Study on baseline vegetation coverage of desertification grassland in northern sand-fixing region based on remote sensing

Abstract: To promote ecology healthy, safe and steady development of sand-fixing ecological functional zone in northern China, and make the appropriate utilization of grassland resources with balanced and sustainable development, we take Zhenglan Banner as a typical instance of sand-fixing ecological functional zone in northern China to carry out research on baseline vegetation coverage of grassland. By using SPSS, the vegetation coverage remote sensing inversion model is established with normalized difference vegetation index (NDVI) extracted from Landsat TM images and plenty of synchronous field survey data. We use this model to extract the regional vegetation coverage of Zhenglan Banner, distinguish sand lands according to its criteria. With help of ArcGIS and ENVI, we extract spatial distribution data of half fixed sand land and fixed sand land respectively, and then convert data of half fixed sand-land and fixed sand-land to their distribution border polygon vector data. we obtain borderline of half fixed sand land and fixed sand land with polygon transformation tools provided by ArcGIS, and obtain line of intersection of half fixed and fixed sand land with intersection tools. With line of intersection and data of vegetation coverage distribution, we use statistical tools in ArcGIS to extract vegetation coverage corresponding to intersection line and count number of pixels of coverage. We obtain average of vegetation coverage from borderline between semi-fixed sandy land and fixed sandy land with their vegetation coverage and the corresponding number of pixel, and the average coverage of intersection line between two kinds of sandy land is taken as baseline coverage. With the baseline coverage, we regard sandy land which is less than value of baseline as substandard region, only those regions above baseline can be utilized appropriately. Experimental results show that average coverage of intergradation region between semi-fixed sandy land and fixed sandy land is 30.47%, which is verified with baseline coverage field survey. The vegetation coverage remote sensing inversion model was established with normalized difference vegetation index (NDVI) extracted from Landsat TM images and plenty of synchronous field survey data. Using this model, we extracted vegetation coverage of Zhenglan Banner. And then, the baseline coverage value was gained based on the boundary of the half fixed sand and fixed sand. The baseline coverage was set as the limited value, therefore, we can calculate the area of conservative grazing zone, that is 396,927.3 hectares, which is 39% of the grassland area in Zhenglan Banner. With data obtained in the experiments, structure of grassland resources utilization was constructed under constraint of ecological protection, which can provide a technical guarantee for promotion of well-balanced circulation of sand-fixing ecosystem, maintain service functions in region ecosystem and appropriately utilize region ecological resources in the north of China.