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RESEARCH PRODUCT

Responses of boreal carabid beetle assemblages (Coleoptera, Carabidae) to clear-cutting and top-soil preparation

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Today, forestry is the most important disturbance force in Fennoscandian boreal forests, having remarkably altered fauna and flora in this biome. However, since the late 1900s, forest-management practices have been modified to better consider biodiversity while harvesting timber. For example, green-tree retention, gap felling, and lighter top-soil preparation methods (harrowing) have been introduced, but little is known about the ecological effects of these changes. We sampled carabid beetles in seven clear-cut stands that were subsequently harrowed. We studied the effects of (1) clear-cut size by comparing carabid catches of small gaps (ca. 0.16 ha) with those of larger clear-cuts (ca. 2 ha), and (2) micro-site type within stands by comparing carabid catches of strips of bare soil to those of drifted humus (adjacent to bare-soil strips) and undisturbed (not scarified) forest floor. We detected only slight effects of clear-cut size on the assemblage structure, but clearer differences at species and ecological-group levels among the three compared micro-site types. The catches of forest carabids, and flightless carabids, were higher in the undisturbed micro-sites as compared to bare-soil ones, whereas open-habitat carabids showed the opposite abundance pattern. The variation among study blocks, and logging per se (compared to un-logged mature stands), had more pronounced effects on carabid assemblage structure than either clear-cut size or micro-site.