1. Key Laboratory of Arable Land Conservation (North China), Ministry of Agriculture, College of Land Science and Technology China Agricultural University Beijing China
2. Department of Agroecology Aarhus University Tjele Denmark
3. Department of Environmental Science The University of Arizona Tucson Arizona USA
4. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Sciences Chinese Academy of Sciences Nanjing China
5. Division of Agricultural and Environmental Sciences, School of Biosciences University of Nottingham Leicestershire UK