Evaluating the effects of soil tillage on ground nesting bees in the southeastern United States

Abstract

Pollination by native bees is an economically and ecologically valuable service, necessary in both agricultural and natural landscapes. The majority of bee species nest below ground, an aspect of their biology that raises questions concerning how common farming practices – such as soil tillage affects their abundance and diversity. Tillage methods are broadly categorized as belonging to either a conventional or conservation regime. Conservation tillage is associated with lower intensities of soil disturbance compared to conventional tillage, as well as requiring the buildup of soil surface residues. In this work, I investigated the effects of tillage on ground nesting bees by intensively sampling with soil emergence traps among four treatment groups: (1) Conventional tillage, (2) Conservation tillage, (3) Reduced tillage, and (4) Field edge. Soil emergence traps were deployed weekly from March-October 2021, and again from March-November 2022. Results from emergence trap collections detected no significant differences among the tillage treatments; however, we observed significantly higher incidence, abundance, and diversity of bee assemblages in the Field Edge treatment compared to all tillage treatments. Our results suggest that bee nesting is depreciated in cultivated fields regardless of tillage type. Implications from this work applies to conservation efforts aimed at mitigating the loss of native bee biodiversity, as well as producers looking to increase the contribution of native bees in agricultural landscapes.