扬州市湿地景观格局演变及驱动力研究

以扬州市2002年、2007年、2013年的遥感影像为数据源,通过解译获得了扬州市湿地资源分布图,运用转移矩阵法及景观格局指数法对2002-2013年间扬州市湿地动态变化及景观格局演变进行分析,并利用主成分分析法对其驱动力进行探究。结果表明,扬州市2002-2013年湿地面积呈逐年下降趋势,2007年比2002年减少13.69 km2,降幅1.1%;2013年比2007年减少43.23 km2,降幅3.3%。2013年与2002年相比,河流面积稍有减少,降幅为5.6%;滩地面积增加73.2%;库塘面积所占比重由49.84%上升到55.37%,面积增加6.2%;湖泊面积降幅29.7%,所占比重由32.83%下降到24.14%。2002、2007、2013年,各湿地斑块所占景观面积比均为库塘>湖泊>河流>滩地。景观格局指数分析表明,湖泊、滩地及库塘呈现不同程度的破碎化,而河流湿地斑块形状趋于规则且连通性较好。扬州市湿地景观整体呈破碎化趋势,湿地斑块形状趋于复杂,景观多样性增加,各类型湿地呈均衡化趋势发展。社会经济发展、人口增加、第二产业比重及降雨量变化是导致湿地景观格局变化的主要驱动力。

Evolution of the Wetland Landscape Pattern and Its Driving Forces in Yangzhou

A key component of the urban ecological infrastructure, urban wetlands offer important ecological services including water resource conservation, climate regulation and water purification. Yangzhou City is located in the intersection of Yangtze River basin and Huaihe River basin, with a complex river network and abundant wetland resources. The rich wetland resources support good wildlife habitat and support aquaculture, bringing ecological, economic and social benefits to the people of Yangzhou. However, the rapid urbanization and population growth have caused excessive exploitation of urban wetland resources in Yangzhou, accompanied by loss of wetland area, wetland landscape fragmentation and the degradation of wetland function. It is therefore important to document the changes and explore the driving forces to provide scientific evidence for the protection of wetland resources and the development of an ecological city. In this paper, remote sensing images for the years 2002, 2007 and 2013 were used as the primary data sources and the spatial distribution of wetlands in Yangzhou were determined by interpreting the images. The transition matrix method and landscape metrics were combined to quantify the dynamic changes of wetland landscape pattern from 2002 to 2013. Additionally, the primary driving factors for wetland landscape changes were diagnosed through principal component analysis. The results indicate that the area of the wetlands in Yangzhou decreased year by year from 2002-2013. The total area of wetlands decreased by 13.69 km2 (1.1%) from 2002 to 2007, and decreased by 43.23 km2 (3.3%) from 2007 to 2013. During the study period, the area of bottomlands increased by 73.2% and the area of artificial reservoirs and ponds increased by 6.2%, resulting in an increase in the percentage of total wetland area from 49.84% in 2002 to 55.37% in 2013. Conversely, the river area decreased by 5.6%, and lake area decreased by 29.7%, resulting in a decline in proportion to the total wetland area from 32.83% in 2002 to 24.14% in 2013. Artificial reservoirs and ponds occupied the largest proportion of wetland areas in Yangzhou as compared to lakes, rivers and bottomlands. Our analysis of landscape metrics shows that lakes, bottomlands and artificial reservoirs and ponds display different degrees of fragmentation, while rivers maintained a high connectivity and the patch shape was even and simple. In general, the wetland landscape pattern of Yangzhou is trending toward fragmentation and a more complicated shape. Landscape diversity increased as different wetland types became more equally distributed across the landscape. Driving force analysis indicates that economic development, increasing population, changes in the proportion of secondary industry and annual precipitation were the main factors driving changes in the wetland landscape pattern of Yangzhou city.