Temporal and spatial distribution of Litang rangeland's desertification on North-western plateau of Sichuan using TM image.

Based on the TM image,using vegetation cover as the main evaluation index of the remote sense monitoring,temporal and spatial distribution of Litang rangeland's desertification was analysed,The result indicated that grassland desertification was serious.The areas of rangeland's desertification occupied 34 % of the total grassland area.Seriously desertificated and moderately desertificated respectively occupied 12.3 % and 5.1 % of the study area,and the lightly occupied 16.6 %.According to spatial distribution,the moderately desertificated and lightly desertificated had a very wide distribution,and seriously distributed in the northwest and southeast of the study area.From 1989 to 2005,the area of rangeland's desertification had an significant increase of 42.87 square kilometers with an average rate of 2.1 every year.The remote sense monitoring through abstracting vegetation index and converting it into vegetation cover was a easy,convenient and practicable method to monitor for grassland desertification.