Boreal mixed-wood beetles and the cumulative ecological consequences of disturbance

Boreal forests of Canada, and elsewhere, are increasingly stressed by multiple, potentially interacting disturbances. In addition to natural disturbances like wildfire, anthropogenic stressors associated with increasing demands for natural resources have become critical elements of the disturbance regime in many areas. Thus, biodiversity conservation and sustainable forest management will increasingly depend on our understanding of the cumulative ecological consequences of disturbance.; I examined the combined effects of wildfire and industrial forestry practices on boreal mixed-wood ground beetles and saproxylic beetles, and on the ecological function of one saproxylic species. Ground beetle responses to the individual and combined effects of wildfire, forest harvesting and herbicide-use were species-specific, but disturbance combinations led to a greater decrease in the compositional variability of the entire ground beetle assemblage. For saproxylic beetle assemblages, the combination of wildfire and forest harvesting (postfire salvage logging) reduced species richness and altered species composition to a greater extent that either disturbance alone. Postfire salvage logging also altered the trophic structure of the saproxylic beetle assemblage and was particularly detrimental for wood- and bark-boring species. Through a series of experiments, the abundance of one such species, Monochamus scutellatus scutellatus, was linked to decomposition processes in burned forests. Together, the results of these studies suggest that disturbance combinations should be avoided whenever possible because they may impact not only beetle diversity, but also decomposition processes in forests recovering from wildfire.