The Spatio-temporal Changes of the Grassland in Madoi County,the Source Region of the Yellow River During 1990-2009

Madoi County is the core area of the source region of the Yellow River and it deserves special attention for its ecological environment and changes of functions. By the end of 20 century, under the impacts of natural and human beings, the ecological environment of the source region had been shown a worsening trend with mainly changing on grassland quality.The features and trends of spatial-temporal changes of grassland quality in Madoi County was investigated through supervised classification with the five Landsat TM images of during 1990-2009. The results showed that the grassland quality changed from high-cold steppe of high coverage to degradation, and then recovered gradually after management during these 20 years from 1990 to 2009. During 2000 and 2005, the area of middle-coverage grassland decreased faster, but increased slightly with the efficient management. The area of high-coverage grassland has been increasing stably since 1995. The study showed the low resistance stability and high resilience stability of plateau grassland system. All these indicated that the ecological management in Madoi County of the source region of the Yellow River has achieved a positive effect.