Progress report for LNC19-420
Examining the role of shelterbelts (tree plantings) on early-season honey production and hive growth of honeybees in the North Central Region (NCR). Pollinators, particularly managed honey bees (Apis mellifera), are critical to food production and sustainable agriculture. Annually, $215 billion of global food production is dependent upon honey bee pollination services, indicating the importance of these organisms to global food security. More specifically, honey production is an important revenue source in many communities across the NCR. Despite this economic and ecological importance, honey bees are under threat from many sources including intensified agricultural practices and continued loss of perennial vegetation. As these threats persist, reductions in the temporal availability of food resources, especially in the early growing season, may be reducing honey bee survivorship and limiting honey production.
Our preliminary observations and communications with beekeepers suggest shelterbelts could provide a crucial food source for bees when other resources are scarce. However, research has not evaluated shelterbelts for pollinator use, particularly in the resource-limited early growing season. We will examine the effect of shelterbelts on early-season honey production and bee hive health in North and South Dakota, the top two honey producing states in the United States.
To address this, we will establish honey bee colonies across a gradient of landscapes that vary in the amount of shelterbelts they contain. Our design will simultaneously contrast pollen collection and hive weights (i.e., a proxy for hive growth or health) across these landscapes. We expect to learn how shelterbelts can benefit bees, which could change both shelterbelt and bee management. Additionally, we will identify trees and shrubs that provide food resources for bees. This will help guide United States Department of Agriculture (USDA) and Soil Conservation Districts (SCDs) across the NCR with future shelterbelt plantings that can have multiple ecological and economic benefits. Identifying and encouraging bee-friendly shelterbelts will 1) help create healthy honey bee populations during the early-season, which will 2) produce more of a commodity (honey) for beekeepers and 3) benefit farmers/ranchers by enhancing the pollinator resources (and services) crucial to the overall success and sustainability of their respective industries. Finally, society in general will benefit from this research as many of the honey bees that spend the summer in the region are a vital source of pollinator services for fruits, nuts and vegetables throughout the United States.
- Private landowners interested in pollinators or shelterbelts
- Soil Conservation Districts
- United States Department of Agriculture (Farm Service Agency, Natural Resource Conservation Service)
- Understand how shelterbelt abundance (Objective 1) and composition (Objective 2) boosts honey production and honey bee colony growth
- Increase awareness about pollinators, their ecology, and how shelterbelt management can improve their health (Objective 3)
- Beekeepers will select more productive early-season landscapes and produce a larger honey crop
- SCDs will promote cost-effective flowering trees and shrubs in shelterbelts that benefit pollinators
- Landowners will benefit from greater crop and forage pollination because of future pollinator-friendly shelterbelts
Globally, native and managed pollinators are experiencing broad-scale population declines, causing a reduction in available pollination services (Council et al., 2007; Potts et al., 2010). Pollinators, however, are extremely important for humans both economically and for global food security (Gallai et al., 2009; Klein et al., 2006; Potts et al., 2010).
Since the mid-1900s the U.S. Department of Agriculture has tracked and documented an overall decline in managed European honeybee (Apis mellifera) colonies (Council et al., 2007). Similar to declines in other pollinators, factors including parasites, pests, and pathogens interact, weakening populations (Council et al., 2007; Potts et al., 2010). As the primary commercial pollinator in North America and the most widely used and managed pollinator in the world, declines prohibit the European honeybee population from keeping up with the demand for their pollination services (Aizen & Harder, 2009; Delaplane and Mayer, 2000; Kearns et al., 1998; McGregor, 1976).
In the U.S. annually, honeybee pollination is estimated to be valued between $1.5-18.9 billion (Council et al., 2007). In 2019 alone, 157 million pounds of honey were produced with a honey production value of over $309 million ("U.S. Honey Industry Report - 2019," 2020).
In addition to their importance throughout the US, honeybees are an important species for the Northern Great Plains (NGP) region. After a mass transport of honeybee colonies back to the region in early spring, the Northern Great Plains region hosts about one million honeybee colonies, leading the country in honey production and making honeybee declines particularly concerning (Otto et al., 2016; "U.S. Honey Industry Report - 2019," 2020).
Increasingly, land-use change reduces forage availability for honeybees throughout the year and influences their survivorship (Smart et al., 2016). These changes limit forage and nutrient diversity necessary for honeybee survival, and colony growth (Smart et al., 2016).
One potential solution to lessen future declines in honeybees is to promote forage diversity specifically at times when it is lacking (Decourtye et al., 2010; Dolezal et al., 2019). Early spring floral resources are often limited in grasslands, however, and flowering trees and shrubs could fill this niche and provide crucial resources in a time of need for declining honeybee populations.
Around the world, trees and shrubs have been highly documented as important honeybee resources especially during spring (Brodschneider et al., 2019; Lau et al., 2019; Sponsler et al., 2020). Tree and shrub plantings in the NGP are commonly known as shelterbelts, and were originally planted to provide soil stability and windbreaks, although they provide numerous services for human use (Gardner, 2009; Johnson & Beck, 1988).
The goal of our study is to determine if early flowering trees and shrubs planted in the NGP provide essential resources to fill early-season forage gaps for honeybees.
Apiaries with a greater area of shelterbelts within a 1-mile radius will experience greater colony weight gains relative to colonies belonging to apiaries located in areas with less cover of shelterbelts.
Honeybees will use trees and shrubs associated with shelterbelts as pollen sources to a greater extent early in the growing season relative to other forbs on the landscape.
We conducted research in Central North Dakota near the Central Grasslands Research Extension Center and western North Dakota near the Hettinger Research Extension Center. Bees owned and managed by T2 Honey company began arriving in western North Dakota around mid-May. Bees owned and operated by Browning Honey Company arrived in the central part of the state about 10 days later.
Prior to honeybee arrival, we uploaded potential apiary locations into ArcGIS and overlaid points on a North Dakota Forest Service tree cover layer. We used these data to determine the proportion of trees cover that occurred within a 1-mile radius of each apiary. We than selected apiaries (research sites) at central and western locations that covered a range of tree cover in proximity to apiaries.
To assess the growth of our bee colonies, we fit two colonies per location (apiary) with digital scales. Scale data will be used to determine how colony growth and honey production varies across our shelterbelt gradient. Colony weights are automatically recorded and saved every 15 minutes throughout the duration of our study. Two additional colonies per location were fitted with pollen traps that collect pollen from bees as they returned from foraging. Colonies within apiaries used for research were checked prior to the onset of research to ensure a healthy queen was present. Pollen traps were opened every five days for two consecutive days from mid-May to mid-July while most trees and shrubs were flowering. From mid-July through September, pollen traps were opened at two-week intervals for three-day periods. We labeled collected pollen and froze for future preparation. To prepare pollen samples, we cleaned, dried, and ground 10 g of each sample into a homogenized powder. Following pollen processing, samples are sent to the USGS lab for floral species identification We intend to use pollen collected by the pollen traps to identify and quantify which plant species bees are using across landscapes throughout the season.
We further classified tree rows (clusters of more than 2 individual plants of typically one tree or shrub species) that fell within a one-mile radius of each apiary. Mapping included species types, individual counts, and geographic locations. Following site classification, we conducted weekly drive-by surveys throughout the season at each site. During weekly drive-bys, we categorized tree and shrub rows by average floral resource percent flowering categories. We compiled these data to document species phenology by region and to record nearby tree and shrub composition.
During the 2020 field season (May-September), we monitored 48 colonies at a total of 24 unique sites (apiaries) within North Dakota. There were 15 sites in western ND and 9 sites in central ND.
Our two colonies at each site sometime differed in their hive weights throughout the season (Figure 1). End weights varied between hives, with six sites ending with less weight than they began and five hives with end weights over 200 lbs greater than their starting weights. We are currently working with the scale data to isolate time periods when trees and shrubs were flowering at each location. We plan to assess the impact of tree cover on honeybee production at various distances from apiaries out to 1 mile. Preliminary analyses suggests there may be a relationship between colony weight gain and the area of tree cover within 250 m of apiaries (Figure 2).
Pollen samples from the western apiaries have been shipped to the lab for identification and the pollen from the central apiaries are in the processing stage and will be analyzed and compared to vegetation surveys in the future.
We hired Hailey Keen as the graduate student responsible for this project. We have been learning all about the honeybee industry as a team, through hands-on experience. In addition to Hailey and the rest of the team, we also hired a summer technician who worked closely with the team during research activities.
Educational & Outreach Activities
We provided a synopsis of the project to be published in the ND Department of Agriculture for their Apiary Newsletter.