The dynamic changes of ecosystem spatial pattern and structure in the Three-River Headwaters region in Qinghai Province during recent 30 years
30年来青海三江源生态系统格局和空间结构动态变化

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 grassland 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.