Using Size-Frequency Distributions to Analyze Fire Regimes in Florida
Wildfire regimes in natural forest ecosystems have been characterized with powerlaw distributions. In this paper, we evaluated whether wildfire regimes in a human-dominated landscape were also consistent with powerlaw distributions. Our case study focused on wildfires in Florida, a state with rapid population growth and consequent rapid alteration of forest ecosystems and natural fire regimes. We found that all fire size-frequency distributions evaluated in this study were consistent with powerlaw distributions, but the powerlaw distributions were piece-wise linear. A kink in the powerlaw distributions occurred at about 640 ha for flatwoods fires and at about 290 ha for swamp fires. Above these levels, fires "exploded" into a catastrophic regime. If the kink represents the level at which fires become immune to fire suppression effort, we would expect that the location of the kink would occur at smaller fire sizes during extreme fire years due to the increased flammability of fuels and the relative scarcity of fire suppression resources. We found this result for three of four extreme fire years in flat-woods ecosystems and for all four extreme fire years in swamps. These results suggest that catastrophic fires may not be possible to prevent and that suppression efforts during extreme fire years may be best applied to strategic areas that decrease the connectivity of fuels.