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A method for in situ monitoring of the isotope composition of tree xylem water using laser spectroscopy |
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| Authors: | Till H. M. Volkmann Kathrin Kühnhammer Barbara Herbstritt Arthur Gessler Markus Weiler |
| Affiliation: | 1. Chair of Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany;2. Biosphere 2 Earth Science, University of Arizona, Tucson, AZ, USA;3. Institute for Landscape Biogeochemistry, Leibniz Centre for Agricultural Landscape Research (ZALF), Müncheberg, Germany;4. Research Unit Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, Switzerland;5. Berlin‐Brandenburg Institute of Advanced Biodiversity Research (BBIB), Berlin, Germany |
| Abstract: | Field studies analyzing the stable isotope composition of xylem water are providing important information on ecosystem water relations. However, the capacity of stable isotopes to characterize the functioning of plants in their environment has not been fully explored because of methodological constraints on the extent and resolution at which samples could be collected and analysed. Here, we introduce an in situ method offering the potential to continuously monitor the stable isotope composition of tree xylem water via its vapour phase using a commercial laser‐based isotope analyser and compact microporous probes installed into the xylem. Our technique enables efficient high‐frequency measurement with intervals of only a few minutes per sample while eliminating the need for costly and cumbersome destructive collection of plant material and laboratory‐based processing. We present field observations of xylem water hydrogen and oxygen isotope compositions obtained over several days including a labelled irrigation event and compare them against results from concurrent destructive sampling with cryogenic distillation and mass spectrometric analysis. The data demonstrate that temporal changes as well as spatial patterns of integration in xylem water isotope composition can be resolved through direct measurement. The new technique can therefore present a valuable tool to study the hydraulic architecture and water utilization of trees. |
| Keywords: | hydraulic integration isotope ratio infrared spectroscopy (IRIS) isotope ratio mass spectrometry (IRMS) nutrients stable isotopes water relations xylem transport |