Evaluation And Monitoring Of Sensitivity Of Karst Rocky Desertification In Southwestern Guangxi Based On Remote Sensing And GIS

Sensitivity of karst rocky desertification is defined that difficulty and possibility of occurring rocky desertification under the natural condition in karst mountain area. To evaluation the sensitivity of rocky desertification, monitor its dynamic change, it is very necessary for providing scientific references for prevention&control of desertification in karst mountain area. This paper take 16 countys in southwestern Guangxi as study region, base on scale of grid and county district, apply technology of remote sensing and GIS, research on evaluating sensitivity of rocky desertification, monitoring dynamic change , spatial analysis, and so on.Based on the unit of grid, and indices include lithology, vegetation fraction, slope and annual rainfall, to evaluate the sensitivity of rocky desertification. Dividing the sensitivity of rocky desertification into 5 grades, include extreme sensitivity, high sensitivity, moderate sensitivity, slight sensitivity and non sensitivity. The results show that: (1) Large area of sensitive region of rocky desertification in study region, moreover, majority of area are in high and extreme sensitive state. It is extremely easy to occur rocky desertification. (2) High and extreme sensitive area comparatively larger than other county in Du'an, Dahua, Mashan, Lingyun, Daxin, Tiandeng. There, high and extreme sensitive area usually large stretches of distribution. The probability and hazard of occurring rocky desertification is comparatively large. (3) It is big of relief degree of land surface in extreme sensitive region, and extremely easy to occur desertification in this region. (4) The great majority of sensitive region distributing in the range of 500-1500 meter of line distance from population centre, and in the range of 0-1000 meter of line distance from road. The probability of influence of humankind is comparatively large.Base on the evaluation of rocky desertification by unit of grid, taking county district as unit, evaluating the sensitivity of rocky desertification and its danger degree. The results show that: (1) The aggregate level of sensitivity of rocky desertification in Du'an, Dahua, Mashan, Daxin, Tiandeng and Jingxi county is higher than other county, and the total possibility and fatalness of occurring rocky desertification is bigger and higher than other county; (2) The danger degree of rocky desertification is extreme danger in Mashan and Du'an county; and high danger in Tiandeng, Pingguo, Jingxi, Dahua county: and moderate danger in Daxin, Longzhou, Tianyang, Debao, Donglan county; and slight danger in Tiandong, Napo, Lingyun, Fengshan, Bama county.Dynamic change monitoring of sensitivity of rocky desertification, results show that: (1) Condition of vegetation cover have improved from 2000-2006. As a whole, it is a benign development trend that rocky desertification is becoming less sensitive. But, there are strengthen of sensitivity of rocky desertification in some local regions. (2) The aggregate level of sensitivity of rocky desertification in each county having declined with different extents, but it is small, the aggregate level of sensitivity of rocky desertification have not changed largely or radically. (3) Dividing change of sensitivity of rocky desertification into 5 grades, including weakening evidently, weakening slightly, no change, strengthen slightly and strengthen evidently. There are only 27.65% of area have changed about sensitivity. And its degree of change is small, based on the principle of slight variation, evident change are few. Look at the spatial distribution of change, abrupt slope region (slope from 25°—35°) is the main region where sensitivity of rocky desertification have changed. And the change mainly taken place in the region of successive limestone and successive dolostone, mainly taken place in nearby region where line distance from road, especially in the region where line distance less than 1000 meter.Finally, this paper proposed some strategies and measures about prevention &control of rocky desertification.