Herbaceous filter strips in agroecosystems:: Implications for ground beetle (Coleoptera: Carabidae) conservation and invertebrate weed seed predation

A 9.3-ba crop field flanked by two filter strips was selected to: 1) assess carabid beetle activity-density and community composition and 2) assess post-dispersal weed seed predation by invertebrates in these habitats. Overall during 1997 and 1998, 12,937 carabid beetles comprising 58 species were collected. Greater species richness and activity-density was observed in filter strips than in the field. A multivariate ordination revealed that year of capture and habitat were important variables conditioning carabid beetle communities. While two omnivorous species known to eat weed seeds [Harpalus erraticus (Say), Anisodactylus sanctaecrucis (F.)] dominated the 1997 captures, two carnivorous [Pterostichus melanarius (III), Pterostichus permundus (Say)] were predominant in 1998. Two omnivorous species, Harpalus pensylvanicus (DeG) and H. erraticus, were primarily captured in filter strips. Weed seed removal was greater in filter strips than in the field. This study shows that habitat management represents a feasible approach to conserve beneficial organisms in farmlands.