Use of remote sensing and GIS to assess the effects of agricultural land quality on spatial extension of construction land in Chengdu

As a major commodity grain base in the Chengdu Plain, the city of Chengdu has played a significant role in the grain security of the Sichuan Province and the stability of national economy. However, with the urbanization process, the cultivated land quantity reduces and quality drops, which further affect the security of the grain production. In this study, we integrate remote sensing and geographic information systems to detect land-use change and reveal the increase in urban built-up land between 1992 and 2002. We compute the indicators of barycenters transformation and landscape index to illustrate the spatial expansion of the built-up land in Chengdu. The result shows that the built-up land increased from 31280 hm 2 to 41196 hm 2 . The net gain of the built-up land was 9916 hm 2 between 1992 and 2002. The quality of the cultivated land was in the third, fourth, fifth, and sixth grades, occupying 0.02%, 87.70%, 5.53%, and 6.75%, respectively. The barycenter of the built-up land moved 0.87 km westward and 2.54 km northward, respectively. With the built-up land patches reducing from 6230 to 5510, their fractal dimensions and broken degree decreased from 1.069 to 1.032 during the ten years, and the average patch area increased from 5.02 hm 2 to7.48 hm 2 . Finally, we propose a built-up land spatial expansion model based on the development stage and construction levels in Chengdu.