在建立玛多县草地植被覆盖遥感监测和评价指标体系的基础上,运用地理信息系统软件和基于植被指数的象元二分法模型,反演了玛多县1985～1988年、1995～1998年和2005～2008年3个时期的草地盖度影像,分析了玛多县不同时期草地植被覆盖的动态变化.结果表明:1985～1988年到1995～1998年高覆盖和中高覆盖草地分别减少了1 452.50 km2和599.56 km2,而中覆盖、低覆盖和极低覆盖草地分别增加了56.63 km2,948.95 km2和1 046.49 km2,说明6年间草地覆盖度在逐年降低,尤其低覆盖和极低覆盖草地下降速度快,程度大;1995～1998年到2005～2008年高覆盖和中高覆盖草地依然表现为减少,分别减少了855.67km2、69.86 km2,但相比上一期,有了很大程度的降低;低覆盖和极低覆盖草地分别减少了222.75 km2、424.52 km2,虽然面积不大,但趋势可喜,这两类型草地覆盖首次出现了逆向转化,说明2000年以来实施的"青海三江源自然保护区生态保护和建设总体规划"生态建设项目效果明显,并运用马尔科夫模型对2015～2018年玛多县草地覆盖度进行了预测,极低覆盖草地面积约为1 579.55 km2,恢复到了20世纪80年代的水平,草地植被覆盖持续恶化逐步得到控制.%Grassland coverage image of three period, 1985 ～ 1988, 1995 ～ 1998,2005 ～ 2008, was inversed based on GIS software and pixel dichotomy model,and the dynamic changes of grassland vegetation coverage in different period were analyzed as well in Maduo county. The results showed that high and medium-high coverage grassland reduced 1 452. 50 km2 ,599. 56 km2 respectively while medium,low and extreme low coverage grassland increased 56. 63 km2 , 948. 95 km2 and l 046.49 km2 respectively from 1985 ～ 1988 to 1995～ 1998. It showed that grassland degrade gradually in past 6 years. High and medium-high coverage grassland still degraded From 1995 ～ 1998 to 2005 ～ 2008, the area reduce 855.67 km2, 69. 86 km2, low and extreme low coverage grassland reduce 222.75 km2 ,424.52 km2 respectively,but compare to the period of 1985～1988 to 1995～1998, the range was not obvious. The two kinds of coverage grassland showed reverse transformation firstly. It has been proved that the effects of ecological construction projects,The Planning for Ecological Protection and Construction in the Nature Reserve of Three River Source Area in Qinghai since 2000,were absolutely obvious. A predict showed that the area of extreme low coverage grassland, in 2015～2018, was about 1 579.55 km2, it would back to the level of 80s by using Markov model. The continuous degrading of vegetation coverage will undercontrol gradually.
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