Collaborative Research: Climate-Fire-Ecosystem Linkages on Decadal to Centennial Time Scales in the North Rockies

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SBR-9719411 Swetnam University of Arizona This three-year, collaborative, multi-disciplinary research project reconstructs the fire, vegetation, and climate history of the sub-alpine forests of the Selway-Bitterroot Wilderness Area in northern Idaho and western Montana over 2,000 years. Its purpose is to examine the linkages among climate, fire regimes, and vegetation composition at different temporal and spatial scales. The variation in and interaction of climate, fire, and vegetation shape the landscape. The processes of interaction vary according to the temporal and spatial scale of analysis. At century-to-millennial temporal scales and at landscape-to-regional spatial scales, large changes in climate determine fire regime and vegetation composition. The linkages between fire and vegetation at these gross scales is less clear. At annual-to-decadal temporal scales and at the watershed spatial scale, fire frequency, size, and severity are determined by climate/weather, vegetation, and ignition frequency. In these finer scales, the linkages between fire and vegetation are fairly well developed: vegetation determines fuel availability, and fires create a landscape pattern that shapes vegetation recovery. Investigators will derive information on the frequency of past fires from charcoal and pollen data in lake sediments, tree-ring records, and tree-stand age information. They will calibrate the lake-sediment and tree-ring records against historical fire maps, to estimate the spatial extent of fires. The data will be compiled at the watershed, landscape, and regional scales. They will develop climate reconstructions from Pinus albicaulis and Larix lyalli tree-ring-width chronologies for the last 300+ years in each watershed. These reconstructions should yield an understanding of fire chronology and synoptic climatic conditions giving rise to prehistoric fires. In the western United States, whether late-twentieth-century fire regimes reflect a shift in climate, a product of human activity, or current management practices is a topic of scientific and public-policy debate. This research should provide data on fire history, vegetation, and climate, and move toward understanding the temporally and spatially specific processes of interaction among these elements.