PARENT SESSION
Oral Session # 6: Fire Ecology I: Structure and Demographics
Presiding: R Parmenter
Monday, August 4. 8:00 AM to 11:30 AM, SITCC Meeting Room 105.

Landscape fire ecology: Defining fire compartments and a topographic index of fire probability.

Langley, Susan¹, Frost, Cecil², Fels, John³, Wentworth, Thomas³, ¹ Georgia Southern University, Statesboro, GA² North Carolina Plant Conservation Program, Raleigh, NC³ North Carolina State University, Raleigh, NC

ABSTRACT- Fire compartments are a central concept of landscape-level fire ecology. A fire compartment is a unit of the landscape having continuous fuel and no natural fire breaks, such that an ignition would be likely to burn the entire compartment barring changes in weather or fuel moisture. We hypothesized that presettlement (potential/natural) distributions of fire-dependent longleaf pine (Pinus palustris) communities could be accurately mapped using a new environmental variable, presettlement fire compartment size. We quantify the average fire probability index (AFPI) for any point within a fire compartment using topographic features and compartment size. GIS layers with watershed information were used with slope-class maps derived from DEMs to map fire compartments in the Uwharrie National Forest, North Carolina. The AFPI for points in this landscape was predicted using a GIS and an algorithm that included distances to firebreaks and prevailing wind direction during fire season. AFPI values were assigned to one of five topographic fire regime (TFR) classes, from class 1 (the most fire protected areas) to class 5 (the most fire exposed areas). TFR classes were comparatively assessed using 209 'witness trees', mapped in a GIS layer from county survey plats of the study area ca. 1700-1800. Trees were assigned to vegetation fire regime (VFR) classes based on species characteristics. The most fire refugial species were assigned to VFR class 1 and the most fire-dependent species were assigned to class 5. Correspondence between VFR and TFR classes was 86%. Our hypothesis that presettlement fire-dependent communities could be accurately mapped using fire compartment size was generally supported by our results. Our weighting scheme also appears to be realistic for this landscape. The AFPI for a particular site may be the most ecologically meaningful environmental variable for understanding and managing remnant natural areas to maintain original levels of biodiversity in fire-dependent landscapes.

Key words: Fire ecology, Average fire probability index (AFPI), Longleaf pine (Pinus palustris), Fire compartments