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 SUREAU (Hydraulic Safety and Drought Resistance of Trees)

Leader : Stéphane HERBETTE

SUREAU staff

The SurEau team is analyzing the hydraulic functioning of trees and its link with severe droughts that can lead to their decline. 

Climate models predict an increase in the intensity and frequency of severe droughts, but little is known about the responses of trees, and more generally of ecosystems, to these events. Sap flows under tension in the xylem, and under the threat of cavitation (sap vaporization) when a drought exacerbates these tensions. This leads to a loss of xylem conductance, i.e. embolism. If embolism is too high, the organs are no longer supplied with water. The hydraulic safety of the tree thus plays a key role during severe droughts and it is on this process that the team focus its research efforts.  The main scientific objective of the SurEau team is to predict the risks of hydraulic failure leading to tree dieback, according to climate change scenarios.

To formulate hypotheses on these risks of hydraulic failure, we have the SurEau model. The development of this model was an opportunity to reconsider the resistance to drought by moving from an intensity scale (water potential) to a duration scale. Thus, understanding this resistance as the capacity to delay hydraulic failure leads us to reconsider the contribution of hydraulic safety traits. Assessing the role of these traits also implies characterizing their variability, especially in a changing climate context. Furthermore, to refine the model predictions, we need to elucidate the mechanisms of tree mortality and the link with hydraulic dysfunction.

The team is also developing original tools (Xyl'em, Cavitron, irrigation control, Drought-box) and acquiring others (microtomograph, optical method for measuring cavitation) to drive projects on the science front. Some of these tools are integrated into the Phenobois platform (Phenotyping of physico-chemical properties of wood and hydraulics of trees) of INRAE.

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