SPATIAL AND TEMPORAL VALIDATION OF FIRE SCAR DATA IN A FREQUENTLY BURNED ARIZONA WILDERNESS AREA

FARRIS, C.A., BAISAN, C.H. AND SWETNAM, T.W.

Laboratory of Tree-Ring Research, The University of Arizona, 105 W Stadium, Tucson, AZ 85721

Understanding the long-term effects of fire and climate variability on ecosystems requires reliable fire history reconstructions. Different data sources and estimation procedures can confound the interpretation and “accuracy” of various fire frequency metrics. The purpose of this research was to compare key spatial, temporal, and seasonal fire frequency parameters developed from point-based fire scars and area-based fires perimeter maps. Ponderosa pine forests in the Rincon Mountains of southern Arizona have experienced an unusually high frequency of well-mapped 20th century fires, with some individual stands having burned at least eleven times since 1937. Our independent fire scar record captured all mapped fires that burned more than 40 hectares and resulted in Natural Fire Rotation estimates within 3 years of the mapped record. Synchronous fire scar dates most often represented large, continuous burns rather than the occurrence of numerous small fires. Moreover, spatially explicit patterns of fire frequency interpolated from fire scar data were strongly correlated (r = 0.81) with the mapped data and had evenly distributed errors. These results indicate that both spatial and temporal fire history parameters can be accurately reconstructed from point-based fire scar data given an adequate distribution and number of plots. We will discuss key implications of these findings with respect to the interpretation of fire history data for climate-fire research.