近15年来长江源区土地利用变化及其生态环境效应

长江源区是我国重要的水源涵养区，也是高海拔地区生物多样性最集中的地区和生态变化最为敏感的地区。基于1986年TM和2000年ETM+卫星遥感数据和野外实地调查，采用GIS软件和景观生态空间分布格局分析方法，对长江源区近15年来土地利用类型的时空变化进行了研究。结果表明：1986～2000年，源区林地和湿地面积减少54.2 %和42.69 %，建设用地、耕地和未利用土地面积分别增加120 %、43.83 %和21.1 %。全区土地利用的空间位置转换面积大于其数量变化，土地利用类型总变化的面积大小依次是草地＞未利用土地＞湿地＞水域＞林地＞耕地＞建设用地。土地利用动态转化过程以草地转化为未利用土地、湿地转化为草地和未利用地逆转为草地为主要特征。15年里景观破碎化程度加剧，分维数和多样性指数增加，优势度降低，景观异质性增强。长江源区脆弱的生态体系对土地利用变化响应强烈，造成水土流失与沙漠化程度加剧，导致大范围高寒草甸、草原植被退化，湿地萎缩。气候变化和人类经济活动是导致研究区土地利用变化的主要因素。

LAND USE CHANGE AND ITS IMPACT ON THE ECO-ENVIRONMENT IN THE SOURCE REGION OF THE YANGTZE RIVER DURING THE PAST 15 YEARS

Based on 1986 TM and 2000 ETM data,the land use and landscape pattern change in the source region of the Yangtze River was studied with geographical information system (GIS) and the analytic method of landscape ecological spatial patterns in both spatial and temporal aspects in this paper. Conclusions of this study are drawn as follows:from 1985 to 2000,woodland area reduced by 54.2%,wetland area by 42.69%,while the construction land,cultivated land area and unused land area increased by 120%, 43.83% and 21.1% respectively. The area order of individual land use changes was grassland>unused land>wetland>water body> forestland> cultivated land> construction land. As a whole, the swap change was greater than its quantity. The analysis of the landscape pattern shows that the landscape fragmentation degree,the fractal degree and the diversity index increased,implying the enhancement of landscape heterogeneity. The eco-environment in the study area is very vulnerable to the land use change,resulting in land desertification and loss of water and soil. These changes result in the degradation of high-cold meadow vegetation and wetland. Abnormal climate and irrational human activities were the major reason of these changes.