[1] Department of Conservation and Protection of Forest, Faculty of Forestry, University of Khartoum, Khartoum, Sudan, Postal Code: 13314

[2 ]E-mail: yousifelnouryagoub@yahoo.com or yousif@lzb.ac.cn

[3] Fax: +249185219082

[4] Tel: +249 121665105