Relationships among wildfire, prescribed fire, and drought in a fire-prone landscape in the south-eastern United States

Concern over increasing wildfire activity in the last few decades has prompted increased investment in fuels reduction treatments worldwide. Prescribed fire is a commonly used management tool for reducing fuels and modifying subsequent wildfire dynamics, yet the influence of prescribed fire on wildfire is difficult to evaluate empirically due to the often unpredictable nature of wildfire. In this study we evaluated a 30-year record of wildfire, prescribed fire and drought at Fort Benning, a 74000-ha military training installation in west-central Georgia, USA. Annual wildfire incidence declined sharply from 1982 to 2012 as prescribed fire hectares increased. Multiple regression models including both prescribed fire and drought (assessed using the Keetch-Byram Drought Index; KBDI) explained similar to 80% and 54% of the variation in annual wildfire incidence and areal extent, respectively. Current- and previous-year prescribed fire were strongly inversely related to current-year wildfire, suggesting that the cumulative area burned by prescription is important in explaining current-year wildfire incidence. Wildfire activity overall (both incidence and areal extent) was highest during drought years when cumulative prescribed fire hectares were low. Our results suggest some inevitability of wildfire during drought, but also provide evidence for the positive effects of sustained landscape-scale prescribed fire in reducing wildfire activity over time.