Department of Landscape Architecture, School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai, China.
Key Laboratory of Urban Agriculture (South) Ministry of Agriculture, Shanghai Jiao Tong University, Shanghai, China.
PLoS One. 2018 Apr 25;13(4):e0196445. doi: 10.1371/journal.pone.0196445. eCollection 2018.
Mitigating extreme heat in urban areas is beneficial and sometimes critical to human health. Thriving plant communities in community parks play an important role in mitigating extreme heat through providing cooling effect, while inevitably affecting how people perceive the benefits of using community parks for recreation. Thus, the impacts of plant communities on the thermal environment should be quantified to determine the optimal structure of the plant community. The goal would be to harmonize the functions of improving the thermal environment with the preferences people have related to the recreational benefits of plant communities with various levels of vegetation density. In this paper, the correlations between the structural characteristics of plant communities and their function in mitigating the thermal environment were investigated on calm summer days in Xincheng Central Park, Minhang District, Shanghai, China. In addition to analyzing the plant communities present and their effects on the park microclimate, a questionnaire was employed to determine the plant community preferences of recreational park users. The results showed that plant communities could reduce the air temperature by 1.23-2.42 °C and increase the relative humidity by 2.4-4.2% during the daytime. The microclimate conditions in plant communities with varying vegetation densities were significantly different. The canopy density and leaf area index primarily controlled the temperature reduction, while the canopy density and total canopy cover ratio primarily controlled the increase in humidity; meanwhile, these correlations varied at different times of the day. Moreover, most of the park users preferred a moderately dense plant community which met their environmental perceptions for recreation in parks. Age or education level variables of park users would also predict preferences for different plant community densities. Ultimately, one plant community pattern with appropriate canopy density (60%), leaf area index (≥3) and canopy cover ratio (total 0.80-1.20, with 0.6-0.75 for trees and 0.20-0.45 for shrubs/woodland area) was recommended, which would harmonize the functions of the mitigation of the thermal environment with most people's perception of a desirable vegetation density.
在城市地区缓解极端高温对人类健康有益，有时甚至至关重要。社区公园中繁茂的植物群落通过提供降温效果，在缓解极端高温方面发挥着重要作用，同时不可避免地影响人们对使用社区公园进行娱乐的好处的感知。因此，应该量化植物群落对热环境的影响，以确定植物群落的最佳结构。目标是协调改善热环境的功能与人们对不同植被密度的植物群落的娱乐效益的偏好。本文在中国上海闵行区莘城中央公园宁静的夏日，研究了植物群落的结构特征与其缓解热环境功能之间的相关性。除了分析现有的植物群落及其对公园小气候的影响外，还采用问卷调查来确定娱乐公园使用者对植物群落的偏好。结果表明，植物群落可以在白天将空气温度降低 1.23-2.42°C，并将相对湿度提高 2.4-4.2%。不同植被密度的植物群落的微气候条件有显著差异。冠层密度和叶面积指数主要控制降温效果，而冠层密度和总冠层覆盖比主要控制湿度增加；同时，这些相关性在一天的不同时间变化。此外，大多数公园使用者更喜欢满足他们在公园娱乐时环境感知的中等密度植物群落。公园使用者的年龄或教育水平变量也会预测对不同植物群落密度的偏好。最终，推荐使用具有适当冠层密度（60%）、叶面积指数（≥3）和冠层覆盖比（总 0.80-1.20，其中树木为 0.6-0.75，灌木/林地为 0.20-0.45）的一种植物群落模式，这将协调缓解热环境的功能与大多数人对理想植被密度的感知。
