Effects of Plant Communities in Urban Green Spaces on Microclimate and Thermal Comfort

Urban green spaces are crucial for regulating microclimates and enhancing human comfort. The study, conducted at Jiyang College of Zhejiang A&F University, investigates the effects of plant communities with diverse canopy structures on campus microclimates and thermal comfort in summer and winter. Data on air temperature (AT), relative humidity (RH), wind speed (WS), and light intensity (LI) were collected over three consecutive sunny days in both summer and winter. Concurrently, plant community structural characteristics, including three-dimensional green biomass (3DGB), canopy density (CD), and sky-view factor (SVF), were measured and analyzed. Quantitative relationships between these plant characteristics and microclimate/thermal comfort indices were evaluated using statistical analyses. The results indicate that, in summer, plant communities produced significant cooling (daily average AT reduced by 2.3 degrees C) and humidifying effects, and decreased the daily maximum thermal humidity index (THI) by 1 degrees C compared to control areas without vegetation. In winter, the moderation of temperature and humidity was present but less pronounced, and no statistically significant temperature difference was observed. Communities with larger 3DGB, higher CD, and lower SVF provided more effective shading and improved microclimatic regulation. A regression analysis identified AT as the primary factor influencing outdoor thermal comfort across both seasons. Planting configurations such as "Tree-Shrub-Herb" and "Tree-Small Tree", as well as the use of broad-crowned shade trees, were shown to be effective in optimizing microclimate and outdoor comfort. Overall, enhancing the vegetation structure may address outdoor thermal comfort requirements in campus environments throughout the year.