Long-Term Impacts of Fire Severity on the Diversity of Cavity-Nesting Bees and Wasps

Bees are essential pollinators and vital to ecosystem function, and thus it is important to understand how fire impacts bee communities and diversity. Human activities are changing fire regimes, which impact the resources upon which bees depend, such as nesting material and floral resources. Fire’s impacts on bee communities vary depending on the time since the fire and fire severity. However, the majority of previous research has examined the impact of relatively recent fires on bee diversity (<5 years post-burn). We addressed this gap in research by examining the impacts of fire on bee diversity over 20 years post-burn.

We selected 18 sites, which varied in burn severity (high burn, low burn, and no burn). We used trap nests to test if fire severity affected cavity nesting bees’ abundance and diversity. We made trap nests using bamboo reeds of varying sizes and installed them at two different heights at each of the 18 sites. Cavity nesting bees and wasps used caps to plug the reeds in the trap nests, which we used to identify the occupants. We assessed the effects of burn severity on cavity-nesting bee and wasp diversity by comparing the richness and abundance. Our initial findings did not show any statistically significant results, but we will overwinter the nests in the lab and identify the species as they emerge, which may impact our results. Our study will help us to improve our understanding of the long-term impacts of fire severity on pollinator diversity.