城市热岛效应与景观格局关联分析：城市化响应及阈值判定

The scope and intensity of urban heat islands in China are continuing increasing along with the process of fast urbanization. The change of landscape patterns has been regarded as the direct driving force of urban heat island. However, it is also recognized that there are distinct differences for the influences of city size, landscape composition and spatial configuration on urban heat island effect among various urbanization stages, and the influencing thresholds identification is not focused. In this project, cities at prefecture or higher levels in China, with a special focus on such large cities as Beijing, Shenzhen, Wuhan, and Chengdu, are selected as study areas. With the application of remote sensing observation, and GIS analysis, the main contents of this project are to contrast spatiotemporal correlations between city size and urban heat island effect, to identify the response of the correlation between landscape composition and urban heat island effect to the process of urbanization, and to determine the contribution of spatial configuration to urban heat island effect. Therefore, the aims of the project are to comprehensively clear up spatial differentiation mechanism of the correlation between landscape patterns and urban heat island effect under different urbanization processes, and to put forward the thresholds of city size, landscape composition and spatial configuration in moderating urban heat island effect. The project is regarded to be of great scientific and practical significance, which will help to deeper the understanding of mutual feedbacks between pattern and process in landscape ecology, to broaden the theory and methodology of urban landscape ecology, and to put forward the landscape approach in improving urban adaptation ability to climate change.

随着城市化进程的快速推进，全国城市热岛的范围与强度不断加大。景观格局改变被视为城市热岛形成的直接原因，但城市规模、景观组分、空间构型对热岛效应的影响在不同城市化阶段差异显著，且缺乏二者关联阈值判定。因此，本项目分别以全国地级及以上城市和北京、深圳、武汉、成都等重点大城市为研究区，综合应用遥感观测、GIS分析等技术手段，对比城市规模与热岛效应的时空关联特征，明晰景观组分与热岛效应关联的城市化响应，厘定空间构型驱动热岛效应的贡献率，从而系统揭示不同城市化进程下城市热岛效应与景观格局关联异同的形成机理，提出缓解城市热岛效应的规模、组分、构型等景观格局要素城市化响应阈值。本项目研究有助于深化景观生态学格局与过程互馈的科学认知、丰富城市景观生态学理论与方法、明晰城市适应气候变化能力提升的景观途径，具有重要的科学与实践意义。

全球气候变暖和快速城市化背景下，城区温度显著高于周围郊区气温的现象，即城市热岛效应，已成为城市生态学的热点研究议题。作为导致地表温度改变的主要原因，城市景观格局的时空分异特征决定了城市热岛效应的强度差异；厘清城市热岛效应与景观格局的关联机理及响应阈值，能够为城市热岛效应缓解提供核心科学依据。本项目重点关注城市规模与热岛效应时空关联、景观组分与空间构型响应城市热岛效应的非线性特征及关键阈值。主要研究成果包括：（1）城市规模与热岛效应关联的时空对比。城市规模超过特定阈值后，对热岛效应产生稳定的正向驱动作用；城市规模对热岛强度的作用阈值受地形、水热条件、经济发展等条件影响显著，在全国体现为西南<西北<东北<中原<华北<东南的地区差异；（2）景观组分、空间构型对城市热岛效应的驱动机理。研究发现景观面积对地表温度的贡献远高于空间构型，其中灰色景观面积对地表温度的影响大于绿色景观面积；绿色景观形态类构型对地表温度的影响大于灰色景观构型并具有尺度效应；绿色景观因子和高反照度因子对地表温度空间异质性的解释率最高，水体景观组分和构型因子均与地表温度呈现弱相关关系，解释作用较为微弱；（3）城市热岛效应缓解的景观途径。相较于最大影响视角，累积影响视角评估城市公园降温效应能够加强对降温效应空间异质性的动态认知；深圳市公园周长达到13283m，面积至429ha后最大降温范围不会随着城市公园面积周长变大而增加；珠三角低、中、高城市化水平下水体景观样本对应的最优斑块规模阈值分别为0.74ha、0.63ha和0.90ha，即随着城市化水平的上升呈现先下降后升高的趋势。未来将重点研究面向景观格局缓解城市热岛效应的降温网络构建，以期进一步服务中国新型城镇化战略目标下的城市气候变化适应能力提升。