scholarly journals Enhancing the Noah‐MP Ecosystem Response to Droughts With an Explicit Representation of Plant Water Storage Supplied by Dynamic Root Water Uptake

2020 ◽  
Vol 12 (11) ◽  
Author(s):  
Guo‐Yue Niu ◽  
Yuan‐Hao Fang ◽  
Li‐Ling Chang ◽  
Jiming Jin ◽  
Hua Yuan ◽  
...  
Keyword(s):  
Water Uptake ◽  
Water Storage ◽  
Root Water Uptake ◽  
Explicit Representation ◽  
Plant Water ◽  
Ecosystem Response

Quantifying how plants with different species-specific water-use strategies cope with the same drought-prone hydro-ecological conditions

2020 ◽  
Author(s):  
Deepanshu Khare ◽  
Gernot Bodner ◽  
Mathieu Javaux ◽  
Jan Vanderborght ◽  
Daniel Leitner ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Drought Stress ◽  
Water Potential ◽  
Water Uptake ◽  
Hydraulic Properties ◽  
Root Water Uptake ◽  
Leaf Water ◽  
Plant Water ◽  
Soil Hydraulic Properties ◽  
Stomatal Control

<p>Plant transpiration and root water uptake are dependent on multiple traits that interact with site soil characteristics and environmental factors such as radiation, atmospheric temperature, relative humidity, and soil-moisture content. Models of root architecture and functions are increasingly employed to simulate root-soil interactions. Root water uptake is thereby affected by the root hydraulic architecture, soil moisture conditions, soil hydraulic properties, and the transpiration demand as controlled by atmospheric conditions. Stomatal conductance plays a vital role in regulating transpiration in plants. We performed simulations of plant water uptake for plants having different mechanisms to control transpiration, spanned by isohydric/anisohydric spectrum. Isohydric plants follow the strategy to close their stomata in order to maintain the leaf water potential at a constant level, while anisohydric plants leave their stomata open when leaf water potentials fall due to drought stress. Modelling the stomatal regulation effectively will result in a more reliable model that will regulate the excessive loss of water. We implemented hydraulic and chemical stomatal control<br>of root water uptake following the current approach where stomatal control is regulated by simulated water potential and/or chemical signal concentration. In order to maintain water uptake from dry soil, low plant water potentials are required, which may lead to reversible or permanent cavitation. We parameterise our model with field data, including climate data and soil hydraulic properties under different tillage conditions. This helps us to understand the behaviour of different crops under drought conditions and predict at which growing stage the stress hits the plant. We conducted the simulations for different scenarios to study the effect of hydraulic and chemical regulation on root system performance under drought stress.</p>

Tracing plant water fluxes in ecosystems by stable isotopes along the soil-plant and plant-atmosphere interfaces

2020 ◽  
Author(s):  
Christiane Werner
Keyword(s):  
Water Uptake ◽  
Large Scale ◽  
Temporal Dynamics ◽  
Root Water Uptake ◽  
Plant Water ◽  
Water Fluxes ◽  
Terrestrial Vegetation ◽  
Species Specific ◽  
The Impact

<p>Terrestrial vegetation is a main driver of ecosystem water fluxes, as plants mediate the water fluxes within the soil-vegetation-atmosphere continuum. Stable isotopologues of water are efficient tracer to follow the water transfer in soils, uptake by plants, transport in stems and release into the atmosphere through stomata. The development of in-situ methods coupled to isotope spectroscopy does now enable real-time in-situ water vapour isotopologue measurements revealing high spatial and temporal dynamics, such as adaptations in root water uptake depths (within hours to days) or the impact of transpirational fluxes on atmospheric moisture.</p><p>Examples will be given how isotopes can be used to inform the complex interplay between plant ecophysiological adaptations and hydrological processes. For example, root water uptake is not solely driven by soil water availability but has to be understood in the context of species-specific regulation of active zones in their rooting system determining the conductivity between soil and roots regulating uptake depths. The latter has also to be evaluated in context of the nutrient demand and the spatial nutrient availability. Similarly, plant water transport and losses are a fined tuned interplay between species-specific structural and functional adaptations and atmospheric processes.</p><p>Finally, first data of a large-scale ecosystem labelling experiment at the Biosphere 2 tropical rainforest of the B2 Wald, Atmosphere, and Live Dynamics (B2WALD) will be presented.</p>

Inferring plant physiologic parameters for root water uptake modelling from high frequency in-situ isotope measurements

2020 ◽  
Author(s):  
Stefan Seeger ◽  
Michael Rinderer ◽  
Markus Weiler
Keyword(s):  
Soil Moisture ◽  
Water Uptake ◽  
Root Distribution ◽  
Fine Root ◽  
Root Water Uptake ◽  
Plant Water ◽  
Plant Water Uptake ◽  
Fine Root Distribution ◽  
Isotope Measurements

<p>In the face of global climate change, a well-informed knowledge of plant physiologic key parameters is essential to predict the behavior of ecosystems in a changing environment. Many of these parameters may be determined with lab or pot experiments, but it could prove problematic to transfer results obtained in a such experiments with small trees to fully grown trees. Therefore, new approaches to determine relevant parameters for mature trees are still required. Regarding plant water uptake, parameters related to fine root distribution (maximum depth, depth distribution and rhizosphere radius) and parameters describing the physiological limits of root water uptake are important, but usually hard or costly to assess for fully grown trees.  In-situ isotope probes (Volkmann et al. 2016a  & 2016b) are a promising recent development that offer new possibilities for the investigation of plant water uptake and associated physiological parameters.</p><p>In this study we used in-situ stable water isotope probes in soil (six depths from 10 to 100 cm) and in tree xylem of mature (140 years) European beech trees (three heights between 0 and 8 m). With those probes, we monitored soil and xylem isotope signatures after an isotopically labeled (Deutrium-Excess = 100 ‰) irrigation pulse equivalent to 150 mm of precipitation and foursubsequent natural precipitation events over a period of twelve weeks with a high temporal resolution (six or more measurements per probe per day). Those measurements were complemented with measurements of soil moisture and sap flow dynamics. We interpolated our measured soil isotope and soil moisture data in order to obtain spatially and temporally continuous data for those soil parameters. Then we used this data as an input to the Feddes-Jarvis plant water uptake model, in order to predict the isotopic signature of plant water uptake at daily time steps. With the help of our observed isotopic signatures, we were able to directly constrain the critical water potential parameter of the Feddes model as well as the underlying fine root distribution. Furthermore, the observed dampening of the breakthrough curve of our Deuterium-labeling pulse allowed us to infer information on the rhizosphere  radius and water transport velocities in the fine roots and stem between the points of root water uptake and the eight meter stem height.</p><p>With our field experiment we showed that in-situ isotope measurements in soil profiles and in tree xylem sap can help to constrain plant water uptake modelling parameters. Future experiments might use this approach to scrutinize lab-scale derived hypothesizes regarding tree water uptake and to investigate the temporal and spatial dynamics of root water uptake in the field.</p><p> </p><p><em>Volkmann, T. H., Haberer, K., Gessler, A., & Weiler, M. (2016a). High‐resolution isotope measurements resolve rapid ecohydrological dynamics at the soil–plant interface. New Phytologist, 210(3), 839-849. </em></p><p><em>Volkmann, T. H., Kühnhammer, K., Herbstritt, B., Gessler, A., & Weiler, M. (2016b). A method for in situ monitoring of the isotope composition of tree xylem water using laser spectroscopy. Plant, cell & environment, 39(9), 2055-2063. </em></p><p><em>Jarvis, N. J. (1989). A simple empirical model of root water uptake. Journal of Hydrology, 107(1-4), 57-72. </em></p>

scholarly journals X Water Worlds and how to investigate them: A review and future perspective on <i>in situ</i> measurements of water stable isotopes in soils and plants

2019 ◽  
Author(s):  
Matthias Beyer ◽  
Maren Dubbert
Keyword(s):  
Stable Isotopes ◽  
Water Uptake ◽  
Isotope Effects ◽  
Root Water Uptake ◽  
Future Research ◽  
Plant Water ◽  
Research Needs ◽  
In Situ Methods ◽  
Water Isotope

Abstract. The number of ecohydrological studies involving water stable isotopes has been increasing steadily due to technological (i.e. field deployable laser spectroscopy and cheaper instruments) and methodological (i.e. tracer approaches or improvements in root water uptake models) advances in recent years. This enables researchers from a broad scientific background to incorporate water isotope-based methods into their studies. Several isotope effects are currently not fully understood, but essential when investigating root water uptake depths of vegetation and disentangle isotope processes at the soil-vegetation-atmosphere continuum. In particular different viewpoints exist on i) extraction methods for soil and plant water and methodological artefacts potentially introduced by them; ii) the pools of water measured with those methods and iii) spatiotemporal issues related with water stable isotope research. In situ methods have been proposed as an innovative and necessary way to address these issues and are required in order to disentangle isotope effects and take them into account when studying root water uptake depths of plants and for studying soil-plant-atmosphere interaction based on water stable isotopes. Herein, we review the current status of in situ measurements of water stable isotopes in soils and plants, point out current issues and highlight potential for future research. Moreover, we put a strong focus and incorporate practical aspects into this review. Finally, we propose an integrated methodology for measuring both soil and plant water isotopes when carrying out studies at the soil-vegetation-atmosphere interface. For all in situ methods, extreme care needs to be taken particularly during set-up in order to obtain reliable data. In situ methods for soils are well established. For transpiration, reliable methods also exist but are not common in ecohydrological field studies due to the required effort. Little attention has been payed to in situ xylem water isotope measurements. Research needs to focus on improving and further developing those methods. There is a need for a consistent and combined (soils and plants) methodology for ecohydrological studies. Such systems should be designed and adapted to the environment to be studied. We further conclude that many studies currently might not rely on in situ methods extensively because of the technical difficulty. Hence, future research needs to aim on developing a simplified approach that provides a reasonable trade-off between practicability and precision/accuracy.

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

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

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

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