Influences of forest roads on the spatial pattern of wildfire boundaries

Although many studies have examined fire ignition and fire spread, the cessation of fire is largely unexplored at a landscape scale. Therefore, we sought to examine the effects of forest roads on fire boundary locations. We analysed six fires within the Wenatchee National Forest in Washington State. Geographic Information System datasets of fire boundaries and environmental variables were obtained from government agencies. Case points were sampled on the fire boundaries, and five matching control points were sampled inside the fire boundary for each case. Matched case-control logistic regression was performed to identify the environmental differences between each case and its set of control points. We found that for four of the fires, fire boundaries were significantly closer to roads than to random control points. Various terrain and vegetation attributes were also correlated with fire boundary locations. In the fires where road effects were significant, they had stronger effects than any of the other environmental constraints on fire boundary locations. These results suggest that road effects on fire cessation should be incorporated more explicitly into landscape-level assessment of wildfire risk and analyses of fuel treatment effectiveness.