30年来青海三江源生态系统格局和空间结构动态变化

The dynamic changes of ecosystem spatial pattern and structure in the Three-River Headwaters region in Qinghai Province during recent 30 years

在多期遥感图像支持下,通过对生态系统类型进行辨识,获得了三江源地区生态系统类型空间分布数据集,并在此基础上分析了20世纪70年代中后期以来青海三江源地区生态系统格局和空间结构的动态变化。结果表明:30年来三江源地区生态系统格局稳定少动,生态系统类型变化相对缓慢,农田、森林、草地、水体与湿地和荒漠生态系统的年变化速率均小于0.5%,是长江、黄河流域乃至全国各区域生态系统转类变幅最小的稳定少动区。20世纪70年代中后期以来三江源地区生态系统类型的转变主要发生在草地和水体与湿地生态系统上,草地生态系统的变化主要发生在中部和东部地区,水体与湿地生态系统的变化主要发生在广大西部和北部地区。

Supported by MSS images in the mid and late 1970s, TM images in the early 1990s and TM/ETM images in 2004, the spatial distribution data set of ecosystem types was acquired through analysis and distinguishment, then the dynamic changes of spatial pattern and structure of ecosystems in the Three-River Headwaters region were analyzed since the 1970s. The results showed that alpine grassland occupied the largest area in the Three-River Headwaters region, and the area of alpine grasslafld occupied 64.68% of the total land area and 99.58% of the total grassland area. Wetland, glacier and mountain permanent snow-cover were characteristic ecosystems in the Three-River Headwaters region, with marsh area occupying 26.09% of the total area of water and wetland ecosystem, and glacier and mountain permanent snow-cover area 9.02 % of the total area of water and wetland ecosystem. As the characteristic ecosystems in the Three-River Headwaters region, wetland, glacier and mountain permanent snow-cover played important roles in providing stable water resource. During recent 30 years, the changes of ecosystem spatial pattern in the Three-River Headwaters region have been stable and rather slow, with an annual changing rate of farmland, forest, grassland, water and wetland, and hungriness ecosystem being less than 0. 5% respectively, the least but stable in the Yangtze and Yellow river basins, even the whole country. The changes of grassland, water and wetland ecosystem have occupied a dominant position in the Three-River Headwaters region since the mid and late 1970s. The changes of grassland mainly occurred in the central and eastern parts of the region, dominated by reclamation of grassland and conversion of grassland into unused land such as bare land, sandy and salt land. And the changes of water and wetland ecosystem mainly occurred in the vast western and northern parts of the region, represented by conversion of water body into beach land and conversion of wetland into grassland.