Impacts of Dryland Farm Management Systems on Weeds and Ground Beetles (Carabidae) in the Northern Great Plains

Farming systems act as ecological filters impacting cropland associated biodiversity; however, the extent of these effects is largely unknown in the drylands of the Northern Great Plains (NGP), a key conventional and organic crop production region. In this 3-year (2013–2015) on-farm study, we addressed this knowledge gap by assessing the effects of conventional and organic farming systems on weed and ground beetle (carabidae) communities. We observed 25 weed species in conventional and 44 in organic fields. Weed species richness and weed species evenness were 237% and 137% greater in organic fields than in conventional fields. We collected a total of 1520 beetle specimens, representing 28 species in conventional and 37 in organic fields. Beetle activity-density and species richness were 220% and 156% greater in organic fields than in conventional fields. Both weed and ground beetle communities differed between conventional and organic fields, indicating that farming systems act as distinct ecological filters. We conclude that, in the drylands of the NGP, adoption of organic farming enhances weed abundance which could have potential management challenges, but provide floral resources to the pollinators and parasitoids. Similarly, greater diversity of ground beetles could enhance conservation biological control of crop pests, ultimately supporting for sustainable agriculture.