MODERN CALIBRATION AND NEW APPROACHES TO FIRE-SCAR ANALYSIS

BAKER, W.L. (1) AND KOU, X. (2)

(1) Department of Geography, University of Wyoming, Laramie, WY 82071; (2) College of Life Sciences, Beijing Normal University, Beijing, P.R. China

Fire historians interested in fire-climate relationships need to know how to filter fire-scar records to find the most important fires, as it is well known that small spot fires dominate both modern and historical fire records. For example, only 1% of the 40,380 fires that burned in western ponderosa pine forests from 1980-2003 account for 97% of the burned area, the other 99% of fires account for only 3% of burned area. These 1% of fires are the largest fires and do the most ecological work in ecosystems. They are also the ones that kill people and destroy their homes. Thus, large fires are often most of interest in understanding the role of climate in fire regimes. One way to determine how to filter fire-scar records to find the key 1% of fires is to compare modern area burned data with fire-scar data from the same sites, a modern calibration. This presentation focuses on modern calibration and the collection and treatment of fire-scar data to estimate fire rotation, which is primarily determined by large fires. This discussion builds upon (1) a modern calibration using data from field studies, (2) a landscape simulation analysis of fires and fire-scar sampling, and (3) an analysis of a new method of deriving fire rotation from fire scars. Traditional composite methods of fire-scar analysis often underestimate, but can overestimate the fire rotation, even with restriction to 25% of scarred trees. A new method provides accurate and unbiased estimates of fire rotation, but requires an estimate of the scarring ratio. A landscape sampling approach is needed to identify the few large fires that most contribute to fire rotation.