Tropical monsoon forest in Yunnan with comparison to the tropical rain forest

Abstract

In Chinese botanical literature,the term "tropical monsoon forest" is explained and used inconsistently and is of-ten confused with tropical rain forest.My objective is to clarify differences between the two forests.Schimper defined tropical monsoon forest as being more or less leafless during the dry season and considered it a transi-tional vegetation type between tropical rain forest and savanna in terms of physiognomy and distribution.I com-pared tropical monsoon forest and rain forest in physiognomy,floristic composition and geographical elements to describe and characterize the monsoon forest in Yunnan,China.The tropical monsoon forest in Yunnan occurs mainly on river banks and in basins of several large rivers below 1 000 m altitude.The forest has one or two tree layers,and trees of at least the top layer are deciduous in the dry season.In life forms,the forest is rich in hemicryptophytes and relatively rich in geophytes and therophytes,but less rich in woody lianas and almost lacks megaphanerophytes and chamaephytes compared to tropical rain forest.In leaf size and form,the forest has more microphyllous leaves and compound leaves (24% and 44% of tree species,respectively) than tropical rain forest.In terms of floristic elements,the forest has a greater percentage of species of pantropic distribution (30% of the genera) and tropical Asia and tropical Africa disjunct distribution than tropical rain forest.Thus,the tropical mon-soon forest in Yunnan has more diverse geographical elements in its flora and a complicated evolution history.