Prescribed Fire in the Everglades

Prescribed fire in the Everglades has been used for fire hazard reduction in sawgrass (i.e., fuel management) to help control dry season fires, to protect resources like hammocks, to clear vistas, to maintain plant communities, to manage habitat for game and endangered animals, and as a tool to control exotic plants (Taylor 1981, Wade et al 1980).

Historically, prescribed fire in the Everglades has been applied through both wet and dry seasons with the largest area burned in the dry season (Gunderson and Snyder 1994). Different portions of the Everglades are managed by different agencies that have different management goals; thus patterns of prescribed fire differ from place to place. Regardless, prescribed fire accounts for less than half the acreage burned by lightning fires and 6 times more area is burned human caused non-prescription fires than by prescribed fires (Gunderson and Snyder 1994).

A number of issues emerge in using prescribed fire in the Everglades:

• Much of the area that burns in the Everglades is situated on organic soils. Though ground fires are a natural part of the ecology of the Everglades they can be difficult from a management perspective (See Organic Soils).
  • In order to avoid igniting a ground fire, minimum soil moisture content of 65% for the highest elevation soils on the burn site has been specifically recommended for Everglades soils (Wade et al. 1980).
  • Work by Hungerford et al. (1996) suggests that higher soil moistures might be required to minimize the probability of igniting ground fires.
  • Ground fires in tree islands can be an operational problem as they can be sources of re-ignition of marsh vegetation as peat on tree islands smolder.
• Ground fires are an important ecological process in the Everglades that operate to maintain the spatial and temporal mosaic of plant communities. Prescribed fire programs designed to eliminate all ground fires may have resulted in a decrease in wetter, deeper water plant communities in favor of sawgrass marsh and have thus operated to reduce environmental heterogeneity and diversity (Davis et al. 1994). Some of these same programs were designed to protect environmental heterogeneity through fuel management to slow the rate of burnout of tree islands. Achieving an ecological balance presents a challenge to prescribed fire managers particularly when managing areas with an altered hydrologic regime.

• Unfortunately, when operating in south Florida, fire managers must consider the effects of exotic vegetation on fires and conversely the effect of fires on exotic vegetation.
  • How will exotic fuels affect fire behavior (ladder fuels, spotting, rate of spread or lack of)?
  • Will fires operate to control exotic vegetation or aid it’s establishment or spread? (See fire and exotic vegetation)
• Give consideration to altered effects of fire when hydrologic conditions depart from the natural regime, or after extreme events.
  • Periods of prolonged flooding with little water level fluctuation can result in an elevation of the meristem in sawgrass plants forming tussocks. These plants are more susceptible to damage from fire because meristems are not as well protected by soil (Wade et al. 1980). Burns may need to be conducted under higher water levels to avoid damage to sawgrass stands.
  • Dead biomass accumulation may be higher where natural flows have been disrupted thus altering decomposition rates and altering flushing rates.
• Fire managers must be aware of conditions that result in increased fuel availability that can alter fire behavior such as:
  • Frost-killed vegetation.
  • Dead exotic vegetation resulting from treatment programs.
  • Lowered water levels.

The implementation of fire in south Florida is discussed by Wade et al. (1980) including prescription parameters, ignition techniques, and equipment needs. The following are ecological considerations when implementing a burn program in the everglades.

• Burning in the natural fire season, the transition from the dry to wet season, has been recommended by several authors (Wade et al. 1980, Hofstetter 1973 in Taylor 1981).
• Burning in the spring is contingent on adequate moisture and high enough water levels.
• Water level fluctuation should be considered when burning sawgrass to ensure it’s survival – too rapid and great a rise can cause mortality.
• If water levels are too high sawgrass may re-burn when water recedes.

• Recommended frequencies for burning various plant communities are not well understood. Various recommendations have been made for sawgrass based on various goals:
  • The belief that sawgrass declines observed in the 1970’s was due to insufficient fire resulted in recommendations for burning to maintain sawgrass vigor. Sawgrass condition subsequently improved in the early 1980’s in both burned and unburned stands (Taylor 1981). Suggested frequencies for burning to maintain sawgrass vigor range from 8-10 year cycles to 2-5 year cycles (references within Taylor 1981).
  • Burning glades on a 10 year interval has been recommended to control hardwood invasion (Hofstetter 1973 in Taylor 1981). Others have suggested that a more frequent burn interval is needed to control Salix caroliniana, perhaps as frequent as a 3 – 4 year interval (Duever 1976 cited in Duever 1984, Lee et al., In press, Lee et al., in prep).
  • Burning sawgrass on a 3-5 year interval to maintain a 2 to 1 ratio of dead to live fuel (references within Wade et al. 1980).