长江源区土地覆盖变化与草地退化格局的时空分异

基于野外调查、遥感影像和统计资料，分析了1987-2007年长江源头地区土地覆盖变化和草地退化格局的时空分异特点，并从海拔、坡度和坡向3方面探讨了导致长江源区草地生态环境变化的主要自然因素.结果表明： 研究期间，长江源头地区土地类型破碎化整体呈增加趋势，自然地理条件和气候变化是导致土地格局变化的主要驱动因素；不同海拔草地退化面积差异显著，研究区草地退化主要发生在海拔4800～5100 m范围内，且退化面积随海拔的升高呈增加趋势，退化面积比重在不同坡度和坡向的差异较大.1987-2007年，长江源头地区气候呈暖干化趋势，区域土地覆盖类型空间结构变化明显；不同坡向、坡度和海拔的草地退化分布格局与高寒环境和人为干扰的格局基本一致，高寒环境和气候演化对草地生态系统格局起决定作用.

Spatiotemporal differentiation of land cover change and grassland degradation pattern in Yangtze River headwaters area

Based on field survey data, remote sensing images and statistical data, this paper analyzed the spatiotemporal differentiation of land use and grassland degradation patterns in Yangtze River headwaters area in 1987-2007, and discussed the main natural factors (elevation, position and slope) leading to the changes of this area's grassland ecological environment. In 1987-2007, the fragmentation of this area' s landscape patterns had an increasing trend, and natural environment and climate change were the main driving forces of land use pattern change. There existed significant differences in the areas of grassland degradation at different altitudes. Grassland degradation mainly occurred at altitudes 4800-5100 m. The grassland degradation area tended to increase with increasing elevation, and the proportions of the degradation area varied greatly over different slopes and aspects. The climate in the study area became warm and dry, and the spatial structure of regional land cover changed obviously. The distribution patterns of grassland degradation at different elevation, position and slope coincided with alpine environment and human disturbances, suggesting that alpine environment and climatic change were the decisive factors to the grassland ecosystem pattern in Yangtze River headwaters area.