The structure characteristics and dominant population regeneration types of Tsuga tchekiangensis communities in the Jiulongshan National Natural Reserve of Zhejiang Province The Niche Characteristics of Endangered Plant Tsuga tchekiangensis in Jiulongshan National Nature Reserve of Zhejiang Province Study on the Dynamics of the Endangered Plant Population of Tsuga tchekiangensis POPULATION QUANTITATIVE CHARACTERISTICS AND DYNAMICS OF RARE AND ENDANGERED TSUGA TCHEKIANGENSIS IN JIULONGSHAN NATURE RESERVE OF CHINA