雅鲁藏布江中游沙地植物区系特征

从雅鲁藏布江中游沙地植物区系的地理成分来看，其特有种非常丰富。在82个主要建群种和常见伴生种中，有31种为特有种，而且这些特有种大都是新近从邻近植物区系中分化出来的，但特有属很少或几乎没有。这说明，本区沙地植物区系是一个年轻的区系。本区沙地植物区系成分还表明，它既不完全是一个衍生的区系，也不完全是就地起源的，而是以东亚区系为主，在青藏高原的隆升过程中，发生了其邻近植物区系成分的迁移和渗透。

FLORISTIC FEATURES OF SAND VEGETATION IN THE MIDDLE REACHES OF THE YARLUNG ZANGBO,XIZANG (TIBET)

The floristic features of the sand vegetation in the middle reaches of the Yarlung Zhangbo River are discussed. From the geographic elements of the floristic it can be seen that the endemic species are quite rich. Among 82 main edificatos and common companions, 31 species are endemics, and most of them are neoendemics, which have differentiated from their ancestors in the adjacent floras,but there is almost no endemic genus. It indicates that the sand flora is a new and young one. The floristic elements also show that the flora is neither totally derived nor entirely native,and it has formed based on the East-Asian element. Meanwhile,the migration and percolation of the adjacent floristic elements have taken place during the lift of the Qinghai-Xizang Plateau.