Ecohydrological separation in wet, low energy northern environments? A preliminary assessment using different soil water extraction techniques

Josie Geris, Doerthe Tetzlaff, Jeffery McDonnell, Jim Anderson, Graeme Paton, Chris Soulsby

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Abstract

Ecohydrological studies in seasonally dry climatic regions have revealed isotopic separation of the sources of water used by trees and those that generate stream flow, also referred to as the ‘two water worlds’ hypothesis. Here we investigated whether similar separation occurs in a wet, low energy northern (Latitude 57º) environment in Scotland. For two common soil types (Histosols and Podzols) at three soil depths, and at both forested (with Scots Pine (Pinus sylvestris)) and non-forested sites, we compared the stable isotope composition of soil water held at increasing soil water tensions. These were assessed by different soil water extraction techniques: Rhizon samplers (mobile water), centrifugation at different speeds (representing different tensions), and cryogenic extraction (bulk water). Sampling occurred during a relatively dry summer. Water that was held at increasing tensions appeared more depleted than more mobile water, consistent with older (winter) precipitation. This pattern was independent of soil type, vegetation cover, and time during the growing season, although there was a slight tendency towards less separation with soil depth. Nevertheless, soil waters in this generally wet, low energy environment exhibited only minor evaporative enrichment, limited to the upper soil profile only. Furthermore, stream water showed no deviation from the local meteoric water line. Preliminary sampling for tree xylem water suggested uptake of evaporated soil water from the near surface soil horizons (upper 10 cm) where fine root densities are concentrated. For Histosols in particular, tree water appeared lagged in its isotopic composition compared to the soil water time series. Although more work is needed to fully test the ‘two water worlds’ hypothesis, our initial analyses did not provide clear evidence to support this in wet, low energy northern environments.
Original languageEnglish
Pages (from-to)5139-5152
Number of pages14
JournalHydrological Processes
Volume29
Issue number25
Early online date29 Jul 2015
DOIs
Publication statusPublished - 15 Dec 2015

Fingerprint

soil water
energy
Histosol
water
soil depth
soil type
climatic region
Podzol
water extraction
sampling
water uptake
fine root
soil horizon
xylem
meteoric water
arid region
vegetation cover
sampler
soil profile
streamflow

Keywords

  • Isotopes
  • Water Storage
  • Soil Water Extraction
  • Tree Water Use

Cite this

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title = "Ecohydrological separation in wet, low energy northern environments? A preliminary assessment using different soil water extraction techniques",
abstract = "Ecohydrological studies in seasonally dry climatic regions have revealed isotopic separation of the sources of water used by trees and those that generate stream flow, also referred to as the ‘two water worlds’ hypothesis. Here we investigated whether similar separation occurs in a wet, low energy northern (Latitude 57º) environment in Scotland. For two common soil types (Histosols and Podzols) at three soil depths, and at both forested (with Scots Pine (Pinus sylvestris)) and non-forested sites, we compared the stable isotope composition of soil water held at increasing soil water tensions. These were assessed by different soil water extraction techniques: Rhizon samplers (mobile water), centrifugation at different speeds (representing different tensions), and cryogenic extraction (bulk water). Sampling occurred during a relatively dry summer. Water that was held at increasing tensions appeared more depleted than more mobile water, consistent with older (winter) precipitation. This pattern was independent of soil type, vegetation cover, and time during the growing season, although there was a slight tendency towards less separation with soil depth. Nevertheless, soil waters in this generally wet, low energy environment exhibited only minor evaporative enrichment, limited to the upper soil profile only. Furthermore, stream water showed no deviation from the local meteoric water line. Preliminary sampling for tree xylem water suggested uptake of evaporated soil water from the near surface soil horizons (upper 10 cm) where fine root densities are concentrated. For Histosols in particular, tree water appeared lagged in its isotopic composition compared to the soil water time series. Although more work is needed to fully test the ‘two water worlds’ hypothesis, our initial analyses did not provide clear evidence to support this in wet, low energy northern environments.",
keywords = "Isotopes, Water Storage, Soil Water Extraction, Tree Water Use",
author = "Josie Geris and Doerthe Tetzlaff and Jeffery McDonnell and Jim Anderson and Graeme Paton and Chris Soulsby",
note = "Funded by European Research Council ERC. Grant Number: project GA 335910 VEWA ACKNOWLEDGEMENTS The constructive comments and suggestions from two anonymous reviewers greatly improved an earlier version of this manuscript. Jon Dick, Jason Lesselsand Jane Bang Poulsen are thanked for assistance with data collection; Audrey Innes for sample preparation and assistance with the cryogenic extraction of water samples; Paula Craib for glassware design; Colleagues in Prof. J. Anderson’s lab for day-to-day assistance incryogenic extraction; Todd Dawson and Nathalie Schultz for providing information on extraction techniques and the analysis of vegetation water; Hedda Weitz for help with the centrifugation of soil samples;and Iain Malcolm and colleagues at the Marine Scotland Freshwater Lab for providing meteorological data. We thank Jason Newton and the Scottish Universities Environmental Research Centre (SUERC) Mass Spectrometry Facility Laboratory in East Kilbride for theisotopic analyses of the xylem water samples. The European Research Council ERC (project GA 335910VEWA) is thanked for funding.",
year = "2015",
month = "12",
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doi = "10.1002/hyp.10603",
language = "English",
volume = "29",
pages = "5139--5152",
journal = "Hydrological Processes",
issn = "0885-6087",
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TY - JOUR

T1 - Ecohydrological separation in wet, low energy northern environments? A preliminary assessment using different soil water extraction techniques

AU - Geris, Josie

AU - Tetzlaff, Doerthe

AU - McDonnell, Jeffery

AU - Anderson, Jim

AU - Paton, Graeme

AU - Soulsby, Chris

N1 - Funded by European Research Council ERC. Grant Number: project GA 335910 VEWA ACKNOWLEDGEMENTS The constructive comments and suggestions from two anonymous reviewers greatly improved an earlier version of this manuscript. Jon Dick, Jason Lesselsand Jane Bang Poulsen are thanked for assistance with data collection; Audrey Innes for sample preparation and assistance with the cryogenic extraction of water samples; Paula Craib for glassware design; Colleagues in Prof. J. Anderson’s lab for day-to-day assistance incryogenic extraction; Todd Dawson and Nathalie Schultz for providing information on extraction techniques and the analysis of vegetation water; Hedda Weitz for help with the centrifugation of soil samples;and Iain Malcolm and colleagues at the Marine Scotland Freshwater Lab for providing meteorological data. We thank Jason Newton and the Scottish Universities Environmental Research Centre (SUERC) Mass Spectrometry Facility Laboratory in East Kilbride for theisotopic analyses of the xylem water samples. The European Research Council ERC (project GA 335910VEWA) is thanked for funding.

PY - 2015/12/15

Y1 - 2015/12/15

N2 - Ecohydrological studies in seasonally dry climatic regions have revealed isotopic separation of the sources of water used by trees and those that generate stream flow, also referred to as the ‘two water worlds’ hypothesis. Here we investigated whether similar separation occurs in a wet, low energy northern (Latitude 57º) environment in Scotland. For two common soil types (Histosols and Podzols) at three soil depths, and at both forested (with Scots Pine (Pinus sylvestris)) and non-forested sites, we compared the stable isotope composition of soil water held at increasing soil water tensions. These were assessed by different soil water extraction techniques: Rhizon samplers (mobile water), centrifugation at different speeds (representing different tensions), and cryogenic extraction (bulk water). Sampling occurred during a relatively dry summer. Water that was held at increasing tensions appeared more depleted than more mobile water, consistent with older (winter) precipitation. This pattern was independent of soil type, vegetation cover, and time during the growing season, although there was a slight tendency towards less separation with soil depth. Nevertheless, soil waters in this generally wet, low energy environment exhibited only minor evaporative enrichment, limited to the upper soil profile only. Furthermore, stream water showed no deviation from the local meteoric water line. Preliminary sampling for tree xylem water suggested uptake of evaporated soil water from the near surface soil horizons (upper 10 cm) where fine root densities are concentrated. For Histosols in particular, tree water appeared lagged in its isotopic composition compared to the soil water time series. Although more work is needed to fully test the ‘two water worlds’ hypothesis, our initial analyses did not provide clear evidence to support this in wet, low energy northern environments.

AB - Ecohydrological studies in seasonally dry climatic regions have revealed isotopic separation of the sources of water used by trees and those that generate stream flow, also referred to as the ‘two water worlds’ hypothesis. Here we investigated whether similar separation occurs in a wet, low energy northern (Latitude 57º) environment in Scotland. For two common soil types (Histosols and Podzols) at three soil depths, and at both forested (with Scots Pine (Pinus sylvestris)) and non-forested sites, we compared the stable isotope composition of soil water held at increasing soil water tensions. These were assessed by different soil water extraction techniques: Rhizon samplers (mobile water), centrifugation at different speeds (representing different tensions), and cryogenic extraction (bulk water). Sampling occurred during a relatively dry summer. Water that was held at increasing tensions appeared more depleted than more mobile water, consistent with older (winter) precipitation. This pattern was independent of soil type, vegetation cover, and time during the growing season, although there was a slight tendency towards less separation with soil depth. Nevertheless, soil waters in this generally wet, low energy environment exhibited only minor evaporative enrichment, limited to the upper soil profile only. Furthermore, stream water showed no deviation from the local meteoric water line. Preliminary sampling for tree xylem water suggested uptake of evaporated soil water from the near surface soil horizons (upper 10 cm) where fine root densities are concentrated. For Histosols in particular, tree water appeared lagged in its isotopic composition compared to the soil water time series. Although more work is needed to fully test the ‘two water worlds’ hypothesis, our initial analyses did not provide clear evidence to support this in wet, low energy northern environments.

KW - Isotopes

KW - Water Storage

KW - Soil Water Extraction

KW - Tree Water Use

U2 - 10.1002/hyp.10603

DO - 10.1002/hyp.10603

M3 - Article

VL - 29

SP - 5139

EP - 5152

JO - Hydrological Processes

JF - Hydrological Processes

SN - 0885-6087

IS - 25

ER -