DIPTEROCARP FORESTS AND THEIR GEOGRAPHICAL DISTRIBUTION IN YUNNAN PROVINCE, CHINA

The Southern Yunnan is the edge part of Asian tropics, its area with tropical environment is about 4700km² , covering 1.23% of the whole province.There are 5 genera, 8 species and 1 variety of Dipterocarpplants discovered in the region.Further more, Parashorea chinensis and Hopea jianshu are the endemic species of Yunnan.In Southern, Southeastern and Southwestern Yunnan, 5 types of Dipterocarpforests are distributed.They are P.chinensisforest, Vatica fleuryanaforest, D.turbinatusforest, Shorea assamicaforest and D.retusus-H.mollissimaforest.The last type is the humid rain forest with most tropical ecological characteristics in China, and it is a geographical variety of Southeastern Asian rain forest.The other 4 types belong to the tropical seasonal rain forests.These 5 types of Dipterocarpforests have a similar genus and family composition with the Southeastern Asian flora, but they are formed with a single or a few dominant species marked with a multi-layer stand structure.The existence of them demonstrates the relations between the Dipterocarpforests in Southern Yunnan and the tropical forests in tropical Asia, and the forests in Southern Yunnan are the edge types of the tropical Asian forests, which expand in the east and north directions.