Woody plant adaptations to multiple abiotic stressors: Where are we?*

Interacting abiotic stresses exert a fundamental selective pressure on the adaptive syndromes of long-living organisms such as woody plants. However, general patterns and mechanisms describing woody plant adaptations to tolerate multiple abiotic stressors are yet to emerge. This hampers our ability to build predictive frameworks foreseeing species responses to stochastic changes in abiotic stress regimes due to climate change. With this Virtual Special Issue (VSI), we aimed to summarize what we know, and what we do not know, about woody plant adaptations to achieve tolerance to multiple abiotic limitations. To this end, we brought together studies exploring ecological or ecophysiological perspectives on woody plant adaptations to tolerate multiple abiotic stresses. Ecological studies suggest patterns associating trait trade-offs, climate, and biotic interactions with woody plants' multi-stress tolerance. Ecophysiological studies point to traits and conceptual frameworks that might explain some processes underpinning woody plant multi-stress tolerance. Here, we first revised the definitions of stress and stress tolerance used in ecological and ecophysiological research, providing a nomenclature of tolerance that could be used to unify definitions across research fields. Then, we summarized the main theories and evidence on woody plant adaptations to tolerate multiple abiotic stresses. Finally, we introduced the ecological and ecophysiological perspectives on this matter and placed the contributions to this VSI within the current state of the art. Altogether, this VSI allowed us to identify the lack of large-scale integration of patterns and processes describing woody plant adaptations to multiple abiotic stresses as a major gap in this field.