Unraveling microclimate effects on pollinator foraging and crop yield in lowbush blueberry

Authors: SISK, GARRETT - University Of Pittsburgh; OSTROSKI, ANAIS - University Of Pittsburgh; UNGER, MASON - Pennsylvania State University; DILLARD, TRAVIS - Consultant; HALL, BRUCE - Consultant; Goslee, Sarah; GROZINGER, CHRISTINA - Pennsylvania State University; KHANNA, VIKAS - University Of Pittsburgh; GRAB, HEATHER - Pennsylvania State University

Submitted to: Agriculture, Ecosystems & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/4/2025
Publication Date: 10/15/2025
Citation: Sisk, G., Ostroski, A., Unger, M., Dillard, T., Hall, B., Goslee, S.C., Grozinger, C., Khanna, V., Grab, H. 2025. Unraveling microclimate effects on pollinator foraging and crop yield in lowbush blueberry. Agriculture, Ecosystems & Environment. 392:109734. https://doi.org/10.1016/j.agee.2025.109734.
DOI: https://doi.org/10.1016/j.agee.2025.109734

Interpretive Summary: Many crops, including wild blueberries, depend on wild and honey bees for pollination. If bees do not visit plants evenly, crop yields can be inconsistent across fields, lowering total production, even in agricultural systems like wild blueberry where honey bee hives are placed nearby. Temperature and humidity variations within the field may influence bee foraging. We monitored temperature, humidity, bee visitation, and flower density at 120 sites within a 170-acre blueberry field during the flowering period. Blueberry production and quality were recorded for those sites at harvest. Flower density was the most important determinant of visits: more flowers meant more bees. Wild bee foraging was highest in warmer areas and nearer the field edge, and wild bees were active during a wider range of weather conditions than were honey bees. Understanding the effect of microclimate on pollination can aid in optimal placement of honey bee hives and in management to support wild bees

Technical Abstract: Pollination services provided by wild and managed bees are critical for many nutrient dense and high-value crops worldwide. However, pollinator foraging is not distributed evenly across space and thus may contribute to variability in crop yields. Here we evaluate how microclimate and distance from forest edge and from managed honey bee hives influence fine-scale foraging by both wild and honey bees and correlate to lowbush blueberry yields. Topographic variation resulted in microclimates with differences of as much as 10°C and 29% relative humidity across the study area. Honey bees were the predominant visitors, and we found no evidence for competition with wild bees. Wild bee visitation was positively correlated with honey bee visitation and wild bee visits did not vary with distance from honey bee hives. Both groups had substantial temporal and microclimatic overlap in their foraging profiles, though wild bees foraged earlier and at a wider range of conditions. Wild bee foraging was greater in warmer than average areas and declined with distance to forest edge. The effect of microclimate on wild bee foraging was similar in magnitude to the effect of forest edge distance and both were weaker than the effect of average flower density. Flower density, which was greater in sites with warmer microclimates, was the primary driver of foraging for both wild bees and honey bees as well as yields. After accounting for differences in flower density, no relationship was observed between either wild or honey bee visitation rates and blueberry yields, suggesting that pollination services were not limiting yield in the study area. Our findings indicate that microclimates within fields can have stronger effects on crop yield than other well recognized factors, mediated by their effects on floral density and bee foraging. Given higher microclimatic variability at higher temperatures, as well as the links between microclimate, flower density, and wild bee foraging, our findings suggest an avenue by which climate change will impact within-field yield variability.