Yuanqiao Li¹, Xiuchen WU¹, Yongmei Huang², Xiaoyan Li¹, Fangzhong Shi¹, Shoudong Zhao², Yuhong Tian¹, Pei Wang¹, Shulei Zhang², Cicheng Zhang¹, Yang Wang², Chongyang Xu³ and Pengwu Zhao⁴, (1)Beijing Normal University, Faculty of Geographical Science, Beijing, China, (2)Beijing Normal University, Beijing, China, (3)Peking University, Beijing, China, (4)Inner Mongolia Agricultural University, College of forestry, Hohhot, China