Within-Year Effects of Prescribed Fire on Bumble Bees (Hymenoptera: Apidae) and Floral Resources

Abstract

Despite the importance of bumble bees (genus Bombus Latreille) for their services to natural and agricultural environments, we know little about the relationship between grassland management practices and bumble bee conservation. Prescribed fire is a common grassland maintenance tool, including in areas where endangered and threatened bumble bees are present. Thus, knowledge of the effects of prescribed fire on bumble bees is essential for designing management schemes that protect and bolster their populations. Using nonlethal surveys to record bumble bee species richness, abundance, and community composition, we evaluated the effects of spring controlled burns on summer bumble bee gynes and workers across five sites in southern Wisconsin. In addition, we explored the effects of fire on floral resources by measuring floral genus richness, abundance, ground cover, and proportion of transects containing blooming flowers in adjacent burned and unburned parcels. Prescribed fire had no measurable effects on bumble bee gyne or worker community composition, species richness, or abundance. However, consistent with previous studies prescribed fire increased floral genus richness and ground cover. The disconnect between bumble bee and floral responses to fire highlights some opportunities for improving our understanding of fire's effects on bumble bee diapause, nest site choice, and foraging.