Multi-scale drivers of wild bee communities in vineyard agroecosystems

CONTEXT Wild bees face multiple, interacting stressors in agricultural landscapes. Effective bee conservation requires understanding the spatial scales that influence bee communities to better inform policies and programs. OBJECTIVE This study examined how wild bee communities respond to local farm-management practices and surrounding land-use and soil variables in vineyard-dominated landscapes. METHODS Bees and local vegetation and floral resources were sampled in 26 commercial vineyards employing varying management practices in the Niagara Region of Canada over two growing seasons. Surrounding land use, soil texture, and slope were quantified within a 300 m radius of each site. Generalized Linear Models (GLMs) were used to assess relationships between local and landscape variables and bee abundance and diversity. Non-metric multidimensional scaling was used to evaluate associations among bee community composition, functional traits, and environmental variables. Additional GLMs were conducted for above- and below-ground nesting bees due to strong associations between nesting traits and community composition. RESULTS AND CONCLUSIONS Wild bee communities were influenced by both local and landscape-scale variables. Locally, greater between-row vegetation height was positively associated with higher bee abundance and diversity. At the landscape scale, higher proportions of surrounding semi-natural land, primarily treed habitats, were associated with increased bee abundance and diversity. Bee community composition varied among sites in relation to both local and landscape factors, associated with multiple bee functional traits including nesting strategy, sociality, sex, and body size. Underground-nesting bee abundance was positively associated with coarser soil textures while both above- and below-ground nesting bees were positively associated with semi-natural land cover. SIGNIFICANCE Supporting abundant and diverse wild bee communities in agricultural landscapes requires consideration of both on-farm management practices and the surrounding landscape context. More research is needed on nesting habitat requirements in agricultural landscapes across bee taxa. • Local, farm management and surrounding landscape factors influence vineyard bees. • Bee abundance and diversity were positively associated with semi-natural lands. • Taller between-row vegetation enhanced bee abundance and diversity. • Soil texture and slope are linked to bee nesting traits.