Interactions of large-scale disturbances: Prior fire regimes and hurricane mortality of savanna pines
Abstract
Differences in initial large-scale disturbances might change effects of subsequent large-scale disturbances. We explored possible effects of prior fire regimes on subsequent hurricane-related mortality of south Florida slash pine (Pinus elliottii var. densa) in remnant Everglades pine savannas that were unburned, burned during the wet (lightning fire) season, or burned during the dry (anthropogenic fire) season in the decade before Hurricane Andrew (1992). We measured direct mortality during Andrew (snapped trees) and extended mortality over the subsequent 24-30 mo (mainly insect attacks on damaged trees). We used Bayesian model averaging to obtain probabilities of different models of survival based on fire regime and site characteristics (remnant area, distance to the Atlantic Ocean, depth to water table in the dry season, sustained wind speeds, tree sizes). Most likely models for direct and extended mortality included large negative effects of tree size and dry-season fire regime, and positive effects of stand area (direct mortality) and wet-season fire regime (extended mortality). Depth to water table and distanceto the ocean had less certain effects. Our results, not predicted from fires or hurricanes alone, suggest that anthropogenic changes to dry-season fires strongly influence the effects of subsequent hurricanes on the mortality of pines in subtropical savannas.