Dynamic monitoring of vegetation and the impact of land use/cover change in the topical karst rocky desertification areas

The study area is located in the Zhongliang mountains of karst areas in southwestern China.Its mean annual temperature is 18 ℃,average annual rainfall is about 1,100 mm and height is about 500 m to 700 m.The terrain in the north side is higher than the south with steep slopes prone to soil erosion.Taking Zhongliang town for example,its total area is 4.75 km2,of which barren mountains account for 1 km2.As rocky desertification results in soil productivity sharply decline,regional economic develops slowly with hostile survival condition.Based on the dataset of MOD13Q1 from 2001 to 2014,digital terrain elevation data and the multi-period land use data,the Fractional Vegetation Cover (FVC) degree was estimated with the dimidiate pixel model in the topical karst rocky desertification areas.The vegetation cover variation tendency was simulated by the linear regression.We carried out the transformation matrix of land use,made comparison of land use changes before and after management,and analyzed the statistical characteristics of land use changes in vegetation change regions.Then the spatial-temporal variation characteristics of FVC and land use and the response mechanism between FVC and land use,terrain were discussed in detail.The results indicate that the percentage of areas with increasing vegetation cover is 76.69,while the area with decreasing vegetation cover accounts for 10.12% of the total area.There is obvious improvement tendency and the ecological regime also recovers greatly.The transformation matrix between 2005 and 2014 shows that human beings activity is the main driving factor and the cultivated land to woodland and construction land are the main transformation types in Zhongliang mountains.The phenomenon of vegetation degeneration has been affected extremely by human activity.The vegetation improvement,barely influenced by human beings activity,is mainly related to the natural restoration.