Study On Dynamic Changes Of Desertification Monitoring In The Semi-arid Crop-grazing Crisscross Area

Taking Yanchi County in Ningxia Hui Autonomous Region as the research object, the main causes of vegetation cover, dynamic change and present situation of desertification were analyzed by using the methods of MODIS image under supporting by GIS in four years.The result showed that the growth status in recent year is good.During the 2001-2004 four years, the best vegetation growth status appear in 2003, and the areas of land desetifacation has decreased. The changes of vegetation trend reflected the changes of desertification trend in a certain degree. The rainfall and correlated measures of the return 不 ing the grain plots to forestry closedly related to the changes of vegetation trend and the changes of desertification trend in this county.The space resolution of remoting sense image and imgae environment of target identification were improved and enhanced the vegetation information characterist by using processed remoting sense data multi-band combination and geometric correction. The image classification and comparision showed, during 2001-2004 vegetation covers degrees have changed in increase or decrease. In the course of research, 2003 shows that the vegetation with low covers degree has decreased obviously, high and middle covers degree vegetation all over the county has all increased at different extent, the area of vegetation low covers decreased 848.7km than 2001, take 64.3%, and vegetation middle covers area increased 560km~2 than 2001, take 13.3%, which show the vegetation low covers have converted to vegetation middle covers and the vegetation coverconversion in YanChi county take vegetation restoration as important.This paper analyzed the causes of vegetation and desertification dynamic change furthermore, the research show that the changes of vegetation and desertification related with rainfall. According to the analyzed result, summarize that the main causes of better vegetation restoration speed and desertification improved were two points: firstly, first is the distinct increase of rainfall especially in 2002 and 2003 contributed greatly to restoration of vegetation. Secondly, the implementation of policy of reverting farming land to forest and grassland since 2001 and forbidding graze in the whole county since November 1st, 2002.