长江、黄河源区高寒湿地动态变化研究

Dynamic Change of Frigid Wetlands in Source Region of the Yangtze and Yellow Rivers

长江、黄河源区是中国湿地分布面积最大的地区之一,近年来湿地面积减少、功能退化引起了严重的区域生态环境问题。为了定量分析湿地退化过程,利用1986年的TM和2000年的ETM+卫星遥感数据,在GIS软件支持下,用景观格局指数对长江、黄河源区15a来湿地的分布和变化进行了研究。结果表明,15a间,长江、黄河源区湿地面积减少了2744.77km2,平均减少率为1.2%/a。长江源湿地的退化比黄河源明显。湿地主要是由高寒沼泽草甸湿地向高寒草甸湿地、裸岩裸土地和高寒草原演变,以及由水域向滩地转变。各湿地景观类型斑块数增加,破碎度和分维数提高,优势度降低,湿地景观空间结构趋于复杂,景观异质性增加。15a间研究区湿地生态服务价值降低了37.86×108元。气候干暖化是造成源区湿地变化的主要因素,人类活动加剧了这一进程。

The Source Region of the Yangtze and Yellow Rivers of the Qinghai -Tibetan Plateau is a serious environmental vulnerable region and one of wetlands of the largest area in China. Frigid wetlands are the most important ecosystems and have important ecological functions in the region, which could be divided into 4 sub - types ：frigid marshy meadow,frigid peat marsh ,fluviatile wetland and lacustrine wetland. Wetlands are the primary water sources for the industry and agriculture and city in the region, so wetland conservation needs to be pay more attention to. However, loss and degradation of wetlands in the region have resulted in serious environmental problems in the recent decades. In this paper, the types, the dynamical change and the temporal and spatial distribution characteristics of the wetlands were analyzed based on the means of remote sensing and the spatial analysis function of GIS. With software of AreView and ArcGIS,remote sensing images in 1986 and 2000 were interpreted and the wetland spatial database was built up. The change of wetlands in study area was illustrated using some landscape ecology indexes, such as the degree of fragmentation, the degree of dominance and fractal dimension index. The reason for the change was discussed from natural and human driving factors. The results showed that①the area of wetlands decreased 2 744.77 km^2 during the past 15 years, with the annual decreasing rate of 1. 74%; among wetland types, frigid marshy meadow lost the largest area. The change extent of wetlands differs in the Yangtze River Source Region and the Yellow River Source Region; ② it was indicated that the dynamic wetland change was mainly characterized by that frigid marshy meadow was transformed into typical frigid meadow, bare land and frigid steppe meadow respectively, as well as the water body transformed into beach land; ③wetland landscape pattern changes significantly during the research stage, the fragmentation and fractal dimension index of entire landscape were on the rise, the patch number index increased, and the dominance index reduced, which indicated that the shape of the landscape became more complex and the heterogeneity enhanced; ④ecosystem service values of wetlands decreased by 37.86 × 10^8 Yuan （RMB） from 1986 to 2000; ⑤warm and dry trend of climate was the major reason for wetland change,and the economic activities of human activities sped up the process.