Initial Responses of Carabidae (Coleoptera) to Intensive Biomass Harvesting and Soil Compaction in Aspen Stands of the Huron-Manistee National Forest, Oscoda County, Michigan

During the 1990s, the United States Forest Service implemented several studies to measure the impacts of organic matter removal and soil compaction on forest productivity in forest ecosystems throughout the country. One site was in northeastern Lower Michigan on the Huron-Manistee National Forest in Oscoda County. This site was dominated by mature quaking aspen (Populus tremuloides Michx.) and bigtooth aspen (P. grandidentata Michx.) growing on sandy loam soils. The three organic-matter removal treatments at the site included: 1. stem-only harvesting (SOH); 2. whole-tree harvesting (WTH); and 3. whole-tree harvesting plus forest floor removal (FFR). The three soil compaction treatments also at the site included: 1. no compaction beyond normal levels resulting from tree harvesting; 2. moderate compaction; and 3. heavy compaction, i.e., increasing surface soil bulk density by about 0%, 15%, or 30%, respectively. These silvicultural treatments were conducted during the winter and spring of 1994, and thus offered an opportunity to determine how carabid beetles would initially respond to these forest management practices. Thus, carabids were collected the year following treatment with pitfall traps from June to September in 1995 on all treatment sites and in nearby uncut forest stands. Overall, 3690 carabid specimens were collected, representing 46 species. Many carabids showed a significant response to the organic matter removal treatments, some positively and some negatively, but few showed a response to the compaction treatments. An NMDS ordination indicated that the carabid assemblages from the uncut aspen stands were distinct from all treatment plots, but most distinct from the FFR-plot assemblages. Catch rates of the Harpalini (12 species) were highest on the FFR plots. For some of the most collected species, catch rates of Myas cyanescens Dejean (540 specimens), Pterostichus pensylvanicus LeConte (208), and Synuchus impunctatus (Say) (473) were generally highest in the uncut aspen stands and lowest in the FFR plots; for Cyclotrachelus sodalis (LeConte) (638) and Pterostichus stygicus (Say) (307) catch rates were highest in the SOH and WTH plots and lowest in the uncut aspen stands; and for Pterostichus mutus (Say) (392) catch rates were highest in the FFR plots and lowest in the uncut aspen stands. Of the 46 species, 8 were significant indicator species: 2 for the FFR plots and 6 for the uncut aspen plots.