Date of Award
Master of Science
Ecology, Evolution, and Organismal Biology
Ecology and Evolutionary Biology
Diane M. Debinski
John M. Pleasants
Pollinator species such as butterflies and bees are declining globally primarily due to habitat loss. This is especially concerning within the tallgrass prairie ecoregion of North America, where the land area comprised of native vegetation has declined by an estimated 99%. Thus, tallgrass prairie restoration and management is imperative. The control of invasive plant species such as tall fescue (Schedonorus phoenix) is one aspect of grassland management. In our first study we added herbicide and seeding treatments to control tall fescue and enhance plant diversity, and measured how these combined treatments affect the abundance, species richness, and diversity of butterflies and flowering plants. Five sites were each divided into three patches, and each patch was managed using one of three different herbicide and seeding treatments. These treatments included a non-sprayed control patch, a patch sprayed with glyphosate, and a patch sprayed with glyphosate as well as seeded with a mixture of native plants. Floral resource abundance was significantly higher in patches that were sprayed or sprayed and seeded compared to the control patches. In addition, floral species richness and diversity were significantly higher in patches that were sprayed and seeded compared to the control. Butterfly abundance was marginally significantly higher in patches that were sprayed and seeded compared to the control patches. This study indicates that the control of an invasive grass via herbicide treatments and seeding can potentially provide benefits to native pollinator and flowering plant communities. Restoring grasslands with the goal of improving native plant abundance, species richness, and diversity is another aspect of grassland management. In our second study, we test responses of the native bee and flowering plant communities to three grassland management treatments. Twelve sites were selected for bee and floral resource sampling based on their current land management strategy. Four sites were tallgrass prairie remnants (TGR), four sites were un-grazed restorations (UGR), and four sites were cattle grazed restorations (CGR). Bee community composition was quantified using “bee bowl” and sweep net sampling. Floral resources were measured along transects by counting flowering ramets. Bee health was quantified by measuring relative lipid content in three Halictids, including Augochlora pura, Agapostemon virescens, and Halictus ligatus. Contrary to expectations, bee abundance was significantly higher in UGR sites than TGR sites and floral abundance was significantly higher in CGR sites compared to TGR and UGR sites. There were no differences among treatments in relative lipid content for the three bee species. Within each species, relative lipid content decreased with increased bee mass. Relative lipid content increased over time in Au. pura and H. ligatus but was primarily due to a decrease in bee mass over time, as was seen for all three species. This study indicates that non-remnant grassland management strategies can positively influence native bee and flowering plant communities, and stresses the inclusion of time and insect mass when evaluating community health.
Stein, David, "Evaluating Pollinator Responses to Grassland Management Techniques" (2017). Graduate Theses and Dissertations. 15427.