Progress report for GNC20-297
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. The proposed research will assess how forest management can improve apple pollination by increasing wild bee functional diversity at the landscape level. We will use 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 are to: (1) Determine how forest management practices, through their influence on forest structural complexity, affect wild bee functional diversity on forest lands; (2) determine which wild bee functional groups are present in apple orchards; compare those wild bee functional groups 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 will collect 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 will quantify forest structural complexity using a variety of metrics calculated from LiDAR point clouds. We will then relate these measures to wild bee functional diversity within forests. Throughout the project we will work alongside apple and peach farmers, private forest landowners, and employees at the Illinois Department of Natural Resources (IDNR) and the University of Illinois Forestry Extension. We will provide surveys, workshops, and reports so that understanding of wild bees, pollination, and the relationship between forest management and crop pollination is shared effectively with all stakeholders and collaborators.
Learning and action outcomes will target the following stakeholders: apple and peach farmers, landowners with forested lands on their property, and employees at the Department of Natural Resources, The University of Illinois Forestry Extension, and Shawnee National Forest. This project will first elucidate how forest management affects wild bees, and that information will be shared with all property owners that we work with and those implementing forest management plans on private and public property. In doing so, forest management practices that enhance bee diversity can be encouraged in southern Illinois. This project will also elucidate which forest management practices are most effective for surrounding apple and peach pollination and why these practices affect pollinators. This knowledge is imperative for apple and peach farmers because there is a clear lack of understanding how forest management affects pollinator diversity. With this knowledge, there is potential to manage lands with the goal of enhancing pollination services to crops like apple and peaches to increase seed set. 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 will provide a foundation for increasing forest management on public lands with co-benefits to surrounding agricultural lands.
Field work was conducted in southern Illinois in Jackson and Union Counties. In total we sampled 42 100m2 plots. There were 29 forest plots, distributed across three public land sites: Lake Murphsyboro State Park (N=9), Trail of Tears State Forest (N=12), and Giant City State Park (N=8). Forest plots were comprised of three treatments: Burn (N=4), Thin (N=4), Burn+Thin (N=12). In addition to these treatments, there were 9 control plots (three at each site). Alongside the forest plots, we sampled 13 apple orchard plots at three privately-owned apple orchards: Flamm Orchards (N=6), Rendleman Orchards (N=6), and Lipe Orchards (N=1). The plot at Lipe Orchards was later dropped due to site differences, but results will still be relayed and communicated with the owner (Sara Lipe).
Our first year of field work was conducted in 2021, and we will have another year of field work starting in the spring of 2022. Sampling did not occur in 2020 due to the pandemic. In 2021, data was collected in three separate sampling rounds: March/April - early spring (during apple blooms), May - late spring/early summer, and July/August - summer. Each sampling round lasted approximately two weeks. In the early spring round, we sampled both apple orchard and forest plots. Only forest plots were sampled in the two consecutive rounds of sampling. We collected wild bee specimens along with various plot-level environmental and abiotic variables.
Wild bee sampling:
We collected wild bees using both active and passive sampling methods. Sampling only occurred when temperatures were above 60 degrees Fahrenheit and conditions were mostly clear with sunny skies. We visited plots twice in one day. During the first visit, we distributed blue, yellow, and white pan traps (N=15) and arranged them in two, perpendicular lines. These traps were filled with soapy water, and left in a plot for two hours. Upon returning to a plot for the second visit, we drained the traps and stored any collected bee specimens in plastic bags. We then actively sampled for bees using nets and stopwatches. We divided the plot into four equal quadrats, and sampled each quadrat for 5 minutes (20 minutes total). During active sampling, we paused the stopwatch once a bee was netted. We then placed the bee into a cyanide tube and started the stopwatch once the net was free to collect another bee. Once we concluded sampling for the day, bees were processed that night. Bees from pan traps were washed with ethanol, dried with a blow dryer and tea strainer, and pinned and labeled. Netted bees were pinned and labeled directly. We then stored all specimens in boxes for later identification.
In addition to wild bees, we collected plant species data (forest and apple orchard plots), soil temperature and moisture measurements (forest plots only), canopy cover (forest plots only), DBH measurements (forest plots only), stem count measurements (forest plots only), and bee nesting resource data (forest plots only). We identified all blooming plants to the species level, and recorded the number of individual flowers on each plant. For bee nesting resources, we estimated the amount of bare ground in a plot, number of holes in the ground, presence of woody debris, and number of snail shells.
We are still in the process of identifying the bee specimens we collected in 2021. We therefore do not have full results to share from 2021 sampling. Below are combined wild bee abundance totals from each treatment: Burn, Thin, Burn+Thin, Apple Orchards, and Control plots.
|Burn||Thin||Burn+Thin||Apple Orchards||Control - Forest|