AUTHORS: Brooke A. Cassell, Portland State University; Robert M. Scheller, North Carolina State University; E. Louise Loudermilk, USDA Forest Service; Matthew D. Hurteau, University of New Mexico
ABSTRACT: Temperatures in the western USA are rising, leading to earlier snowmelt, smaller snowpack, drier fuels, and longer fire seasons. In dry mixed-conifer forests, these conditions are already resulting in more frequent and more severe wildfires, and this trend is projected to continue. Fuel treatments, including mechanical removal of trees and prescribed burning, are known to be effective in reducing wildfire behavior, particularly in forests that were historically dominated by frequent fire-maintained forest types, but the effectiveness of these treatments is uncertain under climate change. Better understanding of the factors that influence the effects of fuel treatment on wildfire activity at large spatial scales and over time is needed while accounting for complex interactions among forest dynamics, fire sizes and severities. We investigated these interactions by simulating forest succession, forest management, and wildfire activity under historical weather and extreme fire weather in a mixed-conifer landscape in the Blue Mountains region of central Oregon. Forest succession and disturbance (e.g., tree harvest, prescribed burning, and wildfire) were dynamically modeled over a 100-year period. We used scenario-building to compare the effectiveness of different management strategies at reducing the spread and severity of wildfire. Spatial optimization of treatments on the landscape was achieved by running 1000 simulation-years of wildfire under extreme conditions on an unmanaged landscape to identify locations that are most likely to burn at high severity (i.e., with a high proportion of tree mortality). Concentrating fuel treatments in these locations was at least as successful, and in some scenarios more successful, at reducing wildfire spread and severity at the landscape scale as placing treatments across the entire landscape. The results of this study offer insight to forest management under extreme weather conditions and help inform decision-making by identifying strategies for spatially optimizing fuel treatments.
