Ecohydrological travel times derived from in situ stable water isotope measurements in trees during a semi-controlled pot experiment

Abstract. Tree water uptake processes and ecohydrological travel times have gained more attention in recent studies. In situ measurement techniques for stable isotopes offer great potential to investigate these but not been applied much tree xylem soils so far. Here, we used probes isotope measurements monitor the isotopic signatures of soil before after two deuterium-labeled irrigation experiments. To show method, tested our approach with 20-year-old trees three different species (Pinus pinea, Alnus incana Quercus suber). They were planted large pots homogeneous order semi-controlled experimental conditions. Additional destructive sampling plant material allowed a comparison between (cryogenic vacuum extraction direct vapor equilibration) measurements. Furthermore, isotope-tracer-based compared derived from sap flow The time first arrival tracer signals at 15 cm stem hight ca. 17 h all matched well sap-flow-based times. However, 150 height tracer-based differed ranged 2.4 3.3 d. Sap-flow-based 1.3 d longer than signature notably, which suggests that types sampled pools. consistent (on average standard deviations smaller by 8.4 ‰ ?2H 1.6 ?18O measurements) also among same pot methods 7.8 ?18O, respectively). Our study demonstrates large-scale experiments very frequent monitoring It shows differences or sensor need be considered when comparing results studies within one using methods.