Promoting Native Bee Health and Pollination Services on Diversified Organic Produce Famis

• Determine if habitat augmentation expedites the development of abundant, diverse, and stable native bee communities (Objective 1):
  • Sub-objective 1a: Establish habitat augmentation treatments on farms

In 2015 we established nesting structures on one half of our participating farms. These nesting structures each contained 400 cardboard tubes to be used by cavity-nesting bees, with 50 tubes of each of 8 sizes. This diversity of tube size could promote cavity nesting bees of varying size. Due to logistical constraints, we did not complete our habitat installations until 2016, which consisted of floral strips and patches of bare ground on each participating farm, in addition to the nesting structures that were established in 2015. Thus, the impacts of these treatments may take several additional years to manifest. Funding from SARE was essential to establish these treatments, and we have leveraged SARE funding to continue to project through 2018 to maintain these treatments and fully measure their impacts on bee communities.

• Sub-objective 1b: Sample native bee communities

In 2014, 2015, and 2016, we sampled the native bee communities on each farm three times per year (May, July, September) using the methods described earlier. From 2014 and 2015, we collected a total of over 7,200 individual bee specimens across our farming network. We expect to collect similar numbers of bees from 2016, although these bees are still in the process of being sorted and pinned in our collection. All of our specimens will be maintained in the Crowder lab for long-term preservation. The bees collected to date represent specimens from at least 20 distinct genera, representing a wide diversity of form and function. We have common social species, such as honey bees and bumble bees, as well as a myriad of cavity-nesting species (which form nests in twigs and small branches, and which may benefit most from nesting structures) and ground-nesting species (which may benefit most from bare ground). The distribution of bees collected to date is shown in (Figure 8). We also found that the abundance and diversity of bees varied greatly based on the time of collection (Figure 9 and Figure 10)

• Sub-objective 1c: Measure the effects of habitat augmentation and landscape intensity

The use of cavity-nesting structures installed at the 34 urban gardens and farms, during 2014 and 2015 indicate that native bees will occupy a diversity of nest substrate, and that this substrate also provides habitat for a suite of three native bee genera, which may contain approximately a dozen species (Figure 11). Yet, these data, when paired with our trapping data fail to indicate that nesting-structures like these increase bee biodiversity and abundance in our farmer’s fields. Although, farmers with a history of previous cavity-nesting bee management had significantly more cavity-nesting bees occupy nesting-structures installed at the margins of their farms (Figure 12). Data on the impact of our other habitat augmentation practices (floral strips and bare ground) may be revealed in our 2016 sampling data, which are still being processed (it is highly labor intensive to identify all bees to genera, and the samples won't be identified until the end of 2016). Moreover, it may take several years for the impacts of these augmentation methods to fully manifest. However, we were able to leverage SARE funding to obtain additional funding for this project, which will allow us to fully monitor the bee communities through 2018 and gain a better understanding of how augmentation practices affected the bee communities.

Our results do indicate that landscape intensification had significant impacts on bee communities. While the diversity of bee communities did not differ significantly between urban and rural farms (Figure 13), the abundance of bees was significantly lower on urban farms (Figure 14). Moreover, these trends persisted in each part of the year where sampling was conducted (Figure 15). Thus, we hypothesize that bee communities in urban areas will ultimately benefit most from habitat augmentation practices.

• Measure the impact of habitat augmentation on pollination services (Objective 2):
  • Sub-objective 2a: Assess pollination services on farms

In 2016 we measured pollination services on all our farms using sentinel strawberry plants. Strawberries were grown in the greenhouse and were regularly trimmed of flowers before being taken out to the field (to prevent fruit set before taking them to the field). In August and September we took plants of the same age, with at least six open flowers to the field. These plants were assigned to one of three treatments (hand pollinated - control), open pollinated (able to be pollinated by bees on our farms), or caged (unable to be pollinated by bees). These three treatments allowed us to explore whether bee communities provide significant pollination services to farms. After 72 hours in the field the plants were brought back to the greenhouse and allowed to continue to grow to measure fruit set. This work will continue in 2017 and 2018 as habitat treatments continue to exert effects on the bee communities.

• • Sub-objective 2b: Explore the effects of habitat augmentation and landscape intensity on fruit set and pollination services

At the time of this report the plants have not yet been harvested and thus we can't determine whether our habitat augmentation treatments increased pollination services. We did observe that bees were critical for strawberry pollination, as plants in the cages treatments had misshapen and poorly set fruit.

Our measurement of bee visitation did provide some insight into the effects of landscape intensity on pollination services. Across farms in urban and rural locations, particular bee groups tended to visit the same flowering plant groups with similar intensity (Figure 16). Thus, we can infer that landscape intensity did not affect the innate foraging preferences of bee groups. While lower abundance of bees in urban areas might diminish pollination services, we do not anticipate that bees change their foraging patterns based on landscape context.

• Educate farmers and engage community members on native bee conservation (Objective 3):
  • Sub-objective 3a: Conduct field days to educate farmers about conserving native bees and pollination services

Farmers who participated in field days indicated their continued willingness to monitor bees outside of the field day programs. Moreover, these same participants gave critical quantitative and qualitative feedback that allowed us to improve our content over the course of the project (Figure 17). Additional analysis is needed to determine the full suite of perceptions organic farmers allotted to the field day experiences.

• Sub-objective 3b: Establish citizen science initiative on bee conservation

To-date, we have hosted 13 citizen science classes, and registered greater than 70 citizen scientists on our website. These citizen scientists have added an addition 8 sampling sites to our bee biodiversity monitoring network (Figure 18), and an additional 7 sites to our research on cavity-nesting bees (Figure 19).