Models of tree–grass coexistence in savannas make different assumptions about the relative performance of trees and grasses under wet vs dry conditions. We quantified transpiration and drought tolerance traits in 26 tree and 19 grass species from the African savanna biome across a gradient of soil water potentials to test for a trade‐off between water use under wet conditions and drought tolerance. We measured whole‐plant hourly transpiration in a growth chamber and quantified drought tolerance using leaf osmotic potential (Ψosm). We also quantified whole‐plant water‐use efficiency (WUE) and relative growth rate (RGR) under well‐watered conditions. Grasses transpired twice as much as trees on a leaf‐mass basis across all soil water potentials. Grasses also had a lower Ψosmthan trees, indicating higher drought tolerance in the former. Higher grass transpiration and WUE combined to largely explain the threefold RGR advantage in grasses. Our results suggest that grasses outperform trees under a wide range of conditions, and that there is no evidence for a trade‐off in water‐use patterns in wet vs dry soils. This work will help inform mechanistic models of water use in savanna ecosystems, providing much‐needed whole‐plant parameter estimates for African species.
This content will become publicly available on April 10, 2025
Stem water potential (Ψstem) is a key indicator for assessing plant water status, which is crucial in understanding plant health and productivity. However, existing measurement methods for Ψstem, characterized by destructiveness and intermittency, limit its applicability. Microtensiometers, an emerging plant-based sensor, offer continuous monitoring capabilities and have shown success in certain vine and tree species. In this study, we investigate the efficacy of microtensiometers ability to monitor the Ψstemof cotton (
- Award ID(s):
- 2102120
- PAR ID:
- 10529622
- Publisher / Repository:
- Springer
- Date Published:
- Journal Name:
- Irrigation Science
- ISSN:
- 0342-7188
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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