Northern forestry and carabids: the case for concern about old-growth species

Two studies in western Canada focus on whether carabid species specialize in use of old-growth forest habitats. In montane lodgepole pine (Pinus contorta Douglas var. latifolia Engelm.) forest, Calathus advena Lec., Carabus chamissonis Fish., Leistus ferruginosus Mnh., Nebria intermedia V. D., Platynus decentis Say, Pterostichus brevicornis Kby., Pterostichus riparius Dej., Scaphinotus marginatus Fisch. and Trechus chalybeus Dej. are common in post-rotation age forest with no history of harvesting, but scarce in or absent from regenerating sites, even 27 years after harvest. Residual populations of old-growth specialists in uncut fragments are exposed to increased contact with habitat generalists and open-habitat specialists from surrounding cut-overs and regenerating forests. Populations of several species of old-growth specialists in lodgepole pine live also in younger, fire-origin stands in boreal aspen (Populus tremuloides Michaux.) stands of the "mixedwood" zone. We hypothesize that they have recolonized from the large surrounding tracts of unburned residual forest remaining after fire. Thus, landscape-scale effects, resulting in changes in regional population size, may alter the probability of species retention in old-growth fragments, and of the recolonization of cut-blocks by particular species characteristic of old-growth.