Impacts of farm management practices on pollinator community and pollination services in the Northern Great Plains

Farm management or cropping practices act as ecological filters influencing pollinator communities and their services. Between 2013 and 2015, we assessed the effects of organic and conventional farm management practices on pollinator communities and services at Big Sandy MT. In 2013 and 2014, pollinators were collected by placing cup traps every five meters along the 55-meter transects located in three conventional and three organic fields. Additionally, as a proxy for measuring the ecosystem services provided by flowering weeds, we placed five hives of Bombus impatiens in each field for two months during peak flowering of crop weeds in 2014 and 2015. The most common pollinators recorded were members of these genera: Agapostemon, Halictus, Lasioglossum, and Eucera. The impacts of farm management practices on bee abundance and Simpson’s diversity index were compared using repeated measures analysis of variance. Colony relative growth rate was compared across farm management practices using a t-test. Preliminary results of the 2013 trials indicated that there was no significant difference in diversity index (P-value = 0.47) and bee abundance (P-value = 0.11) between two management practices. However, the relative growth rate of B. impatiens colonies in 2014 was higher (P = 0.05) in organic than in conventional fields (conventional = 0.05 ± 0.003 and organic = 0.06 ± 0.002 g g^-1 wk^-1). Higher colony growth rate in organic fields may be due to the greater amount of pollen and nectar provided via weed diversity. Hence, greater floral diversity in organically managed wheat cropping can enhance pollination services.