Guillaume Charrier, Nicolas Martin-Stpaul, Claire Damesin, Nicolas Delpierre, Heikki Hänninen, José Torres-Ruiz, Hendrik DaviPlease use the format "First name initials family name" as in "Marie S. Curie, Niels H. D. Bohr, Albert Einstein, John R. R. Tolkien, Donna T. Strickland"
In temperate, boreal and alpine areas, the edges of plant distribution are strongly affected by abiotic constraints. For example, heat waves and drought are major constraints at low latitude and elevation while cold and frost are key factors at high latitude and elevation. Over the next few decades, climate variability is expected to increase, enhancing the probability of extreme events and thus the potential stress imposed by abiotic constraints. Moreover, the likelihood of co-occurring and successive constraints, such as drought and frost, could increase in parallel. It is likely that initial exposure to a first constraint would affect the vulnerability to a subsequent one. Three integrative physiological processes, namely water status, carbon status and the timing of phenological stages, are crucial to understanding how trees will respond to these stress
factors. Although these processes have largely been studied alone, in response to a single constraint, their interaction has rarely been investigated. In this paper, we have examined how water and carbon status interact with the growth cycle and affect both the vulnerability and the exposure to climatic constraints via two different focuses: (i) How would the interaction of frost and drought constraints modulate the vulnerability to a subsequent constraint? (ii) How vulnerability to a given constraint and phenology interact? In the light of numerous papers, we suggest that the interaction between frost and drought constraints should in the short-term influence water status and, in the longer term, the carbon status, both consequently affecting further vulnerability, potentially leading to a decline. This vulnerability can also be modulated by a shift in the annual phenological cycle induced by a previous constraint. Furthermore, we have identified significant gaps of knowledge in the ecophysiological tree response to interacting stresses based on three major points: (i) the spatio-temporal variation in carbohydrate composition, fluxes and allocation in relation to environmental drivers, (ii) the spatio- temporal variation in water content, water and osmotic potentials, (iii) the modulation of phenological processes in response to stress. This framework can help to improve the current process based models and to identify interactions that needs to be better described in order to obtain a more quantitative and dynamic view of drought and frost vulnerabilities integrating the life history of the individual plant.
Abiotic stress, Acclimation, Carbon availability, Drought, Frost, Phenology, Risk assessment, Tree ecophysiology, Water balance
