Remote sensing monitoring of grassland degradation based on NPP changein the Maduo County of the sources region of Yellow River

Maduo County is a typical grassland degradation area in the sources region of Yellow River or even in the sources region of the Sanjiangyuan (the Yangtze River, the Yellow River, and the Lancang River). In this study, the net primary productivity (NPP) of the grassland was derived from the Landsat TM data and the relative auxiliary data in 2008 based on CASA model. Furthermore, taking the reduced percentage of the NPP as measurement index, grassland degradation information was obtained. Compared the grassland degradation information in 2008 to those in 1997, this study showed that the area of severely degraded grassland decreased by 5 944 km2; and distributing in the north region of Maduo County. The monitoring results also showed that grassland degradation level was related to grassland type. Alione steppe was severe degradation, and alpine meadow was middle degradation, wetland was light degradation.