Geographic analysis of the impacts of mountain pine beetle infestation on forest fire ignition

In British Columbia, Canada, the largest mountain pine beetle outbreak on record has resulted in changes to fuel complexes that may alter fire regimes. The goal of this study is to analyze the relative importance of mountain pine beetle infestations as a determinant of forest fire ignition density in British Columbia. Fire ignitions data for the years 2000 to 2007 were modelled with covariates (weather, topography, ignition source, and the nature of the mountain pine beetle infestation) in 1km by 1km cells in the Montane Cordillera ecozone. Kernel density estimation was conducted for each fire season to illustrate broad scale trends in fire occurrence and regression trees were used to analyze the relative importance of each covariate. Results indicate precipitation, temperature, and Seasonal Severity Rating were the most influential determinants of fire ignition densities. While mountain pine beetle covariates were of lesser importance, moderate stand level tree mortality was more important for predicting the highest modelled fire ignition density values than high or extreme level mountain pine beetle mortality. Elevated fire ignition density was also associated with forests attacked by mountain pine beetle both one and six years previous, while other years were less important predictors.