Pollinators utilize both traditional and forb-supplemented set-aside fields in agriculture

Abstract

Agriculture relies on pollinators, yet paradoxically, agricultural practices can harm them, including through habitat simplification. The diversification of agricultural landscapes may support pollinators by providing varied foraging and habitat resources. Grassland set-asides are often established on farms to restore soils for crop productivity, and may have the co-benefit of providing resources for pollinators. Set-asides may also be supplemented with forbs for enhanced pollinator benefit, but few studies have investigated pollinator use of these fields compared to crop fields, and across set-aside management practices. Here, we use passive traps and net surveys to assess the flower-visiting insect community in three farm field types; traditional (grass-dominant) set-asides, forb-supplemented set-asides, and non-pollinator-dependent crop reference fields, to evaluate the potential for each to provide resources for pollinators. We found higher abundance of putative wild pollinators in forb-supplemented set-asides compared to crop fields, and higher species diversity in traditional set-asides compared to crop fields. Bumble bees were more abundant in both set-aside types compared to crops, while honey bees visited flowers in forb-supplemented sites the most. The diversity of wild pollinators and abundance of bumble bees in traditional set-asides occurred despite their lack of floral supplementation, suggesting that they may support pollinators by providing other resources (i.e., nesting or graminoid nutritional resources). We demonstrate that pollinators utilize both traditional and forb-supplemented grassland set-asides more than non-pollinator-dependent crop fields. Future studies to elucidate specific resource use by pollinators in set-asides across management types are needed.