A Comparison of Forest Edges and Interiors on the Infestation Dynamics of Dryocoetes Confusus Swaine (Coleoptera: Curculionidae: Scolytinae)

Abstract

The western balsam bark beetle, Dryocoetes confusus Swaine, is ubiquitous throughout mature subalpine fir ecosystems in British Columbia and is considered the most serious mortality-causing disturbance. Harvesting subalpine fir has increased recently; however, little is known about how this anthropogenic disturbance affects the population dynamics of D. confusus. Using high resolution photography and ground surveys, this study compared stand composition and D. confusus attack levels along natural forest edges and edges created by harvest <10 years or >15 years ago, to forest interiors, where no anthropogenic disturbance had occurred. Subalpine fir density and D. confusus attack were lower in natural forest edges than in harvested edges. There were differences in attack levels between harvest treatments, but the overall impact by D. confusus was similar to D. confusus-caused mortality seen in forest interiors. More recent attack differed among edge treatments, with the highest levels in the <10 years since harvest treatment and the lowest levels in natural edges. This short period of increased activity by D. confusus post-harvest has minimal