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Group Title: Bulleltin Florida Cooperative Extension Service
Title: Ecology and management of cypress swamps
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Title: Ecology and management of cypress swamps a review
Series Title: Bulleltin Florida Cooperative Extension Service
Physical Description: 19 p. : col. ill. ; 28 cm.
Language: English
Creator: Brandt, Karla, H
Ewel, Katherine, Carter
University of Florida -- Institute of Food and Agricultural Sciences
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1989
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Subject: Cypress swamp ecology   ( lcsh )
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    Ecological relationships
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    Forestry practices and lumber production
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    Water management & Management of cypress swamps
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    Literature Cited
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Full Text

May 1989
May 1989


Ecology and Management

of Cypress Swamps:

A Review


Karla Brandt and Katherine C. Ewel



Florida Cooperative Extension Service
Institute of Food and Agri:ultural Sciences
University of Florida
John T. Woeste, Dean


101
2Y26b


Bulletin 252


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Table of Contents


Introduction ........ ......... . .. .....


. . . . . . . . . 1


Ecological Relationships ..........

Distribution . . . . . . . . .
Productivity . . . . . . . . .
Importance of Water .. .........
Fire . . . . . . . . . . .
Seed Production, Dispersal, and Germination
Seedling Survival ... ..........
Regeneration by Coppice ..........
Use of Cypress Swamps by Wildlife .....
Impact of Insects and Diseases .......


Forestry Practices and Lumber Production . . . .

Mensuration ......... ... ... ......
Timber Production and Standing Stocks . . . . ...
Logging Practices .......... ........
Cypress Regrowth Following Logging ...........
Silvicultural Systems ...... ...... ...
Planting ............ .... .. .........

Water Management .. ..................

Management of Cypress Swamps ............

Silviculture . . . . . . . . . . . . .
Burning ..........................
Multiple-Use Management .. . .............

Literature Cited. ........ ...........


. . . . . . . . . . 9

. . . . . . .. . . 9
. ... . . . 10
.. . . . . . . 1 1
. . .. . . . 12
. . . . . . . . . 12
. . ... . . . 13


. . . .. .. . . . 17


Abstract


1 0

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1 LIBI









Ecology and Management of Cypress Swamps: A Review


Karla Brandt and Katherine C. Ewel*


Abstract

Cypress trees (Taxodium distichum) are found in
wetlands throughout the southeastern Coastal Plain
and north along the Mississippi River floodplain into
southern Illinois. Three different forms are recognized:
pondcypress, baldcypress, and dwarf cypress. Pondcy-
press is more tolerant of fire and low nutrient availability
than baldcypress. Dwarf cypress is pondcypress that
grows where nutrients are severely limited. Cypress
trees in Florida grow under a wide range of conditions:
nutrient-poor savannas, moderately productive isolated
ponds, and diverse, highly productive river swamps.
Cypress swamps appear to be even-aged stands,
although it is not clear if this is due to natural conditions
or to previous management practices. Regeneration
does not occur every year because of variations in seed
production and water level. Seeds are not produced
every year by every tree, and they will not germinate
under standing water; seedlings cannot tolerate long
inundation. Regeneration also seems to be best in
nearly full sunlight. It is therefore possible that most
regeneration occurs only once in several years.
Most cypress swamps in the Southeast were
harvested during the late 1800s and early 1900s. The
wood was used for a variety of purposes, some of
which, such as the use of hollowed logs for water
mains, exploited the rot-resistant properties of the
heartwood in centuries-old trees. Logging practices
included girdling large trees several months before
harvest to remove enough water from the wood to
float the logs out of deep swamps after cutting. Later,
levees and railroads were built to provide access to
remote swamps.
Modern forestry practices in cypress swamps are
quite different. Rubber-tired feller-bunchers and
skidders are now widely used for harvesting. Although
there is some evidence that thinning can increase the
growth rates of remaining trees, clearcutting is widely
used, in part because all sizes of trees can be made
into chips for mulch. Soil compaction by large machin-
ery can hinder regeneration, although Florida's sandy
soils may not be so susceptible. The ability of cypress
stump sprouts to produce seed one or two years after
logging may compensate for loss of advance regenera-
tion.
Estimating biomass of cypress swamps is not easy,
because irregular tree shapes in different kinds of


swamps make volume tables difficult to interpret. Nor
can age of a cypress tree be determined precisely
because of the propensity for producing false growth
rings.
Cypress swamps offer more than fiber production.
They provide food, cover, and nesting sites for a variety
of wildlife species. The importance of swamps in
reducing flooding is well known. Intact cypress swamps
may keep regional water supplies high because of their
slow evapotranspiration rates. Finally, cypress swamps
in many parts of Florida are providing some degree of
advanced wastewater treatment. These uses must also
be considered in formulating management plans for
cypress swamps.

Introduction

The Atlantic and Gulf coastal plain states in the
southeastern United States contain at least half the
wetlands in the lower 48 states, according to prelimi-
nary results from the National Wetlands Inventory
(summarized by Mitsch and Gosselink, 1986). More
than 40% of these wetlands (8 million hectares, or 20
million acres) are in Florida and Louisiana. This
concentration of wetlands has provided the region with
a wealth of opportunities for both passive and active
uses. Population pressure and increasing demands on
a shrinking resource base have brought some of these
uses into conflict, requiring a more careful assessment
of the demands that each use places upon the re-
source.
Forested wetlands (swamps) occupy large areas in
Florida and Louisiana, especially. Swamps cover 28%
of commercial forest land in Florida (Dippon, 1983).
Most of these swamps are dominated by baldcypress
(Taxodium distichum) and/or pondcypress (considered
by some to be closely related [T distichum var.
nutans], and by others to be a distinct species [T
ascendens]). Cypress swamps line rivers and lakes,
and they occupy long, meandering channels and
isolated ponds. Swamps have been important in
shaping the economic and cultural development of
Florida and Louisiana, and they remain important as
the ecological relationships within them and the
landscapes they occupy are explored.
Historically, commercial interest in swamps was
limited to timber harvest. Little attention was paid to
long-term management techniques. The resistance of


* Graduate Student and Professor, respectively, Department of Forestry, IFAS, University of Florida, Gainesville, FL 32611

1


UNIVERSITY OF FLORIDA LIBRARIES








cypress heartwood lumber to decay, even when
exposed to moisture (Roth, 1898; Mattoon, 1915;
Betts, 1960), made old, large trees quite valuable. Most
of the larger cypress trees were harvested during the
cypress logging boom that peaked in the 1920s. The
amount of standing timber reached its lowest point in
1933, but has steadily increased during the last 50
years.
Recently, recognition has been given to the impor-
tance of cypress swamps for other uses, such as
wastewater treatment and wildlife habitat. Do these
different uses of swamps conflict? Can rapid regenera-
tion of cypress in harvested swamps be ensured, while
allowing simultaneous use for other purposes? Is there
enough information available to make sound manage-
ment prescriptions? To help address these questions,
this paper reviews the literature pertaining to the
ecology and uses of cypress swamps. Although we
draw on information extracted from the entire geo-
graphic range of baldcypress and pondcypress, we
focus primarily on Florida, where both types are
common.


Ecological Relationships

Distribution

Baldcypress is found along the Coastal Plain from
southern Delaware into southern Florida and west to
southeastern Texas (Fig. 1). It occurs north along the
Mississippi Valley to southern Illinois. Pondcypress has
a more reduced range, and its northern limit is south-
eastern Virginia. Baldcypress usually grows in flowing
water, such as in river swamps and along stream banks
and spring runs, as well as along lake shores. Pondcy-
press is generally confined to ponds and slowly
moving water. Under extreme nutrient limitation, such
as on the marl soils common in the Everglades and on


Fig. 1. Distribution of baldcypress and pondcypress in
North America.


clay soils in the Florida Panhandle, growth is very slow,
and the stunted pondcypress trees characteristic of
these conditions are often called dwarf cypress or
hatrack cypress.
The differences between pondcypress and baldcy-
press may be distinct at some sites but cloudy at
others. We regard them as sibling species, which are
populations that differ in many characteristics but can
still interbreed. They overlap extensively, intergrading
along a continuum. Trees at opposite ends of this
continuum grow in different sites and at different rates
(Table 1). The two often grow together, and characteris-
tics of both types are occasionally found on the same
tree.


Table 1. Important differences in characteristics of pondcypress and baldcypress


Characteristics


Baldcypress


Pondcypress


Stand
Stem density Low High
Rate of average water flow Moderate Slow to stagnant
Nutrient availability High Low
Fire frequency Rare Occasional

Individual tree
Growth rate Fast Slow
Maximum diameter Large Small
Bark Thin, tight Thick, shaggy








Both trees grow in pure stands as well as with other
species. Baldcypress is most commonly associated
with both water tupelo (Nyssa aquatica), primarily in
river swamps, and swamp tupelo, also called black
gum (Nyssa sylvatica var. biflora). It also grows with
red maple (Acer rubrum), ashes (Fraxinus spp.),
sweetgum (Liquidambar styraciflua), oaks (Quercus
spp.), and southern pines (Pinus spp.). Pondcypress
usually occupies isolated ponds, which are particularly
common in Florida and Georgia, and it often occurs in
standing water on the edges of large swamps. Swamp
tupelo is the most common tree in the subcanopy of
cypress ponds, and several species of pines and a
variety of hardwoods occur on hummocks and along
the shallow edges.
In the Big Cypress National Preserve in southwest
Florida, the largest and fastest-growing cypress trees
grow in deep peat (up to 2 meters, or 6 feet), and
pondcypress trees are most common in shallower,
mineral soils (Duever et al., 1986). Cypress generally
grows best on moderately well-drained, moist, deep,
fine sandy loams, but hardwood species usually
outcompete cypress on well-drained soils. In addition,
well-drained soils may not provide enough moisture for
germination of cypress seeds; the best seedbeds for
cypress are sphagnum moss or soft, wet muck
(Mattoon, 1916). Consequently, cypress is usually
restricted to very wet mucks, clays, and fine sands
(Langdon, 1958).


Productivity

Very few measurements of productivity have been
made in cypress swamps. Gross primary productivity
(the rate of photosynthesis) and aboveground net
primary productivity (increase in biomass, such as
wood and new leaves) are directly related to both
water flow rates and nutrient fluxes (Table 2) (Brown,
1981). Productivity is highest in river swamps, which
receive periodic inflows of water and nutrients. It is
intermediate in stillwater swamps, such as ponds and
the long, slowly flowing swamps called strands; these
swamps are dominated by pondcypress. Productivity is
lowest in dwarf cypress savannas, where nutrient
storage and inflows are barely perceptible (Brinson et
al., 1981; Brown, 1981).
Although Florida cypress swamps may store substan-
tial amounts of nutrients in peat, acidity reduces
nutrient availability (Dierberg and Brezonik, 1984).
Cypress trees in these types of swamps respond to
increased nitrogen and phosphorus levels with in-
creased tree growth rates (Nessel et al., 1982; Lemlich
and Ewel, 1984). Growth rates in Florida cypress
domes and strands are equivalent to those in mature
north Florida slash pine plantations (Gholz and Fisher,
1982). Although slash pines grow faster in diameter
than cypress trees, stem density and height of cypress
trees are usually greater.


Table 2. Rates of gross and net primary productivity (grams of carbon per m2) in Florida cypress swamps


Daily
Gross Primary
Swamp Productivity


South Florida
dwarf cypress
savannah

North Florida
cypress domes2

South Florida
cypress strands3

North Florida
river swamps4


Litter
Fall


110


170-240


300-360


290-400


Annual
Net Primary Productivity
Stem
Growth


20


220-270


90-410


170-540


1Flohrschutz, 1978; Brown 1981
2Mitsch and Ewel, 1979; Deghi et al., 1980; Brown, 1981; Dierberg and Ewel, 1984
3Burns, 1984; Duever et al., 1984
4Mitsch and Ewel, 1979; Brown, 1981; Elder and Cairns, 1982; Richardson et al., 1983


Total


130


410-510


450-770


840








Importance of Water


Hydroperiod is the length of time that water stands
at or above the surface of the ground. It is very impor-
tant in determining the diversity and productivity of a
swamp. When water stands for a long time, oxygen
disappears from the soil, forms of manganese, iron,
and sulfur that are toxic to many plants accumulate,
and much of the available nitrogen escapes to the
atmosphere. Fewer and fewer plants are able to exist
as flooding persists. Therefore, plant diversity serves as
a rough index to hydroperiod. Cypress swamps have
hydroperiods of 6 to 9 months. Cypress trees are
among the most flood-tolerant of all swamp trees.
Once established, they can withstand year-long
hydroperiods indefinitely, although depth of flooding
may limit survival. However, because germination will
not occur if water is standing, the trees cannot regener-
ate in permanently flooded areas.
Moving water, on the other hand, brings in oxygen
and nutrients, increasing both productivity and diversity
(Fig. 2). River swamps that flood for only a short time
once or twice a year thus have a very diverse flora,
whereas backswamps and sloughs, where trapped
water remains for weeks or months after floodwaters
subside, are often characterized by pure stands of
cypress.
Pondcypress trees lose relatively little water through
evapotranspiration, which is the loss of water in
transpiration from the leaves plus evaporation from the
water or soil surface. Both pondcypress and baldcy-
press trees are deciduous, so there is no transpiration
during the winter. Evaporation from cypress ponds is
very low at this time of year (Mitsch, 1984). From April
through October, when cypress trees are in leaf, evapo-
transpiration rates in pondcypress domes are 60% to
80% of pan evaporation rates, which estimate
maximum water loss due to evaporation and transpira-
tion (Heimburg, 1984) and 77% of estimated evapo-
transpiration from slash pine plantations (Ewel, 1984).
Evapotranspiration from baldcypress trees is probably
not as low (Brown, 1981).

Fire

Fire frequency appears to differ significantly between
pondcypress and baldcypress swamps. Pondcypress
swamps occasionally bum during droughts. When
protected from fire, they tend to develop into mixed-
hardwood swamps or bayheads (Monk, 1968; Duever
et al., 1986; Gunderson, 1984; Hamilton, 1984). Fires
reduce the number of species and the relative impor-
tance of broadleaf species, thereby maintaining cypress
dominance in these swamps (Ewel and Mitsch, 1978;
Schlesinger, 1978). The thicker, shaggier bark of


Fig. 2. Cypress tree growing along the Apalachicola
River. Note the silt-laden water, which brings
nutrients to the swamp during flooding, and
the cypress knees at the water's edge.

pondcypress trees may represent an adaptation to a
greater frequency of fire than occurs in baldcypress
swamps.
Fire seldom kills mature cypress trees, although
severe fires may reduce tree vigor for several decades
(Duever et al., 1986). A fire in a pondcypress dome in
north central Florida killed more than 95% of the pines
and hardwoods but only 18% of the cypress (Fig. 3)
(Ewel and.Mitsch, 1978). Even if a fire kills the above-
ground portion of the tree, the root system may survive
if the fire does not penetrate the peat layer, and the tree
may grow back from sprouts. Much of the pondcypress
regrowth after major fires in 1954 and 1955 in the
Okefenokee Swamp was probably from stump sprouts
(Cypert, 1972). Duever and Riopelle (1984) found that
fires in the Okefenokee Swamp are often followed by
the development of even-aged cypress stands.
The natural frequency of fires in unaltered cypress
swamps is probably inversely related to hydroperiod








length and to depth of flooding in the wet season. In
south Florida, fires occur more frequently in cypress
domes than in strands, which may be why the under-
story in domes is less diverse than in strands (Wade et
al., 1980). Cypress returned to most sites after a series
of fires in 1937 in the Everglades that burned deeply
into the peat layer, but it regenerated in very few stands
that burned in 1962 (Craighead, 1971), perhaps
because of a lowering of the water table in the interim.
Drainage that has permanently lowered water tables in
the Coastal Plain of the southeastern United States has
increased fire frequency (Wells, 1942; Duever et al.,
1986).
Fires are infrequent in undrained swamps in the Big
Cypress National Preserve (Duever et al., 1986).
However, increased drainage in south Florida has
allowed fire to encroach farther into swamps than it did
under natural conditions, and swamp species are
unlikely to regenerate in drained swamps after severe
fires unless the natural hydroperiod is restored (Fig. 4)
(Wade et al., 1980).
Low water levels accompanied by an accumulation
of organic matter increase susceptibility to fire. If a fire
burns into the deep peat in the center of a cypress
dome, cypress mortality will increase; if enough
organic matter has accumulated around the edges of a
dome that has been dry for a long time, fire can
eliminate cypress completely (Ewel and Mitsch, 1978).


Seed Production, Dispersal, and Germination

Regeneration of cypress from seed apparently
requires a well-defined set of conditions (Table 3).


Fig. 3. A freshly burned cypress pond in north
Florida. Most of the cypress trees in this
swamp survived the fire.


Natural stands of cypress tend to be even-aged
(Putnam, 1951; Stubbs, 1973), and ring counts have
shown that groups of cypress saplings tend to be
about the same age, although their sizes may vary
within each group (Demaree, 1932; Schlesinger, 1978;
Duever and Riopelle, 1984). Cypress regeneration
requires seed production followed by hydrologic
conditions conducive to germination and seedling
growth.
The quantity of seed produced varies from year to
year (Schlesinger, 1978). In swamps, some seed
seems to be produced every year, and a bumper crop
is believed to be produced every 3 years (Mattoon,
1915). This rule of thumb seemed to hold for unaltered
pondcypress domes in Florida during a 3-year period;
in a dome receiving treated wastewater, however, seed
production was high in all 3 years (Brown, 1978).
Baldcypress trees growing along a river bank in north
Florida produced seed every year for at least 4 years.
No minimum age has been documented at which
cypress trees begin to bear viable seed. Cones were
produced by baldcypress in the third year after 1-year-
old saplings were transplanted (Deghi, 1984). We
observed cone production on 1- to 2-year-old stump
sprouts in the Withlacoochee State Forest in central
Florida.
Cypress cones ripen in October, November, and
December (Fowells, 1965). They usually disintegrate on
the tree, but they sometimes fall to the ground in one
piece (Duever et al., 1986). The seeds are probably
dispersed primarily by water (e.g., Harper, 1927;
U.S.D.A. Forest Service, 1948; Kennedy, 1972; Stubbs,
1973; Williston et al., 1980), and in very wet weather
they may be carried by slowly moving floodwaters


Fig. 4. A south Florida swamp that did not survive
burning, perhaps because of drainage.
(Photograph byJ. Ewel)








Table 3. Influences on the life cycle of a cypress tree


Important Factors


Increases Success


Decreases Success


Fire?
Sewage?


Seed production


Seed dispersal


Key animal species?


Germination


Seedling survival


Coppice production


Pre-soaking
Alternating water temperature
Alternating water level


Adequate soil moisture
Less than full
sunlight


Full sunlight?
Light burning


High water level
Extended flood duration


Extended flood duration
Prolonged drought
Fire
Herbivory by small mammals

Intensive burning


across flatwoods from one pond to another (Harper,
1927). Although the seeds appear to be adapted for
floating, only one-third of a sample of pondcypress
seeds from the Okefenokee Swamp actually did float
(Conti and Gunther, 1984).
Dispersal by water alone may therefore be insufficient
to explain the distribution of cypress, particularly
among rolling hills such as in west Florida. Cypress
seeds are eaten by some animals, including squirrels,
turkeys, sandhill cranes, gadwalls, and mallards (Martin
et al., 1951; Bateman, 1959), although the pockets of
resin in the cones may deter consumption by many
birds and rodents (Kennedy, 1972). Nevertheless,
squirrels might have carried the seeds about the
landscape and cached them (Harper, 1927). Robins,
bluebirds, blackbirds, and cedar waxwings may also be
agents of cypress seed dispersal (DeBell and Hook,
1969).
Cypress seeds were a significant part of the diet of
the Carolina parakeet, which became extinct by the
1920s. This bird could travel long distances in short
times, and it might have had a role in seed dispersal
(Duever et al., 1986). Neither the effect of digestion on
cypress seed viability nor the nutritional value of
cypress seed has been examined, but other bird
species are known to consume seeds of cypress and
other conifers. The digestive processes of some
fruit-eating birds help soften the woody husks of some
seeds, thereby facilitating sprouting after the seeds are
eliminated (Dorst, 1971). Whether Carolina parakeets
were important in dispersing cypress seed will probably
never be known.


The germination rate for cypress seeds ranges from
9% to 87%, with an average of 40% to 60% (Kennedy,
1972). Seeds may remain viable for a year or more if
they are kept under water, although baldcypress seeds
that had been submerged for 14 months did not
germinate (Applequist, 1959). However, a few seeds
sprouted after having been stored for 30 months in jars
of water (Demaree, 1932). Cypress seeds will not
germinate without some pretreatment, such as
soaking, to soften the seedcoat (Murphy and Stanley,
1975); but as long as the seeds are inundated, they
will not germinate (Demaree, 1932). Although the
minimum time required for soaking has apparently not
been determined experimentally, more than 80% of
the seeds tested by Murphy and Stanley germinated
after soaking in warm water for 30 days.
Temperature might also be an important parameter
in determining the rate of germination. In an experi-
ment using presoaked seeds from the Okefenokee
Swamp, none germinated while temperature was held
constant at levels ranging from 10 to 310 C, whereas
80% or more germinated after being subjected to
gradual (but unspecified) temperature alternations
(Conti and Gunther, 1984). Alternating temperatures
can rupture hard seedcoats by causing the seed to
expand and contract.
If a specific range of temperatures and a moist (but
not flooded) seedbed are required for germination,
successful reproduction seems unlikely in most years.
Although baldcypress seeds will germinate as late as
midsummer if conditions are too wet for spring
germination (Putnam et al., 1960), younger seedlings


Stage


Drainage








are more susceptible to winter freezing (Mattoon,
1915). Water levels are not likely to be low in summer
in many places. Summer is Florida's rainy season, and
swamps may be dry for a long enough time to allow
germination only once or twice in a decade. In the
deeper swamps of North Carolina's Coastal Plain, water
levels fall to the soil surface only once every 10 to 20
years (Wells, 1942). Louisiana cypress swamps, on the
other hand, are usually flooded only during winter and
spring (Applequist, 1959).

Seedling Survival

Seedlings are more likely to survive brief periods of
inundation under clear, cool water than under warm,
turbid water (Putnam et al., 1960). However, there is
disagreement about the effects of inundation during
the growing season on survival of first- and second-year
seedlings. Demaree (1932) and Williston et al. (1980)
reported that seedlings cannot tolerate any flooding. In
Louisiana, cypress seedlings were killed by more than
2 weeks of flooding in the spring and summer and by
more than 3 weeks of flooding after leaf-drop in the fall
(Rathborne, 1951). Putnam (1951) found that sub-
mergence during the dormant period of flood-tolerant
tree species, including cypress, is not detrimental;
continued submergence into the growing season
simply prolongs dormancy, but the trees will resume
growth after water levels subside. Once buds have
opened, however, no species except willow can survive
more than a few days underwater.
Others have observed that cypress seedlings can
survive flooding after they have leafed out. In a study
of planted 1-year-old seedlings, 67% survived 20 days
of submergence at the beginning of the growing
season; 55% survived 20 to 29 days; and 31%
survived 30 to 45 days (Bull, 1949). Baldcypress
seedlings put out new leaves in August following
several months of complete submergence after they
had leafed out in the spring (Krinard, 1959).
One-year-old baldcypress seedlings survived after
being covered with 0.6 meter (2 feet) of oxygenated
(average 7 ppm 02) water for periods up to 4 weeks,
but growth rates varied during the 5 months following
their release from flooding (Loucks and Keen, 1973).
Best growth was measured on seedlings that had been
under water for 2 weeks.
At the other extreme of water stress, cypress seed-
lings are apparently sensitive to drought. Although
wilted cypress seedlings may recover quickly when
watered (Mattoon, 1916), 4- to 6-week-old baldcypress
seedlings exposed to drought were irreversibly dam-
aged within 3 to 4 hours (Dickson and Broyer, 1972).
In the Okefenokee Swamp, cypress trees are more
likely to become established during droughts


(Schlesinger, 1978; Duever and Riopelle, 1984), and
there is evidence of a 25- to 30-year cycle of drought
and fire (Izlar, 1984a).
When drainage causes prolonged drought, cypress
may be outcompeted by shrubs and hardwoods.
Swamp hardwoods are replacing cypress in southwest
Florida where the water table is receding (Craighead,
1971). Densities of hardwood and shrub species
increased in drained pondcypress domes in north
Florida (Marois and Ewel, 1983).
The optimal soil conditions for cypress seedlings
appear to include adequate aeration and abundant soil
moisture. In greenhouse experiments with 4- to
6-week-old baldcypress seedlings, those in flooded,
aerated soil grew about twice as much in 3 months as
those in unsaturated, but moist, soil (Dickson and
Broyer, 1972). In experiments on nutrient uptake,
2-month-old baldcypress seedlings in saturated,
aerobic soil absorbed more nutrients than did seedlings
in saturated, anaerobic soil or in unsaturated soil
(Dickson et al., 1972).
Seedlings grown in the wild commonly reach heights
of 20 to 25 centimeters (8 to 10 inches) in the first
growing season and 40 to 50 centimeters (16 to 20
inches) in the second season (Mattoon, 1916). They
can reach 1.2 meters (4 feet) in 4 years (Betts, 1938).
Such rapid early growth may be an evolved response
to the risk of inundation by rising water levels (Mattoon,
1916). However, mortality can be high; 66% of a group
of wild seedlings died after two growing seasons,
probably because they were inundated (Deghi, 1984).
Deghi found the survival rate of planted baldcypress
and pondcypress seedlings to be much higher than
that of seedlings that had germinated in situ.
Assessments of the light requirements of cypress
seedlings range from very intolerant (Zon and Graves,
1911) to intolerant (Hamilton, 1984) to moderately
tolerant (Mattoon, 1915; Stubbs, 1973; Williston et al.,
1980) to tolerant (Putnam, 1951). In shade-house
experiments, the increase in biomass of baldcypress
seedlings was greatest under 80% of full sunlight,
while the increase in height was greatest under 32% of
full sunlight (Browder et al., 1974). Seeds often sprout
under heavy shade but do not survive into the second
year (Demaree, 1932). Crowding or shading may
interfere with pondcypress regeneration; the density of
pondcypress seedlings in north Florida domes is
inversely related to the density of herbs, shrubs, and
other trees (Terwilliger and Ewel, 1986).
Uprooting or clipping of seedlings by herbivores
destroyed more than 90% of planted 1-year-old
seedlings in a Louisiana study (Blair and Langlinais,
1960). Further studies showed that nutria (Myocaster
coypus) and swamp rabbits (Sylvilagus aquaticus)
were responsible.








Regeneration by Coppice

Both pondcypress and baldcypress stumps will
sprout (Mattoon, 1915) (Fg. 5). More than 350 shoots
coppicee) were recorded on one stump in a study of
regeneration in several central Florida pondcypress
domes, although most stumps had fewer than 10
sprouts (Ewel, 1985). Among more than 350 stumps
in eight swamps in central Florida, stumps that
produced no coppice were taller, averaging 72 centime-
ters (28 inches),than stumps that did produce coppice,
which averaged 65 centimeters (26 inches). Many
sprouts do not survive even the first growing season,
however.
The amount of light reaching a stump may determine
whether it will sprout. Brush around stumps must be
cleared in order to expose dormant buds on the
stumps to light (Zon and Graves, 1911). In north
Florida, few cut trees sprouted in pondcypress domes
that had been selectively logged; in a clearcut dome,
almost all the stumps had coppiced, possibly because
of the greater amount of light reaching them (Marois
and Ewel, 1983). A central Florida dome that was
clearcut in the 1940s also recovered because of a high
rate of coppicing.
Stumps left from harvested trees in central Florida
sprouted along their entire length (Ewel, 1985). This
may be common in drier habitats, such as along the
Atlantic coast. Stumps in wetter areas, such as near the
Gulf coast and in the Mississippi Valley, generally sprout
only from the tops (Mattoon, 1915). In a study of
stump sprouting of swamp tupelo (Nyssa sylvatica var.
biflora), more than twice as many suppressed buds per
unit of surface area were found between 15 and 30
centimeters (6 to 11 inches) above the ground than


Fig. 5. Stump sprouts coppicee) on a cypress stump
in central Florida.


between ground level and 15 centimeters (6 inches)
above the ground; buds on the lowest parts of the
stumps might have been drowned (DeBell, 1971).
If logging slash is left lying on stumps, subsequent
sprouts will be few, spindly, and poorly formed (Blake,
1983). Other logging practices that interfere with
sprouting are girdling (Mattoon, 1915), debarking of
stumps, and burning severe enough to damage the
cambium (Neal, 1967). Light burning facilitates later
sprouting, probably by increasing the exposure of
stumps to light (Neal, 1967).
Redwood (Sequoia sempervirens) is related to
Taxodium, and redwood coppice survival is related to
light intensity and number of sprouts (Cole, 1983).
Diameter and height growth of unthinned sprouts and
of sprouts thinned at age 2 were monitored for 33
years. Best growth was found in sprouts growing in full
sunlight with little or no competition from surrounding
vegetation. No significant differences in growth were
found between the thinned group and the unthinned
group. However, sprouts growing in moderate light and
with intermediate levels of competing vegetation grew
significantly better when left unthinned. Poorest growth
was found in sprouts that received little or no direct
sunlight and were also heavily affected by competing
vegetation. These results support the theory that some
minimum number of sprouts is necessary to maintain
a healthy root system; more sprouts, and hence more
photosynthetic surface, are required to maintain the
root system where stumps and sprouts are not in full
sunlight.
Sprouts from older cypress stumps may not be as
vigorous as those from younger ones, and they may
be more susceptible to wind damage (Langdon, 1958).
Writing about coppice in general, Stewart (1980) noted
that trees grown from stump sprouts usually develop
defective butt logs and are vulnerable to diseases
entering through the old stump. Butt rot is more likely
to occur in trees that have developed from sprouts on
the higher parts of stumps and in suppressed, low-vigor
trees (Blake, 1983).

Use of Cypress Swamps by Wildlife

Because of the frequency of heart rot in cypress
trees, cavities are frequently used as nesting sites by
both birds and mammals. In general, however, food
production and cover in cypress swamps are limited by
their sparse understory, infertile soils, and fluctuations
in water level. Although no extant vertebrate species
are known to use cypress swamps exclusively for
habitat, many make some use of them for cover,
breeding, and/or feeding.
Of 234 terrestrial vertebrate species in the Big
Cypress National Preserve, 24% use cypress forests








commonly, and another 31% use them rarely (Duever
et al., 1986). Large cypress swamps provide cover for
deer, bobcats, and small mammals such as raccoons,
rabbits, and rodents (Davis, 1943). Birds that nest in
cypress forests in south Florida include wood storks,
snowy egrets, little blue herons, green-backed herons,
great blue herons, swallow-tailed kites, turkeys, black
vultures, white ibis, and several species of owls,
woodpeckers, and warblers (Duever et al., 1986). In
north Florida, reptiles and amphibians dominate the
cypress pond fauna during summer, and birds domi-
nate in winter (Harris and Vickers, 1984).


Impact of Insects and Diseases

The cypress leaf beetle (Systena marginalis) can
cause reddening of foliage over large areas (Barnard
and Dixon, 1983) and probably decreases growth
(Chellman, 1971). Another agent of foliage discoloration
is the red spider mite (Tetranychus spp.), which can
reduce growth and make trees more susceptible to
other pests (Putnam et al., 1960). The cypress looper
(Anacamptodes pergracilis) was responsible for
defoliating nearly 11,340 hectares (28,000 acres) in the
Big Cypress National Preserve in 1980; it may also
cause branch dieback (Dixon, 1982). Bacillus thuringien-
sis is a potential control for this caterpillar (Dixon,
1982).
The most serious predator of cypress cones may be
the baldcypress coneworm, Dioryctria pygmaeella,
whose larvae apparently feed exclusively on seeds of
pondcypress and baldcypress. In 1978, 75% or more
of the cones on north Florida host trees were infested


Fig. 6. Extreme butt swelling on cypress trees.
Compare with tree in Fig. 2. (Photograph byJ.
Ewel)


(Merkel, 1982), although the viability of infested seed
was not determined. In the following year, fewer than
1% of the cones on the same trees were infested. The
baldcypress coneworm is difficult to detect because the
cones remain green after the moths emerge. Pine
coneworms, D. ebeli and D. amatella, also occur in
cypress cones (Merkel, 1982).
Other cypress pests are fall webworms (Hyphantria
cunea), whose larvae feed on cypress needles, and
cicadas (Diceroprocta and Tibicen spp.), which lay eggs
in slits torn through the bark (Barnard and Dixon,
1983). Girdled trees in the Fahkahatchee Strand in
south Florida were attacked by ambrosia beetles
(members of the families Platypodidae and Scolytidae)
(Craighead, 1971).
The fungus Cercospora sequioae, which causes
needle blight disease, infects baldcypress in Japan
(Kobayashi, 1980). It was introduced from the United
States early in this century on Taxodium mucronatum
specimens. In severe infestations, needle blight disease
can almost completely defoliate the host tree.
Pecky cypress heartwood is caused by the fungus
Stereum taxodii, which represents a serious threat to
production of high-quality lumber in Florida (Chellman,
1971). Roth (1898) said pecky cypress looks "as if a
number of small pegs, 1/4 to 1 inch thick, had been
driven into the log, then withdrawn, and the holes filled
with powdered, decayed wood." Wind-dispersed
spores usually enter a tree through the crown. Trees
with basal cavities, broken tops, or woodpecker holes
are almost always pecky. The fungus is not fatal, but it
could weaken the tree and make it vulnerable to wind
damage (Chellman, 1971).


Forestry Practices and Lumber Production

Mensuration

Estimating the volume of wood in cypress trees is
not easy. One difficulty is deciding where on the stem
to measure diameter. Diameter at breast height (dbh),
(1.4 meters, or 55 inches above ground) is not always
appropriate because of irregularity in the height, shape,
and degree of butt swelling (Fg. 6) (Hotvedt et al.,
1985). The few tables of equations that have been
formulated for cypress volume are therefore not all
based on the same point of measurement. On the
other hand, the high degree of irregularity in cypress
may be an advantage. Tables constructed with data
collected from only a small part of the species' range
may be applicable throughout the commercial range of
cypress because of the wide variation in cypress
growth rates within any particular locality (Mattoon,
1915).








Volume tables have been compiled with data
collected in Maryland, South Carolina, and Louisiana,
presumably from baldcypress trees (Mattoon, 1915). In
these tables, diameter at 6 meters (20 feet) above
ground, number of merchantable logs, and diameter at
the top of the first 5-meter (16-foot) log are related to
board feet using the Scribner, Doyle, and two-thirds log
rules.
A table for well-managed, even-aged tupelo stands
that could be "roughly adjusted" for application to
cypress relates average diameter above bottleneck
(measured at 0.60 to 0.75 meter [2 to 2.5 feet] above
the butt swell) to basal area, number of trees, and
average volume per acre (Putnam et al., 1960). For
fully stocked oak-gum-cypress stands on medium and
high sites, tables of volumes per acre, basal area per
acre, and number of live trees per acre by dbh class
were formulated by McClure and Knight (1984).
Volume tables constructed for pondcypress in north
central Florida relate total height and either dbh or
"diameter head height" (taken at 2 meters [6.5 feet]
above the ground) to volume in cubic feet and in board
feet (Scribner rule) (Swinford, 1948). Swinford also
assembled a table relating dbh and number of 5-meter
(16-foot) logs to volume in board feet (Scribner rule).
Volumes calculated from diameter head height were
more accurate than those calculated from dbh, because
the former point is less affected by butt swell than the
latter.
Two tables of merchantable volume are available for
baldcypress in the south Delta region of Louisiana,
using diameter taken at 45 centimeters (18 inches)
above butt swell (called "normal diameter") or at 3
meters (10 feet) above ground (Hotvedt and Parresol,
1982). The volume equation based on diameter at 3
meters fits the data more reliably than the equation
based on normal diameter. Using diameter at 3 meters
also yielded more accurate equations for total volume
than did normal diameter when a larger sample size
was used (Hotvedt et al., 1985). Regression equations
for estimating biomass of pondcypress and baldcypress
using dbh are listed by Brown (1978).
Another difficulty in cypress mensuration arises in
measuring the age of cypress trees. False rings, which
may result from soil-moisture fluctuations, are common
in cypress trees; including false rings in a tree-ring
count can lead to overestimates of age and, con-
sequently, underestimates of growth rates. Planted
cypress averaged 28 rings in 17-year-old trees, 30 rings
in 19-year-old trees, and 32 rings in 20-year-old trees.
A magnification of at least 20X facilitates distinguishing
false rings from true ones (Beaufait and Nelson, 1957).
If growth rates rather than ages are desired, averaging
growth estimates over 6 to 10 years reduces the error
associated with false rings (Ewel and Parendes, 1984).


Timber Production and Standing Stocks

No surveys are available that differentiate between
pondcypress and baldcypress volumes. The earliest
appraisal of total standing cypress sawtimber was
made in 1897 by Mohr (in Mattoon, 1915), who
estimated 33 billion board feet. (These data cannot be
converted easily into metric units.) That figure was
revised to 40 million board feet in 1909; nearly 39% of
all standing sawtimber approximately 15.7 billion
board feet was in Louisiana (U.S. Department of
Commerce, Bureau of Corporations, 1914).
Early in the twentieth century, new markets for
cypress were opened by the expansion of the railroad
system (Stemitzke, 1972), and cypress dealers
mounted a massive effort to develop a national market
(Bums, 1980). The publicity campaign started out by
suggesting the use of cypress for "necessities and
conveniences" such as trellises and garden furniture,
and later promoted its use in farm buildings and
"homemade furniture and knick-knacks" (Anonymous,
1916). Uses of cypress ranged from installation of
hollowed logs for water mains in New Orleans to the
manufacture of birdhouses and beehives from knees.
The advertising campaign was successful. Production
of cypress lumber went from 495 million board feet in
1899 to a peak of 1,097 million board feet in 1913
(Betts, 1938); from 1899 to 1925, average annual
production of cypress lumber was 798 million board
feet (U.S. Department of Agriculture, 1927).
In 1920, the U.S. Forest Service calculated that the
amount of standing cypress sawtimber had dropped to
22.9 billion board feet, a decline of more than 40%
since the 1909 survey (Betts, 1938). In 1933, the
Forest Service's estimate of standing sawtimber fell to
4.1 billion board feet, about 10% of the 1909 figure.
The cypress industry collapsed even faster than it
had boomed. By the Great Depression, most of
Louisiana's virgin cypress forests had been cut over,
and most of the state's cypress mills had been shut
down (Bums, 1980). The decline in the harvest of
cypress has been attributed to economic and physical
constraints imposed on forestry operations by wet site
conditions (Jackson and Morris, 1986). In addition,
most of the larger, readily accessible stands of old-
growth timber had already been cut. In 1933, cypress
lumber production had fallen to 158 million board feet;
in the early 1930s, Florida overtook Louisiana as the
leading cypress-producing state. In 1931, 144 million
board feet were produced in Florida, while only 52
million board feet came from Louisiana (Anonymous,
1934).
By 1936, total production had risen again to 441
million board feet (Betts, 1938), but by 1943 it had
dropped back to 254 million board feet (Betts, 1945a).








Average annual production of cypress lumber from
1945 to 1954 was 247 million board feet; in 1954,
about 25% of it came from Florida, 14% from
Louisiana, and the rest from 19 other states (Betts,
1960). In 1972, Sternitzke estimated the harvest of
balcypress to be roughly 69 million cubic feet.
Since the 1930s standing sawtimber volumes have
increased steadily. In 1939, the amount of standing
sawtimber was estimated to be 11.6 billion board feet
(Betts, 1945a). At the start of 1953, the Forest Service
(1958) found 12.7 billion board feet of cypress on
commercial forest land; 25% of it was in Florida, and
19% in Louisiana. Between 1953 and 1963, the
volume of cypress growing stock increased 25%, from
93 to 116 million cubic meters (3.3 to 4.1 billion cubic
feet); during that decade, growing stock increased 61%
in Florida and 35% in Louisiana (Southern Forest
Resource Analysis Committee, 1969). In 1965, there
were 17.2 billion board feet of standing timber: 32% in
Florida, 26% in Louisiana, and 24% in Georgia, North
Carolina, and South Carolina (Kennedy, 1972). The
most recent Forest Service estimate (1978) set the
amount of standing sawtimber at 19.8 billion board
feet at the beginning of 1977.
Most present-day cypress stocks are relatively young.
Because it takes at least two centuries for cypress to
develop an appreciable proportion of decay-resistant
heartwood (Betts, 1938), and because second-growth
trees contain a larger proportion of sapwood than do
virgin trees (Betts, 1960), young second-growth trees
are unsuited to the kinds of uses for which cypress
was dubbed "the wood eternal" in the heyday of
cypress logging. However, use of cypress lumber
remains popular. Pondcypress is primarily used for
fenceposts, stakes, mulch, and pulp (Terwilliger and
Ewel, 1986), although fenceposts made from pondcy-
press sapwood were found to last less than five years
(Applequist, 1957).


Logging Practices

Mattoon (1915) sketched the early history of cypress
logging techniques. The first cypress forests to be
harvested extensively by white settlers were near the
mouths of the larger southern rivers. Logs were floated
out of the swamps, a practice that caused very little
destruction of the remaining growing stock.
The practice of girdling, or belting, cypress trees
dates back to these early loggers. A few months before
the timber was to be cut, an incision was made
completely around the stem of each tree that was to be
harvested. This cut had to extend through the sapwood
to the heartwood to ensure death of the tree and
subsequent drying. Without girdling, 10% to 20% of


the logs would float, whereas 6 months after girdling
95% would float. Girdling was also popular because
skidding tongs were less easily dislodged from dead
wood than from green wood, because heartwood of
green cypress would swell during milling and bind the
saws, and because green cypress has a greater
tendency to mildew after sawing (Mancil, 1980).
Stumps of girdled trees would not sprout, however,
and trees girdled in the spring were subject to attack by
ambrosia beetles (probably members of the families
Scolytidae or Platypodidae), which considerably
reduced the quality of the lumber. This problem was
avoided by girdling trees in late summer and letting
them dry during the winter, when the beetles are
inactive (Craighead, 1971).
Other logging practices were detrimental to the
remaining trees. In the 1890s, dredges were used to
clear passageways into deeper swamps, and engines
mounted on pullboats were used to skid out logs by
dragging them along the ground up to 600 meters
(2,000 feet), causing considerable damage to the
remaining stand. Early in the twentieth century, loggers
began building railroads on pilings into swamps that
were not sufficiently flooded to support floatation
logging, and they constructed steam-powered overhead
cableway skidders to remove the logs. In the
Okefenokee Swamp, cables were run from a spar tree

18.5 meters (60 feet) high to trees growing on the
edges of each 185-meter (600-foot) "skidder set" (Izlar,
1984b). Trolleys on the cables pulled logs to railway
flatcars for transport to the mill. The volume of wood
removed was as high as 350 cubic meters per hectare
(5,000 cubic feet per acre), or 5,670 cubic meters
(200,000 cubic feet) per "setup." The overhead skidder
destroyed nearly all the uncut trees in its path (Mattoon,
1915). Several decades after the end of logging in
Louisiana's Atchafalaya Basin, only a little second-
growth timber could be found where pullboats and
railroads had been used to extract the timber (Kennedy,
1969).
In the 1950s, May Brothers of Garden City, Louisiana,
took out a patent on an elaborate swamp-logging
technique (Anonymous, 1959). Their scheme involved
building levees 1.8 meters (6 feet) high around forest
blocks that ranged from 485 to 1,010 hectares (1,200
to 2,500 acres). During levee construction, trees were
girdled and aquatic skidways were cleared. Once the
levee was completed, water was pumped into the
block to a depth of 1 meter (3 feet). The logging crew
would then cut the trees with chain saws and cross-cut
saws. The logs were floated to the levee and loaded on
barges for transport to the mill.
At present, most cypress harvesting is done with
rubber-tired feller-bunchers and skidders (Fig. 7).
Tracked vehicles are also used for harvesting swamps



























Fig. 7. A rubber-tired skidder pulling logs from a
cypress swamp.

(Priegel, 1981), but they cost more than twice as much
as their rubber-tired counterparts and are more
expensive to repair (Koger and Patrick, 1981). Both
rubber-tired and tracked vehicles can ruin productive
wetland soils by compaction (Priegel, 1981). Increased
soil bulk density impedes root penetration, reduces
aeration, and restricts the movement of air and water
in the soil (e.g., Hanna, 1981), although it is not clear
how much Florida's sandy soils may be affected.
Advance regeneration is crushed by machines, and
cypress seeds may not germinate as well in compacted
soils where drainage has been impeded. Machines skin
the bark off stumps, decreasing the likelihood of
sprouting, and damage remaining trees, making them
vulnerable to invasion by insects and fungi.
In spite of the damage they cause, cable-yarding
systems like those used until the 1940s have been
recommended as best for year-round logging in very
wet sites (Priegel, 1981). Skyline systems, which carry
more of the tree's length off the ground, cause less
damage to remaining trees and to soil (Czerepinski,
1985).
Airborne systems, such as hot-air, propane-fueled
balloons capable of hoisting 4,500 kilograms (5 tons),
have been suggested for transporting logs where
road-building is infeasible (McDermid, 1969). Helicopter
logging might be economically justifiable where there
are large volumes of high-quality timber and road
building costs are prohibitive (Priegel, 1981).

Cypress Regrowth Following Logging

Even before the turn of the century, some foresters
predicted that cypress would not regenerate after it was
harvested:


The supply of cypress is considerable and the
output is capable of material increase, but once
gone, the present forests will be unable to replace
the supplies, and it is doubtful whether cypress can
be thought of as a timber of the future (Roth 1898).
After the era of intensive logging, cypress did not
regenerate in cutover swamps where there were not
enough seed trees and where water levels were higher
than they were when the forests were established
(Betts, 1938). Cypress reproduction was more abun-
dant where cutting had been "conservative" versus a
"clean sweep" (Mattoon, 1915). Very little regeneration
of baldcypress was found in cutover areas in southwest
Florida where only a few remnant cypress trees were
left, and no regeneration was found in areas previously
dominated by baldcypress that had been both logged
and burned and where no cypress trees had been left
standing (Gunderson, 1984).
Regeneration of cypress-tupelo swamps may not be
successful unless all competing plants except annual
herbs are eliminated (Putnam, 1951). Eight years after
harvest of an uneven-aged stand of baldcypress, water
tupelo, and swamp tupelo in a North Carolina river
swamp, the site was dominated by black willow (Salix
nigra). Clumps of young cypress and tupelo saplings
were found where seed sources or advance regenera-
tion had not been obliterated by skidders (Allen, 1962).
Selective cutting of cypress from mixed swamps may
allow the remaining species to assume dominance.
The practice of harvesting cypress and leaving water
tupelo (which was considered worthless) has resulted
in dominance of some swamps by water tupelo
because it became the dominant seed source (Betts,
1945b), and because tupelo seedlings are abundant in
undisturbed swamps (DeBell and Auld, 1971). After
cypress was removed from the mixed swamp forests
of the Big Cypress National Preserve, remaining
subcanopy hardwoods assumed dominance (Duever et
al., 1986). However, Wade et al. (1980) found that
cypress was returning in many such swamps.
Rates of pondcypress reestablishment were high in a
study of north and central Florida pondcypress domes
that had been selectively cut (Terwilliger and Ewel,
1986). According to Stubbs (1973), clearcut baldcy-
press-swamp tupelo forests regenerate well if water
levels stay low and competing vegetation is reduced as
a side effect of harvesting.

Silvicultural Systems

Silvicultural systems that have been used in cypress
swamps range in intensity from clearcutting to thinning.
Because natural stands of cypress tend to be even-aged
(Putnam, 1951; Stubbs, 1973), the most frequently
prescribed silvicultural systems are clearcutting and





























Fg. 8. A clearcut cypress swamp in central Florida.

seed-tree cutting. However, there is no clear evidence
supporting any one method. The major areas of
concern are damage to remaining trees, subsequent
regeneration, and degree of growth response after
thinning or other forms of partial cutting.
Clearcutting (Fig. 8) has been defended as a method
of ensuring good post-harvest stocking (e.g., Hanna,
1981). Arguments supporting clearcutting are based on
good regeneration that has been observed on experi-
mentally clearcut plots, the efficient use of labor and
equipment in swamps that are not readily accessible,
and the economic impracticality of removing low
volumes in intermediate thinnings (McGarity, 1979). A
vegetation analysis of ten swamps in central Florida
showed that in the absence of fire, cypress seedlings
and sprouts are dominant among the woody species
(Ewel et al., 1989). Lack of regeneration in a baldcy-
press stand where no trees had been left after logging
and burning (Gunderson, 1984) suggests that a nearby
seed source and absence of fire are necessary for
baldcypress reproduction.
Seed-tree cutting is favored by the fact that advance
regeneration of cypress is usually sparse (Stubbs,
1973; Johnson, 1981; Best et al., 1984). Cypress seed
is relatively immobile, and seed trees can be left as
long as it takes to establish a new stand after harvest-
ing. Good natural regeneration has been observed in
cypress forests in which trees have been left standing.
For instance, Terwilliger and Ewel (1986) found that
pondcypress regained its apparent original basal area
and dominance within 45 years after selective logging.
Recommendations have included leaving a heavy
shelterwood of 75 to 100 trees per hectare (30 to 40
trees per acre) where there is little advance regeneration
(Stubbs, 1973) and 10 to 20 trees per hectare (4 to 8


---
f !I__
''
'"-ilal


trees per acre) with diameters of 25 to 46 centimeters
(10 to 18 inches) (Mattoon, 1915).
Some have found that thinning out smaller trees can
be profitable (e.g., Johnson, 1979). Mattoon (1915)
recommended thinning in small stands of pole-sized
cypress and in dense second-growth stands to give
better trees more space for crown development. Bull
(1949) suggested thinning out poorer individuals at age
70 and holding the best trees until age 100 because
the rate of increase in volume would still be high.
Evidence of enhanced growth of remaining trees was
provided for baldcypress by McClurkin (1965), Williston
(1969), and McGarity (1979), but Terwilliger and Ewel
(1986) found that selective logging did not increase the
growth rate of remaining pondcypress trees.
McGarity (1979) preferred clearcutting to thinning.
However, if early returns are desired, he recommended
thinning to a basal area of 16 to 18 cubic meters per
hectare (70 to 80 cubic feet per acre). He found that
this degree of thinning left enough trees to utilize the
site fully, and these so-called "leave" trees showed the
same amount of diameter growth as did trees in more
severely thinned stands.
Williston et al. (1980) advocated two thinnings before
the final cut. The first, between the ages of 15 and 20
years, would yield fenceposts, but more importantly,
would relieve the stagnation caused by the overstocking
that can follow clearcutting. They advised leaving at
least 750 trees per hectare (300 trees per acre);
otherwise, the trees would not lose their lower limbs,
resulting in undesirable knots in the wood (Smith,
1962). Mattoon (1915) also pointed out that side
shading accelerates height growth and natural pruning.
The second thinning, 10 years after the first, would
yield poles and other small products.

Planting

To ensure cypress regeneration, Bull (1949)
suggested planting seedlings tall enough to avoid
inundation. Seedlings raised in a nursery by Gooch
(1953) averaged 75 to 100 centimeters (30 to 40
inches) in height at the end of the first growing season.
Rathborne (1951) found that seedlings 75 centimeters
(30 inches) tall or greater were large enough to survive
flooding in an experimental Louisiana planting.
Bull recommended a 2-meter by 2-meter (6-foot by
6-foot) or 2.5-meter by 2.5-meter (8-foot by 8-foot)
spacing. Krinard andJohnson (1976) planted 896
seedlings on a 2-meter by 3-meter (6-foot by 10-foot)
spacing. The plantation was cultivated three or four
times annually for the first 4 years and mowed once a
year for the next 6 years. After 21 years, 41% of the
trees had survived, and their average diameter was
15.5 centimeters (6.1 inches).








Water Management

Cypress swamps play a complex role in regional
water budgets. Like most freshwater wetlands, they are
important in flood protection, although different kinds
of swamps accomplish this in different ways. River
swamps slow the velocity of water during flooding,
damping the severity of flooding downstream and
removing some of the silt from floodwaters. Isolated
wetlands are more subtle in their effects, storing runoff
before it reaches lakes and streams. During dry
periods, slow evapotranspiration from pondcypress
swamps allows more infiltration of surface water into
groundwater (Heimburg, 1984). This pattern of storage
during times of water abundance and release during
times of water shortage alleviates the effects of uneven
distribution of rainfall over the year in areas with
abundant wetlands (Littlejohn, 1977).
The Green Swamp is a 223,400-hectare (550,000-
acre) region in west-central Florida where wetlands
occupy roughly 30% of the surface area. About
two-thirds of the wetlands, or 45,500 hectares (112,000
acres), are cypress domes and strands. A regional
water budget showed that the infiltration rate of water
from wetlands to the surface aquifer was roughly three
times the rate of infiltration from upland areas (Brown,
1984). Simulating drainage of wetlands showed that
the level of the surface aquifer progressively declined as
the proportion of drained wetlands increased; draining
80% of the area's wetlands caused a 45% reduction in
the amount of water available to the area.
Cypress strands and domes have also been used for
disposal of wastewater that has undergone secondary
treatment (Fig. 9). Such systems can remove more
than 90% of the organic matter, nutrients, and minerals


A norm nonaa cypress ponu oemng useu lor
advanced wastewater treatment.


from wastewaters before they reach groundwater
(Dierberg and Brezonik, 1984). Major changes observed
in swamps receiving treated effluent are the develop-
ment and persistence of a continuous cover of
duckweed (Lemna spp., Spirodela spp., and Azolla
carolinensis) (Ewel, 1984), development of anoxia in
the water (Dierberg and Brezonik, 1984), and an
increase in passerine bird populations together with
elimination of amphibian reproduction (Harris and
Vickers, 1984).
Significant increases in growth rates have been
measured in pondcypress trees growing in swamps
receiving treated effluent. The basal area increment
(bai) per tree of pondcypress in a north Florida strand
that had been receiving wastewater for 41 years was
twice the bai of trees in a nearby dome that did not
receive effluent (Nessel et al., 1982). Similar results
were obtained in two north Florida pondcypress
domes, one that had received secondary effluent for a
short time and one that had received runoff from
fertilized farmlands and feed pens (Brown, 1981).
However, addition of raw sewage and primary wastewa-
ter depressed pondcypress growth rates in parts of
another north Florida strand, apparently due to the
development of severe reducing conditions (Lemlich
and Ewel, 1984).
Although regeneration in such swamps may occur
during a scheduled drydown or even during a summer
drought, planting seedlings is probably necessary for
long-term ecosystem maintenance. Pondcypress
seedlings planted in a cypress dome receiving sec-
ondary wastewater grew faster than those in a control
dome, but mortality rates were higher; baldcypress
seedlings in the sewage dome grew more slowly and
had a higher mortality rate than those in the control,
possibly because baldcypress is not as well adapted to
low oxygen concentrations (Deghi, 1984).

Management of Cypress Swamps

It is clear that cypress swamps play a variety of roles
in meeting society's needs. Without any explicit manage-
ment, they provide habitat for wildlife and reduce flood
peaks and groundwater fluctuations. At the same time,
they can be used to treat wastewater and to provide a
variety of wood products. The fact that cypress swamps
still represent a large proportion of wetlands in the
southeastern United States suggests that early logging
activities were not entirely destructive and that cypress
swamps can recover from at least some degree of
logging.
Demands for all the services that swamps can
supply are increasing, and the greater facility of
modern logging vehicles for maneuvering in swamps
has increased the potential for damage to both remain-








ing trees and soil. Consequently, all the potential uses
of a cypress swamp must be carefully considered
when management strategies are formulated. The
recommendations we make are based on the informa-
tion that we have summarized above. Considerably
more research is necessary, however, into the full
scope of implications that arise from management
decisions.


Silviculture

The major consideration in logging is regeneration.
Although there is disagreement about the likelihood of
natural regeneration after timber harvest, it is clear that
a seed source must be left on or adjacent to a site, that
severe fires following harvest can prevent regeneration,
and that profound changes in hydroperiod, water
levels, soil aeration, and understory vegetation can
hinder seed germination and seedling survival. Given
the precise sequence of water levels needed for seed
soaking, seed germination, and seedling establishment,
it is unlikely that regeneration from seeds deposited
before harvesting will occur immediately after harvest.
Regeneration via coppice appears dependable, but it
is not well understood. If sprouting is desired, trees
should be cut so that the tops of the stumps are above
the mean high water level, although sprouting appears
to decrease if stumps are too high. Optimum tree age
and season of cutting, vulnerability of trees grown from
coppice to windthrow and disease (particularly pecki-
ness), and the quality of timber produced by sprouts
must be ascertained before dependence on coppice for
cypress regeneration can be recommended for sus-
tained-yield timber production. One advantage of
successful reproduction by coppice may be early
production of seeds from the sprouts.
Although an economic analysis of the profitability of
planting cypress is beyond the scope of this paper, it
seems safe to say that hastening (or ensuring) the
establishment of a new cypress stand by planting
might be advisable to derive the best returns from
forest land. Seedlings should be tall enough to escape
inundation after outplanting; 1-year-old seedlings may
be adequate for smaller, shallower swamps. Cattle
should be excluded from regenerating areas. Where
nutria and rabbits are abundant, planting is risky, and
trapping and/or application of repellents may be
necessary.
Clearcutting is attractive because it requires less labor
(selection of seed trees is not required) and only one
cut is necessary during each rotation (no second cut is
needed to remove seed trees). If an isolated swamp,
such as a cypress dome, is to be harvested, then seed
trees must be left or coppice production must be


dependable. If a larger swamp is to be cut, a viable
alternative might be to harvest in small blocks to
ensure good seed distribution from trees on the edges
of the clearcuts.
The traditional seed-tree system, in which seed trees
are left scattered throughout a large cutover area, risks
damage to seed trees during the initial harvest and to
the new stand when the seed trees are harvested. The
latter risk can be eliminated if seed trees are not
removed, making this technique a practical alternative.
In mixed swamps where cypress regeneration is
desired, cypress should not be selectively cut, because
cypress seedlings and saplings are likely to be outcom-
peted by more shade-tolerant hardwoods. Cypress and
many desirable shade-intolerant hardwoods are more
likely to regenerate in such forests if small blocks are
clearcut.
With a system of clearcutting small blocks (Fig. 10),
the distinction between clearcutting and seed-tree
cutting becomes blurred. Such a system will preserve a
source of seed and maximize the amount of light
reaching the floor of the swamp. Controlling the growth
of understory vegetation may still be necessary to
ensure cypress regeneration.
The question of thinning is difficult to address,
because there has not been sufficient research to
demonstrate its effectiveness. Thinning baldcypress
stands increases the growth of remaining trees, but not
significantly. Economic feasibility and potential for
damaging the remaining trees during thinning opera-
tions are the major considerations in deciding whether
thinning is advantageous.
In large stands of high-quality timber where it is
economically fzai Eblc, the May Brothers' system of


.- .. ...


Fg. 10. A north Florida swamp being cut gradually by
harvesting only 16 hectares (40 acres) at a
time.








building levees and flooding the areas to be harvested
could be modified to enhance regeneration. Seed trees
should be left uncut and standing water maintained
inside the levees during the winter after harvest to
allow seeds to soak. In spring, the water level could be
drawn down to the surface to allow germination.
Although the use of large machinery appears
attractive, especially for harvesting large swamps, the
long-term costs of impairment of regeneration and
reduced site quality can be significant (Fig. 11). Degree
of soil compaction and its effect on regeneration are
important issues. Harvesting timber in small blocks
and cutting with chain saws instead of feller-bunchers
may prove less costly in the long run.


Burning

Although Wade et al. (1980) suggested that no
special fire schedule is needed in south Florida cypress
domes, many Florida swamps exist in areas no longer
subject to natural fire regimes. There is little specific
information available to recommend a pattern of
prescribed burning for cypress swamps, although
some general guidelines can be proposed.
Pondcypress is adapted to more frequent fires than
baldcypress, and ponds probably bum more frequently
than strands. If pondcypress swamps are not burned
frequently enough, understory vegetation may prevent
enough light from penetrating to allow cypress regener-
ation, and succession to a bayhead or mixed hardwood
swamp may ensue. However, if cypress swamps are
burned too often, the growth of mature trees may be
retarded, and seed sources and young trees will be
destroyed. Allowing a fire to burn through a swamp


when the moisture content of its organic soil falls
below 65% can generate a peat fire that can destroy
not only seeds and saplings but also the roots of
mature trees. Heartrot may result if organic matter
burns deep beneath a tree's roots.
It is risky to use fire following a cypress harvest to
reduce slash and to control competing vegetation. Too
much fuel will cause an excessively hot fire, which
could destroy seeds, saplings, and seed trees; very hot
fires also eliminate the ability of stumps to sprout. If
the fuel load is light and the soil is wet, a carefully
controlled surface burn could be used.

Multiple-Use Management

The use of cypress swamps for additional treatment
of secondarily treated wastewater does not appear to
conflict with wood production. The increased growth
rates of trees in pondcypress stands receiving wastewa-
ter indicate that the two uses are compatible. Although
reproduction by seed is difficult because of continually
high water levels, planted seedlings can survive in such
swamps.
To date, only small swamps have been recom-
mended for use in wastewater treatment. Using
cypress domes for disposal would alleviate some of
the problems of groundwater pollution from septic
tanks in rural areas, and using small strands may be an
economical alternative to construction of expensive
tertiary treatment plants in small towns. However, the
effects of wastewater on wood quality and the effects
of soil compaction caused by harvesting on the water
treatment function are unknown.
Harvest scheduling should be based on the distribu-
tion of cypress swamps in the landscape, not just on
the amount of standing timber. Rather than cutting all
the cypress in one place in a given year, harvests can
be done in small, widely scattered patches in order to
maintain an even distribution of mature forest cover
and wildlife habitat. Although transporting equipment
and logs to carry out such a cutting design is more
costly, planning timber harvests on a landscape basis
can preserve the important ecological roles of cypress
swamps for flood mitigation, wildlife habitat, and water
conservation.


Fig. 11. Skidder trail left after logging in a central
Florida swamp.









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