Land-cover change of semi-arid area in Northeast China since 1950s

摘要

The semi-arid and semi-humid agricultural region in Northeast China occupies parts of the Songnen Grassland and the Horqin Grassland. The region has been an important base in food production and stockbreeding. During the past 50 years land cover in the region underwent dramatic changes. Based on thematic maps and statistical data, the change trajectories of cultivated land and grassland were traced for the period from 1950 to 1985. Visual interpretation of the false composite images followed by screen digitizing was applied to obtain digital data of land cover. With the spatial analysis techniques of GIS, the spatial patterns and changing characteristics of land cover for the period of 1986-2000 were analyzed. The percentage of cultivated land expanded from 38.6% to 48.4% from 1986 to 2000. Salinized land also increased rapidly. The area of grassland decreased severely with the reduction 6.8% at annual loss rate of 1.98%. Forestland, grassland and water area are more fragmented. The dominant land cover changes were the conversion of grassland and forestland into cultivated land, dryland into paddy field, and grassland into salinized land. Land cover changes were closely related to climate fluctuation, rapid growth of population and underdeveloped economic position.