In a study published in Plant Diversity, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) report the first record of tropical lowland tall deciduous forest in southern Yunnann, China. They confirm that it represents a pristine and primary example of the tropical tall deciduous forest formation which dominates regions of tropical Asia that experience 5–7 dry months.  

The researchers established four sampling plots of tropical tall deciduous forests in southern Yunnan: one each in deep valleys in the lower Lancang (Upper Mekong) River at Nuozhadu and its tributary at Luozahe, and two in the Red River and its tributary at Luzijiang. 

They studied the floristic composition, physiognomy and biogeography of the tropical deciduous forest in southern Yunnan, SW China. 

They found that the flora of the deciduous forest largely consists of tropical elements (80% of the genera and 70% of the species), providing indisputable evidence that this forest is tropical. Both forests have exceptionally rich evergreen tree flora, consistent with the historical absence of domestic cattle or frequent anthropogenic fire such that, unlike tall deciduous forest in South Asia, their form is unique and possibly aboriginal. 

“The forest types described here are unique due to the exclusive dominance of deciduous species in their closed canopies, yet abundance and diversity of their overwhelmingly evergreen subcanopy,” said Prof. ZHU Hua of XTBG. 

Furthermore, the physiognomy of the forest is correlated more with climate, especially the length of the dry season (November to April), whereas their biogeography shows a connection with the geological and climatic history of these two regions. 

“Our finding that Chinese endemic species are present at higher ratios at the Red River and its tributary than at the lower Lancang River leads us to recommend that conservation priority should be given to the tropical deciduous forest of the Red River and its tributary,” said ZHU Hua. 

Contact 

ZHU Hua Ph.D 

Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, Yunnan 666303, China            

E-mail: zhuh@xtbg.ac.cn    

Tropical deciduous forest at lower Lancang River. (Image by ZHU Hua)  

Tropical semi-deciduous forest at Lvzhijiang tributary of Red River. (Image by ZHU Hua)