Intermountain West lightning-caused fires: climatic predictors of area burned.

Abstract

An increase in continuous fine fuels promoted by the expansion of aggressive annual exotic grasses in the Intermountain West has altered the region's fire regimes, with both ecologic and economic ramifications. I examine the predictive nature of seasonal climatic variables, seasonal precipitation and temperature data up to 2 years before the actual summer fire season, to forecast the area burned by lightning-caused fires during the 13 fire seasons (1980-1992). Five climatically-distinct regions in the shadscale, sagebrush-steppe, sagebrush-semidesert, and open pine with grass communities of California, Idaho, Nevada, Oregon, and Utah were included in the analysis. The amount of associated variance ranged from 43 to 62 % between area burned and seasonal climatic variables. Results show that the seasonal climate that promotes fue is distinctly regional, even in areas of similar vegetation. However, the area burned increases primarily when the climate favors the growth of annual grasses over perennial species, or promotes either cooler or wetter conditions during the previous summer (fire) seasons. These results provide land managers with additional information for making decisions on presuppression activities.