HS10.5

EDI

Stable isotopes are powerful tools for tracing fluxes of water and associated nutrients in the soil-plant-atmosphere continuum. They are increasingly used by various disciplines to better understand the functioning of the soil-plant-atmosphere system. While new methods allow measurements at high spatial and temporal resolution, studies applying tracer methods are now tackling complex interactions between soil processes, plant physiology and ecology, and variable atmospheric drivers. As such, methodological developments and changes are happening quickly and have a strong bearing on process understanding and interpretation of findings. This session aims to address the current state of the art for methods, applications, and process interpretations using stable isotopes in the critical zone and to foster interdisciplinary exchange. We welcome experimental and modeling studies that present methodological developments and applications of isotope tracers to improve the actual knowledge of the water and nutrient exchanges at the soil-plant-atmosphere interfaces. Studies that seek to cross disciplinary boundaries and reveal new eco-hydrological process understanding are especially welcome.

Convener: Jana von FreybergECSECS | Co-conveners: Jesse Radolinski, Natalie OrlowskiECSECS, Adrià BarbetaECSECS, Magali Nehemy
Presentations
| Thu, 26 May, 13:20–16:28 (CEST)
 
Room 2.15

Session assets

Session materials

Presentations: Thu, 26 May | Room 2.15

Chairpersons: Jana von Freyberg, Adrià Barbeta, Natalie Orlowski
13:20–13:25
13:25–13:35
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EGU22-1182
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solicited
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Highlight
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Virtual presentation
Katrin Meusburger, Fabian Bernhard, and Arthur Gessler

Processes in the rooting zone and root water uptake decisively affect ecosystem resilience to stressors such as drought or deposition of air pollutants. However, the rooting zone is literally a black box. Water stable isotopes may shed light on some parts of this black box and tell us about water residence times, mixing of different water pools, plant water sources, preferential flow, soil evaporation, and many more. While this flexibility to use stable water isotopes is advantageous, it also entails many degrees of freedom. The additional collinearity of the hydrogen and oxygen isotopes leads to a largely underdetermined problem to solve. Bayesian mixing models help quantify the resulting uncertainty and add some constraints to the system by prior knowledge. Particularly in the case of disentangling plant water sources, additional data such as soil water content, matric potential or sap flow are needed since i) the isotope gradient smoothes with soil depth and ii) isotope-derived relative changes in root water uptake cannot be translated to absolute ones. Framing this ancillary data in a physically based water balance model may refine our predictions and help to trace water and related nutrient fluxes through the belowground. This contribution will summarize some of the experience gained during an in-situ monitoring study conducted in the drought summer of 2018 and a one-year sampling campaign at ten long-term ecosystem monitoring sites across Switzerland.

How to cite: Meusburger, K., Bernhard, F., and Gessler, A.: What stable water isotopes may tell us about belowground processes, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1182, https://doi.org/10.5194/egusphere-egu22-1182, 2022.

13:35–13:36
13:36–13:43
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EGU22-8800
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ECS
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On-site presentation
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Ruth Magh, Benjamin Gralher, Barbara Herbstritt, Angelika Kübert, Hyungwoo Lim, Tomas Lundmark, and John Marshall

The interest of inferring plant water uptake depths/patterns and water movements through the soil matrix grew tremendously in recent years and, studies have shown the use of in-situ measurement systems based on laser absorption spectroscopy making e.g. plant or soil water stable isotope datasets available on-site and in real-time. However useful, in-situ systems are limited to sites with power supply and require constant care.

We tested, first in the lab and then in the field, a method for equilibrating, collecting, storing, and finally analysing water vapour for its isotopic composition. We used a vapour storage vial system (VSVS) that relies on in-situ sampling, using a pump and a flow meter powered through a small battery into crimp neck vials with a double coated lid, and measuring the samples in a laboratory. We tested the utility of the sampling method and the reliability of the VSVS to faithfully store the isotopic composition of its content by sampling a range of water vapour of known isotopic compositions (from -95 to 1700‰ for δ2H) and measuring the isotopic signature after the storage period. Samples for the field trial were taken in a tracer pulse chase experiment in a boreal forest in Northern Sweden.

We were able to prove the utility of the sampling method within defined uncertainties (0.6 to 4.4‰ for δ2H and 0.6 to 0.8‰ for δ18O) for natural abundance. For in 2H-enriched samples the range was adapted to higher uncertainty. We detected a small change in the isotopic composition of the sample after a longer storage period, which was consistently greater for oxygen but correctable by linear models.

Our method has the potential to combine the best of two worlds: sampling in-situ in high spatial or temporal resolution while measuring in the laboratory, could solve problems with location biases and give the community a tool that is not only cost-efficient but also easy to use while all components are commercially available.  

How to cite: Magh, R., Gralher, B., Herbstritt, B., Kübert, A., Lim, H., Lundmark, T., and Marshall, J.: Practical measurements of water stable isotopes in tree stems and soils using conservative water vapor storage, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8800, https://doi.org/10.5194/egusphere-egu22-8800, 2022.

13:43–13:50
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EGU22-4249
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ECS
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On-site presentation
Alessandro Montemagno, Christophe Hissler, Victor Bense, Adriaan J. Teuling, and Laurent Pfister

Since the `60s, stable isotopes of hydrogen and oxygen have proven to be excellent tracers for water flows in different systems. Nowadays, such tracers still represent a formidable resource for eco-hydrologists who study water spatio-temporal dynamics and transit time distributions in the Critical Zone (CZ). Unfortunately, many issues remain unsolved, especially when looking at the regolith-trees continuum in which a complex mixture of isotopic fractionation processes may occur (evaporation, transpiration, adsorption on soil clays and oxides, microorganism's activity, mixing of water of different ages). Moreover, the lack of standard protocols for sampling and analysis represents a limitation when determining which water source(s) trees uptake. Indeed, by using sap cryogenically extracted from tree cores (recognized as the standard protocol), several studies have indicated discrepancies between the isotopic signatures of xylem sap extracted from plants and the potential water source(s).

In this context, we propose to look at the water which flowing in the xylem vessels, by directly sampling sap from tree roots and branches. It is our hypothesis that root water would represent a more reliable fraction to identify the source(s) of water that trees absorbed from the different regolith compartments. Additionally, we also aim to observe how O and H isotopic composition of sap is evolving from the roots to the leaves. Inside this pathway, the absorbed water would be impacted by various processes, such as evaporation from the bark and mixing with other water pools (e.g. storage water), which would lead to a change in the isotopic composition of the sap which will be observed in the one extracted from the branches.

To reach our objectives, we sampled water from diverse CZ compartments at three European beech (Fagus sylvatica L.) stands in the Weierbach Experimental Catchment (Hissler et al. 2021). These stands are located along a catena from the highest elevation (plateau) to the stream (riparian zone). Rainfall, throughfall, soil solutions at 20, 40 and 60 cm depth, groundwater and streamwater were collected. For beech sap sampling, we developed and applied an in-situ extraction using suction under vacuum. This method allowed us to collect sap from roots, stems and branches, separately. At the same time, tree cores from the trunks were collected and stored at -20 °C before cryogenically extracting their water content under vacuum.

When reported in a δ2H vs. δ18O diagram, our results clearly illustrate that beech sap samples extracted with this techniques plot in a different area than the water extracted using cryogenic extraction. The root sap samples fall on the Local Meteoric Water Line (LMWL) in the same field as specific water sources (soil solutions, groundwater, streamwater). Moreover, the sap samples collected from branches are also located on the LMWL but presented a significant enrichment in 18O and 2H in comparison to the root sap samples. These new results allow us to calculate more accurately the contribution of the regolith water pools to the tree uptake and to discuss the origin of the fractionation that happened for both O and H isotopes in the tree water pathway.

How to cite: Montemagno, A., Hissler, C., Bense, V., Teuling, A. J., and Pfister, L.: New approaches to sap extraction from trees and comparison with conventional methods: new avenues for H and O stable isotopes ecohydrology, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4249, https://doi.org/10.5194/egusphere-egu22-4249, 2022.

13:50–13:57
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EGU22-9558
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On-site presentation
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Valentin Couvreur, Flavius C Pascut, Daniela Dietrich, Nicky Leftley, Guilhem Reyt, Yann Boursiac, Monica Calvo-Polanco, Ilda Casimiro, Christophe Maurel, David E Salt, Xavier Draye, Darren M Wells, Malcolm J Bennett, and Kevin F Webb

A key impediment to studying water-related mechanisms in plants is the inability to noninvasively image water fluxes in cells at high temporal and spatial resolution. Here, we report that Raman microspectroscopy, complemented by hydrodynamic modelling, can achieve this goal - monitoring deuterated water fluxes within living root tissues at cell- and sub-second-scale resolutions. Raman imaging of water-transporting xylem vessels in Arabidopsis thaliana mutant roots reveals faster xylem water transport in endodermal diffusion barrier mutants. Furthermore, transverse line scans across the root suggest water transported via the root xylem does not re-enter outer root tissues nor the surrounding soil when en-route to shoot tissues if endodermal diffusion barriers are intact, thereby separating ‘two water worlds’ inside roots.

How to cite: Couvreur, V., Pascut, F. C., Dietrich, D., Leftley, N., Reyt, G., Boursiac, Y., Calvo-Polanco, M., Casimiro, I., Maurel, C., Salt, D. E., Draye, X., Wells, D. M., Bennett, M. J., and Webb, K. F.: Non-invasive isotope-based hydrodynamic imaging in plant roots at cellular resolution, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9558, https://doi.org/10.5194/egusphere-egu22-9558, 2022.

13:57–14:04
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EGU22-2594
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ECS
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On-site presentation
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Haoyu Diao, Philipp Schuler, Gregory Goldsmith, Matthias Saurer, and Marco Lehmann

Recent studies challenge the use of plant water from cryogenic vacuum distillation (CVD) extraction in accurately representing the hydrogen and oxygen isotopic composition (δ2H and δ18O) of plant source water. This is hypothesized to be because the δ2H in extracted water depends on tissue relative water content (RWC), which might be explained by the exchange of H-atoms between water and organic material. Secondary hypotheses focus on extraction artefacts related to evaporation and sublimation, but clear evidence is lacking. Here, we hypothesized that the observed δ2H and δ18O offsets (Δ2H and Δ18O) are influenced by (i) an H-exchange effect, (ii) tissue water amount or RWC and (iii) evaporation and sublimation enrichments.
The hypotheses were systematically tested by three corresponding experiments. Firstly, we added a range of strongly depleted reference water (δ2H: ca. -460‰; δ18O: ca. -170‰; 50–1200 μl) to organic materials (with and without exchangeable H) of constant weight (200 mg), followed by a 24 h incubation. In addition, the same range of pure reference water and tap water without any material were used as controls. Secondly, we incubated dry stem segments (Larix decidua) of different sizes in excess of reference water for 24 hours, then they were took out for extracting known water contents from samples with known RWC. Accordingly, fresh twig segments from the same species were prepared for extracting water with natural abundance. Thirdly, a range of different amounts of reference water (50–1200 μl) was added directly into the water collection tubes of the CVD extraction system. In addition, 2 ml glass vials containing the same range of reference water amounts were incubated in a climate chamber at 25 °C and 50 % relative humidity with lids open for 2 hours. All the samples, except the water in the glass vials, were extracted using a standard CVD extraction method for 2 hours. 
We found that both Δ2H and Δ18O values were not related to changes in RWC. In contrast, we observed an inversely proportional relationships with water amount, i.e., the lower the water amount, the higher the Δ2H and Δ18O. For Δ2H, the pattern was more pronounced for materials with exchangeable H, which reached 150‰ at the lowest water amount and decreased to -20‰ with increasing water amounts when the depleted reference water was used. However, the pattern was much less pronounced for the samples with natural isotopic abundance, indicating that the magnitude of the pattern is probably dependent on isotope ratios of plant water and water vapour in the laboratory. The evaporation and sublimation tests both showed that the pattern was partly caused by an increasing isotopic enrichment with decreasing water amount.
In conclusion, we identified a significant artefact of CVD when water is present in small amounts, particularly when δ2H and δ18O of the water was below natural isotope abundances. We therefore recommend extracting > 600 μl of water. Moreover, we provide first evidence of a significant H-exchange effect, suggesting that using hydrogen isotopes for estimating plant source water will remain challenging in future.

How to cite: Diao, H., Schuler, P., Goldsmith, G., Saurer, M., and Lehmann, M.: On uncertainties in the plant source water isotopic composition extracted with cryogenic vacuum distillation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2594, https://doi.org/10.5194/egusphere-egu22-2594, 2022.

14:04–14:11
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EGU22-10019
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ECS
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On-site presentation
Giulia Zuecco, Anam Amin, Jay Frentress, Michael Engel, Chiara Marchina, Tommaso Anfodillo, Marco Borga, Vinicio Carraro, Francesca Scandellari, Massimo Tagliavini, Damiano Zanotelli, Francesco Comiti, and Daniele Penna

Recent studies applying stable isotopes of hydrogen and oxygen showed that different methods for extracting water from plant tissues can return different isotopic composition. One of the most used methods to extract plant water is the cryogenic vacuum distillation (CVD), which tends to extract total plant water. Conversely, the Scholander pressure chamber (SPC), which is commonly used by tree physiologists to measure water potential in plant tissues, likely accesses only the mobile plant water (i.e., xylem and inter-cellular water). However, only few studies reported the application of SPC to extract plant water for isotopic analyses, and therefore, an inter-method comparison between SPC and CVD is needed.

In this study, we analyzed the variability in the isotopic signature of plant water extracted by SPC and CVD. Furthermore, we considered the potential variability in the isotopic composition of the plant water extracted from various tissues by CVD (i.e., leaves, twig without bark, twig with bark, twig close to the trunk of the tree, and wood core), and from different tree species (i.e., alder, apple, chestnut and beech) located in three different study areas in northern Italy.

Results indicate that plant waters extracted by SPC and CVD were significantly different, likely due to the extraction of different plant water domains. The difference in the isotopic composition obtained by the two extraction methods was smaller in the beech samples compared to alder, apple and chestnut samples. The signature of alder, apple and chestnut plant water extracted by SPC was more enriched in heavy isotopes than the samples obtained by CVD (except for the leaf water obtained by CVD, which also had a marked evaporative signature). We conclude that plant water extraction by SPC does not represent an alternative for CVD, as SPC likely extracts mostly the mobile plant water, whereas CVD tends to retrieve all water stored in the sampled tissues. However, studies aiming to quantify the relative contribution of the water sources to transpiration should rely more on the isotopic composition of xylem water transpiring during the sampling day (theoretically sampled by SPC), than the isotopic composition of total plant water (sampled by CVD), which also contains a fraction of water that could be stored in plant tissues for a long time.

 

 

Keywords: stable isotopes of hydrogen and oxygen; cryogenic vacuum distillation; Scholander pressure chamber; plant water; xylem water.

How to cite: Zuecco, G., Amin, A., Frentress, J., Engel, M., Marchina, C., Anfodillo, T., Borga, M., Carraro, V., Scandellari, F., Tagliavini, M., Zanotelli, D., Comiti, F., and Penna, D.: Comparing plant water extraction methods for isotopic analyses: the Scholander pressure chamber vs. the cryogenic vacuum distillation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10019, https://doi.org/10.5194/egusphere-egu22-10019, 2022.

14:11–14:18
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EGU22-11593
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ECS
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On-site presentation
Angelika Kübert, Maren Dubbert, Kathrin Kuehnhammer, Matthias Beyer, Joost van Haren, Laura K. Meredith, S. Nemiah Ladd, and Christiane Werner

The isotopic signature of xylem water (δX) is of great interest for plant source water studies. δX is usually derived by destructive sampling and subsequent cryogenic vacuum extraction (CVE). However, numerous studies have criticized this approach due its methodological constraints and analytical artifacts. New in situ methods to derive δX have been proposed in recent years. Yet, they are still in the development- and test phase, and their application highly intrusive. Gas exchange chamber techniques, on the other hand, have been well established for decades and allow the isotopic signature of transpired water (δT) to be monitored in high temporal resolution. As δT values approach δx values when transpiration is at isotopic steady state, measurements of δT may provide a relatively non-intrusive method to derive δX values.  

While conducting a large-scale long-term drought experiment of 90 days in a model rainforest ecosystem (Biosphere 2, WALD project), we monitored dynamics in δT values in two tropical plant species, one understory and one canopy species. Severe drought was ended with a deep water pulse strongly enriched in 2H. By connecting flow-through leaf chambers to a water isotope analyzer, we measured δT in a 2-h resolution and observed its response to increasing drought, deep labelling and subsequent recovery. Parallel to continuous measurements of δT, branch samples were collected at 5 time points throughout the experiment to determine δX values from CVE.

We found that δT values provide a good proxy for δX values when using the daily averages of δT values, weighted by the transpiration flux; derived δX values matched well with isotopic compositions of soil water. In situ-δ18OX agreed well with values from CVE. CVE-δ2HX values, however, were strongly enriched in 2H in comparison to in situ derived values, which is probably linked to the isotopic effects of CVE on δ2H as recently found in several studies. Moreover, by adding a 2H deep water pulse, δT allowed us to distinguish clearly between deep and shallow soil water use as well as show uptake velocities of newly added water. Monitoring  δT using gas exchange chambers provides a good proxy for δX values to address research questions concerning plant-available water sources and their usage, and at the same time give additional information on the plant water status. 

How to cite: Kübert, A., Dubbert, M., Kuehnhammer, K., Beyer, M., van Haren, J., Meredith, L. K., Ladd, S. N., and Werner, C.: Deriving xylem water isotopic compositions from in situ transpiration measurements: opportunity for plant source water identification? , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11593, https://doi.org/10.5194/egusphere-egu22-11593, 2022.

14:18–14:25
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EGU22-10699
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On-site presentation
Gabriel Bowen, Paige Austin, Scott Allen, William Anderegg, Stephen Good, David Noone, and Christopher Still

Isotope ratios of soil water and atmospheric water vapor have been used to estimate soil evaporation fluxes and to partition evapotranspiration at local (plot, stand) scales, but the application of these methods has been limited by 1) challenges associated with data acquisition, and 2) the complexity of and lack of consensus about appropriate data interpretation methods. New initiatives that have expanded access to data, such as the U.S. National Ecological Observatory Network (NEON), are beginning to address the first of these limitations. In order to make progress toward the second, we link a model of soil water and water isotope balance, based on the widely used Noah land surface model, to a range of core NEON measurements and ancillary field-collected data using a Bayesian hierarchical framework. This model framework allows self-consistent treatment of the water and isotope cycles, including representation of uncertainties and differing assumptions, and simultaneous optimization of all model parameters conditioned on all data using Markov-Chain Monte Carlo sampling. We test the framework by applying it to estimate evapotranspiration partitioning at a dryland NEON site in central Utah and show that the posterior estimates give reasonable and useful constraints on flux rates and provide constraints on model parameters that could inform our understanding of soil properties and isotopic systematics in the system. This flexible framework for interpretation of water isotope data in evapotranspiration studies is amenable to application across ecosystems and at sites with different levels of data availability in support of cross-site syntheses and validation/testing of earth system models.

How to cite: Bowen, G., Austin, P., Allen, S., Anderegg, W., Good, S., Noone, D., and Still, C.: Quantifying and partitioning evapotranspiration using Bayesian inversion of an isotope-enabled soil water balance model, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10699, https://doi.org/10.5194/egusphere-egu22-10699, 2022.

14:25–14:32
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EGU22-6602
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Highlight
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Presentation form not yet defined
Adrià Barbeta, Miriam Coenders-Gerrits, Josie Geris, Tamara Jakovljević, Pilar Llorens, Hannu Marttila, Kazakis Nerantzis, Natalie Orlowski, Emel Zeray Öztürk, Daniele Penna, Andrea L. Popp, Youri Rothfuss, Francesca Scandellari, Michael Stockinger, Christine Stumpp, Ilja van Meerveld, Jana von Freyberg, Polona Vreča, and Petra Žvab Rožič

The WATSON COST Action (CA19120; https://watson-cost.eu/) started in September 2020. It aims to integrate and synthesize current interdisciplinary scientific knowledge on the use of the stable isotopes of water to understand the mixing and partitioning of water in the Earth’s Critical Zone. The network is organized into working groups that focus on a major scientific challenge: 1) groundwater recharge and soil water mixing processes; 2) vegetation water uptake and transpiration; and 3) catchment-scale residence time and travel times. A fourth working group organizes the network and dissemination activities.

WATSON aims at better connecting academia and stakeholders from industry, non-profit organizations, and government agencies. WATSON fosters the exchange of information and expertise among scientists and stakeholders, builds capacity in the use of the latest isotope approaches and translates scientific cutting-edge knowledge into tangible outputs and recommendations on how to use stable water isotopes to effectively address water management needs. 

Our poster describes the WATSON network, as well as its activities. These include the preparation of an open-access database of water isotope-based studies in the Critical Zone, the development of protocols for water sampling and stable isotope analysis, the organization of virtual and in-person meetings, seminars, training schools, and the exchange of students, researchers, and technicians via short term scientific missions.

How to cite: Barbeta, A., Coenders-Gerrits, M., Geris, J., Jakovljević, T., Llorens, P., Marttila, H., Nerantzis, K., Orlowski, N., Öztürk, E. Z., Penna, D., Popp, A. L., Rothfuss, Y., Scandellari, F., Stockinger, M., Stumpp, C., van Meerveld, I., von Freyberg, J., Vreča, P., and Žvab Rožič, P.: The WATSON COST Action: Water isotopes in the critical zone from groundwater recharge to plant transpiration, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6602, https://doi.org/10.5194/egusphere-egu22-6602, 2022.

Coffee break
Chairpersons: Jesse Radolinski, Natalie Orlowski, Magali Nehemy
15:10–15:11
15:11–15:18
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EGU22-339
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ECS
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On-site presentation
Ann-Marie Ring, Dörthe Tetzlaff, Birgit Kleinschmit, and Chris Soulsby

Urban green spaces are valuable infrastructure in the urban environment because they facilitate natural stormwater management through rainwater retention, decelerated runoff and enhanced evapotranspiration which can also mitigate heat stress. Investigating the complex interactions of water flux partitioning of incoming precipitation into “green” (i.e. evaporation and transpiration) and “blue” (surface runoff and groundwater recharge) water fluxes through urban vegetation is crucial to understand what types of landcover might best balance water re-distribution for a particular geographical setting and provide a cooling effect whilst not compromising groundwater recharge.

Stable water isotopes are very useful tools to investigate these complex processes. So far, studies investigating high-resolution ecohydrological process dynamics at the urban soil-plant-atmosphere interface, e.g. canopy evaporation, with stable isotopes are rare. Here, we conducted novel field experiments using direct in-situ monitoring of the isotope composition of evaporated atmospheric moisture at different heights above the soil surface, plant xylem and soil water in different types of urban greenspaces in Berlin, Germany. Results show a more homogenous spatio-temporal distribution of water vapour signals within the elevation profile of urban trees compared to grasslands, reflecting continuous interplay of interception evaporation, transpiration and soil evaporation. Additionally, grasslands showed a lower impact on the isotopic composition of atmospheric water vapor, mainly reflecting higher evaporative losses close to the ground surface. Complex patterns of precipitation fractionation under contrasting urban vegetation canopies were also revealed. Topsoil moisture rates strongly depended on the soil type and less on the above vegetation type.

The collected data on the redistribution of urban water in different types of green spaces is very helpful for the development of isotope aided ecohydrological models. This knowledge can further support valuable decision-making for sustainable urban development across scales.

How to cite: Ring, A.-M., Tetzlaff, D., Kleinschmit, B., and Soulsby, C.: Urban Moisture (Re)cycling: quantifying canopy effects using in-situ water stable isotope monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-339, https://doi.org/10.5194/egusphere-egu22-339, 2022.

15:18–15:25
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EGU22-374
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ECS
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On-site presentation
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Jessica Landgraf, Dörthe Tetzlaff, Maren Dubbert, and Chris Soulsby

Ecohydrological fluxes in the critical zone are characterised by complex interactions between soils, plants, and the atmosphere. Vegetation and land use therefore play a crucial role in forming the interface between the soil and atmosphere, and spatial variation in land management within a catchment can have a dominant influence on water partitioning. Consequently, in drought sensitive environments there is a need for careful assessment of the water use of different land use types, likely resilience to future climate change and implications for groundwater recharge and runoff.

We monitored isotopes in precipitation, soil water and groundwater over the growing season of 2021 (March – October) under 8 plots with contrasting land cover in the drought-sensitive Demnitzer Millcreek Catchment (DMC) in NE Germany. These encompassed traditional arable crops, cropping schemes with water conservation measures (e.g. syntropic crops and agroforestry), grasslands and contrasting forests. The isotope monitoring was complemented with a flux tower, forest sap flow monitoring, pasture lysimetry and soil moisture measurements to provide hydroclimatic and ecohydrological context.

The growing season of 2021 being relatively wet compared to the drought years of 2018-20. Nevertheless, ET was high and soil moisture declined from May onward with only a large (60mm) event in June substantially replenishing the soil water storage before more general re-wetting in autumn. Soil moisture availability was generally highest under grassland and syntropic crops and lowest under forests. In general, precipitation isotopic composition varied during the summer, and was largely tracked by soil water isotopes, though at all sites variations were increasingly damped and lagged with depth. Soil water isotopes generally plotted close to the local meteoric water line, with limited effects of soil evaporation showing differences in interception and transpiration mainly explained the differences in soil moisture between sites. Estimates of soil water ages showed that the upper soils of arable sites had the greatest variability in isotopic composition and most rapid turnover of water, whilst soil water under trees had more limited isotopic variability, was much older and showed low levels of groundwater recharge.

Our study illustrated the advantage of monitoring the spatial variability of natural stable water isotope abundance in soil-vegetation systems to understand heterogeneity in water partitioning. Further, conservation measures like syntropic agriculture were tentatively shown to be a useful adaptation against dryer climatic conditions as this site was able to retain the highest proportion of precipitation in the soil for crop growth. However, monitoring over multiple growing seasons with contrasting hydroclimatic conditions is needed for a fuller assessment.

How to cite: Landgraf, J., Tetzlaff, D., Dubbert, M., and Soulsby, C.: Stable water isotopes reveal the effects of land use on ecohydrological partitioning in a drought-sensitive mixed land-use catchment , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-374, https://doi.org/10.5194/egusphere-egu22-374, 2022.

15:25–15:32
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EGU22-11815
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ECS
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Virtual presentation
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Yafei Li, Franziska Aemisegger, Andreas Riedl, Nina Buchmann, and Werner Eugster

During dry spells, non-rainfall water (hereafter NRW) mostly formed from dew and fog potentially plays an increasingly important role in temperate grassland ecosystems with ongoing global warming. Dew and radiation fog occur in combination during clear and calm nights, and both use ambient water vapor as a source. Research on the combined mechanisms involved in NRW inputs to ecosystems is rare, and distillation of water vapor from the soil as a NRW input pathway for dew formation has hardly been studied. Furthermore, eddy covariance (EC) measurements are associated with large uncertainties on clear, calm nights when dew and radiation fog occur. The aim of this paper is thus to use stable isotopes as tracers to investigate the different NRW input pathways into a temperate Swiss grassland at Chamau during dry spells in summer 2018. Stable isotopes provide additional information on the pathways from water vapor to liquid water (dew and fog) that cannot be measured otherwise. We measured the isotopic composition (δ18O, δ2H, and d = δ2H − 8⋅δ18O) of ambient water vapor, NRW droplets on leaf surfaces, and soil moisture and combined them with EC and meteorological observations during one dew-only and two combined dew and radiation fog events. The ambient water vapor d was found to be strongly linked with local surface relative humidity (r = −0.94), highlighting the dominant role of local moisture as a source for ambient water vapor in the synoptic context of the studied dry spells. Detailed observations of the temporal evolution of the ambient water vapor and foliage NRW isotopic signals suggest two different NRW input pathways: (1) the downward pathway through the condensation of ambient water vapor and (2) the upward pathway through the distillation of water vapor from soil onto foliage. We employed a simple two-end-member mixing model using δ18O and δ2H to quantify the NRW inputs from these two different sources. With this approach, we found that distillation contributed 9–42% to the total foliage NRW, which compares well with estimates derived from a near-surface vertical temperature gradient method proposed by Monteith in 1957. The dew and radiation fog potentially produced 0.17–0.54 mm d-1 NRW gain on foliage, thereby constituting a non-negligible water flux to the canopy, as compared to the evapotranspiration of 2.7 mm d-1. Our results thus underline the importance of NRW inputs to temperate grasslands during dry spells and reveal the complexity of the local water cycle in such conditions, including different pathways of dew and radiation fog water inputs.

How to cite: Li, Y., Aemisegger, F., Riedl, A., Buchmann, N., and Eugster, W.: The role of dew and radiation fog inputs in the local water cycling of a temperate grassland during dry spells in central Europe, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11815, https://doi.org/10.5194/egusphere-egu22-11815, 2022.

15:32–15:39
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EGU22-3448
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Presentation form not yet defined
Daniele Penna, Paolo Benettin, Andrea Dani, Francesca Sofia Manca di Villahermosa, Matteo Verdone, Giulia Pastacaldi, Carlo Andreotti, and Massimo Tagliavini

Understanding water availability and sources for crop transpiration is essential for sustainable management of water resources in agriculture, especially under changing climatic conditions. Identifying the origin of water accessed by crops is particularly critical in typical rain-fed agroecosystems, such as vineyards in Mediterranean regions where viticulture is one of the mainstays of the local economy.

As far as we know, no study so far has attempted to analyse root water uptake dynamics on hilly vineyards where the hillslope topography plays a role on water redistribution and availability for grapevine uptake. For this reason, we instrumented two plots within a vineyard in the famous Chianti wine region in Tuscany, Italy. The vineyard is cultivated with 11-year-old grapevines either on 1103 Paulsen or 420A rootstocks, which are typically characterized by a deeper and shallower rooting system, respectively. We aimed to test the hypothesis that i) grapevines located at the hillslope bottom took up water from shallower soil layers compared to grapevines located at the hillslope top due to lateral downslope redistribution of infiltrated rainwater; and that ii) grapevines with rootstock 1103 Paulsen took up water from deeper soil layers compared to the grapevines with rootstock 420A.

We monitored precipitation and temperature as well as soil moisture at 30 and 60 cm depth at two hillslope locations (top and bottom, 140 and 115 m asl, respectively) from April to October 2021. We collected samples for isotopic analysis from rainfall, soil at 30 and 60 cm, shoots and leaves from two adjacent grapevines for each rootstock at the two hillslope locations. Additional water samples were taken through the application of sealed plastic bags around some top branches and collection of water that had transpired and condensed on the bag walls. Water from soil samples, leaves and shoots was extracted though cryogenic vacuum distillation. The isotopic composition was determined through laser spectroscopy or, for organically-contaminated samples, mass spectrometry.

Preliminary results show that soil moisture was higher at the hillslope bottom than at the top, and higher at 60 than 30 cm depth. The isotopic composition of soil water was statistically different at the two depths with more enriched values in the shallower layer, as expected in Mediterranean climates; however, no statistical difference was observed between soil water at the two hillslope locations. The isotopic composition of plant water between the two locations was statistically different for bag (transpired) water and leaf water (although the latter was highly fractionated), but not for shoot water, allowing us only to partially accept hypothesis i). However, the isotopic composition of bag, leaf, and shoot water was always similar for 1103 Paulsen and 420A grafted plants, suggesting that grapevines with different rootstock took up soil water from the same depth in the study vineyard, and leading us to reject hypothesis ii).

These results contribute to better understand water uptake sources in economically-valuable agroecosystems such as vineyards.

How to cite: Penna, D., Benettin, P., Dani, A., Manca di Villahermosa, F. S., Verdone, M., Pastacaldi, G., Andreotti, C., and Tagliavini, M.: Do hillslope position and rootstock matter in root water uptake by grapevines? A case study in a Tuscany vineyard, Italy , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3448, https://doi.org/10.5194/egusphere-egu22-3448, 2022.

15:39–15:46
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EGU22-9888
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ECS
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Presentation form not yet defined
Jesse Radolinski, Herbert Wachter, Steffen Birk, Nicolas Brüggemann, Markus Herndl, Ansgar Kahmen, Angelika Kübert, Andreas Schaumberger, Christine Stumpp, Matevz Vremec, Christiane Werner, and Michael Bahn

Rapid alteration of Earth’s climate amplifies concerns over the future quantity and quality of freshwater resources. Earth’s warming atmosphere is known to store and transport more water vapor at higher velocities than historic climatic conditions, augmenting the magnitude and frequency of extreme weather events like intense rainfall and droughts. Warming can accelerate evapotranspiration by elevating vapor pressure gradients, whereas atmospheric CO2 enrichmentcan suppress transpiration as plants preferentially close their stomata. Despite the potential hydrological implications, no study to date has comprehensively explored how these global change factors, when combined, impact the transit of moisture through the soil-plant-atmosphere continuum. In a montane grassland we tracked an extensive deuterium-labelled rainfall event following a severe experimental drought period under current versus simulated future (+300 ppm CO2 and +3°C warming) conditions. We monitored stable isotopes of water in soil and evapotranspiration vapor, to partition signatures of evaporation, transpiration, drainage and soil pore water and quantify transit times through each ecohydrological compartment. Preliminary results suggest that under future conditions (+300 ppm CO2 and 3°C) drought can drastically increase the retention time of water in the rootzone, which intermittently forces plants to return older water to the atmosphere. We intend to use these findings to directly quantify the water age preference of evaporative and drainage fluxes under a range of climate scenarios.

How to cite: Radolinski, J., Wachter, H., Birk, S., Brüggemann, N., Herndl, M., Kahmen, A., Kübert, A., Schaumberger, A., Stumpp, C., Vremec, M., Werner, C., and Bahn, M.: Impact of elevated CO2, temperature, and drought on summer ecohydrological moisture cycling and water transit times in montane grassland, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9888, https://doi.org/10.5194/egusphere-egu22-9888, 2022.

15:46–15:53
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EGU22-1127
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ECS
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On-site presentation
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Paulina Alejandra Deseano Diaz, Dagmar van Dusschoten, Angelika Kübert, Nicolas Brüggemann, Mathieu Javaux, Steffen Merz, Jan Vanderborght, Harry Vereecken, Maren Dubbert, and Youri Rothfuss

Traditional destructive plant and soil water isotopic monitoring has provided important insights into root water uptake changes in drought and evapotranspiration partitioning across scales. Recently, non-destructive isotopic monitoring coupled with laser-based spectroscopy allow a better understanding of these and other questions with a higher spatial and temporal resolution. We investigated the changes in root water uptake profiles and eco-physiological characteristics (e.g. stomatal conductance, leaf water potential) of the grassland species Centaurea jacea under varying environmental conditions (i.e. atmospheric demand, soil water availability) with a labeling experiment in fully-controlled laboratory conditions. We measured non-destructively the isotopic composition of soil water and of plant transpiration. With these measurements, daily root water uptake profiles were obtained using a multi-source mixing model embedded in a Bayesian statistical framework. We analyzed the daily changes of these profiles together with changes in environmental conditions and plant physiology-related variables to discover potential adaptation strategies of C. jacea to water scarcity. Even in a dry soil (~ 10% soil water content), the studied grassland species was able to sustain high transpiration rates. This was accompanied by a very negative leaf water potential (~-3 MPa). Root water uptake profiles in both dry and wet conditions were very similar: root water uptake was highest in the soil layer 0-15 cm (up to 87%) and second highest (up to 40%) in the soil layer 45-60 cm. Before soil water content dropped below 12%, transpiration rate was mainly controlled by vapor pressure deficit. After this, a reduction of canopy conductance restricted gas leaf exchange. Instantaneous water use efficiency dropped when the soil was very dry, but intrinsic water use efficiency was maintained. Our comprehensive data set of plant-related and environmental variables allowed us to investigate at a 1-cm and daily scales the plant’s response to varying hydro-climatic conditions.

How to cite: Deseano Diaz, P. A., van Dusschoten, D., Kübert, A., Brüggemann, N., Javaux, M., Merz, S., Vanderborght, J., Vereecken, H., Dubbert, M., and Rothfuss, Y.: Investigating root water uptake dynamics of a grassland species under varying hydro-climatic conditions with non-destructive isotopic monitoring, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1127, https://doi.org/10.5194/egusphere-egu22-1127, 2022.

15:53–16:00
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EGU22-12306
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ECS
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On-site presentation
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Marius G. Floriancic, Scott T. Allen, and James W. Kirchner

Forests greatly impact the water cycle by redistributing water between the atmosphere and the subsurface, via processes including interception, infiltration, and transpiration. In order to understand which water is redistributed among different ultimate fates, and thereby better understand the role of vegetation in that process, we use stable isotopes to quantify transport processes across the different compartments of the forest water cycle. At our Waldlabor hillslope laboratory (Zurich, Switzerland) we have frequently measured and sampled water fluxes across the forest water cycle since April 2020. Specifically, we measure the isotopic composition in precipitation, throughfall, stemflow, bulk and mobile soil waters in depths of 10, 20, 40 and 80cm as well as in deep mobile water (from boreholes in the unsaturated zone up to 7m depth), groundwater and surface discharge at the outlet of the catchment. We also assess soil water uptake by beech and spruce trees from destructive sampling of twig xylem every three weeks.

The isotopic composition in precipitation was similar to what we found in throughfall and stemflow, so canopy interception processes did not substantially alter the isotopic signal. The seasonal variation in precipitation isotope composition was strongly dampened with depth in subsurface storages (through the soil layers, deep mobile water, and groundwater to streamflow). The assessment of the new water fractions in soil waters of different depths and the deeper soil drip water showed that the fractions of new precipitation in each layer decreased with depth. Although precipitation is almost equally distributed throughout the year, we found that soil new water fractions were generally smaller in summer compared than in winter. Water in spruce and beech xylem has a similar isotope signal throughout the year, potentially suggesting use of deep sources that contain a relatively stable mixture of summer and winter water. Together, these data provide opportunities for new perspectives on how subsurface flows and vegetation interact.

How to cite: Floriancic, M. G., Allen, S. T., and Kirchner, J. W.: Isotopic signals across the forest water cycle, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12306, https://doi.org/10.5194/egusphere-egu22-12306, 2022.

16:00–16:07
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EGU22-5313
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ECS
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On-site presentation
Ginevra Fabiani, Julian Klaus, Remy Schoppach, and Daniele Penna

Topography plays a major role in mediating subsurface water redistribution and ultimately water availability for tree transpiration. Trees located in valley bottoms commonly benefit from greater accessibility to groundwater and wetter soil from lateral redistribution of water compared to trees growing upslopes. However, water availability and movement in the subsurface may differ according to subsurface properties (permeability, soil texture, geology) and climatic regimes. The spatially and seasonally variable water accessibility along a hillslope affects species composition, stand structure, and biomass productivity resulting in areas which will be more likely impacted by potential water shortages. So far, the understanding of how hydrological processes occurring at the hillslope scale affect tree water use is still limited, rising the need of measurements at hillslope-level to allow deeper comprehension of forest dynamic and survival.

Here, we set up a comparative study on a gentle and very steep forested hillslope located in the Weierbach catchment (Luxembourg) and the Re della Pietra catchment (Italy), respectively. We aimed at testing if different climatic and hydrological conditions, i.e., meteorological forcing, groundwater depth, soil moisture, and water redistribution affect water use patterns of beech trees (Fagus sylvatica L.) along hillslopes.

We monitored soil moisture, groundwater level, sap velocity, and hydro-meteorological variables and determined the isotopic composition of precipitation, soil water, groundwater, and xylem water to estimate tree water sources. The combination of these measurements allows us to link the transpiration response of trees to water availability along the two different hillslopes.We carried out biweekly field campaigns during the growing season 2019 and 2020 in Weierbach catchment and throughout 2021 in Re della Pietra catchment to sample xylem water, soil water at different depths, groundwater, stream water, and precipitation.

Trees in the Weierbach catchment rely on water stored in the unsaturated zone regardless of the hillslope position and the hydrologic conditions of the season. On the contrary, preliminary results from Re della Pietra suggest position-specific water use strategy. Trees located at the footslope experienced longer vegetative period compared to plants located at the midslope and hilltop locations due do larger soil moisture content recorded at the footslope. Additionally, xylem water of footslope trees displayed lighter isotopic composition compared to other trees, suggesting the use of a less fractionated water sources.

We argue that contrary to the Weierbach catchment where subsurface hillslope structure promotes vertical water flux over lateral redistribution in the vadose zone, the steep hillslope on the Re della Pietra catchment experiences shallow lateral downslope water redistribution which results in substantial differences in vadose zone water supply between hillslope positions.

How to cite: Fabiani, G., Klaus, J., Schoppach, R., and Penna, D.: Contrasting tree water use strategies along hillslopes in forested catchments in Luxembourg and Italy , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5313, https://doi.org/10.5194/egusphere-egu22-5313, 2022.

16:07–16:14
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EGU22-5437
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ECS
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On-site presentation
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Corinna Gall, Alexander Maurer, Julia Dartsch, Delia Maas, Martin Nebel, Harald Neidhardt, Yvonne Oelmann, Thomas Scholten, and Steffen Seitz

Nonvascular plants such as bryophytes are often overlooked; however, they are important players at the soil-atmosphere interface and affecting water exchange, nutrient fluxes or carbon storage. Bryophytes also act as soil stabilizers in a variety of ecosystems and thus contribute significantly to the mitigation of soil erosion. Nevertheless, these stabilizing effects are not completely understood, with two distinctions: Firstly, bryophytes form a physical protective barrier that prevents direct drop impact on soil. Secondly, they fix carbon and thus contribute to soil carbon storage, which in turn enhances soil aggregation. Both factors result in a reduction of soil erosion, although it is unclear to what extent. As bryophytes showed a high impact on carbon assimilation and soil carbon storage in boreal environments, gaining an understanding of these effects in a temperate forest can be a key factor in assessing the overall state of that ecosystem.

In this study, we used the stable carbon isotope ratio (δ13C) analysis as an approach to evaluate the effect of bryophytes on soil organic carbon (SOC). Furthermore, we investigated the influence of SOC on aggregate size. Soil substrates and bryophyte species were sampled in temperate forests in southern Germany with different kinds of parent material. Five sites were located in Schönbuch Nature Park next to Tübingen and one site in the Black Forest close to Freiburg. Each study site consisted of three treatments: bryophyte-covered patches, bare undisturbed soil and partial disturbed soil from forest management. In this context, it was hypothesized that there is a significant contribution of bryophytes to SOC, which is reflected by a change in isotopic signatures and aggregate sizes. Consequently, bryophyte-covered soils are assumed to exhibit higher SOC contents, form larger soil aggregates and for this reason be more resistant to soil erosion, and the contribution of bryophytes to SOC can be estimated based on the differences in the δ13C of bryophytes compared to C3 plants.

Preliminary results of two study sites revealed a distinct positive correlation between SOC and aggregate size, whereby a contribution of bryophytes to SOC could not yet be established based on δ13C values. This could be due to the different ecological structure of the two studied sites, the similarity of carbon isotope signatures of C3 plants and bryophytes, the alteration of isotope signature as a result of decomposition, and the combination of all these factors. Laboratory and data analysis of the four remaining sites is currently ongoing, so further results will be presented at EGU 2022.

How to cite: Gall, C., Maurer, A., Dartsch, J., Maas, D., Nebel, M., Neidhardt, H., Oelmann, Y., Scholten, T., and Seitz, S.: Investigating the effects of bryophytes on carbon cycling in a temperate forest ecosystem from stable isotope composition, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5437, https://doi.org/10.5194/egusphere-egu22-5437, 2022.

16:14–16:21
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EGU22-8620
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ECS
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On-site presentation
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Kathrin Kühnhammer, Joost van Haren, Angelika Kübert, Maren Dubbert, Nemiah Ladd, Laura Meredith, Christiane Werner, and Matthias Beyer

Due to ongoing and likely intensifying climate change impacts, ecosystem water availability is altered across the globe. Humid tropical forests, which evolved under conditions of abundant water, might be particularly vulnerable to water stress. One important factor in a tree's resilience to a less reliable water supply from precipitation is a root system that reaches deep into the ground. However, accessing deep soil regions as well as observing active deep root water uptake is challenging. Consequently, the occurrence, functioning and importance of deep roots are not well understood.

The Biosphere 2 Tropical Rainforest in Arizona, USA offers a unique possibility to further investigate this knowledge gap as environmental conditions can be controlled and soil can be accessed from below. Within the interdisciplinary B2 WALD project, we imposed a two-month drought on the enclosed ecosystem. To identify deep water uptake, water labeled with 2H isotopes was supplied through a drainage system in 2-3 m soil depth before the drought ended. To investigate tree reactions to the manipulations in water supply, we closely monitored atmospheric conditions, soil water content and isotopic composition as well as tree sap flow, stem water content and the isotopic composition of tree xylem and transpired water. Only few data sets exist, combining water stable isotope information with different hydrometric measurements within the same experiment. Additionally, we used novel in situ approaches to monitor the isotopic composition in soils, tree xylem and transpiration in high temporal resolution.

Combining all measurements in 10 tree individuals of 5 different species, we found contrasting reactions to the added deep water. Except of two understory trees, all canopy trees had access to it, suggesting that deep roots could be a common feature also in tropical tree species. Trees did not use deep water in the same way. We observed differences in the speed and timing of the reaction as well as in within-tree water dynamics. While some individuals first refilled their stem water storage, others used the deep water source to preserve their sap flow and transpiration stream. This not only impacted the time course of tree water isotopes but knowledge of those different behaviors is pivotal in better understanding and predicting tree performance, survival and ecosystem water cycling. In summary, our data illustrates the need for an extensive network combining different measurements to correctly interpret tree water isotope dynamics, tree water use strategies and to further uncover the functioning of deep roots and assess their importance for ecosystem resilience in a changing climate.

How to cite: Kühnhammer, K., van Haren, J., Kübert, A., Dubbert, M., Ladd, N., Meredith, L., Werner, C., and Beyer, M.: In situ monitoring of tree water uptake depths, storage and transport reveals different strategies during drought and recovery, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8620, https://doi.org/10.5194/egusphere-egu22-8620, 2022.

16:21–16:28
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EGU22-9870
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ECS
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On-site presentation
Diego Todini and the PRIN WATZON

Stable isotopes (2H and 18O) are common natural tracers for the investigation of water transport in the soil-plant-atmosphere continuum. Isotopic data can be coupled with soil water content data to inversely estimate soil hydraulic and transport parameters. The calibration of a hydrological model by inverse modelling is a prerequisite to determine the temporal origin of xylem water taken by roots.

In this study, we used isotopic data to calibrate Hydrus-1D via inverse modelling to simulate one-dimensional water flow and isotope transport in a controlled soil-plant-atmosphere system. We propose the following protocol i) to estimate root water uptake transit time of irrigation water, and ii) to assess the sensitivity of the transit time distribution to the variation in the water available for root uptake.

The dataset was obtained from an isotope-tracing experiment carried out between May and July 2018 on an olive tree placed in a pot inside a glasshouse. Meteorological variables and sap flow were monitored at 5-minute intervals, whereas shallow soil moisture (0-6 cm depth) was measured manually with an impedance probe at the daily timescale. The olive tree was irrigated with water of known isotopic composition. The pot surface was covered by a plastic sheet to avoid evaporation. Soil at different depths, twigs, wood cores and root samples were collected weekly for isotopic analyses. Water from soil and the xylem tissues was extracted by cryogenic vacuum distillation. Based on the results of a previous study carried out on the same dataset, we considered that no isotopic fractionation occurred during the water uptake and the transport within the olive tree.

We used soil water content and δ18O data at different soil depths to optimize flow (soil hydraulic and root water uptake parameters) and transport (longitudinal dispersivity) parameters. Numerical simulations of isotope transport were validated with sap flow data (compared to actual transpiration) and δ18O in xylem water. Given that the timing of irrigation water for plant transpiration is fundamental for assessing the vulnerability of olive trees to drought, we will be proposing various scenarios based on different irrigation events to mimic drought periods. Based on these scenarios, we will be evaluating the sensitivity of the root water uptake transit time to the different water availability in the soil profile. Afterwards, the same protocol will be exploited to determine the root water uptake transit time for different tree species under various environmental conditions.

Keywords: stable isotopes, HYDRUS-1D, root water uptake, transit time, soil water.

How to cite: Todini, D. and the PRIN WATZON: Assessing root water uptake transit time by simulating isotope transport in Hydrus-1D, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9870, https://doi.org/10.5194/egusphere-egu22-9870, 2022.