Remote sensing-based monitor dynamically grassland degradation in typical regions, middle and upper reaches of Heihe River Basin, Western China

The severity of grassland degradation in the typical regions near the middle and upper reaches of Heihe River Basin, Western China was assessed from TM image in conjunction with in situ samples of above-ground biomass, fractional grassland cover and palatable grass percent collected over 1 m2 sampling plots. The above-ground biomass, fractional grassland cover and palatable grass percent were integrated to develop a grassland vegetation degradation index (GDI). Remote sensing-based monitoring model for grassland degradation was established through regression analyses between GDI and vegetation index derived from TM image. The results of dynamic monitoring situation of grassland degradation using RS, GIS, and GPS techniques showed as follows TM imagery, in conjunction with in situ grassland samples data, could the efficient and accurate assessment of grassland degradation in regional scale, The degradation manifested three levels of degradation severity: severe, intermediate, and slight degradation. The area of severe, intermediate, and slight degradation was 499.86 km2, 772.67 km2 and 916.74 km2 , respectively, in 1986; 322.23, 815.20 and 1 015.84 km2 , respectively, in 2003. The overall situation presented both area and intensity of grassland degradation increased significantly, the degree of degradation worsened as well from 1986 to 2003.