基于GIS网格技术的城镇周边永久基本农田划定研究——以江苏宜兴市为例

目的]通过运用网格化技术和综合评价法将研究区划分为4类永久基本农田划定类型区,为创新县域尺度永久基本农田保护区划定的方法和技术体系,协调耕地保护、经济发展和生态保护之间的关系提供有力支撑。方法]文章以宜兴市为实证研究区,将城镇周边区域网格化,选取综合等别、距城镇和可建设占用区的距离等因子作为评价指标,确定永久基本农田约束划入区。同时,根据土壤综合污染指数修订耕地利用等,得到耕地综合等,然后以耕地距离城镇、交通干线的距离和空间连片度作为评价指标,对耕地进行立地条件评价并划分等级,最后将约束划入区以外的耕地以综合等-立地条件的形式,划分为不同的类型区。结果](1)城镇外延区被划分为1.232 0万个100m×100m的网格评价单元,在网格环境下,纳入约束划入区的耕地面积5 170.33hm~2,占全部耕地的9.65%;(2)耕地利用等修订后得到的综合等与利用等相比,耕地等别依然集中在4、5等,受重金属污染区影响出现了8等耕地;(3)约束划入区外的耕地被划分为优先划入区、适宜划入区及整治划入区,耕地面积占比分别为21.16%、40.52%及28.67%。结论]通过网格化确定的约束划入型主要分布在规划选定的重点建设项目区和有条件建设区,与城镇主要发展方向一致,既满足了城镇连片发展的需求,也实现了对城镇周边优质耕地优先保护;优先划入型分布在城镇周边或交通干线沿线,区位条件优越,且耕地质量高;适宜划入型在立地条件或综合等方面有较大发展潜力,可通过整治措施提升其质量水平;整治划入型受重金属污染严重,综合等别较低且立地条件较差,在经过差别化的土地整治后可作为入选永久基本农田的后备资源。

PERMANENT PRIME FARMLAND DEMARCATION AROUND THE URBAN AREAS BASED ON GIS GRID

The delineation of permanent prime farmland is the important content of China′s land resources management and ecological construction, which require us to deal with dialectical relationship among the demands of economic development, the protection of high quality cultivated land and ecological environment quality.The study used the technology of grid environment to divide the cultivated land of suburb urban.Then the constraint area of the permanent basic farmland was determined which broke the traditional constraint of plot scale and administrative units.The grade of cultivated land was revised based on the soil comprehensive pollution index.Finally, according to the synthesis grade and site conditions, the type of the outside constraint area was divided.The results showed that (1) the extension of urban area was divided into 12320 grids with the size of 100m*100m.The constraint area was 5170.33hm2 which accounted 9.65% of the total cultivated land area and located in urban built-up areas.It could be influenced by future urban development and local government policies.(2) Thecultivated land grade still concentrated in the grade 4 and 5, but the grade 8 appeared because of the heavy metal pollution.(3) Outside constraint area of cultivated land was divided into priority area, suitable area and remediation area,accounting for 21.16%, 40.52% and 28.67% of total cultivated land,respectively.The priority area distributed along the surrounding towns or traffic line.The suitable area included a large potential lands in the site conditions or synthesis grade.The remediation area wasaffected by serious heavy metal pollution, and was lower synthesis grade and poor site condition.The results will improve the methods and techniques system of permanent basic farmland delineation in county scales, and provide a support to coordinate the relationship between cultivated land protection and economic development.