Weak coordination between leaf drought tolerance and proxy traits in herbaceous plants

© 2021 The Authors.
Increased drought is predicted to have a major impact on plant performance under environmental change. Yet leaf hydraulic traits directly related to drought tolerance, such as leaf turgor loss point (π), are under-represented in trait-based studies and have been largely overlooked within the main frameworks evaluating trait–trait coordination and trade-offs—the leaf economics spectrum (LES) and the global spectrum of plant form and function. Using 122 herbaceous species from the Central European temperate grasslands, we investigated (a) the coordination between π and traits often used as proxies for drought tolerance, namely SLA, leaf area (LA), leaf dry matter content (LDMC), leaf thickness (LT), plant height and intrinsic water use efficiency (iWUE); (b) whether the strength of the trait–trait relationships differed across plant functional types (PFTs: graminoids and forbs) and depended on species phylogeny; and (c) whether single or multiple traits, combined with either PFTs or phylogenetic relatedness, provide a good prediction of π. A more negative π (higher leaf drought tolerance) was coordinated with higher LDMC and higher iWUE. This pattern was consistent among PFTs and also after accounting for phylogenetic relatedness. However, the coordination of π with other traits was weak. For LT and height, it was driven by the differences between PFTs. For SLA and LA, it was only observed after accounting for phylogenetic relatedness. The most parsimonious model predicting π as a function of other traits retained LDMC and LA (adj. R = 0.37). Since π showed a strong phylogenetic signal, accounting for the influence of phylogenetic relatedness further improved π prediction by 17%. In herbaceous temperate plants, there is relatively weak coordination between leaf drought tolerance (π) and traits representing key dimensions of the LES and the global spectrum of plant form and function. None of the proxy traits considered here, alone or in combination, provided a strong prediction of π across a large number of grassland plant species. Therefore, our work emphasizes the need for direct measurements of leaf hydraulics when estimating plant drought responses to better understand and predict species responses to environmental change. A free Plain Language Summary can be found within the Supporting Information of this article.
This study was supported by the project GAČR 20-08900S funded by Czech Science Foundation, the project RVO 67985939 funded by the Czech Academy of Sciences and the projects VEGA 2/0096/19 and 2/0147/21 funded by the Slovak Science Foundation. A.J.A. was funded by the Hungarian Eötvös Scholarship, J.D. and P.L. were supported by the MSMT INTER-EXCELLENCE project (LTAUSA18007) and F.d.B. was supported by the Plan Nacional de I + D + i (project PGC2018-099027-B-I00). The authors thank Adam Martin, Kevin Mueller and an anonymous reviewer for helpful comments on the previous versions of the manuscript. Open Access funding enabled and organized by Projekt DEAL. WOA Institution: Eberhard Karls Universitat Tubingen, Blended DEAL: Projekt DEAL.