State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No. 18 Shuangqing Road, Beijing 100085, China.
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No. 18 Shuangqing Road, Beijing 100085, China; University of Chinese Academy of Sciences, No. 19A Yuquan Road, Beijing 100049, China; Beijing Urban Ecosystem Research Station, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No. 18 Shuangqing Road, Beijing 100085, China; Beijing JingJinJi Urban Megaregion National Observation and Research Station for Eco-Environmental Change, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No. 18 Shuangqing Road, Beijing 100085, China; Xiongan Institute of Innovation, Xiongan New Area, 071000, China.
Sci Total Environ. 2023 Mar 15;864:160929. doi: 10.1016/j.scitotenv.2022.160929. Epub 2022 Dec 20.
Increasing urban tree canopy (UTC) has been widely recognized as an effective means for urban heat mitigation and adaptation. While numerous studies have shown that both percent cover of UTC and its spatial configuration can significantly affect urban temperature, the pathways governing these relationships are largely unexplored. Here we present a cross-city comparison aiming to fill this gap by explicitly quantifying the pathways on which percent cover of UTC and its spatial configuration affect land surface temperature (LST) using structural equation modeling (SEM), based on UTC mapped from high resolution imagery and LST derived from Landsat thermal bands. We found: 1) Although both the direct and indirect pathways significantly affected LST regardless of scales and cities, the direct pathway played a more important role in affecting LST in Baltimore, Beijing, and Shenzhen. In contrast, an opposite result was found in Sacramento, likely due to the effects of buildings and their interactions with UTC. 2) Similarly, the direct pathway of mean patch size (MPS) and mean shape index (MSI) played a more important role in affecting LST than their indirect effects via altering edge density (ED). Our results highlighted the necessity for discomposing the effects of different spatial configuration variables on LST. Understanding the pathways through which UTC affects LST can provide insights into urban heat mitigation and adaptation.
增加城市树冠覆盖率（UTC）已被广泛认为是缓解和适应城市热岛效应的有效手段。虽然许多研究表明，UTC 的百分比覆盖和其空间配置都可以显著影响城市温度，但这些关系的作用途径在很大程度上仍未得到探索。本研究通过结构方程模型（SEM），基于高分辨率图像中映射的 UTC 和 Landsat 热波段衍生的 LST，明确量化了 UTC 百分比覆盖及其空间配置影响 LST 的途径，从而进行了跨城市比较，旨在填补这一空白。结果表明：1）尽管无论在何种尺度和城市，直接和间接途径都显著影响 LST，但在巴尔的摩、北京和深圳，直接途径对 LST 的影响更为重要。相比之下，萨克拉门托的结果则相反，这可能是由于建筑物及其与 UTC 的相互作用的影响。2）同样，平均斑块大小（MPS）和平均形状指数（MSI）的直接途径对 LST 的影响比通过改变边缘密度（ED）的间接途径更为重要。本研究结果强调了需要分解不同空间配置变量对 LST 的影响。理解 UTC 影响 LST 的途径可以为城市热缓解和适应提供启示。
