scholarly journals Review of "Diurnal variation in the isotope composition of plant xylem water biases the depth of root-water uptake estimates” by Hannes P. T. De Deurwaerder et al.

2020 ◽  
Keyword(s):  
Diurnal Variation ◽  
Water Uptake ◽  
Isotope Composition ◽  
Root Water Uptake

scholarly journals Diurnal variation in the isotope composition of plant xylem water biases the depth of root-water uptake estimates

2020 ◽  
Author(s):  
Hannes P. T. De Deurwaerder ◽  
Marco D. Visser ◽  
Matteo Detto ◽  
Pascal Boeckx ◽  
Félicien Meunier ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Soil Water ◽  
Water Uptake ◽  
Isotope Composition ◽  
Soil Water Potential ◽  
Root Water Uptake ◽  
Stem Length ◽  
Sap Flux ◽  
Sap Flux Density ◽  
Water Isotopologues

Abstract. 1. Stable isotopologues of water are a widely used tool to derive the depth of root water uptake (RWU) in lignified plants. Uniform isotope composition of plant xylem water (i-H2O-xyl) along the stem length is a central assumption, which has never been properly evaluated. 2. We studied the effects of diurnal variation in RWU, sap flux density and various other soil and plant parameters on i-H2O-xyl within a plant using a mechanistic plant hydraulic model and empirical field observations from French Guiana and northwestern China. 3. Our model predicts significant i-H2O-xyl variation arising from diurnal RWU fluctuations and vertical soil water heterogeneity. Moreover, significant differences in i-H2O-xyl emerge between individuals with different sap flux densities. In line with model predictions, field data show excessive i-H2O-xyl variation during the day or along stem length ranging up to 25.2 ‰ in δ2H and 6.8 ‰ in δ18O, largely exceeding the measurement error range. 4. Our work show that the fundamental assumption of uniform i-H2O-xyl is violated both theoretically and empirically and therefore a real danger exists of significant biases when using stable water isotopologues to assess RWU. We propose to include monitoring of sap flow and soil water potential for more robust RWU depth estimates.

scholarly journals Supplementary material to "Diurnal variation in the isotope composition of plant xylem water biases the depth of root-water uptake estimates"

2020 ◽  
Author(s):  
Hannes P. T. De Deurwaerder ◽  
Marco D. Visser ◽  
Matteo Detto ◽  
Pascal Boeckx ◽  
Félicien Meunier ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Water Uptake ◽  
Isotope Composition ◽  
Root Water Uptake ◽  
Supplementary Material

scholarly journals Diurnal variation in xylem water isotopic signature biases depth of root-water uptake estimates

2019 ◽  
Author(s):  
Hannes De Deurwaerder ◽  
Marco D. Visser ◽  
Matteo Detto ◽  
Pascal Boeckx ◽  
Félicien Meunier ◽  
...  
Keyword(s):  
Diurnal Variation ◽  
Soil Water ◽  
Water Uptake ◽  
Sap Flow ◽  
Soil Water Potential ◽  
Root Water Uptake ◽  
Isotopic Signature ◽  
Stem Length ◽  
Individual Plant ◽  
List Type

SummaryStable water isotopes are a powerful and widely used tool to derive the depth of root water uptake (RWU) in lignified plants. Uniform xylem water isotopic signature (i-H2O-xyl) along the length of a lignified plant is a central assumption, which has never been properly evaluated.Here we studied the effects of diurnal variation in RWU, sap flow velocity and various other soil and plant parameters on i-H2O-xyl signature within a plant using a mechanistic plant hydraulic model.Our model predicts significant variation in i-H2O-xyl along the full length of an individual plant arising from diurnal RWU fluctuations and vertical soil water heterogeneity. Moreover, significant differences in i-H2O-xyl emerge between individuals with different sap flow velocities. We corroborated our model predictions with field observations from French Guiana and northwestern China. Modelled i-H2O-xyl varied considerably along stem length ranging up to 18.3‰ in δ2H and 2.2‰ in δ18O, largely exceeding the range of measurement error.Our results show clear violation of the fundamental assumption of uniform i-H2O-xyl and occurrence of significant biases when using stable isotopes to assess RWU. As a solution, we propose to include monitoring of sap flow and soil water potential for more robust RWU depth estimates.

scholarly journals In situ measurements of soil and plant water isotopes: a review of approaches, practical considerations and a vision for the future

2020 ◽  
Vol 24 (9) ◽  
pp. 4413-4440
Author(s):  
Matthias Beyer ◽  
Kathrin Kühnhammer ◽  
Maren Dubbert
Keyword(s):  
Water Uptake ◽  
Isotope Composition ◽  
Isotope Effects ◽  
Root Water Uptake ◽  
Water Isotopes ◽  
Future Research ◽  
Plant Water ◽  
In Situ Methods ◽  
Water Isotope

Abstract. The number of ecohydrological studies involving water stable isotope measurements has been increasing steadily due to technological (e.g., field-deployable laser spectroscopy and cheaper instruments) and methodological (i.e., tracer approaches or improvements in root water uptake models) advances in recent years. This enables researchers from a broad scientific background to incorporate water-isotope-based methods into their studies. Several isotope effects are currently not fully understood but might be essential when investigating root water uptake depths of vegetation and separating isotope processes in the soil–vegetation–atmosphere continuum. Different viewpoints exist on (i) extraction methods for soil and plant water and methodological artifacts potentially introduced by them, (ii) the pools of water (mobile vs. immobile) measured with those methods, and (iii) spatial variability and temporal dynamics of the water isotope composition of different compartments in terrestrial ecosystems. In situ methods have been proposed as an innovative and necessary way to address these issues and are required in order to disentangle isotope effects and take them into account when studying root water uptake depths of plants and for studying soil–plant–atmosphere interaction based on water stable isotopes. Herein, we review the current status of in situ measurements of water stable isotopes in soils and plants, point out current issues and highlight the potential for future research. Moreover, we put a strong focus and incorporate practical aspects into this review in order to provide a guideline for researchers with limited previous experience with in situ methods. We also include a section on opportunities for incorporating data obtained with described in situ methods into existing isotope-enabled ecohydrological models and provide examples illustrating potential benefits of doing so. Finally, we propose an integrated methodology for measuring both soil and plant water isotopes in situ when carrying out studies at the soil–vegetation–atmosphere continuum. Several authors have shown that reliable data can be generated in the field using in situ methods for measuring the soil water isotope composition. For transpiration, reliable methods also exist but are not common in ecohydrological field studies due to the required effort. Little attention has been paid to in situ xylem water isotope measurements. Research needs to focus on improving and further developing those methods. There is a need for a consistent and combined (soils and plants) methodology for ecohydrological studies. Such systems should be designed and adapted to the environment to be studied. We further conclude that many studies currently might not rely on in situ methods extensively because of the technical difficulty and existing methodological uncertainties. Future research needs to aim on developing a simplified approach that provides a reasonable trade-off between practicability and precision and accuracy.

scholarly journals Analysis of Soil Water Response to Grass Transpiration

2013 ◽  
Vol 1 (No. 3) ◽  
pp. 85-98
Author(s):  
Dohnal Michal ◽  
Dušek Jaromír ◽  
Vogel Tomáš ◽  
Herza Jiří
Keyword(s):  
Soil Water ◽  
Water Uptake ◽  
Preferential Flow ◽  
Water Movement ◽  
Control Volume ◽  
Water Pressure ◽  
Lower Boundary ◽  
Root Water Uptake ◽  
Water Dynamics ◽  
Soil Water Dynamics

This paper focuses on numerical modelling of soil water movement in response to the root water uptake that is driven by transpiration. The flow of water in a lysimeter, installed at a grass covered hillslope site in a small headwater catchment, is analysed by means of numerical simulation. The lysimeter system provides a well defined control volume with boundary fluxes measured and soil water pressure continuously monitored. The evapotranspiration intensity is estimated by the Penman-Monteith method and compared with the measured lysimeter soil water loss and the simulated root water uptake. Variably saturated flow of water in the lysimeter is simulated using one-dimensional dual-permeability model based on the numerical solution of the Richards’ equation. The availability of water for the root water uptake is determined by the evaluation of the plant water stress function, integrated in the soil water flow model. Different lower boundary conditions are tested to compare the soil water dynamics inside and outside the lysimeter. Special attention is paid to the possible influence of the preferential flow effects on the lysimeter soil water balance. The adopted modelling approach provides a useful and flexible framework for numerical analysis of soil water dynamics in response to the plant transpiration.

scholarly journals Modelling the Impact on Root Water Uptake and Solute Return Flow of Different Drip Irrigation Regimes with Brackish Water

Water ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 425 ◽  
Author(s):  
Fairouz Slama ◽  
Nessrine Zemni ◽  
Fethi Bouksila ◽  
Roberto De Mascellis ◽  
Rachida Bouhlila
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Water Uptake ◽  
Brackish Water ◽  
Deficit Irrigation ◽  
Root Zone ◽  
Root Water Uptake ◽  
Return Flows ◽  
Semi Arid

Water scarcity and quality degradation represent real threats to economic, social, and environmental development of arid and semi-arid regions. Drip irrigation associated to Deficit Irrigation (DI) has been investigated as a water saving technique. Yet its environmental impacts on soil and groundwater need to be gone into in depth especially when using brackish irrigation water. Soil water content and salinity were monitored in a fully drip irrigated potato plot with brackish water (4.45 dSm−1) in semi-arid Tunisia. The HYDRUS-1D model was used to investigate the effects of different irrigation regimes (deficit irrigation (T1R, 70% ETc), full irrigation (T2R, 100% ETc), and farmer’s schedule (T3R, 237% ETc) on root water uptake, root zone salinity, and solute return flows to groundwater. The simulated values of soil water content (θ) and electrical conductivity of soil solution (ECsw) were in good agreement with the observation values, as indicated by mean RMSE values (≤0.008 m3·m−3, and ≤0.28 dSm−1 for soil water content and ECsw respectively). The results of the different simulation treatments showed that relative yield accounted for 54%, 70%, and 85.5% of the potential maximal value when both water and solute stress were considered for deficit, full. and farmer’s irrigation, respectively. Root zone salinity was the lowest and root water uptake was the same with and without solute stress for the treatment corresponding to the farmer’s irrigation schedule (273% ETc). Solute return flows reaching the groundwater were the highest for T3R after two subsequent rainfall seasons. Beyond the water efficiency of DI with brackish water, long term studies need to focus on its impact on soil and groundwater salinization risks under changing climate conditions.

Validation of a root water uptake model to estimate transpiration constraints

2010 ◽  
Vol 97 (9) ◽  
pp. 1382-1388 ◽  
Author(s):  
Derblai Casaroli ◽  
Quirijn de Jong van Lier ◽  
Durval Dourado Neto
Keyword(s):  
Water Uptake ◽  
Root Water Uptake
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