Abstract: The paper presented the characters of tropical forests and their secondary succession series in the Big Bend Gorge of Yalu Tsangpo River, S.E.Tibet, E.Himalayas. In the region the tropical forests occur in the bottom of the gorge at an altitude between 600-1200 m, which belong to the low mountain semi-evergreen tropical rain forests, and include mainly three types as follows: Altingia excelsa+ Terminalia myriocarpe forest; Altingia excelsa+ Lagerstroemia mimuticar pa forest and Altingia excelsa forest. The natural and artificial factors causing the destruction of the original vegetation were discussed. The factors led to two different secondary succession series of the semiuevergreen tropical rain forest.

Key words: Yalu Tsangpo river

摘要： 对雅鲁藏布江大峡弯河谷地区热带森林植被情况进行了调查分析。论述了造成该地区热带植被概况及其被破坏的自然因素和人为因素。并对该地区植被在次生演替的各个时期植被种类成分的变化，群落结构，建群种生长速度等进行比较研究，结果如下：A．自然因素导致的次生演替主要经历了下列 6个价段：（1）尼泊尔桤木（Alnus nepalensis）阶段;（2）尼泊尔桤木单优群落阶段；（3）原生植被主要树种侵入阶段；（4）尼泊尔桤木林衰退阶段；（5）原生植被恢复阶段；（6）原生植被建立阶段。B．人为因素导致的次生演替主要经历有下列5个阶段：（1）高大禾草或热带高草阶段；（2）野芭蕉侵入生长阶段；（3）喜阳树种侵入或恢复生长阶段；（4）杂木林阶段；（5）原生植被恢复及建立阶段。最后讨论了植被次生演替规律对自然植物区系的影响和对治理山地，保护该地区生物多样性，合理利用资源及发展生产的重要性及意义。

关键词: 雅鲁藏布江, 热带森林, 演替