In spring 2017, 2018, and 2019, I employed novel canopy-sampling methods using elevated “bee bowl” traps at 11 sites in NY state. I caught wild bee pollinators in the canopy and understory of woodlots adjacent to pollination-dependent fruit trees. Woodlots were dominated by wind-pollinated tree species, and more than half of captured bees were known apple pollinators (Russo et al. 2015, Blitzer et al. 2016). Canopy bees were highly abundant during tree bloom, and rapidly declined after, supporting the idea that bees were foraging.
Here, I propose three research objectives investigating (1) bee abundance and activity in forest canopies, with analysis of the evolutionary relationships and life history diversity of the forest bees (2) the relationship between forest and orchard habitats for male and female bees at different times of year and (3) a comparison of nutritional resource quality and pesticide exposure for bees visiting forest-canopy and orchard blooms.
(1) I am using taxonomic guides, expert support, and DNA barcoding to identify the wild bee species found in the canopy, understory, and adjacent orchards. Many commonly found forest bees are poorly known and thus hard to identify due to underdeveloped taxonomic resources. This is especially true for groups such as mining bee males; the females of this group of bees are highly effective pollinators, so understanding the behavior and foraging choices of males is crucial.
(2) I am using microscopy to identify the pollen from guts of trap-caught wild pollinators. Traps demonstrated immense diversity of canopy-foraging bees, but not which trees the bees preferred. Pollen identification through microscopy will provide detailed tree pollen use by the wild pollinating bees. I ask if bees are foraging on wind-pollinated forest canopy trees in early spring, which would support more direct action for forest management for bees. I also hypothesize that pollen preferences vary over space, time, and the gradient of forest cover in the surrounding landscape. Note that this microscopy method is change in approach, adjusted with the goal of answering the same ecological questions but with more detail (discussion of change in methods sections).
(3) I will quantify the pollen quality and quantity of important forest and hedgerow trees with metrics relevant to bee health. To estimate pollen quantity, I will improve estimates of flower abundance for trees and shrubs in an in-development floral resource database for the Finger Lakes region of NY (Iverson et al. unpublished data), then combine these data with per-flower estimates pollen abundance. The only available pollen quality data is missing many local species and provides only protein content (Roulston et al. 2000), while protein:lipid ratio of pollen is most important for pollinator choice (Vaudo et al. 2016a, 2016b). I thus propose to collect and calculate protein:lipid ratios for the common wind- and insect-pollinated forest trees and compare these with apple pollen in adjacent orchards. I will ask if the preferred trees identified in objective (2) also have the highest quality or quantity pollen. I will quantify pesticide residues in the pollen of forest and hedgerow trees. Using pollen from trees collected 100-500m from the orchard, I will analyze pollen samples for 41 compounds commonly applied in our landscape at the Cornell Chemical Ecology Core Facilities, through the McArt lab. I will calculate toxicity estimates based on the literature and compare wild tree pollen toxicity relative to apple pollen.
The purpose of this project is to identify the forest, woodlot, and hedgerow tree species that are most important for supporting fruit tree pollinators. While much research has focused on herbaceous wildflower plantings for pollination services in agricultural crops (Blaauw and Isaacs 2012, 2014, Grass et al. 2016), almost nothing is known about how forest and shrub resources support pollinator populations and effect pollination services. This is a surprising gap in knowledge since forests and forest fragments commonly surround orchards in the Northeastern US, and the resources they provide may be critical for robust pollinator populations. For example, our own data from flower counts taken in spring 2017 found the number of flowers on a single canopy maple or oak tree often exceed 600,000 or even 700,000 blooms/tree. A single male red maple can present up to 1350 flowers/m 3 of the outer 2 meters of canopy, which translates to an estimated 1.35 ml nectar/m 3 (Batra 1985). This exceptional resource likely contributes to findings that natural forest habitat and plant diversity support thriving pollinator populations in apple orchards in the northeast (Park et al. 2015, Kammerer et al. 2016), yet these patterns have never been measured directly, nor is the contribution of specific tree and shrub resources known.
Of the 416 species of wild bees in New York State, over 120 species have been found visiting apple orchards (Russo et al. 2015, Blitzer et al. 2016) . Wild bees emerge after spring thaw immediately requiring pollen and nectar, and forests are among the only available forage resources (Chambers 1968, Russo et al. 2013) . Since the orchards they pollinate will not bloom for several weeks, bees require other resources to stay active until crops bloom, and to amass sufficient resources to reproduce to maintain healthy populations each year (Schellhorn et al. 2015) . While spring ephemerals certainly provide pollen and nectar and are the focus of much research (Motten 1986, Williams and Winfree 2013, Parker et al. 2016, Austen Emily J. et al. 2018) , they pale in comparison to the sheer number of flowers in the canopy. Although their nutritional quality has never been investigated, many scattered literature observations suggest wind-pollinated trees are visited by diverse bee species (Chambers 1968, Raw 1974, Russo and Danforth 2017) .
A healthy wild bee population reduces the need to rent honey bee hives and provides pollination services in poor weather and unpredictable climates (Blitzer et al. 2016) . Biodiverse pollinator populations are insurance against climate change, pests, and diseases, as bees with different traits respond differently to climate pressures (Bartomeus et al. 2013) , so species diversity supports economic security in the form of a successful crop each year (Aizen and Harder 2009, Garibaldi et al. 2013) . It will thus directly inform land management for fruit tree pollination services and thus crop viability to identify the preferred tree species and the quantity and quality of pollen they produce for a maximally diverse bee population.
The value of pollination services in NY State is estimated at $500 million/year for crops including apples, pumpkins, and strawberries (New York State Departments of Environmental Conservation and Agriculture & Markets. 2016) . Pollination is crucial for human diets, including a high proportion of nutrient dense foods (Eilers et al. 2011) . Yet, the average loss rate for honey bee hives in the U.S. in 2014-2015 was 49.0% (Seitz et al. 2015) . Orchardists are struggling to find honey bee hives to rent for pollination services, (personal communication to Scott McArt from Jeff Morris, Glenora Farms, Dundee NY), and rentals have risen to $140/hive on average in recent years (Wheeler et al. 2018). Wild bees increase pollination services regardless of honey bee abundance (Winfree et al. 2007, Garibaldi et al. 2013) , and are important pollinators in New York apple orchards (Blitzer et
al. 2016) . There is also widespread cultural interest and knowledge around managing for wild bees. A recent survey of over 600 orchardists in New York and Pennsylvania found that 93% of respondents highly valued wild pollinators, and sought to actively manage their land for wild bee conservation (Park et al. 2018) . Some orchardists are now choosing to rely entirely on wild bee services (Dunn 2018) .
Wild bees often suffer from nesting habitat and forage loss associated with land-use change and agricultural intensification (Steffan-Dewenter Ingolf et al. 2002, Carvell et al. 2006) . Wildflower plantings, a frequently suggested solution, can increase wild bee abundance, diversity, and pollination services (Blaauw and Isaacs 2014) , yet such strips require expensive establishment and are often overtaken by weeds requiring herbicide management (Landis and Savoie 2018) . In contrast, once established, perennial trees and shrubs provide resources to bees in addition to long-term benefits such as soil stabilization, wind breaks, carbon sequestration, timber, firewood, shade for animals, and even maple syrup or nuts (Farming the Woods 2014, Graham and Nassauer 2017) . Thus, identifying the forest and hedgerow species which provide food to bees could successfully maximize ecological services and increase not just fruit pollination but whole-farm ecological and economic sustainability (Bommarco et al. 2013)(Potts et al. 2016) .
There is a growing call for basic research into insect use of wind-pollinated resources, a large portion of which are early-blooming trees (Saunders 2018) . Their pollen-releasing catkins are not showy or colorful, so not traditionally understood as attractive to bees and thus ignored in forest resource calculations. Yet several “wind-pollinated” species are in fact used extensively by bees and partially pollinated by insects, including willow (Peeters and Totland 1999) , several maples (Sullivan 1983, Batra 1985) , linden (Anderson 1976) , and others. Scattered historic data suggest that bees frequently collect from wind-pollinated oak, ash, beech, and birch (Chambers 1968, Raw 1974) . Thus, to understand how to select forest and hedgerow trees to support pollinators, we must re-evaluate the importance of these less-showy resources. Therefore, I propose here to calculate the use patterns and quality of this resource for the broad community of wild bees in order to fill this knowledge gap.
Since last winter’s report, I completed my third and final spring sampling of forest & orchard bees. In 2017, 2018, and 2019 respectively I sampled in 6, 11 and 9 different forest-orchard pairs across the Finger Lakes region of New York State. Prior to receiving the SARE grant, I worked with each of the growers to confirm sampling goals and areas and completed two seasons of bee sampling. To set up, I used a “Big Shot” 7-ft slingshot to launch a weight attached to a thin rope. In five trees per forest, I aimed precisely for a branch or branching fork that would allow for sampling at the edge of the canopy tree. Once positioned correctly, I then reeled a bee trap into the canopy, and installed a paired trap at ground level. These traps were “bee bowl” cups in standardized fluorescent yellow, white and blue, each color of which is known to attract a different suite of bee species. Together the three bowls comprise a standard bee sampling method. Five similar tri-color traps were deployed in adjacent orchards in the branches of apple trees. Bees were collected weekly from each trap at all sites and placed directly into small Whirlpak bags with 95% Ethanol for later processing. Sampling began each spring immediately after winter thaw and continuing one week after apples finished blooming across all sites (each year, roughly first week of April-first week of June).
Objective (1) was first to finalize bee abundance and activity in forest canopies, with analysis of the evolutionary relationships and life history diversity of the forest bees. Each bee was pinned and individual labels with “QR” barcodes were generated for databasing and accessioning into Cornell’s permanent insect collections. Bees have nearly all been identified and are in the process of being databased. A lack of previous research on this bee community meant that there was a lack of identification resources, particularly for the Andrena mining bee males –a highly efficient pollinator. As a result, we are complementing microscopic identification with molecular barcoding. This has created an exciting and unexpected project, and we expect to advance the resources and primer pairs available for bee identification using a streamlined protocol. One undergraduate mentorship (Anna Espinoza) in molecular taxonomy has emerged from this project, and a collaboration with a post-doc and now professor at McGill University (Jessica Gillung), and we hope will become a side publication focused on the rapid protocol and correct primer sets for molecular identification of a regional fauna, particularly when one sex of the species is less resolved. This technique was crucial for positive identification of all species and to allow us to address the subsequent ecological questions.
Objective (2) is to use pollen analyses to characterize the relationship between forest and orchard habitats for male and female bees at different times of year and, and to so I am in the process of identifying the pollen collected by each bee species. This will allow us to understand which tree species in the early spring forest are most important for wild bee pollinators. In the first step towards this answer, an undergraduate mentee and I dissected each of the bees collected in 2018, which had been collected into 95% Ethanol. Bees were surface sterilized so no contaminant pollen was collected. Dissection was done carefully to remove only the internal guts, but not damage the structure of the bee’s external integument, so that they might still be identified to species under the microscope. All guts were immediately placed into individually labeled tubes and placed in the -80C freezer, to maintain them for future identification via molecular (or microscopy) methods. The original method for this pollen identification was to use pollen meta-barcoding, a molecular approach to identify the full community of pollen in a sample (in this case, in a wild bee’s digestive tract). However, since the time of funding, several new papers have demonstrated discrepancies in the ability of this method to accurately quantify the amount of different pollens, and bias depending on the relative abundances in the original sample. This could make it impossible for me to know if bees were actually using significant amounts of certain species of trees that might amplify in their gut samples, or if there were simply contamination or otherwise negligible amounts of those pollens in their digestive tracts. Thus, upon careful reflection, my advisors and I have adjusted my allocation of funds to ensure that I am accurately & thoroughly able to answer the ecological questions here funded. Using DNA barcoding instead for the wild bee identification allows for a highly accurate and cutting-edge approach to characterizing this relatively-unknown insect community, while moving to microscopy from meta-barcoding for the pollen samples allows for accurate insight into relative resource use. This is very important, as I am seeking to particularly identify resources that have been overlooked in the past.
Objective (3) investigates the nutritional resource quality and pesticide exposure for bees visiting forest-canopy and orchard blooms. During these field seasons, I have collected branches from 18 common tree species in local woodlots, and collected all pollen that dropped from these blooms after they dehisced in order to obtain a pure sample of each. These samples will be analyzed for protein & lipid contents and screened for pesticide content at the Cornell Pesticide Core Facility this spring.
For quantity estimates, I am collaborating with Prof. Aaron Iverson to estimate blooms/tree for all common tree species in regional woodlots, while taking into account variables such as tree age and canopy position. I am collecting flowers to calculate the amount of pollen / anther, anthers / flower. These numbers will allow us to understand the bee-relevant diet quality in the context of the availability of those resources on the landscape.
Background Data & Important Ecological Correlates
Schematic preliminary graphs characterizing the forest composition (measured with variable radius plots using an angle gage, BAF 10) and light levels (measured with a hand-held densiometer; superimposed bloom windows estimated to represent dates compiled across sites).
OBJECTIVE (1) Forest bee community characteristics
Bees were most abundant in early spring in the understory and the canopy of forests, and a few weeks later were more abundant in adjacent apple orchards. After this last field season, I am able to present roughly similar patterns for all three years for bees in forest canopies, understories, and adjacent apple orchards. The abundance peaks seem to roughly correspond to active bloom times.
I am similarly in the process of measuring the downed wood (coarse woody debris, or CWD) and standing dead wood. The below protocol provides a site-level measurement of CWD; these data are nearing completion. I will use this measurement to ask if there is a relationship between the amount of coarse woody debris and the abundance & diversity of known wood- and cavity-nesting bees in forest habitat. This will have direct implications for how farmers may choose to manage the downed wood in their nearby woodlots.
Figure below: The abundance of bees caught in the forest canopy was not significantly different from that of the bees caught in the understory (that is, bees were similarly abundant–highly abundant–in the canopy!).
However, males and females were not equally abundant in the canopy and understory (figure below). Females were significantly more abundant in the canopy than the understory. This may be due to differences in foraging activity: I hypothesize that females are more abundant in the canopy because they are foraging more heavily on canopy trees, while males may be spending more time near nests on the ground waiting for mating opportunities. Pollen identification (Objective 2) will provide support for or refute this hypothesis.
A goal of this project is also to compare the forest canopy with the bees in the orchard. To illustrate the “habitat sharing” of a species that is found both in forests and orchards, the graphic below compares 10 years of apple orchard bee species data to the bee species caught in the forest canopy just 1 year (2017, itself a very rainy spring with low bee activity)! Many of these species were found in both apple and orchard habitats (shared species represented by dark green circles). We expect this number only to increase as we finish the 2018 bee species identifications and further future sampling.
The most common groups of bees were sweat bees, “green bees,” small carpenter bees, and ground nesting mining bees, who include the most effective orchard pollinators on a per-visit basis. Nearly all genera were found in both the canopy and the orchard in 2018, although some species do prefer one or the other habitat. Also, in some cases, the male of a species is predominantly found in the canopy, while the female is found in the orchard. Our future work will investigate which trees all of these groups are visiting for pollen resources.
OBJECTIVE (2) Gut Pollen Dissections & Pollen Identification for Diet Characterization.
In 2018 and 2019 respectively, we caught 499 and 621 Andrena (male bees 59 and 53%), the important pollinators commonly called mining bees. Following gut dissections in both 2018 and 2019, I found that male mining bees were more abundant in the forest than in the orchard, and females were most abundant in the canopy, followed by the orchard (all contrasts p = <0.001). Male and female adult bees caught in apple orchards and canopies were more likely to have pollen meals in their digestive tracts (p = <0.001). This suggests that the canopy catches may indeed be due to foraging in those treetops. In 2019, 158 out of 328 (48%) of male Andrena had pollen in their digestive tracts.
A surprising finding that warrants further study was that of all male Andrena with pollen in their guts, 25% of those with pollen had gymnosperm-type pollen (that is, coniferous). These distinctive grains were highly abundant, suggesting that bees were either consuming them intentionally or otherwise spending sufficient time in conifers that accidental consumption was common. This pattern warrants further investigation in future research.
All gut pollen samples have been plated for microscopic identification, and will be identified by me and undergraduate mentees over the next months.
OBJECTIVE (3) Quantity and Quality of Forest Tree Pollen
I have preliminary counts of the absolute amount of pollen produced by 10 of our most common forest trees. For example, two Red Maple trees had 9,400 and 15,600 flowers, while two canopy red maples respectively had 157,100 and 132,800 flowers. Red maple flowers had an average of 10 anthers per flower, for a range of 94,000 to 1,571,000 anthers per tree of these four counted trees. In a silver maple, two trees had 17,800 and 510,100 flowers per tree, 19 anthers per flower for a range of 338,200 to 9,691,900 anthers per tree, and an average of 2330 pollen grains per anther, for a total estimate of 788,006,000 to 22,582,127,000 (~800 million to ~22 trillion) pollen grains per tree. I will continue to finalize these number and compare them to apple tree estimates, and then multiply these out by landscape scale abundance of trees to understand landscape scale estimates.
I have also been successful in collecting pollen in volume from the common forest trees & apple trees in my study sites, in preparation for quality analysis (protein & lipid) and risk (suite of pesticides, analyzed by Cornell’s core pesticide facility) analysis later this summer. I have sufficient pollen for pesticide analysis for six common wind-pollinated regional trees (alder, quaking aspen, silver maple, white birch, box elder, red oak, and black oak), which requires a very large pollen quantity. I have sufficient pollen for protein:lipid analysis for an additional seven species, for a total of 13 local species. This longer list includes apple and several ornamental and insect-pollinated forest trees for comparison with the wind-pollinated forest species. My goal for this spring’s field work includes finalizing the collections of these volumes.
Education & Outreach Activities and Participation Summary
2019 Insectapalooza "wild bee trivia" scavenger hunt fact sheet for interactive bee display;
2019 PolliNation podcast guest with host Andony Melathopolous;
Outreach days at 2019 Empire Farm Days pollinator outreach tables
March 2019: I was invited to give a talk at the 4th Biennial Forest Landowners Conference: Working Woods for Today and Tomorrow. My talk was titled “Bees in the Trees: Biodiverse Pollinators in the Early Spring Flowering Forest Canopy,” and 60 people attended. There was a lively discussion afterwards.
May 2019: I visited with Autumn Stoscheck & Ezra Sherman at their cidery, one of my research sites in Van Etten, NY. Their synopsis and a video me discussing my research can be found at https://www.evescidery.com/pollination/
July 2019: I was invited to host a two-day workshop at the Yale School of Forestry for an undergraduate summer field biology course hosted by Yale Forestry Professor Marlyse DuGuid; this will involve several interactive lessons, field day for bee observations and collection, sample processing & insect pinning lesson, and bee identification and construction of “interaction networks” of field plants and pollinators.
I also gave a seminar at the Yale Myers Forest for their weekly “quiet corner initiative” summer research symposium (typical audience: ~60 rural landowners and Yale Forestry students in the northeast corner of CT).
August 2019: I helped continue our annual tradition of participating in wild bee outreach at Empire Farm Days, the largest Farm Expo in New York State! Despite the rain, we spoke with many families.
October 2019: I was featured on the PolliNation Podcast! It was great fun to talk with Andony Melathopolous. The podcast has a listenership of 400. http://blogs.oregonstate.edu/pollinationpodcast/2019/10/06/113-kass-urban-mead-bees-in-trees/
December 2019: Following a conversation with NYFOA members at Empire Farm Days, I was invited to write an article for the New York Forest Owner’s journal, titled “Wild Bees Amidst the Trees.” It included several considerations for forest owners on managing forests for bee biodiversity. It has been published and is currently being mailed out to all forest landowning subscribers (Forest Owners website: www.nyfoa.org) .
September 2020: I was invited to be one of 8 speakers at the 2020 Cleveland Pollinator and Native Plant Symposium, after the organizers heard my PolliNation podcast. There were 225 attendees at the 2019 symposium; www.clevelandpollinatorsymposium.org.
I hope that this project will contribute to future sustainability by directly integrating pollinator conservation into agroforestry, silvopasture, and small-farm woodlot and hedgerow management. This will be particularly relevant for apple orchards, the focal commodity of our lab’s research. However, many crops and wild plants benefit from or entirely rely on ecosystem services provided by free-living pollinators.
I am eager to continue working with growers, researchers, and community members to answer these exciting questions about the role of woodlots and forests in wild pollinator conservation. I am committed to sharing the knowledge I gain through careful research and collaboration.
In my future career, I hope to work at the intersection of extension and teaching, either through non-profit government or a joint extension/teaching faculty position. This current SARE project is deepening my natural history knowledge in the context of working agricultural lands, and should generate concrete outcomes in terms of being able to recommend woodlot and hedgerow management for pollinator conservation. Given the importance of trees for soil stabilization, wind breaks, carbon sequestration, forage, and numerous other sustainability benefits, I am particularly excited to find myself poised at the cusp of integrating pollinator conservation with these efforts.