The potential influence of mountain pine beetle (Dendroctonus ponderosae) control harvesting on grizzly bear (Ursus arctos) food supply and habitat conditions in Alberta

Abstract

In response to the mountain pine beetle (Dendroctonus ponderosae) threat in Alberta, forest companies plan to surge harvest 75% of susceptible (mature) lodgepole pine (Pinus contorta) stands over 20 years. To assess potential changes to grizzly bear (Ursus arctos) habitat, I projected food availability over 60 years in the Upper Foothills. I also examined grizzly bear response to pine age, and its interaction with elevation and edge proximity. Post surge, forbs were predicted to increase by 25% and fruits by 2%. After 60 years, forbs should remain above (13%) while fruits could decline below (10%) pre-harvest conditions. Less Vaccinium membranaceum shrubs above 1228m and reduced Vaccinium myrtilloides fruit production below 1228m contributed to the decline. If the surge cut proceeds, efforts should be made to increase fruit production by enhancing shrubs at specific environmental conditions (age, elevation). Small cut-blocks near non-harvested pine seemed to be particularly beneficial for bears.