Impact of agricultural management on carabid communities and weed seed predation

This study evaluated the relationship between diversity and activity-density of carabid beetles and invertebrate weed seed predation in conventional, no-till, and organic management systems in the Midwest USA. Carabid beetles were sampled with pitfall traps and invertebrate seed predation rates of fall panicum and common lambsquarters were assayed with exclosure cages. Total carabid activity-density was over two times higher in the conventional systems compared to the no-till and organic management systems. In contrast, activity-densities of seed-predating carabid species were over three times higher in the no-till compared to the conventional and organic systems. Carabid diversity was higher in the no-till and organic systems compared to the conventional system, and a multivariate analysis showed that carabid community structure was distinct among the three systems. Predation of fall panicum and common lambsquarters seeds was often over two times higher in the no-till compared to the conventional and organic systems, and there was a strong correlation (r > 0.94) between seed removal rates and the total number of carabid seed predators captured in each system.