The characteristic of land changes in ecologically fragile Kast Areas: a case study in Northwest Guangxi, China
喀斯特生态脆弱区桂西北土地变化特征

Karst areas have usually poor geochemical conditions and fragile ecology, due to rocky desertification which is often induced by ineffective land uses and management. To understand land change in the Karst region over the past 20 years in North\|western Guangxi, China, indexes of singe land change velocity, comprehensive land change velocity, land use degree, and spatial distribution were investigated by land surveys, and analyzed used information from remote sensed images of Landsat TM in 1985, 1990 and 2000, and RS, GIS and GPS techniques. The results show that shrub, woodland, and sparseness land were the main land types in the region (total ratios were 73.72%, 74.14% and 73.59% in the three years respectively), where the proportions of rocky land and sparseness were high (total ratios were 20.44%, 22.84% and 20.44% in the three years respectively). Land types in the study area have changed dramatically between 1985 and 2000. There were significant differences in land changes among different land types. Arable land, rocky land and woodland decreased in the early phase of the period, but increased afterwards, while paddy field, sparseness and grassland changed opposite, resident land increased continuously. Due to the influences of the precipitation and the environmental immigrant, the land change velocity and land use degree during the period from 1990 to 2000 were higher than those from 1985 to 1990 (93.87% and 63.54% respectively). Since 1990, the rocky land increased and the ecological quality declined.