Spatial-Temporal Evolution of Land Use/Cover Change in Middle Section of Heihe Basin Since 1975

The Heihe River is one of the most important inland rivers in the northwest arid region of China.With its economy and population growing rapidly,the Heihe basin is faced with deteriorating ecological environment in recent years.Therefore,it is very important and urgent to analyze changes in land use/cover in the area,and their driving forces,and eco-environment problems.The middle section of Heihe basin was chosen as a research area,of which the remote-sensing images of 1975,1987,1992,2001 and 2010 were picked as basic data for comprehensive analysis using corrlation analysis method and principal component analysis method in combination with transfer matrix.Variation amplitude,dynamic degree and intensity of land use were set as indices.Results show that within 35 years after 1975,the proportions of cultivated land and land for urban and rural housing and public facilities and for industrial and mining expanded steadily by 5.60 and 0.46 percentage points,respectively,and the area of grassland and water surface decreased by 3.87×10⁴ and 0.41×10⁴hm²,respectively.Among the various types of land use in the study,cultivated land was the highest in variation amplitude,reaching 0.1604% and was followed by grassland.The conversions of grassland into farmland and wasteland,and the coversion of wasteland into farmland and grassland and the coversion of forestland into grassland and vice versa were the main trends of the landuse variation.The major force driving the variation of the land use is development of the social economy.