Wild bee response to forest management varies seasonally and is mediated by resource availability

Abstract

In many temperate, deciduous forests, long-term management suppression has led to mesophication (cool, damp, and shaded conditions), resulting in habitat with homogenous composition and structure. Management approaches that emulate historical disturbance regimes (e.g., prescribed fire and thinning) have the potential to restore habitat heterogeneity, but effects on biodiversity remain poorly understood, especially for insects. Specifically, the ramifications of forest management practices for beneficial insects such as bees are unclear and rarely considered in management outcomes. Furthermore, the majority of bee studies in temperate, deciduous forests and do not consider how seasonality and management may interact to affect bee composition. To address these knowledge gaps, we sampled bees across spring and summer for two years in 28 plots comprised of non-treated control plots and three different treatment types (burn-only, thin-only, and the combination of both (thin-burn)). Our overall objective was to determine how bee communities respond to forest management and identify the primary predictors of community composition and structure. We found that bee communities varied across management types, with more intensely managed plots (thin-burn) consistently having the highest bee diversity and abundance. On average, more intensely managed plots had three times as many bees in comparison to control plots. Comparing spring to summer, we found that different resources predicted bee diversity and abundance. Most notably, floral resources predicted bee diversity in spring, while in summer, management type, as well as floral and nesting resources were most important. Surprisingly, deadwood did not predict bee diversity and abundance despite being a critical nesting resource. Overall, our results suggest that forest management practices that emulate historical disturbance regimes can affect bee communities, with more intense management enhancing abundance and diversity.