Land System Change Features in Shaanxi Loess Platform Region

Based on GIS and RS,landuse variation features in the Shaanxi loess platform region from 1985to 2010were analyzed by a series of landuse change indexes.Results are as follows:In 2010,cultivated land, grassland and built-up land occupied 984 337.30,143 030.47and 105 871.35hm2,whose percentages over the total area of the loess platform region were 77.89%,11.32% and 8.38%,respectively.During the research period,cultivated land,grassland,forestry land and water area decreased by 20 866.61,11 065.22, 1 186.44and 748.96hm2,respectively,accounting for 2.08%,7.18%,4.60%and 11.64%of each of land types in 1985,while built-up land increased by 33 902.8hm2,which took up 47.11% of built-up land in 1985.There were 26 668.8hm2 cultivated land changed into built-up land,accounting for 96.26%of the total area changed into built-up land,and 18 923.9hm2 grassland changed into cultivated land,accounting for 93.24% of the total area changed from grassland.The land system was relatively stable during 1985—1990(synthetic dynamic index was 0.52),and the landuse change was active during 1990—1995(synthetic dynamic index was 0.36).Since then,the synthetic dynamic index gradually decreased,the land system tended to be stable,and the value of synthetic dynamic index decreased to 1.16from 2005to 2010.In space,cultivated land changed into construction land was tremendously distributed around cities and towns,the mutual transformation between the cultivated land and grassland mainly occurred in the eastern part of Weinan platform region,the northern part of Xianyang and Baoji platform region.