FIRE TEMPERATURE HETEROGENEITY IN CONTRASTING FIRE PRONE HABITATS - KANSAS TALLGRASS PRAIRIE AND FLORIDA SANDHILL

Spatial patterns of fire temperatures from a tallgrass prairie and adjacent Gallery forest in northeast Kansas and a sandhill community in central Florida were recorded using temperature-sensitive pyrometers. The objectives of the study were to determine, in both habitats, the range of temperatures reached during prescribed burning under a range of different conditions. Both habitats are characterized by frequent, low-intensity fires confined to the herbaceous vegetation and low shrubs. In tallgrass prairie, fire temperature maxima ranged from 19 to 399-degrees-C (n = 243). The highest temperatures were associated with fires in isolated tree and shrub canopies (399-degrees-C). Fires were hotter in headfires compared with backfires (47-degrees-C difference), on lowlands compared with uplands (12-degrees-C difference), and in areas that had not been burned for many years compared with areas burned annually (34-degrees-C difference). In the Florida sandhill, fire temperature maxima ranged from 35 to 538-degrees-C (n = 240), with the highest temperatures recorded at ground level in sites which had not been burned for at least 5 years. Compared with frequently burned areas, areas that have not burned for many years build up high fuel loads that support a more homogeneous, hotter fire. In the tallgrass prairie, homogeneity of fire temperatures was greatest in areas of intermediate fire frequencies. The greater spatial heterogeneity in fire characteristics of prairie with very high fire frequency (annual fire) and very low frequency (> 15 years between fires) is likely a result of low fuel loads and more patchy vegetation structure, respectively. In sandhill, low fuel loads and patchy distribution of fuel contribute to high spatial variability in fire temperatures in annually burned sites.