Trade-offs among leaf toughness, constitutive chemical defense, and growth rates in oaks are influenced by the level of leaf mass per area

Key message Among the variety of leaf defensive strategies to counteract herbivory attacks, the oak species analyzed in this study maximize investment in no more than one, with high-LMA oaks developing very tough leaves and low-LMA oaks favoring between high concentrations of condensed tannins or high growth rates.Context Plants develop a variety of defense strategies to counteract herbivory attacks, from physical and chemical defenses to tolerance strategies. Tradeoffs between strategies have been widely assessed from a resource allocation perspective, but there is a need to consider eventual interactions among them.Aim We evaluate the among-species tradeoff between three main constitutive plant defense traits, while considering the leaf mass per area ratio (LMA) as a proxy of leaf construction investment on area basis. Methods Leaf toughness measured as work of fracture, condensed tannins, and relative growth rate (RGR) were analyzed in a set of 19 Quercus L. species with contrasting LMA.Results Most species had low values either in two or in the three traits analyzed. Moreover, the highest values of work of fracture appeared in the species with high LMA; the highest values of condensed tannins were found in the species with the lowest LMA; and high values of RGR were measured in species with intermediate or lower values of LMA.Conclusion Oaks showed a trade-off among leaf defensive strategies influenced by LMA. Oaks with high LMA developed very tough leaves while oaks with low LMA presented lower values of toughness but favored between one of the two other strategies.

Automated summary

This study examines the leaf defensive strategies of oak species and finds that the leaf toughness of oaks is correlated with leaf density, with high-density oaks having tougher leaves and low-density oaks favoring either high concentrations of condensed tannins or high growth rates.