HS8.3.3 | Soil-Plant Interactions
EDI
Soil-Plant Interactions
Co-organized by SSS8
Convener: Martin Bouda | Co-conveners: Valentin Couvreur, Camilla Ruø Rasmussen, Mohsen Zare, Sabine J. Seidel
Orals
| Tue, 16 Apr, 14:00–15:45 (CEST), 16:15–18:00 (CEST)
 
Room 3.16/17, Wed, 17 Apr, 16:15–18:00 (CEST)
 
Room 3.16/17
Posters on site
| Attendance Wed, 17 Apr, 10:45–12:30 (CEST) | Display Wed, 17 Apr, 08:30–12:30
 
Hall A
Posters virtual
| Attendance Wed, 17 Apr, 14:00–15:45 (CEST) | Display Wed, 17 Apr, 08:30–18:00
 
vHall A
Orals |
Tue, 14:00
Wed, 10:45
Wed, 14:00
The interactions between plants and the environment play a prominent role in terrestrial fluxes and biochemical cycles. However, we still lack detailed knowledge of how these interactions impact plant growth and plant access to soil resources, particularly under deficient conditions. The main challenge arises from the complexity inherent to both soil and plants. To address these knowledge gaps, an improved understanding of plant-related transfer processes is needed.
Experimental techniques such as non-invasive imaging and three-dimensional root system modeling tools have deepened our insights into the functioning of water and solute transport processes in the soil-plant system. Quantitative approaches that integrate across disciplines and scales constitute stepping-stones to foster our understanding of fundamental biophysical processes at the interface between soil and plants.
This session targets research investigating plant-related resource transfer processes across different scales (from the rhizosphere to the global scale) and welcomes scientists from multiple disciplines encompassing the soil and plant sciences. We are specifically inviting contributions on the following topics:
- Bridging the gap between biologically and physically oriented research in soil and plant sciences
- Measuring and modeling of soil-plant hydraulics, water and solute fluxes through the soil-plant-atmosphere continuum across scales.
- Identification of plant strategies to better access and use resources from the soil, including under abiotic stress(es)
- Novel experimental and modeling techniques assessing below-ground plant processes such as root growth, root water, and nutrient uptake, root exudation, microbial interactions, and soil aggregation
- Mechanistic understanding of drought impact on transpiration and photosynthesis and their predictions by earth system models

Orals: Tue, 16 Apr | Room 3.16/17

Chairpersons: Martin Bouda, Camilla Ruø Rasmussen
14:00–14:05
14:05–14:25
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EGU24-6403
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ECS
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solicited
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On-site presentation
Hannah Schneider

The functional role and genetic control of many root anatomical and architectural traits are poorly understood. Our research focuses on characterizing root traits for enhanced stress tolerance and identifying genetic mechanisms controlling the expression of root traits. We have identified a candidate gene for root cortical aerenchyma formation which mapped to a root cortex-expressed bHLH transcription factor gene. A bHLH121 Mu transposon mutant line and a CRISPR/Cas9 loss-of-function mutant exhibited reduced root cortical aerenchyma formation, whereas an overexpression line exhibited significantly greater root cortical aerenchyma formation when compared to the wildtype line in many environments. Overall functional validation of the bHLH121 gene’s importance in root cortical aerenchyma formation provides a functional marker to select varieties with improved soil exploration and thus yield. Characterization of these lines under suboptimal water and nitrogen availability in multiple soil environments revealed root cortical aerenchyma is plastic in response to abiotic stress. Our results suggest that phenotypic plasticity is highly quantitative and plasticity loci are distinct from loci that control trait expression in stress and non-stress conditions. The identification of genes and functional phenotypes of root traits will facilitate efforts for the development of novel nutrient and water efficient crop varieties.

How to cite: Schneider, H.: Genetic Control and Phenotypic Plasticity of Root Cortical Aerenchyma in Maize, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6403, https://doi.org/10.5194/egusphere-egu24-6403, 2024.

14:25–14:35
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EGU24-12359
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On-site presentation
Elsa Coucheney, Thomas Kätterer, Katharina Meurer, and Nick Jarvis

Crop breeding to increase below-ground production and inputs of organic matter into soil has been attracting increasing attention as a potentially effective strategy to enhance soil organic matter (SOM) stocks and thus the quality of soil and sustainability of arable cropping systems. We used the new soil-crop model USSF (Uppsala model of Soil Structure and Function) to investigate the potential for increasing SOM whilst maintaining or improving yields by modifying the root system of winter wheat in terms of below-ground allocation of carbon and key root traits. USSF combines physics-based descriptions of soil water flow, water uptake and transpiration by plants, with a simple (generic) crop growth model and a model of soil structure dynamics and soil organic matter turnover that considers the effects of soil physical protection and microbial priming. 

The USSF model was first calibrated against field data on soil water contents and both above-ground and root biomass of winter wheat measured during one growing season in a clay soil in Uppsala, Sweden. Based on five acceptable calibrated parameter sets, we created four model crops (ideotypes) by modifying root-related parameters to mimic winter wheat phenotypes with improved root traits. Long-term (30-year) simulations of a conventionally tilled monoculture of winter wheat were then performed to evaluate the potential effects of cultivating these ideotypes on soil water balance, soil organic matter stocks and grain yields.

Our results suggest that exploiting winter wheat varieties that allocate more assimilate to the root system would not in itself have any positive effect on soil organic matter storage and would also decrease grain yields. In contrast, deeper root systems or root systems that are more effective for water uptake were predicted to slightly increase grain yields, as well as increasing SOM stocks in the soil profile by ca. 3 to 5%. Combining all three improved root traits showed even more promising results: compared with the baseline “business-as-usual” scenario, SOM stocks in the soil profile were predicted to increase by ca. 7% in a 30-year perspective (as an average of the five parameter sets) without negatively impacting yields.

How to cite: Coucheney, E., Kätterer, T., Meurer, K., and Jarvis, N.:  Improving the sustainability of arable cropping systems by modifying root traits: a modelling study for winter wheat, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12359, https://doi.org/10.5194/egusphere-egu24-12359, 2024.

14:35–14:45
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EGU24-7991
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ECS
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On-site presentation
Juan C. Baca Cabrera, Jan Vanderborght, Dominik Behrend, Thomas Gaiser, Thuy Huu Nguyen, Yann Boursiac, and Guillaume Lobet

Root water uptake is a pivotal process in the regulation of water movement within the soil-plant-atmosphere continuum. At a specific atmospheric demand, root water uptake is determined by the architecture of the root system and the hydraulic properties of individual roots and root segments. In agricultural settings, root traits are affected by management practices, including breeding. Specifically for wheat, the most important European crop, a decrease in root system size has been observed in modern varieties compared to historical ones1, and differences in root hydraulic properties between cultivated and wild species have been documented2. However, an assessment on the long-term evolution of root hydraulic properties with breeding is still absent.  

Here, we investigated the effect of breeding on root hydraulic properties of wheat and its implications for root water uptake at the plant scale. For this, an experiment encompassing six wheat cultivars spanning over a century of breeding history was conducted. We measured the number of root axes (crown roots and seminal roots) of plants grown in the field during the tillering phase (BBCH <30) and the root hydraulic conductivity of young plants grown in hydroponics (<12 days, no crown roots), using the pressure chamber technique.

Average root hydraulic conductivity (per root surface area) did not differ among cultivars, but a pronounced decrease in the number of root axes was observed in the most recent cultivars. Based on these observations, simulations with the whole-plant 3-D model CPlantBox were performed, indicating a higher whole-root system conductance in the oldest cultivars at the end of the tillering phase, associated with a higher number of tillers and root axes. This suggests an evolution of wheat cultivars towards more conserving root water uptake strategies, a feature of special importance under water-limited conditions.

 

References 

  • 1Zhao et al. (2005). 10.1111/j.1744-7909.2005.00043.x
  • 2Fradgley et al. (2020). 10.1007/s11104-020-04585-2 

How to cite: Baca Cabrera, J. C., Vanderborght, J., Behrend, D., Gaiser, T., Nguyen, T. H., Boursiac, Y., and Lobet, G.: Evolution of root hydraulic properties of wheat with breeding and its influence on root water uptake: insights from a field experiment and modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7991, https://doi.org/10.5194/egusphere-egu24-7991, 2024.

14:45–14:55
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EGU24-978
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ECS
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On-site presentation
Alina Azekenova, Karl-Heinz Feger, and Stefan Julich

Soil moisture in forested regions displays considerable spatial and temporal variability within the soil-plant interaction. The high frequency of drying and wetting cycles exacerbates the uncertainty in this already complex relationship. Recent studies in forest hydrology have frequently postulated that soil physical properties and precipitation partitioning induce soil water content (SWC) variability. However, in-situ evidence for this linkage is scarce. To support the notion of SWC patterns corresponding to these two elements, a transect-based method was utilised. It clarifies the variation in soil moisture on a small scale and facilitates the identification of specific patterns with the distance from the tree stem. An intensive monitoring of SWC (52 profiles) and precipitation, including throughfall and stemflow, has been carried out in the near-natural beech forest in north-eastern Germany since 2022. It covers three study sites that are stocked over a terminal moraine and are classified as wet, intermediate and dry on the basis of the soil moisture gradient. The result stipulates increase of the SWC away from the stem during drying cycles at the dry study site. However, this appears to be the reverse for the wet site. During the wetting phase, soil moisture at intermediate and dry sites exhibited homogeneous variation, although the wet site experienced an increase in soil moisture by stem distance. Therefore, uncovering the distance from stem, root density distribution and canopy structure as possible controlling factors.  It is concluded, that within soil-plant interaction both soil physics and precipitation define the patterns of soil moisture variation during wetting cycles. Conversely, soil retention characteristics mainly anticipate water fluxes in the soil during drying periods.

How to cite: Azekenova, A., Feger, K.-H., and Julich, S.: What impacts the soil moisture dynamics in the near-natural beech forest?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-978, https://doi.org/10.5194/egusphere-egu24-978, 2024.

14:55–15:05
15:05–15:15
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EGU24-1452
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ECS
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On-site presentation
Jiaojiao Yao, Jonathan Barès, Evelyne Kolb, and Lionel Dupuy

Rooting depth is critical for plants to acquire water and nutrient efficiently. However, when progressing deeper into the soil, a growing root must overcome physical obstacles such as stones and zones with different mechanical impedance (like hard pans and aggregates) which results in tortuous trajectories and a reduced ability to reach deeper soil horizons. We have developed different model systems which consists of roots growing in artificial substrates made of a customized arrays of stiff or deformable obstacles which the root can either bypass or penetrate based on the resistance of the obstacle. High-throughput imaging systems were used to capture time lapse data and image analysis techniques were used to track root responses to obstacles. In the presence of rigid obstacles, only a limited number of growth responses were observed with a transition from vertical to oblique trajectories observed as a function of size and distance between physical obstacles. When obstacles were deformable the likelihood of penetration could be predicted from factors such as the incidence angle, the length of the root that can bend freely, and the degree to which previous obstacles compress and anchor its base. Overall, our results showed that primary root growth in heterogeneous substrates is largely deterministic and can be predicted from the maximum curvature a root can bend, the spatial arrangements of obstacles and the mechanical stress anchoring the base of the root.

Keywords: root, soil, mechanical impedance, heterogeneity, biomechanics

How to cite: Yao, J., Barès, J., Kolb, E., and Dupuy, L.: The biomechanics of path of least resistance of roots in heterogeneous substrates, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1452, https://doi.org/10.5194/egusphere-egu24-1452, 2024.

15:15–15:25
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EGU24-9239
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On-site presentation
Antonello Bonfante

The SWAP model allows studying the behavior of agricultural systems at different spatial and temporal scales, addressing climate change adaptation and mitigation issues.

In recent years, it has been used in the viticultural sector to study the soil-plant-atmosphere (SPA) relationships in vineyards and to define and support the terroir concept and its resilience under climate change.

This contribution presents the results relating to the ability of the model to (i) shed light on the relationships between water stress and grape quality characteristics and (ii) evaluate the impact of climate change on the responses of the vineyard system of three vine varieties cultivated in southern Italy (Aglianico, Cabernet sauvignon and Greco).

In each case study, the calibrated and validated SWAP model output has been used to explore the relations between the plant water stress realized during the growing season and vine responses (physiological and productive responses). The identified relations were successively applied to evaluate the climate change (CC, RCP 4.5 and 8.5 ) adaptation of each vineyard system studied. Furthermore, in the case of the Aglianico grapevine, the evaluation of adaptation to CC was spatially extended to a region of southern Italy (Valle Telesina, BN; 20.000 ha) devoted to high-quality wine production, and the resilience of the terroir concept evaluated.

Finally, the strengths and limitations of SWAP application in the viticultural context will be discussed.

Keywords: grapevine, SPA system, terroir, climate change, vine water stress, grape quality.

How to cite: Bonfante, A.: SWAP model potentiality in the viticultural system study and analysis., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9239, https://doi.org/10.5194/egusphere-egu24-9239, 2024.

15:25–15:35
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EGU24-15793
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ECS
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On-site presentation
Nirali Vashishth, Souradip Dey, and Dr. Richa Ojha

Understanding spatial variation in soil hydraulic properties is important for comprehending the physical behaviour of soil and for analysing field-scale water flow and solute transfer processes. Tension disc infiltrometers are commonly used for measuring in-situ unsaturated hydraulic properties of soil. In this study, spatial variation in soil hydraulic properties is analysed for an experimental plot at IIT Kanpur, India after harvest of rice crop using tension disc infiltrometer. Measurements were taken at three different depths of 10, 25 and 50 cm and at multiple locations in the field for consecutive supply pressure heads of -12, -9, -6 and -3 cm. The measured data was analysed using HYDRUS-2D model and four Maulem-van Genutchen parameters (θs, α, n and Ks) were inversely estimated. The maximum variation was observed in α at the depth of 50 cm. The reduced variability observed in pore size distribution index (n) could be attributed to the flooded irrigation practice in rice. The findings of this study enhance our understanding of soil-water interaction in agricultural settings.

Keywords: Soil hydraulic properties, Tension disc infiltrometer, HYDRUS-2D

How to cite: Vashishth, N., Dey, S., and Ojha, Dr. R.: Spatial variation in soil hydraulic properties in an agricultural field estimated using Tension Disc Infiltrometer, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15793, https://doi.org/10.5194/egusphere-egu24-15793, 2024.

15:35–15:45
Coffee break
Chairpersons: Camilla Ruø Rasmussen, Martin Bouda
16:15–16:20
16:20–16:40
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EGU24-3773
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ECS
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solicited
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On-site presentation
Maud Tissink, Jesse Radolinski, David Reinthaler, Sarah Venier, Erich M. Pötsch, Andreas Schaumberger, and Michael Bahn

In a changing climate, grasslands are expected to experience major shifts in water supply and demand. To date, little is known about how projected future conditions of severe drought, climate warming, and rising CO2 affect grassland water uptake, and whether adaptations of fine roots affect the capacity to extract water from soil. Using a multifactor global-change experiment in a managed montane C3 grassland, we studied the individual and combined effects of drought, warming (+3 ℃), and elevated CO2 (eCO2; +300 ppm) on root water uptake (RWU) over three growing seasons. RWU was assessed across different layers of the main rooting horizon using diel soil moisture dynamics during non-rain periods. We also investigated treatment effects on fine roots (production, traits), fine-root-to-shoot ratios, and consequences for RWU capacity. By increasing vapour pressure deficit (VPD) and its effect on RWU rates normalized to soil water content (RWUSWC), warming reduced RWU during hot periods. Under sustained warming, grassland decreased specific root length, and increased root diameters and fine-root-to-shoot ratios. Conversely, eCO2 slowed RWUSWC at high VPD, though fine-root adaptations were negligible. Compared to warming alone, future conditions (warming, eCO2) increased RWUSWC to a lesser extent and induced no fine-root adaptations, but reduced RWU to a similar degree. Drought reduced RWU (-66–75%) and increased water sourcing from deeper soil layers; however, a hot season amplified any RWU reductions under future conditions by 20%. Altogether, our study demonstrates that (i) RWU in C3 grasslands declines in a warmer, drier future, though (ii) eCO2 will mitigate the need for fine-root adaptations, maintaining RWU capacity. However, (iii) rising temperatures will exacerbate RWU reductions under drought. Therefore, hot droughts should have significant repercussions for water dynamics in C3 grasslands.

How to cite: Tissink, M., Radolinski, J., Reinthaler, D., Venier, S., Pötsch, E. M., Schaumberger, A., and Bahn, M.: Individual versus combined effects of drought, warming and eCO2 on grassland water uptake and fine roots, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3773, https://doi.org/10.5194/egusphere-egu24-3773, 2024.

16:40–16:50
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EGU24-11972
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On-site presentation
Andrea Carminati, Fabian Wankmüller, Louis Delval, Martin J Baur, Mathieu Javaux, Sebastian Wolf, Peter Lehmann, and Dani Or

The upscaling of hydrologic processes at catchment scale from small scale soil hydraulic parameterization has been met with limited success. For example, spatially variable attributes (topography, surface properties, preferential flow paths) affect infiltration and runoff rates, introducing uncertainties that mask the role of soil properties at catchment scales. In contrast, evidence suggests that evapotranspiration (ET) remains controlled by small scale processes (flow of water to roots, capillary pumping to drying surface) that are critically dependent on soil hydraulic properties. This scale invariance of ET offers opportunities for upscaling emergent ecosystem scale ET dynamics from basic soil information.

ET switches from being energy to water limited at a critical soil water threshold when the water flow through the soil matrix can no longer sustain the atmospheric water demand. This transition depends on the soil water characteristics and soil hydraulic conductivity curve (characterized by their nonlinearity and dependence on soil texture), on plant traits (root length density, leaf area, and xylem vulnerability), and on atmospheric conditions (e.g., vapor pressure deficit and wind velocity). Despite the importance of plant hydraulic traits and atmospheric conditions, the large variations in soil hydraulic properties as a function of soil texture, make small scale hydraulic properties the key in controlling ET during soil drying (Lehmann et al. 2008, Carminati and Javaux 2020). It follows that soil moisture thresholds of ET are controlled by water flow in soils and by the soil hydraulic conductivity. Accordingly, small-scale models of water flow to the soil surface and to the roots successfully predict soil moisture thresholds that have been measured at the ecosystem scale.

The question of why upscaling flow equations and properties derived from small sample and single plants to ecosystems proved to be successful is an important one. In contrast to water infiltration and run-off affected by the scale-dependent size of surface heterogeneities, the spatial scale of water flow from soils to roots does not increase with the scale of observation. It is the limiting flow through the soil matrix, with spatial scales of 0.01-0.1 m, which sets the point when plants downregulate transpiration and photosynthesis as the soil dries; a process that is similar to the evaporation from the soil surface.

In conclusion, despite the challenges and uncertainties in applying soil physical laws to larger scale, the application of Buckingham-Darcy law to properly predict matrix flow and evapotranspiration at the ecosystem scale is doable and relevant for understanding drought effects on ecosystem water use and productivity.

 

Carminati A, Javaux M. Soil rather than xylem vulnerability controls stomatal response to drought. Trends in Plant Science. 2020 Sep 1;25(9):868-80.

Lehmann P, Assouline S, Or D. Characteristic lengths affecting evaporative drying of porous media. Physical Review E. 2008 May 16;77(5):056309.

How to cite: Carminati, A., Wankmüller, F., Delval, L., Baur, M. J., Javaux, M., Wolf, S., Lehmann, P., and Or, D.: Ecosystem scale evapotranspiration is controlled by small scale processes and soil hydraulic properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11972, https://doi.org/10.5194/egusphere-egu24-11972, 2024.

16:50–17:00
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EGU24-16651
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Highlight
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On-site presentation
Laura Borma, Fabio Sakagushi, Wilian Demetrio, Breno Pupin, Dione Ventura, Carlos Daniel Meneghetti, Basile Devoie, Charlotte Dermauw, Lola Parmentier, and Mathieu Javaux

Given the critical role of tropical forests in providing ecosystem services, extensive global efforts have been made to conserve and restore these vital areas. Despite the recognized environmental value of preserved forests, substantial uncertainties persist regarding the impact of reforestation activities on water recharge. While some studies suggest that reforestation might lead to a reduction in surface and groundwater reserves, other research, backed by public opinion, indicates that forest recovery enhances water reserve.

Recognizing this as a crucial scientific and environmental management concern, our study aims to explore the role of de and reforestation on soil hydraulic properties. Combining in situ monitoring of water status and soil physical properties, our study aimed at addressing the following scientific question: how does soil structure evolve with different revegetation stages?

We selected several plots along a hillslope transect in the oceanic forest (Sao, Paulo, Brasil), with different reforestation stages (40 y.o. forest vs deforested pasture).  Deep percolation measurements were conducted using sealed bottom lysimeters. A comparative analysis of soil conditions in contrasted study areas involved soil physical properties such as texture, permeability, and bulk density, along with assessing the seasonal variability of matric potential and soil moisture content.

Our findings reveal that soil infiltration capacity of pasture was lower than under a 40 yr-old forest. We also observed that soil macroporosity  was higher under the forest area than  under the pasture area, potentially influencing infiltration rates and favoring deep drainage in the forest compared to the pasture.

How to cite: Borma, L., Sakagushi, F., Demetrio, W., Pupin, B., Ventura, D., Meneghetti, C. D., Devoie, B., Dermauw, C., Parmentier, L., and Javaux, M.: Tropical humid forests: water consumers or producers? The case of a forest fragment in the Atlantic Forest, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16651, https://doi.org/10.5194/egusphere-egu24-16651, 2024.

17:00–17:10
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EGU24-17711
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ECS
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Highlight
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On-site presentation
Sven Westermann, Jan Bumberger, Martin Schädler, Stephan Thober, and Anke Hildebrandt

Grasslands are highly dynamic ecosystems that adapt to environmental drivers such as climate, soil properties and anthropogenic management. However, the belowground response and adaptation of grassland communities to environmental drivers are poorly understood. Here, we investigate differences in the temporal dynamics of root water uptake, its depth pattern and the evolution of plant-available soil water storage between three different grassland management types and in two different climate treatments (control and future). The climate scenarios included treatments with and without a precipitation manipulation that partially shifts the precipitation from summer to spring and autumn. Soil moisture measurements were carried out at 6 depths up to 90 cm on three land use types (i) extensively and (ii) intensively managed grassland and (iii) extensive pasture at the Global Change Experimental Facility (GCEF) in Central Germany. Afterwards, root water uptake was estimated from diurnal variations in soil water content. We found that the grassland vegetation, in general, extracts water to depths of up to 90 cm during the growing season and can go even deeper. Extensively managed grasslands in the future climate scenario had increased root water uptake depths even in spring when water was not limiting indicating an adaptation to changing rainfall patterns. In contrast, more intensively managed grasslands could not compensate for greater water limitation with deeper root water uptake. Root water uptake depths during summer differed between the management types only in the future climate scenario, with drier conditions, along with the management intensity: The more intense, the shallower the uptake. This demonstrates that the ability to adapt to changing climate depends on management. Cumulative atmospheric water deficit was the main driver of root water uptake depth until the first mowing while ecosystem structure (vegetation height) and soil properties (plant available water at the beginning of the vegetation period) affect that relationship.

How to cite: Westermann, S., Bumberger, J., Schädler, M., Thober, S., and Hildebrandt, A.: How grasslands are managed will determine their ability to adapt to increased water scarcity under climate change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17711, https://doi.org/10.5194/egusphere-egu24-17711, 2024.

17:10–17:20
17:20–17:30
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EGU24-22231
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On-site presentation
Zeqing Ma, Gaigai Ding, Wenjing Zeng, Tao Yan, and Lijuan Sun

Plant nutrient foraging depends on roots and mycorrhizal fungi, which are affected by plant carbon (C) investment and soil nutrient availability. The C supply for root metabolism and associated fungi might be diminished as the host plant size increases, while the quality and quantity of soil nitrogen (N) change with forest succession. There is still no holistic understanding of how the organization of belowground mycorrhizal root structure and fungi in the nutrient acquisition continuum shifts with forest age and soil resources, which restrains our understanding of the functional relations among roots, fungi, and soil. Here we examined the shifts in the absorptive root and mycorrhizal strategies, and changes in soil-associated fungal community compositions along a temperate larch forest chronosequence nested with a long-term N fertilization gradient. We found that the effect of forest age outweighed soil N addition in our forest. As tree age increased, root respiration and specific root length decreased, but protective investments such as tissue density and phenolics decreased. Meanwhile, the proportion of ectomycorrhizal fungi with a short-distance exploration type increased, but those with a long-distance exploration type decreased. The shifts in root and mycorrhizal fungal traits demonstrate a nutrient acquisition continuum from "young explorative roots with long mycorrhizas" to "mature conservative roots with short mycorrhizas". A trade-off between the root architecture and root segment metabolism, and a complementarity between the size of the root system and mycorrhizal exploration types functionally constrains this nutrient acquisition continuum. Our results thus suggested forest succession drives the covariations among root system size, root metabolic rate, mycorrhizal fungal exploration type, and soil-associated fungal functional groups.

How to cite: Ma, Z., Ding, G., Zeng, W., Yan, T., and Sun, L.: Forest succession drives systematic change of root-mycorrhizal foraging strategies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-22231, https://doi.org/10.5194/egusphere-egu24-22231, 2024.

17:30–17:40
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EGU24-20215
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On-site presentation
Václav Šípek, Lukáš Vlček, Jan Hnilica, and Miroslav Tesař

Soil moisture plays a key role in the hydrological cycle by partitioning of precipitation between evapotranspiration and deep infiltration. The ongoing climate change is causing an increase in air temperatures, changes in precipitation patterns and decrease in winter snow cover. It simultaneously shifts spring snowmelt towards winter months. Both air temperature and precipitation patterns are suspected to be one of the influential factors affecting changes in soil hydraulic properties. Thus, the ongoing climate change can alter soil hydraulic properties, commonly considered time-invariant, and the prediction of future soil moisture regime can therefore be more uncertain than originally thought.

We measured a saturated hydraulic conductivity using an automatic single-ring infiltrometer thorough one entire year in a monthly time-step in the spruce covered site. Higher infiltration rates were regularly observed in the middle of a vegetation season compared to lower rates observed in a dormant season. Based on this finding we implemented a new function, enabling the seasonal variation of the saturated hydraulic conductivity, into the simple bucket-type soil moisture model. The root-mean square error of soil moisture prediction decreased by one-third and Nash-Sutcliffe efficiency increased significantly indicating possible benefits of a new concept. Main reasons behind the seasonal variability of soil hydraulic properties in uncultivated sites can be numerous (encompassing biological activity, changes in the root architecture, wetting/drying and freezing/thawing cycles altering the pore space) and deserve further investigation.

The major outcome is represented by the concept enabling a more efficient prediction of soil moisture regime outside the vegetation season, which is increasingly more important as the onset of soil drought can often be observed at the end of the dormant season. Furthermore, modelling of a climate change impact on the availability of water resources will also benefit from a better prediction of the soil moisture by considering regular structural changes of soil.

How to cite: Šípek, V., Vlček, L., Hnilica, J., and Tesař, M.: Modelling of soil water regime in forested areas: potential benefits of seasonally variable soil hydraulic properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20215, https://doi.org/10.5194/egusphere-egu24-20215, 2024.

17:40–17:50
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EGU24-11051
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ECS
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Virtual presentation
Daniel Fishburn, Andy Smith, Lars Markesteijn, and Ana Rey

Above-ground plant litter decomposition has a major influence on the global carbon (C) cycle by transferring 50% of net primary productivity to soil organic matter and releasing 60 Pg C annually into the atmosphere. Despite extensive research devoted to disentangling the main drivers controlling litter decomposition, the role of lithology remains understudied. Here, two studies were conducted to investigate the combined effects of lithology and climate on needle litter decomposition on three distinctive lithological substrates (calcareous, peridotite, and metapelite) along a precipitation gradient (ranging from 641 to 1097 mm yr-1) in the province of Málaga, south of Spain.

Study one examined needle litter decomposition of Pinus pinaster (maritime pine) along the experimental gradient, and study two was a reciprocal transplant experiment established on calcareous and peridotite lithological substrates located in the centre of the precipitation gradient with litter of contrasting chemical recalcitrance obtained from P. pinaster and Abies pinsapo (Spanish fir) to assess the impact of lithology on the home field advantage hypothesis.

Total litter mass loss during decomposition was highest in the calcareous substrate, exceeding metapelite and peridotite substrates by 24% and 50%, respectively. Decreased precipitation reduced litter mass loss only in calcareous soils (35%) but had little effect on metapelitic and peridotite sites indicating that more productive bedrock types are influenced to a greater degree by reducing precipitation, supporting the boom-bust hypothesis. On peridotite substrates, decomposition of the labile soluble cell fraction and cellulose-based crude fibre fractions of intermediate recalcitrance was delayed by one dry season whereas lignin decomposition ensued immediately highlighting physicochemistry-induced modification of substrate accessibility.  Moreover, study two demonstrated a pronounced home-field advantage for litter on calcareous substrates, contrasting with an away-field advantage for litter derived from peridotite substrates. These results underscore the significant role of lithology in dictating litter decomposition dynamics, directly influencing both litter quality and microbial substrate accessibility.

Given that lithology directly impacts litter quality and its response to changing precipitation patterns—both critical variables in global ecosystem carbon models—incorporating lithological factors is essential for accurately predicting how plant litter decomposition will respond to climate change.

How to cite: Fishburn, D., Smith, A., Markesteijn, L., and Rey, A.: The effect of lithology on leaf litter decomposition of Pinus pinaster forests along a Mediterranean precipitation gradient, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11051, https://doi.org/10.5194/egusphere-egu24-11051, 2024.

17:50–18:00

Orals: Wed, 17 Apr | Room 3.16/17

Chairpersons: Camilla Ruø Rasmussen, Sabine J. Seidel
16:15–16:20
16:20–16:40
|
EGU24-21812
|
solicited
|
On-site presentation
|
Marius Heinen, Martin Mulder, Jos van Dam, Ruud Bartholomeus, Quirijn de Jong van Lier, Janine de Wit, Allard de Wit, and Mirjam Hack-ten Broeke

Modelling soil-water-atmosphere-plant interactions and the modelling of processes in the unsaturated zone is performed in research and engineering projects worldwide, often extended to practical applications by stakeholders. The hydrological model SWAP stands out as a frequently used tool in this context. We consider the SWAP model and its predecessors like SWATR and SWACROP to have been initiated half a century ago, in 1974, in an article by Feddes, Bresler and Neuman in Water Resources Research entitled ‘Field test of a modified numerical model for water uptake by root systems’.

 

Over the years, the evolution to the present version of SWAP went through a great number of alterations, additions and improvements. In this contribution we will provide an overview on these developments, especially those from most recent years. This will include, amongst others, root growth dynamics, root water uptake and links to crop growth modelling. We aim on further improvements given new challenges like those resulting from climate change, extreme weather events, aspects of environmental sustainability, model parameterization, and model structure.

 

How to cite: Heinen, M., Mulder, M., van Dam, J., Bartholomeus, R., de Jong van Lier, Q., de Wit, J., de Wit, A., and Hack-ten Broeke, M.: SWAP 50 year: Advances in modelling soil-water-atmosphere-plant interactions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21812, https://doi.org/10.5194/egusphere-egu24-21812, 2024.

16:40–16:50
|
EGU24-7315
|
On-site presentation
Daniel Leitner, Andrea Schnepf, and Jan Vanderborght

Root water uptake strongly affects soil water balance and plant development. It can be described by mechanistic models of soil-root hydraulics based on soil water content, soil and root hydraulic properties, and the dynamic development of the root architecture. Recently, novel upscaling methods have emerged (Vanderborght et al. 2023, 2021), which enable the application of detailed mechanistic models on a larger scale, particularly for land surface and crop models, by using mathematical upscaling.

In this study, we explore the underlying assumptions and the mathematical fundamentals of the upscaling approach. Our analysis rigorously investigates the errors introduced in each step during the transition from fine-scale mechanistic models, which considers the nonlinear perirhizal resistance around each root, to more macroscopic representations. Upscaling steps simplify the representation of the root architecture, the perirhizal geometry, and the soil spatial dimension and thus introduces errors compared to the full complex 3D simulations. In order to investigate the extent of these errors, we perform simulation case studies: spring barley as a representative non-row crop and maize as a representative row crop, and using three different soils.

We show that the accuracy of the upscaled modeling approach strongly differs, depending on  root architecture and soil type. Furthermore, we identify the individual steps and assumptions that lead to the most important losses in accuracy. An analysis of the trade off between model complexity and accuracy provides valuable guidance for selecting the most suitable approach for specific applications.

 

References 

Vanderborght, J., Couvreur, V., Meunier, F., Schnepf, A., Vereecken, H., Bouda, M., and Javaux, M. (2021). From hydraulic root architecture models to macroscopic representations of root hydraulics in soil water flow and land surface models. Hydrology and Earth System Sciences, 25(9):4835–4860.

Vanderborght, J., Leitner, D., Schnepf, A., Couvreur, V., Vereecken, H., and Javaux, M. (2023). Combining root and soil hydraulics in macroscopic representations of root water uptake. Vadose Zone Journal, e20273.

How to cite: Leitner, D., Schnepf, A., and Vanderborght, J.: From hydraulic root architecture models to efficient macroscopic sink terms , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7315, https://doi.org/10.5194/egusphere-egu24-7315, 2024.

16:50–17:00
|
EGU24-17850
|
ECS
|
On-site presentation
Mona Giraud, Ahmet Sircan, Guillaume Lobet, Thilo Streck, Daniel Leitner, Holger Pagel, and Andrea Schnepf

To assess the impact of agricultural practices on water and carbon cycles within specific Genome-Environment-Management combinations, understanding the interactions across the Soil-Plant-Atmosphere continuum (SPAC) is crucial.

Indeed, soil water conditions influence carbon concentration and transport, impacting soil carbon physical and biochemical reactions.

The soil water and carbon status affect, in turn, the plant water and carbon dynamics directly via the plant-to-soil water or carbon gradient, and indirectly via plant water status, influencing its inner balance of water (uptake, transpiration and flow) and carbon (assimilation, usage for maintenance and growth, storage, respiration, rhizodeposition, and transport).

Reciprocally, plant water and carbon balances affect the soil carbon cycle in the short term through root water uptake and rhizodeposition. Those rhizodeposits are, for the most part, made of exudates and mucilage. Root exudates are low molecular weight organic compounds that are mainly passively diffused, while mucilage is a fluid made of polymers with high molecular weight created from starch via an active process.

Modelling plant and soil water and carbon processes, along with their interactions, can help to understand better and represent the effects of the underlying feedback loops. In this study, we therefore coupled the Functional Structural Plant Model (FSPM) CPlantBox with the rhizosphere model TraiRhizo, implemented using the porous medium flow and transport solver DuMux.

The overall coupled model and multiscale framework includes a module of 3D plant architecture development, and modules to represent flow and transport within the plant, the soil and the perirhizal zone around each root segment. Flows between compartments are solved implicitly via fixed-point iteration, using parallel computation for both the 3D soil and rhizosphere models.

We present a case study in which we simulated the growth of a C3 monocot and observed how changes in soil water content, due to root water uptake, influenced dissolved carbon concentration and (de)activation of the soil microbial communities during a dry spell.

In the future, the model will be applied to assess the impact of small dry spells at various stages of plant development against a baseline scenario. In time, this model could support plant breeding efforts to find root traits that aim for more drought-resistant plants in specific pedoclimatic environments.

How to cite: Giraud, M., Sircan, A., Lobet, G., Streck, T., Leitner, D., Pagel, H., and Schnepf, A.: Coupling a Functional-Structural Plant Model with a Rhizosphere Model To Gain Multiscale Insights into Plant-Soil-Atmosphere Interactions for Water and Carbon Cycles, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17850, https://doi.org/10.5194/egusphere-egu24-17850, 2024.

17:00–17:10
|
EGU24-15520
|
On-site presentation
Ruud van der Ent, Fransje van Oorschot, Andrea Alessandri, and Markus Hrachowitz

Vegetation plays a crucial role in regulating the water cycle through transpiration, which is the water flux from the subsurface to the atmosphere via vegetation roots. The amount and timing of transpiration is controlled by the interplay of seasonal energy and water supply. The latter strongly depends on the size of the root zone storage capacity (Sr) which represents the maximum accessible volume of water that vegetation can use for transpiration. Sr is primarily influenced by hydro-climatic conditions as vegetation optimizes its root system in a way it can guarantee water uptake and overcome dry periods. Sr estimates are commonly derived from root zone water deficits that result from the phase shift between the seasonal signals of root zone water inflow (i.e., precipitation) and outflow (i.e., evaporation). In irrigated croplands, irrigation water serves as an additional input into the root zone. However, this aspect has been ignored in many studies, and the extent to which irrigation influences Sr estimates was never comprehensively quantified. In this study, our objective is to quantify the influence of irrigation on Sr and identify the regional differences therein. To this aim, we integrated two irrigation methods, based on irrigation water use and irrigated area fractions, respectively, into the Sr estimation. We evaluated the effects in comparison to Sr estimates that do not consider irrigation for a sample of 4511 catchments globally with varying degrees of irrigation activities. Our results show that Sr consistently decreased when considering irrigation with a larger effect in catchments with a larger irrigated area. For catchments with an irrigated area fraction exceeding 10%, the median decrease of Sr was 17 mm and 22 mm for the two methods, corresponding to 12% and 17%, respectively. Sr decreased the most for catchments in tropical climates. However, the relative decrease was the largest in catchments in temperate climates. Our results demonstrate, for the first time, that irrigation has a considerable influence on Sr estimates over irrigated croplands. This effect is as strong as the effects of snow melt that were previously documented in catchments that have a considerable amount of precipitation falling as snow.

A manuscript associated with this abstract is available as preprint:

van Oorschot, F., van der Ent, R. J., Alessandri, A., and Hrachowitz, M.: Influence of irrigation on root zone storage capacity estimation, EGUsphere [preprint], https://doi.org/10.5194/egusphere-2023-2622, 2023.

How to cite: van der Ent, R., van Oorschot, F., Alessandri, A., and Hrachowitz, M.: The influence of irrigation on root zone storage capacity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15520, https://doi.org/10.5194/egusphere-egu24-15520, 2024.

17:10–17:20
17:20–17:30
|
EGU24-15318
|
ECS
|
On-site presentation
Louis Delval and Mathieu Javaux

Climate change will exacerbate drought events in many regions, increasing the demand on freshwater resources and creating major challenges for viticulture. The knowledge on grapevine drought stress physiology has increased significantly in recent years, but a holistic comprehension on how soil-grapevine hydraulic conductances develop and are regulated in the soil-grapevine-atmosphere continuum (SPAC) remains poorly understood. In particular, how soil type affects the grapevine hydraulic response to drought is still an open question.

The aim of this work is to understand how the hydraulic conductances in the SPAC continuously evolve according to soil type, during drought.

The continuous, concomitant and automatic monitoring of soil and collar water potentials, as well as sap flow, made it possible to characterize the evolution of the soil-grapevine hydraulics in situ in real-time. To investigate the impact of the soil type, two vineyards planted with Vitis vinifera cv. Chardonnay were selected due to their intra-field heterogeneity of soil properties (two subplots per vineyard). In a first vineyard, soil-grapevine hydraulics were measured on a sandy subplot and on a loamy subplot. In a second vineyard, we worked on a loamy subplot and on a silty-clay subplot.

We found that grapevine hydraulic response to soil drying is soil texture specific. Stomatal closure was observed for grapevines planted on coarse-textured soils, but not, or little, on fine-textured soils. This stomatal response was triggered by a decrease in belowground hydraulic conductance and not xylem cavitation in the trunk. This suggests that the interaction between the grapevine and the soil hydraulic environment plays a crucial role in shaping hydraulic behaviour of Chardonnay during drought periods.

While soil dries out, the decline in soil hydraulic conductivity led to a steep and nonlinear reduction in soil matric potential at the soil-root interface, with greater reduction in sandy soils compared to loamy soils. This rapid decline in soil hydraulic conductivity implies that the soil is more rapidly limiting (at less negative soil water potential), triggering earlier stomatal closure in coarse-textured soils. Stomatal regulation is amplified in sandy profile as compared to fine textured profile within the same grape variety.

How to cite: Delval, L. and Javaux, M.: In situ grapevine hydraulic response to drought is soil-texture specific, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15318, https://doi.org/10.5194/egusphere-egu24-15318, 2024.

17:30–17:40
|
EGU24-14434
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ECS
|
On-site presentation
Jianqiang Huo and Zhishan Zhang

Desertification is one of the most important environmental problems in the world. In arid and semi-arid regions, desert shrub reconstruction is one of the most effective ways to prevent desertification and promote ecological restoration. Recently, many studies have reported the hydraulic trade-off, coordination, and hydraulic segmentation of woody plants, however, the mechanism of how the hydraulic segmentation drives morphological adjustment of desert shrub to response to drought is still largely unclear. Here, the two-year-old seedlings of Caragana korshinskii and Artemisia ordosica as materials were subjected to continuous drought treatment. The aim is to explore hydraulic strategies and quantify the hydraulic threshold when morphological adjustments drive occurs. The results showed that tissues water content of C. korshinskii and A. ordosica under persistent drought showed an exponential decrease with the decrease of soil water content, but it is with a certain lag effect. Meanwhile, the leaf water potential, xylem specific hydraulic conductivity, degree of natural embolism and photosynthetic rate, etc. showed decrease trend with persistent drought. Above results suggested that hydraulic functional traits were drove by changes of soil water, but the tissue hydraulic capacitance acts as a buffer against decline of above traits. Moreover, the water potential thresholds of 88% stomatal closure and hydraulic safety margin in C. korshinskii was significant high than A. ordosica’s, which indicated that C. korshinskii are more vulnerable to drought. Then, the morphological adjustments such as leaf wilting and lateral branches wilting further occurred with the continued drought, however, the lateral branches of C.korshinskii could germinate again after soil water recovery, but A.ordosica could not. Overall, the water potential and hydraulic conductivity threshold for morphological adjustment of desert shrub such as leaves wilting and lateral branches wilting under continuous drought were quantified and the hydraulic strategies were elucidated that was regulated by hydraulic segmentation.

How to cite: Huo, J. and Zhang, Z.: Hydraulic strategies of desert shrubs responding to morphological adjustment under persistent drought, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14434, https://doi.org/10.5194/egusphere-egu24-14434, 2024.

17:40–18:00

Posters on site: Wed, 17 Apr, 10:45–12:30 | Hall A

Display time: Wed, 17 Apr 08:30–Wed, 17 Apr 12:30
Chairpersons: Sabine J. Seidel, Martin Bouda
A.72
|
EGU24-535
Shahar Baram and Hadas Levmore

In the published literature, irrigation with hyperoxic (dissolved oxygen > 15 mg/L) nanobubbles aerated water (NB-water) has a significant impact on bio-geo-chemical processes in soils. Yet, simple mass balances show that the amount of oxygen added to soils with such waters provides less than 1% of the oxygen respired. Further, such practices only slightly increase (0.1-0.5%) the oxygen concentration in the soil air. These minor contribution to the soil’s oxygen pool raises questions about the mechanisms that drive the impact on the bio-geo-chemical processes in it. Specifically on the soil’s microbial population and activity, greenhouse gasses emissions, and plant growth.  Soil respiration and nutrient uptake require a continuous supply of oxygen (O2) to the rhizosphere. However, in reality, in most soil, the rate of O2 diffusion into the soil is lower than the rate of its consumption. Hence, O2 concentrations in the rhizosphere are lower than in ambient air (20-21%; normoxia), and often sub-optimal or anoxic conditions develop. To date, the definition of sub-optimal O2 concentrations is not clear, and the general perception is that in most soils, O2 is not a crop-limiting factor. However, in recent years, more and more studies have shown that even small changes in the O2 concentration of the soil air (i.e., >0.2%) positively impact plant growth, metabolism, and yield. Results from studies with various soil aeration methods, such as the dissolution of micro- and nanobubbles and peroxides, show a positive response to O2 additions, even when the additions contributed a mere 0.01-1% of the soil respiration fluxes. The governing mechanisms for such positive responses are unclear, and further study is needed. 

How to cite: Baram, S. and Levmore, H.: Why does irrigation with hyperoxic water alter soil biochemistry?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-535, https://doi.org/10.5194/egusphere-egu24-535, 2024.

A.73
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EGU24-2130
|
ECS
Anne-Sophie Wachter, Alain Tissier, Esther Armah Harding, and Doris Vetterlein

Apple replant disease (ARD) refers to the observed decline in plant growth, fruit yield, and quality after repeated planting of apples at the same site. It is a phenomenon in all apple-producing areas worldwide which leads to an estimated profitability reduction of 50 % over the lifetime of an apple orchard. Up to now, the mechanisms behind ARD are only poorly understood. It has been attributed to the action of a site-specific, multi-kingdom, pathogenic, and parasitic biological complex. Thus, the soil faces (micro-) biome alterations due to previous apple cultures.

Upon initial contact, apple roots can detect and avoid soil affected by ARD. So far, it is not known how the roots can sense ARD in soil. Volatile organic compounds (VOCs) are promising candidates as communicators between soil and plant. It is known that VOCs mediate many cases of plant responses to pests or pathogens. Nevertheless, their role in ARD has so far been neglected.

A rhizobox experiment was set up to determine the volatile emission of apple plantlets growing in ARD and non-ARD soil. Volatiles are analyzed using untargeted gas chromatography-mass spectrometry with prior concentration on an adsorbents (here: stir bar sorptive extraction, SBSE) and thermodesorption.

This first pre-experiment run with the interpretation of the gas chromatogram as the next step. Our aim is to determine whether there are any differences between the volatiles detected in the close proximity of apple roots growing in ARD and in non-ARD soil. Noticeable VOCs will be identified to specify the occurring volatile profiles.

We will examine the potential role of VOCs as communicators between plants, the microbiome, and soil. It will be addressed whether the sensing of ARD is related to volatile production.

How to cite: Wachter, A.-S., Tissier, A., Harding, E. A., and Vetterlein, D.: The relationship between volatile organic compounds and apple replant disease, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2130, https://doi.org/10.5194/egusphere-egu24-2130, 2024.

A.74
|
EGU24-3544
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ECS
Jane Omenda, Milka Kiboi, Felix Ngetich, Gerd Dercon, Monicah Mucheru-Muna, Jayne Mugwe, Said Ahmed Hami, Fabian Kaburu, Samuel Nii Akai Nettey, Daniel Mugendi, Roel Merckx, and Jan Diels

Current knowledge on using 13C discrimination as an indirect measure of yield and water use efficiency (WUE) under different soil moisture conditions and soil fertility inputs in C4 crop species has considerable uncertainty. The objective of this study was to test for (i) the effect of selected soil water conservation measures and soil fertility inputs on sorghum yield, water use efficiency, and 13C discrimination, (ii) evaluate the relationship between various measures of water use efficiency and 13C discrimination, between sorghum yield and 13C discrimination; (iii) sorghum stem diameter and WUE and, the use of stem diameter and 13C discrimination as potential yield and WUE proxy. We implemented a field trial on-station for five seasons in the semi-arid areas of Upper Eastern Kenya. The experiment was designed in a randomized complete block design (RCBD) with three levels of nitrogen fertilization (120 kg ha−1, 60 kg ha−1, and 30 kg ha−1) application with four replications. The selected soil water conservation measures and soil fertility management were minimum tillage, mulching, tied ridging, and Managing Beneficial Interactions in Legume Intercrops (MBILI) along a control (no input). Water use efficiency was determined using carbon discrimination analysis and gravimetric technique. The leaves and post-harvest grain samples were analyzed for %N, %C, and δ13C on an Isotope Ratio Mass Spectrometer (IRMS). A clear and significant (p≤ 0.05) treatment effect was observed on the 13C isotopic discrimination and sorghum yield and growth attributes over the five seasons. The highest (4.85 Mg ha-1) grain yield was observed with minimum tillage with crop residue treatment. The δ13C values ranged from -13.14to -11.86‰for the sorghum grain. Treatments under minimum tillage with residue and tied ridges and the MBILI intercrop had significantly (p≤ 0.05) higher sorghum grain yield, WUE, stem diameter, chlorophyll content, and high δ13C values. The 13C discrimination was significantly (p≤ 0.05) associated with yield, WUE, stem diameter, and leaf chlorophyll. In the treatment with high N rate, the equation relating 13C discrimination to yield was Yield (Mg ha-1) = 1.4822δ13C + 20.879; R² = 0.3518. A significant positive relationship (R2 = 0.31) was observed between grain N fertilizer use efficiency and grain δ13C in sorghum harvested from plots with high N rate treatments. There was also a correlation (R2 = 0.341; p=0.001) between WUE and sorghum stem diameter. Based on these results, we conclude that grain 13C discrimination values at maturity and stem diameter are a potential complementary criterion for assessing sorghum yield performance and WUE under different soil moisture and nutrient availability conditions. Therefore, it can be deduced that minimum tillage with crop residue with a high fertilizer application rate (120N/ha) improves sorghum grain yield, WUE, and higher grain δ13C values. The high grain δ13C values observed with minimum tillage with crop residue over the five seasons indicate that plants suffered less water stress under minimum tillage with crop residue treatment. Therefore, grain δ13C discrimination and stem diameter can be used as water use efficiency proxy with C4 crops like sorghum.

How to cite: Omenda, J., Kiboi, M., Ngetich, F., Dercon, G., Mucheru-Muna, M., Mugwe, J., Hami, S. A., Kaburu, F., Nettey, S. N. A., Mugendi, D., Merckx, R., and Diels, J.: Sorghum water use efficiency and yield variations discerned by 13C isotopic technique under managed agricultural practices in Upper Eastern Kenya, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3544, https://doi.org/10.5194/egusphere-egu24-3544, 2024.

A.75
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EGU24-5513
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Martin Mulder, Marius Heinen, and Mirjam Hack-ten Broeke

For quantitative land evaluation studies often simulation models are used to determine differences between soil types in terms of water availability (actual transpiration) or crop productivity. In the Netherlands we developed a land evaluation system specifically for water authorities, provinces and drinking water companies. The system allows answering questions on how water management influences crop development due to too dry or too wet conditions in the unsaturated zone. This system is based on the linked simulation model SWAP (Soil-Water-Atmosphere-Plant) and WOFOST (WOrld FOod STudies). The impact of changes in climate or hydrology can then be studied in terms of effects on crop growth and farm income.

Although SWAP and WOFOST are process based models, the rootzone development is simulated in a straightforward way: the development of the root extension is specified by the user in advance and the root length density distribution is assumed static in time. Roots play a key role in the interaction between soil water and crop growth and crop yield simulation. Although plant roots are highly adaptable, their adaptability is often neglected in simulation models that are used for predicting impacts on yield. For a more realistic approach we implemented a simple and innovative root growth model which will react on the hydrological conditions within the rootzone. This means that newly formed roots will be assigned to regions where there is no or the least stress, and less or no new roots to regions where water stress was experienced. As a result the drought and oxygen stress will be less dependent on the initial root distribution as specified by the user.

The model performance of the adaptive root growth model is compared with a rhizobox experiment where the root growth of maize was tracked while influencing soil moisture conditions at the same time (Maan et al., 2023). An example for a regional study will be provided to show the relevance of adaptive rootzone development for assessing land qualities in space and time.

How to cite: Mulder, M., Heinen, M., and Hack-ten Broeke, M.: Effect of adaptive rootzone development in quantitative land evaluation studies, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-5513, https://doi.org/10.5194/egusphere-egu24-5513, 2024.

A.76
|
EGU24-7397
Jan Vanderborght, Juan Baca Cabrera, Guillaume lobet, Daniel Leitner, Mathieu Javaux, Valentin Couvreur, and Andrea Schnepf

Root systems of trees are obviously much larger than those of herbaceous plants. Considering a root length of 30 km of roots below a surface area of 1m2 in a forest and considering that the root system of a single tree extends over a horizontal area of 10 m², this would mean that a root system of one tree is 300 km long. To simulate the water flow in the root system, the root system is typically discretized in 1cm long root segments and a set of flow equations is setup and solved to derive the water potential and flux in each segment of the 3D root hydraulic architecture. For a system with n root segments and n+1 nodes at which segments are connected, this results in a set of n equations that need to be solved. Solving this set of equations corresponds with inverting an n by n matrix. For the root system of a tree, the size of this matrix would be 3 107 by 3 107. The linear equation matrix is sparse and could be solved using equation solvers that do not calculate the inverse matrix. But, also these solutions might still be too expensive so that an upscaled and reduced set of equations is needed. We developed an approach to upscale flow equations in root hydraulic architectures (Vanderborght et al., 2021), which were subsequently coupled to non-linear flow equations that account for resistance to flow in the soil around root segments (Vanderborght et al. 2023). But, these upscaling approaches require an inversion of the linear equation matrix. In order to address this problem, we developed an inversion method that uses the hierarchical structure of the root network to divide the inversion into a set of smaller inversion problems that can be solved in parallel. In this presentation, we outline the principle of the inversion method and demonstrate it for large root systems of trees.

 

References

Vanderborght, J., et al. (2021) From hydraulic root architecture models to macroscopic representations of root hydraulics in soil water flow and land surface models. Hydrol. Earth Syst. Sci., 25(9), 4835-4860. https://doi.org/10.5194/hess-25-4835-2021

 Vanderborght, J., et al. (2023). Combining root and soil hydraulics in macroscopic representations of root water uptake. Vadose Zone Journal, n/a(n/a), e20273. https://doi.org/https://doi.org/10.1002/vzj2.20273

How to cite: Vanderborght, J., Baca Cabrera, J., lobet, G., Leitner, D., Javaux, M., Couvreur, V., and Schnepf, A.: Upscaling of 3D root hydraulic architectures of trees to 1D root hydraulic models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7397, https://doi.org/10.5194/egusphere-egu24-7397, 2024.

A.77
|
EGU24-8276
Ágota Horel, Levente Czelnai, Tibor Zsigmond, Imre Zagyva, and Csilla Farkas

The objectives of the study was to 1) investigate soil-plant-water interactions based on field measurements of plant reflectance and soil water content (SWC) in different inter-row managed vineyards, and 2) modeling changes in the SWC due to differences in soil physical parameters among slope positions and management methods. The study explored the impact of three different soil management practices on grapevine growth and soil health in vineyards: tilled (T), cover crops (CC), and perennial grass (NT) inter-rows. Data was collected for 2022 and 2023. At each study slopes, we had two measurement points along a slope section. To continuously monitor soil water and temperature conditions, sensors were strategically positioned at two depths of 15 cm and 40 cm below the soil surface along the slopes, both at the upper and lower points of the vineyard, while topsoil SWC was measured bi-weekly. Normalized Difference Vegetation Index (NDVI) and Photochemical Reflectance Index (PRI) sensors were used to measure leaf reflectance, while handheld instruments were used to measure additional NDVI and leaf Chlorophyll contents (SPAD). For the hydrological modeling we used SWAP (Soil-Water-Atmosphere-Plant), where the rswap R-package was used for calibration (2020 15 and 40cm data), validation (2021 15 and 40cm data), and statistical evaluation.

In 2022, all three slopes showed a significantly higher SWC content for the higher points compared to the lower, while in 2023 the grassed slope upper point showed higher SWC (0.18 vs 0.15%). The highest NDVI values were measured for the cover cropped vineyard site (0.68). However, we found no significant differences among NDVI values based on inter-row management or slope position, only the grassed inter-row vineyard had differences in the NDVI values at the lower and upper points (p=0.034). The highest leaf chlorophyll contents were measured for the cover cropped vineyard site (305). Most of the leaf Chlorophyll values were not significantly different among slope positions. Using the SWAP model, data from the cover cropped inter-row vineyard was used for calibration and validation. We found good model fitting (NSE > 0.52; d_daily > 0.81). Reduced-tillage (RT) and drought tolerant plant (DTP) management scenarios were run to simulate SWC changes over time. Preliminary data shows that DTP significantly reduced, while RT did not significantly affect our site’s SWC.

Acknowledgments: This material is based upon work supported by the Hungarian National Research Fund (OTKA/NKFI) project OTKA FK-131792. The research presented in the article was carried out within the framework of the Széchenyi Plan Plus program with the support of the RRF 2.3.1 21 2022 00008 project.

How to cite: Horel, Á., Czelnai, L., Zsigmond, T., Zagyva, I., and Farkas, C.: Inter-row soil management affecting the soil-plant-water system in vineyard , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8276, https://doi.org/10.5194/egusphere-egu24-8276, 2024.

A.78
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EGU24-9160
|
ECS
Hanna Sjulgård, Lukas Graf, Tino Colombi, Juliane Hirte, Thomas Keller, and Helge Aasen

Drought can severely limit plant growth, and in turn crop productivity, and poses challenges to global food production. Plant growth can be measured with the Green Leaf Area Index (GLAI), and satellite images offer opportunities to estimate GLAI at field and landscape scales. Analysing satellite-estimated GLAI development at the landscape level could reveal new insights into how soil characteristics influence crop performance under various weather conditions, which in turn could provide information on how to mitigate the impacts of extreme weather. In this study, we quantified winter wheat growing patterns in two years with contrasting weather conditions (2018: early summer drought; 2021: normal growing conditions) on farmers’ fields using Sentinel-2 derived GLAI, and assessed the impacts of drought on GLAI dynamics. Moreover, we tested whether soil properties can explain differences in GLAI dynamics between a dry and a normal weather year.

Sentinel-2 scenes were downloaded from Microsoft Planetary Computer and the radiative transfer model PROSAIL was used to estimate GLAI throughout the winter wheat vegetative growing season on farmers’ fields in the south of Sweden. Characteristic GLAI parameters such as growth rate, area under the curve, peak GLAI and timing of the peak were calculated from the GLAI time series. The impact of drought on winter wheat growth was assessed by comparing the GLAI parameters between the dry year 2018 with the normal weather year 2021. In addition, the GLAI parameters were related to several biological, chemical and physical soil properties measured on the farmers’ fields.

The results showed lower GLAI parameters during the dry year compared to the normal weather year on the farmer’s fields. For some fields, there was a large difference between the years while for other fields a smaller difference. Plant available water content was found as the most important soil property in explaining the differences in GLAI parameters between the years. Our study demonstrates that satellite image analysis of GLAI dynamics can be used to identify plant stress responses on farmer’s fields. By analysing a dry and a normal year, we show that the impacts of drought can vary considerably between fields, and by combining GLAI estimates with measurements of soil properties, we identified plant available water content as a key soil property to explain differences between years. Thus, our results contribute to knowledge towards developing soil management strategies to mitigate the impacts of extreme weather.

How to cite: Sjulgård, H., Graf, L., Colombi, T., Hirte, J., Keller, T., and Aasen, H.: Impact of drought on Sentinel-2 derived winter wheat growth dynamics and the relation to soil properties, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9160, https://doi.org/10.5194/egusphere-egu24-9160, 2024.

A.79
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EGU24-19179
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ECS
Imen Mhimdi, Dagmar van Dusschoten, and Mathieu Javaux

Effect of soil texture on root water uptake 

I.Mhimdi, D.van Dusschoten, M.Javaux

Forschungszentrum Jülich, Institute for Plant Sciences (IBG-2 ),  Jülich, Germany

Catholic University of Louvain, Earth and Life Institute, Louvain La Neuve, Belgium

Understanding how root water uptake (RWU) depends on soil properties is a key to estimate plant transpiration dynamics and its response to climate. Despite the fact that soil texture plays an important role in determining plant water availability and mechanical resistance, texture and RWU have not often been considered simultaneously in literature. Recently, a novel method was developed by (van Dusschoten et al, 2020), the SWaP (Soil Water Profiler), in which soil water content and its depletion could be monitored during a modulated light regime in order to derive the RWU profile. The scope of our work is to investigate with the SWaP how soil texture impacts RWU dynamics. We hypothesize that the soil texture will impact the distribution of the rhizosphere resistance in the rhizosphere and thereby its RWU.

Eight faba bean (Vicia Faba) plants were grown in 45cm PVC pots, two soil textures (Loamy and Sandy) with different dry density were used. The plants were subjected to progressive water deficits, and were measured continuously with the SWaP, while applying light modulations during daytime to measure instantaneous 1D water content and derived root water uptake profiles. In combination with the SWaP, several MRI measurements were performed combined with image analysis, in order to determine the local root length distribution and its relation to RWU.

For loamy soil, MRI measurements showed a structured spiral shape, an extensive and deeper root system with higher root diameter. Roots were less smooth, tortuous and with denser lateral roots in sandy soil. In both textures, root water uptake decreased with depth, which can be explained by the less abundant roots in lower soil layers and a higher resistance for the deeper roots (Müllers et al, 2023). Root water uptake profiles and total water uptake dynamics were different, between soil types, which could partially be attributed to differences in root distribution.

References

van Dusschoten et al., 2020, Spatially resolved root water uptake determination using a precise soil water sensor, Plant Phys.

Müllers et al., 2023, Deep-water uptake under drought improved due to locally increased root conductivity in maize, but not in faba bean, Plant, Cell & Environment.

How to cite: Mhimdi, I., van Dusschoten, D., and Javaux, M.: Effect of soil texture on root water uptake  , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19179, https://doi.org/10.5194/egusphere-egu24-19179, 2024.

A.80
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EGU24-9866
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ECS
Mohanned Abdalla, Andrea Carminati, and Mutez Ahmed

Stomatal regulation, which governs water loss and hence plant water use, is a key feature facilitating plant adaptation to water-limited environments. Nevertheless, the underlying mechanisms governing stomatal closure remain disputed. Recent studies proposed that the loss in hydraulic conductivities within the soil-plant system is the main driver of stomatal closure. However, the primary hydraulic constraint along the system, being in the soil and/or within the plant, remains without consensus. Furthermore, simultaneous measurements of the hydraulic limitation and stomatal regulation, especially in intact plants, is challenging. Here, we reviewed the recent literature on the relationship between stomatal closure and the loss of hydraulic conductance of key elements across the soil-plant-atmosphere continuum: soil, root, root-soil interface, xylem and leaf. We observed higher correlation between stomatal closure and declining below-ground hydraulics rather than leaf and/or xylem hydraulics. This analysis confirms the notion that stomatal closure is triggered by the decline of the soil-plant hydraulic conductance, and that this decline has often a below-ground origin. Understanding the key regulatory role of below-ground hydraulics is critical for forecasting and managing plant behavior under drought. 

How to cite: Abdalla, M., Carminati, A., and Ahmed, M.: The concomitance of water use regulations and loss in soil-plant hydraulic conductivities, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9866, https://doi.org/10.5194/egusphere-egu24-9866, 2024.

A.81
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EGU24-11140
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ECS
Emma Ossola, Tina Köhler, Andrea Carminati, and Walid Sadok

The rise of global temperatures and shifts in precipitation patterns lead to increasing vapour pressure deficit (VPD), which was shown to have a detrimental impact on yield of many crops. A reduction in the transpiration rate (TR) at high VPD has been proposed as a key drought tolerance breeding trait to avoid excessive water loss. Our hypothesis is that with climate change, it will be more convenient for plants to have traits that restricts TR under high VPD levels. With this research we aimed to identify relevant hydraulic traits impacting plant water use during atmospheric drying.

We measured water use and hydraulic traits of 15 different Minnesota spring wheat (Triticum aestivum L.) genotypes. We grew 45 plants (3 replicates for each genotype) in a climate chamber with controlled climatic conditions, while the soil was kept moist. After six weeks of growth, we monitored TR at 6 different VPD levels, between 0.5 and 2.8 kPa. Additionally, we measured maximum stomatal conductance (gs), leaf area (LA), plant hydraulic conductance (Kplant), stomatal density (SD), and root and leaf total biomass.

Our findings show that total transpiration per LA, LA, and root/shoot-ratio differed significantly between genotypes. Conversely, transpiration sensitivity to rising VPD (indicated by the critical VPD upon which plants restricted transpiration, VPDBP), Kplant and maximum gs did not significantly differ between genotypes. However, we observed that plants with a low Kplant and a high maximum gs expressed a relatively low VPDBP, indicating a higher transpiration sensitivity to VPD. Our results align well with a hydraulic explanation of the TR response to increasing VPD and suggest that plant hydraulics play a key role in regulating TR during atmospheric drying. If the goal of future breeding is to modify plant water use under increasing VPD, targeting hydraulic traits has still much underexplored potential.

How to cite: Ossola, E., Köhler, T., Carminati, A., and Sadok, W.: Genotypic variability of plant water use strategies during increasing atmospheric drought in 15 spring wheat (Triticum aestivum L.) genotypes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11140, https://doi.org/10.5194/egusphere-egu24-11140, 2024.

A.82
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EGU24-12431
Armando Molina, Veerle Vanacker, Oliver Chadwick, Santiago Zhiminaicela, Marife Corre, and Edzo Veldkamp

Plants play a key role in absorbing nutrients and water through their roots, and modulate the biogeochemical cycles of terrestrial ecosystems. Nutrient uptake mechanisms of water and nutrient by plants depend on climatic and edaphic conditions, as well as of their root systems. Soil solution is the medium in which abiotic and biotic processes exchange nutrients, and nutrient concentrations vary with the abundance of reactive minerals and fluid residence times. High-altitude grassland ecosystems of the tropical Andes are particularly interesting to study the relationship between vegetation communities, soil hydrology and mineral nutrient availability. In páramo ecosystems, forest, tussock grasses and cushion plants co-occur across the landscape. In the nutrient-depleted nonallophanic Andosols, the plant rooting depth varies with drainage and soil moisture conditions. Vegetation composition is a relevant indicator of rock-derived nutrient availability in soil solutions. Significant variations in the soil solute chemistry revealed patterns in plant available nutrients that were not mimicking the distribution of total rock-derived nutrients nor the exchangeable nutrient pool, but clearly resulted from strong biocycling of cations and removal of nutrients from the soil by plant uptake or deep leaching. Our findings highlight the importance of vegetation communities, soil hydrological condition, and the bioavailability of mineral nutrients to trigger rapid and complex changes in the biogeochemistry of soil waters. Moreover, the findings have important implications for future management of Andean ecosystems where vegetation type distributions are dynamically changing as a result of warming temperatures and anthropogenic disturbances. Such alterations may not only lead to changes in soil hydrology and solute geochemistry but also to complex changes in weathering rates and solute export downstream with effects on nutrient availability in Andean rivers and high-mountain lakes.

How to cite: Molina, A., Vanacker, V., Chadwick, O., Zhiminaicela, S., Corre, M., and Veldkamp, E.: Effect of soil-plant interactions on nutrient availability and supply in a tropical Andean ecosystem , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12431, https://doi.org/10.5194/egusphere-egu24-12431, 2024.

A.83
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EGU24-15054
|
ECS
Laura Raquel Quinonez Vera and Quirijn de Jong van Lier

A frequently used approach to estimate the reduction of the root water uptake (RWU) caused by oxygen stress in hydrological models such as SWAP is the empirical model of Feddes, which describes RWU using a piecewise linear function. Critical values associated with the threshold pressure heads defining oxygen stress (h1 = -10 cm and h= -25 cm) seem not to be able to represent properly this condition, because oxygen may start at more negative values of h. As an alternative, Bartholomeus et al. (2008) proposed a model based on physical and physiological soil and root processes to calculate the minimum gas-filled porosity of the soil at which oxygen stress occurs. We performed a sensitivity analysis of the Bartholomeus model focusing on two parameters, the threshold to stop root extension in case of oxygen stress and the air-filled root porosity in shallow water table scenarios cropped with soybean. We performed simulations for five soil types in combination with several water table depths. To do so, the water table was used in SWAP as the lower boundary condition. The sensitivity of the RWU and relative transpiration to combinations of parameters will be shown and discussed.

 

How to cite: Quinonez Vera, L. R. and de Jong van Lier, Q.: Sensitivity analysis of root water uptake reduction using the Bartholomeus model in shallow water table scenarios, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15054, https://doi.org/10.5194/egusphere-egu24-15054, 2024.

A.84
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EGU24-15448
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ECS
Thuy Nguyen, Gina Lopez, Sabine Seidel, Lena Lärm, Felix Bauer, Anja Klotzsche, Andrea Schnepf, Thomas Gaiser, Hubert Hüging, and Frank Ewert

Improved understanding of crops’ response to soil water stress is important to advance soil-plant system models and to support crop breeding, crop and varietal selection, and management decisions to minimize negative impacts. Studies on eco-physiological crop characteristics from leaf to canopy for different soil water conditions and crops are often carried out at controlled conditions. In-field measurements under realistic field conditions and data of plant water potential, its links with CO2 and H2O gas fluxes, and crop growth processes are rare. Here, we presented a comprehensive data set collected from leaf to canopy using sophisticated and comprehensive sensing techniques (leaf chlorophyll content, hourly leaf stomatal conductance and photosynthesis, canopy CO2 exchange, sap flow, and canopy temperature) including detailed crop growth characteristics based on destructive methods (seasonal dynamics of crop height, leaf area index, above-ground biomass, and yield). Data were acquired under field conditions with contrasting soil types, water treatments, and different cultivars of wheat and maize. The data from 2016 up to now will be made available together with the below-ground data. This dataset produced under field conditions is unique and could be used by different users (agronomists, hydrologists, crop modelers, breeders, etc.) for studying soil/water-plant relations and improving soil-plant-atmospheric continuum models.

How to cite: Nguyen, T., Lopez, G., Seidel, S., Lärm, L., Bauer, F., Klotzsche, A., Schnepf, A., Gaiser, T., Hüging, H., and Ewert, F.: Multi-year aboveground dataset of minirhizotron facilities on a cropland site with two soil types in Western Germany, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15448, https://doi.org/10.5194/egusphere-egu24-15448, 2024.

A.85
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EGU24-16031
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ECS
Dominik Behrend, Thuy Huu Nguyen, Hubert Hüging, Juan C. Baca Cabrera, Guillaume Lobet, Clara Oliva G. Bazzo, Sabine J. Seidel, and Thomas Gaiser

Partitioning of biomass between roots and the above ground organs of crops is a key plant physiological processes that is closely linked to root growth and, thus, water and nutrient uptake. This makes investigations and knowledge about the partitioning of carbon between below and above ground plant organs important for accurately simulating water and carbon fluxes from croplands. Previous experiments have shown that carbon partitioning between root and shoot of crops could be altered by drought. However, most crop models do not explicitly consider the alteration of carbon partitioning caused by drought. This might partly be due to the difficulties in measuring the complete root biomass under field conditions and, thus, a lack of data on the field scale. Current methodologies such as soil coring and shovelomics are time-consuming and limited with regards to the measured depth, they do not necessarily capture the whole root biomass of deep rooting winter crops like winter wheat.

The overall aim of the study is to improve our understanding of responses of below and above ground growth processes to different soil water availability. A field experiment has been conducted to investigate how drought stress affects the root: shoot ratio of different winter wheat cultivars under field conditions. A carbon partitioning subroutine, based on the sink strength principle and considering the direct effects of drought stress on carbon allocation, is implemented in the crop model SIMPLACE<LintulCC2>. The experimental data was used to test whether this newly developed model could successfully represent the effects of drought stress on biomass partitioning for different wheat cultivars.

In the experiment, tubes with a diameter of 11 cm and a length of 1 m, filled with a sandy substrate and closed on the bottom with a fine mesh fleece that allows water to flow through but stops roots from growing through, were buried in 1m deep holes. Winter wheat was sown inside the tubes and the field around them to catch the whole plant biomass under canopy conditions. Half of the tubes were watered during the growth period, the other half were sheltered from rain during early growth stages. Root biomass and traits were investigated after harvesting the tubes. The data from this experiment was used to calibrate the carbon partitioning subroutine in the crop model under non-stressed and water-stressed conditions. The carbon partitioning subroutine calculates organ-specific potential daily growth rates. These growth rates are used to calculate the organ-specific sink strength, which can be affected by water stress and is used to define the amount of carbon distributed to each organ per day.

The first experimental results show that water stress did affect the carbon partitioning between root and shoot biomass of winter wheat. The implemented model improved the simulation of biomass partitioning between root and above ground plant organs under drought conditions.

How to cite: Behrend, D., Nguyen, T. H., Hüging, H., Baca Cabrera, J. C., Lobet, G., G. Bazzo, C. O., Seidel, S. J., and Gaiser, T.: New methods of measuring and modeling biomass partitioning in winter wheat under field conditions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16031, https://doi.org/10.5194/egusphere-egu24-16031, 2024.

A.86
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EGU24-16680
|
ECS
|
Lucie Rapp-Henry, Jean-Martial Cohard, Mahamadi Tabsoba, Basile Hector, Jérôme Demarty, and Laura Condon

The Sahelian region experienced intense droughts between 1970 and 1990 and despite a precipitation « recovering », soils remain degraded and a decrease in the soil ability to infiltrate - an essential characteristic for vegetation recover – is observed, together with an increase of desertification and of eroding floods frequency.

To tackle with this phenomenon, coordinated agricultural strategies, like the Great Green Wall project, have been encouraged and spread over large areas through NGOs. This consists in applying agro-ecological practices, like micro dams, to harvest water, favor infiltration, and hence vegetation growth. These strategies still require critical assessments and optimisation. To study such agroecological practices we are developing a modelling framework based on ParFlow-CLM to simulate the interactions between surface hydrology and vegetation in the context of crusted Sahelian soils where water transfers are highly dependent on both surface hydrodynamical properties and root distribution below the surface. Indeed, the very thin eolian crust acts as a hydraulic discontinuity that slows down soil evaporation transfers but not transpiration, which benefits from the roots below the crust and from the stems which bridge to the atmosphere.

However, since the CLM family models were designed for large scale with a relatively thick mesh at the surface, the root density function proposed as a decreasing exponential function distribute the majority of roots just below the surface. This disposition is irrelevant for finer millimeter underground meshes modelling, particularly in areas with a hot and dry climate such as the Sahelian one, that dries very rapidly the first centimetres of soil.

Thus, In the CLM land surface model framework and according to literature, we propose a new root distribution in the soil, using a parameterised function which is zero at the surface and at infinity, and adapt the maximum root density depth and the root concentration around this maximum. We compare the impact of both initial and proposed root functions on a Sahelian case study in Niger where all necessary data are available thanks to the AMMA-CATCH observatory. Studying this function highlighted simple causal relations between root density function parameterisation and evapotranspiration flux.

By modifying the root density function, we can find a set of parameters corresponding to a better representation of transpiration, global evapotranspiration and soil moisture, and accordingly, a better representation of the studied ecosystem.

Once this representation is relevant, a dynamic LAI based on allocation laws, available in the latest version of CLM, will then complete this modification of the vegetation scheme. We will then introduce the changes on surface due to agricultural practices and study the impact of their sizing.

How to cite: Rapp-Henry, L., Cohard, J.-M., Tabsoba, M., Hector, B., Demarty, J., and Condon, L.: Eco-hydrology modelling in arid areas : Study of root density impact on water fluxes in the Sahelian region, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16680, https://doi.org/10.5194/egusphere-egu24-16680, 2024.

A.87
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EGU24-16788
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ECS
Valentin Michels, Maximilian Weigand, and Andreas Kemna

Despite their vital role for agricultural management practices and plant breeding experiments, it is still challenging to characterize plant roots non-invasively in their natural environment. A promising new method for plant root characterization is the spectral electrical impedance tomography (sEIT) method, which is able to image the conductive and polarizable subsurface properties with high spatio-temporal resolution. Electrical polarization signatures have been shown to be sensitive to root structure and activity, although superimposed soil signatures complicate the interpretation. Recent studies have demonstrated that impedance measurements can be used to estimate root traits under laboratory conditions, especially in hydroponic experiments. However, field studies using sEIT on plant-root systems are still scarce.

In this study we present a field dataset of multi-frequency sEIT measurements on sugar beet and maize. Three different growth stages were measured during a whole growing season. We performed complex resistivity inversions for each measurement frequency, and subsequently analyzed the spatially resolved spectral response using a Debye decomposition analysis. Characteristic relaxation times, extracted from the spectral analysis, serve as proxies indicating the length scales of the observed polarization processes. We find that the physiologically different plant root systems cause distinct polarization responses in the low-frequency range. While both root systems exhibit an increasing polarization response towards higher frequencies, sugar beet develops an additional low-frequency polarization peak near 10 Hz later in the season, corrseponding with increasing size of the sugar beets. We attribute this peak to the polarization of root structures associated with the macroscopic dimensions of the beet roots, and demonstrate this link through the correlation of the retrieved mean relaxation time at the sugar beet positions with the square of the respective maximum beet diameter. Additionally, we evaluate the intrinsic spectral form of the polarization signatures extracted from the maize root area, and find a moderate correlation with the fresh biomass.

In conclusion, our results highlight that sEIT can be used in the field for plant root trait estimations, but structurally differing plants require different analysis procedures to extract root information. Additionally, environmental factors, like a varying soil composition or soil water content, have a strong influence on the measured impedance signal, and can make precise root trait estimation difficult.

How to cite: Michels, V., Weigand, M., and Kemna, A.: Investigating electrical polarization signatures of sugar beet and maize: A field study using spectral electrical impedance tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16788, https://doi.org/10.5194/egusphere-egu24-16788, 2024.

Posters virtual: Wed, 17 Apr, 14:00–15:45 | vHall A

Display time: Wed, 17 Apr 08:30–Wed, 17 Apr 18:00
Chairpersons: Valentin Couvreur, Mohsen Zare, Martin Bouda
vA.21
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EGU24-12839
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ECS
Marina Luciana Abreu de Melo, Quirijn de Jong van Lier, Jos C. van Dam, and Marius Heinen

Drought stress is one of the main reasons for reduced yields in soybean and wheat crops in Brazil. Process-based root water uptake (RWU) models are valuable tools to assess soil-water-plant relations and improve crop water management. We aimed to perform a pioneer sensitivity analysis (SA) of a process-based RWU model using three methods and two sampling strategies. The SWAP agro-hydrological model with the recently implemented MFlux RWU function was used to predict drought stress in soybean and wheat crops simulated on five soils with different hydraulic properties sampled in southeast Brazil, characterized by a tropical winter-dry climate. Three SA methods were used: local, global Morris, and global Sobol. Seven parameters of the MFlux function were selected, together with their reference values and ranges of variability. The local sensitivities were predominately negative, indicating that the drought stress increased as the values for each RWU parameter decreased. The Morris method revealed parameter interactions not addressed in the local method. The Sobol method also evidenced parameter interactions calculated through robust variance-based indices. Although the three SA methods provided different results regarding parameter contributions to drought stress prediction, the root length density was the most sensitive parameter for all simulated scenarios. Hence, it should be a priority in future model calibration efforts.

How to cite: Abreu de Melo, M. L., de Jong van Lier, Q., C. van Dam, J., and Heinen, M.: Sensitivity analysis of a process-based root water uptake model to predict drought stress in soybean and wheat in a tropical winter-dry climate, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12839, https://doi.org/10.5194/egusphere-egu24-12839, 2024.

vA.22
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EGU24-13962
Effect of soil moisture hysteresis on root water uptake: 1D Model
(withdrawn)
Tathagata Sinha