Pollinators, especially native bees, are experiencing striking declines worldwide. Approximately 80% of bee species in North American grasslands build nests in the ground. Grasslands tend to include natural or semi-natural habitat, including remnants that are unplowed parcels of pristine land, restorations that are plantings of native plants, and old fields left fallow from agriculture. However, bees may not build nests in all land types. For instance, bees may not build nests in areas of high plant diversity where they forage for resources. I ask the question: do land types differ in nesting quality for ground-nesting bees? For this study, I quantified density of ground-nesting bee nests at 8 sites, each with 3 land types, for a total of 24 locations. I placed traps used for collecting ground-nesting bees on 1,440 randomly chosen GPS coordinates, prior to bee emergence each day. I measured microhabitat data on vegetation including richness and abundance along with soil metrics including texture, slope, aspect, shade, and bare ground. To avoid data overload, I sampled all coordinates with bee nests along with 10 additional randomly chosen coordinates per location.
Results/Conclusions
Bee nest density differed substantially, driven by differences in both land type and site, according to a generalized linear model with a binomial distribution (p-value < 0.0001). Restorations had 9% fewer bees captured compared to remnants and old fields. Overall, I had a capture rate of 0.07% utilizing these trapping methods. Additionally, soil texture analysis suggests the majority of nests were found in sandy-loam or silty-loam soils. This evidence suggests that the three land types can support ground-nesting bees, but restorations may not provide as much habitat for ground-nesting bees. I will also present results about the relationship between the other microhabitat characteristics and nesting densities. I predict that a diverse vegetation community managed for duff and litter, a large percentage of bare ground per trap, and southeastern aspect may predict nest presence. The information from this study will improve our understanding about where native bees nest and allow land managers to make decisions to protect, conserve, and prioritize habitat suitable for ground-nesting bees.