STABILITY AND INSTABILITY IN PLANT-COMMUNITIES FOLLOWING FIRE

Tree species composition and density were monitored in closed oak-hickory forest and forest-prairie edge for a period of five years after a prescribed burn. In the closed forest, tree stem density declined markedly following the burn. Tree basal area and density decreased from 17.5 m2/ha and 630 trees/ha in the preburn sample to 12.0 m2/ha and 310 trees/ha five years later. In contrast, on the forest-prairie edge, tree basal area and density increased slightly during the same time period from 3.0 m2/ha and 117 trees/ha to 5.2 m2/ha and 172 trees/ha. Our data suggest that closed canopy forests in fire susceptible areas accumulate fuels to levels that encourage fires of sufficient intensity to destabilize forest systems and convert them to open forests or savannahs. Conversely, on the forest-prairie edge, amounts and patterns of fuel accumulation, and species response to burning, are such that fire can be considered to be a factor promoting stability.