Forest spatial configuration and local management influence bee pollinator biodiversity in urban and rural landscapes

Forests are crucial for sustainable land planning and they are believed to buffer land use changes and to promote human wellbeing and biodiversity. However, it is not clear how forests could influence bee diversity, that is responsible for the pollination ecosystem service. Here, we investigated bee biodiversity in relation to forests patches in agricultural and urban landscapes, and to urban forest features and flower richness in green areas; we also quantified the amount of pollen transported in relation to nesting and body-size traits. In the results, the importance of landscape variables depended on the macrohabitat: in agricultural lands, bee abundance increased with the number, distance and intermediate cover of forest patches, but in urban environments only forest shape complexity contributed. Moreover, in urban parks with mature urban forests, cavity-nesting bee richness increased with large logs and decaying wood, while bee richness increased with flower species richness in meadows adjacent to forests. Hence, open spaces rich in flowers and forests managed to keep understorey wood are relevant for increasing urban bee richness. Forest management could shape the occurrence of certain bee traits, but the nesting substrate trait will not modify the potential pollination ecosystem service because the amount of pollen transported related more to the body size. This study emphasises the importance of forested areas for bees in agricultural and urban environments. The results could contribute to develop biodiversity-friendly landscape planning and forest management practices when they are focused on ensuring wood elements, flowers and specific forest patch configurations sustaining bees.