Potential of seed mixes to provide nesting habitat for ground-nesting bees

Restored tall grass prairies provide essential foraging and nesting habitat for ground-nesting bees, and floral diversity and abundance are essential for pollinator conservation efforts. However, tallgrass prairie seed mixes used for pollinator conservation management are often cost prohibitive and can be over $1,000 per acre. Varying the design of seed mixes can lower the cost of the mix but it is unknown how these changes affect the nesting habitat of ground-nesting bees. Our research objectives are to determine if distinctions in forb:grass ratios and seed density in tallgrass prairie seed mixes affect the activity of ground nesting bees.
Emergence traps were used to make direct measurements of areas used by bees for three treatment levels of forb:grass ratios (low, medium, high) and two seed density levels at a tallgrass prairie seed mix experiment in southern Minnesota. The field site was in its second year of establishment.  Emergence traps for all four treatments, as well as a control, were set at random to collect insects at two week intervals for a total of four sample rounds. At each collection date, vegetation and other microhabitat variables that relate to nesting were recorded. Bees will be pinned and identified to species to compare abundance and diversity of bees in each of the study treatments.
Ground-nesting bee habitat is often overlooked in prairie restoration design, and measuring it could inform seed mix compositions in a way that more adequately serves the wild bee populations they’re designed to protect.