Land Use Change of Slope Land in Karst Mountainous Regions,Guizhou Province during 1960-2010

Land use change has intensively been studied in different ways across the world and it has greatly been influenced by human activity such as land degradation and soil erosion,land acquisition and expansion during the process of urbanization.Therefore,it is important to understand the process of land use/cover change for policy making,evaluation of potential environmental problems and man-land relationship.The environment pressure has continuously increased with constant population pressure since the 1960s.Serious environment problems have resulted from livelihood,insufficient awareness of environmental protection as well as a lack of laws and regulations concerned.And then a strategy of sustainable development has been implemented to protect environment.The policy of returning cultivated land to forest and grassland was issued in the 1990s.The exposed area of carbonate rocks has 73% and the mountainous and hilly areas account for 92.5% of the total provincial area.Therefore,the slope land is the main part of cultivated land resource in Guizhou Province.This kind of land use pattern leads to ecological issues of serious soil erosion and rock desertification.So it is important to study the land use change of the slope land in karst mountainous regions in Guizhou over the past 50 years.Based on GIS and RS technologies,this paper conducts studies on the regions with the slope greater than 25 gradients of karst mountainous regions in Guizhou Province.With the topographical maps at the scale of 1: 50000 in 1960 and Landsat TM and HJ-1A/1B RS images obtained in 1990 and 2010,the land use data in 1960,1990 and 2010 was interpreted.Combined with the hydrogeological map and slope map of Guizhou,the land use variations in slope land are analyzed.The results are shown in the following aspects.(1) From 1960 to 1990,forest land,shrub land and water were decreasing,in which shrub land decreased the most and secondly forest land;while grassland,construction land,bare rock and cultivation land were increasing,in which grassland increased most,followed by the cultivation land.(2) From 1990 to 2010,shrub land,bare rock and cultivation land were decreasing in which cultivation land reduced the most;while forest land,open forest land,grassland and water were increasing in which open forest land increased the most.(3) The land use types which were distributed in an inversely proportional to slope were forest land,open forest land,water,construction land and cultivation land;while those which were proportional to slope were shrub land,grassland and bare rock.The development of this area before 1990 was mainly focused on agriculture,but after 1990 it changed and guided by urbanized development.It is indicated primarily that the cultivated land increased drastically from 1960 to 1990 as a result of reclamation under the increasing population pressure and the total area of cultivated land in China dropped in a continuous way,while the total area of city grew in a continuous way because the policy of returning cultivated land to forest and grassland had been implemented since 1990 and urban expansion had grown rapidly.