Fire Ecology

Big Cypress has five main vegetation types that we consider when it comes to fire management:

Pine Forest
Pine forests inhabit the upland portions of the Preserve and reside on sandy soil with exposed bedrock. The pinelands are considered a sub-climax plant community maintained by fire that will succeed to a mixed hardwood forest in the absence of fire. Slash pine, saw palmetto, cabbage palm and wax myrtle are the dominant fire-adapted species found in pinelands.

Mixed Grass Prairie
The mixed grass prairies found within the Preserve are seasonally inundated with water between June and October. Muhlenbergia grass is the dominant herbaceous species and the primary carrier of fire.

Cypress Forest
Cypress forests within the Preserve can be divided into three categories; cypress domes, cypress strands and cypress prairies. Pond and bald cypress trees typically dominate strands and domes and dwarf cypress trees occupy wet prairies, although all species of cypress can be found in each of the formations. Generally all three communities are barriers to fire spread in normal climatic conditions. In drought years, water can become completely absent from cypress communities, allowing fire to move through the understory, often igniting ground fire. It is recognized that cypress trees and communities are fire dependent. Cypress trees have been found to have one of the most fire-resistant barks, as measured by its insulating properties. It is thought that without occasional drought years and fire, cypress domes and strands can become increasingly dominated by hardwood species.

Mixed Hardwood Hammocks
Hardwood hammocks are considered to be a climax community. Hardwood hammocks usually develop on elevated locations in the absence of fire. Although fire may carry through the surface litter layer, generally the root systems of hammock vegetation penetrate the sandy soils and bedrock and are protected from average fire behavior in normal climate conditions. Dominant species found in the hammocks within the Preserve include live oak, water oak, laurel oak and wild tamarind.

Marsh
Marsh vegetation is extremely varied, but a given site is usually dominated by one or two species. Among the most common are pickerel weed, arrowhead, sawgrass, fire flag, cattail, and bulrush. Marshes are maintained as sub-climax associations by fire, and ponds are often created by peat fires. In the absence of fire, shrubs rapidly invade and within 5-10 years, may form a complete canopy. Marshes are considered a sub-climax plant community maintained by fire that will succeed to a mixed hardwood forest without fire.

 

Vegetation Group	Acreage	Total Percentage of Big Cypress Acreage
Cypress Strand/Dome	218,435	30%
Cypress Prairie	141,293	20%
Pineland	95,924	14%
Prairie	66,565	9%
Sawgrass	96,914	14%
Tall Sawgrass	5,234	1%
Hammock	25,858	4%
Swamp Forest	22,690	3%
Marsh	19,746	3%
Disturbed	6,458	1%
Mangrove	2,997	0.4%
Water	2,598	0.4%

 

 

FUEL CHARACTERISTICS

One-hour fuels (grasses and other fine fuels) are a major component of the fire environment in south Florida. Palmetto and wax myrtle are shrub species that also contribute to the fire behavior. The volatile makeup of these species allows them to burn year round, with varying degrees of intensity. These fuels can burn readily with an relative humidity of 57 percent and wind speed of 7 mph. The least extreme fire behavior is experienced in the late summer months when there is hydrologic sheet flow throughout the Preserve. During this time there is standing water in most of the vegetation types.

Wet season (July – October)
Standing water is present in all three types of cypress forest and sheet flow conditions are present in the prairies. Some pinelands may become inundated for short durations. During these time periods fire spread is generally confined to dry pinelands. Under higher wind conditions (> 15 mph) fire may move through the top portions of prairie grasses or palmetto patches across standing water; however, the extent of wet cypress and hardwood hammock fuel breaks generally prevents large fire growth and unchecked rates of spread.

Dry season (March – May)
Water may be absent from all vegetation types, and all fuels are available to burn including organic matter. Fire behavior in cypress formations is characterized by a fuel model 8 (GR2 and TL4), pinelands a fuel model 7 (SH6), and prairies a fuel model 3 (GR5 and GR8). Marshes and the deepest interiors of cypress domes and strands may continue to hold water and act as barriers to fire spread.

Season transition (November – February & June)
Historically, water levels begin to rise in the cypress formations and prairies when the summer rains begin in June and subside during the fall and winter months as the rainy season tapers off in October. Fire spreads from pine stand to pine stand and across the driest portions of the mixed-grass prairies. Cypress domes, strands and cypress prairies are effective barriers to fire spread at this time.

FIRE SEASON

Human caused fire season typically coincides with dry season and increased recreational activity. Lightning fire season can range from April through August. In the early years of the Preserve, wildfires were human caused during the winter. Presently, human caused fires are during the driest months of March – June.