Even after complete stomatal closure, plants lose water through the leaf cuticles and bark. This residual water conductance of leaves (g_leaf-res) and stems (g_bark) can negatively impact plant water balance and affect plant survival in seasonally dry environments. However, little is known about the costs and benefits associated with such water leaks, especially on stem level.

Here, we characterized the structural and functional determinants of the variability in g_bark across tropical savanna species to elucidate how variations in this trait are related to contrasting growth strategies.

The high variability in g_bark across species was associated with morphoantomical properties of the outer bark (thickness, density, and lenticel investment), and such characteristics influenced both stem transpiration and respiration, suggesting the existence of a trade-off between water conservation and oxygen permeability, which reflected contrasting growth and dehydration tolerance strategies. For instance, species with higher g_bark and g_leaf-res presented a fast resource acquisition strategy but were more prone to drought-induced mortality by hydraulic failure. However, model simulations revealed that the relative contribution of g_leaf-res and g_bark to overall water balance depended on whether leaves were less or more resistant to cavitation than the stems.

Synthesis. By combining correlative studies, experimental results, and a modeling exercise, we provide a new understanding of the costs and benefits associated with the variability in g_bark across tropical savanna species, and a new perspective for studies of water relations and carbon economics in species from a hyperdiverse savanna.

All methods and analyses are explicitely described and provided in the corresponding paper.

Please refer to the corresponding paper published in Journal of Ecology for further details.