Fuels reduction thinning positively influences native bees, but not blooming plants, in a mixed coniferous forest

Abstract

Progressively more intense and frequent forest fires in western North America have led to higher demand for active fuels management activities. The most common method to manage fuel loads in western forests is fuels reduction thinning. Concurrently, growing evidence highlights the importance of forests as valuable habitat for native bees. However, the effects of fuels reduction thinning on bees are not well understood in the Pacific Northwest (PNW), United States. We examined how thinning affected native blooming plant and bee communities by conducting a before-after, control-impact (BACI) study across four years (2020–2023) and 24 sites in a northeastern Oregon coniferous forest. We sampled bees using passive traps and hand nets, counted blooming plants along transects, measured groundcover and bare ground, and estimated elk (Cervus canadensis) herbivory from GPS collars twice per year. Throughout our study we counted 42,209 blooms of 101 species and collected 11,880 bees of 166 species. Thinning decreased canopy cover and increased woody debris. Thinning also increased, though not significantly, elk herbivory. Although blooming plants were not significantly affected by thinning, bee abundance, richness, and diversity increased in thinned sites. Thinning also changed bee community composition, with increases in wood and soil nesting bees but no change in cavity nester abundance. Blooming plant responses may have been moderated by increased elk herbivory in thinned sites. Our findings suggest fuels reduction thinning in PNW forests may have positive effects on native bees, with bee responses apparently initially driven by changes in nesting habitat rather than in floral resources.

Citation

Mitchell, Scott R.; DeBano, Sandra J.; Rowland, Mary M.; Burrows, Skyler. 2026. Fuels reduction thinning positively influences native bees, but not blooming plants, in a mixed coniferous forest. Forest Ecology and Management. 617: 123896. https://doi.org/10.1016/j.foreco.2026.123896.