Bee diversity in tallgrass prairies affected by management and its effects on above- and below-ground resources.
Abstract
Habitat management methods are crucial to maintaining habitats in the long term and ensuring vital resources are available for declining species. However, when management focuses on a single resource there is the potential to reduce or degrade other critical resources and negatively affect species of concern. Although both floral and nesting resources are critical to supporting bee populations, little consideration is given to the availability of nesting resources. Given known effects of management methods on soils, where the majority of bees nest, and floral food resources, increasing our understanding of management effects on both soils and floral resources is important to improving bee conservation efforts. In 20 tallgrass prairie plots managed under 1 of 3 common methods: burning, haying and patch-burn grazing, we assessed effects on bee communities and necessary above- and below-ground resources. We also considered how management and resources affected below-ground nesting in each prairie. Management type affected both soil conditions and floral resources with patch-burn grazing sites providing overall worse resources for bees compared to ungrazed sites. Soil conditions were also important for predicting most aspects of the bee community including abundance and community composition. Soil conditions also decreased floral richness and Floristic Quality Index (FQI). This suggests management affects bee communities both directly and indirectly through soil. Increased nesting was observed in sites with greater floral abundance and soil conditions that correspond to increased bare ground, lower soil moisture and warmer soil temperatures suggesting management that helps increase floral abundance and improve soil conditions could be critical to increasing bee nesting. Synthesis and applications. Measuring and tracking bare ground, Floristic Quality Index (FQI) and floral richness may help managers determine if their management methods are adversely affecting bees. Grazing and haying management negatively affected the bee community, vital nesting and floral resources and nesting rate. These managements may need to be avoided to meet bee conservation goals in prairies. Additionally, while soils have been largely overlooked, we found soil conditions to be an important predictor for bee communities and floral resources, and should be considered more explicitly in conserved areas.