Land Use/Cover and Landscape Pattern Changes over the Karst Reservoir Area of the Red River,China

Exploitation of hydroelectric resources cannot avoid bringing certain adverse impacts to land use and eco-environments when bringing huge economic benefits.It is therefore critical for sustainable development of the Karst reservoir area on the Red River to investigate the characteristics of the variations in land use and landscape patterns.The environment in the Karst reservoir area of the Red River has become severely degraded due to the exploitation of water resources,irrational human activities and so forth.Dahua Yao Autonomous County in Guangxi Zhuang Nationality Autonomous Region,China,with an area of about 2753.31 km2,is located in the middle reaches of the Red River.Dahua County,where the environment was highly degraded,the earliest reservoir area was formed,the most immigrants existed and hydroelectric power was earliest utilized over the Red River areas,was selected for investigation in detail.The characteristics of the variations in land use and landscape patterns in the area were examined from Landsat TM images acquired in the year 1988,1992,1999,and 2006,respectively,on the basis of geographic information system(GIS) and related methods for landscape analyses.In addition,the effects of the dynamic changes in land use types upon landscape pattern frangibility were also analyzed.Results indicated that cropland,dry land,orchards,urban built-up land,water bodies,moderate grassland,sparse grassland,shrub and forests showed relatively large changes.Bare rocky dominating the study site did not show significant changes over the study period.Significant increases in the areas of orchards,urban built-up land and water bodies,and significant decreases in the areas of paddy land,forests,moderate grassland,sparse grassland and dry land were observed,showing high variations in land use changes for different periods.Besides,there existed an apparent spatial heterogeneity in land use changes over the study area.Meanwhile,the transition among different land use types was complex,and obvious trends in land degradation and the transition of different land use types to water bodies exhibited.Consequently,the landscape in the study area has become more fragmented as demonstrated by an increase in the patch number and a decrease in the mean patch size(MPS) at landscape level.The regional landscape frangibility increased from 1988 to 1999,peaked in 1999,and then decreased from 1999 to 2006.Analyses of the regional landscape frangibility suggested that irrational human activities,rapid hydropower development and potential environmental factors together exerted a combined eco-environment influence on changes in land use/cover and landscape patterns over the high-ecological risk Karst reservoir area,nearly exceeding the eco-environmental bearing capacity of this area.Immediate actions should be carried out in order to improve the environment and realize a sustainable development over this area.