Analysis on the Characteristic of LUCC in the Environment-forced Emigration Region of the Karst Southwestern China Based on RS & GIS——A Case Study of Huanjiang County in Northwest Guangxi

With the rapid and wide development of the modern globe information science,RS GIS are now increasingly becoming the most powerful means to solve such problems as the eco-environment survey,land use changes,sustainable development decision-making,estimation of vegetation biomass,et al,which once were very arduous to be disposed by the traditional research mode.According to the datum derived from Land sat TM/ETM images in 1988 and 1999,associating with 1∶250000 DEM,the land use and land cover changes in Huanjiang County,which is located in Northwestern Guangxi Zhuang Autonomous Region of China,were analyzed.The results revealed that,with the rapid growth of population and expansion of economy,great land use pattern changes in this county had taken place:the arable land and grassland areas expanded 178.2km~2 and 365.4km~2 respectively,and correspondingly the proportion in the total areas increased by 3.95% and 8.09% during the whole 11 years;At the same period,as the biggest land use shift type,unused land area decreased 535.1km~2 and its proportion in the extent of whole county declined by 11.85%;on the contrary,the change of the forest land area was very small.Further analyzing all kinds of land use shifts,the percent of the areas of arable land,grass land and unused land increased by 41.78%,51.71% and 57.34% respectively.There were significant shifts among forest land,grass land,arable land and unused land during 11 years.Among them,with forest land mainly changing into grassland,the unused land transformed in a large scale,mostly converting to arable land,forest land and grass land.According to the study on the relations between the index of region land use comparative change rates and the frequency of the major types of land use changes,it could be concluded that if all indexes of regional land use comparative change rates were less than the whole region,namely Huanjiang county,then theoretically the frequency of this major type of land use change was high.Such regional development characteristic could be explained by its present stage:the survival economy development.Here,the index of comprehensive land use dynamic change degree was firstly used to indicate a(region's) competition ability,and accordingly confirms the swelling point:Shien,which was the center of Huanjiang county.