Effects of logging on pollinator communities, habitat, and plant-pollinator interactions in coniferous forests

Global declines of bees and other flying insects threaten the delivery of pollination services in wild and managed ecosystems. Effective pollinator conservation in forested landscapes is emerging as a critical issue for protecting biodiversity and ecosystem function. Many US National Forests have now included desired conditions and goals for maintaining and restoring pollinator habitat in their revised forest plans. However, successful management is hindered by a lack of information about how common forest management practices, such as logging, affect pollinator abundance and diversity, pollinator habitat, and plant-pollinator interactions.

We surveyed 8 logged and 8 control sites in a coniferous forest in Montana, USA in 2023 and 2024. We hypothesized that logged sites have higher plant and pollinator diversity, and more complex plant-pollinator interaction networks. We measured foraging and nesting habitat and collected all observed insect floral visitors, identifying all flowers and insects to species level. We found that plant community composition and floral diversity differed significantly between treatments, although total plant abundance and species richness (including forbs, grasses, and woody plants) did not. Pollinator diversity, as well as frequency and diversity of plant-pollinator interactions were higher in the logged sites. These results indicate that common management treatments can benefit pollinator habitat and diversity in forested landscapes. Ongoing research will include environmental DNA analysis of insect-collected pollen and trace insect DNA from flowers to construct plant-pollinator networks, enabling non-destructive measurement of plant-pollinator interactions and pollinator diversity.