With an aim to understand the structure and composition of the understory treelets in Xishuangbanna tropical forest, Assoc. Prof. Tang Jianwei and his student of XTBG investigated species richness, floristic composition, and structure of understory treelets in three 1-ha plots. The study was conducted in the undistrubed tropical seasonal rain forest of Xishuangbanna (21°08′–22°36′ N and 99°56′–101°50′ E), SW China.

The authors investigated all the woody species except lianas in the three plots, compared the differences of species diversity of trees and treelets in those plots and the differences of understory structure between that forest and the typical dipterocarp forests in SE Asia. They found 5089 individuals belonging to 356 species, 189 genera, and 63 families in the three plots. The five most important families were Rubiaceae, Euphorbiaceae, Lauraceae, Meliaceae, and Annonacae.

The treelet layer was much more diverse than the tree layer, indicating that result based only on trees may be not an appropriate representation of the diversity status of a particular tropical forest type. When the treelet layer was considered, the three plots were more similar than when tree layer was considered.

In contrast with the dipterocarp forests in SE Asia, the understory of tropical seasonal rain forest was mainly composed of the trees with small and middle stature at maturity classes.

The research results indicate that the structure of tropical forest understory may differ not only among continents but also within continent.

The study has demonstrated that the species diversity of treelets (2 cm ≤ DBH < 10 cm) is much higher than that of the trees (DBH ≥ 10 cm) in the tropical seasonal rain forest in Xishuangbanna.

Related research observation has been published in Forest Ecology and Management, 260 (4): 565-572, doi:10.1016/j.foreco.2010.05.013 .