Evaluating remnant vegetation management practices adjacent to apple orchards to support native bee pollinators

Maintenance of a diverse pollinator community helps ensure resilience in pollination services. Fragments of woody and grassy vegetation in the vicinity of croplands have been shown to encourage the presence of crop-pollinating bees. However, to date, little attention has been given to the management practices that may enhance the presence of bees in such fragments. We investigated how the maintenance of remnant forest fragments adjacent to apple orchards in South Australia affects floral resources and native bee communities. The fragments had been subject to either (a) fire (assessments three years post-burn), (b) cattle grazing under trees and (c) low maintenance management (>20 years not grazed or burnt). Plant communities were sampled along transects in plots. Bee communities were sampled using hand netting. We fitted generalised linear mixed models to investigate differences in plant and bee diversity between treatments and to elucidate the effect of plant diversity on bee diversity. We compared plant and bee community composition among treatments using non-metric multidimensional scaling and conducted network analysis to measure the robustness of plant-pollinator interactions to the removal of species. Both floral resource abundance and bee diversity were higher in burnt and low-maintenance fragments than in grazed fragments. Bee species richness was positively associated with plant species richness. The species richness of bees that visit apple flowers was positively associated with flower abundance but not with floral species richness. Plant-pollinator networks in grazed sites had fewer links per species and a higher proportion of realised links than those under other management practices. However, the resilience of pollinator networks did not differ significantly between management practices. Thus, controlled burns or low-maintenance management of forest fragments appear to be the most suitable landscape management practices to support apple pollinating bees. Burning requires consideration of additional ecological consequences, such as the conservation of fire-sensitive species and specialist woodland fauna. Cattle grazing adjacent to orchards results in simplified bee communities and pollination networks and is not recommended if pollination services are required for adjacent land uses. This information can benefit orchardist as well as managers of fragments of native vegetation adjacent to orchard crops.