1. Jilin Provincial Laboratory of Grassland Farming, Changchun, China
2. Northeast Institute of Geography and Agroecology Chinese Academy of Sciences, Changchun, China
3. College of Resource and Environmental Science, Jilin Agricultural University, Changchun, China
4. College of Resources and Environmental Sciences, Gansu Agricultural University, Lanzhou, China
5. Soil Fertilizer Workstation of Changchun City, Changchun, China