Delayed effect of drought on xylem vulnerability to embolism in Fagus sylvatica

Understanding variation in drought resistance traits is needed to predict the potential of trees to adapt to severe drought events. Xylem vulnerability to embolism is a critical trait related to drought-induced mortality that has large variability between species. Acclimation of this trait to environmental conditions implies changes in the xylem structure and organization, leading previous studies to investigate its variations under conditions that preserve growth. In European beech (Fagus sylvatica L.) saplings, we assessed the effect of drought on the species' vulnerability to embolism in branches developed the next year during recovery. Newly formed branches displayed less vulnerability to embolism in plants that experienced the most severe droughts that led to native embolism. The pressure that induced 50% loss of conductance in severely drought affected plants versus control plants was similar to 3.98 versus similar to 3.1 MPa, respectively. These results argue for a lagged acclimation of this trait to drought events.