Effects of forest management on native bee biodiversity under the tallest trees in the world.

It is not clear if mature secondary growth coniferous forests can support similar pollinator communities as old growth coniferous forests, or how active management (e.g., retention forestry) in mature secondary growth forests may affect pollinator communities. We compare the native bee community and plant-bee interaction networks of old growth, naturally regenerating and actively managed (retention forestry) mature secondary growth forests of similar stand age. Old growth forests had a higher bee species richness and Shannon's diversity index, but not Simpson's diversity index, than both actively managed and naturally regenerating mature secondary forests. Forest type (old-growth, naturally regenerating mature secondary growth, and actively managed mature secondary growth) had a significant effect on bee community composition. Redwood forest bee-plant interaction networks were small in size and had lower complexity than expected and few connector species. While studies suggest that small-scale timber harvest may increase bee biodiversity in the short-term in other coniferous forest habitats, our study suggests that there may be long-term negative effects of clear-cutting that lower bee biodiversity in mature secondary growth forests as compared to mature old-growth forests.