When trees get dehydrated, they suffer in terms of growth and survival. Tree dehydration is particularly problematic during droughts and heat waves like the one that Louisiana experienced during the summer of 2023. An often-overlooked source of tree water loss that leads to dehydration is through the bark. Although trees are covered in bark, its leakiness to water vapor, or permeability, is not well understood. Recently, Yinuo Zhou (Ph.D.; Wolfe) and her collaborators showed that bark permeability ranges widely among Louisiana tree species and that it can be affected by disturbances such as wind and flooding. The results were recently published in Tree Physiology and can be read at Bark water vapor conductance varies among temperate forest tree species and is affected by flooding and stem bending | Tree Physiology | Oxford Academic.

Zhou found that tree species growing at the LSU AgCenter’s Botanic Gardens at Burden varied five-fold in how leaky their branches were to water vapor. When she bent branches to simulate the effects high winds, bark permeability increased on average by 23%. When she subjected saplings to flood conditions, bark permeability was not affected until 69 days post flood, when it was reduced by 41%. Perhaps the flooded saplings became dormant sooner than unflooded saplings, leading to waxy deposits that reduced bark permeability. Clearly there are complex drivers of variation in bark permeability, including interacting effects of disturbances.

Currently, Zhou is exploring novel methods for measuring bark permeability and investigating the underlying bark traits that determine permeability. This series of research projects will hopefully fill the knowledge gap regarding water loss through bark and tree dehydration. The results can help us better predict the effects of extreme weather events on tree performance and lead to improved forest management.

Yinuo Zhou exams bark traits on a branch segment.