PARENT SESSION
Oral Session #41: Agroecology and Urban Ecology. Presiding: M. Liebman.
Wednesday, August 8, 2001. 8:00 AM to 12:15 PM. Hall of Ideas L&M.
Impact of agricultural management systems on carabid beetle communities and post-dispersal weed seed predation.
DAUER, JOSEPH1, FOX, TYLER2, MENALLED, FABIAN3, 1 2 3
ABSTRACT- The goal of our study was to assess the influence of different management systems on carabid beetle activity/density and weed seed predation. The research was conducted in three annual crop systems at the Long Term Ecological Research site at the Kellogg Biological Station, Michigan. Studied systems included: 1) conventional (high-chemical input, moldboard plowed), (2) no-till (high-chemical input, no tillage), and (3) organic (no external chemical input, moldboard plowed). Our approach consisted of a twofold study. First, assessment of carabid beetle/activity density using pitfall traps. Second, evaluation of invertebrate post-dispersal weed seed predation. Seed removal of fall panicum (Panicum dichotomiflorum) and common lambsquarter (Chenopodium album) was determined using 2 treatments: 1) vertebrate exclosures, which allowed invertebrates to remove seeds, and 2) total exlosures, which prevented both vertebrates and invertebrates from removing seeds. A total of 1610 carabid beetles comprising 33 species were sampled. Three generalist predators (Poecilus chalcites, P. lucublandus, and Anisodactylus rusticus) accounted for 82% of the captures. While 54 % of the beetles were collected in the conventional system, 25% were sampled in the no-till system, and 21% in the organic system. A total of 204 seed predators were trapped with 132 captured in the no-till system, 36 in the conventional system, and 36 in the organic system. In accordance, weed seed removal was significantly higher in the no-till system than in the conventional and in organic systems.
KEY WORDS: agoecology, ground beetles, weeds, annual crop systems