Hydraulic traits are coordinated with maximum plant height at the global scale

Authors: LIU, HUI - Chinese Academy Of Sciences; Gleason, Sean; HAO, GUANGYOU - Chinese Academy Of Sciences; HUA, LEI - Chinese Academy Of Sciences; HE, PENGCHENG - Chinese Academy Of Sciences; GOLDSTEIN, GUILLERMO - Universidad De Buenos Aires; YE, QING - Chinese Academy Of Sciences

Submitted to: Science Advances
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2018
Publication Date: 2/13/2019
Citation: Liu, H., Gleason, S.M., Hao, G., Hua, L., He, P., Goldstein, G., Ye, Q. 2019. Hydraulic traits are coordinated with maximum plant height at the global scale. Science Advances. 5(2):1-14. https://doi.org/10.1126/sciadv.aav1332.
DOI: https://doi.org/10.1126/sciadv.aav1332

Interpretive Summary: Plants must transport water from the soil to the sites of photosynthesis in the leaves. For tall plants, the height to which water must be lifted represents a significant obstacle. As such, it is possible that the maximum height (Hmax) of plant species is limited by the investment in vascular plant tissue and the resistance of this tissue to dysfunction. However, little is known about the relationships between water transport traits and plant height across terrestrial ecosystems, particularly whether Hmax represents a compromise to reach high light habitats whilst also transporting water without significant risk of failure. We compiled a dataset of Hmax and 11 hydraulic traits of 1368 woody species from 378 sites worldwide. We found that taller species tended to occur in wetter regions, and avoided damage to their water transport tissues by making these tissues more efficient. However, taller stature and greater water transport efficiency were associated with greater susceptibility to damage at low water potential (tension existing within the water transport tissues), lower wood density, wider and fewer conduits, and presumably, a greater capacity to store water in stems and branches. Our results suggest that Hmax is has been coordinated by natural selection to achieve the efficient transport of water, but also to avoid significant failure of the water transport pathway.

Technical Abstract: Maximum plant height (Hmax) could be limited by hydraulic functioning because water must be transported longer distances in taller plants. However, little is known about the relationships between hydraulic traits and plant height across terrestrial ecosystems, particularly whether Hmax reflects an optimization of hydraulic efficiency and safety. We compiled a dataset of Hmax and 11 hydraulic traits of 1368 woody species from 378 sites worldwide. We found that taller species tended to occur in wetter regions, and avoided low xylem water potentials by achieving high xylem hydraulic efficiency. Taller stature and greater xylem efficiency were associated with greater susceptibility to embolism (lower hydraulic safety), lower sapwood density, wider and less dense conduits, and presumably, greater hydraulic capacitance. Our results suggest that xylem traits, hydraulic functioning, and Hmax represent a coordinated axis of variation, aligned primarily with water availability, extending our understanding of species sorting processes across a broad range of taxa, climates, and habitats.