1
|
Kühnhammer K, van Haren J, Kübert A, Bailey K, Dubbert M, Hu J, Ladd SN, Meredith LK, Werner C, Beyer M. Deep roots mitigate drought impacts on tropical trees despite limited quantitative contribution to transpiration. Sci Total Environ 2023; 893:164763. [PMID: 37308023 PMCID: PMC10331952 DOI: 10.1016/j.scitotenv.2023.164763] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 06/05/2023] [Accepted: 06/07/2023] [Indexed: 06/14/2023]
Abstract
Deep rooting is considered a central drought-mitigation trait with vast impact on ecosystem water cycling. Despite its importance, little is known about the overall quantitative water use via deep roots and dynamic shifts of water uptake depths with changing ambient conditions. Knowledge is especially sparse for tropical trees. Therefore, we conducted a drought, deep soil water labeling and re-wetting experiment at Biosphere 2 Tropical Rainforest. We used in situ methods to determine water stable isotope values in soil and tree water in high temporal resolution. Complemented by soil and stem water content and sap flow measurements we determined percentages and quantities of deep-water in total root water uptake dynamics of different tree species. All canopy trees had access to deep-water (max. uptake depth 3.3 m), with contributions to transpiration ranging between 21 % and 90 % during drought, when surface soil water availability was limited. Our results suggest that deep soil is an essential water source for tropical trees that delays potentially detrimental drops in plant water potentials and stem water content when surface soil water is limited and could hence mitigate the impacts of increasing drought occurrence and intensity as a consequence of climate change. Quantitatively, however, the amount of deep-water uptake was low due to the trees' reduction of sap flow during drought. Total water uptake largely followed surface soil water availability and trees switched back their uptake depth dynamically, from deep to shallow soils, following rainfall. Total transpiration fluxes were hence largely driven by precipitation input.
Collapse
Affiliation(s)
- Kathrin Kühnhammer
- IGOE, Environmental Geochemistry, TU Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany; Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany.
| | - Joost van Haren
- Biosphere 2, University of Arizona, 32540 S Biosphere Road, Oracle, AZ 85623, USA; Honors College, University of Arizona, 1101 E. Mabel St., Tucson, AZ 85719, USA
| | - Angelika Kübert
- Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany; Institute for Atmospheric and Earth System Research, University of Helsinki, P.O. Box 68, Pietari Kalmin katu 5, 00014 Helsinki, Finland
| | - Kinzie Bailey
- School of Natural Resources and the Environment, University of Arizona, 1064 E Lowell St, Tucson, AZ 85721, USA
| | - Maren Dubbert
- Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany; Isotope Biogeochemistry and Gasfluxes, ZALF, Eberswalder Straße 84, 15374 Müncheberg, Germany
| | - Jia Hu
- School of Natural Resources and the Environment, University of Arizona, 1064 E Lowell St, Tucson, AZ 85721, USA
| | - S Nemiah Ladd
- Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany; Department of Environmental Sciences, University of Basel, Bernoullistrasse 32, 4056 Basel, Switzerland
| | - Laura K Meredith
- Biosphere 2, University of Arizona, 32540 S Biosphere Road, Oracle, AZ 85623, USA; School of Natural Resources and the Environment, University of Arizona, 1064 E Lowell St, Tucson, AZ 85721, USA
| | - Christiane Werner
- Ecosystem Physiology, University of Freiburg, Georges-Köhler-Allee 53/54, 79110 Freiburg, Germany
| | - Matthias Beyer
- IGOE, Environmental Geochemistry, TU Braunschweig, Langer Kamp 19c, 38106 Braunschweig, Germany
| |
Collapse
|
2
|
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. Sci Total Environ 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] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| |
Collapse
|
3
|
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 Environ 2023; 46:133-149. [PMID: 36305510 DOI: 10.1111/pce.14475] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [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.
Collapse
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
| | | |
Collapse
|
4
|
Kühnhammer K, Dahlmann A, Iraheta A, et al. Continuous in situ measurements of water stable isotopes in soils, tree trunk and root xylem: Field approval. Rapid Commun Mass Spectrom 2022; 36:e9371. [PMID: 36082612 DOI: 10.1002/rcm.9371] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
|