Diversity patterns and composition of wild bee communities (Hymenoptera: Anthophila) in Swedish boreal forests under different management regimes

Abstract: Intensive forest management has led to forest homogenization with associated changes to biodiversity. Compensatory actions have been taken to counteract the negative effects of these practices on biodiversity, but the effectiveness of these actions depends both on which scale they are evaluated and the group of species they are addressed to. In Sweden, the state-owned forest company Sveaskog has developed landscape restoration projects called ecoparks to create multipurpose forests which combine production, recreation and enhancement of natural values. Previously, little research has been done on wild bee communities (Hymenoptera: Anthophila) in boreal forests. With a functional and multi-scale approach, this study aims to figure out whether and how different management regimes affect diversity patterns of wild bee communities. The study also investigates if there are differences in species and functional composition between these management regimes. A pair of landscapes consisting of an ecopark and a conventionally managed production landscape were selected in the south and north of Sweden. Bees were sampled during three years in open and sun-exposed plots where local environmental variables were measured. The percentage of open areas surrounding each plot at different scales was also extracted. Results showed no differences in diversity patterns nor in composition or functionality of wild bee communities between management regimes. Instead, there were differences (except in functional composition) between southern and northern regions. There was higher alpha diversity in the north and higher gamma diversity in the south. The northern region had a higher local functional diversity than the southern one. Functional diversity was, in general, positively related to deadwood diversity but when analysing the data by regions, just the southern one was significantly related to deadwood diversity. The latter relationship might be explained by the diversity of the dataset in terms of species functionality. Despite the little time elapsed since the beginning of restoration, this study suggests that landscape could be playing an important role in the assemble of wild bee communities and highlights the potential of using a functional approach when assessing the effects of different management regimes on wild bee communities.