We compare in our latest study soil water isotope data from suction cup lysimeter, that are limited to sample the mobile water (MW), with soil water isotope data sampled with the direct water-vapor analysis, that samples the bulk soil water (BW). We present for six landscape units at three VeWa sites that the BW isotopic compositions shows a kinetic fractionation, which is indicative for soil evaporation, but MW does not. We suggest that the relative volume of MW to BW is relevant for explaining these isotopic differences, since MW volumes are usually relatively low during periods of high evaporation. We additionally use the numerical 1-D flow model SWIS (Soil Water Isotope Simulator) to simulate the hydrometric and isotopic dynamics at the studied sites. The simulations accounting for a fast and slow flow supported the conceptualization of two soil pore domains (MW and BW) with isotopic exchange via vapor exchange. Please see the manuscript here.
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Very interesting discussion on the topic of water ages in the hydrological cycle during last weeks workshop funded by the Wassernetzwerk Baden-Württemberg. The interdisciplinary organizing committee (Prof. Dr. Markus Weiler , Chair of Hydrology, University of Freiburg; Prof. Dr. Werner Aeschbach , Institute of Environmental Physics, Heidelberg University; Prof. Dr. Christiane Werner , Chair of Ecosystem Physiology, University of Freiburg; PD Dr. Christiane Stumpp , Helmholtz Zentrum München and University of Freiburg) brought together early career and senior scientists working on the different compartments of the hydrological cycle. This way, the workshop fostered exchange between the disciplines to get a better understanding of how the water flow in the unsaturated and saturated zone is affected by vegetation and atmosphere. The workshop ended with a field visit of a long-term experimental forest site close to Freiburg (Conventwald).
EGU Session on "Stable isotopes to study water dynamics in the soil-plant-atmosphere continuum"4/10/2017 I organize a session for EGU 2018 together with Josie Geris, Christophe Hissler, Pilar Llorens and Natalie Orlowski on "Stable isotopes to study water dynamics in the soil-plant-atmosphere continuum". It is co-organized by the sections of Ecohydrology (HS10.5), Terrestrial Biogeoscience (BG2.1) and Soil System Science (SSS). Invited speaker will be Arthur Gessler from WSL, Zürich.
More info and the session description here. Tetzlaff, Doerthe, Ala-Aho, P; Buttle, J; Carey, SK; Kohn, M; Kuppel, S; Laudon, H; McDonnell, J; McNamara, JP; Spence, C; Sprenger, M; Smith, A; Soulsby, C :"Using stable isotopes to understand vegetation‐water linkages across northern landscapes (VeWa)"
Sprenger, M; Tetzlaff, D; Ala-Aho, P; Buttle, J; Laudon, H; Mitchell, C; Snelgrove, J; Weiler, M; Soulsby, C: Keynote on "Water fluxes, transport and transit times" including recent work on "Mobile and tightly bound soil water fluxes in northern environments" See the program of the conference here. Our study on the influence of forest and shrub canopies on precipitation partitioning and isotopic signatures is out in Hydrological Processes and available on Researchgate.
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