Lianas and trees in tropical forests in south China

Lianas are an increasingly important growth form in tropical forests around the world, but are relatively unknown in southeast Asia. In this PhD research some liana communities are described and a number of structural-functional characteritics of lianas are analysed, in most cases comparative to trees. Special attention is put to growth performance and ecophysiological leaf and plant characters in a framework of adaptive ecology.

The liana communities of three common forest types in the tropical-temperate transitional zone at Xishuangbanna, SW China are described. Compared to other tropical Asian tropical forests, the diveristy and abundance of lianas is relativley high in Xishuangbanna.

Two studies where conducted in which a large number of liana and tree species were compared for selected leaf structural and physiological characteritics. In the seasonal tropical forest, lianas have lower leaf structural costs and higher rates of resource capture than trees, supporting the dry season growth advantage hypothesis for lianas. In the strong phosporus-limited montane rainforest, liana species exhibited similar mature and senesced leaf nutrient concentrations and nitrogen resorption efficiencies, but higher litter phosphorus concentrations and less phosphorus resorption efficiencies than tree species.

In greenhouse experimental studied the growth of five Bauhinia species was compared,  three lianas and two trees. Light-demanding lianas grew clearly faster than light-demanding trees. This difference may be explained by morphological plant parameters, such as specific leaf area, leaf mass ratio and leaf area ratio, and not be attributed to higher photosynthetic rates at the leaf level. A shade-tolerant liana exhibited a growth strategy rather different from the light-demanding tree and liana species studied.

Seasonal acclimation in growth and photosynthesis of the seedlings of the liana species, Zizyphus attopensis Pierre, was due to changes in biochemical features and biomass allocation, rather than to changes in leaf morphological features. The local light level is the main factor driving seasonal variations in growth and photosynthesis in the study area.

Additionally, I studied morphological and physiological leaf and whole-plant features of seedlings of six late-successional common woody species differing in adult stature and shade tolerance. Compared with small shrub species, the taller tree species, which are more likely to experience high light during their life span, showed a greater potential for light acclimation. Physiological differences among the four tree species were not consistent with differences in adult stature.

Lianas have growth strategies different from trees in these forests, but do not always follow expected patterns. Additionally, for some characters lianas are far less different from trees than expected. This sheds new light on patterns of adaptive ecology of lianas versus trees in tropical forest.

Keywords: lianas, trees, liana-tree interaction, plant morphology, plant ecophysiology,

growth, biodiversity, south China, Xishuangbanna

Zhi-quan Cai defended his thesis on March 28, 2007

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