Effects of Differences in Prescribed Fire Regimes on Patchiness and Intensity of Fires in Subtropical Savannas of Everglades National Park, Florida

Abstract

We investigated effects of fire frequency, seasonal timing, and plant community on patchiness and intensity of prescribed fires in subtropical savannas in the Long Pine Key region of Everglades National Park, Florida (U.S.A.). We measured patchiness and intensity in different plant communities along elevation gradients in “fire blocks.” These blocks were prescribed burned at varying times during the lightning season and at different frequencies between 1995 and 2000. Fire frequency, seasonal timing, and plant community all influenced the patchiness and intensity of prescribed fires. Fires were less patchy and more intense, probably because of drier conditions and pyrogenic fuels, in higher elevation plant communities (e.g., high pine savannas) than in lower elevation communities (e.g., long‐hydroperiod prairies). In all plant communities fires became increasingly patchy and less intense as the wet season progressed and moisture accumulated in fuels. Frequent prescribed fire resulted in increased patchiness but a wider range of intensities; higher intensities appeared to result from regrowth of more flammable vegetation. Our study suggests that frequent early lightning season prescribed fires produce a wider range of post‐fire conditions than less frequent late lightning season prescribed fires. Our study also suggests that natural early lightning season fires readily carried through pine savannas and short‐hydroperiod prairies, but lower elevation long‐hydroperiod prairies functioned as firebreaks. Natural fires probably crossed these firebreaks only during drier years, potentially producing large landscape‐level fires. Knowledge of how patchily and intensely fires burn across a savanna landscape should be useful for developing landscape‐level fire management.

Ecological Implications of Fine-Scale Fire Patchiness and Severity in Tropical Savannas of Northern Australia

“…Allan 2001, Slocum et al 2003, Russell-Smith and Edwards 2006. Grasses, the dominant component of the combustible fuel in these savannas, progressively cure and collapse with the onset of the dry season.…”

“…Various studies have been undertaken to better understand fire patchiness, for a variety of ecological and associated land management purposes, in the USA (Turner et al 1994, Slocum et al 2003, southern Africa (Hudak et al 2004) , Spain (Román-Cuesta et al 2009 and Australia (Russell-Smith et al 1997, Allan 2001, Russell-Smith et al 2002b, RussellSmith and Edwards 2006. Russell-Smith and Edwards (2006) reported that EDS fires have 80% probability of being of low severity and would therefore be expected to have greater internal patchiness than LDS fires.…”

Changes in Modern Pollen Assemblages and Soil Geochemistry along Coastal Environmental Gradients in the Everglades of South Florida

“…Wet prairies typically have hydroperiods of less than 12 months and are thus dry seasonally, tending to burn more than once a decade, and even every 1-2 years if adjacent to pine savannas (Platt, 1999;Schmitz et al, 2002;Slocum et al, 2003).…”

“…Vegetation at these four sampling locations is typical of wet prairies consisting of mainly sawgrass marsh (C. jamaicense) and willow thickets (Salix), with Sagittaria and Typha in more open areas (Slocum et al, 2003). Vegetation at RRP (#3) is dominated by bald cypress (Taxodium distichum), with other bottomland hardwood species (e.g., Acer, Fraxinus, Annona) forming the subcanopy, and Utricularia, Eleocharis, ferns, and Asteraceae present in the understory.…”

The Effects of Fire on Spore Viability of Lygodium microphyllum (Old World Climbing Fern)

“…For example, in pine savannahs, fallen needles make up the fine fuels which, when suspended on grass tussocks, burn well (500-800°C) because of their resins and ventilation (Slocum et al 2003). Temperature measurements taken at the ground surface in longleaf pine forest by Glitzenstein et al (1995) ranged from 274 to 452°C.…”