EGU General Assembly 2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Global variation in the ratio of sapwood to leaf area explained by optimality principles

Huiying Xu1,2, Han Wang1, I. Colin Prentice1,3, Sandy P. Harrison1,4, Lucy Rowland2, Maurizio Mencuccini5,6, Pablo Sanchez-Martinez5,7, Pengcheng He8, Ian J. Wright9,10, Stephen Sitch2, and Qing Ye8
Huiying Xu et al.
  • 1Tsinghua Univeristy, Department of Earth System Science, Beijing, China (
  • 2Department of Geography, University of Exeter, Exeter, UK
  • 3Georgina Mace Centre for the Living Planet, Department of Life Sciences, Imperial College London, Ascot, UK
  • 4School of Archaeology, Geography and Environmental Sciences (SAGES), University of Reading, Reading, UK
  • 5CREAF, Campus UAB, Barcelona, Spain
  • 6ICREA, Barcelona, Spain
  • 7Universitat Autònoma de Barcelona, Barcelona, Spain
  • 8South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China
  • 9Hawkesbury Institute for the Environment, Western Sydney University, New South Wales, Australia
  • 10School of Natural Sciences, Macquarie University, NSW, Australia

The sapwood area supporting a given leaf area (vH) reflects a coordinated coupling between carbon uptake, water transport and loss at a whole plant level. Worldwide variation in vH reflects diverse plants strategies adapt to prevailing environments, and impact the evolution of global carbon and water cycles. Why such a variation has not been convincingly explained yet, thus hinder its representation in Earth System Models. Here we hypothese that optimal vH tends to mediate between sapwood conductance and climates so that leaf water loss matches both sapwood hydraulics and leaf photosynthesis. By compiling and testing against two extensive datasets, we show that our hypothesis explains nearly 60% of vH variation responding to light, vapor pressure deficit, temperature, and sapwood conductance in a quantitively predictable manner. Sapwood conductance or warming-enhanced hydraulic efficiency reduces the demand on sapwood area for a given total leaf area and, whereas brightening and air dryness enhance photosynthetic capacities consequently increasing the demand. This knowledge can enrich Earth System Models where carbon allocation and water hydraulics play key roles in predicting future climate-carbon feedback.

How to cite: Xu, H., Wang, H., Prentice, I. C., Harrison, S. P., Rowland, L., Mencuccini, M., Sanchez-Martinez, P., He, P., Wright, I. J., Sitch, S., and Ye, Q.: Global variation in the ratio of sapwood to leaf area explained by optimality principles, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1764,, 2023.

Supplementary materials

Supplementary material file