Study On Dynamic Changes Of Desertification In Yanchi County Based On NDVI And LUCC

Desertification has become a serious problem that endangered sustainable development of Yanchi County which is a typical agro-pastoral ecotone in China,it is both theoretically and practically significant to study the desertification in this area. Based on the multi-spectral Landsat TM/ETM+ image of the year 1999,2004 and 2010,the paper calculated the vegetation coverage (VC) using the Normalized Difference Vegetation Index (NDVI), obtained the land use/cover change (LUCC) information by means of supervised classification, and analyzed the LUCC using the conversion matrix and Markov process. Both the VC and LUCC is closely related to the desertification process, so the author combined them as the gradation index of desertification and divided the desertification into four degree, namely, mild, moderate, serious and very serious, to see the dynamic change of the desertification.The analysis of the VC shows that the average VC of the year 1999,2004 and 2010 in Yanchi county is 24.08%,26.97% and 23.92% respectively. The research on the LUCC shows that grassland is the main land cover of Yanchi county, with a percentage of above 60%,and that the conversion of the LUCC is mainly between grassland and and farmland, but the conversion speed is slowing down.As to the dynamic change of desertification in Yanchi county, the desertification degree of more than 60% of the land is moderate and the ratio is still increasing. The area of the land with the mild and very serious desertification degree is continually decreasing, and the serious desertification land is also decreasing after a first increasing trend. So the overall desertification change trend is towards moderate, which kind of land is composed mainly of grassland with moderate VC.