1.Key Lab.of Soil & Water Conservation and Desertification Combating,Ministry of Education,Beijing Forestry University,100083,Beijing;2.College of Resources and Environment,Northwest A & F University,712100,Yangling,Shaanxi;3.Forestry Bureau of Huanglong Mountain,715700,Huanglong,Shaanxi;4.Institute of Germ Plasm Resources,Academy of A & F Science of Ningxia,750002,Yinchuan,Ningxia: China