Petersen, S.M. and P.B. Drewa (Case Western Reserve University, Cleveland, OH 44106). Did lightning-initiated growing season fires characterize oak-dominated ecosystems of southern Ohio? J. Torrey Bot. Soc. 133(2): 217–224. 2006.—The persistence of oak-dominated ecosystems throughout the Central Hardwoods Region has been attributed to chronic, non-catastrophic fire regimes prior to Euro-American settlement. The nature of these fires is not well understood. We used lightning strike, thunderstorm activity, and precipitation data to elucidate the seasonal timing of natural fire regimes for southern Ohio. Our results suggest that fires are most likely to be initiated during the growing season (especially August) when there is a high frequency of lightning strikes and thunderstorm activity that occurs simultaneously with dry environmental conditions. We hypothesize that the use of prescribed growing season fires would effectively deter encroachment of shade tolerant hardwood vegetation and foster regeneration of oaks. Such fires would provide an evolutionary basis for the conservation of oak-dominated ecosystems in southern Ohio.