AUTHORS: Michael J. Cunningham-Minnick*, Thomas O. Crist – Miami University
ABSTRACT: Intensively managed agricultural lands are generally considered detrimental to native bees. Large production areas, pesticide use, and reduction of natural habitats are agricultural practices that remove favorable nesting sites and food resources required for diverse, abundant bee communities. Moreover, habitat remnants such as forests are often vulnerable to invasive species, especially along edge habitats between forests and agricultural fields. We studied the roles of local habitat characteristics in forest-crop edges and the surrounding land use and land cover in determining bee species diversity, composition and abundance in Midwestern agricultural landscapes. At the local scale, we predicted that forest edges with greater native floral resources and fewer invasive plants would support more diverse and abundant bee communities. At the landscape level, we predicted that greater areas or connectivity of natural (forest) or semi-natural (grassland and pasture) land cover would lead to greater bee diversity and abundance in forest edge habitats. We sampled the bee community, floral resources, tree species composition, soil texture, and invasive shrub density along 100 x 5-m edges of 12 forest fragments adjacent to corn and soybean agriculture in southern Ohio and Indiana. Mixed effects models containing these habitat variables were compared to those with area and connectivity of land use and land cover within the surrounding 500, 1000, 2500, and 5000-m radius buffers surrounding each forest to predict bee community metrics. Contrary to our hypothesis, invasive flowering shrub density explained 29% and 28% of the variation in bee species richness and abundance, respectively, despite its strong negative association with native floral availability. Land-use and land cover models may suggest important roles for neighboring natural and semi-natural habitats in supporting these forest edge bee communities, or may emphasize that supplemental floral resources of invasive shrubs can play a role in increasing bee diversity and abundance.
