Effects of ground flowering plant traits on the diversity of wild bees in apple orchards during flowering.

Pollination is one of the important ecosystem services related to sustainable development of human society. However, the population diversity and abundance of wild bees, important pollinators, have been significantly reduced by climate change, agricultural intensification, and landscape transformation. Re-establishment of pollinator habitat by planting nectar-producing plants is an important way to maintain pollination service. In this study, we investigated the status of wild bees and the traits of flowering plants in 22 apple orchards during flowering stage in Changping District, Beijing in 2019. We analyzed the response of wild bee diversity to the flowering plant richness, flower color richness, inflorescence type richness, flowering plant coverage, herbaceous layer coverage and different flower color coverage in apple orchards, aiming to provide guidance for the selection of nectar-producing plants to establish the habitat of wild bees. A total of 3517 wild bees were captured during the apple flowering season, representing 49 species, 13 genera, and 5 families. We identified 21 flowering plants species that shared a similar flo-wering period with apple, exhibiting a range of 5 colors and 9 inflorescence types. The Shannon diversity index, evenness index, and social bee richness of wild bee community were positively correlated with flowering plant richness. The total wild bee community richness, social bee richness, underground nesting bee richness were positively correlated with the richness of flowering plant color, but Halictidae bee abundance was negatively correlated with the richness of flowering plant color. The Shannon diversity index and evenness index of wild bee community were positively correlated with the richness of inflorescence types. Megachilidae bee richness was negative correlated with the white flower coverage. Megachilidae bee richness, social bee abundance, and ground nesting bee richness were positively correlated with the purple flower coverage. There was no significant correlation between wild bees and flowering plant richness, flower color richness, inflorescence type richness, flowering plant coverage, herbaceous layer coverage and different flower color coverage in other communities of different families, lifestyles and nesting types. Maintaining diverse ground flowering plants with various traits in orchards is important to improve the diversity of wild bees. In particular, increasing the coverage of purple flower during apple flowering period is helpful to promote the diversity of Megachilidae bee, social bees, and ground nesting bees.