Fire Ecology and Management of Cypress Ponds

Cypress Swamp

Non-alluvial wetlands dominated by pond cypress (Taxodium distichum var. nutans) including Cypress ponds, cypress strands, cypress domes, sinkhole ponds, cypress-gum ponds and cypress savannahs are a common feature of the southeastern coastal plain. These wetlands tend to be isolated, situated within a matrix of fire-adapted communities. Rain, runoff and shallow groundwater are the dominant sources of water in most of these pond cypress wetlands. Water levels fluctuate widely, and hydroperiods are long ranging from 6 to 12 months per year. The soils of these communities range from organic and peat accumulations to mineral soils.

The vegetation of these cypress-dominated wetlands differs in composition and structure. The canopy can be almost purely pond cypress in cypress savannahs to mixtures of cypress, pine and hardwoods in other cypress wetlands. Shrubs may dominate midstories or shrubs may be absent. Herbs can be common, where shrubs are absent and where standing water is not too deep. Wetland margins are habitat for many rare plants.

Animals that use pond cypress wetlands include a diverse assemblage of invertebrates. Fish populations are not well developed in cypress wetlands that are ephemeral. However, amphibians and reptiles take advantage of the ephemeral nature of the wetlands and are common and important components of cypress wetland fauna. Several listed species of amphibians use cypress wetlands for breeding. Bird fauna is dominated by passerines. Mammal species found in these cypress systems tends to be similar to those that use the surrounding communities.

The fire regime of isolated wetlands is influenced by the surrounding fire adapted communities. Historically, the margins of these isolated wetlands may have experienced a higher fire frequently than the centers of wetlands as fires spread from upland into wetlands. Wetland margins may have burned as often as every 3 years and entire wetlands may have gone as long as 10 to 100 years depending on the frequency of drought and draw down. Natural fires are thought to have occurred in early lightning season and coincided with a time of common drawdown of wetlands. Human alterations of the natural fire regime include decreases in frequency of burns in wetlands and shifts from the natural lightning season to dormant season burns. Further, wetlands have often been “protected” from fire by plowed fire lines.

Fire helps shape the vegetation of pond cypress communities. Pond cypress is resistant to fires and will survive fires that hardwoods do not. Pond cypress is known to sprout following injury from fires. However, severe ground fires will cause mortality of pond cypress. Fire and hydrology are instrumental in limiting hardwood invasion of pond cypress wetlands. Little research has been conducted on fire effects on shrubs in cypress wetlands; however, shrub response is likely similar to shrubs of other wetland and pine systems with frequent fires helping to limit shrub invasion. Frequent fires are important in maintaining herbaceous ecotones and herbs in some wetlands.

Animal species are influenced by fire through the effects on plants. Infrequent fires resulting in canopy closure decrease use by wading birds, amphibians and reptiles. Grassy ecotones are particularly important for reproduction of several listed amphibian species including the flatwoods salamander, striped newt and gopher frog.

Prescribed fire programs have often excluded fire from pond cypress wetlands through the use of plowed firebreaks and by burning under wet conditions. Smoke management and fire control may be an issue when burning cypress wetlands with organic soils. Allowing fires to burn into and through wetlands is ecologically desirable because of the effects of fire on vegetation and the effect of vegetation on animal habitat, including listed species habitat. However, the conditions under which vegetation within cypress stands will burn and any organic soil will not, are precise. Prescriptions that include such goals may create narrow burn windows.