1. Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology Chinese Academy of Sciences Harbin 150081 China
2. Univ. of Chinese Academy of Sciences Beijing 100039 China
3. Dep. of Soil Science Univ. of Wisconsin‐Madison Madison WI 53705 USA
4. Nanjing Normal Univ. School of Geography Nanjing 210023 China
5. Dep. of Renewable Resources, 442 Earth Sciences Building Univ. of Alberta Edmonton AB T6G 2E3 Canada