Distribution and Composition of Cypress Ponds

Cypress ponds and related communities, cypress strands, cypress domes, sinkhole ponds, cypress-gum ponds and cypress savannahs, are all non-alluvial wetlands, dominated by pond cypress (Taxodium distichum var. nutans). These wetlands are a common feature of the southeastern costal plain occurring in Florida, Georgia, South Carolina, North Carolina, Alabama, Mississippi, into southeastern Louisiana and as far north as southeastern Virginia (Ewel 1995). These wetlands range widely in size from less than 1 ha (0.25 acres) to greater than 10 ha (25 acres) (Ewel 1998, Schalles et al. 1989), but within the landscape, small wetlands are much more common than are large wetlands (Schalles et al. 1989, Semlitsch and Bodie 1998). These wetlands are situated in basins or depressions and generally have no connection to aboveground streams or river systems (Russell et al. 2002). Fire plays an important role in shaping these communities (see Fire Regime).

Rainfall patterns and thus hydrology differ among these wetlands within their range. In south Florida, there tends to be distinct wet and dry seasons (Wade et al. 1980). In northern Florida and southern Georgia there tends to be two wet seasons, one in winter, associated with passing cold fronts and another in summer due to convective storms (Chen and Gerber 1990). Farther north and west in the costal plain, rainfall tends to be more evenly distributed throughout the year (Kirkman et al. 2000).

Rain, runoff and shallow groundwater are the dominant sources of water in pond cypress wetlands, with the exception of sinkhole ponds, which are sometimes connected to deeper aquifers (Ewel 1990, 1998). All of these wetlands are subject to widely fluctuating water levels, which are often unpredictable. Water fluctuation is important in these wetlands as cypress requires dry ground for germination (Demaree 1932) and under non-flooded conditions hardwoods out-compete cypress (Marios and Ewel 1983). Hydroperiod in these wetlands ranges from 6 – 9 months per year for cypress domes and savannahs (Marios and Ewel 1983, FNAI 1990, Sutter and Kral 1994) to 6-12 months for pond cypress ponds and cypress gum ponds (Sutter and Kral 1994). Basin depth (water plus accumulated peat) is typically shallow, < 1.5m (Casey 1997) and water is acidic (Brown 1981).

Cypress domes are thus named because of their domed appearance with tallest trees at the center and shortest vegetation at the edges. Of the pond cypress dominated communities, cypress domes and strands are most likely to contain peat deposits, though peat is not always present. Where peat or surface organic soil layers are present, they are deepest in the center of the wetland. Some domes contain non-forested areas of nearly permanent standing water in the deepest center portions of the dome. This community type is most common in Florida and southern Georgia. Cypress strands, also most common in Florida, particularly in south Florida, are shallow depressions in close proximity to one another that coalesce and contain flowing water in times of flood. Strands can be hard to distinguish from cypress domes under conditions of low water. The deepest portions of strands that often contain flowing water can have bald cypress present (Ewel 1990). Cypress ponds and cypress gum ponds are most common from the panhandle of Florida northward. They occur in shallow depressions but tend to be characterized by mineral soils or organic soils rather than peat and can occur in Carolina Bays, a type of depression of uncertain geologic origin, lime sinks or in other depressions. Cypress savannahs occur in broad basins with mineral soils underlain by clay (Schafale and Weakley 1990). A variant, dwarf cypress savanna occurs over very shallow, nutrient poor soils underlain by limestone in south Florida (Wade et al. 1980). Dwarf cypress also occurs in the Panhandle of Florida (Ewel 1998).

There tends to be a gradient of nutrient availability that is mirrored by productivity ranging from low productivity in dwarf cypress savannahs to intermediate in cypress domes to moderate in cypress strands (Brandt and Ewel 1989).

Vegetation:

Pond cypress dominated wetlands differ from bald cypress (Taxodium distichum) dominated communities, which occur along river drainages and lake margins not only in fire frequency, but also in hydrology, productivity, nutrient availability, and species richness. Bald cypress tends to occur where there is flowing water whereas pond cypress occurs in still water wetlands. Nutrient availability, productivity and species richness all tend to be higher in bald cypress swamps as opposed to pond cypress swamps (Ewel 1995). Fire frequencies are higher in pond cypress wetlands (see Fire regime)

Common vegetation in cypress domes and strands includes pond cypress, swamp tupelo (Nyssa sylvatica var. biflora), and slash pine (Pinus elliottii) in the canopy. Other canopy species can overlap with those of bay swamps. Midstory can be lacking, sparse or comprised of shrubs including fetterbush (Lyonia lucida), Virginia willow (Itea virginica), button bush (Cephalanthus occidentalis), titi (Cyrilla racemiflora), and dahoon holly (Ilex cassine). Common vines include laurel greenbrier (Smilax laurifolia) and poison ivy (Toxicodendron radicans). Where shrubs are absent or sparse, groundcover can include sphagnum and various sedges (Ewel 1990, FNAI 1990).

Farther north, cypress-gum pond canopy species include pond cypress, swamp tupelo. Shrub species are sparse except around pond margins and can include storax (Styrax americana) hurrah-bush (Leucothoe racemosa) sweet pepperbush (Clethra alnifolia) and fetterbush. Sedges and canopy species seedlings sparsely cover the ground layer (Kirkman et al. 2000).

Pond cypress is the dominant canopy species in more northerly cypress savannahs and is widely spaced over a grass and herb dominated understory. Other trees can occur in the canopy including swamp tupelo, persimmon (Diospyros virginiana) and red maple (Acer rubrum). The most common shrubs include myrtle leaf holly (Ilex myrtifolia) and buttonbush. The herbaceous groundcover is diverse and variable among sites and dominant species can change dramatically from year to year within a site (Sutter and Kral 1994, Schafale and Weakley 1990). Sutter and Kral (1994) suggest that these cypress savannahs are among the most floristically diverse systems in the southeastern costal plain.

In South Florida, dwarf cypress savannah is dominated by stunted pond cypress with grasses, sedges and forbs in the understory. Cover of the understory can be quite sparse to continuous depending on the qualities of soils and overstory density (Wade et al. 1980).

Animals

There is generally a high diversity of invertebrates in cypress wetlands in comparison to other systems (McMahan and Davis 1984). Among invertebrates, bottom-dwelling species involved in decomposition likely form the base of wetland food chains (Ewel 1998). The most common small invertebrate taxa represented in dome systems in Florida included flies; ants, wasps and bees; spiders and bugs (McMahan and Davis 1984). Crayfish are also common inhabitants of these systems (Ewel 1990, Hart and Newman 1995).

The ephemeral nature of most pond cypress wetlands tends to prohibit the development of an extensive fish fauna, although fish populations can be important in wetlands with permanent or semi-permanent water (Ewel 1990, Hart and Newman 1995). Presence/absence of fish is related to the period of flooding and the proximity of the wetland to permanent wetlands from which fish emigrate during floods (Snodgrass et al. 1996, Hart and Newman 1995).

A particularly important component of these small, isolated, temporary ponds are amphibians and reptiles (Semlitsch and Bodie 1998, Russell et al. 2002). The general lack of predatory fish creates an environment important for amphibian breeding and larval development. Reptiles utilize these wetlands for cover, foraging and hibernation (Russel et al. 2002). High diversity and densities of amphibians and reptiles using small isolated wetlands have been documented all over the Southeastern Costal plain. Russel et al. (2002) documented 26 species of amphibians and 36 species of reptiles utilizing wetlands. Similar numbers of reptile and amphibian species have been found in other isolated wetlands in the southeastern costal plain (Harris and Vickers 1984, reviewed in Semlitch and Bodie 1998, and Russel et al. 2002). Frogs and toads are particularly numerous (Harris and Vickers 1984). Various species of salamanders also utilize these wetlands including the federally threatened flatwoods salamander and the striped newt, a candidate for listing.

Bird life tends to be dominated by passerines, including many migrants, and cavity nesting birds. Common species include common yellow throat warbler, robins, woodpeckers, Carolina wrens and occasionally wood ducks (Workman 1996, Harris and Vickers 1984). These birds tend to forage for insects in evergreen vegetation and some take advantage of fruits produced by various shrubs and vines. Wading and water birds are not common in shrubby cypress systems, but are known from systems with open understories, and will utilize clear-cut systems (Harris and Vickers 1984, Workman 1996). Cypress wetlands in Florida are known to contain wading bird rookeries (Ewel 1998)

Use of pond cypress wetlands by mammals is not as frequent or intensive as in other nearby systems (Harris and Vickers 1984), and there are no mammals that are restricted to or endemic in these wetlands (Ewel 1998, Schalles et al. 1989). Small mammals that use these wetlands tend to utilize the periphery or ecotone of the wetland (Harris and Vickers 1984). Various species of mice and rats, shrews, otters, possums, raccoons, mink and white tailed deer utilize wetlands (Hart and Newman 1995). These wetlands may be important sources of food and cover for some species of mammals (Hart and Newman 1995).