Many fire history studies have evaluated the temporal nature of fire regimes using fire interval statistics calculated from fire scars. More recently, researchers have begun to evaluate the spatial properties of past fires as well. In this paper, we describe a technique for investigating spatio-temporal variability using a geographic information system (GIS). We used a dataset of fire-scarred trees collected from four sites in eastern Washington, USA, ponderosa pine (Pinus ponderosa C. Lawson) forests. The patterns of past fires recorded by individual trees (points) were converted to two-dimensional representations of fire with inverse distance weighting (IDW) in a GIS. A map overlay approach was then used to extract a fine-grained, spatially explicit reconstruction of fire frequency at the four sites. The resulting classified maps can supplement traditional fire interval statistics and fire atlas data to provide detailed, spatially heterogeneous estimates of fire frequency. Such information can reveal ecological relationships between fire and the landscape, and provide managers with an improved spatial perspective on fire frequency that can inform risk evaluations, fuels reduction efforts, and the allocation of fire-fighting resources
