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Rao S, Liu T, Cernusak LA, Song X. Harnessing photosynthetic C 18O 16O discrimination dynamics under leaf water nonsteady state to estimate mesophyll conductance: a new, regression-based method. THE NEW PHYTOLOGIST 2024. [PMID: 38634162 DOI: 10.1111/nph.19767] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2023] [Accepted: 03/27/2024] [Indexed: 04/19/2024]
Abstract
Mesophyll conductance (gm) is a crucial plant trait that can significantly limit photosynthesis. Measurement of photosynthetic C18O16O discrimination (Δ18O) has proved to be the only viable means of resolving gm in both C3 and C4 plants. However, the currently available methods to exploit Δ18O for gm estimation are error prone due to their inadequacy in constraining the degree of oxygen isotope exchange (θ) during mesophyll CO2 hydration. Here, we capitalized on experimental manipulation of leaf water isotopic dynamics to establish a novel, nonsteady state, regression-based approach for simultaneous determination of gm and θ from online Δ18O measurements. We demonstrated the methodological and theoretical robustness of this new Δ18O-gm estimation approach and showed through measurements on several C3 and C4 species that this approach can serve as a benchmark method against which to identify previously-unrecognized biases of the existing Δ18O-gm methods. Our results highlight the unique value of this nonsteady state-based approach for contributing to ongoing efforts toward quantitative understanding of mesophyll conductance for crop yield improvement and carbon cycle modeling.
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Affiliation(s)
- Sen Rao
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
- Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen, 518060, China
| | - Tao Liu
- College of Resources, Sichuan Agricultural University, Chengdu, 611130, China
| | - Lucas A Cernusak
- College of Science and Engineering, James Cook University, Cairns, Qld, 4878, Australia
| | - Xin Song
- College of Life Sciences and Oceanography, Shenzhen University, Shenzhen, 518060, China
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2
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Haberstroh S, Kübert A, Werner C. Two common pitfalls in the analysis of water-stable isotopologues with cryogenic vacuum extraction and cavity ring-down spectroscopy. ANALYTICAL SCIENCE ADVANCES 2024; 5:2300053. [PMID: 38827022 PMCID: PMC11142394 DOI: 10.1002/ansa.202300053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 01/08/2024] [Accepted: 01/11/2024] [Indexed: 06/04/2024]
Abstract
Water stable isotopologue analysis is widely used to disentangle ecohydrological processes. Yet, there are increasing reports of measurement uncertainties for established and emerging methods, such as cryogenic vacuum extraction (CVE) or cavity ring-down spectroscopy (CRDS). With this study, we investigate two pitfalls, that potentially contribute to uncertainties in water-stable isotopologue research. To investigate fractionation sources in CVE, we extracted pure water of known isotopic composition with cotton, glass wool or without cover and compared the isotopologue results with non-extracted reference samples. To characterise the dependency of δ2H and δ18O on the water mixing ratio in CRDS, which is of high importance for in-situ applications with large natural variations in mixing ratios, we chose samples with a large range of isotopic compositions and determined δ2H and δ18O for different water mixing ratios with two CRDS analysers (Picarro, Inc.). Cotton wool had a strong fractionation effect on δ2H values, which increased with more 2H-enriched samples. δ2H and δ18O values showed a strong dependency on the water mixing ratio analysed with CRDS with differences of up to 34.5‰ (δ2H) and 3.9‰ (δ18O) for the same sample at different mixing ratios. CVE and CRDS, now routinely applied in water stable isotopologue research, come with pitfalls, namely fractionation effects of cover materials and water mixing ratio dependencies of δ2H and δ18O, which can lead to erroneous isotopologue results and thus, invalid conclusions about (ecohydrological) processes. These practical issues identified here should be reported and addressed adequately in water-stable isotopologue research.
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Affiliation(s)
- Simon Haberstroh
- Ecosystem PhysiologyFaculty of Environment and Natural ResourcesInstitute of Earth and Environmental SciencesUniversity FreiburgFreiburgGermany
| | - Angelika Kübert
- Ecosystem PhysiologyFaculty of Environment and Natural ResourcesInstitute of Earth and Environmental SciencesUniversity FreiburgFreiburgGermany
- Institute for Atmospheric and Earth System Research (INAR)University of HelsinkiHelsinkiFinland
| | - Christiane Werner
- Ecosystem PhysiologyFaculty of Environment and Natural ResourcesInstitute of Earth and Environmental SciencesUniversity FreiburgFreiburgGermany
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3
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Orlowski N, Rinderer M, Dubbert M, Ceperley N, Hrachowitz M, Gessler A, Rothfuss Y, Sprenger M, Heidbüchel I, Kübert A, Beyer M, Zuecco G, McCarter C. Challenges in studying water fluxes within the soil-plant-atmosphere continuum: A tracer-based perspective on pathways to progress. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 881:163510. [PMID: 37059146 DOI: 10.1016/j.scitotenv.2023.163510] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2023] [Revised: 04/04/2023] [Accepted: 04/10/2023] [Indexed: 06/01/2023]
Abstract
Tracing and quantifying water fluxes in the hydrological cycle is crucial for understanding the current state of ecohydrological systems and their vulnerability to environmental change. Especially the interface between ecosystems and the atmosphere that is strongly mediated by plants is important to meaningfully describe ecohydrological system functioning. Many of the dynamic interactions generated by water fluxes between soil, plant and the atmosphere are not well understood, which is partly due to a lack of interdisciplinary research. This opinion paper reflects the outcome of a discussion among hydrologists, plant ecophysiologists and soil scientists on open questions and new opportunities for collaborative research on the topic "water fluxes in the soil-plant-atmosphere continuum" especially focusing on environmental and artificial tracers. We emphasize the need for a multi-scale experimental approach, where a hypothesis is tested at multiple spatial scales and under diverse environmental conditions to better describe the small-scale processes (i.e., causes) that lead to large-scale patterns of ecosystem functioning (i.e., consequences). Novel in-situ, high-frequency measurement techniques offer the opportunity to sample data at a high spatial and temporal resolution needed to understand the underlying processes. We advocate for a combination of long-term natural abundance measurements and event-based approaches. Multiple environmental and artificial tracers, such as stable isotopes, and a suite of experimental and analytical approaches should be combined to complement information gained by different methods. Virtual experiments using process-based models should be used to inform sampling campaigns and field experiments, e.g., to improve experimental designs and to simulate experimental outcomes. On the other hand, experimental data are a pre-requisite to improve our currently incomplete models. Interdisciplinary collaboration will help to overcome research gaps that overlap across different earth system science fields and help to generate a more holistic view of water fluxes between soil, plant and atmosphere in diverse ecosystems.
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Affiliation(s)
- Natalie Orlowski
- Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg im Breisgau, Germany.
| | - Michael Rinderer
- Hydrology, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg im Breisgau, Germany; Geo7 AG, Bern, Switzerland
| | - Maren Dubbert
- Isotope Biogeochemistry and Gasfluxes, ZALF, Müncheberg, Germany
| | | | - Markus Hrachowitz
- Department of Water Management, Faculty of Civil Engineering and Geosciences, Delft University of Technology, Stevinweg 1, 2628CN Delft, Netherlands
| | - Arthur Gessler
- Forest Dynamics, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland; Institute of Terrestrial Ecosystems, ETH Zurich, Zurich, Switzerland
| | - Youri Rothfuss
- Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum Jülich GmbH, Jülich, Germany; Terra Teaching and Research Centre, University of Liège, Gembloux, Belgium
| | - Matthias Sprenger
- Earth and Environmental Sciences at the Lawrence Berkeley National Laboratory, Berkeley, USA
| | - Ingo Heidbüchel
- Hydrological Modelling, University of Bayreuth, Bayreuth, Germany; Hydrogeology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany
| | - Angelika Kübert
- Institute for Atmospheric and Earth System Research (INAR), University of Helsinki, Helsinki, Finland
| | - Matthias Beyer
- Institute for Geoecology, Technische Universität Braunschweig, Braunschweig, Germany
| | - Giulia Zuecco
- Department of Land, Environment, Agriculture and Forestry, University of Padova, Legnaro, Italy; Department of Chemical Sciences, University of Padova, Padova, Italy
| | - Colin McCarter
- Department of Geography, Department of Biology and Chemistry, Nipissing University, North Bay, Ontario, Canada
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4
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Kübert A, Dubbert M, Bamberger I, Kühnhammer K, Beyer M, van Haren J, Bailey K, Hu J, Meredith LK, Nemiah Ladd S, Werner C. Tracing plant source water dynamics during drought by continuous transpiration measurements: An in-situ stable isotope approach. PLANT, CELL & ENVIRONMENT 2023; 46:133-149. [PMID: 36305510 DOI: 10.1111/pce.14475] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Revised: 10/21/2022] [Accepted: 10/23/2022] [Indexed: 06/16/2023]
Abstract
The isotopic composition of xylem water (δX ) is of considerable interest for plant source water studies. In-situ monitored isotopic composition of transpired water (δT ) could provide a nondestructive proxy for δX -values. Using flow-through leaf chambers, we monitored 2-hourly δT -dynamics in two tropical plant species, one canopy-forming tree and one understory herbaceous species. In an enclosed rainforest (Biosphere 2), we observed δT -dynamics in response to an experimental severe drought, followed by a 2 H deep-water pulse applied belowground before starting regular rain. We also sampled branches to obtain δX -values from cryogenic vacuum extraction (CVE). Daily flux-weighted δ18 OT -values were a good proxy for δ18 OX -values under well-watered and drought conditions that matched the rainforest's water source. Transpiration-derived δ18 OX -values were mostly lower than CVE-derived values. Transpiration-derived δ2 HX -values were relatively high compared to source water and consistently higher than CVE-derived values during drought. Tracing the 2 H deep-water pulse in real-time showed distinct water uptake and transport responses: a fast and strong contribution of deep water to canopy tree transpiration contrasting with a slow and limited contribution to understory species transpiration. Thus, the in-situ transpiration method is a promising tool to capture rapid dynamics in plant water uptake and use by both woody and nonwoody species.
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Affiliation(s)
- Angelika Kübert
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
- Institute for Atmospheric and Earth System Research, University of Helsinki, Helsinki, Finland
| | - Maren Dubbert
- Isotope Biogeochemistry and Gas Fluxes, Landscape Functioning, ZALF, Müncheberg, Germany
| | - Ines Bamberger
- Atmospheric Chemistry Group, University of Bayreuth, Bayreuth, Germany
| | - Kathrin Kühnhammer
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
- Institute for Geoecology, Technical University of Braunschweig, Braunschweig, Germany
| | - Matthias Beyer
- Institute for Geoecology, Technical University of Braunschweig, Braunschweig, Germany
| | - Joost van Haren
- Biosphere 2, University of Arizona, Tucson, Arizona, USA
- Honors College, University of Arizona, Tucson, Arizona, USA
| | - Kinzie Bailey
- School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, USA
| | - Jia Hu
- School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, USA
| | - Laura K Meredith
- Biosphere 2, University of Arizona, Tucson, Arizona, USA
- School of Natural Resources and the Environment, University of Arizona, Tucson, Arizona, USA
| | - S Nemiah Ladd
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
- Biogeochemistry Group, Department of Environmental Sciences, University of Basel, Basel, Switzerland
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5
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Farquhar GD, Griffani DS, Barbour MM. The effects on isotopic composition of leaf water and transpiration of adding a gas-exchange cuvette. PLANT, CELL & ENVIRONMENT 2021; 44:2844-2857. [PMID: 33938016 DOI: 10.1111/pce.14076] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/24/2021] [Accepted: 04/26/2021] [Indexed: 06/12/2023]
Abstract
An expression was earlier derived for the non-steady state isotopic composition of a leaf when the composition of the water entering the leaf was not necessarily the same as that of the water being transpired (Farquhar and Cernusak 2005). This was relevant to natural conditions because the associated time constant is typically sufficiently long to ensure that the leaf water composition and fluxes of the isotopologues are rarely steady. With the advent of laser-based measurements of isotopologues, leaves have been enclosed in cuvettes and time courses of fluxes recorded. The enclosure modifies the time constant by effectively increasing the resistance to the one-way gross flux out of the stomata because transpiration increases the vapour concentration within the chamber. The resistance is increased from stomatal and boundary layer in series, to stomata, boundary layer and chamber resistance, where the latter is given by the ratio of leaf area to the flow rate out of the chamber. An apparent change in concept from one-way to net flux, introduced by Song, Simonin, Loucos and Barbour (2015) is resolved, and shown to be unnecessary, but the value of their data is reinforced.
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Affiliation(s)
- Graham D Farquhar
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Danielle S Griffani
- Research School of Biology, The Australian National University, Canberra, Australian Capital Territory, Australia
| | - Margaret M Barbour
- School of Life and Environmental Sciences, The University of Sydney, Sydney, New South Wales, Australia
- Te Aka Mātuatua-School of Science, The University of Waikato, Hamilton, New Zealand
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6
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Mejia-Chang M, Reyes-Garcia C, Seibt U, Royles J, Meyer MT, Jones GD, Winter K, Arnedo M, Griffiths H. Leaf water δ 18O reflects water vapour exchange and uptake by C 3 and CAM epiphytic bromeliads in Panama. FUNCTIONAL PLANT BIOLOGY : FPB 2021; 48:732-742. [PMID: 34099101 DOI: 10.1071/fp21087] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2021] [Accepted: 04/20/2021] [Indexed: 05/27/2023]
Abstract
The distributions of CAM and C3 epiphytic bromeliads across an altitudinal gradient in western Panama were identified from carbon isotope (δ13C) signals, and epiphyte water balance was investigated via oxygen isotopes (δ18O) across wet and dry seasons. There were significant seasonal differences in leaf water (δ18Olw), precipitation, stored 'tank' water and water vapour. Values of δ18Olw were evaporatively enriched at low altitude in the dry season for the C3 epiphytes, associated with low relative humidity (RH) during the day. Crassulacean acid metabolism (CAM) δ18Olw values were relatively depleted, consistent with water vapour uptake during gas exchange under high RH at night. At high altitude, cloudforest locations, C3 δ18Olw also reflected water vapour uptake by day. A mesocosm experiment with Tillandsia fasciculata (CAM) and Werauhia sanguinolenta (C3) was combined with simulations using a non-steady-state oxygen isotope leaf water model. For both C3 and CAM bromeliads, δ18Olw became progressively depleted under saturating water vapour by day and night, although evaporative enrichment was restored in the C3 W. sanguinolenta under low humidity by day. Source water in the overlapping leaf base 'tank' was also modified by evaporative δ18O exchanges. The results demonstrate how stable isotopes in leaf water provide insights for atmospheric water vapour exchanges for both C3 and CAM systems.
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Affiliation(s)
- Monica Mejia-Chang
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Casandra Reyes-Garcia
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK; and Unidad de Recursos Naturales, Centro de Investigación Científica de Yucatán, Calle 43 Num. 130 Churburná de Hidalgo, Mérida, 97200, México
| | - Ulli Seibt
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK; and Department of Atmospheric and Oceanic Sciences, UCLA, Los Angeles, CA, USA
| | - Jessica Royles
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Moritz T Meyer
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Glyn D Jones
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK
| | - Klaus Winter
- Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Republic of Panama
| | - Miquel Arnedo
- Departament de Biologia Evolutiva, Ecologia i Ciències Ambientals, Fac. Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
| | - Howard Griffiths
- Physiological Ecology Group, Department of Plant Sciences, University of Cambridge, Cambridge, CB2 3EA, UK; and Corresponding author.
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7
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Wang A, Siegwolf RTW, Joseph J, Thomas FM, Werner W, Gessler A, Rigling A, Schaub M, Saurer M, Li MH, Lehmann MM. Effects of soil moisture, needle age and leaf morphology on carbon and oxygen uptake, incorporation and allocation: a dual labeling approach with 13CO2 and H218O in foliage of a coniferous forest. TREE PHYSIOLOGY 2021; 41:50-62. [PMID: 32879961 DOI: 10.1093/treephys/tpaa114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 08/25/2020] [Indexed: 06/11/2023]
Abstract
The carbon and oxygen isotopic composition of water and assimilates in plants reveals valuable information on plant responses to climatic conditions. Yet, the carbon and oxygen uptake, incorporation and allocation processes determining isotopic compositions are not fully understood. We carried out a dual-isotope labeling experiment at high humidity with 18O-enriched water (H218O) and 13C-enriched CO2 (13CO2) with attached Scots pine (Pinus sylvestris L.) branches and detached twigs of hemiparasitic mistletoes (Viscum album ssp. austriacum) in a naturally dry coniferous forest, where also a long-term irrigation takes place. After 4 h of label exposure, we sampled previous- and recent-year leaves, twig phloem and twig xylem over 192 h for the analysis of isotope ratios in water and assimilates. For both species, the uptake into leaf water and the incorporation of the 18O-label into leaf assimilates was not influenced by soil moisture, while the 13C-label incorporation into assimilates was significantly higher under irrigation compared with control dry conditions. Species-specific differences in leaf morphology or needle age did not affect 18O-label uptake into leaf water, but the incorporation of both tracers into assimilates was two times lower in mistletoe than in pine. The 18O-label allocation in water from pine needles to twig tissues was two times higher for phloem than for xylem under both soil moisture conditions. In contrast, the allocation of both tracers in pine assimilates were similar and not affected by soil moisture, twig tissue or needle age. Soil moisture effects on 13C-label but not on 18O-label incorporation into assimilates can be explained by the stomatal responses at high humidity, non-stomatal pathways for water and isotope exchange reactions. Our results suggest that non-photosynthetic 18O-incorporation processes may have masked prevalent photosynthetic processes. Thus, isotopic variation in leaf water could also be imprinted on assimilates when photosynthetic assimilation rates are low.
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Affiliation(s)
- Ao Wang
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
- Institute of Terrestrial Ecosystems, ETH Zurich, Universitaetsstrasse 16, 8092 Zurich, Switzerland
| | - Rolf T W Siegwolf
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Jobin Joseph
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Frank M Thomas
- Geobotany, University of Trier, Behringstrasse 21, 54296 Trier, Germany
| | - Willy Werner
- Geobotany, University of Trier, Behringstrasse 21, 54296 Trier, Germany
| | - Arthur Gessler
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
- Institute of Terrestrial Ecosystems, ETH Zurich, Universitaetsstrasse 16, 8092 Zurich, Switzerland
| | - Andreas Rigling
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
- Institute of Terrestrial Ecosystems, ETH Zurich, Universitaetsstrasse 16, 8092 Zurich, Switzerland
| | - Marcus Schaub
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Matthias Saurer
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Mai-He Li
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
| | - Marco M Lehmann
- Forest Dynamics, Swiss Federal Research Institute WSL Birmensdorf, Zuercherstrasse 111, 8903 Birmensdorf, Switzerland
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8
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Kühnhammer K, Kübert A, Brüggemann N, Deseano Diaz P, van Dusschoten D, Javaux M, Merz S, Vereecken H, Dubbert M, Rothfuss Y. Investigating the root plasticity response of Centaurea jacea to soil water availability changes from isotopic analysis. THE NEW PHYTOLOGIST 2020; 226:98-110. [PMID: 31792975 DOI: 10.1111/nph.16352] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 11/21/2019] [Indexed: 06/10/2023]
Abstract
Root water uptake is a key ecohydrological process for which a physically based understanding has been developed in the past decades. However, due to methodological constraints, knowledge gaps remain about the plastic response of whole plant root systems to a rapidly changing environment. We designed a laboratory system for nondestructive monitoring of stable isotopic composition in plant transpiration of a herbaceous species (Centaurea jacea) and of soil water across depths, taking advantage of newly developed in situ methods. Daily root water uptake profiles were obtained using a statistical Bayesian multisource mixing model. Fast shifts in the isotopic composition of both soil and transpiration water could be observed with the setup and translated into dynamic and pronounced shifts of the root water uptake profile, even in well watered conditions. The incorporation of plant physiological and soil physical information into statistical modelling improved the model output. A simple exercise of water balance closure underlined the nonunique relationship between root water uptake profile on the one hand, and water content and root distribution profiles on the other, illustrating the continuous adaption of the plant water uptake as a function of its root hydraulic architecture and soil water availability during the experiment.
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Affiliation(s)
- Kathrin Kühnhammer
- Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
| | - Angelika Kübert
- Ecosystem Physiology, University Freiburg, D-79104, Freiburg, Germany
| | - Nicolas Brüggemann
- Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
| | - Paulina Deseano Diaz
- Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
| | - Dagmar van Dusschoten
- Institute of Bio- and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
| | - Mathieu Javaux
- Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
- Earth and Life Institute, Environmental Sciences (ELIE), Université catholique de Louvain (UCL), B-1348, Louvain-la-Neuve, Belgium
| | - Steffen Merz
- Institute of Energy and Climate Research, Fundamental Electrochemistry (IEK-9), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
| | - Harry Vereecken
- Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
| | - Maren Dubbert
- Ecosystem Physiology, University Freiburg, D-79104, Freiburg, Germany
| | - Youri Rothfuss
- Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, D-52425, Jülich, Germany
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9
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Lehmann MM, Goldsmith GR, Mirande-Ney C, Weigt RB, Schönbeck L, Kahmen A, Gessler A, Siegwolf RTW, Saurer M. The 18 O-signal transfer from water vapour to leaf water and assimilates varies among plant species and growth forms. PLANT, CELL & ENVIRONMENT 2020; 43:510-523. [PMID: 31732962 DOI: 10.1111/pce.13682] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Revised: 11/11/2019] [Accepted: 11/14/2019] [Indexed: 06/10/2023]
Abstract
The 18 O signature of atmospheric water vapour (δ18 OV ) is known to be transferred via leaf water to assimilates. It remains, however, unclear how the 18 O-signal transfer differs among plant species and growth forms. We performed a 9-hr greenhouse fog experiment (relative humidity ≥ 98%) with 18 O-depleted water vapour (-106.7‰) on 140 plant species of eight different growth forms during daytime. We quantified the 18 O-signal transfer by calculating the mean residence time of O in leaf water (MRTLW ) and sugars (MRTSugars ) and related it to leaf traits and physiological drivers. MRTLW increased with leaf succulence and thickness, varying between 1.4 and 10.8 hr. MRTSugars was shorter in C3 and C4 plants than in crassulacean acid metabolism (CAM) plants and highly variable among species and growth forms; MRTSugars was shortest for grasses and aquatic plants, intermediate for broadleaf trees, shrubs, and herbs, and longest for conifers, epiphytes, and succulents. Sucrose was more sensitive to δ18 OV variations than other assimilates. Our comprehensive study shows that plant species and growth forms vary strongly in their sensitivity to δ18 OV variations, which is important for the interpretation of δ18 O values in plant organic material and compounds and thus for the reconstruction of climatic conditions and plant functional responses.
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Affiliation(s)
- Marco M Lehmann
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, 8903, Switzerland
| | - Gregory R Goldsmith
- Schmid College of Science and Technology, Chapman University, Orange, CA, 92866
| | | | - Rosemarie B Weigt
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, 8903, Switzerland
| | - Leonie Schönbeck
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, 8903, Switzerland
| | - Ansgar Kahmen
- Department of Environmental Sciences-Botany, University of Basel, Basel, 4056, Switzerland
| | - Arthur Gessler
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, 8903, Switzerland
| | - Rolf T W Siegwolf
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, 8903, Switzerland
| | - Matthias Saurer
- Forest Dynamics, Swiss Federal Institute for Forest, Snow and Landscape Research (WSL), Birmensdorf, 8903, Switzerland
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Kübert A, Paulus S, Dahlmann A, Werner C, Rothfuss Y, Orlowski N, Dubbert M. Water Stable Isotopes in Ecohydrological Field Research: Comparison Between In Situ and Destructive Monitoring Methods to Determine Soil Water Isotopic Signatures. FRONTIERS IN PLANT SCIENCE 2020; 11:387. [PMID: 32346381 PMCID: PMC7171290 DOI: 10.3389/fpls.2020.00387] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2019] [Accepted: 03/18/2020] [Indexed: 05/15/2023]
Abstract
Ecohydrological isotope based field research is often constrained by a lack of temporally explicit soil water data, usually related to the choice of destructive sampling in the field and subsequent analysis in the laboratory. New techniques based on gas permeable membranes allow to sample soil water vapor in situ and infer soil liquid water isotopic signatures. Here, a membrane-based in situ soil water vapor sampling method was tested at a grassland site in Freiburg, Germany. It was further compared with two commonly used destructive sampling approaches for determination of soil liquid water isotopic signatures: cryogenic vacuum extraction and centrifugation. All methods were tested under semi-controlled field conditions, conducting an experiment with dry-wet cycling and two isotopically different labeling irrigation waters. We found mean absolute differences between cryogenic vacuum extraction and in situ vapor measurements of 0.3-14.2‰ (δ18O) and 0.4-152.2‰ (δ2H) for soil liquid water. The smallest differences were found under natural abundance conditions of 2H and 18O, the strongest differences were observed after irrigation with labeled waters. Labeling strongly increased the isotopic variation in soil water: Mean soil water isotopic signatures derived by cryogenic vacuum extraction were -11.6 ± 10.9‰ (δ18O) and +61.9 ± 266.3‰ (δ2H). The in situ soil water vapor method showed isotopic signatures of -12.5 ± 9.4‰ (δ18O) and +169.3 ± 261.5‰ (δ2H). Centrifugation was unsuccessful for soil samples due to low water recovery rates. It is therefore not recommended. Our study highlights that the in situ soil water vapor method captures the temporal dynamics in the isotopic signature of soil water well while the destructive approach also includes the natural lateral isotopic heterogeneity. The different advantages and limitations of the three methods regarding setup, handling and costs are discussed. The choice of method should not only consider prevailing environmental conditions but the experimental design and goal. We see a very promising tool in the in situ soil water vapor method, capturing both temporal developments and spatial variability of soil water processes.
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Affiliation(s)
- Angelika Kübert
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
- *Correspondence: Angelika Kübert,
| | - Sinikka Paulus
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
- Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany
| | - Adrian Dahlmann
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
| | | | - Youri Rothfuss
- Institute of Bio- and Geosciences, Agrosphere Institute (IBG-3), Jülich, Germany
| | | | - Maren Dubbert
- Ecosystem Physiology, University of Freiburg, Freiburg, Germany
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Dubbert M, Caldeira MC, Dubbert D, Werner C. A pool-weighted perspective on the two-water-worlds hypothesis. THE NEW PHYTOLOGIST 2019; 222:1271-1283. [PMID: 30604465 DOI: 10.1111/nph.15670] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/22/2018] [Indexed: 06/09/2023]
Abstract
The 'two-water-worlds' hypothesis is based on stable isotope differences in stream, soil and xylem waters in dual isotope space. It postulates no connectivity between bound and mobile soil waters, and preferential plant water uptake of bound soil water sources. We tested the pool-weighted impact of isotopically distinct water pools for hydrological cycling, the influence of species-specific water use and the degree of ecohydrological separation. We combined stable isotope analysis (δ18 O and δ2 H) of ecosystem water pools of precipitation, groundwater, soil and xylem water of two distinct species (Quercus suber, Cistus ladanifer) with observations of soil water contents and sap flow. Shallow soil water was evaporatively enriched during dry-down periods, but enrichment faded strongly with depth and upon precipitation events. Despite clearly distinct water sources and water-use strategies, both species displayed a highly opportunistic pattern of root water uptake. Here we offer an alternative explanation, showing that the isotopic differences between soil and plant water vs groundwater can be fully explained by spatio-temporal dynamics. Pool weighting the contribution of evaporatively enriched soil water reveals only minor annual impacts of these sources to ecosystem water cycling (c. 11% of bulk soil water and c. 14% of transpired water).
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Affiliation(s)
- Maren Dubbert
- Chair of Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, Freiburg, 79110, Germany
| | - Maria C Caldeira
- CEF, Instituto Superior de Agronomia, Universidade de Lisboa, Tapada da Ajuda, Lisbon, 1349-017, Portugal
| | - David Dubbert
- Chair of Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, Freiburg, 79110, Germany
- Landscape Ecohydrology, Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin, 12587, Germany
| | - Christiane Werner
- Chair of Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, Freiburg, 79110, Germany
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Dubbert M, Werner C. Water fluxes mediated by vegetation: emerging isotopic insights at the soil and atmosphere interfaces. THE NEW PHYTOLOGIST 2019; 221:1754-1763. [PMID: 30341780 DOI: 10.1111/nph.15547] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Accepted: 10/14/2018] [Indexed: 05/27/2023]
Abstract
Plants mediate water fluxes within the soil-vegetation-atmosphere continuum. This water transfer in soils, through plants, into the atmosphere can be effectively traced by stable isotopologues of water. However, rapid dynamic processes have only recently gained attention, such as adaptations in root water uptake depths (within hours to days) or the imprint of transpirational fluxes on atmospheric moisture, particularly promoted by the development of real-time in-situ water vapour stable isotope observation techniques. We focus on open questions and emerging insights at the soil-plant and plant-atmosphere interfaces, as we believe that these are the controlling factors for ecosystem water cycling. At both interfaces, complex pictures of interacting ecophysiological and hydrological processes emerge: root water uptake dynamics depend on both spatiotemporal variations in water availability and species-specific regulation of adaptive root conductivity within the rooting system by, for example, modulating soil-root conductivity in response to water and nutrient demands. Similarly, plant water transport and losses are a fine-tuned interplay between species-specific structural and functional strategies of water use and atmospheric processes. We propose that only by explicitly merging insights from distinct disciplines - for example, hydrology, plant physiology and atmospheric sciences - will we gain a holistic picture of the impact of vegetation on processes governing the soil-plant-atmosphere continuum.
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Affiliation(s)
- Maren Dubbert
- Ecosystem Physiology, University of Freiburg, 79110, Freiburg, Germany
| | - Christiane Werner
- Ecosystem Physiology, University of Freiburg, 79110, Freiburg, Germany
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Barbeta A, Peñuelas J. Increasing carbon discrimination rates and depth of water uptake favor the growth of Mediterranean evergreen trees in the ecotone with temperate deciduous forests. GLOBAL CHANGE BIOLOGY 2017; 23:5054-5068. [PMID: 28544424 DOI: 10.1111/gcb.13770] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 05/04/2017] [Accepted: 05/16/2017] [Indexed: 05/17/2023]
Abstract
Tree populations at the low-altitudinal or -latitudinal limits of species' distributional ranges are predicted to retreat toward higher altitudes and latitudes to track the ongoing changes in climate. Studies have focused on the climatic sensitivity of the retreating species, whereas little is known about the potential replacements. Competition between tree species in forest ecotones will likely be strongly influenced by the ecophysiological responses to heat and drought. We used tree-ring widths and δ13 C and δ18 O chronologies to compare the growth rates and long-term ecophysiological responses to climate in the temperate-Mediterranean ecotone formed by the deciduous Fagus sylvatica and the evergreen Quercus ilex at the low altitudinal and southern latitudinal limit of F. sylvatica (NE Iberian Peninsula). F. sylvatica growth rates were similar to those of other southern populations and were surprisingly not higher than those of Q. ilex, which were an order of magnitude higher than those in nearby drier sites. Higher Q. ilex growth rates were associated with high temperatures, which have increased carbon discrimination rates in the last 25 years. In contrast, stomatal regulation in F. sylvatica was proportional to the increase in atmospheric CO2 . Tree-ring δ18 O for both species were mostly correlated with δ18 O in the source water. In contrast to many previous studies, relative humidity was not negatively correlated with tree-ring δ18 O but had a positive effect on Q. ilex tree-ring δ18 O. Furthermore, tree-ring δ18 O decreased in Q. ilex over time. The sensitivity of Q. ilex to climate likely reflects the uptake of deep water that allowed it to benefit from the effect of CO2 fertilization, in contrast to the water-limited F. sylvatica. Consequently, Q. ilex is a strong competitor at sites currently dominated by F. sylvatica and could be favored by increasingly warmer conditions.
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Affiliation(s)
- Adrià Barbeta
- ISPA, Bordeaux Science Agro, INRA, Villenave d'Ornon, 33140, France
- Global Ecology Unit CREAF-CSIC-UAB, CSIC, E-08193, Bellaterra, Catalonia, Spain
- CREAF, E-08193, Cerdanyola del Vallès, Catalonia, Spain
| | - Josep Peñuelas
- Global Ecology Unit CREAF-CSIC-UAB, CSIC, E-08193, Bellaterra, Catalonia, Spain
- CREAF, E-08193, Cerdanyola del Vallès, Catalonia, Spain
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