AN ANALYSIS ON THE RELATIONSHIP BETWEEN THE ECOLOGICAL CHANGE AND SANDSTORM IN THE DROUGHT ZONE OF MIDDLE NINGXIA

The year-to-year quantificational change characteristics in Yanchi county of the drought zone of the middle Ningxia where occurred sandstorm frequently in the 1990s were revealed on the whole by using TM remote sensing and land survey data. Analyzed results show that ecological condition in Yanchi county in the early 1990s was obviously better than that in the late 1990s. Drought was mainly reasons caused ecological change. Human activity, such as land over-cultivated on a large scale, over-pasturage and digging the liquorice in excess, however, was another important reason. It was the situation of ecological environment became worse and worse in whole and got better in part that caused the fall in threshold of dust-blowing. The probability of sandstorm occurrence had been increased remarkably in the drought zone of middle Ningxia in the past 30 years according to the analysis of the cause of sandstorm and by mean of synthetically analysis of individual cases of thirty-year sandstorms in Yanchi county. Due to those: climate, water resource shortage and land overloaded etc which caused desertification in western China would not be improved in predictable longterm period in future, moreover, ecological environment is frangible, easy to ruin and difficult to resume, and with the objective quantificational analysis on data, we put forward a point the first time of that the probability sandstorm occurrence in western China would be in the ascending situation from now on.