Quantitative assessment of urban expansion impact on comprehensive productivity of cultivated land in Tangshan city based on RS and GIS

It is of great significance to research the changing patterns of current regional cultivated land and to explore its impact on grain productivity. With the assistance of Erdas software, the actual land use map and statistics data of Tangshan, the maps about the urban land expansion distribution in Tangshan were acquired by interpreting LANDSAT and TM/ETM images of 1993 and 2003 with the aid of the technology of RS and GIS. Method of man-machine interactive operation was applied to interpret LANDSAT and TM/ETM images of 1993 and 2003. Meanwhile, according to the database of soil attributes and spatial parameters in classification and gradation for farming land in Tangshan, the correlation relationship between the land utilization index and the realistic productivity was established. The loss of cultivated land and comprehensive productivity caused by the urban expansion from 1993 to 2003 was studied and analyzed by methods of the statistical analysis and the spatial analysis The results indicated that the cultivated land resource in Tangshan was occupied 14.27×103 hm2 in the urbanization expansion during the past ten years. Especially, the cultivated land with high productivity and favorable facilities in the suburbs was decreasing much faster because of their close contiguity to the expanding city, and the total loss of the capacity of cultivated land caused by land shrinkage reached 135 thousand tons. Finally, it might be concluded that rapid urbanization was posing an increasing pressure on land resources, of which the impact on regional agricultural production and food security allowed no neglect.