This doctoral dissertation research project is about the influence of climatic variability and topographic gradients on the spatial and temporal variation of landscape patterns of fire severity from the 1700s to the present. Both fire frequency and the annual area burned are strongly related to regional climate and have exhibited increasing trends over recent decades in relation to global warming. However, the ecological effects of increased fire activity are not clearly understood. As a measure of tree mortality, fire severity directly describes one of the major ecological impacts of wildfires. But how sensitive fire severity is to climatic factors or other controls (i.e. topographic factors, vegetation characteristics) is poorly understood. Because fire severity in many forest ecosystems varies over both space and time, long time series of fire severity that quantify spatial patterns of heterogeneity are necessary, both to capture the full range of fire effects and to identify the key drivers of this variation. This is especially true for forests characterized by mixed-severity fire regimes where fire severity is known to be highly variable. This research will adopt a spatially explicit nested research design combining intensive tree-ring sampling, extensive analyses of historical high resolution aerial photography and satellite-based change detection methods to address three primary research goals: 1) to quantify the spatiotemporal variability of fire severity within multiple watersheds from about 1700-present; 2) to evaluate the strength of climatic and topographic controls on landscape patterns of fire severity; and 3) to compare fire severity patterns between historical and contemporary wildfires to assess the role of climate change on fire regime shifts between the two periods. These questions will be examined for Douglas fir (Pseudotsuga menziesii) dominated forests and mixed-conifer western larch (Larix occidentalis) dominated forests, two of the dominant low-middle elevation forests in the northern Rocky Mountains known to exhibit mixed-severity fire regimes.
Information about how spatiotemporal patterns of fire severity have varied over time and which factors have driven this variability is an important framework for scientists, land managers and others interested in past and future ecological effects of wildfires. The detailed understanding of climate-fire severity relationships provided by this research is a novel and necessary foundation for accurate modeling of future fire severity and land management planning in response to currently shifting climatic conditions. Results from this research will be published in various publications and presented to academic and management audiences. Findings will also be broadly disseminated through ongoing partnerships with National Park Service (NPS) managers, U.S. Department of Agriculture (USDA) Forest Service managers and researchers, and investigators at other several universities involved in related research. The project involves the training of undergraduate and graduate students, and as a Doctoral Dissertation Research Improvement award will provide needed support to a promising doctoral student at a critical stage of career development.
