Gradients in abundance and diversity of ground dwelling arthropods as a function of distance to tree rows in temperate arable agroforestry systems

Ground dwelling arthropods present in agricultural systems regulate multiple ecosystem services (ES), such as nutrient and carbon cycling and biological pest control. The presence of semi-natural landscape features, such as the tree component of agroforestry systems (AFS), can contribute to functional agrobiodiversity and optimize the delivery of such ES in agricultural landscapes. In temperate AFS, however, potential patterns in abundance and diversity have scarcely been investigated for detritivorous soil dwelling arthropods and only to a limited extent for predatory arthropods. Therefore, we have assessed the abundance and diversity of woodlice (Isopoda), millipedes (Diplopoda), rove beetles (Coleoptera: Staphylinidae) and carabids (Coleoptera: Carabidae) as a function of the distance to the tree row in a set of temperate arable AFS. Abundance and diversity of woodlice and millipedes were significantly higher in the tree rows than in the arable zone. In the case of mature trees, a higher abundance of detritivores was also observed in the arable zone close to the trees. Tree presence did not consistently lead to higher abundance of predatory arthropods, but a limited increase in carabid diversity was observed in the arable zone close to the tree rows. These results indicate that in temperate AFS, the trees and the associated understory vegetation strip contribute to the preservation of arthropod biodiversity and the enhancement of associated ES in the tree rows and in the arable field zone.