Agricultural landscapes for bee diversity and pollination services

Current agricultural landscapes often fail to support bee pollinators in sufficient numbers to maintain essential pollination services to crop and wild plants. Bumble bees are important native pollinators of crops in northern temperate regions, but their communities are changing in response to agricultural intensification and landscape simplification. To maintain these populations it is essential to maintain a mosaic of land-uses providing flowers, which could include the creation of specific bee-friendly habitats. Also the availability of flowering crops may benefit bumble bee populations. However, the degree of spatiotemporal resource continuity resulting from landscape heterogeneity, crop selection and habitat creation may impact bumble bee communities and thus pollination services. For example, it has been suggested that lack of late-season flower-resources limit bumble bee populations. We found support for this contention, because agricultural landscapes with late-season flowering red clover fields sustained significantly more queen and male bumble bees. This suggests that interventions such as flower strips can alleviate population limitation stemming from late-season resource bottle-necks. Occurrence of mass-flowering crops may also influence pollinator communities in adjacent habitats through spatial and temporal spill-over, both to other agricultural habitats and to semi-natural habitats. However, mass-flowering crops could alternatively turn into ecological traps for bees if they are treated with pesticides. We investigated such spill-over effects in a series of experiments replicated at landscape scales, contributing to the knowledge of effects of mass-flowering crops on spill-over and pollination is adjacent habitats.