Preprints
https://doi.org/10.5194/hess-2020-592
https://doi.org/10.5194/hess-2020-592

  24 Nov 2020

24 Nov 2020

Review status: a revised version of this preprint was accepted for the journal HESS and is expected to appear here in due course.

Assessing ecohydrological separation in a northern mixed forest biome using stable isotopes

Jenna R. Snelgrove1, James M. Buttle2, Matthew J. Kohn3, and Dörthe Tetzlaff4,5 Jenna R. Snelgrove et al.
  • 1Environmental and Life Sciences Graduate Program, Trent University, Peterborough, ON, K9L 0G2, Canada
  • 2School of the Environment, Trent University, Peterborough, ON, K9L 0G2, Canada
  • 3Department of Geoscience, Boise State University, ID, 83725-1535, USA
  • 4Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB), Berlin, Germany
  • 5Department of Geography, Humboldt-University Berlin, Germany

Abstract. In recent years, much attention has been paid to the issue of ecohydrological separation during water uptake by vegetation. This has been spurred in part by the two water worlds hypothesis, whereby mobile blue water contributes to groundwater recharge and streamflow generation whereas less mobile green water held in the soil is taken up and transpired by vegetation. This study examines the potential for ecohydrological separation in a northern mixed forest in Ontario, Canada. Stable isotopic compositions of gross precipitation, bulk soil water and xylem water were measured throughout the 2016 growing season for four species: eastern white cedar, eastern hemlock, red oak and eastern white pine. Near-bole soil water contents and mobile soil water isotopic compositions were measured for the last three species. Mobile soil water did not deviate significantly from the local meteoric water line (LMWL); in contrast, both bulk soil water and xylem water deviated significantly from the LMWL, with xylem water significantly depleted in 18O and particularly 2H relative to bulk soil water. Near-surface bulk soil water experienced evaporative enrichment from pre-leaf out to peak leaf out under all tree canopies. There were inter-species differences in displacement of xylem water isotopic compositions from the LMWL and their temporal changes during the growing season, with those of coniferous species becoming isotopically enriched while those of red oak became more depleted in 2H and 18O. These divergences occurred despite thin soil cover (generally < 0.5 m depth to bedrock) which would constrain inter-species differences in tree rooting depths in this landscape. Our results failed to support the ecohydrological separation hypothesis that a distinct soil water source contributes to plant water uptake. Potential explanations for inter-specific differences in xylem water isotopic composition and its temporal evolution during the growing season in this northern forest landscape are assessed.

Jenna R. Snelgrove et al.

 
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Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Jenna R. Snelgrove et al.

Data sets

Snelgrove et al HESS 2020 submission James Buttle https://doi.org/10.5683/SP2/TGCHV6

Jenna R. Snelgrove et al.

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Short summary
The potential for ecohydrological separation in a little-studied northern mixed forest landscape was explored. Marked interspecific differences in the isotopic composition of xylem water relative to surrounding soil water occurred, despite thin soil cover constraining inter-species differences in rooting depths. We failed to observe ecohydrological separation and provide potential explanations for differences in temporal evolution of xylem water isotopic composition in this northern landscape.