喜马拉雅东部雅鲁藏布江大峡湾河谷地区种子植物区系的性质和近缘关系

中国西藏墨脱雅鲁藏布江大峡湾河谷地区（海拔2500m以下热带亚热带山地）属东喜马拉雅山地的一部分，在区系亲缘上属印度东北部阿萨姆喀西山和那加山以及尼泊尔等东喜马拉雅地区区系的一部分；其热带成分与我国云南南部的西双版纳也有较为密切的联系，这是第三纪以来印度－马来成分沿中南半岛迁移和交流的结果．也与同二者在地理上密切相连有关.在植物区系区划上，本地区山地基带植被是一种由热带植被向亚热带植被水平过渡的具有浓郁亚热带特色的半常绿雨林，但其典型的印度－马来成分仍然有限，而泛北极的中国－喜马拉雅成分占优势，并拥有东亚或中国－喜马拉雅的特征科属；因此墨脱雅鲁藏布江大峡湾地区应归入泛北极植物区中的东喜马拉雅植物地区

THE PHYTOGEOGRAPHICAL AFFINITIES AND NATURE OF THE BIG BEND GORGE OF THE YALU TSANGPO RIVER, S. E, TIBET, E. HIMALAYAS

The phytogeographical affinities and florisitic nature of the big bend gorge (tropical and subtropical mountainous region below 2 500 m) of the Yalu Tsangpo River,S. E. Tibet. E. Himalayas were studied. The results showed that the flora of the region was a part of E. Himalayas and had the same or similar original background and close phytogeographical affinities to Assam,N. Myanmar,Nepal and other regions of E. Himalayas: the tropical elements there were also closely related to those in Xislauangbanna, S. Yunnan. This was resulted from that since the Tertiary period the Indo--Malayan elements had been dispersing and exchanging along the Indo--Sino Peninsular to Himalayas ,and that the regions were closely connected geographically. As for phytogeographical division. the climax vegetation along the base areas of the gorge of E. Himalayas belonged to semi-evergreen rain forest with strong tropical charecters which was a horizontal transitional type from typical tropical forest to subtropical forest. The typical Indo--Malayan tropical elements occurring in the forest were still limited, but the Sino--Himalayan elements were dominant. In addition, many families and genera typical of the E. Asia were found in the region. So the region should still belong to. E. Himalayan region, Holarctis.