Land Use Structure and Temporal-Spatial Variation Analysis in Eight Main Agricultural Regions in China

There are eight main agricultural production regions in China,which play a critical role in China's agriculture.In this paper,the authors examined spatial and temporal changes in land use types in the eight regions during the past 15 years based on land use data of the 1980s and 2005.Results show that cultivated land and land for construction were mainly distributed in the Huang-Huai-Hai Plain,the middle Yangtze River and Jianghuai region,the Sichuan Basin,and the Songnen Plain,whereas grassland,woodland,and unused land were primarily located in Xinjiang,the eastern part of Inner Mongolia,and the Sanjiang Plain.From the 1980s to 2005,the total amount of cultivated land area was found to increase with an uneven distribution over space.A significant increase occurred in Xinjiang,the eastern part of Inner Mongolia,and the Sanjiang Plain,whereas a substantial decrease in the Huang-Huai-Hai Plain,the middle Yangtze River and Jianghuai region,and the Sichuan Basin.There was a remarkable spatial transfer of cultivated land from eastern and central China,traditional agricultural core areas with a higher cropping index,to northwestern and northeastern China,ecologically fragile regions with a low cropping index,which led to an overall decline in land productivity of China.Grassland,the only land use type showing a decreasing trend in all regions,appeared to be the largest contributor to the area increase of all other land use types.Among the eight regions,Xinjiang and the eastern part of Inner Mongolia accounted for the largest proportion of the increment.Land for construction shows a tendency to rapidly grow,especially in the Huang-Huai-Hai Plain and the Songnen Plain,taking up 70% of the total increment.Both woodland and water bodies were also found to grow.About 90% of the net increase in woodland took place in the eastern part of Inner Mongolia,while a slight reduction occurred in the Sanjiang Plain and the Huang-Huai-Hai Plain.An 2.8974×106hm2 increase in unused land was observed during the same period,and the eastern part of Inner Mongolia contributed the greatest increment of 2.6772×106hm2.Among the unused land,the sandy land,marshland,and bare land increased by 1.0100×106hm2,2.1671×106hm2,and 0.1729×106hm2,respectively,which might be indicative of significant land degradation across these regions.One of the reasons might be related to vulnerability of ecology of the regions.The continuing increase in the cultivated land led to large occupation of ecological water bodies,resulting in deterioration of the environment,water and soil loss,as well as a reduction of natural vegetation.On the contrary,unused land in the Huang-Huai-Hai Plain,the middle Yangtze River and the Jianghuai region,and the Sichuan Basin decreased to varying degrees.Land resources are expected be in short supply in the near future due to rapid industrialization and urban sprawl.