1. Institute of Agricultural Resource and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China
2. Institute of Plant Nutrition, Resource and Environment, Beijing Academy of Agriculture and Forestry Science, Beijing 100097, China
3. Beijing Cultivated Land Construction and Protection Center, Beijing 100029, China
4. Department of Bioresource Engineering, McGill University, Sainte-Anne-de-Bellevue, QC H9X 3V9, Canada
5. Cultivated Land Quality Monitoring and Protection Center, Ministry of Agriculture and Rural Affairs, Beijing 100125, China