Reducing Overstory in Pacific Northwest Forests Enhances Forage for Bumble Bees Without Increasing Microparasite Prevalence
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Date
2024-08-07
Authors
Fan Brown, Jesse
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Publisher
University of Oregon
Abstract
Bumble bees (Bombus spp.) are the most effective pollinator group in temperate and boreal regions, but habitat loss and disease are contributing to steep declines of several forest-associated species. Forest bumble bees benefit when forest management decreases overstory cover and enhances understory forage plant species, but effects can be short-lived. Forest restoration techniques that prioritize canopy openness may prolong forage availability through later successional stages. Management that increases floral resources may aggregate bumble bee populations and increase disease risk. We examined effects of forest management strategies on understory plant and bumble bee communities and evaluated whether plant and bee community characteristics were correlated with bumble bee disease dynamics. We surveyed the abundance and diversity of flowering plants and bumble bees within stands of varied canopy cover in the Coast Range (n = 98 stands) in Oregon, USA and screened bumble bees for six microparasite taxa (n = 191 bees). We found that canopy openness was positively correlated with flowering plant abundance and diversity and flowering plant communities were positively correlated with bumble bee richness and diversity. Our parasite prevalence rates were comparable to those of other North American bumble bee populations and were not correlated with characteristics of flowering plant or bee communities. Our data suggest that thinning in dense forests can enhance bumble bee habitat without increasing disease prevalence, informing efforts to conserve, restore, and expand forest habitat for imperiled bumble bee species.
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Keywords
bombus, disease, forest management, pollinators, restoration, thinning