Arthropod overwintering in agri-environmental scheme flowering fields differs among pollinators and natural enemies

Abstract

Arthropod diversity in agricultural landscapes is important to maintain numerous ecosystem services. Most arthropods, however, need shelter habitats for overwintering embedded in agricultural landscapes. Habitats created by perennial agri-environmental schemes (AES) such as flowering fields can provide such overwintering places in addition to nesting sites and food resources. However, it is unclear, to which extent arthropods use such flowering fields for overwintering. We assessed the emergence of six functionally relevant arthropod groups (wild bees, hoverflies, wasps, carabid beetles, staphylinid beetles and spiders) with emergence cages on wheat fields and on four types of flowering fields differing in temporal continuity (age and time since last soil disturbance). Wild bee richness and abundance was highest in flowering fields that had undergone soil disturbance in the previous year while recent soil disturbance was clearly detrimental. Natural enemies were mostly unaffected by temporal continuity and hoverflies emerged most abundantly from wheat fields. Carabid beetle richness and densities of carabid and staphylinid beetles were positively affected by recent soil disturbance while hoverfly densities were negatively affected. Further assemblage composition of emerging wild bees and carabid beetles differed between habitat types. Our results indicate that most natural enemies overwinter even in flowering fields with low temporal continuity and recent soil disturbance while wild bees need habitats of higher temporal continuity for overwintering. We thus propose a mix of flowering habitats with different degrees of temporal continuity embedded in the agricultural landscape to make AES more effective towards the provisioning of overwintering sites for ecosystem service providers. We conclude that a better understanding of the overwintering ecology of different arthropod groups is required to counteract current biodiversity decline in agricultural landscapes.