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 Title Page
 Table of Contents
 Introduction
 Methods
 Results
 Discussion
 Summary
 Bibliography
 Figures
 Tables














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Ecological evaluation of the Green Swamp Riverine Corridor Tract /
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Title: Ecological evaluation of the Green Swamp Riverine Corridor Tract /
Physical Description: ix, 138 leaves : ill. ; 28 cm.
Language: English
Creator: Snyder, Theresa L., 1960-
Publication Date: 1991
 Subjects
Subjects / Keywords: Ecological surveys -- Florida -- Green Swamp   ( lcsh )
Wildlife management -- Florida -- Green Swamp   ( lcsh )
Urban and Regional Planning thesis M.A.U.R.P
Dissertations, Academic -- Urban and Regional Planning -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis (M.A.U.R.P)--University of Florida, 1991.
Bibliography: Includes bibliographical references (leaves 131-137).
Statement of Responsibility: by Theresa L. Snyder.
General Note: Typescript.
General Note: Vita.
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Holding Location: University of Florida
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Resource Identifier: ltqf - AAA9427
notis - AJA2096
oclc - 25151666
alephbibnum - 001690054
System ID: UF00016760:00001

Table of Contents
    Title Page
        Title Page
    Table of Contents
        Table of Contents
    Introduction
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    Methods
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    Results
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    Discussion
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    Summary
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    Bibliography
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    Figures
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    Tables
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Full Text





Report to


Southwest Florida Water Management District




ECOLOGICAL EVALUATION OF THE
GREEN SWAMP RIVERINE CORRIDOR TRACT



Final Technical Report








Mark T. Brown, Theresa Snyder, and Pamela Green










Research Studies conducted under contract to
The Southwest Florida Water Management District






WETLANDS & WATER RESOURCES RESEARCH CENTER
University of Florida
Phelps lab
Gainesville, FI 32611


May 1992










TABLE OF CONTENTS

INTRODUCTION ............................................................. 1
Rationale ..................... ..................................... 1
Review of the Literature: Hydrology and Wetlands .......................... 2
Hydrologic Influences on Wetland Community Structure ................ 2
Impacts of Altered Hydrology ...................................... 3
Groundwater Withdrawals ........................................ 7
Summary of Hydrologic Influences on Wetlands ....................... 9
Review of the Literature: Issues of Wildlife Management ..................... 10
Habitat Fragmentation ............... ........................... 10
Reduction in Habitat Quality ...................................... 11
Impacts of Adjacent Land Use ...................................... 12
Impacts of Public Recreation ...................................... 14
Impacts of Cattle Grazing and Related Activities .................. .... 14
Impacts of Silviculture ....... .................................. 15
Description of the Study Area ........................................... 16
Landscape Associations of the GSRCT ................................ 17
Ecological Communities of the GSRCT ............................... 21
Current Uses and Management ..................................... 25
Plan of Study ....................................................... 27
METHODS .............................................. ................... 30
Map Coverages ................................. ..................... 30
Land Use and Land Cover ......................................... 30
Evaluation of Landscape Heterogeneity .................................... 31
Evaluation of Habitat Suitability ......................................... 34
Calculation of Habitat Values ..................................... 35
Ranking Criteria .............................................. 36
Evaluation of Potential Habitat Suitability ................................. 38
Deriving Potential Land Cover .................................... 38
Map Coverages of Landscape Diversity and Habitat Suitability ................. 39
RESULTS ................................................................. 40
Spatial Distribution of Ecological Communities ............................. 40
Landscape Diversity ................ ................................. 41
Evaluation of Habitat Suitability ........................................ 42
Potential Habitat Suitability ........................................... 48
Evaluating Conflicting Uses and Management ...... ......................... 49
DISCUSSION .......................................... ..................... 52
Management Suggestions .............................................. 52
SUMMARY ............................................................... 65
BIBLIOGRAPHY ............................................................. 68
FIGURES .............................................................. 83
TABLES ................................................................. 118













INTRODUCTION


This is the final report of a study of the Green Swamp Riverine Corridor Tract whose
main objective was to develop a computer aided evaluation system for natural reserves, and then
to suggest management alternatives based on landscape scale values and minimization of
conflicting uses. The overall project was organized into two phases. In the first phase, spatial
analysis of the mosaic of ecological communities lead to ranking of portions of the site according
to their diversity of land cover types (ie landscape heterogeneity) and wildlife habitat
suitability. In the second phase, the results of the ranking were combined with present uses and
management, to develop management suggestions for the tract, as a whole, and for those areas
within the tract which the analysis indicated had special significance.


Rationale


Ecological communities are components of landscapes in which living organisms interact
with each other and with the physical environment around them. As urbanized portions of the
landscape expand, once continuous mosaics of ecological communities are fragmented into
increasingly smaller patches of increasing isolation. Recent initiatives to reverse, or at least
counter these trends have resulted in establishment of natural area preserves of varying size
(from a few acre set-aside within proposed developments, to large parcels purchased under
numerous state and local programs). Often the rational for preservation is that the proposed
reserve is inhabited by threatened or endangered species, or that the area is an especially good
example of an ecological community that is relatively scarce. In other situations, areas are
purchased because of their geographic locations, or physical attributes that make their
remaining in a 'natural' state important. Once purchased, no matter what their size or the
rationale for purchase, natural reserves require some degree of management.
Management of purchased lands may be as 'benign' as allowing natural succession to take
its course, or as intense as management for multiple uses including: timber harvest, cattle












grazing, and public recreation. In some reserves, where listed1 wildlife species are present,
management objectives may be aimed at insuring their continued survival. In all, no matter
what the incremental objectives, management need look at the whole. For, increasingly, it is
becoming apparent that single species (or single objective) management decreases the
likelihood of maintaining a long term sustainable wildlands landscape of ecological communities.



Review of the Literature: Hydrology and Wetlands


The following review of the importance of hydrology on the structure and function of
wetland ecosystems and the affects of altered hydrology on community organization and
processes was summarized from recently completed work for SWFWMD (Brown et. al 1992).


Hydrologic Influences on Wetland Community Structure
Water is the single most critical factor influencing wetland structure and function with
frequency, timing, depth, and duration of inundation the critical factors (Day et al. 1988).
While the chemical constituents of water may be important to vegetative community structure,
depth and duration of flooding are, by far, the most important aspects of water (Jeglum 1975;
Krusi and Wein 1988; Lieffers 1988; Lindholm and Markkula 1984; Mannerkoski 1985). The
effects of water depth and hydroperiod on community structure act through several mechanisms.
First, water depth and duration of flooding affect soil oxygen levels creating anoxic conditions
almost immediately upon soil saturation as a result of the lower diffusion rate of air through
water (Campbell 1980) and effect nutrient availability, oxygen content, redox potential and pH
(Wharton et al. 1982; Damman 1986). Second, decomposition rates are altered. For the most
part, decomposition tends to be faster in flooded sites versus nonflooded sites (Brinson 1977;
Bell et al. 1978; Ewel and Odum 1978; Merritt and Lawson 1979; Shure et al. 1980; Day
1982) although several researchers have suggested the opposite (Lieffers 1988). Third,
moisture regime directly impacts the potential and intensity of wildfire in wetland communities
(see Monk 1968; Ewel 1984). The presence (or lack) of fire has profound implications on


1Listed species are those that are considered threatened, endangered
or species of special concern by state and federal agencies, and have been
included on one of several lists of species sharing this status.












vegetative community structure since many wetland vegetation species are particularly
sensitive to fire. Often when drought conditions prevail for long periods of time, dry surface
layers of accumulated peat (or muck) may readily burn, lowering ground surface elevations and
killing much of the wetland vegetation.
Wetland functions are influenced by water levels and the length of time of inundation.
Both too much and too little water in wetlands can have negative effects on primary productivity
(Mitsch and Ewel 1979; Brinson et al. 1981; and Wharton et al. 1982).
Alternating periods of wet and dry change availability of forage species for herbivorous
animals and can concentrate aquatic organisms for higher carnivorous animals (see Browder
1976 and 1984; Fredrick and Collopy 1988; and Kushlan 1986), while other species,
especially amphibians, favor wetlands that have a dry cycle to eliminate predator fish (see
Heyer et al. 1975; Woodward 1983; Morin 1983; Caldwell 1987; and Moler and Franz 1987)
The importance of hydrology to the spatial distribution of vegetation, both within
communities and at the landscape scale, was demonstrated by several studies of hydrologic
influences on wetland vegetation. Duever (1982, 1988) and Duever et al. (1975) showed that
hydroperiod was the fundamental factor determining distribution of major plant communities.
Studying the spatial heterogeneity of vegetation, Lowe (1986) determined that the spatial
heterogeneity of vegetation in the floodplain marsh of Blue Cypress Lake, in east-central
Florida marsh was largely determined by spatial variation in hydrologic conditions due to
topographic relief.
In all, depth and duration of flooding effect floral and faunal species composition through
two generalized mechanisms: (1) direct alteration of physical conditions favoring one suite of
species over another, and (2) alteration of soil and water chemistry, affecting rates and
pathways of nutrient cycling, pH, and habitat suitability.


Impacts of Altered Hydrology
Numerous studies of the impacts of altered hydrology in Florida wetlands have shown
significant adverse effects. Marois and Ewel (1983) referencing Demaree (1932) and
DuBarry (1963) suggested that alterations of the natural hydrologic cycle of cypress domes
might affect regeneration of cypress because of the dependence of seed upon seasonally
fluctuating water levels for germination and establishment. Fire, which has occurred
historically in cypress ecosystems during the dry season, is an important factor in preventing












the dominance of cypress wetlands by other tree species (Cypert 1961; Gunderson 1977; Ewel
and Mitsch 1978); yet it can become a serious threat to wetland communities that have been
drained (Odum and Ewel 1974).
Harris and Vickers (1978), citing Marois and Ewel (1983) proposed that as water
levels in cypress swamps are lowered, broad-leaved, predominantly evergreen, midstory
plants such as wax myrtle, buttonbush, fetterbush, bays, and dahoon holly become more
common. These changes in water depth and stand structure decrease habitat for aquatic and
wading animals, but seem to favor arboreal species.
Among other things, Marois and Ewel (1983), reported that the drier conditions of
disturbed (drained) cypress domes were associated with changes in vegetation composition: an
increase in the importance and absolute density of hardwood species, and in shrub densities as
well as the invasion of slash pine.
Studying the impacts of drainage in the Melbourne-Tillman watershed in east central
Florida, Barile (1986) provided an example of the impact of wetlands alteration on the
hydrologic cycle. She calculated that drainage within the watershed caused: evaporation rates to
decreased by 5%, evapotranspiration rates to increased by 5% (yet the net result was a 10%
deficit in the amount of water vapor being returned to the atmosphere), surface water flow to
the estuary increased 34%. In addition, with the loss of wetland function due to levee
construction and drainage, groundwater flow decreased if not stopped altogether. Total
groundwater storage in the study area was decreased by 13%. In an earlier study, Barile
(1976) documented loss of wetland soils from oxidation in an area of more than 39 km2 where
the soil classification changed from muck to sand.
Marked seasonal changes, which appeared to be related to water-level fluctuations, were
evaluated related to species composition, distribution, and abundance of the vegetative
community of west-central Florida marshes by Botts and Cowell (1988). The importance of
water depth was greater in marshes with standing water and in seasons when water was present.
They suggested that any alteration of drainage patterns that resulted in diversion of water away
from the marshes could possibly lead to succession toward a pine flatwood community.
Summarizing important ecological monitoring of wetlands in and around wellfields,
Dooris, Dooris, Rochow, and Lopez (1990) suggested the short and long term impacts from
wellfields are now being recognized and described the impacts on vegetation, physical
conditions, and wildlife. Approximately 65 wetlands located in and near several wellfields in












Pasco, Hillsborough, and Pinellas counties have been studied since 1972. Wetlands that were
subjected to shortened hydroperiods resulting from pumpage-induced water table declines
exhibited several physical and biological changes. Affected cypress ponds underwent changes in
understory species composition both in the interior and on the periphery of the pond. Slash
pine invaded many wetland edges and interiors. As the drying became more prolonged,
individual cypress trees began to lean over and fall from dryness, shrinkage, and fissuring of
the peaty soil in most wetlands. If surface waters were not present for long periods of time,
major subsidence of the wetland's entire basin occurred, producing additional tree falls. The
unnaturally dry conditions increased susceptibility of most wetlands to fire.
Environmental evaluations of the wellfields of the northwest Hillsborough County area
provide some detailed information of the effects of groundwater withdrawals on surface waters
and ecological conditions in wetlands. They provide a chronology of impacts to wetlands and
groundwaters at each of the wellfields. The following paragraphs briefly summarize the effects
at selected wellfield locations.
In the fourth annual report of the St. Petersburg-South Pasco Wellfield Study, Bradbury
and Courser (1977) concluded that the shallow water table has been affected by wellfield
pumping. Production from the Floridan Aquifer lowered the potentiometric head in this area,
resulting in increasing downward leakage from the surficial to the artisan aquifer. The long-
term trend of fluctuations of the water table in the wellfield was a lowering of yearly minimum
levels yet maximum yearly water levels were attained. A nearby lake, slightly east of the
wellfield, had declined approximately 1 m since the wellfield went into operation, and the
decline was apparently a direct result of wellfield operations. "Minor" changes occurred in the
wetland vegetation of the South Pasco Wellfield since the initiation of production. The changes
generally reflected the drawdown of the surface water table which occurred with the onset of
pumping. Weedy, annual plants invaded wetland areas as a result of the shortened period of
inundation. However, they had not "established" themselves and with heavy rain, were "knocked
back" when some wetland plants made a recovery to previous levels of abundance. The authors
suggest that "overall, there has been little damage of major significance, caused by the wellfield
to date." However, in earlier reports, late flowering and leaf-out of cypress, blowdowns of
trees, and significant fires were noted, and they state "even the slightly higher-than-average
rainy season did not help mitigate this impact [fire when water table was low] as some trees
began to visibly lean in the fall."












Lopez (1983) reviewed six years of monitoring (1977-1982) at City of Tampa's
Morris Bridge Wellfield and Water Treatment Plant. The program gathered data on surface
water levels, groundwater levels, and understory vegetation composition within several wetland
habitat types. At the time of the report there was no evidence of widespread adverse vegetational
changes within most wetlands in the wellfield. However, conditions at several monitoring sites
were diagnostic of prolonged dry conditions, beyond the range of those exhibited by control sites
and other sites within the wellfield. Reductions in hydroperiod at several sites had resulted in
adverse changes in wetland vegetation. Vegetation data (quadrats and transects) indicated
changes in species composition and abundance, ranging from the invasion of wetland areas by
weedy, terrestrial plant species to the complete disappearance of obligate aquatic and semi-
aquatic plants. Additionally, transect data illustrated shifts in the areal extent of plant
communities as a result of altered hydroperiods.
Biological Research Associates, Inc. (1987 and 1988) assessed the overall condition of
the environment at the end of the second year of ecological monitoring on Morris Bridge
Wellfield. Based on the vegetation transect analysis, conditions were drier on-site than off-
site. The vegetation transects showed that on-site transects had more species and a greater
cover of species classified as facultative, facultative upland, or upland by the USFWS Wetland
Species Classification. Obligate and facultative wetland species were more abundant off-site
than on-site. The results of tree growth, mortality, and recruitment monitoring were
inconclusive. Mortality and recruitment appeared to be dominated more strongly by fire than
by water table. They suggested that wetlands on the wellfield may have been in a state of flux in
response to changing hydric conditions, yet that it was not possible to assess if wetland plant
communities have reached an equilibrium in species composition.
The Environmental Section of the SWFWMD had monitored environmental conditions at
the Starkey Wellfield and Wilderness Park for more than 10 years (Rochow 1985a). The
monitoring indicated that in the portions of the wellfield where pumping was greatest wetlands
experienced cycles of moderate inundation interspersed with relatively lengthy periods of
dryness and some have shown a noticeable successional trend toward a more upland terrestrial
environment.
Rochow (1985b and 1985c) reported on the hydrobiological monitoring at the Cypress
Creek Wellfield in Pasco County, Florida. The Environmental Section of the SWFWMD had
monitored environmental conditions at the wellfield for more than 10 years. Several cypress











and marsh monitoring sites within the Cypress Creek Wellfield experienced lower-than-
expected water levels in the years after water production began in 1976. Wellfield monitoring
sites with at least two years without surface water experienced a complete loss of typical deep-
water, aquatic plant species such as pickerelweed and rush (Juncus repens). In three dry
marshes, maidencane or willow expanded through the central marsh area; in one marsh, blue
maidencane invaded the outer, formerly shallow-water marsh fringe. Only one cypress dome
was dry for at least two consecutive years. Despite subsequent water augmentation from a
nearby production well, dog fennel and buttonbush replaced pickerelweed in the central area of
the dome. Control wetland sites, unlike several wellfield sites, experienced surface water
throughout the monitoring period, including the years with below-normal precipitation.
Wetland conditions at the Eldridge-Wilde Wellfield were reevaluated by Rochow (1988)
six years after the last evaluation. It appeared that wellfield wetlands were in about the same
condition, that is "poor" in the majority of areas where good wetlands once existed. Rochow
attributed the poor quality to three characteristics: abnormally low wetland water levels,
wetland subsidence, and excessively destructive fires. In earlier work, Young (1974) recorded
extensive damage to cypress heads within the northern portions of the Eldridge-Wilde Wellfield.
Several of the cypress heads had been totally destroyed. Young suggested the damaging effects of
the loss of water to the cypress heads included shrinkage of the organic soils from desiccation
and apparent land subsidence. However the most serious damage came from fire. The
investigation suggested the effects of the cone of depression from well pumpage extended
laterally a maximum of approximately 1.3 km beyond the boundaries of the wellfield.


Groundwater Withdrawals
Groundwater withdrawals, whether from deep or shallow aquifers, can have a marked
effect on the shallow water table levels (Parker 1973, 1975). Lowered shallow water table
levels can have marked impact on wetland hydrology since many wetland ecosystems are
intimately connected with the surficial aquifer. The literature on groundwater withdrawal
effects on wetland hydrology is, for the most part, confined to scientific reports on the
hydrobiological monitoring of wellfields. However, Bays and Winchester (1986) reviewed
factors thought to be contributing directly and indirectly to the changes being observed in
Florida wetlands, and concluded that groundwater withdrawals were one of the more significant












changes, although somewhat limited in their spatial extent. Their summary of the process of
change is relatively straight forward:
Groundwater withdrawal affects the water table either directly through
withdrawals from the surficial aquifer, or indirectly through withdrawals from
the deep aquifer, the latter which lowers the potentiometric surface and induces
recharge from the surficial aquifer. Around each point of withdrawal, a cone of
depression is formed in the potentiometric surface and to a more variable extent,
the water table. The areal extent and depth of the cone of depression depend on a
number of factors; the most important are the amount of leakage through the
confining layer, transmissivity in the deep aquifer, and the distribution and
amount of withdrawals. As wells operate together in proximity, their respective
cones of depression can overlap to cause a broader or deeper zone of depressed
potentiometric and water table levels. This process is dynamic, with water
levels fluctuating in response to recharge by rainfall, fluctuations in the
potentiometric surface, and local and regional variation in pumpage.

Groundwater withdrawals have impacts on surface water runoff as well as surficial
groundwater elevations. Cherry, Stewart, and Mann (1970) analyzed duration of low flow of
Brooker Creek near Tarpon Springs for two time periods, 1951-58 and 1959-66; periods
prior to and following large groundwater withdrawals from the Floridan Aquifer in portions of
the creek's basin, which began in 1958. They concluded that during a period of increased
groundwater withdrawals and higher than average rainfall, more low flow days occurred
indicating that groundwater pumping did reduce the flow of the stream. A similar analysis of
low-flow duration of the Anclote River near Elfers was made for 1951-58 and 1959-66. Like
Brooker Creek, the Anclote River had more low flow days during the period of high rainfall and
increased groundwater withdrawals. However, Brooker Creek showed the greatest effect
because the drainage area of the creek was almost entirely within the cones of depression of
wellfields.
Concern over lake levels prompted the Hillsborough River Basin Board to request that
the USGS provide model simulation data that would portray the effects of wellfield pumping on
Lakes Thomas, King, and Bell (Knutilla 1985). Six pumping scenarios were simulated by the
model based on current consumptive-use permits (CUPs) for three adjacent wellfields. Model
results indicated that the greatest hydrologic impact on the lakes would occur when the three
wellfields were pumped simultaneously. As indicated by the simulated water table drawdown,
the levels of Lakes Thomas, King, and Bell would decline equally, about 18 cm each, when the
wellfields were pumped at the average permitted rate of 76.9 MGD.












Bengtsson (1989) discussed the impacts related to short-term water level declines
associated with seasonal agricultural withdrawals in east-central Hillsborough County, Florida.
The impacts included: failure of domestic wells and pumps, sinkhole formation and flooding
from the irrigation runoff. A simulation model was used to quantify the impacts of the
withdrawals to the potentiometric surface of the Floridian Aquifer. The model indicated minimal
effects to the water table; however, pumpage and recharge to the surficial aquifer was not
included in the simulation. Induced recharge through the semiconfining unit above the pumped
aquifer created a small amount of drawdown in the surficial aquifer.


Summary of Hydrologic Influences on Wetlands
Wetland hydrology is a dynamic balance between rain, run-in, recharge, discharge and
evapotranspiration. Hydrology affects the structural properties of wetlands and rates of
internal processes. In turn the structural properties like basin morphology, accumulations of
organic matter, and hummocks that result from tree falls affect both gross hydrologic patterns
and smaller scale topographic differences that affect hydroperiod. There is a suggestion that
some wetlands may influence deep geologic formations through percolation of acidic waters and
thus maintain their depressional status in a balance between accumulation of organic matter and
solution of underlying limestone as organic matter accumulates.
There is no doubt that wetland hydrology, specifically depth, duration of flooding, and
periodicity, influence vegetative structure and in turn influence faunal community structure.
Depth alone does not explain differences in wetland vegetative community structure; but
duration of flood and dry periods are cited as the primary variable influencing community
structure and susceptibility to fire. Altered hydrology is the most cited reason for loss of
wetland functions.
Since wetland hydroperiod is the single most important factor influencing wetland
functions and values, and since it in turn is strongly influenced by changes in its forcing
functions, there is strong impetus to control exogenous activities that affect groundwater
elevations. Direct drainage and thus lowering of groundwater elevations, increases in runoff,
and groundwater withdrawals are the three most important factors affecting groundwater
elevations. The protection of wetlands and their functions is not only a matter of protecting
them from dredging and filling, but preserving their hydrology.












Review of the Literature: Issues of Wildlife Management


Schaefer (in Brown et.al 1991) categorized the issues of wildlife management into 8
areas: Habitat Fragmentation, Wildlife Corridor Misconceptions, Decrease in Landscape
Diversity, Reduction in Habitat Quality, Impacts of Adjacent Land Use, Impacts of Public
Recreation, Impacts of Cattle Grazing and Related Activities, Impacts of Silviculture. Of these,
habitat fragmentation, reduction in habitat quality, impacts of adjacent land use, impacts of
public recreation, impacts of cattle grazing, and impacts of silviculture are most relevant to the
GSRCT and are summarized below.


Habitat Fragmentation
The effects of fragmenting or reducing habitat size on animal communities (especially
birds) has been researched as a means of providing a scientific bases for the proper design of
nature preserves surrounded by areas with little or no habitat values. Earlier work involved
the species area relationship that is so prevalent in the ecological literature (Arrhenius 1921,
Gleason 1922, Preston 1960 and 1962, MacArthur and Wilson 1967). More recently,
forested fragments have been studied as islands of natural habitats surrounded by culturally
modified land (Terborgh 1974, Sullivan and Shaffer 1975, Wilson and Willis 1975, Diamond
and May 1976, Forman et al. 1976, Galli et al. 1976, and many others).
The process of habitat fragmentation is accompanied by insularization of fragments, i.e.,
isolated pieces of habitat surrounded by dissimilar habitat. Eventually, fewer native species
will be found in a habitat island than in a sample area of equal size within an extensive block of
habitat (Harris 1984). The number of species may not change much, or may even increase in
isolated habitats, but species composition will shift toward the more common non-forest-
dependent species. There have been numerous studies of the relationship between size of forest
stand and populations of bird species. Smaller forest islands surrounded by clear cuts or
agricultural fields contained fewer bird species than larger contiguous stands (Linehan et al.
1967, Moore and Hooper 1975, Forman et al. 1976, Galli et al. 1976, McElveen 1978,
Wilson and Carothers 1979, Stauffer and Best 1980, Martin 1980, Robbins 1980, Tassone
1981, Ambuel and Temple 1983, Lynch and Whigham 1984, Blake 1986, Blake and Karr
1987, Temple 1986). Similar results have been shown from Florida studies. Harris and











Wallace (1984) reported that the number of breeding bird species occupying habitat islands in
north central Florida hammocks increased as a direct function of island size.
The validity of the forest island size vs. species model has been little tested concerning
other taxa. Variations in mammalian species richness was reported by Kitchener et al.
(1980b) and Matthiae and Stems (1981). Shreeve and Mason (1980) found area to be
correlated with the number of butterfly species.
There are many potential interpretations of the species-area relationship. Four general
explanations are (1) larger areas support more kinds of habitats (and thus more habitat-
specific species), (2) larger areas offer bigger "targets" for organisms dispersing across the
landscape, (3) larger areas maintain larger populations that are less vulnerable to extinction
due to random or deterministic population fluctuations, and (4) larger areas support animals
with large territory and home range size that cannot be supported in small areas. Any one of
these explanations is powerful enough to support the general recommendation that nature
preserves should be as large as possible (Soule and Wilcox 1980, Frankel and Soule 1981,
Schonewald-Cox et al. 1983, Harris 1984, Soule 1986).


Reduction in Habitat Quality
By far, the most common cause of wildlife population reduction is natural landscape
alteration through agriculture, silviculture, or construction activities. Altering or changing
natural conditions to which species are adapted often harms native wildlife communities by
destroying key elements that make a habitat suitable. Timber harvesting stops natural
succession of aging forests. This results in forest landscapes dominated by relatively young,
even-aged stands. These young forests lack the structural and functional diversity of older
forests. These managed forest landscapes may be ecologically inadequate to ensure long-term
forest productivity (Maser and Trappe 1984, Spies and Franklin 1988) and the perpetuation of
the full array of wildlife populations. Many species of wildlife including flying squirrels,
several species of bats, pileated woodpecker, red-cockaded woodpecker, a variety of cavity-
nesting birds, and several species of amphibians are dependent on old, mature forests.
Extinction of the ivory-billed woodpecker (Campehilus principals) in the United States and the
endangered status of the red-cockaded woodpecker are associated with the loss of old forests
(Thomas et al. 1988).












Impacts of Adjacent Land Use
The question of how large a habitat area must be to maintain biological integrity cannot
be answered without considering the impacts of land uses adjacent to the preserve. The negative
effects of induced edge on species have been reported by Faaborg (1980), Samson (1980), Noss
(1981, 1983), Samson and Knopf (1982), Harris (1984), and Noss and Harris (1986). The
type of habitat on the outside of a forest edge determines the nature of edge effects. A general
principle is that the greater the contrast between habitat types, the greater the edge effect
(Harris 1984). Modified areas surrounding a forest fragment are usually altered into earlier
successional stages. These types of habitats are then attractive to pioneering species that invade
several hundred meters into the adjacent forest fragment and alter species composition and
relative abundances.
The negative impacts of induced (man-made) edges in a forested system and of the noise
and domestic animal problems associated with development adjacent to natural habitat areas
have been reported by Brown et al. (1990). Earlier studies of edge effects focused primarily
on bird populations of forested tracts.
Whitcome et al. (1976) provided evidence that, in areas along forest edges avian brood
parasites (brown-headed cowbirds), nest predators (small mammals, grackles, jays, and
crows), and non-native nest hole competitors (e.g. starlings) are usually abundant. Gates and
Gysel (1978) found that a field-forest edge attracts a variety of open-nesting birds, but such
an edge functions as an "ecological trap." Birds nesting near the edge had smaller clutches and
were more subject to higher rates of predation and cowbird parasitism than those nesting in
either adjoining habitats. This abnormally high predation rate is related to the artificially high
densities of many opportunistic animals near forest edges and in disturbed habitats including
suburbs; (Wilcove et al. 1986).
Any forest tract has a "core area" that is relatively immune to deleterious edge effects
and is always far smaller than the total area of the forest (Temple 1986). Relatively round
forest tracts with small edge-to-interior ratios would thus be more secure, whereas thin,
elongated forests (such as those along unbuffered riparian strips) may have very little or no
core area and would be highly vulnerable to negative edge effects.
Sound is a physical phenomenon and defined as an oscillation in pressure of a medium
measured in decibels (dB); (American National Standards Institute 1971). Sometimes, sound
is noise which is defined as unwanted or undesirable sound (U.S. Environmental Protection












Agency 1978). This annoyance factor of sound negatively impacts all hearing animals. Along
with air and water contaminants, noise has been recognized as a serious pollutant.
Noise associated with construction, operation, and maintenance of developments can
cause harmful impacts on wildlife. Animals that rely on their hearing for courtship and mating
behavior, prey location, predator detection, homing, etc., will be more threatened by increased
noise than will species that use other sensory modalities. However, due to the complex
interrelationships that exist among all the organisms in an ecosystem, direct interference with
one species will indirectly affect many others.
Unfortunately, few data are available that demonstrate the specific effects of noise on
wildlife Much of what is found in the literature lacks specific information concerning sound
intensity, spectrum, and duration of exposure. There have been no systematic studies with
experimental designs that show definite relationships between specific noise disturbances for
various species and different sound levels. Brandt and Brown (1988) conducted an extensive
literature search on this topic and found that most of our current knowledge of sound impacts on
wildlife are based on observations of animal reactions to aircraft overflights and laboratory
studies. Because such little research emphasis has been given to this topic, it is not surprising
that results are inconclusive and sometimes contradictory.
While general understanding and consequences of noise impacts on wildlife are not very
specific, a few conclusions are obvious. Short-term exposure to loud sounds can cause
physiological changes in animals as it does in humans. Chronic lower level sounds (55 dB) are
annoying to humans and also probably make an area relatively less desirable to wildlife. Some,
but not all, species can adapt to some sounds. Human activity also disturbs wildlife and can have
similar effects such as nest abandonment. Noise and human activity will negatively impact semi-
aquatic and wetland-dependent wildlife from the landward side as well as the water side if the
water is used for recreational purposes.
Edge effects have been shown to negatively impact wildlife species within at least 300
feet of forest boundaries. Studies of nature reserve boundaries have provided data that support
the need for buffer zones of decreasing use outside reserve boundary (Unesco 1974, Dasmann
1988, Schonewald-Cox 1988). The core of these areas must be protected from cats, dogs,
human activities, noise, predators, exotic competitors, parasitism and other detrimental effects
of development.












Impacts of Public Recreation
Assessing direct impacts of human recreational activities on wildlife is a newly evolving
science. Boyle and Samson (1985) summarized 106 recreational impact studies and reported
that 73% of these concluded nonconsumptive activities negatively affected bird communities.
Hiking and camping affect wildlife through trampling of habitat (Liddle 1975), disturbance of
animals (Ward et al. 1973, Aune 1981) and less directly through discarded food or other items
(Foin et al. 1977).
Human disturbance of waterbird colonies has been shown to cause nest losses through
predation (Schreiber and Risebrough 1972, Hand 1980, Anderson and Kieth 1980) and nest
abandonment (Hunt 1972, Ellison and Cleary 1978). Some duck species and the great crested
grebe did not winter in one reservoir since it was opened to sailboats, even though these species
were observed elsewhere in the vicinity (Batten 1977). Rodgers and Burger (1981) reported
that human activities in waterbird colonies may delay nesting for some pairs, eliminate late-
nesting pairs, or cause late-nesting pairs to shift to other less suitable nesting sites. Tremblay
and Ellison (1979) reported that visits to black-crowned night heron colonies just before or
during laying provoked abandonment of newly constructed nests and either predation of eggs or
abandonment of eggs followed by predation. This study also concluded that herons did not nest in
areas where human interference occurred. Ellison and Cleary (1978) found similar results
with double-crested cormorants. Wintering eagles were more disturbed by infrequent
activities than by regular activities (Stalmaster and Newman 1978). Landin (1978)
recommended protecting all wading bird nesting areas from human activities during the nesting
season.
Effects of boating and swimming have been reported primarily for birds. In a
comprehensive review, Liddle and Scorgie (1980) noted that wildlife is affected through sight
and sound of recreationists, pollution from boats and recreational facilities, and habitat changes
caused by vegetation control practices and facility construction. Beach and shore recreationists
can disrupt shorebird breeding (Norman and Saunders 1969) or force birds into less preferred
habitats (Erwin 1980).


Impacts of Cattle Grazing and Related Activities
Specific impacts of cattle grazing that may occur on ecosystems and wildlife within the
GSRCT depend on several variables such as the number and density of cattle, type of ecosystem,












the current condition of the vegetation, the amount of vegetation or forage available, the time of
year, the grazing schedule, the size of the area, surrounding land use, and the species of wildlife
present. In general the literature seems to suggest that if grazing is controlled at some level, it
can be compatible with wildlife conservation efforts.
Most grazing/wildlife studies have focused on the competition of wildlife and cattle for
food resources in western rangelands. Landowner interest in managing game species as a valued
commodity has stimulated some research on the compatibility of cattle grazing and game
management. Several studies have concluded that grazing must be controlled to effectively
manage for game species (Grover and Thompson 1986, Austin and Urness 1986). There also
are some studies that provide evidence of grazing practices benefit nongame wildlife ( Harrison
1975, Crouch 1982, Johnson 1982, Bue et al. 1952). However, few differences between
pastures in small mammal communities were evident prior to grazing, one month following
grazing, and no differences in numbers or distribution of small mammals were observed five
months following grazing levels recommended by SCS in Colorado (Samson et al. 1988).
Consistent differences also were not found in abundance, diversity, and microhabitat of small
mammals between an ungrazed and a deferred-rotational grazed areas in Nevada (Oldemeyer and
Allen-Johnson 1988).
After a review of the literature, May and Davis (1982) concluded there is little question
that overgrazing and excessive livestock use of streamside areas can exert negative influences
on stream ecosystems. They added that these influences can be minimized with proper planning
and controlled livestock use. Trout stream habitat was detrimentally influenced by livestock
grazing in Montana (Hitchcock 1988).


Impacts of Silviculture
Alteration or manipulation of vegetation in any area will impact wildlife species living
there. Some animals will benefit by these changes and others will lose life sustaining
requirements. Removing trees will enhance the landscape for wildlife that prefer early
succession, open habitats. Such areas will become unsuitable for species that depend on mature
trees for food and cover.
During a 15 year study of wildlife responses to even-aged silvicultural practices in
Alabama, potential food availability was highest for deer, turkey and quail during years 3 and 4
of the study (Johnson 1986). Use generally increased for deer, however, their overall


L












physical condition decreased following crown closure. Use decreased for quail, squirrels,
raccoons and opossums while turkey and rabbit usage was generally stable. No data was
collected on other species.
Clear cutting of pine forests has been shown by a variety of studies to negatively affect
wildlife populations. Bird and small mammal abundance and diversity was greater in a mature
long leaf pine stand than in nine-year-old slash pine plantations Harris et al. (1975).
Following harvest in flatwoods stands in north Florida, bird use shifted from being evenly
dispersed to concentrating in cypress domes and edges of stands (Marion and O'Meara 1982).
Amphibian and reptiles abundance post harvest was only half of that recorded in pre-harvest
areas. Clear cutting in mixed oak stands in Virginia initially reduced breeding bird species
diversity and abundance (Conner and Adkisson 1975), This management practice also altered
species composition. Although clear cutting in north Florida flatwoods did not affect amphibian
species richness, reptile richness was lower in the maximum-treatment clear cut, amphibian
abundance was reduced, reptile abundance was reduced, and species composition was altered
(Enge and Marion 1986). Habitat quality for the red-cockaded woodpecker can be significantly
affected by clear cutting. The reported average ages of cavity trees for the endangered red-
cockaded woodpecker ranged from 63-176 years for long leaf pine and 70-76 years for slash
pine (U.S. Fish and Wildlife Service 1985).



Description of the Study Area


The study area is a 54,000 acre tract of land owned by the Southwest Florida Water
Management District, known as the Green Swamp Riverine Corridor Tract (GSRCT). The GSRCT
is located in the central Florida and includes portions of Polk, Sumter, and Lake counties
(Figure 1). An abandoned railroad track borders the northeast portion of the GSRCT, State Road
471 borders its west along the Pasco and Sumter county lines and U.S. 98 runs diagonally just
to the south of the property. A major electric power transmission line crosses along the border
of the northern area and numerous dirt roads crisscross the tract. The Withlacoochee State
forest, lies immediately to the north of the GSRCT.
The GSRCT is within a larger area known as the "Green Swamp". The Green Swamp is
not a true continuous swamp, but rather an area of higher table lands with shallow depressions












which trap and store water, creating a natural retardance for flood waters while also providing
habitat for wildlife. The Green Swamp is the headwaters for 5 rivers: the Withlacoochee,
Peace, Kissimmee, Oklawaha, and Hillsborough Rivers. Earlier analysis and mapping of the
Green Swamp (Brown et al. 1975) revealed the extent of wetlands. In 1973 the area of
wetlands measured from aerial photographs was approximately 31.5%.


Landscape Associations of the GSRCT


The GSRCT consists of a variety of natural ecological community types defined by the SW
Florida Water Management District (1990) including: pine flatwoods, upland hardwood forests,
wet prairies, freshwater marshes, cypress domes, riverine cypress, mixed hardwood swamps,
riverine mixed hardwood swamps, low temperate hammocks, and upland temperate hammocks.
Descriptions of community types often neglect the interactions between systems and for this
reason we present a narrative based on a larger perspective, the landscape association.
Associations are mosaics of ecological communities, usually a matrix (or background)
community type with lesser area of one or several different community types. They have
distinct topographic, geologic, and hydrologic conditions and landscape position. The associations
of the GSRCT are: Flatwoods/Isolated Wetlands, Flatwoods/Flowing Water Wetlands,
Flatwoods/mesic hammocks/hydric hammocks/hardwood swamps Much of the area of former
pine flatwoods throughout the GSRCT has been cleared and replanted in slash pine. Some areas
remain uncut. Yet prior to timber harvest the area was dominated by a matrix of flatwoods with
interspersed wetlands and hammocks.


Landscape Classification 1. Flatwoods/Isolated Wetlands This association is characterized by
very low topographic relief and very minor surface drainage features. As a result, overland
flow during the wet season and significant storm events is quite common. During normal years,
water tables are at or near the ground surface for about six months of the year.
Pine flatwoods are so named because of the flat topography on which this association is
typically found. The lack of gradient results in frequent flooding during the summer rainy
season (Brown 1980). Often underlain by a "hardpan" of organic materials, clays or accreted
oxides, that retard downward migration of groundwaters, flatwood soils are often poorly drained
and flood easily. Many grassy scrub areas and palmetto prairies were probably once pine











flatwoods that have been converted to grassy scrub by tree harvest, increased drainage, and/or
greater fire frequency (Brown 1980).
Interspersed throughout the flatwoods are topographic low areas, which are occupied by
patches of wetlands of various types. Wetlands are typically circular in shape and vary from
quite small (less than one-half hectare) to large (tens of hectares). Depth of standing water in
isolated wetlands during the rainy season is typically 46 to 64 centimeters (8 to 24 inches).
Wetland types include cypress domes, bayheads, wet prairies, and shallow marshes (Brown and
Schaefer 1987). Occasionally deep freshwater marshes (Brown 1980) are found, although they
most often are associated with areas of higher relief and greater surface water drainage. The
wetlands in this association are relatively oligotrophic whose main source of nutrients is
rainfall and a minor surface drainage from small surrounding watersheds.
Cypress domes are dominated by pond cypress (Taxodium ascendens). Dominant tree
species in bayheads include red bay (Persea borbonia), sweet bay (Magnolia virginiana),
loblolly bay (Gordonia lasianthus), black gum (Nyssa sylvatica), red maple (Acer rubrum),
pond pine (Pinus serotina), and slash pine (Pinus elliottii). Typical wet prairie plants include
St. John's wort (Hypericum fasciculatum), primrose willow (Ludwigia spp.), elderberry
(Sambucus simpsonii), panicum grasses (Panicum spp.), soft rush (Juncus effusus), spike
rush (Eleocharis cellulosa), and pickerelweed (Pontederia cordata).
Shallow marshes may be dominated by one of the following species: pickerelweed (P.
cordata), sawgrass (Cladium jamaicense), arrowhead (Sagittaria spp.), fire flag (Thalia
geniculata), cattail (Typha spp.), spikerush (E. cellulosa), bulrush (Scirpus spp.), or
maidencane (Panicum hemitomon); some marshes contain patches or mixtures of some or all of
these species (Brown and Starnes 1983).
The flatwoods/isolated wetland association is found throughout the GSRCT occupying the
flat table lands between drainage features and is especially prominent in the northeast and north
central portions of the tract


Landscape Classification 2. Flatwoods/Flowing Water Wetlands The soils in this category are
poorly drained and have higher percentages of clay and organic matter than do those of the
flatwoodslisolated wetland association. Unlike the table lands of the first association, the
topography of this association is more variable. Having somewhat greater relief, the flatwoods
of this association have surface drainage features that resemble elongated swales dominated by












wetland vegetation. Both surface and groundwaters contribute water flows to the wetland
drainage features.
Sloughs or strands are elongated wetlands with no open water channels; however, water
flows imperceptibly slow as sheet flow during the wet season and through small, braided
channels during drier times.
Flowing water wetlands include both sloughs dominated by pond cypress (Taxodium
ascendens) and southern mixed hardwood forests growing throughout sloughs and strands.
Common hardwood species include red maple (A. rubrum), water tupelo (Nyssa aquatica,
swamp black gum (Nyssa sylvatica var. biflora), sweet gum (Liquidambar styraciflua), pop ash
(Fraxinus caroliniana), Florida elm (Ulmus floridana), and cabbage palm (Sabal palmetto)
(Brown 1980).
The seasonal flooding that is characteristic of flowing water wetlands provides the
nutrients needed for plant growth. Water levels can fluctuate about 0.75 meters (2.5 feet)
between the wet and dry season in an average year. The normal depths of inundation are about
61 to 76 cm (24 to 30 inches). Often deeper pools in a slough may be as deep as 1.5 meters (5
feet) (Brown and Starnes 1983). Flooding is also important for seed distribution, seed
scarification, and elimination of upland plant species (Brandt and Ewel 1989).
The flatwoods/flowing water wetlands association is the most common association in the
western and southern portions (contributing surface water to the Withlacoochee River) of the
GSRCT.


Landscape Classification 3. Flatwoods/mesic hammocks/hydric hammocks/hardwood swamps -
More moderate to moderately well drained sandy soils and level to sloping topography
characterize the uplands of this association. Between the upland communities of flatwoods and
mesic hammock and the lower zone communities of hardwood swamp or marsh, hydric
hammocks often occur where moisture conditions maintain soils in constant saturation but
rarely, if ever, flood.
The excellent growing conditions and good soils foster the development of quite diverse
and robust pine flatwoods. If fire is excluded, the mesic hammocks that follow are the most
diverse of the upland communities in the central Florida region and may contain between 8 and
35 tree species. Overstory species in mesic hammocks include Southern magnolia (Magnolia
grandiflora), laurel oak (Quercus laurifolia), red bay (P. borbonia), pignut (Carya glabra),











American holly (llex opaca), water oak (Quercus nigra), black cherry (Prunus serotina), and
live oak (Quercus virginiana). The canopy is so dense that little sunlight reaches the forest
floor. Soils are moderately well drained to somewhat poorly drained. Rainfall is the major
water source for mesic hammocks, although seepage and runoff may provide water to some
stands (Brown 1980).
Soils in hydric hammocks are generally shallow and sandy, and limestone (either in
bedrock or in nodules in the soil) is most often present (Vince et al. 1990). Hardpans (weakly
cemented Bh horizons) do not occur in hydric hammocks, but clay layers that support surficial
water tables occur in some hammocks (Vince et al. in press).
Where high water tables are characteristic, hydric hammock soils are saturated most of
the year (Brown and Schaefer 1987). Sources of water to hydric hammocks include
groundwater seepage, rainfall, stream overflows, and aquifer discharge (Simons et al. in
press); groundwater seepage from uplands is the major source of water for many hydric
hammocks found bordering floodplain swamps. Hydric hammocks have the most diverse flora of
any wetland in central Florida. Species include pop ash (F. caroliniana), live oak (Q.
virginiana), laurel oak (Q. laurifolia), water oak (Q. nigra), Southern magnolia (M.
grandiflora), red bay (P. borbonia), sweet bay (M. virginiana), tulip poplar (Liriodendron
tulipifera), red maple (A. rubrum), red cedar (Juniperus silicicola), cabbage palm (S.
palmetto), slash pine (P. elliottii), and blue beech (Carpinus caroliniana) (Brown and Starnes
1983).
Hardwood swamps are characterized by seasonal flooding of the flowing waters along
which they are found. Species composition depends upon the flow rate, water quality, and
turbidity of the adjacent waterway. The most common species are red maple (A. rubrum),
water tupelo (N. aquatica), swamp black gum (N. sylvatica var. biflora), sweet gum (L.
styriciflua), bald cypress (T. distichum), pop ash (F. caroliniana), Florida elm (U. floridana),
and cabbage palm (S. palmetto) (Brown 1980). Soils associated with this community are
nearly level, very poorly drained, and dark in color. They are either organic or have coarse- to
medium-textured surfaces underlain by finer textured material (Brown and Starnes 1983).
The higher relief and somewhat "better drained" topography of the southern portions of
the GSRCT adjacent to the Withlacoochee River are dominated by this landscape association.












Ecological Communities of the GSRCT


Landscape associations are composed of a "matrix" of upland ecological communities and
one or more wetland community types that are surrounded by the upland matrix. In this section
descriptions are given of the upland and wetland ecological communities of the GSRCT.


Upland Communities
Pine Flatwoods The pine flatwoods ecosystem is the most common and widespread in Florida.
Given its extensive coverage, the pine flatwoods exhibits a broad variety of growth forms from
communities resembling prairies with widely scattered long leaf pines (Pinus palustris) to
extremely dense communities of long leaf pine (P. palustris) and slash pine (P. elliottii) on
moderately drained soils, to dense communities of pond pine (P. serotina) often growing in
poorly drained sloughs. Most frequently, pine flatwoods occupy nearly level, poorly drained
soils that are strongly acidic, and have a "hardpan" several feet below the ground surface. These
conditions lead to frequent flooding during the wet season, and often flatwoods are flooded from
June through September. However, just as they are prone to flooding during the wet season,
they are also prone to drought conditions during the dry season (October to May). With the dry
season drought and the flammable nature of the litter layer, fire is a common occurrence in the
pine flatwoods. The community is adapted to fire and often referred to as a "fire climax"
community; if fire is withheld, the community often succeeds to a hardwood forest or hammock.
Throughout the GSRCT, the flatwoods were once dominated by long leaf pine (P.
palustris) and slash pine (P. elliottii). In many locations, as the result of earlier logging, the
original canopy of long leaf and slash pine has been almost eliminated and replaced with forests
of improved slash. In some areas long leaf pine is now being planted. Where the canopy is open
and much sunlight can reach the understory vegetation, a dense layer of saw palmetto (S.
repens) often becomes the dominant species in the shrub layer. Other species in the shrub
layer include: fetterbush (L. lucida), staggerbush (L. fruticosa), pawpaw (Asimina
reticulatus), shiny blueberry (Vaccinium myrsinites), sparkleberry (Vaccinium arboreum),
tarflower (B. racemosa), wax myrtle (Myrica cerifera), gallberry (Ilex glabra), and dwarf
huckleberry (Gaylussacia dumosa).
While quite common, "healthy" examples of robust flatwoods are increasingly hard to
find. The majority of the "native" pine flatwood communities are scattered throughout the tract











with the largest concentrations adjacent to and west of the Devils Creek Swamp and the
Withlacoochee River.


Mesic Hammock The mesic hammock community is a hardwood forest ecosystem also called a
southern mixed forest. The term "hammock" seems to be an old colloquial term meaning grove
or stand of trees. Over the years it has come into common usage and is often used to describe
forested communities in conjunction with the terms xeric, mesic and hydric, to differentiate
between dry, moist, and wet hammocks, respectively.
The mesic hammock occupies moderately well-drained, neutral soils and is believed to
be the latter successional stage resulting from the absence of fire in pine flatwoods. The canopy
is quite diverse and dominated by any of the following: Southern magnolia (M. grandiflora),
laurel oak (Q. laurifolia), red bay (P. borbonia), pignut (C. glabra), American holly (1.
opaca), water oak (Q. nigra), black cherry (P. serotina), live oak (Q. virginiana), sweet gum
(L. styriciflua), and cabbage palm (S. palmetto). The understory is often composed of seedlings
of the overstory as well as saw palmetto (S. repens), wax myrtle (M. cerifera), persimmon
(Dispyros virginana), fetterbush (L. lucida), and various grasses and sedges.
The most extensive areas of this community type occur in the southern portions of the
tract adjacent to the Withlacoochee River.


Wetland communities
There are several types of wetlands occurring within the GSRCT. Community structure
of wetlands is controlled primarily by hydrologic parameters (hydroperiod and depth of
inundation) and then by other factors such as soils, recent fire history, and logging activities.
The types of wetlands are as follows: bayheads, cypress domes/strands/sloughs, mixed
hardwood swamps, hydric hammocks, wet prairies, shallow marshes, and deepwater marshes.
Each is discussed in some detail below.


Bay swamp communities The bay communities of the GSRCT are, for the most part,
quite young, and quite dispersed. Bay swamps naturally occur where ground surfaces are rarely
inundated to any degree for long periods of time, but saturation is quite common for most of the
year. Seepage areas at the base of sandy ridges are often dominated by bay communities.











Experience has shown community shifts from cypress wetlands to bay swamps in response to
lowered groundwater tables and fire.
Bay swamps are dominated by sweet bay (M. virginiana), loblolly bay (G. lasianthus),
and, to a lesser extent, swamp red bay (Persea palustria). Other species sometimes reaching
canopy stature include: wax myrtle (M. cerifera) and dahoon holly (llex cassine). The
understory often resembles a thicket dominated by wax myrtle (M. cerifera), fetterbush (L.
lucida), and vines like wild grape (Vitisis rotundifolia) and catbrier (Smilax laurifolia).


Cypress Swamps Cypress swamps are probably one of the most common forested
wetlands in Florida. When circular in shape and isolated they are called cypress domes. When
elongated and exhibiting sluggish surface-water flow in nondistinct channels, they are called
cypress sloughs; and when surface flows are evident but still without distinct channels, they are
referred to as cypress strands. Riverine cypress occupy the margins of channelways of streams
and rivers. Growth rates, density of trees and basal area in cypress wetlands all seem to
increase with increasing hydrologic function (amount and pulses of flooding) and access to
nutrients. For instance, cypress domes have the smallest trees and lowest growth rates while
riverine cypress swamps have largest trees and highest growth rates.
Cypress domes, sloughs, and sometimes strands are dominated by pond cypress (T.
ascendens) while riverine swamps are more characteristically dominated by bald cypress (T.
distichum). Other trees sharing the canopy include black gum (N. sylvatica), pond pine (P.
serotina), slash pine (P. elliottii), red maple (A. rubrum), and one or more of the bay species.
The understory can be relatively diverse having fetterbush (L. lucida), wax myrtle (M.
cerifera), dahoon holly (/. cassine), buttonbush (Cephalanthus occidentalis), Virginia willow
(Itea virginica) and numerous others.
Cypress domes, sloughs and strands are quite common throughout the GSRCT. Although
many show successional trends and the effects of earlier logging to the extent that they are now
co-dominated with other tree species, some have only remnent cypress trees. The large
headwater swamp called the Devils Creek Swamp and portions of the swamp associated with the
Withlacoochee River are extensive stands of cypress.
When the dominance of cypress gives way to other species, especially in riverine
floodplain swamps, the community is classified as a mixed hardwood swamp.











Mixed hardwood swamp When hydroperiods are short, inundation is moderate, and
ground topography is relatively rough, the diversity of plant species that can colonize, survive
and grow is richer. Mixed hardwood swamps have the highest diversity of the forested wetland
communities, primarily as a result of the variation in hydrologic regimes of "micro-sites"
within the wetland.
The canopy in these wetlands is a rich assemblage of hardwood species and cypress such
that no single species dominates. Canopy species include: red maple (A. rubrum), water tupelo
(N. aquatica), swamp black gum (N. sylvatica var. biflora), sweet gum (L. styriciflua), bald
cypress (T. distichum), pond cypress (T. ascendens), pop ash (F. caroliniana), Florida elm (U.
floridana), cabbage palm (S. palmetto), sweet bay (M. virginiana), and loblolly bay (G.
lasianthus). The understory is similar to cypress swamps.
The preponderance of mixed hardwood swamps are associated with the riverine swamps
of the floodplain of the Withlacoochee River and Devils Creek Swamp, although there are
numerous isolated wetlands that resemble cypress domes or strands but, because of hydrologic
conditions, historic logging, and possibly fire frequency, have mixed canopies. Changes in
hydrology and fire frequency can be the result of natural or anthropogenic forces.


Wet prairies Surrounding many forested wetlands in a transitional zone from several
meters to as much as 50 meters wide, and in isolated depressions, wet prairies are found. Wet
prairies are essentially treeless wetlands inundated for short periods of time, and often ravaged
by fire. Wet prairies often occur on mineral soils and do not exhibit accumulations of organic
matter; however, when fire is not a recurrent element, minor organic accumulations may
occur. Wet prairies are maintained by high water tables, infrequent inundation, frequent fires,
and recently, by heavy grazing. While grazing may have the effect of maintaining wet prairie
ecosystems, the impacts of selective foraging by cattle cause obvious shifts in species
composition. Changes in groundwater table elevations as a result of "improved drainage" are
particularly detrimental to wet prairies, often eliminating them entirely from the landscape
after only two dry years. The communities that replace wet prairies under these conditions may
be the grassy-scrubor pine flatwoods if seed source is available and fire frequency is low.
St. John's wort is often the only woody species present in the wet prairie. Sometimes on
the drier margins dense stands of wax myrtle (M. cerifera) may grow to heights of 4 meters or
more. There is a wide variety of herbaceous species associated with wet prairies including:












grassy arrowhead (Sagittaria graminea), pipewort (Eriocaulon decangulare), capitate beaked-
rush (Rhynchospora microcephala), mermaid-weed (Proserpinaca pectinata), yellow-eyed
grass (Xyris caroliniana), bloodroot (Lachnanthes caroliniana), red ludwigia (Ludwigia
repens), Virginia chain-fern (Woodwardia virginica), Baldwin's spikerush (Eleocharis
baldwinnil), maidencane (P. hemitomon), water smartweed (Polygonum punctatum), (Pluchea
rosea), (Cyperus spp.), and water pennywort (Hydrocotyle umbellata).
Wet prairie communities are common throughout the northeastern portions of the GSRCT
as well as isolated areas scattered throughout the central portions.


Shallow marshes Where inundation is more frequent, depths of inundation are around
0.5 meter, and fire is somewhat less frequent than in wet prairies, shallow marshes are
common. With deeper inundation, longer hydroperiods and accumulations of organic matter,
broad-leaved marshes occur (sometimes called flag ponds) dominated by the following species:
pickerelweed (P. cordata), arrowhead (Sagittaria spp.), fire flag (T. geniculata), and cattail
(Typha, spp.). Dominant in the grassy shallow marshes are sawgrass (C. jamaicense),
spikerush (E. cellulosa), soft rush (J. effusus), bulrush (Scirpus spp.), and maidencane (P.
hemitomon), to name but a few.
Shallow marshes are not common throughout the tract. Where they appear, they are
isolated flatwoods marshes scattered throughout the GSRCT.


Deepwater marshes Where hydroperiods are long, and depths of inundation greater
than 0.5 meter to a much as 1 meter, deepwater marshes prevail. Often found as deeper pools
within other wetland systems (including forested wetlands) they are usually dominated by free-
floating plants such as water hyacinth and water lettuce if nutrients are high, or rooted aquatic
plants such as water lily and spatterdock in lower nutrient conditions.
The extent of deepwater marshes is quite small and relatively local in occurrence. Their
spatial distribution within the tract is confined to areas along and in conjunction with the
Withlacoochee River.


Current Uses and Management
Currently, the GSRCT is used for a variety of activities including: grazing, hunting,
hiking, and fishing. Until very recently, nearly half of the tract was leased to private interests












for cattle grazing (Figure 2). The largest cattle lease (now discontinued), found in the
northwestern corner, consisted of 8,320 hectares (20,550 acres) with a stocking rate of
approximately 500 head of cattle. A 598 hectares (1,478 acre) parcel along the southwestern
border maintains 70 head of cattle. Other grazing areas throughout the Swamp total
approximately 770 hectares (1,900 acres). Cattle are not currently maintained on these
parcels, but the parcels have grandfathered leases; in addition, many of the fences and cross
fences remain within the tract (K. Tully SWFWMD, personal communication). The GSRCT is
used for a range of recreational activities. Hunting and fishing activities take place in the
Wildlife Management Area. Generally, there are three hunting seasons throughout the year;
general gun season (mid November through early January), spring turkey season (mid March
through late April), and fishing and frogging season (early May through late June). Harvested
species included fish and frogs, deer, squirrels, hogs, rabbits and turkeys. Other human uses
include: picnicking, hiking, and sightseeing. The Florida Trail crosses the GSRCT (Figure 4).
Management of the GSRCT is accomplished by both the District and the Florida
Game and Fresh Water Fish Commission. The Districts management is guided by SWFWMD
Board Policy, which states:
District-owned lands shall be managed and maintained in an environmentally acceptable
manner and, to the extent practicable, in such a way as to restore and protect their
natural state and condition. (District Policy #610.3)
District management consists of reestablishing and maintaining the ecological
communities of the tract. This is accomplished, in fact, using three management techniques: site
preparation of previously logged over areas, planting and release harvests of tree species and
control burning. In recent years (since 1989) control burning has been conducted in both
growing and dormant seasons. Approximately 2,024 hectares (5,000 acres) of previously
clear-cut (by original ownerss) flatwoods are being restored. With the absence of overstory
pine, understory vegetation had become dominant and thus site preparation consisting of
burning and chopping is necessary before planting in pine species. Higher, better drained sites
are now being planted in long leaf pine, while the less well drained sites are planted in slash
pine. The district has recognized the need for alternative configurations and spacing of planted
pines, using wider spacing to accommodate higher understory productivity. Some lands are
being planted randomly rather than by machine planting in straight rows.












The Florida Game and Fresh Water Fish Commission manages all aspects of hunting by
managing the tract as a Type I wildlife management area. Of the wildlife species that are
harvested, the three most important species (both in terms of their numbers and their relative
impacts on the ecological systems of the tract) are: deer, feral hogs, and turkey.
In terms of areal extent, control burning is the current dominant management strategy
of the area. Burn control lines are maintained along the SWFWMD property boundaries and
roadways (Figure 5). The control lines are maintained at varying widths with a tractor-pulled
disc plow. Lines along the perimeter are disced annually at a width of 6 to 7.6 meters (20-25
feet) and interior lines are plowed bi-annually 4.5 to 6 meters (15-20 feet) wide (K. Tully,
personal communication). The objectives of the fire control lines are to protect against
wildfires and to control prescribed burns. Prescribed burns in most areas are generally
conducted on a 3-4 year rotation, with some areas burned less frequently. There have been
numerous small wild fires as well as one major wild fire in 1980 which burned approximately
4,860 hectares (12,000 acres) of land (Figure 6).



Plan of Study


The plan of study was to develop a computer aided inventory and management system for
natural area reserves. A methodology was developed and tested that could be used to rank areas
of a reserve relative to the heterogeneity of the mosaic of ecological communities (ie landscape
diversity or richness) and to determine habitat suitability for wildlife species taken
individually, and then as a whole by combining individual results. The methodology used a data
base of land cover of the Green Swamp Riverine Corridor Tract and manipulated the data base
using a Geographic Information System (GIS).
More specifically, the project was organized into two phases. First, the entire tract was
quantitatively surveyed and areas of greatest community diversity and richness were evaluated
using measures of diversity, richness, complexity and power density. Second, habitat
suitability of the mosaic ecological communities was evaluated for several representative
wildlife species separately and combined to evaluate composite wildlife habitat suitability. The
wildlife species were: the white tailed deer (Odocoileus virginianus), southeastern American
kestrel (Falco sparverius paulus), red cockaded woodpecker (Picoides villosus), Eastern indigo












snake (Drymarchon corals couperi), American alligator (Alligator mississippiensis), wild
turkey (Meleagris gallopavo), river otter (Lutra canadensis), Florida sandhill crane (Grus
canadensis pratensis) and raccoon (Procyon lotor). These species represent a diverse
assembledge chosen on the basis of meeting one or more of the following criteria: their
commonness, economic significance (game species), special needs, and endangered or species of
special concern. Home range and habitat data are not readily available for most wildlife, and for
the most part, were unavailable for other species.
Once habitat suitability and landscape heterogeneity were evaluated, suggestions for
management and protection of existing values were generated based on identification of
conflicting uses. Conflicting uses were identified by overlaying landscape heterogeneity and
wildlife suitability with present uses and management actions. In addition to evaluations of the
existing wildlife habitat suitability, an attempt was made to evaluate potential habitat
suitability using soils as a surrogate for potential ecosystem development. Ultimately, after
analyzing the results of the potential habitat suitability, it was concluded that soils were not a
good surrogate for ecological communities because community succession can take any number
of different pathways depending on such variables as fire frequency, soil moisture, and human
interference. While the analysis for potential habitat suitability was conducted, the results of
the analysis are not presented in this document.








29








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METHODS


Overall, the methodology involved the generation and manipulation of map coverages and
spatial data bases in ARC/INFO. The map coverages included land use/ land cover, soils, and
several cultural features. Wildlife habitat suitability was evaluated using the land use/ land
cover map coverage. For comparison with present land use and land cover, potential habitat
suitability was evaluated using the soil map coverage and assuming climax communities based on
soil classifications. Cultural features and management units were used as a means of evaluating
present and future management options.


Map Coverages


ARC/INFO is a geographical information system (GIS) which incorporates computer
mapping and data base management. Both graphic and nongraphic data are used. The data base
includes spatially oriented information which can then be analyzed, stored, retrieved, and
collected to present as geographical data. ARC/INFO uses a set of features describing
geographical areas called a coverage. This coverage is linked to a table which stores current
information on each of the features.


Land Use and Land Cover
Land use and land cover were mapped and ARC/INFO coverages created from 1983 aerial
photography at a scale of 1:2000 by the SWFWMD for the majority of the GSRCT. The
classification system for land use/land cover was developed by the SWFWMD and is given in
Table 1. The minimum mapping unit was approximately two hectares (5 acres). Several
sections of land were purchased and added to the tract subsequent to the land cover mapping done
by the District. These areas, totalling about 9 sections in the northwest corner of the tract and
2 sections along the southern boundary were photo interpreted from 1:2000 false color
infrared photography using the District classification system. Once interpreted, additional
areas were digitized and intersected with the old vegetation coverage.


1












Soils and Potential Land Cover
Soil maps for Polk, Lake, and Sumter counties at scales of 1:20000 were digitized and
soil types labeled consistently between the counties. Land cover classification codes were
assigned to each soil type, based on vegetation characteristics described in each county soil atlas.
The assigned land cover types represented the potential climax community, assuming
management strategies favorable to climax communities. The vegetation classes were derived
from the land use classifications provided by the SWFWMD. Table 2 lists soils by name and the
assigned land cover classification code.


Cultural Features
Dirt roads, locations of prescribed burns, wildfires, and cattle leases were mapped from
data provided by the SWFWMD. Separate ARC/INFO coverages were created for each of these
features. Rivers, creeks, and unnamed ditches along roads and railroad tracks were digitized
into ARC/INFO from USGS topographic maps of the area. From a map provided by the Florida
Trails Association, the portion of the Florida Trail which crosses the GSRCT was digitized to
create a trail coverage.


Evaluation of Landscape Heterogeneity


Analysis of the land cover mosaic to derive maps of landscape diversity was conducted
using several measures of diversity. Normally diversity is calculated at the community level
using species data. Landscape diversity however, was derived using ecological communities
instead of species in the various measures commonly used for the smaller scale analysis of
community level data.
Measurement of landscape diversity was accomplished by dividing the tract into cells
(sampling frames) and calculating indices of diversity within each cell. Cell size was
determined by analysis of the spatial data base by graphing number of polygons per unit area on
cell size. The objective was to choose a sample frame size that was neither too small to miss
most landscape scale diversity, or too large so as to mask landscape heterogeneity. The sampling
frame size is obviously some function of the average size of units and the 'texture' or frequency
of units within the landscape.












To measure influence of sampling frame size, cells of increasing size were placed at the
center of the tract and the number of polygons of land cover were tabulated within each. The
resulting data were graphed as shown in Figure 7, where the x axis is area of cell and the y axis
is sampling efficiency. Sampling efficiency is defined as:


SE =1 -(N / A) (1)
where:
N = number of polygons within the cell
A = area of the cell


The resulting curve of sampling efficiency (Figure 7) shows a marked change in slope at
around 240 280 hectares (600-700 acres). Sampling efficiency drops off markedly in cells
with areas greater than 280 hectares (700 acres), while cells having areas of less than 700
acres exhibit increasing sampling efficiency. The graph of sampling efficiency is an attempt to
relate both the number of units (polygons of land cover) and average size of units to a sample
frame size.
Based on the analysis of sampling frame size, landscape scale diversity indices were
calculated using a sampling frame size of 260 hectares (1 mi.2). The entire GSRCT was
overlaid and intersected with the 260 hectare (1 mi.2) grid resulting in each cell having a
unique set of land cover polygons. To account for cell location and possible biases resulting from
cell placement, the grid of cells was moved northwest 1/3 of the cell size and then again
northwest 1/3 of the cell size (Figure 8). With each move, the land cover was intersected, so
that in the end a total of 3 intersections and thus three sets of data were analyzed for the various
measures of landscape diversity.
Several measures of diversity used in analysis of community level data, broadly termed
indices of complexity were employed to rank portions of the tract. These measures were
calculated using land cover types in place of species, and included Simpson's Diversity,
Shannon/Weiner Diversity, and Dominance.
In addition to these measures of diversity, two new indices were calculated; Complexity,
and Power Density. Each index is defined next.












Simpson's Diversity A measure of diversity that gives relatively little weight to the rare
species (communities) and more weight to the common species. Simpson's index of diversity is
equal to probability of picking two organisms at random that are different.
The formula for Simpson's diversity is:
s 2
D = 1 (p) (2)


where
D = Simpson's index of diversity
pi = proportion of individuals of species i in the community
S = number of species
In this application to landscapes, ecological communities are used in place of species. A total
Simpsons diversity index for each cell was calculated and all cells ranked from highest to
lowest. The 30 highest ranking cells were selected and displayed as a map coverage.


Shannon-Wiener Diversity Two components of diversity are combined in this measure:
number of species and equitability or evenness of allotment of individuals among the species. A
greater number of species will increase species diversity, and a more even or equitable
distribution among species will also increase species diversity measured by the Shannon-
Weiner function. The formula for Shannon-Weiner diversity is as follows:



H=-o (p)(logp) (3)
i 2 i

where:
H = information content of sample (bits/individual) = index of species diversity
S = number of species
pi = proportion of total sample belonging to ith species


In this application to landscapes, ecological communities are used in place of species. A total
Shannon diversity index for each cell was calculated and all cells ranked from highest to lowest.
The 30 highest ranking cells were selected and displayed as a map coverage.












Dominance Dominance is related to the concept of species diversity, but inversely related to
diversity. As the number of species increases, dominance decreases. Dominance is defined as
percentage of abundance contributed by the two most abundant species. The formula for
dominance is as follows:


D= 100 x (yl -y2)/y (4)

where:
yl = abundance of most abundant species

y2 = abundance of second most abundant species

y = total abundances of all species


In measures of community dominance, abundance is measured by density, biomass or
productivity. In this application to the landscape scale, abundance is measured by numbers of
ecological communities per unit area. A total dominance for each cell was calculated using
equation 4 and all cells ordered from lowest to highest. The 30 highest ranking cells (lowest
dominance values) were selected and displayed as a map coverage.


Complexity Complexity is a measure of the total edge within a grid cell and is defined as the
ratio of total perimeter (in meters) divided by area (in hectares). A total complexity index for
each cell was calculated and all cells ranked from highest to lowest. The 30 highest ranking
cells were selected and displayed as a map coverage.


Power Density Power density is the rate of useful work per unit area. The rate of useful
work in ecological communities is expressed as Gross Primary Production (GPP). Previous
studies of Florida ecosystems (Brown, 1980) established average estimates of GPP from the
literature. Power densities are measured in solar emjoules per acre. A solar emjoule is the
equivalent solar energy (measured in joules) required for GPP. Total power density in each
cell was calculated by multiplying power density of each community type by the area of each
type and summed. The 30 highest ranking cells were selected and displayed as a map coverage.


Evaluation of Habitat Suitability












The evaluation of wildlife habitat suitability was conducted using the land use/land cover
and soils data bases. First existing habitat suitability was determined using present land
use/land cover and then for comparative purposes potential habitat suitability was determined
using the soils data base as an alternative to potential land cover.
The procedure for determination of wildlife habitat suitability involved first calculating
habitat value of the mosaic of ecosystems using a grid of varying size (dependent on the home
range of each animal) and then ranking each habitat cell based on species specific habitat
requirements.
Evaluation of habitat suitability was derived by evaluating the presence of selected land
cover types within cells on a cell by cell basis over the entire tract. Cell size varied for each
animal and was based on home range size. A grid based on appropriate cell size for each species
was superimposed and intersected with the vegetation coverage using the tract's northwestern
tic location as the intersection point. To test for locational variability that may bias results,
each grid was subsequently moved 1/3 cell width up and off center, and then again 1/3 cell
width up and off center. With each move, the land cover was intersected, so that in the end, a
total of 3 intersections and thus three sets of data were analyzed for each species habitat
suitability. All cells from the three intersections were then ranked from best fit to worst fit.
The final selection resulted in a minimum of 9 cells, and maximum of 15 cells that best met all
habitat requirements for each species. The method for ranking habitat values of cells are
described next.


Calculation of Habitat Values
Habitat value of the landscape mosaic of ecological communities was determined by
evaluating the mosaic through the use of cells whose size were determined by the home range of
each species. The habitat requirements (feeding, breeding, or nesting requirements) for each
species were researched from the literature and became the basic variable upon which the
evaluation was based. These data are given in Table 3.
Each species had habitat values calculated in the following manner. First, home range for
the species was determined from best estimates in the literature, often resulting from the mean
of several reported values (column 2 in Table 3). Second, the entire GSRCT was overlaid with a
grid whose size was equal to the home range. Third, the land cover data base was intersected with
the grid resulting in each grid having a unique set of land cover types. Fourth, the grid of cells












were moved northwest 1/3 of the cell size and then again northwest 1/3 of the cell size (Figure
8). After each move, the land cover within each cell was summarized by land cover type. By
repeating the cell shift twice, artificial results due to cell location were eliminated from the
evaluation. Fifth, each cell was reviewed and those cells containing the appropriate mix of
ecological communities as dictated by the literature obtained habitat requirements (column 3 in
Table 3) were selected. Finally, a maximum of five cells were ranked based on the criteria
discussed next.


Ranking Criteria
Once habitat values of animal home range cells were determined, they were ranked
according to how well they met habitat requirements. To minimize the number of cells in the
final selection, a maximum of five of the highest "scoring" cells for each species were retained
as candidates for optimum habitat areas. Each species had specific ranking criteria that were
both qualitative and quantitative. A discussion of these criteria follows.
Selection of the most suitable habitat cells in each run of the analysis was based on the
three criteria that were aimed at attaining the best match with habitat requirements. In some
cases habitat data obtained from the literature gave specific spatial requirements of each land
cover type or time spent in different types; in others the literature was rather oblique. Where
the literature was relatively specific, the first criteria was that selected cells must have the
required proportions of habitat types. Where the literature was vague, the selection process
became relatively qualitative; the first criteria being that there was an even mix of required
land cover types. In other words, cells that had only a few acres of one or more required land
cover types were eliminated in favor of those that had a "balance." The second criteria was that
selected cells had the largest quantity of required land cover types in the proper proportions
(where this data were known). The final criteria was that the required habitat types must
cover at least 20% of the home range size. In addition to these three general criteria, specific
criteria for several species were also used and are given next.


Deer- The literature suggested no preferential habitats for the deer, therefore, optimum
habitat areas were home range cells which had an even mix of required habitat. This meant that
cells that were either dominated by or almost deficient in one or several of the required habitat
types were "scored" low.










37

Kestrel- The literature did not place more importance on either the pine flatwoods or
rangeland/pasture for the kestrel. Therefore, cell areas which did not display a
disproportionate amount of one land cover type over the other were considered. To narrow this
selection further, the cells of the greatest amount of acreage comprised the final mapped area.


Red cockaded woodpeckers- Red cockaded woodpeckers show a habitat preference of pine
flatwoods among the required habitats. Therefore, this land cover comprised the majority of the
grid section followed by cypress and wet prairies.


Indigo snake- The selection of home range cells for the indigo snake was based on the presence
of required habitat types where no one land cover dominated.


Alligator- Selections for the alligator were determined using only the first two steps in the
ranking process; all required habitat types must be present and the habitat types need to cover
20% of the home range cell size.


Turkey- The amount of open space, which refers to rangeland and pasture, within the turkey
home range cells was calculated. The optimal open space is 10%-50% of the total home range
cell size. The remaining cells were analyzed in terms of the acreage for each of the land cover
types. Those cells which showed a more even distribution of habitat types were retained.


River otter- River otter selections consisted of home range cells with the required habitat
types distributed evenly.If one land cover dominated, the amount of total acreage would have to
be a large amount in order for that particular home range cell to be selected.


Sandhill crane- Areas for sandhill crane selections were ranked by two factors: first, if
required habitat types were evenly distributed, and second, the amount of freshwater marsh
available. The cells having the largest area in freshwater marshes were "scored" higher than
other home range cells.


Raccoon- Raccoon habitat areas were chosen on the basis of the presence of and relatively even
distribution of required habitat types.













Evaluation of Potential Habitat Suitability


Potential landscape suitability was derived through the use of soil map coverage as a
surrogate for potential ecosystem development. Soils data were mapped and then used to develop
a map of a landscape mosaic of climax ecological communities assuming management strategies
that foster these communities. The procedures used in the evaluating of existing wildlife habitat
suitability were rerun using as land cover data, the potential landscape mosaic derived from the
soils map coverage.


Deriving Potential Land Cover


Potential was derived from the soils coverage. Climax ecosystem development on each of
the soil types of the GSRCT was taken from USDA (1975, 1988, 1988a) and SCS (1987) as
given in Table 2. These community types were used as the land cover data base for evaluation
of potential habitat suitability, assuming management strategies that allow development of
climax communities. There are several important omissions from assigned land cover.
Rangeland, pasture, wet prairies, and riverine cypress were not assigned classifications. The
first three land cover types are not climax communities, but are the result of human
management (rangeland and pasture) and natural factors (wet prairies) that maintain these
areas in some "early successional" state. Riverine cypress is a variant of the riverine mixed
hardwood swamp. The forces acting to develop "pure" stands of cypress verses mixed stands are
not entirely understood. They may be the result of anthropogenic, edaphic, or other factors.
Consideration of these factors in developing the climax community land cover data base from
soils was beyond the scope of this study. Habitat suitability was analyzed using potential land
cover with the same methods employed for the existing land cover types. In brief, first habitat
values were determined using home range cells that were intersected with the soils based climax
land cover types. Then qualitative ranking of cells was conducted to yield a selection of cells that
were most suitable for each species assuming the climax land cover.









39

Map Coverages of Landscape Diversity and Habitat Suitability


Spatial data manipulation and intersections were conducted using a Pc based version of
ARC/Info. Output files of selected cells for both landscape diversity and wildlife habitat
suitability were generated and converted to raster maps suitable for MAPII (a Macintosh based
map processor, [Pazner et al, 1989]). The raster coverages and the MAPII software make data
manipulation extremely easy, requiring at least 1/100th the time required by Pc based
ARC/Info. Map coverages included in this report were produced using the MAPII map processor.












RESULTS


Results of spatial data manipulations are presented as raster maps at a scale of
1:283465 for convenience of presentation and the manipulation of data. The loss of visual
acuity is not a loss of accuracy, since the raster maps were generated from the vector based
ARC/Info coverages. The ARC/Info coverages are part of this report, and full scale maps can be
generated from these data for finer scale resolution and presentation.


Spatial Distribution of Ecological Communities


Figures 9 through 13 show the spatial distribution of ecological communities in the
GSRCT. Community types are grouped together in logical groupings to simplify presentation.
Shown in Figure 9 is the pine flatwoods map including both Pine Flatwoods (slash and
long leaf [52, 53]), the darkest areas, and pine plantations (slash pine [51, 541), the medium
gray areas. Total area of pine flatwoods and planted pines,combined, was about 3,040 hectares
(7,570 acres). The largest concentration of contiguous pine flatwoods were in the southern
portion of the tract bordering the Withlacoochee River and the northern end of the panhandle.
Figure 10 is a map of the spatial distribution of hammock communities. The map
includes low temperate (23, 61), and upland temperate (62) hammocks, as well as upland
hardwood forest (63,83). Each of the classifications are shaded differently, but because of
their small size differences are not visible. The areas of low temperate, upland temperate
hammocks and mixed hardwood forest combined was 350 hectares (880 acres).
The greatest spatial concentration of wet prairies and marshes was in the northeast
quadrant of the tract as shown in Figure 11. Shown in the map are wet prairies (42) and
freshwater marshes (35, 36, 41). The total area of wet prairies and freshwater marshes,
combined was 2,990 hectares (7,390 acres).
Cypress (31) and mixed hardwood swamps (32,33,34) are shown in Figure 12. Much
of the central portion of the tract is dominated by the cypress ecosystems as is much of the
panhandle. Because of the small size of many of the isolated cypress and mixed hardwood
wetlands, the rastorization may have increased the areal extent of these systems. Measured
areas of the two communities from the rastor map combined was 9160 hectares (22,630
acres).












Figure 13 shows the spatial distribution of riverine cypress swamps (21) and riverine
mixed hardwoods (22, 24, 26). The riverine systems of the Withlacoochee and Devils Creek
are shown. The total area of riverine swamps was 3,784 hectares (9,350 acres).


Landscape Diversity
Given in Table 4 are the results of analysis of the Green Swamp Riverine Tract for the
various measures of Landscape Diversity. In the first column the cell name and number are
given; numbered consecutively from 2 to 53. Several cell numbers are missing because they
fell outside of the tract boundaries, due to its irregular shape. The second column gives the total
number of polygons. In the third and fourth columns area and total perimeter length are given
in hectares and meters respectively. The fifth and sixth columns give Simpson's and Shannon-
Weiner Diversity, while the seventh column gives dominance. The eight column gives
complexity, as measured using perimeter divided by area. The ninth column gives Landscape
Development Intensity, and the final column gives power density.
Maps have been generated depicting the 30 highest "scoring" cells for each of the
following indices: Simpson's diversity, Shannon-Weiner diversity, Dominance, Complexity,
and Power Density (Figures 14 through 19). The highest scoring cells were not always those
with the highest absolute scores. Where the diversity index was biased by a smaller area
(complexity) cells that were not close to full size (1mi2) were eliminated.
Figure 14 is a map of Simpson's diversity, depicting the 30 highest scoring cells for
that parameter. The darker the tone of a cell, the higher its score. There were 6 groupings of
cells having high Simpsons diversity, mostly associated with the complex associations of plant
communities that transition from the riverine wetlands to uplands. They were (clockwise from
the northeast corner): Gator Hole and areas northeast, the Withlacoochee swamp at the railroad
crossing, the Withlacoochee swamp north of Kinsinger road, the area southwest of Strand
hammock, the area north of Stanley Fish Hole, and the area west and northwest of Devils Creek
Swamp. Those areas having the highest Simpsons diversity were: the Withlacoochee swamp
north of Kinsinger road and the area north of Stanley Fish Hole.
Figure 15 depicts the highest scoring cells for Shannon-Weiner Diversity. In general
the highest Shannon diversities were found adjacent to the Withlacoochee River. Clockwise from
the right, they were: the Withlacoochee swamp at the railroad crossing, the area north of Orange
Lake, the area southwest of Strand hammock, and the area north of Stanley Fish Hole. Highest












diversities were found in the Withlacoochee swamp at the railroad crossing and north of Stanley
Fish Hole.
Given in Figure 16 are the lowest scoring (highest ranking) cells for dominance. Since
dominance and diversity are most generally inversely related; that is, when dominance is lowest
diversity is highest, these maps depict the lowest scoring cells. Lowest scoring cells were
clustered along the flatwoods/cypress dome association in the northeast quadrant of the tract,
southwest of Gator Hole.
Figure 17 shows the 30 cells having the highest complexity index. The highest landscape
complexities were found in the area of wet prairies, marshes and pine in the northeastern area
of the tract bordering Gator Hole. Secondary concentrations of landscape complexity were found
immediately north and south of the Withlacoochee River in areas of extreme interdigitation of
cypress and pine.
Power density is given in Figure 18 showing the 30 highest scoring cells. The areas
with greatest power density and therefore gross production were clustered around the
Withlacoochee River in the southern portion of the tract. Nearly 90% of the highest scoring
cells were clustered in this area.
The measures of landscape diversity using Simpson's diversity, Shannon-Weiner
diversity, in general, were highest in the transitional areas bordering the Withlacoochee River,
with a secondary area in the vicinity of the Devils Creek Swamp. Dominance and complexity on
the other hand were highest in the flatwoods/cypress dome and flatwoods wet prairie and marsh
associations where interdigitation between these communities was greatest. Power density was
highest in much of the same area as the indices of diversity.
A composite map of the diversity indices is given in Figure 19. There were three areas
of greatest diversity: (1) the area surrounding the Withlacoochee River where lands transition
from riverine swamps to the drier hammocks and flatwoods, (2) the area of cypress, wet
prairie and flatwoods ecosystems in the northeastern portion of the tract, and (3) an area in the
northwest surrounding and including the Devils Creek Swamp.


Evaluation of Habitat Suitability


In this section results of the analysis of wildlife habitat suitability are given. Wildlife
habitat suitability was determined on a cell by cell basis for nine wildlife species using home












range and habitat requirements derived from the literature. The results of the evaluations
using the land use/land cover map coverage are given as habitat units for each species; where a
habitat unit is a single cell or group of contiguous cells composed of required habitat types. A
habitat unit should not be confused with the minimum area necessary to support a given animal,
or population. There is much discussion in the literature concerning minimum viable
populations and the area necessary to support them. Since habitat units were derived from
home range data there is nothing in the analysis that would suggest wildlife carrying capacity of
these areas. Carrying capacity is a function of the productivity of the landscape; determinations
of the quality of the landscape and thus productivity were beyond the scope of this study. As a
result, the selected habitat units are nothing more than areas that have the required ingredient
s preferred by a given species. It can be surmized that the larger the habitat unit and the
greater the area of the required habitat types, the greater the carrying capacity of the unit.
Map coverages showing the habitat units having the highest wildlife suitability are given
in Figures 20 through 29 for each wildlife species. The following paragraphs summarize the
results of the evaluation and ranking.


White tailed deer
Habitat units having the most suitable mix of required habitat types for the white tailed
deer are given in Figure 20. These selections include the required land cover types: mixed
hardwood swamps, riverine mixed hardwood swamps, freshwater marsh, and pine flatwoods.
Each home range cell was 260 hectares (640 acres). There were three areas of the required
habitat mix, all located north of the Withlacoochee River. The single cell toward the west side of
the property had a total of 83 ha(204 acres) of the required habitat types (Pine flatwoods= 38
hectares (93 acres), freshwater marsh= 3 hectares (8 acres), mixed hardwood swamps=6
hectares (15 acres), and riverine hardwood swamps= 36 hectares (89 acres)). The habitat
unit in the central portion of the tract had a total of 367 hectares (907 acres) of required
habitat types (pine flatwoods= 113 hectares (280 acres), freshwater marsh=46 hectares
(110 acres), mixed hardwood swamps= 27 hectares (67 acres), and riverine mixed hardwoods
swamps= 182 hectares (450 acres)). On the east side of the property, the selected habitat unit
totaled 344 hectares (850 acres) of required habitat types (pine flatwoods=52 hectares (129
acres), freshwater marsh= 10 hectares (24 acres), mixed hardwood swamps=76 hectares
(187 acres), and riverine mixed hardwood swamps= 205 hectares (507 acres)).













Southeastern American Kestrel
Required habitat types for the kestrel included pasture/rangeland, and pine flatwoods.
Highest ranking habitat units (Figure 21) were scattered throughout the study area as both
single and contiguous groups of habitat units. Three contiguous habitat units were found along
the north, southeast, and west property boundaries. The habitat unit along the northern
boundary contained three home range cells having a total of 153 hectares (378 acres) of
required habitat types (pine flatwoods= 73 hectares (180 acres) and rangeland= 80 hectares
(198 acres)). The habitat unit located in the southeastern corner of the tract totaled 130
hectares 322 acres of required habitat types (rangeland= 57 hectares (140 acres) and pine
flatwoods= 73 hectares (182 acres). The habitat unit in the western portion of the site was
composed of 2 home range cells and totals 132 hectares (326 acres) of required habitat
(rangeland= 87 hectares (214 acres) and pine flatwoods= 85 hectares (211 acres)). If the
isolated cell immediately above this habitat unit were added, the total area of required habitat
within the combined 3 cell area would be 179 hectares (441 acres). The remaining two single
habitat units have 55 hectares (137 acres) (top) and 56 hectares (138 acres) (bottom) acres
of required habitat types.


Red Cockaded Woodpecker
Figure 22 shows highest ranking habitat units for the red cockaded woodpecker. Each
cell represents a home range of 198 hectares (490 acres). Required habitat types include pine
flatwoods (and plantations), cypress swamps, and wet prairies. There were three single habitat
units found in the north central portion of the tract, in the western portion of the tract border,
and in the southern panhandle. These areas totaled 123 hectares (304 acres), 182 hectares
(450 acres), and 79 hectares (194 acres) of required habitat types, respectively. Habitat
units composed of two or more home range cells were located in the central area of the tract,
the south central portion of the tract the northern end of the panhandle and along the
southern border of the property The habitat unit in the central portion of the site consisted of
70 hectares (173 acres) of pine flatwoods, 65 hectares (161 acres) of cypress, and 7hectares
(18 acres) of wet prairies totaling 143 hectares (352 acres). Total area of the south central
habitat unit was 313 hectares (773 acres), composed of 135 hectares (333 acres) of pine
flatwoods, 167 hectares (412 acres) of cypress, and 11 hectares (28 acres) wet prairies. The












habitat unit at the northern end of the panhandle totaled 330 hectares (815 acres) of required
habitat types as follows: 190 hectares (470 acres) of pine flatwoods, 127 hectares (314
acres) of cypress, and 13 hectares (31 acres) wet prairies. The habitat unit along the
southern border had a total of 163 hectares (403 acres) of required habitat types consisting of
72 hectares (179 acres) of pine flatwoods, 90 hectares (223 acres) of cypress, and 0.4
hectares (1 acre) of wet prairies.


Eastern Indigo Snake
The Eastern indigo snake had home range cells of 224 hectares (553 acres) that included
riverine mixed hardwood swamps, mixed hardwood swamps, pine flatwoods, low temperate
hammocks, and upland hardwood forests (Figure 23). The majority of the highest ranking home
range cells were concentrated in a large habitat unit totaling 333 hectares (822 acres) of
required habitat types located along the southern boundary of the tract. The habitat unit was
composed of the following areas of habitat types: 119 hectares (295 acres) of pine flatwoods,
143 hectares (353 acres) of riverine mixed hardwood swamps, 34 hectares (84 acres) of
mixed hardwood swamps, 35 hectares (87 acres) of low temperate hammocks, and 1.2 hectares
(3 acres) of upland hardwood forests. The two remaining habitat units consisted of two selected
cells in the panhandle composed of 30 hectares (74 acres) of pine flatwoods, 10 hectares (24
acres) of riverine mixed hardwood swamps, 60 hectares (148 acres) of mixed hardwood
swamps, and 21 hectares (51 acres) of low temperate hammocks.


American Alligator
Selected cells for the American alligator, whose home range equaled 891 hectares
(2,200 acres) were in the vicinity of the Withlacoochee River, with contiguous habitat areas
located at the east and west extremes of the tract (Figure 24). The eastern habitat unit
consisted of a total area of 443 hectares (1,093 acres) of required habitat types as follows: 25
hectares (61 acres) of riverine cypress swamps, 311 hectares (767 acres) of riverine mixed
hardwood swamps, and 107 hectares (264 acre) of wet prairies The western habitat unit
totaled 769 hectares (1,899 acres) of required habitat types consisting of 55 hectares (136
acres) of riverine cypress swamps, 318 hectares (786 acres) of riverine mixed hardwood
swamps, and 396 hectares (977 acres) of wet prairies.











Wild Turkey
Habitat units for wild turkey were found over most of the study area (Figure 25) as a
result of its large home range ( 2,024 hectares [5,000 acres] is considered the minimum
management area of game turkeys) and its ubiquitous nature. In the panhandle, areas of
required habitat types totaled 1,721 hectares (4,250) acres as follows: cypress/riverine
cypress swamps (613 hectares or 1,515 acres), pine flatwoods (560 hectares or 1,384
acres), and rangeland/pasture (547 hectares or 1,351 acres). The remaining portion of the
tract contained a total of 9,222 hectares (22,779 acres) of required habitat types, as follows:
cypress/riverine cypress swamps, (4,243 hectares or 10,481 acres), pine flatwoods,
(1,868 hectares or 4,615 acres), and rangelandlpasture, (3,110 hectares or7,683 acres).
The L shaped area in the center of the property probably should be included as a logical addition
to the habitat unit.


River Otter
Required habitat types for the otters, whose home range totaled 318 hectares (785
acres) included cypress/riverine cypress swamps, riverine mixed hardwood swamps, mixed
hardwood swamps, and freshwater marshes. Figure 26 shows three habitat units located along
the Withlacoochee River. The western most habitat unit contained 2 cells totaling 342 hectares
(845 acres) of required habitat types as follows: 114 hectares (282 acres) of
cypress/riverine cypress swamps 215 hectares (530 acres) of riverine mixed hardwood
swamps, 7 hectares (17 acres) of mixed hardwood swamps, and 6 hectares (16 acres) of
freshwater marshes. The central habitat unit was composed of three home range cells totaling
605 hectares (1,495 acres) of required habitat types as follows: (1,136 acres) of
cypress/riverine cypress swamps, (247 acres) of riverine mixed hardwood swamps, 7
hectares (17 acres) of mixed hardwood swamps, and 38 hectares (95 acres) of freshwater
marshes. The habitat unit located along the eastern boundary of the tract was composed of 243
hectares (599 acres) of cypress/riverine cypress swamps 212 hectares (524) acres of
riverine mixed hardwood swamps, 78 hectares (192 acres) of mixed hardwood swamps, and 29
hectares (71 acres) of freshwater marshes. The total area of required habitat types was 561
hectares (1,386 acres).











Florida Sandhill Crane
Habitat units for the sandhill crane represented a large portion of the tract (Figure 27)
due in part to its large home range (1,291 hectares or 3,190 acres) and habitat requirements
for three of the most common community types. The habitat unit, while contiguous can be
divided into two subsections along the Devil Creek Swamp, with the western portion containing
the most important habitat requirements. The total required habitat within the habitat unit was
4,058 hectares (10,023 acres) and was composed of: wet prairies, (1,983 hectares or 4,898
acres), pine flatwoods, (718 hectares or 1,774 acres), rangeland/pasture, (1,171 hectares
or 2,893 acres), and freshwater marshes, (185 hectares or 458 acres).


Raccoon
Habitat types required by the raccoon, whose home range was equal to 100 hectares
(247 acres), consisted of cypress swamps, riverine cypress swamps, riverine mixed
hardwood swamps, freshwater marshes, mixed hardwood swamps, and low temperate hammocks.
Only three home range cells contained the required habitat types (Figure 28), resulting from
the small size of the home range and the ranking criteria that required all habitat types to be
present in more or less equal abundance. The three cell habitat unit in the northwestern
portion of the tract had total habitat area of 239 hectares (591 acres) as follows: 5 hectares
(12 acres) of freshwater marsh, 34 hectares (84 acres) of mixed hardwood swamps, 136
hectares (336 acres) of riverine cypress/cypress swamps, 45 hectare (111 acres) of
riverine mixed hardwood swamps, and 19 hectares (47 acres) of low temperate hammocks.
The two cell habitat unit located centrally along the Withlacoochee River had a total required
habitat area of 118 hectares (292 acres) as follows: 2 hectares (5 acres) of freshwater
marsh, 6 hectares (14 acres) of mixed hardwood swamps, 107 hectares (264 acres) of
riverine cypress/cypress swamps, 1 hectare (3 acres) of riverine mixed hardwood swamps,
and 2 hectares (6 acres) of low temperate hammocks. The single cell habitat unit had a total
area of required habitat types of 90 hectares (223 acres) as follows: 3 hectares (8 acres) of
freshwater marsh, 3 hectares(7 acres) of mixed hardwood swamp, 77 hectares (190 acres) of
riverine cypress/cypress swamps, 2 hectares (6 acres) of riverine mixed hardwood swamps,
and 5 hectares (13 acres) of low temperate hammocks.












Composite Habitat Suitability
Selected habitat cells were overlaid in a composite habitat suitability map given in
Figure 29. The darkest areas had the highest suitability for the largest number of animals. The
three areas scoring highest composite suitability are adjacent to the Withlacoochee River. the
eastern most area is associated with the floodplain swamp near the railroad crossing. Two other
areas are immediately north of the River in its central and western reaches.



Potential Habitat Suitability


Potential habitat suitability was determined by mapping soil types and converting the
soils to land cover types. Less diversity of land cover types per unit area was generated in the
landscape through the use of soils than appeared in the original land cover mapping. The river
otter and white tailed deer were the only species for which all required habitat types were
present using soils generated climax community coverage (see Snyder, 1991). All other species
have at least one required land cover type missing in the potential landscape. Potential habitat
depended on the resolution of the soils maps and on the accuracy of probable climax community
types that would be realized for each soil. We were limited in our analysis by both of these
factors. First, the resolution of soils, that is, their smallest areal extent was not as detailed as
the existing vegetation coverage. Second, there are numerous pathways to climax community
type, and several soils share the same possible climax community. Numerious exogenious
factors, especially fire frequency and severity have a great deal of influence over development
of climax communities. In the end after trying several scenarios of possible climax conditions,
we had to abandon the idea of potential habitat based on soils. What we eventually concluded was
that it is most difficult to match the landscape heterogeneity that is generated by the complex
interaction of humans, fire, drought and seed availability using a simple surrogate like soils
coverage.













Evaluating Conflicting Uses and Management


Prescribed burn units cover most of the GSRCT. Management that includes the use of
prescribed burns has the potential of decreasing the number and severity of wildfires. In
addition many wildlife species benefit from the increased production that follows fire and from
the reduction of mid-canopy vegetation. In general, white tailed deer and wild turkeys benefit
from reduced mid-canopy biomass and the increased foraging opportunities that the fire related
increases in production afford. Florida sandhill crane habitat requires periodic burns to
maintain the quality of the habitat. Wet prairies and shallow marshes (two important sandhill
crane habitats) are believed to require fire on a relatively frequent basis to eliminate shrub
and tree species. The red cockaded woodpecker habitat is enhanced by periodic burns because
midstory vegetation and hardwoods are eliminated. Figure 30 is a map depicting the prescribed
bum overlay with the selected home range cells for the woodpecker. The use of prescribed
burns may, however, decrease habitat quality for some species. The indigo snake requires a
dense understory; therefore, burning may decrease habitat quality for this species (Figure 31).
As better habitat models are developed for Florida wildlife species, additional overlays can be
generated using the data base to aid in management decisions.
Human uses of the GSRCT are primarily passive activities and hunting. The Florida Trail
provides a portion of the passive recreation possible. The Trail crosses through the
Withlacoochee River area. This area is also suited for species which are hunted; deer, turkey,
raccoon, and otter. There is no question that hunting conflicts with passive recreation. At the
present time hunting is confined to areas north of the Withlacoochee River. Conflicts with
passive recreation arise during the hunting seasons of November to January, March to April,
and May to June. In addition to conflicts with other human uses, wildlife species which are
found in this area but are not hunted may still be indirectly effected by the increase in human
use of the area and through human disturbances associated with hunting.
Areas of planted pine are scattered throughout the study area. These areas were not a
selected habitat type for any of the study species. However, most planted pine areas will
potentially provide suitable habitat for species if the stated District objectives are successful.
Red cockaded woodpeckers will benefit on planted pine areas, for example, if management is
successful in reestablishing an old growth pine community having the mature trees needed by









50

this species (Figure 32). White tailed deer can also use areas of planted pine. As these areas
mature and District management is successful in reestablishing more mature stands of varying
aged trees with diverse understory vegetation, deer populations may benefit. Where pines have
been planted using the railroad track spacing, development and growth of the understory will
enhance deer browsing.
Most cattle leases in the GSRCT are no longer active (the largest was discontinued during
this study). Some, however are still grandfathered leases which may be used at some future
time. Cattle can influence plant growth through browsing and may be a conflict to some wildlife
which depend on the same browse. The species most in conflict is the white tailed deer. Figure
33 represents the deer with the cattle lease overlay.









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DISCUSSION:
Managing the Terrestrial and Wetland Resources
of the Green Swamp Riverine Corridor Tract

The ecological communities of the GSRCT are self-organizing systems driven by natural
forces of sunlight, wind and rains and reorganized through human actions and of pulses of flood,
drought and fire. Good landscape management does not interrupt natural cycles or alter driving
forces. It fits development and economic uses into the landscape instead of upon it. Effective
landscape management balances a symbiotic relationship between ecological communities and
human uses for a long-term sustainable yield rather than short-term gain. The objective of the
Districts land management scheme is to restore and protect the natural state of lands (to the
extent practicable), in an environmentally acceptable manner. Our review of the Prescribed
Burning and Restoration Programs for the GSRCT suggests that the stated objectives and
techniques employed to achieve those objectives are not in conflict with good landscape
management. However, other uses impose management requirements, and thus act to overlay
existing management with a second layer of constraints and actions that ultimately affect overall
ecological function. For instance, stated District land management includes restoration of
degraded ecological communities through site preparation and planting of desirable tree species
and prescribed buying, yet the management of lands for wildlife hunting, or cattle grazing can
easily be in conflict with the stated objective. Additionally, secondary activities and
management that result from the primary objective of ecological restoration can have important
ecological consequences. For instance, road and fire line construction can create gaps in
otherwise continuous canopies. Or the construction of borrow pits can either enhance ecological
function and habitat values or detract from them.
Our discussion of management alternatives is not limited to the stated objectives and
techniques employed by the District, but covers other potential uses and resulting management.


Management Suggestions


Managing Groundwater Hydrology The importance of depth and duration of flooding to wetland
structure and function and ultimately to ecological well-being cannot be overstated. While
nutrient availability has obvious implications regarding wetland community composition,












hydrologic function remains the chief criteria upon which wetland determination is based.
Without water in sufficient quantity and for a sufficient period of time, a wetland is not a
wetland.
Depth and duration of flooding in wetlands is a dynamic balance of inflows and outflows
that are both externally controlled (variability in rainfall) and internally modified
(transpiration and recharge). Detailed studies of the hydrology of isolated cypress domes
(Heimberg 1984) showed two very significant results related to the dynamic behavior of
wetland hydrology: first, groundwater flows out of wetlands increase as the difference in
elevation between surface waters within the wetland and the elevation of groundwaters in
surrounding lands increases, and second, small wetlands are affected more by this phenomena
than larger wetlands. In other words, with lowered water table elevations in surrounding lands,
recharge is increased and the impacts of increased recharge more strongly influence surface
water hydrology in small versus large wetlands.
Both floral and faunal species composition in wetlands is strongly influenced by the
depth and duration of flooding. At the extremes, water depth determines the difference between
herbaceous and woody wetlands, yet subtle differences in water depth and duration can shift
vegetative composition from obligate hydrophytes to transitional species. When vegetative
species composition shifts, faunal food sources are influenced and when surface water levels are
altered habitat values change. Drier wetlands favor more terrestrial species at the expense of
obligate wetland species, because food sources shift and drier habitats favor different species
with different life history requirements.
The yearly cycle of wet and dry seasons and the re-occurring natural drought cycle act
together to add to the dynamic nature of wetland hydrology and consequently to the dynamics of
community structure. Under normal conditions the shifting rainfall patterns alter community
structure (principally the shorter lived herbaceous species) favoring more terrestrial species
during dry periods and more obligate wetland species during wetter times. In extremely dry
periods, many wetlands may burn naturally, the result of dry organic soils and accumulations of
litter that may have occurred during several years of dryer than normal conditions favoring
weedy understory species. Extremely hot fires may reverse successional trends and "setback"
forested wetlands to early stages of herbaceous or shrub dominated communities and may burn
organic soils lowering ground surface elevations.












The natural cycles of wet and dry seasons can be exacerbated when groundwater
elevations are lowered through drainage or lowered potentiometric surface in deep aquifers with
leaky confining layers. Dry periods last longer and depths of inundation are shallower. The
evidence for a strong relationship between drainage that lowers groundwater levels and serious
erosion of wetland ecological function is prevalent in literature. Burns (1978) found
significant decreases in productivity and biomass as well as increased incidence of hot killing
fires in wetlands of southwest Florida. In documenting the natural resources of the
Econlockhatchee River Basin, Brown et al. (1990) found that the most prevalent cause of
decreased environmental quality and loss of wetland habitat was drainage that lowered
groundwater tables. Bays and Winchester (1986) after reviewing factors that contribute to
changes in ecological functions of wetlands concluded that groundwater withdrawals were one of
the more significant causes of change, although somewhat limited in spatial extent.
In all, declines in surficial water tables result in loss of wetland values, like wildlife
habitat and food chain support, as well as causing shifts in plant community structure away
from predominately wetland species toward upland species. The general decline in Florida' s
groundwater levels brought on by increased urban demand for ground water resources,
manipulation of surficial water tables for agricultural and forestry purposes, and lower than
normal rainfall over the past decade have worked in consort to reduce the acreage and quality of
wetland ecosystems through out the State. The wetlands of the GSRCT have not been immune to
these trends. While direct withdrawals for public water supplies have not occurred within the
GSRCT, drought and generalized water table declines have resulted in lower than normal
surficial groundwater elevations. Reversing these trends should be of preeminent concern.
Where ever possible drainage works that increase runoff whether from previous ownership or
present management should be curtailed. Any plans for groundwater withdrawals for public
water supply purposes should be closely scrutinized in light of the potential impacts on the
mosaic of wetland and upland ecosystems of the GSRCT.


Managing Fire The ecological communities of the tract for the most part are fire
climax systems. The current fire management strategy has at least one of several objectives
depending on the site: (1) site preparation, (2)minimize build up of understory vegetation and
litter, and (3) ecosystem management. Ecosystem management involves maintaining and
enhancing natural plant communities, habitat potential, community diversity, and nutrient












cycling as well as burning for the control of diseases. The frequency and timing of burning and
age of stand when first burned affect both the build up of understory vegetation and litter and
ecosystem functions.
There are both positive and negative consequences of control burning. The obvious
advantage is that it prevents destructive wildfires and maintains most pine systems in a fire
climax state. Many wildlife species benefit from burning, yet there are 14 wildlife species
including 2 listed species that are likely to occur within the tract that rely on the mid-story
canopy for nesting, feeding, or breeding (Schaefer 1990, in Brown et al 1990). Frequent
burning that effectively eliminates the mid-story canopy can eliminate these species. Without
control burns, however, sites with dense midstory canopy are susceptible to destructive
wildfires. Yet, management that fosters areas with dense midstory canopy may be an important
objective. The most logical flatwoods sites that may be allowed to develop thick understories are
those that because of their locations have greatest natural protection from wildfires such as
sites that are protected by surrounding wetland communities. Obviously, because of their
relatively inaccessible locations management of these areas may already include the no-burn
option. Because of their adjacency to wetland communities, development and maintenance of mid-
canopy and shrub vegetation in these upland systems will benefit numerous wetland wildlife
species that spend portions of their life cycle in adjacent uplands (see Schaefer 1990).
Control of the midstory canopy may be essential for some species. There is some
evidence (U.S. Fish and Wildlife Service, 1985) that most active colonies of Red-Cockaded
Woodpeckers (RCW) are found in open, park-like stands of pine with sparse midstories. While
they will tolerate a wide range of stocking in the pine overstory, it is generally agreed that the
birds will not nest in tracts with dense hardwood stocking in the midstory. One plausible
explanation is that the more moist sites having greater midstory hardwood biomass are better
habitat for populations of pileated and red-bellied woodpeckers than the more pure stands on
drier sites. Both the pileated and red-bellied woodpeckers are known for usurping RCW nesting
cavities. The drier areas of planted pine and flatwood sites in the northeastern quadrant of the
tract may offer potential RCW habitat if managed for old growth timber, proper stocking rate
(13.9 to 20.7 m2/ ha [60-90 ft2/acre] basal area with 60 trees/ hectare [24 trees/ acre]
greater than or equal to 25 centimeters [10 inches] DBH) and control burned to minimize mid-
story canopy. A map of potential RCW habitat is given in Figure 32 showing those areas where












selective harvesting and management for old growth pine communities might develop habitat
suitable for the their introduction to the tract.
Frequent burning of marshes, wet prairies and open range land is essential for
maintenance of habitat for the Florida Sandhill Crane. Figure 34 shows the area of largest
concentration of wet prairies and marshes with an over-lay of the Crane habitat suitability. A
burn schedule of once every 2-3 years may benefit Crane habitat requirements in maintaining
wet prairies and open range land. Burning of marshes and wet prairies is probably best
accomplished in spring or early summer when organic soils are wet (to minimize loss of soils
and plant rhizomes).


Managing Forest Resources While the District does not practice silviculture, in the
intensive management sense, and in fact silviculture as practiced, is aimed at restoring
ecological communities, the following discussion is intended to help develop a rationale for the
continuation of practices that yield sustainable ecological communities first, and possibly
timber yields of secondary importance. In addition, it is urged that the District embark on a
program of documented research on forest resource management that could benefit the timber
and paper industries and ultimately the citizens of Florida by demonstrating alternative
management techniques that foster multiple forest resource values, including ecological values.
Since objectives of lands management are resource protection and preservation, the research we
suggest be done should not compromise these goals, but in the long run enhance them.
Often silvicultural operations are managed for the timber resources, with less attention
paid to other considerations, like wildlife. Cutting practices that cut all timber including
wetland timber, site preparation practices that ditch and drain wetter sites, and clear-cutting,
in general, may favor opportunistic and successional species in favor of other indigenous
wildlife. There is ample evidence that habitat fragmentation and induced edge caused by clear
cutting may erode habitat quality for many wildlife species, especially bird populations. There
is a serious need throughout Florida for sustained yield forests of older growth timber that give
equal consideration to wildlife values and timber value. Old growth forests offer much greater
potential wildlife habitat for a diverse array of species than do young even aged stands of
vigorous growing pine. The timber and paper industries could benefit from research that
demonstrates yield potential from alternative forestry management practices that include
wildlife values.









57

The GSRCT with its diverse mosaic of wetlands and uplands may be the perfect landscape
to research pine forestry management schemes that seek to lengthen overall rotation times
through selective harvesting on a site cycle of greater than 100 years. Sustainable, economic
yields may be achievable through management of selected areas for old growth along with areas
on a shorter rotation. Selective harvesting and rotating clear-cuts of both upland and wetland
communities in small strips leaving uncut forested canopies in alternating rows could be
researched. Field research aimed at a better understanding of cutting cycles, size and shape of
cuts and leave strips, and their impact on timber, wildlife, and economic yields, is needed.
Many of the current management practices are in consort with the objective of maintaining and
enhancing ecological communities that will support viable populations of wildlife. However,
without a concerted effort to organize field methods and collect data in a consistent manner,
much of what might be learned from management will not be transferable to industry and
government.
Wetland communities, especially isolated cypress domes are under considerable
silvicultural pressure throughout central and northern Florida. Most of the forested wetlands
of the Green swamp were logged by the early 1950s, and regrowth from stump spouts and
reseeding has occurred. Todays swamps are composed of 30-40 year old trees having little
timber value, but having value as mulch. As the trees continue to mature, it may be possible to
once again harvest cypress for its timber value. However, clear cutting of swamps using heavy
machinery should be avoided since it often results in impacts to soil substrate leaving deep ruts
that may channelize flows and alter hydroperiods. Instead, harvesting techniques should be
employed to minimize the use of heavy machinery within wetland ecosystems. Research is
needed to better understand cypress (and other wetland trees) regeneration, to develop
sustainable yields that does not compromise wetland integrity.


Managing Roadways and Burn Control Lines Habitat fragmentation that results from
roadway construction can be a critical factor related to loss of habitat quality. Induced edge in
forested communities results in increased edge habitat. Species that require interior forest
habitat are replaced by those that favor edge. Increased predation of interior species and loss of
nesting habitat are the main causes of declines. The literature suggests that edge effects can
extend 90 meters (300 feet) into the interior of a forested community. In other words, an
induced edge resulting from a roadway cut can lower habitat quality for many forested species












over an area of 180 meters (600 feet) plus the roadway width. When multiplied by the total
length of road, the loss of habitat can be significant.
In studies of the need for wetland buffers Schaefer (in Brown et al 1990) calculated that
continuous uncut forested buffers of greater than 335 meters (1,100 feet) surrounding
wetland communities were necessary to maintain viable wildlife habitat in wetlands and
adjacent areas. The rationale suggested that a minimum of 335 meters (1,100 feet) was
necessary so that species that were wetland dependent were protected from edge effects and loss
of critical habitat. The study was based on analysis of habitat requirements of 214 non-fish,
vertebrate, native species. In planning future road construction and the maintenance of existing
roads within the GSRCT, we feel that significant wetland areas (>30 hectares or 75 acres)
should be protected by wildlife conservation buffers of 335 meters (1,100 feet) or greater.
A serious impact of roadways and to a lesser extent, fire control lines is the alteration of
surface drainage conditions. When constructed perpendicular to surface drainage, wet season
sheet flow can be interrupted, impounded or diverted. When constructed parallel to drainage,
sheet flow can be channelized and diverted. The consequences of diverted sheet flow may not
seem serious, but in areas of extremely flat terrain where ephemeral ponds and shallow
marshes receive surface waters from surrounding uplands the loss of their watershed can
seriously affect water budgets. A simulation model used to evaluate development impacts on the
hydrology of isolated wetlands (Brown, 1988) suggested that the loss of surface run-in from
the surrounding watershed could decrease hydroperiod as much as 50 percent. Fire control
lines should not interrupt surface drainage patterns and channelize flows away from or into
wetland systems. Roadways should have sufficient culverting to insure that surface drainage
patterns are not interrupted.


Managing Borrow Pits and Excavations Excavations for fill material for roadways and
culverts are frequently dug from an uplands area in close proximity to the location where the
fill is required. There are several excavation pits in the GSRCT. Their presence and potential
ecological functions and those of future excavations can be enhanced if the void that is created is
considered as important as the material that is removed. Often the only concern when making an
excavation is the removal of material as efficiently as possible, thus holes are dug to
accommodate machinery and to minimize the foot print of the excavation. Minimization of an
excavations foot print is advisable only if it is an ecological liability. If designed right and












replanted in vegetation it may become an important contribution to overall landscape
heterogeneity. By increasing the foot print (thus decreasing the depth) and varying the depths
of an excavation, a more ecologically functional aquatic and wetland system can be created.
Figure 35 shows a plan view and section elevation of a possible excavation. The edge of
the wetland is varied to maximize shoreline length and thus wading bird usage since most are
known to fish singularly. Depths of the pond vary: those appropriate for a shallow marsh (0-
45 centimeters deep), those appropriate for a deep marsh (45 -90 centimeters deep), and
depths that will remain open water (>90 centimeters). An island, surrounded by permanent
water could be incorporated as a nesting site for wildlife species that seek sites protected from
terrestrial predators. The margins of the island could also be sloped and planted in emergent
vegetation. Since the groundwater elevation varies from wet to dry season, some knowledge of
its elevation relative to the ground surface is necessary to accurately contour the excavation pit.
Table 7 lists herbaceous plant species that are appropriate for planting in the shallow and deep
marsh areas. Since the GSRCT is not deficient in forested wetland systems, we have not included
tree species. However, in other areas where forested wetlands might be desirable because of
their relative scarcity, tree species and herbaceous species could be planted simultaneously.
The location of excavation pits might be driven by ecological function, as well. Water is
an essential aspect of habitat quality for many wildlife species. Excavations for road fill
material offer the potential to increase wildlife habitat suitability by providing, in otherwise
dry areas, a surface water body for wildlife use. Future excavations might enhance landscape
heterogeneity and wildlife suitability if located in areas where no surface water presently
exists, or where it does not exist during the dry season.


Managing Cattle Grazing Although the largest cattle lease in the GSRCT has been discontinued,
there are several smaller leases that remain active. While it is difficult to determine specific
impacts of cattle grazing on ecosystems and wildlife of the GSRCT, it can be logically assumed
that any activity that alters the ground vegetation on a continuous basis will have an impact.
Previous review of the literature (Brown et.al 1990) revealed a paucity of studies on the
impacts of native range cattle management on wildlife and ecosystem function in Florida. Many
studies, reported in that review were from western range lands. Yet these studies and anecdotal
evidence from field observations in central Florida suggest that cattle grazing on native range
can significantly alter vegetation and wildlife habitat quality. The severity of impact depends on












several variables: the density of cattle, type of ecosystem, grazing schedule, and other
management actions like burning.
Some ecological communities are more sensitive to cattle grazing than others, just as
some species of plants are more desirable as forage. Hardest hit are marshes and wet prairies,
and if density of cattle is high enough, they can be completely defoliated or selectively grazed to
the extent that species composition is shifted. Understory vegetation in forested communities
can be reduced, seedlings trampled or grazed, and species selectively eliminated in grazed areas.
Again the severity of these impacts is related to density, ecosystem type, and grazing schedule.
Streamside areas may be particularly sensitive to uncontrolled grazing since cattle often return
to streams for water and vegetation of the aquatic/ terrestrial interface. Water quality impacts
associated with cattle use of streams and streamside areas is well documented. Loss of
streamside vegetation through grazing and trampling can increase turbidity and siltation, and
the increased nutrient loads from cattle feces and urine can negatively impact aquatic production
and species composition.
In all, recommendations of appropriate stocking rates and grazing schedule are difficult
to make, since so much depends on the combination of ecological communities that may be within
a given cattle lease and site specific conditions of each of those communities. Recommended
stocking rates for native rangeland by the SCS are probably based more on the ability of
ecological communities to provide forage than on negative impacts of selective foraging and
trampling on species composition of communities, or water quality impacts on stream
ecosystems. In the absence of quantitative data that would support other recommendations,
minimum stocking rates should be observed in all areas where restoration and protection of the
natural state and condition of ecological communities is the objective. Where cattle grazing is
conducted, quantitative studies of community structure and wildlife populations would yield
much needed information for the management of this important use of District lands.


Managing Feral Hog Populations Like cattle grazing, the activities of feral hogs can have
serious impacts on ecosystem structure. However, unlike cattle, which graze over a wide range
of communities, selectively foraging, hogs often concentrate their rooting in relatively small
areas. The result is concentrations of activity in areas of extremely impacted ground vegetation.
Anecdotal observations of the activities of feral hogs suggests that they often root in the
transitional areas between wetlands and uplands, probably because of the ease with which soil












can be turned and the relative abundance of desirable food. At high population densities the
damage to these areas could reverse stated objectives of restoration and protection of the natural
state and condition of ecological communities. At low densities, the added heterogeneity that
results from their rooting activities may offset the negative impacts.
At the present time the Florida Game and Freshwater Fish Commission manages feral
hogs through size and bag limits to maintain a population for hunting purposes. Setting limits
on population size depends on determining an acceptable level of community disturbance by
their rooting activities. Some level of disturbance in some areas is probably acceptable,
however in the absence of quantitative data on the existing population size and the extent of their
disturbance, it is difficult to suggest appropriate population levels. However, we do strongly
recommend that populations be controlled and that hunting be encouraged to maintain
populations as low as possible. Their presence on the GSRCT offers the potential for long term
study of their impact on ecosystem structure and function and if studied from an ecosystem
(landscape) perspective, would provide important data upon which management options, for
this tract and others, could be based.


Managing Recreational Uses The primary recreational activity (based on numbers of users)
within the GSRCT is hunting. Other uses include fishing and frogging and passive activities like
hiking. Potential uses include all terrain bicycling, and the use of All Terrain Vehicles (ATVs).
During the hunting seasons these other activities are, obviously, unlikely to occur. The Florida
trail bisects the tract and offers an attractive day hike, especially during the spring. In all the
existing and potential recreational uses of the GSRCT are important, quite varied, and often in
conflict.
The impacts of recreation, like other uses, is density and activity dependent. The
intensity of the activity sets its density, or carrying capacity. Recommendations for managing
recreational activities are as follows:
The use of ATVs within the tract should be strictly limited since evidence from other
areas suggests that ATVs cause loss of habitat quality from excessive noise
(Brandt and Brown, 1988) and degradation of community structure from their
off road use.
All terrain bicycles if confined to designated trails are compatible with resource
management objectives for the tract. This new and growing recreational activity












is relatively passive in its impacts on the environment, and would take full
advantage of the size and extensive network of roads within the tract. There is an
obvious conflict with hunting during portions of the year. At the present time
there is no reason to limit to the number of bicycle users within the tract, except
during hunting seasons.
Hiking along the Florida Trail is compatible with resource management objectives for
the tract. The Florida Trail is maintained by volunteers and seems to be in good
condition, although there were several areas along its length where we lost the
marked trail for a time, but eventually retraced steps and found it again. There
are obvious conflicts with hunting during portions of the year. There are no
reasons to limit hiking use of the tract, except during hunting seasons.
There are several locations along the Withlacoochee River that offer good fishing and
frogging. An obvious conflict with hunting limits fishing to off season times.
Limits on fishing recreationists may be more the result of their need for vehicle
access to get to remote areas than their consumptive activities. Generally
frogging is a night time activity and may require changes in the operation of the
tract if allowed to take place.
Overnight camping within the tract might be considered. There is an increasing need
for camping areas that offer recreationists a wilderness camping experience.
Because of the extensive hunting activity during portions of the year, camping
should be limited to off season times. At the present time there is no need to limit
the number of campers, but if the activity were to gain in popularity, limits may
need to be imposed, more from a human perspective than from a resource
perspective.


Managing Utility Corridors Utility corridors, especially for electric transmission lines, cut
through the landscape and fragment once continuous forested canopies. Control of the location of
any additional utility corridors should be implemented to locate their right-of-way in such a
manner as to minimize fragmentation. The best location for utility corridors is along existing
corridors, or roadways.











Managing Exotic Species The introduction of exotic species to the sate of Florida has resulted
in relatively serious ecological consequences. While many introduced terrestrial species are
tropical in origin and therefore do not represent a serious threat to the GSRCT there a several
that deserve attention. In addition, several aquatic plants should be mentioned. These include
the floating aquatic, water-hyacinth (EIchhornia crassipes); the shrub, Brazilian-pepper
(Schinus terebinthifolius); the submerged aquatics, Waterweed (Egeria densa), Elodeas (Elodea
spp.), and Hydrilla (Hydrilla verticillata); the sprawling herbs, East Indian Hygrophila
(Hygrophila polysperma) [known to exist in Pasco county] and Alligator Weed (Alternanthera
philoxeroides); the emergent herb, Wild taro (Colocasia esculenta); and the trees, Melaleuca
(Melaleuca quinquenervia), Mimosa Tree (Albizia julibrissin), Camphor Tree (Cinnamomum
camphora), and China-berry tree (Melia azedarach).
The level of infestation of exotics in the GSRCT is unknown. It is likely that aquatic
species common throughout central Florida (water-hyacinth, hydrilla, and alligator weed) can
be found in the tract. Species that are dispersed by birds (Brazilian-pepper, mimosa, camphor
and China-berry) may not present an immediate problem since distances to seed sources are
still relatively large (although significant infestations of Brazilian-pepper and camphor are
known to exist in the unreclaimed lands of the Tenoroc Preserve in the northern Saddle Creek
Basin). The wind dispersed Melaleuca tree is known to exist at the same latitude in central
Florida and on both coasts, although recent freezes have diminished its relative importance in
these locations. Most probably, both Melaleuca and Brazilian-pepper will not represent a
serious threat to the ecosystems of the GSRCT since annual freezes will reduce their potential to
become nuisance species. The other woody exotics (Camphor, China-berry, and Mimosa), on
the other hand, are somewhat more freeze tolerant and may become established within the Tract.
Since the presence of exotic species can be construed to oppose the stated objective of
restoring and maintaining native plant communities, prevention of their establishment within
the Tract may be advisable. Control of terrestrial exotics varies from programs of herbicide
application (where infestations are large) to selective removal of the target species (where its
nature of growth warrants and/or where the infestation is small). Aquatic weed control usually
involves the application of a systemic poison or herbicide. While effective in reducing the
infestation, the practice often results in increased accumulations of decomposing organic matter
that negatively impact dissolved oxygen levels.












In general, exotic vegetation control may best be accomplished through effective
landscape management that increases fitness and therefore competitive advantage of native
species. Since many infestations of exotics are the result of changed environmental conditions
that favor exotics over natives, maintaining and enhancing competitive advantage of native
species can be accomplished by maintaining and restoring abiotic conditions that favor them.
Without changing the conditions that favor exotics over natives the use of poisons for their
control may result in long term commitments for control instead of eliminating the conditions
that give exotics competitive advantage. The possible exception is aquatic plants that have
flourished in the relatively nutrient rich surface waters of Florida.
From a purely ecological perspective, however, the question must be asked...does the
elimination of exotics serve anything other than an aesthetic purpose? The increased
productivity that results from exotic infestations on disrupted lands or the filling of an unfilled
niche often result in increased food chain support that can be argued to result in greater overall
ecological value. Only if the goal is to maintain native communities composed of species that are
endemic to the region can their elimination be justified. Thus, since the stated objective of
management policy is to restore and maintain native ecological communities, the elimination and
prevention of establishment of exotics within the Tract is warranted.













SUMMARY


One objective of this research project was to develop a method for evaluating the wildlife
habitat potential for District owned lands using the GSRCT as the focal point. The method that
was developed relied on mapping habitat requirements of indicator species. Obviously, the
greatest limiting factor in developing the method was the paucity of data on habitat
requirements. Research is needed to develop a better data base from which to assess wildlife
habitat requirements.
Other measures of landscape scale diversity were used to evaluate landscape
heterogeneity. Combined, they showed those areas of the Tract that had highest heterogeneity.
There is much in the literature that suggests that heterogeneity can be equated with greater
ecological importance since a diverse landscape offers more opportunities for a greater number
of wildlife species.
A second objective, which was an outgrowth of the first, was to offer management
suggestions for the GSRCT. Specific management suggestions require detailed knowledge of both
the spatial and temporal organization of the ecological communities of the Tract. While we had
considerable information regarding the spatial organization, time and resources available
limited the amount of temporal data that we could collect. Much needed was the age and species
composition of forest stands. However, the size of the Tract precluded the collection of these
data. As a consequence, we have reviewed the current management regime and made general
suggestions concerning both the explicit techniques employed and those that are implicit because
of the various uses the Tract is subjected to. For the most part, current forest management
practices by the District are aimed at achieving and maintaining healthy ecological systems
throughout the Tract. The techniques employed: planting, burning and selective harvesting will
achieve their intended goal.
If there is anything in current management that might be improved it is the use of
District lands and implementation of the management regimes for research purposes. Much can
be learned from District lands about multiple use forests and sustainable yields that reflect both
economic and ecological values. This is not to say that the District is not learning from
continued management of its lands, nor that the proposed research would be consistent with the
statutory directives of Chapter 373, F.S....only, that with a program of intentional research to












answer broader questions of the interactions of humanity and nature, much that would benefit
the citizens of Florida could be learned. Unfortunately, State and National forests, which are
dedicated in large part to timber production have not as yet devoted much substantial effort to
conducting research into these larger scale issues. There are few agencies equipped with large,
diverse tracts of land where pressures are not great to achieve high economic yields, and
therefore have the luxury to evaluate management alternatives. Information learned
couldbenefit industry, other governmental agencies, and the citizens of Florida through
increased economic and ecologic productivity in a balanced system of humanity and nature.








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83
471







LAKE





...... ...P...OLK

.o .-...,:. .: . < lk <:......




















0 1 2 3 4 5
I I I I IN
MILES











Figure 1. The Green Swamp Riverine Corridor Tract (GSRCT) is located in central
Florida within an area known as "The Green Swamp". The Green Swamp
Riverine Corridor Tract contains portions of Lake, Polk and Sum ter
counties.


-Ii.- .. .1.11, .232-I~~ LL~~=- I~ WW )IB VI*BY90







Cattle Lease.map

. . . .: ..
i.. . .iiiiii.. .ii
7i f

.::::' :::
: ::iUii ii :. : : .: i :
::::::::::: ::::: :: : ::::: iiii
":I i :::: i i C; i : : : :::::: i i iii
: ::" ; : )i . .. :i: "
i iii !ii.iiIi2


i i :i i i : : : : :

:::I::i -; iiii
::::::-11.













----I=3000 Metres 1:283465



Figure 2. Map showing the cattle leases in the Green Swamp Riverine Corridor
Tract.









Rivers.map


Figure 3. Map of rivers as shown on USGS Quad maps. Hunting is allowed north of the
Withlacoochee River (Gray line transversing in an east west direction).








Trail.map 86

Sil i ii i !ii!!

















}*--**= 3000 Mtres 12834
::::::::::

:::::::::::'''::::~~~:::~;:: ::;;;
i.. .......
...........
.... ...
,.. ... . . .










..........

. . ..
:i -- -- -I ~ i. . . . .0 0. M.:2 5
.............. : ::: ;:::;;:;:::;;:
. ..... . :::;:::::::: i :::::: -::: ::::::::::
. . . ...: ::: ::~~:: ~ :: ::

:i:::::~i~i~i::i......... ....:I :
: :I ~ : : .. .... . . . . . . ....: : : ;:-:










30M Metres 1:283465::: :r..:r.. ~..::


Figure 4. Map showing the location of the Florida Trail.











CNTRL1.MAP


--- = 3000 Metres 1:283465


Figure 5. Map showing the location of prescribed burn fire control lines.









88
Burn.map
r


. . . . ..



.. . . ..i r i

i, I : ::~.. ii:: ij i: i rr i ...... ...; ii
i : iii :.. ..... ....... i i ~l


i = 3000 Metres 1:283465


Figure 6. Map showing the location of recent wildfires.


~~. .. ... . . .


FI:: : : : :
I: j i :i : i i i i j : i

i i i i i ii.











SAMPLING EFFICIENCY
ltart aof seanrpln am Sum


_- 21So 113M
'npj FraflM Sim (=cmw)


Figure 7. Graph of sampling efficiency showing the effect of increasing sampling frame
size on the number of polygons per unit area.












S-- Isr reposition


- Initial cell location


Figure 8. Diagram illustrating the method of cell relocation to account for positional
bias. Suitability was determined for each of the cells by moving the cell 1/3
of cell size up and to the left, and then again 1/3 cell size up and to the left.


f


--










Planted Pine & Pine Ratwoods.map


Figure 9. Map showing the location of pine flatwoods and planted pine plantations
(dark areas).


~









92
Hardwood Hammock.map



























I--ii=i 3000 Metres 1i283465



















Figure 10. Map showing the locations upland hardwood hammocks (dark areas).
I = 3000 Metres 1:283465



Figure 10. Map showing the locations upland hardwood hammocks (dark areas).










93
Marsh & Wet Prairie.map














.............::: ...: ..:i:::::..........










............
:...... =- 3000 Metres 1:2&W5 = =
Figure 11. Map showing: the locations of marshes and wet prairies (dark areas).::
*::: *:::: <::



:::::::::: : : ::::::::::::::::: :::



































Figure 11. Map showing the locations of marshes and wet prairies (dark areas).









Cypress & Mixed Swamp.map


Figure 12. Map showing the locations of non-riverine cypress and mixed hardwood
swamps (dark areas).









Riverine Swamp.map


Figure 13. Map showing the locations of riverine cypress and riverine hardwood
swamps (dark areas).










Simpsons


Figure 14. Map showing the locations of the 30 highest "scoring" cells for
Simpsons diversity. Cell shading indicates relative ranking of score, where
the darker the shading the higher the score.










Shannon 9


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-l 300 Metr sl: 83465 1
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:': :...... ~.. :. '. :':. .:-. :'. :'. :'. :' .: : : ::..: '- ':-::. .i
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:::::: : :::::::::::::: ::::::::'-
:' :: ::::: :::::::::::::::''";::r::::: :::: ''5













,N o....o X -..%.
"darker the shading'the higher thescore.
:::::::::::: :::::::::::::::::::: ::
;.:.:.,:c :-::.:.:,:' rZ"" '
'',..--.,.-,I ::: = 3000 Metre 1:28346'5' ::: -:' ' ::

Figure 15. Map shoin the loaton o. the 30. hihs soigclsfrSann
Weiner::: divrsty Cell shain inicte reatv ranin of: score, wher the- ~I :
dake the..... shading .. the highe the score









98
Dominance












































I--= 3000 Metres 1:283465


Figure 16. Map showing the locations of the 30 highest "scoring" cells for
Dominance. Since dominance is inverse to diversity, the 30 cells shown here
------.I 3000 Metres 1:283465


Figure 16. Map showing the locations of the 30 highest "scoring" cells for
Dominance. Since dominance is inverse to diversity, the 30 cells shown here
have the lowest dominance values, where the darker the shading the lower the
dominance value.




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