TIAN Chao1,YANG Xin-bing1,LI Jun1,2,LU Shao-wei3,LIU Yang1,BI Ke-jiao1(1.Agricultural University of Hebeii,Baoding,Hebei 071000,2.Mulan Forestry Administration of Hebei Province,Weichang,Hebei 068450,3.Institute of Forestry and Pomology of Beijing Academy of Agriculture and Forestry Sciences,Beijing 100093)