In tropical forests, trees and lianas grow to tall statures to display their leaves for light capture in the exposed upper forest canopy. Large lianas and trees in the forest canopy are challenged by hydraulic and mechanical failures and need to balance hydraulic conductivity, hydraulic safety and mechanical safety.
In a recent issue of journal Tree Physiology, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and Wageningen University showed that liana and tree branches diverged in mechanical design due to fundamental differences in wood formation, but similar in hydraulic design.
The researchers sampled and measured branches from 22 species at a canopy crane in a seasonal tropical lowland rain forest in Xishuangbanna.
To evaluate trade-offs and differences between lianas and trees, the researchers quantified the hydraulic conductivity from the xylem-specific hydraulic conductivity (KS), hydraulic safety from the cavitation resistance (P50) and mechanical safety from the modulus of rupture (MOR). They also measured a number of anatomical features that may influence those three functional traits.
They found that there were no clear trade-offs between hydraulic conductivity, hydraulic safety and mechanical safety across exposed canopy distal branches in trees and lianas. Liana canopy distal branches better resist branch breakage against mechanical forces than tree canopy branches.
Moreover, lianas and trees were as groups similar in hydraulic performance; and the mechanisms that drive KS, P50 and MOR may differ between lianas and trees.
CHEN Yajun Ph.D
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China