Improving apple and peach pollination by advancing knowledge of how forest management affects wild bee functional diversity

View the project final report

Commodities

• Fruits: apples

Practices

• Crop Production: forestry, forest/woodlot management, pollination, pollinator health

Improving apple and peach pollination by advancing knowledge of how forest management affects wild bee functional diversity

Agricultural systems worldwide are dependent on bee pollination. With continued pollinator declines, it is imperative that we manage landscapes in ways that both conserve and promote pollinators. Land management operations rarely assess ecosystem services (i.e. pollination), and the diversity of pollinators is crucial to successfully pollinate crops. We assessed how forest management can improve apple pollination by increasing wild bee functional diversity at the landscape level. We used a forest-agriculture interface in southern Illinois to evaluate this relationship because these two ecosystems have the potential to increase a wide diversity of pollinators (specifically wild bees) due to their contrasting environments and floral resources. Our specific objectives were to: (1) Determine how forest management practices, through their influence on forest structural complexity, affect wild bee functional diversity on forest lands; (2) compare wild bee composition in apple orchards to managed forest lands; and (3) advance stakeholder knowledge (apple and peach farmers and forest landowners) about promoting wild bee pollination with management through workshops that engage local resource managers and local landowners.

To explore the relationship between forest management, wild bee functional diversity, and apple pollination, we collected wild bee specimens in both forest sites on public lands and on nearby apple farms. In order to measure vertical canopy heterogeneity, which can affect pollinator communities, we quantified forest structural complexity using a variety of metrics calculated from LiDAR point clouds. We then related these measures to wild bee diversity within forests. Throughout the project we worked alongside apple and peach farmers and employees at the Illinois Department of Natural Resources (IDNR) and the University of Illinois Forestry Extension. 

We found that bee functional composition varied with forest management type, and that different bee functional traits aligned with different management strategies (including no management). Unmanaged habitat provides critical nesting resources to bees that otherwise might not exist within managed habitat. Given these findings, a diversity of management strategies is needed to support a functionally diverse bee community. We also determined which structural metrics derived from LiDAR point cloud data were most useful in predicting bee diversity and abundance within managed forests. Structural metrics in the understory, as well as overall vegetation density, were most predictive of spring bee diversity and abundance. Structural metrics in the midstory were most predictive of summer bee diversity and abundance. Midstory vegetation density had consistently negative relationships with summer bee diversity and abundance. Although we were only able to collect one year of data for the apple pollination portion of the project, we were able to determine that bee composition significantly varied between apple orchards and all forest management strategies. More research is needed to determine which forest management strategies increase pollination services to apple orchards. 

Land managers at the IDNR will be using our data and findings when considering future management decisions. Reference collections are being provided to all public land sites used in the study (Giant City State Park, Trail of Tears State Forest, and Lake Murphysboro State Park). Displays showcasing bee specimens will be set up at select visitor centers within these sites so that employees and the public are aware of the diversity of wild bees in temperate deciduous forests and how management can affect their populations.

Learning and action outcomes targeted the following stakeholders: apple and peach farmers, landowners with forested lands on their property, and employees at the Department of Natural Resources, and The University of Illinois Forestry Extension. This project first elucidated how forest management affects wild bees, and that information was and will be shared with those implementing forest management plans on private and public property. In doing so, forest management practices that enhance bee diversity will be encouraged in southern Illinois. In the long-term, all stakeholders will understand the value of forest management in relation to pollinators and agriculture, learn about wild bees, and either be able to implement forest management strategies on their forest lands that are pollinator friendly or potentially increase pollination to their apple and peach orchards. Results provide a foundation for increasing forest management on public lands with co-benefits to surrounding agricultural lands.