[en] Recent work compared six plant water extraction approaches for hydrogen and oxygen stable isotope analysis. Previously it was believed that these ex- traction approaches would provide analytes whose δ²H and δ¹⁸O values were similar, but the authors found significant differences in the isotopic composition of the produced analytes. We report a short followup experiment to specially explore systematic differences between one form of cryogenic vacuum distillation (hereafter CVD-2 from, based on Koeniger et al.[2]), and direct vapour equilibration (DVE[3, 4]).

[en] Using stable isotope data from soil and vegetation xylem samples across a range of landscape positions, this study provides preliminary insights into spatial patterns and temporal dynamics of soil-plant water interactions in a humid, low-energy northern environment. Our analysis showed that evaporative fractionation affected the isotopic signatures in soil water at shallow depths but was less marked than previously observed in other environments. By comparing the temporal dynamics of stable isotopes in soil water mainly held at suctions around and below field capacity, we found that these waters are not clearly separated. The study inferred that vegetation water sources at all sites were relatively constant, and most likely to be in the upper profile close to the soil/atmosphere interface. The data analyses also suggested that both vegetation type and landscape position, including soil type, may have a strong influence on local water uptake patterns, although more work is needed to explicitly identify water sources and understand the effect of plant physiological processes on xylem isotopic water signatures. - Highlights: • Plant-soil-water interactions in the temperate humid North are relatively unknown. • Stable isotopes of soil and vegetation water revealed spatio-temporal patterns. • In contrast to other biomes, we found little separation between soil water sources. • Vegetation sources were constant temporally, but variable with landscape position.