1. University of Copenhagen Department of Plant & Environmental Sciences Højbakkegård allé 13 DK–2630 Tåstrup Denmark
2. University of Chinese Academy of Sciences Sino-Danish Center for Education and Research (SDC) 380 Huaibeizhuang, Huairou district Beijing China
3. Chinese Academy of Sciences State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil Science 210008 Nanjing China
4. University of Copenhagen Department of Plant & Environmental Sciences Thorvaldsensvej 40 DK–1821 Frederiksberg Denmark