长沙城市斑块湿地资源的时空演变

Spatial-temporal changes of urban patch wetlands Changsha,China

利用GIS技术,对长沙市1955、1972和1990年地形图湿地数据及2007年长沙市湿地资源普查数据进行提取和分析,选取最具代表性的斑块湿地作为研究对象,从时间与空间、动态与静态、规模与填埋等视角,研究50年来城市斑块湿地生态系统各层次要素的时空演变过程和变化规律。结果表明:(1)时间层次上,长沙城市斑块湿地总面积呈现先增后减、总体增加的态势;斑块湿地面积变化幅度不断加大,速率逐步加快;(2)规模层次上,面积在32 hm2规模以下的斑块湿地呈增加态势,32 hm2规模以上斑块湿地呈减少态势;(3)动态空间层次上,被填埋斑块湿地的比例在建成区和郊区呈相反的演变结果;(4)静态空间层次上,斑块湿地密度在建成区范围和郊区范围演变结果相背。研究显示,伴随着城市化进程,不同时间尺度、不同规模尺度、不同空间属性、不同空间状态的城市斑块湿地常常呈现差异很大、甚至是截然相反的演变结果;无论是动态空间还是静态空间,建成区与郊区的空间分界线往往是城市斑块湿地演变态势的分水岭。

Wetland is one of the important ecosystems providing various ecological goods and services to human well-being However, in urban areas, owing to rapid economic development and urban expansion to be converting to other land uses, including resident houses, transportation Understanding the spatial-temporal changing information for wetland conservation and patterns of urban wetland and their , wetlands are encountering a threaten facilities, and industrial buildings. driving forces could provide valuable urban planning toward sustainable development Characterized by typical hilly area and subtropical monsoon climate, Changsha has abundant wetland resources. The changes in wetland area in Changsha the urban wetland data in Changsha city represent the common phenomena in were derived from topographical maps in south-central cities of China. In this study, 1955, 1972 and 1990, and remote sensing image in 2007 by using the GIS tool. Then, we selected the most representative patch wetlands as our study objectives. From the viewpoints of the time and space, dynamics and static, we investigated and analyzed the dynamics and variations of elements and spatial characteristics in urban patch wetlands ecosystem during last five decades. The result indicated that total areas of urban patch wetlands in Changsha has been increased from 1955 thorough 1972 to 1990, but then decreased from 1990 to 2007. The general tendency during the last five decades exhibited an increased process. The variation amplitude of urban patch wetland area in Changsha continued to be increased and the change rategradually speeded up. In terms of wetland size, the area of patch wetland smaller than 32ha has increased while the area of wetland larger than 32 ha showed a reversed tendency. Whether in the downtown or the suburb area, the density of urban patch wetland has been increased. The number of the reconstructed patch wetland and the remained patch wetland per land area has been increased in both the downtown and the suburb area. The ratio of reconstructed to remained patch wetland showed reversed change tendency in the downtown and the suburb area. The number of patch wetland per land area decreased in the downtown area. Our results suggested that no matter how differences in temporal scales, spatial attribute and spatial state, urban patch wetland often appear to be different and even opposite change patterns along with city expansion. In either dynamic or static space, the boundaries between downtown area and suburbs were key area of changes in urban patch wetlands. Overall, we found three key factors that mainly determined the changes in urban patch wetlands in Changsha. The first one was the size of patch wetland, with area smaller than 8 ha constituting more than 60% the total patch wetland; The second was the land use policy and urban construction, which resulted in the decline in patch wetland in the last decade; The third was location or area in the city, with increase of wetland in suburb area and decline of wetland in downtown. However, the direct relationships among these three factors mentioned above and changes in patch wetlands, as well as the effects of other natural factors （ such as climate change） are not well understood and will be the further research topics.