城市“源-汇”热景观变化及其空间作用强度特征——以深圳西部地区为例

The“source-sink”thermal landscape change and their interactions across space in urban area:A case study in the western part of Shenzhen City

城市热岛作为一种整体涌现性的地球表层系统环境问题受到地理学和景观生态学的广泛关注,基于空间异质性对城市冷热岛影响方面的研究初步揭示了城市热环境的形成机制,然而城市冷热岛在空间上是否存在相互影响及相互作用强度还有待研究。以深圳市西部城市区为例,应用地表温度和景观分类数据,通过构建二维矩阵识别“源-汇”热景观,并采用“源-汇”热贡献指数和空间引力模型等方法定量分析了城市“源-汇”热景观的演变过程,“源-汇”热贡献程度的时空分异特征,以及两者在空间上的整体相互作用强度及演变特征。结果表明:(1)1988—2019年,城市热源、汇在空间上呈现由包围到反包围的变化,热源景观呈现基质化,其面积增长210.45%;热汇景观则表现为破碎化趋势,其面积减少48.07%。与之对应的热汇景观地表温度与区域的平均温度的温差逐渐增大,从1988年的0.49℃上升到2019年的1.91℃。(2)源、汇对热环境的贡献规模呈增长趋势,热源景观的贡献程度会随着热岛规模从零星状向区域化的转变过程中提升,形成温度聚集效果;而热汇景观的贡献程度会随着冷岛规模的破碎化过程中被抑制。(3)1988—2019年“源-汇”热景观的作用对基本保持稳定,但总作用强度发生了显著的变化,30年间增长了8倍。从热汇景观一对多影响热源景观转变为热源景观一对多影响热汇景观,且作用强度也越来越强。研究发现城市热“源-汇”的空间相互作用强度与“源-汇”热景观的贡献程度有密切关联,因此控制热源景观规模和维护热汇景观规模对调控城市热环境,对提升城市居民生活质量有重要意义。

Urban heat island is an emerging environmental problem worldwide,and has been widely concerned by the interdisciplinary of geography and landscape ecology.Many previous studies have discovered that the impact mechanism of landscape pattern on urban heat/cold island varied across space.However,as far whether the urban hot/cold island has mutual effects and how the intensity of their interaction may change over space remain uncertain.By focusing on the western part of Shenzhen city as the case study area and based on land surface temperature(LST)and landscape types,this study constructed a two-dimensional matrix to identify the source/sink thermal landscape.Then,a contribution index(CI)was used to quantitatively analyze the evolution process of the source/sink thermal landscape.The Gravity Model was used to quantify the intensity of interaction between thermal source landscape and thermal sink landscape during the 1988─2019.The results showed that(1)the urban thermal sink patches originally surrounded by sporadic thermal source patches in 1988 were reversed in 2019.The area of thermal source landscape increased by 210.45%,while the thermal sink landscape showed a fragmentation trend,and decreased in area by 48.07%.The difference between regional average LST and that in thermal sink landscape increased from 0.49℃in 1988 to 1.91℃in 2019.(2)The CI of the thermal“source-sink”landscape had an increasing trend during the past thirty years.In more detail,the CI of thermal source landscape increased when the discrete thermal source patches became spatially more continuous,which aggregated LST.Meanwhile,the CI of thermal sink landscape is inhibited with the fragmentation of thermal sink landscapes.(3)In 1988─2019,the interaction between sources and sink thermal patches was relatively stable.However,the intensity of their interaction quantified by gravity model increased eight times after 30 years.Besides,the linking pattern of source and sink landscape from one sink to many sources changed from one source to many sinks,which led the intensity of link pairs to become stronger and stronger.Overall,our results indicated that the intensity of spatial interaction between urban thermal source-sink landscapes are closely related to the contribution degree of source/sink thermal landscape.Therefore,controlling the size of thermal source landscape and maintaining the size of thermal sink landscape are very important strategic for land policy makers to regulate urban thermal environment.It is also important to improve the quality of life of urban residents.