Global variation in the ratio of sapwood to leaf area explained by optimality principles
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
• The sapwood area supporting a given leaf area (Huber value, vH) reflects the coupling between carbon uptake and water transport and loss at a whole-plant level. Geographic variation in vH presumably reflect plant strategic adaptations but the lack of a general explanation for such variation hinders its representation in vegetation models and assessment of how its impact on the global carbon and water cycles.
• Here we develop a simple hydraulic trait model to predict optimal vH by matching stem water supply and leaf water loss, and test its performance against two extensive plant hydraulic datasets.
• We show that our eco-evolutionary optimality-based model explains nearly 60% of global vH variation in response to light, vapour pressure deficit, temperature and sapwood conductivity. Enhanced hydraulic efficiency with warmer temperatures reduces the sapwood area required to support a given leaf area, whereas high irradiance (supporting increased photosynthetic capacity) and drier air increase it.
• This study thus provides a route to modelling variation in functional traits through the coordination of carbon uptake and water transport processes.
• Here we develop a simple hydraulic trait model to predict optimal vH by matching stem water supply and leaf water loss, and test its performance against two extensive plant hydraulic datasets.
• We show that our eco-evolutionary optimality-based model explains nearly 60% of global vH variation in response to light, vapour pressure deficit, temperature and sapwood conductivity. Enhanced hydraulic efficiency with warmer temperatures reduces the sapwood area required to support a given leaf area, whereas high irradiance (supporting increased photosynthetic capacity) and drier air increase it.
• This study thus provides a route to modelling variation in functional traits through the coordination of carbon uptake and water transport processes.
Date Issued
2026-04-01
Date Acceptance
2025-12-16
Citation
New Phytologist, 2026, 250 (1), pp.181-193
ISSN
0028-646X
Publisher
Wiley
Start Page
181
End Page
193
Journal / Book Title
New Phytologist
Volume
250
Issue
1
Copyright Statement
Copyright © 2026 The Author(s). This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
License URL
Publication Status
Published
Date Publish Online
2026-01-28