中文摘要：

草地是黄河源区最主要的覆被类型，采用黄河源区玛多县1977年、1990年和2003年3期夏季时相的MSS／TM遥感影像，通过人机交互式目视解译方法，首次采用草地覆被变化分类系统，提取了玛多县1977年～2003年间草地覆被时空变化特征，在此基础上分析了玛多县20世纪70年代以来的草地覆被时空变化特征，以及草地覆被变化与高程、坡度和坡向之间的关系。主要结论有：①玛多县的草地退化格局在20世纪70年代已经基本形成。之后退化过程一直持续发生，1990年～2003年间退化程度略有加强；②草地覆被变化以轻度和中度退化为主，主要类型为破碎化和覆盖度下降，这2种类型对应的草地面积比重为27．62％；③草地覆被变化主要发生在海拔4200m～4700m的范围；④草地覆被变化主要发生在坡度0°～15°范围内，在此以上的坡度发生的变化较少，坡度在50以下时，各种草地覆被变化类型的发生随着坡度的增加而增加，当坡度大于12°时，变化的发生随着坡度的增加而减少；⑤随着坡向的变化，草地覆被的变化的发生没有太大的差异。

英文摘要：

Grassland is the main cover type in the region which includes the source of the Yellow River. There are many studies on grassland in this area, but most of them use data from after the 1980s, and are not comprehensive. The data used in this research is from the 1970s, so reflects the situation from an earlier time period. We used remote sensing images from 1977, 1990 and 2003 for the interpretation of land cover in Madoi County in Qinghai Province. As other research has shown, the degradation of grassland is mainly due to changes from grassland to other land use types, but there also other types of changes such as fragmentation and decreased coverage. We first used the classification system for grass cover change, and then through the comparison of remote sensing images from different time periods, the grass cover change is clearly described and we calculated statistical data on grass cover change in Madoi County. The grass degradation area of each type and degradation degree of each level was derived from analysis of the interpretation results. The temporal and spatial characteristics of grass cover change were obtained and analyzed in terms of elevation, slope, and aspect characteristics. The results show that the grass degradation pattern of Madoi County was already formed in the 1970s and degradation has continued since then, becoming serious after the 1990s. The grass cover change in Madoi County is mostly lightly or moderately degraded, and the main type of grass cover change in Madoi County is fragmentation or decreased coverage. Changes meters, and concentrated on in grass cover were mostly between slopes between 0 and 15 degrees. the elevation of 4200 meters and 4700 There is no relationship between grass cover change and aspect. There are multiple causes of grass cover change in Madoi County, and quantitative analysis should be done to reveal the main factors causing the grass degradation patterns, to provide decision-making support for ecosystem restoration work.