Abstract:

Background & Aims: Overgrazing poses a dominant threat to the biodiversity of most grassland communities. Bees are the primary pollinator group in the grassland ecosystem. Grazing has generally negative effects on bee diversity by affecting floral and nesting resources in grassland communities. However, in communities with long grazing history and reasonable grazing management, grazing may have a positive or neutral impact on bee diversity. Therefore, how grazing affects bee diversity and its role in ecological restoration needs further study.
Progress: In this study, we integrate the recent literature and research practice, and propose that the efficacy of bee restoration can be more accurately assessed through the integration of bee species richness, functional diversity, phylogenetic diversity and full plant-pollinator interaction networks, which provide comprehensive and quantitative information on the structure and function of grassland communities. For grasslands with low degradation, bees can be gradually recovered by effective grazing management, which uses the natural recovery potential of the communities. For grasslands with greater degradation, it is necessary to accelerate the bee restoration through active interventions on the basis of grazing management, such as sowing wildflower species that cannot migrate into the restoration area without assistance and enhancing the availability of nesting habitat for bees. To ensure that bees can obtain enough floral rewards in different flowering periods, the selection and combination of the sown flower species should take into account their roles in the pollination network, floral traits and flowering phenology.
Perspective: It is of great practical significance to investigate the mechanism of bee loss in different types of grasslands in southern and northern China, and to guide the development of targeted ecological restoration strategies for bees.

Key words: grassland, overgrazing, wild bees, pollination network, ecological restoration