城市绿地演化轨迹与变化研究——以上海市外环以内区域为例

Evolution and change of an urban greenspace:A case study on the outer ring of Shanghai

城市绿地是城市绿化系统和城市景观的重要组成部分,具有重要的生态、社会、心理和经济功能.作为城市绿地研究的重要组成部分,城市绿地的演化轨迹与变化规律的研究对维持城市绿地系统的稳定性和优化城市生态网络具有重要的意义.传统的大部分绿地变化研究多采用景观指数和空间分析等方法,难以反映出绿地斑块的变化过程、变化类型及空间分布规律.本研究首先定义了7种城市绿地演化类型,分别为连续、扩张、收缩、消失、新增、合并和分解,以此为基础构建出以绿地斑块为节点、以绿地演化类型为边的绿地演化图.以上海市外环以内区域作为研究区域,基于绿地演化图对2008年、2012年和2016年的绿地演化过程进行了提取和三维可视化,并分析了城市绿地变化过程及城市绿地全局变化的空间分布规律.研究结果表明:上海市外环以内的绿地变化以新增与消失两种变化类型最为突出.其中新增的城市绿地斑块空间分布较为均匀,新增的小斑块多分布于中心区域,而新增的大斑块多位于边缘区域.消失的绿地出现在非中心位置的较多,而且浦东新区外环以内的区域占比最多.与2008—2012年的城市绿地变化相比,2012—2016年新增绿地的空间分布更加均匀,消失绿地的位置分布更加集中.

Urban greenspace is an important part of the urban green system and urban landscape,with important ecological,social,psychological,and economic functions.The evolutionary trajectories and change patterns of urban greenspaces are of great significance to the sustainable development of urban green space systems and the optimization of the urban ecological network.There is ongoing emphasis on urban greenspace research;most previous research studies on greenspace changes have used landscape indices and spatial analysis methods,which struggle to accurately reflect the change process,change types,and spatial distribution patterns of greenspace.In our paper,seven types of greenspace evolution were defined,including continuous,expansion,contraction,dissipation,creation,merging,and splitting.Then,an evolution graph was constructed by defining greenspace patches as nodes and greenspace evolution relations as edges.Based on the greenspace evolution graph,the greenspace evolution process and its corresponding evolutionary trajectory were further extracted and visualized.Taking the Shanghai city center as a case study area,the spatial distribution pattern and change process of the urban greenspace for 2008,2012,and 2016 were extracted.Results indicated that the most dominant greenspace evolution types were creation and dissipation.The newly added urban greenspace patches were more evenly distributed compared with those patches involved with an evolution type of dissipation.Small patches were more likely to be located in the urban center,while large patches tended to be concentrated in rural areas.The location of greenspace patches that disappeared were mostly concentrated in non-central areas,particularly in the Pudong New Area.Compared with the urban greenspace changes between 2008 and 2012,locations where new greenspace appeared between 2012 and 2016 were more evenly distributed,while locations where greenspace disappeared were more concentrated.