| Fire and Climatic Variability in the Inland Pacific Northwest: Integrating Science and Management |
This project analyzes relationships between climate and topography and spatio-temporal patterns in historical fire regimes in the inland Pacific Northwest, using fire-history data from the Wenatchee, Okanogan, and Colville National Forests. The primary constraints on fire occurrence and fire extent change across spatial scales. At small scales (within watersheds), topography controls fire sizes, and rates of fuel accumulation control fire frequency. Viewed across the entire study area, climatic variation and extreme climatic conditions such as drought control the area burned and the synchrony between fires. These constraints have clearly weakened, however, since the beginning of active fire suppression. Understanding how the dominant processes that drive fire regimes have changed across scales and under different management enhances the knowledge of fire as a keystone process in ecosystem dynamics and improves the ability to anticipate severe fire seasons, allowing for efficient allocation of resources.
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Quantifying Spatial Structures Associated with Low-Severity Fire Regimes in the Eastern Cascade Mountains of Washington
Fire regimes are complex systems that represent an aggregate of spatial and temporal events whose statistical properties are scale-dependent. Despite the breadth of research regarding the spatial controls on fire regime variability, there are few datasets available with sufficient resolution to test spatially explicit hypotheses. Spatial relationships were analyzed for an extensive, spatially distributed network of geo-referenced, fire-scarred trees in eastern Washington. The spatial dependence of historical fire regimes varied within and among sites. Spatial controls on low-severity fire regimes within similar dry forest ecosystem types operate at varying spatial scales, reflecting topographic properties of local landscapes. However, only portions of the spatial variability in fire events can be attributed to topography. In complex, rugged terrain, modal fire sizes were 150 ha or less, whereas in more open and rolling terrain, the spatial scale of fire occurrence was not controlled by landform. Results illustrate that the statistical spatial characteristics of fire regimes change with landform characteristics within a forest type, suggesting that a simple relationship between fire frequency and forest-type does not exist. Quantifying the spatial structures in fire occurrence associated with topographic variation demonstrated that fire regime variability is scale and location dependent. By identifying the scale dependencies associated with specific fire regimes, the regime can be matched to the scales of the controlling factors with greater precision, thus increasing the ability to evaluate their relationship.
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