1. College of Life Sciences, Shanxi Normal University, Taiyuan 030031, China
2. Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, China
3. State Key Laboratory of Efficient Utilization of Arid and Semi-Arid Arable Land in Northern, Beijing 100081, China
4. College of Horticulture, Jilin Agricultural University, Changchun 130118, China