Stable isotopes of water reveal differences in plant – soil water relationships across northern environments

We compared stable isotopes of water in plant stem (xylem) and soil collected over a complete growing season from five well-known long-term study sites northern/cold regions. These spanned decreasing temperature gradient Bruntland Burn (Scotland), Dorset (Canadian Shield), Dry Creek (USA), Krycklan (Sweden), to Wolf (northern Canada). Xylem was isotopically depleted waters, most notably for deuterium. The degree which potential sources could explain the isotopic composition xylem assessed quantitatively using overlapping polygons enclose respective data sets when plotted dual isotope space. At angiosperms showed strong overlap with water; this not case gymnosperms. In cases, on given sampling day be better explained if considered longer antecedent periods spanning many months. at usually dissimilar drier summer months, although differed sequence change. Open questions remain why significant proportion cannot by sources, particularly It is recommended that future research focuses fractionation affect uptake soil-root interface, both through effects exchange between vapour liquid phases mycorrhizal interactions. Additionally, cold regions, evaporation diffusion winter may an important process.