Spatial Pattern of Pteroceltis tatarinowii Populations in Langya Moutain of Anhui Province Spatial Patterns and Associations in a Birch-fir Forest in Mt. Taibai Age Structure and Spatial Distirbution Patterns of Taxus yunnanensis Population in Lanping County,Yunnan Province Population structure and spatial patterns for the main tree species in Castanopsis carlesii-Schima superba community in Tiantong, Zhejiang Province, China