The Studies Of Desertification Monitoring

Taking Yanchi County in Ningxia Hui Autonomous Region as the research object, the main causes of desertification,dynamic change and present situation of desertification were analyzed by using the methods of biodiversity,multivariate statistic analysis and Vegetation fraction Remote sensing estimated manners based on depart two grid cell model design method using NDVI as parameter.The result showed that the growth status in recent year is good.During the 2002~2005 four years, the best vegetation growth status appear in 2003, the worst appear in 2005.Through the data analysis, the vegetation status of wasteland sample and de-farming sample in 2001 is better than that in 2002, which explain these two measures are effective, the best one is returning land for farming to forestry, then the next one is shelf the wasteland. Separately analyze the NDVI in 1989 and 2003 show 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, especially the later is increasing more obvious, which show that the desertification in YanChi county has reversed because of the comprehensive harnessing measures. In the course of research, the area of vegetation cover type with no change is 3692km2; mainly consist of the vegetation with middle cover degree. The degenerated vegetation area is 608.61 km2, otherwise the vegetation restoration area is up to 3310.13km2 that is 5.4 times than degeneration, which show that the vegetation cover conversion in YanChi county take vegetation restoration as important.Analyze the dynamic changes of every sandy dune land in Yanchi County in the last 40 year, found that the region desertification before 1989 in YanChi County appear enlarge trend, the sandy dune area in 1989 has increased to 2366.67km2 from 1006.11km2,each year enlarge 46.92km2,the average annual increase ratio is 4.66%.Appear decrease trend after 1989,especially after 2000,until 2003, the desertification area has decreased to 455.75km2,take 19% to 1989.The data analyzed result is consistent with located monitoring and NDVI result.Then this paper analyzed the causes of desertification dynamic change furthermore, the research show that the desertification area has negatively correlated with the precipitation in former year (α<0.05),has obvious linear positive correlation relationship with the total amount of goat (α<0.01).According to the analyzed result, summarize that the main causes of better vegetation restoration speed were two points: firstly, first is 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. Secondly, the distinct increase of rainfall especially in 2002 and 2003 contributed greatly to restoration of vegetation.