Saproxylic beetle tolerance to habitat fragmentation induced by salvage logging in a boreal mixed-cover burn.
Michel St-Germain, Pierre Drapeau, Annie Hibbert.
Saproxylic insect assemblages associated with burned forests are generally abundant and species rich, consisting of a mix of pyrophilous and secondary, opportunistic species depending on time elapsed since disturbance. Life-history traits associated with each group suggest that they may respond differentially to habitat fragmentation caused by salvage logging, with pyrophilous species having a much higher dispersal potential. In a 2-year-old burn highly fragmented by pre- and post-fire logging, we sampled saproxylic beetles in coniferous and broadleaf burned residual stands along a gradient of spatial context including intensity of fragmentation and isolation from source habitat using Lindgren multiple-funnels traps. Beetle assemblages differed in composition between coniferous and broadleaf burned stands, with secondary users dominating the latter. Pyrophilous species increased in abundance with distance from the edge and avoided unburned patches within the fire. Secondary users did not respond negatively to fragmentation or isolation of burned habitats, with one exception, the alleculid Isomira quadristriata (Couper), being overall diverse and abundant throughout the study area regardless of salvage logging prevalence. No deleterious effects of isolation were thus detected in the occurrence patterns of secondary users, even up to 8 km from the edge. Our results suggest that older burns, especially those having some broadleaf cover, are intensively used by non-pyrophilous saproxylic species usually associated with dead wood in green forests and may contribute to maintain broader saproxylic assemblages than originally thought, especially when considering the importance of dead wood volume pulses associated with fire in boreal forests. © 2012 The Royal Entomological Society.