HABITATS AND MANAGEMENT ASSOCIATED WITH COMMON GROUND BEETLES (COLEOPTERA, CARABIDAE) IN A MICHIGAN AGRICULTURAL LANDSCAPE

The associations between common ground beetles and habitat and managem ent characteristics were studied in an agricultural landscape that com prised part of the Long-Term Ecological Research site in southwestern Michigan. The 42-ha area included 7 habitat treatments, which represen ted 4 annual cropping systems in wheat, Triticum aestivum L., corn, Ze a mays L., soybean, Glycine max (L.) Merr., rotation; 2 perennial crop systems (alfalfa, Medicago sativa L., and Populus); and a native succ ession habitat. Pitfall traps were used to sample adult ground beetles during the growing seasons of 1994 and 1995. Four species numerically dominated the trap catches and together accounted for 87% of the tota l specimens collected: Cyclotrachelus sodalis (LeConte), Poecilus lucu blandus (Say), Pterostichus melanarius (Illiger), and Agonum placidum (Say). Differences in representation of these common species were most pronounced between perennial and annual plant systems. However, tilla ge also influenced the relative abundance of these species. The adult- overwintering, spring-breeding species, P. lucublandus and A. placidum , were most common in the annual crop habitats, particularly those und er conventional tillage. Catch numbers of these 2 species were correla ted positively suggesting similar habitat preferences or responses to management practices. In contrast, C. sodalis, a larval-overwintering, autumn breeder, was most common in the perennial crop systems and the annual crop system receiving no tillage. The exotic species P. melana rius showed the least response to the agricultural habitat treatments but was more abundant in managed crop habitats compared with the unman aged succession habitat. Cluster analysis based on these 4 species ind icated that plant type and tillage were important in distiniquishing t he carabids of these habitats. The potential implications of these fin dings for conserving or enhancing ground beetle populations in agricul tural systems are discussed.