[1] Prof. Li Zhong Qin, Postdoctoral Advisor, State Key Laboratory of Cryospheric Sciences/Tian Shan Glaciological Station, Northwest Institute of Eco-Environment and Resources, CAS, 320 Donggang West Road,
Lanzhou, 730000, China. E-mail: lizq@lzb.ac.cn, Tel: +8613893391417

[2] Prof. Zhang Bo, Ph.D. Advisor, Northwest Normal University, College of Geography and Environmental Science, Anning Road, Lanzhou, 730000, China, E-mail: zhangbo@nwnu.edu.cn, Tel: +8613669369897.

[3] Prof. Awad Osman Abusuwar, M.Sc. Advisor at university of Khartoum, Faculty of Forestry, Shambat, Code 13314, Sudan. Current address: Department of Arid land Agriculture, King Abdul Aziz University,
Jeddah, e-mail: Abusuwar@yahoo.com, Tel +966 564900736

[4] Dr. Elamin Sanjak Mohamed, University of Khartoum, Faculty of Forestry, Shambat, Code 13314, Sudan, E-mail: ssanjak2000@yahoo.com, Tel: +24922691346, Fax: +249185219082