Fire Severity Patterns in The Klamath Mountains of Northern California and Southwestern Oregon

At the stand scale, wildfire behavior can be modified by altering the quantity, structure, and arrangement of fuel (vegetation) using silvicultural treatments such as forest thinning and prescribed fire. At the landscape scale, mathematical models and empirical data indicate that the type and spatial arrangement of treated areas can influence the ability of high intensity fires to move across the landscape. However, developing a strategy for applying fuels treatments across a landscape is not always straight forward given concerns for potential impacts on habitats of both terrestrial and aquatic species. In the Klamath Mountains of northern California and southwestern Oregon, fire severity patterns, both from recent fires and reconstructed from the tree-ring record, may help to inform the process. Here, except on the western edge near the coast, fire severity patterns have been found to be strongly associated with topography. For example, high severity effects are more often found on the upper thirds of especially south and west facing slopes. In contrast, low severity effects are more often found in canyon bottoms (lower thirds of slopes) and on north facing slopes. These effects are often accentuated by the influence of strong thermal inversions that set up after several days of burning, filling canyons with smoke and moderating fire behavior. Further, the tree-ring record indicates that before the onset of fire exclusion, topographic features bounded many fires. These topographically influenced patterns of severity over time helped to determine patterns of habitat (for example, where late-seral, old-growth habitat is likely to be developed and sustained). We suggest that understanding the expected patterns of severity can help managers to develop broad landscape strategies for fuels management as well as strategies for using wildfires to minimize unwanted fire effects and achieve various resource objectives