protection as a
nature preserve. It consists of relatively undisturbed
lands adjacent to the Sebastian River, and boasts one of
the two documented active bald eagle nesting territories
in the county (one fledgling was produced by this nest-
ing pair of eagles in 1988). The tract is immediately
across the river from Donald MacDonald and Dale
Wimbrow parks, and could be managed as a limited-
access nature preserve. Alternatively, the site is
upstream from Sebastian Inlet State Recreation Area,
and could be managed as an adjunct preserve of that