Comparison of early seral forest bee communities following clearcutting or wildfire depends on stand age and nesting guild

Forest harvesting can create habitat for wild bees (Hymenoptera: Anthophila), but with potentially different characteristics from habitats created by natural disturbance such as wildfire. We evaluated how bee communities varied between stands regenerated by stand-replacing wildfire or intensively managed stands regenerated by clearcut harvest up to 20 years post-disturbance, using a chronosequence design in southwest Oregon. We also compared bee communities supported by post-fire salvage logging, 6–9 years post-disturbance. Clearcut stands supported higher bee abundance (90% CI: 36, 255%) and species richness (90% CI: 24.6, 44.8%) than fire-origin stands initially, but lower abundance (90% CI: –21, –71%) and species richness (90% CI: –51.4, –66.5%) in the oldest stands. Solitary nesting species associated with dead wood (mostly Osmia spp.) were more abundant in fire-origin stands. Our results indicate that clearcut harvest creates habitat for most wild bees adapted to stand-replacing fire but compromises habitat longevity and limits dead wood nesting habitat.

Our results indicate that intensive forest management may be compatible with supporting the pool of wild bee species that occur in response to stand-replacing wildfire, except for species reliant on dead wood. Greater retention of downed dead wood may help alleviate these differences. Wild bee habitat within regenerating stands lasted longer following wildfire disturbance than clearcutting with intensive forest management. Therefore, retaining broadleaf vegetation likely prolongs bee habitat but may trade off with bee abundance during stand initiation. It is also possible that the large total extent of regenerating stands in some managed landscapes offsets shorter habitat longevity for bees.