Storage, mixing, and fluxes of water in the critical zone across northern environments inferred by stable isotopes of soil water

Abstract. Understanding the influence of vegetation on water storage and flux in the upper soil is crucial in assessing the consequences of climate and land use change. We sampled the upper 20 cm of podzolic soils at 5 cm intervals in four sites differing in their vegetation (Scots Pine (Pinus sylvestris) and heather (Calluna sp. and Erica Sp)) and aspect. The sites were located within the Bruntland Burn long-term experimental catchment in the Scottish Highlands, a low energy, wet environment. Sampling took place on 11 occasions between September 2015 and September 2016 to capture seasonal variability in isotope dynamics. The pore waters of soil samples were analyzed for their isotopic composition (δ2H and δ18O) with the direct-equilibration method. Our results show that the soil waters in the top soil are, despite the low potential evaporation rates in such northern latitudes, kinetically fractionated compared to the precipitation input throughout the year. This fractionation signal decreases within the upper 15 cm resulting in the top 5 cm being isotopically differentiated to the soil at 15–20 cm soil depth. There are significant differences in the fractionation signal between soils beneath heather and soils beneath Scots pine, with the latter being more pronounced. But again, this difference diminishes within the upper 15 cm of soil. The enrichment in heavy isotopes in the topsoil follows a seasonal hysteresis pattern, indicating a lag time between the fractionation signal in the soil and the increase/decrease of soil evaporation in spring/autumn. Based on the kinetic enrichment of the soil water isotopes, we estimated the soil evaporation losses to be about 5 and 10 % of the infiltrating water for soils beneath heather and Scots pine, respectively. The high sampling frequency in time (monthly) and depth (5 cm intervals) revealed high temporal and spatial variability of the isotopic composition of soil waters, which can be critical, when using stable isotopes as tracers to assess plant water uptake patterns within the critical zone or applying them to calibrate tracer-aided hydrological models either at the plot to the catchment scale.

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Spatiotemporal variations of soil water stable isotopes in a small karst sinkhole basin

Environmental Earth Sciences ◽

10.1007/s12665-020-09284-w ◽

2021 ◽

Vol 80 (1) ◽

Author(s):

Tao Zhang ◽

Jianhong Li ◽

Junbing Pu ◽

Weijie Huo ◽

Sainan Wang

Keyword(s):

Stable Isotopes ◽

Soil Water ◽

Spatiotemporal Variations ◽

Karst Sinkhole

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Characterization of hydraulic properties in the upper vadose zone for two aquifers in Slovenia

10.5194/egusphere-egu21-2407 ◽

2021 ◽

Author(s):

Vesna Zupanc ◽

Matjaž Glavan ◽

Miha Curk ◽

Urša Pečan ◽

Michael Stockinger ◽

...

Keyword(s):

Stable Isotopes ◽

Soil Water ◽

Water Flow ◽

Vadose Zone ◽

Hydraulic Properties ◽

Isotope Composition ◽

Transport Processes ◽

Precipitation Event ◽

Water Fluxes ◽

Flow And Transport

Environmental tracers, present in the environment and provided by nature, provide integrative information about both water flow and transport. For studying water flow and solute transport, the hydrogen and oxygen isotopes are of special interest, as their ratios provide a tracer signal with every precipitation event and are seasonally distributed. In order to follow the seasonal distribution of stable isotopes in the soil water and use this information for identifying hydrological processes and hydraulic properties, soil was sampled three times in three profiles, two on Kr&#353;ko polje aquifer in SE Slovenia and one on Ljubljansko polje in central Slovenia. Isotope composition of soil water was measured with the water-vapor-equilibration method. Based on the isotope composition of soil water integrative information about water flow and transport processes with time and depth below ground were assessed. Porewater isotopes were in similar range as precipitation for all three profiles. &#160;Variable isotope ratios in the upper 60 cm for the different sampling times indicated dynamic water fluxes in this upper part of the vadose zone. Results also showed more evaporation at one sampling location, Brege. The information from stable isotopes will be of importance for further analyzing the water fluxes in the vadose zone of the study sties.&#160; This research was financed by the ARRS BIAT 20-21-32 and IAEA CRP 1.50.18 Multiple isotope fingerprints to identify sources and transport of agro-contaminants. &#160;

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Employing stable isotopes to determine the residence times of soil water and the temporal origin of water taken up by Fagus sylvatica and Picea abies in a temperate forest

New Phytologist ◽

10.1111/nph.15255 ◽

2018 ◽

Vol 219 (4) ◽

pp. 1300-1313 ◽

Cited By ~ 29

Author(s):

Nadine Brinkmann ◽

Stefan Seeger ◽

Markus Weiler ◽

Nina Buchmann ◽

Werner Eugster ◽

...

Keyword(s):

Stable Isotopes ◽

Picea Abies ◽

Soil Water ◽

Fagus Sylvatica ◽

Temperate Forest ◽

Residence Times

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Ideas and perspectives: Tracing terrestrial ecosystem water fluxes using hydrogen and oxygen stable isotopes – challenges and opportunities from an interdisciplinary perspective

Biogeosciences ◽

10.5194/bg-15-6399-2018 ◽

2018 ◽

Vol 15 (21) ◽

pp. 6399-6415 ◽

Cited By ~ 36

Author(s):

Daniele Penna ◽

Luisa Hopp ◽

Francesca Scandellari ◽

Scott T. Allen ◽

Paolo Benettin ◽

...

Keyword(s):

Stable Isotopes ◽

Environmental Science ◽

Terrestrial Ecosystem ◽

Critical Zone ◽

Water Fluxes ◽

Stable Water Isotopes ◽

Natural Systems ◽

Plant Soil ◽

Oxygen Stable Isotopes ◽

Challenges And Opportunities

Abstract. In this commentary, we summarize and build upon discussions that emerged during the workshop “Isotope-based studies of water partitioning and plant–soil interactions in forested and agricultural environments” held in San Casciano in Val di Pesa, Italy, in September 2017. Quantifying and understanding how water cycles through the Earth's critical zone is important to provide society and policymakers with the scientific background to manage water resources sustainably, especially considering the ever-increasing worldwide concern about water scarcity. Stable isotopes of hydrogen and oxygen in water have proven to be a powerful tool for tracking water fluxes in the critical zone. However, both mechanistic complexities (e.g. mixing and fractionation processes, heterogeneity of natural systems) and methodological issues (e.g. lack of standard protocols to sample specific compartments, such as soil water and xylem water) limit the application of stable water isotopes in critical-zone science. In this commentary, we examine some of the opportunities and critical challenges of isotope-based ecohydrological applications and outline new perspectives focused on interdisciplinary research opportunities for this important tool in water and environmental science.

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Investigation of soil water hydrological process in the permafrost active layer using stable isotopes

Hydrological Processes ◽

10.1002/hyp.13765 ◽

2020 ◽

Vol 34 (12) ◽

pp. 2810-2822

Author(s):

Zongjie Li ◽

Jinzhu Ma ◽

Lingling Song ◽

Juan Gui ◽

Jian Xue ◽

...

Keyword(s):

Stable Isotopes ◽

Soil Water ◽

Active Layer ◽

Hydrological Process

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Metal stable isotopes track the fate of rock-derived nutrients in the critical zone

10.7185/gold2021.8170 ◽

2021 ◽

Author(s):

Julien Bouchez ◽

Friedhelm von Blanckenburg ◽

Patrick Frings

Keyword(s):

Stable Isotopes ◽

Critical Zone

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Stable isotopes reveal evaporation dynamics at the soil-plant-atmosphere interface of the critical zone

10.5194/hess-2017-87 ◽

2017 ◽

Cited By ~ 3

Author(s):

Matthias Sprenger ◽

Doerthe Tetzlaff ◽

Chris Soulsby

Keyword(s):

Stable Isotopes ◽

Isotopic Composition ◽

Scots Pine ◽

Soil Depth ◽

Critical Zone ◽

Soil Evaporation ◽

Pore Waters ◽

Catchment Scale ◽

Scottish Highlands ◽

Northern Latitudes

Abstract. Understanding the influence of vegetation on water storage and flux in the upper soil is crucial in assessing the consequences of climate and land use change. We sampled the upper 20 cm of podzolic soils at 5 cm intervals in four sites differing in their vegetation (Scots Pine (Pinus sylvestris) and heather (Calluna sp. and Erica Sp)) and aspect. The sites were located within the Bruntland Burn long-term experimental catchment in the Scottish Highlands; a low energy, wet environment. Sampling took place on 11 occasions between September 2015 and September 2016 to capture seasonal variability in isotope dynamics. The pore waters of soil samples were analysed for their isotopic composition (δ2H and δ18H) with the direct equilibration method. Our results show that the soil waters in the top soil are, despite the low potential evaporation rates in such northern latitudes, kinetically fractionated compared to the precipitation input throughout the year. This fractionation signal decreases within the upper 15 cm resulting in the top 5 cm being isotopically differentiated to the soil at 15–20 cm soil depth. There are significant differences in the fractionation signal between soils beneath heather and soils beneath Scots pine, with the latter being more pronounced. But again, this difference diminishes within the upper 15 cm of soil. The enrichment in heavy isotopes in the topsoil follows a seasonal hysteresis pattern, indicating a lag time between the fractionation signal in the soil and the increase/decrease of soil evaporation in spring/autumn. Based on the kinetic enrichment of the soil water isotopes, we estimated the soil evaporation losses to be about 5 and 10 % of the infiltrating water for soils beneath heather and Scots pine, respectively. The high sampling frequency in time (monthly) and depth (5 cm intervals) revealed high temporal and spatial variability of the isotopic composition of soil waters, which can be critical, when using stable isotopes as tracers to assess plant water uptake patterns within the critical zone or applying them to calibrate tracer-aided hydrological models either at the plot to the catchment scale.

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Equilibrium sediment exchange in the earth’s critical zone: evidence from sediment fingerprinting with stable isotopes and watershed modeling

Journal of Soils and Sediments ◽

10.1007/s11368-018-2208-8 ◽

2018 ◽

Vol 19 (9) ◽

pp. 3332-3356 ◽

Cited By ~ 4

Author(s):

David Tyler Mahoney ◽

Nabil Al Aamery ◽

James Forrest Fox ◽

Brenden Riddle ◽

William Ford ◽

...

Keyword(s):

Stable Isotopes ◽

Watershed Modeling ◽

Critical Zone ◽

Sediment Fingerprinting ◽

Earth’S Critical Zone

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Simulating soil-plant-atmosphere interactions for sub-daily in situ observations of stable isotopes in soil and xylem water to assess two-pore domain model hypothesis

10.5194/egusphere-egu2020-17975 ◽

2020 ◽

Author(s):

Fabian Bernhard ◽

Stefan Seeger ◽

Markus Weiler ◽

Arthur Gessler ◽

Katrin Meusburger

Keyword(s):

Stable Isotopes ◽

Soil Water ◽

Vadose Zone ◽

Model Performance ◽

Root Water Uptake ◽

In Situ Observations ◽

Pore Domain ◽

Model Structures ◽

Isotope Measurements

Recent advances in stable isotope measurements within the soil-plant-atmosphere continuum have paved the way to high-resolution sub-daily observations of plant water supply (Stumpp et al. 2018, Volkmann et al. 2016a, 2016b). It seems time is ripe for in-depth assessments of long-standing yet much-debated assumptions such as complete, homogenous mixing of water in the vadose zone (&#8220;one water world&#8221; versus "two water world") or absence of fractionation during root water uptake and vascular transport in plants.Information on the nature of these processes contained in high-resolution data sets needs to be exploited. One way to test hypotheses and thereby advance our understanding of soil-plant water interactions is by analysing observations with numerical simulations of the system dynamics &#8211; a method also known as inverse modelling. By evaluating the model performance and parameter identifiability of different model structures, conclusions can be drawn regarding the relevance of the modelled processes for reproduction of the observations. Testing two different models allows thus to assess the impact of the difference.We develop a framework for numerical simulation and model-based analysis of observations from soil-plant-atmosphere systems with a focus on isotopic fractionation. A central objective is to facilitate the evaluation of different model structures and thus test model hypotheses. This can assist development of models specifically tailored to the intended purpose and available data. The framework will first be tested with the "SWIS" model presented by Sprenger et al. (2018).As an illustration of the framework, we will test the model performance on a dataset of continuous, in situ observations of stable isotopes in xylem water of beech trees and soil water in four depths combined with observations of soil water content. The model assumes one-dimensional soil water flow taking place in one or two separate flow domains for tightly and weakly bound pore water. These two water pools are separated by a matrix potential threshold and isotopic exchange is modelled only through the vapour phase. Root water uptake is parametrised using the Feddes-Jarvis model. First results allow to assess the relevance of the two-pore domain hypothesis for the different soil depths and xylem water.&#160;Sprenger, M., D. Tetzlaff, J. Buttle, H. Laudon, H. Leistert, C.P.J. Mitchell, J. Snelgrove, M. Weiler, and C. Soulsby. 2018. Measuring and modeling stable isotopes of mobile and bulk soil water. Vadose Zone J. 17:170149. doi:10.2136/vzj2017.08.0149Stumpp, C., N. Br&#252;ggemann, and L. Wingate. 2018. Stable isotope approaches in vadose zone research. Vadose Zone J. 17:180096. Doi: 10.2136/vzj2018.05.0096Volkmann, T.H., K. Haberer, A. Gessler, and M. Weiler. 2016a. High&#8208;resolution isotope measurements resolve rapid ecohydrological dynamics at the soil&#8211;plant interface. New Phytologist, 210(3), 839-849.Volkmann, T.H., K. Haberer, A. Gessler, and M. Weiler. 2016a. High&#8208;resolution isotope measurements resolve rapid ecohydrological dynamics at the soil&#8211;plant interface. New Phytologist, 210(3), 839-849.

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