Fire disturbance in the everglades ecosystem



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FIRE DISTURBANCE IN THE EVERGLADES ECOSYSTEM


Disturbance

  • Disturbance: Any relatively discrete event in space and time that disrupts ecosystem, community, or population structure and changes resources, substrate, or the physical environment. Disturbances typically cause a significant change in the system.

  • Landscape processes transfer energy and matter across a landscape.

  • Ming Xu, Lecture notes



Disturbance Regime

  • A summary description of a repeating disturbance type for a given landscape, for a given period of time

  • Described using empirical data and statistical summaries

  • Described by spatial, temporal and magnitude measurements



Disturbance and Landscape Interactions

  • Landscape pattern may affect the spread of disturbances

  • Existing landscape pattern may inhibit or facilitate the spread of a disturbance











Big Cypress National Preserve

  • Located in southwestern Florida, north and west of Everglades National Park.

  • Wetland communities, especially those dominated by bald cypress (Taxodium distichum), make up much of the preserve’s landscape

  • Topographic relief in the preserve is minimal, with a gradual slope (about 1 foot per mile) toward the coast, most of the preserve is under at least few inches of water during the summer rainy season

  • The flat nature of the land supports large areas of shortgrass prairies and sawgrass marshes

  • Graminoid communities naturally burn every few years

  • Fire is a common and significant ecological factor





FACTS

  • In terms of the amount of burning accomplished, the Big Cypress prescribed fire management program is the largest in the National Park Service (NPS)

  • Approx. 40,000 acres burned annually to reduce accumulated fuels in plant communities



IMPORTANT ENDANGERED WILDLIFE CONSIDERATIONS

  • Florida panther (Felis concolor coryi) habitat and prey

  • Red-cockaded woodpecker (Picoides borealis) nesting colony sites

  • Cape Sable seaside sparrow (Ammodramus maritimus mirabilis) nest site availability

  • Florida tree snail (Liguus fasciatus) hardwood hammock habitats



Florida tree snail (Liguus fasciatus)



Why is fire important in the Everglades Ecosystem?

  • Fire is an essential component of South Florida wetlands and pineland uplands and has been an important ecological process in shaping Everglades vegetation patterns

    • can determine inland expansion of mangroves
    • tree-island growth
    • plays an important role in preventing cypress trees from extending into marshes
  • 70% of plants endemic to southern Florida occur in pyroclimactic (fire climax) communities, Wade et al. (1980)



FIRE DISTURBANCE BENEFITS

  • Exotic plant removal

    • Melaleuca (Melaleuca quinquenervia)
  • Stand health and maintenance

  • Reduction of Hazardous Fuels

  • New growth provides food for wildlife (i.e. deer)

  • Controls pest problems



FIRE DISTURBANCE BENEFITS

  • “Moderate fires influence nutrient cycling, stimulate net primary production, and may even be the evolutionary process that selects for sawgrass and slough environments” (Wade et al. 1980).



WITHOUT FIRE…

  • Cypress domes can be replaced by mixed hardwoods

  • Flammable leaf litter builds up, increasing the fuel loads = higher risk for more severe fires

  • “Lack of fire has allowed succession to proceed in many areas, so that herbaceous communities are being invaded by dense shrub thickets and pine on more upland sites, and cypress forests are being invaded by shrubs and hardwoods” (Hofstetter 1984).



ALTERED FIRE REGIMES

  • Altered timing, frequency, and intensity of fires

  • Drainage of Everglades attributed to change in regime

  • Can result in peat or muck fires, which may burn over extensive time period

  • Disrupt entire everglades ecosystem health



Exotic Species Effects on Natural Fire Regimes

  • Old World climbing fern (Lygodium microphyllum (Cav.) R. Br.) promotes the spread of wildfires, due to kiting of burning mats into adjacent habitats that would otherwise be protected by fire breaks, and due to its tendency to act as a flame ladder carrying fire high into native tree canopies (Roberts 1996).



FIRE SEASON

  • Late spring is likely season for fires

  • Ecological observations:

    • (1) late spring is usually the driest season
    • (2) dry conditions occur through much of this season
    • (3) afternoon lightning becomes common






Prescribed Burns and Fire Season

  • Therefore, prescribed burn plans should take into account the natural fire regimes that occurs in the preserve.

  • Avoid burning in communities at times when fires would not naturally occur

  • Doing so might alter the ecological effects of the natural fire regime



Fire Disturbance Simulation Models

  • Useful for land managers to model fire regimes to estimate the ecological effects of fire disturbance



Hierarchical Fire Frequency Model Yang et al.

  • Hierarchical fire frequency model

  • Accounts for the separation of fire ignition from fire occurrence

  • Complicated non-stationary temporal patterns of fire can be simulated

  • Implemented as an improved fire module in LANDIS



Hierarchical Fire Frequency Model Yang et al.

  • Can simulate a wide range of fire regimes across heterogeneous landscapes with a few parameters and a moderate amount of input data

  • The model possesses great flexibility for simulating temporal variations in fire frequency for various forest ecosystems and can serve as a theoretical framework for future statistical modeling of fire regimes





Swamp Buggy Fire Truck





Prescribed Burn



Hot palmetto fire



Forest fire in the Everglades



Forest fire in the Everglades









CONCLUSIONS

  • A disturbance is any relatively discrete event in space and time that disrupts ecosystem, community, or population structure and changes resources, substrate, or the physical environment. Typically cause a significant change in the system.

  • The ecology of biological communities should be considered in planning fires



CONCLUSIONS

  • Recovery of natural fire regimes is critical for the overall Everglades restoration effort

  • Fire disturbance simulation models can be used as a valuable management tool to predict ecological fire disturbance effects.



SOURCES



SOURCES

  • Xu, Ming. 2006. Lecture Notes. Rutgers University.

  • Wade, D., J. Ewel, and R. Hofstetter. 1980. Fire in South Florida Ecosystems. General Technical Report SE-17. Asheville, N.C.: U.S. Department of Agriculture–Forest Service, Southeast Forest Experiment Station.

  • Duever, Michael J. “Big Cypress Regional Ecosystem Conceptual Ecological Model”

  • Robertson 1955, White 1970, Cohen 1974, Duever et al. 1976, Wade et al. 1980, Wu et al. 1996.

  • Davis 1943, Egler 1952

  • Long, Alan J. 1999. Benefits of Prescribed BurningUniversity of Florida.

  • Jian Yang, Hong S. He and Eric J. Gustafson. 2003. “A hierarchical fire frequency model to simulate temporal patterns of fire regimes in LANDIS”




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