Grazing influences the diversity and community composition of bees and other insects in livestock pastures

Pollinators contribute to the establishment of perennial native forages, but little is known about the effect of grazing practices on pollinator abundance and diversity in livestock pasture ecosystems. Objective of this study was to examine the impact of grazing on bees and other non-bee insects in livestock pasture established with seed mixes of native forb/legume/grass (FLG) and warm season grasses (WSG). Each pasture was divided into two halves (in a split-plot design) using an electric fence in which one plot was grazed and the other plot was non-grazed. Blue vane traps and a pair of yellow and blue pan traps were used for sampling bees and other insects. A diverse array of bees (total 59 species) and non-bee insects (total 93 species) were documented. The abundance, diversity, and evenness of bee communities and other insects were greater in non-grazed plots as compared to grazed plots. However, species richness, as measured by rates of species accumulation relative to sampling effort, was not different among treatments. Results show that a diverse community of bees and other insects may be found in livestock pasture systems, but that reduction in bee and insect diversity in grazed areas highlight the importance of rotational grazing regimes to allow for sufficient floral resources for pollinators at relevant scales.