AUTHORS: Vera Pfeiffer*, Janet Silbernagel, Christelle Guedot, Juan Zalapa – University of Wisconsin- Madison
ABSTRACT: Native pollinators provide an important ecosystem service for many pollination-dependent fruit crops and wild bees require nesting and foraging resources in proximity to target crop plants. Consequently, landscape resources influence the distribution of pollination services, which may fluctuate temporally through the season due to pollinators’ foraging preferences. This study investigates how floral resources and landscape context influence bumble bee colony density and fluctuation between the growing season and the target crop pulse. We sampled bumble bees at fourteen cranberry marshes before, during, and after the cranberry bloom in central Wisconsin. Two sites supplemented wild bumble bees with commercial colonies, which were separately analyzed. Floral richness and surrounding land cover were quantified and their effects on individual and colony density were assessed using linear regression models and variance partitioning. The percentage of forest or cultivated land best predicted individual and colony density during almost all temporal extents. The interspersion of meadow through the surrounding landscape and the total bog edge were also useful in top regression models. Floral richness was the primary factor influencing individual density during bloom, as well as the change in colony density between the growing season and the bloom when change accounts for detection. Landscapes with large agricultural field sizes and very clumpy forest experienced a decrease in colony detection probability, and likely colony dependence during bloom. We suggest that maintaining forested land and interspersed meadow around cultivated fruit crops is important for colony abundance, and bolstering floral richness locally will draw in more bees when floral resources are abundant.
