Document: KEN-3-68-4

Influence of severe wildfires on density and composition of tree layer on flatwoods sites of southeastern coastal plain, USA.

OUTCALT, K.W.*

USDA Forest Service, Southern Research Station ¹

Abstract:
Severe fires burn flatwoods sites of the coastal plain of the southeastern United States during periodic droughts. The purpose of this study was to measure the effect of one of these catastrophic fires to determine their importance in shaping the density and composition of the tree layer. The study was conducted on the Osceola National Forest in northeast Florida on a 10,000 ha wildfire area that burned during extreme conditions in June 1998. Prior to the wildfire there were 264, 317, and 344 slash (Pinus elliottii) and longleaf (P. palustris) pine trees per ha on dry, moist, and wet sites, respectively. Mortality from the fire increased with relative moisture level exceeding 70 percent on the wettest habitats. The wildfire killed most slash seedlings while most longleaf seedlings recovered. There were no differences in species mortality rates for larger trees except on the wet sites where longleaf had higher losses than slash. On the dry sites there was a disproportionate loss of slash pines from the sapling size class. This catastrophic fire significantly reduced the density of the tree layer, especially on the wetter areas. Thus, these less frequent but more severe fires seem to drive the system toward a more open savanna type habitat particularly on the wetter sites. They also seem to influence composition by selecting for slash pine on the wettest sites and longleaf on the drier ones.

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This abstract is being presented at: 10:30 AM in session:
Poster Session #12: Disturbance Ecology.