The Changes on Quality and Production Capacity of Farmland in the Main Agricultural Regions during Recent 20 Years

The main agricultural production region,which plays an important role in the agricultural outputs,constitutes the key area of farmland-protection.The recognition of dynamic changes of the arable land in these areas turned to be important and essential.This paper aims to understand such spatial-temporal changes of cropland by comparing the land use map of 1980s and 2005 provided by Data Center for Resources and Environmental Sciences,China Academy of Sciences.With the help of 1∶1000 000 Land Resource Map,the changes on quality and production capacity of farmland brought by the farmland dynamic changes are evaluated.The main findings are:1) In 2005,the cultivated land in the whole study area is about 9 321.96×104 hm2,and increased about 175.53×104 hm2 in the recent 20 years.2) In space,the cropland dynamic pattern can be characterized by north-increase and south-decrease.The northern four regions,including eastern part of Inner Mongolia region,Xinjiang region,Songnen Plain and Sanjiang Plain,are the net-increase area,the farmland area in these regions are increased by 10.29%,19.10%,10.91% and 14.14%,respectively;While the southern four regions,including Huang-Huai-Hai Plain,middle Yangtze River and Jianghuai region,Huanan region and Sichuan Basin,are net-decrease regions,the amount of the cropland are decreased by 2.17%,2.00%,3.15% and 5.61%,respectively.This dynamic pattern result to the shift of cropland weight from the eastern and middle part of China to the northeast and northwest part of China.3) According to the evaluation result,the farmland can be classified into four classes.Farmland in class I has the best quality with no limitation for cropping,which the one in Class II has relatively high quality with certain limitations when used for crop.The class III is relatively-low suitable for cropping,and land in class IV is not suitable for farming.The dynamic changes on farmland resources impact the land quality obviously.The farmland in class I decreases by 3.24%,while the class II,class III,and class IV farmland is expanded by 2.91%,7.81% and 14.10%,respectively.4) Owning to the remarkable spatial shift of cultivated land distribution from Eastern and Central China and traditional agricultural core areas with higher cropping index,to Northwestern and Northeastern China,ecological fragile regions with low cropping index,the overall land productivity of China is declined even though the overall amount of farmland is increased.The productivity is 9.24×108 t in 1980s,while it reaches to 9.17×108 t in 2005,decreasing by 0.84%.