With the goal of conserving native bees, current recommendations for improving habitats include increasing available floral resources by planting diverse seed mixes. However, these recommendations only account for the nutritional needs of bees while the availability of equally important nesting resources is often ignored. Here we used a novel system to investigate the effects of seed mix diversity on abiotic factors previously associated with nest sites of ground-nesting bees—available bare ground and soil temperature, moisture, and compaction—and on the occurrence of nests. We used standard bee-collecting techniques and a newer method using soil emergence tents (E-tents) to assess how seed mix diversity affects the distribution of bees. Plots planted with the highest-diversity seed mixes had the greatest amount of available bare ground and the highest soil temperatures at the surface and depths commonly associated with bee nests. The observed changes suggest these areas should be preferred by ground-nesting bees, but nest occurrence did not vary significantly among treatments. However, foraging bee species richness and abundance was greatest in plots planted with the highest-diversity seed mixes. Failure to detect a response in nest occurrence to seed mix diversity may be the result of low bee nest density, manifested in only a few nests being detected and low statistical power. We conclude that the current recommendation of planting highly diverse seed mixes provides adequate nutritional resources and improves some of the key abiotic factors associated with selection of nest sites by ground-nesting bees.
Anderson, Nicholas and Harmon-Threatt, Alexandrea, "The Effects of Seed Mix Diversity on Soil Conditions and Nesting of Bees in Prairie Restorations" (2016). 2016 North American Prairie Conference. 17.