A new paper led by Adrià Barbeta is currently under review in Hydrology and Earth System Sciences discussion. In this paper, we investigated plant-water sources of an emblematic refugial population of Fagus sylvatica in the Ciron river gorges in South-Western France using stable isotopes. Using Bayesian isotope mixing models (MixSIAR), we then quantified the contribution of the considered sources to xylem water. Although xylem water 18O could always be interpreted as a mixture of deep and shallow soil waters, the 2H of xylem water was often more depleted than any other possible water source. We argue that an isotopic fractionation in the unsaturated zone and/or within the plant tissues could underlie this unexpected 2H depletion of xylem water. For more information, see here.
Discussion paper on the tree water source identification using stable water isotopes