Fractal Characters of Rocky Desertification Land: A Case Study in Pingguo County,Guangxi Province,China

摘要

Karst rocky desertification is a kind of serious land degradation. And it is the third-largest ecological and environmental problem compared with China northwest desertification and soil erosion in loess plateau. Besides, fractal geometry theory is mainly used to explore the regularity, hierarchy and scale invariance hide in complex natural phenomena. And it is a new research angle that the fractal geometry theory is applied to rocky desertification land degradation research. In this study, to explore the fractal characters of rocky desertification, we selected Pingguo County as a case study area. And the data sources include TM data in 2005 growth season, 1:100 thousand land use data, and 30-meter DEM data of ASTER. Above all, vegetation coverage, gradient and land use mode were selected as critical indications of rocky desertification. Subsequently, with the help of ENVI, ARCGIS, SPSS, etc., we have got the perimeter and area of the three types of polygons. And on the basis of above period results, fractal dimension and stability coefficient were obtained by linear regression analysis fit method. In conclusion, different karst rocky desertification landscape mosaic structures show different stability. Firstly, from the aspect of vegetation coverage, low vegetation coverage, no vegetation coverage, middle vegetation coverage and high vegetation coverage display an increasing sequence. Secondly, from the aspect of land use mode, it shows a decreasing trend in stability as wood land, dry hill, middle coverage grassland, plain dry land, dry mountain, water area, paddy hill, thin stocked land, (urban and rural, mining, residential areas), other thin stocked land, high coverage grassland, shrub land and paddy field. Finally, from the aspect of gradient, the landscape of 0°-15°, 15°-18°, 25°-30°, 22°-25°, 18°22°, 30°-90° displays an increasing tendency in stability. Generally speaking, it is from a new angle that the fractal dimension and stability coefficient are put forward as a reflection of the characters of the rocky desertification land.