Experimental techniques such as non-invasive imaging and three-dimensional root system modeling tools have deepened our understanding of water and solute transport processes in the soil-plant system. Quantitative approaches that integrate across disciplines and scales serve as stepping stones to advance our understanding of fundamental biophysical processes at the interface between soils and plants.
This session targets research investigating soil-plant-related resource transfer processes and contributions linking biological processes and soil physics across different scales (from the rhizosphere to the global scale) and welcomes scientists from multiple disciplines encompassing soil and plant sciences across natural, as well as agricultural systems. 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 belowground processes such as root growth, root water, and nutrient uptake, root exudation, microbial interactions, and soil structure formation.
- Mechanistic understanding of plant water use and gas exchange regulation under drought and their implementation in Earth system models.
The aim of this session is to highlight the potential of interdisciplinary approaches to address current and future challenges in soil and plant science and to foster scientific exchange across disciplines.
Plant roots draw soil water locally, increasing the moisture heterogeneity in the soil at the onset of drought. The resulting heterogeneity presents a major challenge for linking observed flux rates to measured soil moisture values using process-based models. As such, soil moisture heterogeneity is a key remaining hurdle to robust, mechanistic predictions of forest canopy fluxes under water limitation and a stubborn source of uncertainty in predictions of the future terrestrial carbon cycle.
Several recent theoretical advances in describing soil-root water flow at plant or larger scale despite heterogeneous moisture distributions (e.g., Hildebrandt et al., 2016; Vanderborght et al., 2021) share one potentially central feature: the conductance- or flux- weighting of water potential at the soil-root interface. Flux-weighted water potential may be a key concept capable of characterising the hydrodynamic state of the soil-plant system in a single value regardless of its instantaneous heterogeneity.
Given the apparent theoretical promise of this concept, we should ask whether we can infer its values from field observations and, if so, what and how to measure. The challenges of directly measuring plant water potential over time are already daunting aboveground. Maintaining a dense network of probes for soil water content and water potential at substantial cost and effort may not yield relevant values, since the potential drop toward the root is nonlinear and largest over the final millimetres of soil. One potentially promising avenue for field observations is afforded by recent advances in optical methods both above and below ground. Separately, key parameters arising from the process-based models will need to be constrained in lab-based experiments. Collaborators within the ongoing HydroScale project aim to develop a complex approach combining traditional and innovative techniques sufficient to infer flux-weighted potentials from field data.
How to cite: Bouda, M.: Can we observe flow-weighted water potential at the root-soil interface in heterogeneously moist soils?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12198, https://doi.org/10.5194/egusphere-egu26-12198, 2026.
The critical root-zone soil moisture (SM) threshold is a fundamental parameter that marks the transition from energy-limited to soil-moisture-limited evapotranspiration (ET) regimes, yet regional and global studies often rely on near-surface SM and its associated threshold as a proxy. This study presents a global, measurement-based evaluation of critical root-zone SM threshold by analyzing 666 dry-down events across 34 eddy covariance flux tower sites equipped with multi-layered SM sensors reaching depths of at least 1 meter. The results demonstrate that critical thresholds derived from near-surface and root-zone SM are significantly inconsistent, with an overall root mean square error (RMSE) of 0.11 m³ m⁻³. This discrepancy is primarily driven by the vertical SM gradient and the decoupling of near-surface and root-zone layers during drydown periods, which leads to substantial errors in identifying the onset and duration of plant water stress. For instance, at a forest site (US-Me2), using the critical threshold derived from near-surface SM delayed the detected onset of moisture stress by 27 days and underestimated the duration of the moisture-limited regime by 36 days. Across the diverse biomes and climate types studied, the global mean was 0.12 ± 0.11 m³ m⁻³. These findings provide a critical observational benchmark for the evaporative fraction-root zone soil moisture relationship, highlighting that transitioning from near-surface to root-zone-based assessments is essential for accurate land-surface model evaluation and the quantification of ecosystem vulnerability to drought.
How to cite: Chen, B., Fu, Z., Huang, Y., Wang, S., and Chen, Z.: Uncovering critical thresholds of root-zone soil moisture for plant water stress in terrestrial ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4133, https://doi.org/10.5194/egusphere-egu26-4133, 2026.
Land-atmosphere exchange shifts from energy-limited to water-limited regime at a critical soil moisture, which marks a fundamental transition in the Earth system. Estimates of the critical threshold vary a lot across studies despite its importance for the mechanistic understanding of soil moisture limitation on transpiration and plant productivity.
We introduce a novel, model-based diagnostic approach — the Normalized Transpiration Deficit (NTD) method — and demonstrate that it yields results highly consistent with observational methods such as finding breakpoints in the evaporative fraction. Using a hydraulically-enabled version of the CABLE-POP land surface model, we conducted a factorial experiment across various soil textures, climate regimes, and plant hydraulic parameters. It suggests that the critical threshold occurs at a broadly similar soil matric potential (ψcrit) across soil types, resulting in a quasi-linear relationship between the critical volumetric soil moisture (θcrit) and sand content, as observed in earlier studies. The dependency of θcrit on soil type vanished when it was normalised by field capacity, which yielded hence also a universal threshold of relative extractible water REWcrit, as found empirically for forest ecosystems.
Most of the variance of θcrit, 86%, came from soil texture in the factorial experiment, while the variances of ψcrit and REWcrit were largely explained by plant hydraulic traits, accounting for 87% and 77% of total variance, respectively. Within the plant hydraulic traits, the P50-values of stomatal conductance (ψ50,l) and of xylem conductance (ψ50,x) showed the strongest correlations with the critical thresholds, indicating that vulnerability to hydraulic dysfunction plays a key role in shaping plant responses to soil drying. There was, however, no direct effect of climate on any of the critical thresholds, i.e. the thresholds remained invariant across climates for given soil and vegetation types. This suggests that apparent climate dependencies reported in observational studies may be artifacts due to limited soil moisture ranges at each observational site, or they represent biological adaptation and acclimation that is currently not captured in our static model parameters.
These findings highlight the necessity of incorporating ecosystem-scale hydraulic regulation in biosphere models to reconcile divergent estimates of critical thresholds and to improve predictions of drought impacts on water and carbon fluxes.
How to cite: Lu, Z. and Cuntz, M.: The soil matric potential where ecosystems get water-limited is independent of soil type and climate, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5068, https://doi.org/10.5194/egusphere-egu26-5068, 2026.
Semi-arid coastal basins where fog sustains fragmented forest patches provide a powerful natural laboratory for examining how vegetation–microclimate feedbacks shape ecotone position and stability. Yet most studies of woodland–open vegetation transitions treat ecotones as passive boundaries imposed by climate or soil conditions, rather than as zones where plant water-use strategies may actively reinforce or relax those boundaries. Here, a coastal Chilean fog forest–shrub ecotone is used to evaluate whether tree water can biologically promote ecotone persistence.
We studied fog-fed relict forests of the endemic temperate tree species Aextoxicon punctatum found on mountain tips of the semiarid coast of central Chile. We quantified sap flux and microclimatic conditions along a transect spanning forest edge to interior, using long-term sap flow measurements from 13 trees of A. punctatum, the dominant tree species in these forest patches, combined with continuous records of temperature, humidity, and vapor pressure deficit (VPD). This design allowed us to assess how tree water use responds to contrasting microclimatic environments across the ecotone.
We found strong edge-to-interior gradients in microclimate, with forest edges experiencing higher temperatures, higher VPD, and greater microclimatic variability than the forest interior. Correspondingly, tree water use differed systematically with tree position along the edge-to-interior gradient. Edge trees exhibited distinct seasonal dynamics and greater sensitivity to atmospheric conditions compared to interior individuals, particularly during periods of higher water availability. Contrary to expectations for a strictly water-limited temperate system, tree water use peaked during cool, foggy autumn and winter months, and contrasts between edge and interior trees were strongest during periods of high water availability, when trees used water most liberally. These patterns indicate that trees occupying different positions within the ecotone persist under contrasting physiological constraints and capacities.
Together, these results support the idea that forest–shrub ecotones are not merely passive boundaries imposed by climate, but may be biologically reinforced by spatial variation in tree water-use strategies. We further suggest that tolerance to edge microclimates, potentially coupled with the ability to exploit non-rain water inputs, may contribute to the persistence and resilience of fog-inundated forest patches. This perspective highlights ecotones as dynamic zones where individual-level physiological performance shapes vegetation boundaries, with implications for predicting coastal dry–humid transitions under climate change.
How to cite: Gaxiola, A., García, V., Gutiérrez, Á., and Rocha, A.: Ecotones as biological outcomes: spatial variation in tree water use across a boundary of a fog forest., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14212, https://doi.org/10.5194/egusphere-egu26-14212, 2026.
As soils dry, soil hydraulic conductivity (Ks) declines nonlinearly and can become a dominant bottleneck to root water uptake, constraining plant gas exchange. Although drought regulation involves both physiological and structural mechanisms, it remains unclear how these mechanisms differ between plants exposed to drought during early development versus at later developmental stage, and how soil texture and its hydraulic behavior shape regulation of soil–plant water relations. The objective of this study was to resolve how the timing of drought exposure reorganizes regulation of the soil–plant–atmosphere continuum (SPAC). Specifically, we aimed to (i) compare drought imposed from early vs at late developmental stage in terms of their reliance on physiological versus structural mechanisms of water-use regulation, and (ii) assess how soil texture and hydraulic trajectories condition these mechanisms.
We addressed these objectives using a controlled phenotyping experiment with six maize genotypes (three landraces and three hybrids) grown in contrasting soil textures (sandy loam and silt loam). Drought was imposed either continuously from the onset of growth or at later stage of plant development. Whole-plant transpiration, plant and soil water potentials, and above- and belowground structural traits were quantified to resolve SPAC regulation under contrasting drought timings.
Across soils and genotypes, transpiration declined to comparable fractions of its maximum within a narrow range of Ks, despite large differences in soil water content (θ) and matric potential (Ψsoil) between sandy loam and silt loam, this identifies Ks rather than θ or Ψsoil as the dominant physical control governing transpiration downregulation. Additionally, SPAC regulation differed strongly with drought timing. Under drought, imposed from early development, plants primarily reduced whole-plant water use through structural downscaling, characterized by reduced shoot area and increased root-to-shoot ratios, while maintaining relatively high transpiration rates per unit leaf area. In contrast, plants exposed to drought at later stage retained larger shoot area but reduced transpiration predominantly through strong stomatal regulation, resulting in lower transpiration rates per unit leaf area at comparable Ks and xylem water potential.
Belowground responses mirrored these contrasting strategies. Drought from onset promoted coordinated structural adjustment, including higher total root length, finer mean root diameters, and enhanced rhizosheath formation relative to late drought. These traits increased effective uptake surface area and were associated with higher soil–plant hydraulic conductance under low Ks. Across soils, high-performing plants converged on a common belowground trait syndrome, characterized by high total root length, fine roots, and enhanced rhizosheath formation, although the genotypes expressing this syndrome differed between soil textures.
Overall, our findings show that drought responsiveness emerges from the interaction between the soil’s hydraulic limit and its timing during development. Accounting for the temporal dynamics of hydraulic constraint, rather than treating drought as a static stress, providing a mechanistic framework to link soil texture, plant traits, and genotypic performance, with implications for targeted breeding and improved crop resilience under increasing climate extremes.
How to cite: Gupta, S., Wild, A. J., Heid, A., Thiel, J., Humpert, J., Wiesmeier, M., Lueders, T., Pausch, J., Hafner, B., and Zare, M.: The Timing of Soil Hydraulic Constraints Shapes Plant Drought Responses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13463, https://doi.org/10.5194/egusphere-egu26-13463, 2026.
Climate change is associated with rising temperatures and an increased frequency of drought events. Plants growing in water-limited environments must develop strategies to adapt to soil water availability. In the short term, stomatal regulation enables the control of transpiration and maintenance of plant water status during drought. Under prolonged water deficit, plants are expected to adjust their shoot-root allocation to sustain growth and survival. Although these adaptive responses are conceptually intuitive, the underlying processes and controlling factors remain poorly understood. Understanding short- and long-term plant responses to drought is crucial for investigating plant adaptation to climate changes.
In this work, we hypothesize that soil properties and climatic demand are key factors affecting plant stomatal conductance in the short term and root-to-shoot surface ratio (RSSR) over the longer term. Indeed, results of a simplified soil-plant hydraulic model demonstrated that the regulation of stomatal conductance and of RSSR should be texture dependent. We investigate these relationships through experiments conducted under controlled environmental conditions. Specifically, we assess how soil water content and soil type influence the RSSR of an isohydric species (maize) and an anisohydric species (sunflower). The experimental findings are subsequently analysed using a simplified soil-plant hydraulic model.
The experiment was conducted in a growth chamber controlling photoperiod, temperature, relative humidity, PAR, and VPD. Maize and sunflower were grown in pots using two contrasting substrates, sand and loam, whose hydraulic properties were characterized using the Hyprop system. Two irrigation regimes were imposed to maintain soil water content within predefined target ranges. Each of the 8 species × substrate × treatment combinations included 10 replicates.
Root and shoot biomass and surface were measured at 3 collects to capture plant growth dynamics. Soil water content was monitored by gravimetric measurements before and after each irrigation, with irrigation volumes adjusted to maintain the target moisture range. In addition, stomatal conductance and leaf water potential were punctually measured to characterize plant functioning.
We used a simplified soil-plant hydraulic model representing the system as three resistances in series (soil, roots, xylem), driven by soil-to-leaf water potential gradients (Carminati & Javaux, 2020). This model was employed to predict the optimal RSSR maximizing carbon assimilation while minimizing the risk of embolism.
Our results show that, despite differences in leaf and root surfaces, RSSRs remain within a similar range for both species. RSSR adaptation to soil texture is lower in maize (isohydric) than in sunflower (anisohydric). In addition, RSSR strongly depends on soil water potential (ψsoil), with a stronger response in sunflower. This relationship is further constrained by soil texture through its hydraulic conductivity. For a given RSSR, plants grown in loam are able to sustain at lower ψsoil compared with those grown in sand. To survive at similar ψsoil in a sandy soil, plants would require a substantial increase in RSSR. However, root active surface depends on soil types and modulates the RSSR-ψsoil relationship. Model predictive potential could be further improved by including additional information on active root surface.
How to cite: Delvoie, B., Cecere, A., Fauconnier, S., Carminati, A., and Javaux, M.: Root-to-shoot surface ratio adaptation to soil hydraulic constraints: linking experiments to a soil-plant hydraulics model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7769, https://doi.org/10.5194/egusphere-egu26-7769, 2026.
Plant water regulation plays a critical role in land–atmosphere coupling and ecosystem responses to climate extremes. Isohydricity is widely used to characterize how plants regulate water loss under water stress, yet its behavior under interacting drought and salinity remains poorly understood. Here, we investigated maize (Zea mays L.) water-use strategies under combined water and salinity constraints using a controlled pot experiment. Maize plants were exposed to two water availability regimes (well-watered and drought conditions) and irrigated with either fresh or saline water. Isohydric behavior was assessed using three complementary hydraulic relationships: (i) transpiration rate (normalized by leaf area) versus soil water potential, (ii) leaf water potential versus soil water potential, and (iii) stomatal conductance versus leaf water potential. In addition, the vulnerability of soil–plant hydraulic conductance was also examined.
Under drought or salinity applied separately, maize tended to exhibit more anisohydric behavior, characterized by relatively weak reductions in transpiration and stomatal conductance with declining water potential and a broader range of leaf water potential variation. In contrast, when drought and salinity occurred simultaneously, maize shifted toward a more isohydric mode of regulation, clearly differing from responses under single stress conditions. Moreover, under drought conditions, isohydricity inferred from the leaf–soil water potential relationship tended toward a more isohydric behavior under saline treatment, whereas isohydricity inferred from transpiration- and stomatal conductance–based relationships under salinity indicated a more anisohydric behavior. This discrepancy highlights the influence of evaluation methods on isohydricity characterization. Furthermore, we conclude that maize isohydricity is closely linked to the vulnerability of soil–plant hydraulic conductance. Under drought or salinity conditions, maize tends to exhibit more anisohydric behavior, which is associated with enhanced resistance of the soil–plant hydraulic system to the loss of hydraulic conductance. These findings advance our understanding of crop water relations under combined water and salinity stress and support integrated irrigation and salinity management strategies to improve water use efficiency and sustain yields in salt-affected regions.
How to cite: Shao, X. and Lei, G.: Interacting drought and salinity reshape maize isohydric behavior through soil–plant hydraulic constraints, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2178, https://doi.org/10.5194/egusphere-egu26-2178, 2026.
The subsoil contains valuable nutrient and water resources for crop production, but high penetration resistance impedes root growth and therefore resource access. Large-sized biopores formed by deep-rooting perennial taprooted crop species such as chicory and lucerne can provide pathways through compacted subsoil layers. Different field and mesocosm experiments have shown that colonization by anecic earthworms modifies physical and biochemical properties of biopore networks and pore walls, further increasing attractivity of biopores for crop roots. The intensity of biopore exploration by crop roots and resulting nitrogen uptake from biopore walls as assessed with a combination of classical root-length density determination, in-situ endoscopy and 15N-labelling varies across different crop species and seems to be largely determined by root architecture. Long-term field observations show that benefits of precrops forming large-sized biopores for following crops in terms of water and nutrient uptake as well as grain yield generally in dry years and particularly pronounced for spring-sown cereals.
How to cite: Athmann, M.: Root-soil interactions in biopores and their role in climate adaptation of cropping systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-22888, https://doi.org/10.5194/egusphere-egu26-22888, 2026.
Climate change is intensifying droughts and threatening food security. Roots are the plants’ organ for water uptake and are crucial for their adaptation, with their structure being a decisive factor. In barley (Hordeum vulgare), lateral roots form~60% of the total root length and are important for water uptake. Hydraulic conductance scales strongly with root diameter: thicker laterals conduct more water per unit length but demand higher carbon for construction and maintenance. During soil drying, this creates a potential carbon-water trade-off. We test whether such a trade-off exists and whether it shapes drought resilience across environments by comparing the diameter that optimizes the trade-off with that maximizing shoot dry mass (SDM).
We used a functional–structural plant model (OpenSimRoot) to simulate barley growth across five climatically and pedologically contrasting global sites, representing different drought regimes. Simulations covered 50 growing seasons (2000–2049) using projected climate data and site-specific soils. Five lateral root diameter classes were evaluated, and outputs included shoot dry mass, root carbon allocation, and root hydraulic conductance. Drought performance was assessed by jointly considering productivity and efficiency-based metrics related to carbon investment and water transport capacity.
Across all environments, barley performance showed a clear dependence on lateral root diameter, with intermediate diameters generally balancing water uptake capacity and carbon costs. SDW and trade-off analyses converged on to the same diameter, reflecting a general trend. However, site-specific analyses revealed substantial divergence, reflecting differences in climate variability, soil properties, and drought characteristics. In several environments, finer lateral roots did not consistently confer advantages in either hydraulic efficiency or biomass production, challenging the notion of a universally optimal “cheap-root” strategy under drought.
A robust carbon–water trade-off underlies lateral root diameter; the diameter that performs best depends on the environment (climate and soil) and the objective (e.g., maximizing SDW versus efficiency/resilience). When data are pooled across all sites, SDM- and trade-off–based optima coincide, but site-level results differ; therefore, breeding for drought resilience should target site- and objective-specific trait values rather than a single fixed optimum.
How to cite: Fang, B., Postma, J., and Kuppe, C.: The resilience of barley to drought in a changing climate is determined by its lateral root diameter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5060, https://doi.org/10.5194/egusphere-egu26-5060, 2026.
The objective of this study is to investigate experimentally how plants adjust their structural and functional properties when facing soil water heterogeneity from the plant down to the organ scales. We developed a novel rhizotron platform, each rhizotron equipped with 9 hydraulically isolated compartments, wherein constant spatial patterns of local soil water potential can be imposed while monitoring water consumption and root development. In the validation experiment, maize plants (cv. B104) were grown under constant and homogeneous water potential in this rhizotron platform for four weeks, before entering a fifth week in which different levels of water potential were imposed. The desired local soil water potentials were successfully applied and adjusted. The local water consumption and root morphological trails were monitored in real time, indicating that root water uptake and root elongation correlate with root age and local soil moisture. At the whole-plant scale, more negative soil water potentials resulted in a lower cumulative water uptake, while at the local scale, cumulative water uptake within individual compartments increased more rapidly as root length within the same compartment increased, indicating a direct coupling between local root development and local water extraction. These observations highlight a strong spatial-temporal linkage between root trails and soil water conditions. Together, the validated rhizotron platform enables root plasticity studies by establish a quantitative and dynamic measurements for soil–root hydraulic interactions at the plant and organ scale, providing a promising platform for future studies exploring how maize plants respond to spatial and temporal heterogeneity in soil water environments.
How to cite: Wei, T.-J., Draye, X., and Javaux, M.: A novel rhizotron platform for studying root–soil hydraulic interactions in heterogeneous environments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21300, https://doi.org/10.5194/egusphere-egu26-21300, 2026.
Plants respond to soil and atmospheric water deficits through strategies such as stomatal regulation and belowground adaptations. Root mucilage buffers erratic fluctuations in the rhizosphere water content, yet its influence on soil hydraulic properties, especially unsaturated hydraulic conductivity, and stomatal regulation remains unknown. We hypothesized that mucilage facilitates water uptake by attenuating the drop in matric potential at the root–soil interface during soil and atmospheric drying. We measured the impact of various maize (Zea mays) mucilage contents (0.0%, 0.05%, 0.2%, and 0.4%) on the water retention and hydraulic conductivity of a loamy soil. Leveraging a soil–plant hydraulic model, we investigated the effects of mucilage contents on transpiration and stomatal responses under soil drying and increased vapor pressure deficit (VPD). Higher mucilage contents prevented sharp declines in unsaturated hydraulic conductivity as soils dried. Simulations revealed that higher mucilage contents delayed the onset of hydraulic stress (the threshold transpiration rate beyond which a small increase in transpiration would result in a disproportionate decline in leaf water potential), broadened the hydroscape zone, and shifted stomatal behavior from isohydric to more anisohydric regulation, enabling plants to sustain stable transpiration and lower midday leaf water potentials under drought. The buffering effects on soil–plant hydraulics persisted across varying degrees of VPD, although high mucilage contents accelerated soil drying, indicating a trade-off between improved water uptake and faster moisture depletion during prolonged drought. Our findings underscore the important role of mucilage in modulating soil–plant water relations and stomatal regulation, offering insights into strategies for improving plant responses to soil and atmospheric drought.
How to cite: Akale, A., Cai, G., Diamantopoulos, E., Leuther, F., Kersting, L., McAdam, S., Liu, S., and Ahmed, M. A.: Root mucilage alters stomatal responses to soil and atmospheric drought, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20137, https://doi.org/10.5194/egusphere-egu26-20137, 2026.
Root hairs are assumed to enhance plant water uptake by increasing root surface area and effective root radius, thereby reducing dissipation of soil water potential in the rhizosphere and increasing transpiration. However, recent field observations indicate that their dominant hydraulic role emerges at short time scales through dynamic regulation of the soil–plant system rather than through steady-state flux enhancement.
Field measurements show that transpiration rates scale with soil texture, with plants in coarse-textured soils transpiring at lower rates than those in finer soils. This reduction reflects longer-term structural and physiological adjustment of the plant (e.g. shoot–root allocation), rather than short-term stomatal control. In contrast, steady-state transpiration has little sensitivity to the presence or absence of root hairs. Instead, plants lacking root hairs exhibit rapid and pronounced dissipation and oscillations of leaf water potential during periods of high atmospheric vapor pressure deficit, particularly in coarse-textured soils. These fluctuations occur on time scales of minutes to tens of minutes, overlapping with typical stomatal response times. In contrast, plants with root hairs showed smooth, non-oscillatory leaf water potential dynamics.
We propose that the most prominent hydraulic effect of root hairs is to buffer excessive oscillations in leaf water potential that are too fast compared to stomatal response kinetics. Root hairs introduce a physical buffering component by increasing the volume of water that can be extracted from the rhizosphere. In this way root hairs integrate short-term fluctuations in transpiration demand and damp rapid water potential changes. In the absence of root hairs, this buffering term is missing, leaving the system vulnerable to high-frequency disturbances that outpace stomatal adjustment.
To investigate this mechanism, we develop a mechanistic soil–plant hydraulic model that explicitly represents rhizosphere processes associated with root hairs and couples them with a dynamic stomatal response model. The model resolves transient water flow and storage and is used to quantify how root hairs modify system capacitance, damping, and stability across soil textures and atmospheric demand.
By focusing on transient dynamics rather than steady-state fluxes, this modelling study advances fundamental understanding of root water uptake regulation and highlights the rhizosphere as a key hydraulic bottleneck which affects the whole plant hydraulic system.
How to cite: Stoll, F., Duddek, P., and Carminati, A.: Root Hairs as an Integral Buffer in Stomatal Control of Plant Water Status, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12447, https://doi.org/10.5194/egusphere-egu26-12447, 2026.
Soils represent the largest terrestrial reservoir of organic carbon, with dissolved organic matter (DOM) acting as its most mobile and reactive fraction and the immediate precursor to mineral-associated organic matter, the dominant long-term carbon pool. While DOM dynamics have been extensively studied in bulk soil and the rhizosphere, the hyphosphere—soil influenced by fungal hyphae—remains comparatively understudied, despite the extraordinary spatial reach, rapid turnover, and mineral surface interactions of mycorrhizal fungi. Disentangling root- versus hyphal-derived dissolved organic carbon (DOC) inputs is therefore critical for understanding how recent plant carbon is redistributed and stabilized in soils.
Here, we applied a nested ingrowth core system to experimentally separate rhizosphere and hyphosphere DOC pools under semi-controlled greenhouse conditions. The system consisted of an outer mesh core permitting root and hyphal access and an inner fine-mesh core allowing hyphal ingrowth only, both filled with inert sand. Ingrowth cores were installed in pots containing native tree species planted in monocultures and mixtures. At harvest, distinct sand fractions representing bulk sand, rhizosphere, and hyphosphere subsets were recovered and extracted for total organic carbon (TOC) analysis; samples are being further characterized using untargeted metabolomics.
Preliminary results indicate clear differences in TOC concentrations among compartments, with highest values in rhizosphere samples, intermediate values in the hyphosphere, and lowest concentrations in bulk sand. Species composition exerted a strong influence on total TOC concentrations, and root ingrowth into the outer cores varied markedly among species. Metabolomic analyses are currently in progress and will be used to further assess compositional differences between rhizosphere- and hyphosphere-derived DOC.
Together, this work highlights the hyphosphere as a distinct and experimentally accessible domain of DOC production and underscores the need to explicitly consider fungal pathways when linking fresh carbon inputs to persistent soil organic matter formation.
How to cite: Werner, R., Goebel, M., Kessler, A., and Bauerle, T.: Disentangling hyphal- and root-derived contributions to dissolved organic carbon in mixed tree systems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16718, https://doi.org/10.5194/egusphere-egu26-16718, 2026.
Plants and their ability to capture atmospheric CO2 are indispensable for the buildup of soil organic matter, underscoring their crucial role in terrestrial carbon cycling. Yet, the plant physiological processes regulating soil carbon inputs and their environmental controls remain severely underrepresented in soil carbon research, which limits our understanding of soil carbon sequestration potential across biomes and land uses. Root biomass constitutes a major input of organic matter to soil that is particularly difficult to estimate. Here, we outline a framework for the explicit integration of root growth physiology into soil carbon dynamics. Using data acquired in rice (Oryza sativa, L.), we provide mechanistic evidence that the expansion of cortical cells in growing roots is a key process determining the fate of the carbon plants allocate to their root system. We combined measurements of carbon partitioning between biomass formation and respiration in growing roots with three-dimensional quantifications of root cortical cell size using high resolution (1.8 μm) X-ray Computed Tomography. With increasing cortical cell size, indicating greater contribution of cell expansion over cell division to root growth, more carbon was allocated to root biomass formation and less to root respiration (R2 = 0.83). We then integrated our experimental findings with data obtained from the literature covering different land use types to highlight the fundamental importance of including root physiological processes in estimating soil carbon inputs. The established structural-functional relationships between root cortical cell size and carbon partitioning point out the paramount role of root physiology in improving our understanding and prediction of carbon fluxes and retention in plant-soil systems. We therefore propose that measurements of root cortical anatomy be included when assessing global change impacts on soil carbon inputs and the potential of soils to sequester carbon.
How to cite: Colombi, T., Herrmann, A., Atkinson, J., Bhosale, R., Mooney, S., Sturrock, C., and Sjögersten, S.: Divide or expand? Implications of root growth physiology for soil carbon inputs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8245, https://doi.org/10.5194/egusphere-egu26-8245, 2026.
Plants actively modify the physical and chemical properties of the rhizosphere to regulate water and nutrient supply, particularly under soil drying conditions. Root mucilage has emerged as a key mediator of these interactions, yet quantitative, mechanistic evidence for how its hydraulic function depends on soil texture and moisture remains scarce. Here we synthesize results from a series of complementary experiments that together demonstrate that rhizosphere hydraulic regulation is an active, texture-dependent process driven by targeted carbon investment belowground.
We combined controlled rhizosphere model systems, isotope tracing, and neutron radiography to disentangle how mucilage alters water retention, unsaturated hydraulic conductivity, and solute diffusion across contrasting soil textures. Using mucilage extracted from maize seedlings, we quantified its effects in sand, sandy loam, and loam under varying moisture conditions. In parallel, we employed 14C pulse labelling and neutron imaging to directly link plant carbon allocation patterns to rhizosphere hydraulic outcomes under contrasting soil texture and water availability.
Across experiments, mucilage effects on rhizosphere hydraulics were strongly texture dependent. In coarse-textured soils, relatively high mucilage concentrations were required to increase water-holding capacity, whereas in finer-textured soils even small additions substantially enhanced retention. Mucilage reduced calcium diffusion in sandy soils across moisture levels, reflecting increased liquid-phase viscosity, while in fine-textured soils it prevented the sharp decline in diffusion during drying by maintaining liquid connectivity. Neutron radiography revealed consistently wetter rhizosphere zones compared to bulk soil, with the strongest hydration gradients occurring in sandy soils, precisely where hydraulic continuity is otherwise most fragile.
Carbon tracing further showed that plants actively adjust their belowground investment in response to soil physical constraints. In sandy soils, particularly under dry conditions, seminal, lateral, and crown roots exhibited elevated 14C allocation to the rhizosphere, indicating enhanced exudation. This sustained carbon investment coincided with root system architectures that maintained access to hydraulically buffered zones near the root surface. Together, these observations demonstrate that plants deploy more, and hydraulically more effective, mucilage where soil texture imposes the strongest physical limitations on water flow.
Taken together, these findings establish a mechanistic link between soil texture, carbon allocation to root exudation, and rhizosphere hydraulic regulation. They reposition mucilage from a passive by-product of root growth to a central component of plant drought strategy and highlight rhizosphere engineering as a key process shaping plant water relations across soils. This perspective opens new avenues for incorporating soil physical context into models of plant drought response and for developing soil- and crop-specific strategies to improve root-zone water availability under increasing climate extremes.
How to cite: Zare, M., Hosseini, B., Adamczewski, R., and Spinoso Sosa, S.: Plants as Engineers: Carbon Investment and Hydraulic Control in the Rhizosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5961, https://doi.org/10.5194/egusphere-egu26-5961, 2026.
Biological activity in soil is very diverse and around plant roots it affects water transport. Root growth displaces soil particles and alters soil porosity, by creating biopores that conduct water. The secretions of plants and microbes modify surface tension, viscosity, absorption and retention of water. Microbial motility may also contribute to water transport, but such effects have not been demonstrated in soil to date. To elucidate how these factors influence root water uptake, we combined dye tracing experiments [1,2], live microscopy and physical characterization of root exudates of winter wheat, along with analyses of cell suspensions and secretions of the bacterium Bacillus subtilis. Using this dataset, we coupled a modified Richards’ equation [3] with the model of Šimůnek and Hopmans [4] to investigate how the combined effects of these processes influence water availability to crops over a complete wet–dry–wet cycle. Results showed that both microbes and plants’ secretions act as facilitators of water infiltration of dry and mildly repellent soil layers. In arid environments, under light and sporadic rainfall events, this effect tends to benefit more deeper-rooted or mature crops. Results also show that microbial motility alone may be inducing an active stress of few Pascals which also contributes to enhance water infiltration. These results have important implications for the management of irrigation in cropping systems.
References
[1] Liu et al 2025, Biosystems Engineering, https://doi.org/10.1016/j.biosystemseng.2025.02.006
[2] Gómez et al 2025, Plant Cell Environment, https://doi.org/10.1111/pce.70240
[3] Mair et al 2025, Vadose Zone Journal, https://doi.org/10.1101/2025.03.28.645940
[4] Šimůnek and Hopmans 2009, Ecological Modelling, 220(4), 505–521
How to cite: Dupuy, L., Mair, A., Mezza Manzaneque, B., Gomez Preal, E., Martín Sanchez, I., de las Heras Martínez, G., Natalia Elguezabal Vega, N., Lindner, A., Clement, E., Stanley-Wall, N., and Ptashnyk, M.: Mechanisms of facilitation of water transport in the rhizosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-102, https://doi.org/10.5194/egusphere-egu26-102, 2026.
Soils play a critical role in regulating plant water availability, with characteristics like bulk density, porosity, and texture determining soil hydraulic properties, that is, properties that affect the soil water retention and water transport. Together with mycorrhizal activity, which influences the conductance of water between the soil and the roots, soil hydraulic properties affect the ease with which plants can access soil water. In turn, root growth also modifies soil structures and mycorrhizal communities, influencing soil water retention and soil hydraulics. Despite a good theoretical understanding of the dynamic interactions between soils and plants, limited information is available on: (i) how much soil texture affects plant hydraulic properties across plant species; and (ii) how much plant roots affect soil hydraulic properties across soil textures. To assess the extent of the feedback loop between soil and plant hydraulics, we transplanted 4-year-old Quercus robur (N=12) and Quercus cerris (N=12) saplings into either a loam or a clay loam, in equal numbers for each species. Following an acclimation period of three to five months, a total of 28 soil water retention curves were measured from soil cores collected at depths of 7-12 cm, 25-30 cm, and 55-60 cm in the vicinity of the trees (i.e., likely to contain root fragments, mycorrhiza, etc.). We measured a further eight water retention curves in the absence of trees, allowing the determination of a baseline of soil hydraulic characteristics. Finally, after the soil sample collection, we established two hydraulic vulnerability curves per tree. Preliminary results show no indication of plant hydraulic acclimation to soil under well-watered conditions. The presence of tree roots affected soil bulk density at depth in the loam, as well as hydraulic properties like the field capacity at -33 kPa and the permanent wilting point, but not in the clay loam. Whether these effects are the same after longer acclimation periods or under water-stress conditions remains to be determined.
How to cite: Tang, Z., Sabot, M., García Leher, A., Hildebrandt, A., Pachmann, A., Verhoef, A., Weber, E., and Wittig, M.: Rooted in reciprocity: interactions and feedbacks in the soil-plant hydraulic continuum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15088, https://doi.org/10.5194/egusphere-egu26-15088, 2026.
Polyphosphates (poly-P), consisting of two or more phosphate residues, are not directly available to plants and must first be hydrolyzed to orthophosphate (ortho-P). Although microbial polyphosphatase activity is well established, there is currently no evidence for extracellular poly-P-hydrolyzing enzymes produced by plants in the rhizosphere. This study investigated the capacity of plants to hydrolyze and utilize long-chain and cyclic poly-P forms and sought to identify extracellular poly-P hydrolytic activity of plant origin.
Six plant species were cultivated under sterile conditions with either cyclic poly-P or ortho-P as the sole phosphorus source. Pronounced interspecific differences were observed in poly-P utilization. Lettuce exhibited limited growth on poly-P, whereas pepper achieved biomass levels comparable to those supplied with ortho-P, providing direct evidence of rhizospheric poly-P hydrolysis. Enzymatic assays using intact plant tissues revealed significantly higher hydrolytic activity in pepper roots than in lettuce, while leaves showed minimal activity in both species.
Protein extracts from pepper roots were further analyzed to characterize the enzymatic activity. Poly-P hydrolysis was abolished by heat treatment, confirming enzymatic involvement. Fractionation by fast protein liquid chromatography (FPLC) led to the isolation of an approximately 20 kDa protein displaying strong poly-P hydrolytic activity, exceeding that of known plant phosphatases. The enzyme preferentially hydrolyzed shorter poly-P chains, with activity declining as chain length increased.
These findings provide the first evidence for a polyphosphatase-like enzyme in vascular plants. The identification of an extracellular, root-derived enzyme capable of hydrolyzing long-chain poly-P challenges the prevailing paradigm that plants rely exclusively on soil microorganisms for the conversion of complex polyphosphates into bioavailable forms.
How to cite: Toren, N. and Erel, R.: Evidence for a Polyphosphatase-Like Enzyme Catalyzing the Hydrolysis of Long-Chain Polyphosphates in the Rhizosphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21534, https://doi.org/10.5194/egusphere-egu26-21534, 2026.
Climate change is increasing risks to agriculture and soil stability, with soil erosion and flooding being significant global threats that reduce crop yields and degrade soil quality. Tightly correlated with the soil’s response to these changes are the impactful and diverse soil microbiota. As primary drivers of organic matter decomposition, microorganisms convert plant inputs into humus and cell residues. This enhances soil’s physical structure, improves pore formation, and consequently, water-retention and infiltration capacity.
To identify and model the effects of agricultural practices, the CARA project [1] is implementing bacterial traits to improve soil resilience under current and future rainfall conditions. This was achieved using a carefully designated rainfall simulator, capable of precisely regulating droplet size and precipitation intensity while maintaining natural terminal velocity, thereby enabling the recreation of various rainfall scenarios. Two scenarios were selected and tested on artificial soil columns with varying content of compost-based organic matter: a current scenario, relating to the precipitation events in Austria, and a future scenario, anticipating increased rainfall intensity and longer dry periods. Furthermore, certain soil columns were supplemented with animal- and plant-based liquid fertilizers to enhance microbial activity.
The aim was to assess the influence of microbial activity on soil structure and its capacity for water retention. We identified that the precipitation scenarios exhibited distinct microbiomes across the treatments and over time, with rainfall intensity influencing soil microbial communities by washing out specific taxa, such as Bacilli and Limnochordia, which were subsequently detected within the leachate. Validation experiments in microcosms confirm the observed evaporation reduction and the treatments with liquid fertilizer showed the highest water retention. Our findings offer a basis for evaluating microbiome-based strategies to enhance soil resilience under climate-driven changes in rainfall patterns.
[1] Climate change adaptation through flood-reducing agriculture (CARA): https://projekte.ffg.at/projekt/4754252
How to cite: Vukosavljevic, H., Li, X.-Y., Monschein, M., Wicaksono, W. A., Schneider, J., Berg, G., and Bickel, S.: Impact of heavy rainfall and liquid fertilizers on microbial communities and leachate in compost-amended soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11437, https://doi.org/10.5194/egusphere-egu26-11437, 2026.
Soil structure plays a vital role in ecosystem functioning. Earthworms and plant roots are key bioturbation agents crucial to building and maintaining soil structure suitable for agriculture. However, following soil compaction, the succession of biophysical activity between these agents remains unclear and understanding this dynamic is critical for sustainable soil management. This study utilised imaging techniques to assess how compaction affects bioturbation by endogeic earthworms and barley roots and their impact on soil functionality (e.g. hydraulic conductivity, water retention, etc.). To this end, two experimental systems were established: (i) rhizoboxes for 2D imaging, photographed regularly over a six-weeks, and (ii) PVC cylinders for X-ray computed tomography (XCT), scanned at trial end. Each system included compacted and uncompacted treatments, with earthworms and barley co-incubated. Compacted systems were surface loaded at 150kPa. Rhizobox imaging tracked biopore formation and interactions between bioturbation agents, while XCT provided high resolution 3D structural data subsequent to bioturbation. Image analysis involved segmenting biopores using thresholding and filtering techniques, such as median and Gaussian for the 2D images and non-local means for 3D XCT images. These methods enabled us to compare the structural characteristics of the biopore systems (i.e. number of biopores, branches, thickness, branch length, etc.). Both image types were skeletonised and combined with local thickness maps to extract the structural metrics assessed. Results showed compaction reduced mean trends in earthworm bioturbation activity, while root activity largely stayed the same. The results from the XCT data showed that hydraulic conductivity increased markedly after bioturbation, increasing two orders of magnitude in uncompacted and three orders of magnitude in compacted soil. We concluded that for soil restoration, this suggests a sequential approach, with initial cover crop planting to alleviate compaction stress, enabling earthworms to proliferate and create the structure needed to maintain healthy soil functioning and productivity.
How to cite: Clark-Hattingh, O., Wright, C., Nazemi, E., Alvarez Borges, F., Sandom, C., Roose, T., McKay Fletcher, D., Williams, K. A., and Ruiz, S.: Earthworm and Plant Root Bioturbation Succession in Compacted Soil Revealed by 2D Rhizobox and X-ray CT Imaging, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11319, https://doi.org/10.5194/egusphere-egu26-11319, 2026.
Soil structure can mitigate both mechanical impedance and water stress, thereby modulating root elongation and access to deep soil water. Although process-based root growth models represent soil–root interactions, they rarely account explicitly for structural conditions and their consequences for the combined effects of water and mechanical stresses on root growth. We quantify how soil structure under no-tillage influences soybean root elongation, effective rooting depth, and water-deficit mitigation, and we parameterize these effects in a biophysical root-growth model. A long-term field experiment established in 2016 compared three cropping systems preceding soybean (Glycine max): ruzigrass (Urochloa ruziziensis), maize (Zea mays), and fallow. Soybean root length density and soil physical attributes were measured in nine layers down to 210 cm. Effective rooting depth was defined as the depth containing 95% of total root length. Plant-available water was computed from soil water retention between −60 and −15,000 hPa, and readily available water was assumed as 50% of plant-available water within the rooted zone. Grain yield was determined at harvest. In addition, soybean root elongation rate was measured in the laboratory using core from field and repacked samples across gradients of degree of saturation and soil penetration resistance. The structural effect was incorporated as a parameter in a biophysical model that combines water and mechanical limitations to root elongation. Increasing soil penetration resistance from 1.0 to 3.5 MPa reduced relative root elongation by 46% in preserved structure, whereas reductions reached 76% in repacked soil. At 0.5 MPa and 60% degree of saturation, elongation in repacked soil was 29% higher than in preserved structure, but both structural conditions converged as soil penetration resistance increased to 1.0 MPa. Under 90% degree of saturation, elongation in preserved structure was nearly threefold that in repacked soil. In the field, effective soybean rooting depth (in a trench of 210 cm depth) differed among previous cropping systems, with ruzigrass promoting substantially deeper roots (154.7 cm at 95% cumulative distribution) compared with maize (127.9 cm) and fallow (121.0 cm). Root length density in the 0 to 10 cm layer was highest after ruzigrass (4.72 cm cm-3), followed by maize (3.33 cm cm-3) and fallow (2.48 cm cm-3). Cumulative root length in the soil profile from 0 to 210 cm reached 202.2 cm cm-2 after ruzigrass, compared with 128.4 cm cm-2 after maize and 94.3 cm cm-2 after fallow. Soybean yield was 2.9 (after ruzigrass), 2.6 (after maize), and 2.1 Mg ha-1 (after fallow). Plant-available water in the soybean root zone was 175 mm after ruzigrass, compared with 145 mm after maize and 140 mm after fallow, indicating a 25% increase relative to fallow. Assuming evapotranspiration of 7 mm d-1, this represents approximately 15 days of water supply after ruzigrass versus 12 days after fallow. Preserved soil structure improved soybean root performance under strong physical constraints and increased deep water access. Explicitly representing soil structural conditions in simulation models can improve predictions of rooting depth and drought mitigation under no-tillage.
Acknowledgements: AGRISUS Foundation [PA 3534/23], CNPq [409621/2023-4] and FAPESP [23/10427-3 and 23/11945-8].
How to cite: Tuzzin de Moraes, M., Quecine Grande, L. H., dos Santos, J. K., Batista Neri Pereira, M., Paiva de Lima, R., Balbinot Junior, A. A., and Debiasi, H.: Soil Structure under No-Tillage Enhances Soybean Root Growth and Access to Subsoil Water, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15727, https://doi.org/10.5194/egusphere-egu26-15727, 2026.
Emerging contaminants in agricultural soils and irrigation water present significant threats to food safety and environmental health through their uptake and accumulation in edible plant tissues. This study presents a dynamic multicompartment plant-uptake model to simulate the fate and transport of both neutral and ionizable compounds under conditions involving pre-existing soil contamination or continuous contaminant loading via different agricultural practices. The model characterises chemical behaviour across soil, roots, stem, leaves, and fruits, explicitly accounting for gaseous exchange, volatilisation losses, atmospheric deposition, xylem- and phloem-driven translocation, growth dilution, and organelle-level partitioning within plant cells. A comparison of the framework's predictions with previously published multicompartment plant-uptake datasets reveals its ability to predict the observed uptake, transport, and redistribution patterns across plant organs. The model's integration of key physicochemical, physiological, and environmental drivers into a unified mechanistic platform enhances its ability to predict contaminant transfer through the soil–plant continuum. The proposed framework can support risk assessments, guide the selection of safer irrigation sources, and inform management strategies for agricultural systems affected by historical pollution or poor-quality irrigation water.
How to cite: Meena, V. and Swami, D.: A Multicompartment Plant-Uptake Model for Neutral and Ionizable Compounds: Development and Validation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1159, https://doi.org/10.5194/egusphere-egu26-1159, 2026.
Croplands are among the systems most vulnerable to shifts in precipitation regimes and prolonged droughts particularly in temperate climates. Although irrigation may increase agricultural productivity, it can’t offer a sustainable long-term solution to compound droughts due to intensified pressure on freshwater resources. Thus, characterizing root water uptake patterns is essential to understand how crops maintain function while sustaining transpiration during drought. We investigated water uptake patterns of winter cereals (wheat, barley) across two contrasting growing seasons (2024, 2025). The research site is in central Germany, it exhibits a suboceanic/subcontinental climate and has a shallow groundwater level (ca. 1.5 m). In the footprint of an eddy covariance (EC) tower, we sampled plant leaves, soil water, precipitation, river water, and groundwater to trace stable water isotopes. We monitored leaf area index (LAI) and installed soil moisture sensors (5–100 cm). Using soil moisture time series and dual-isotope mixing models, we quantified variation in water uptake depth throughout the growing seasons (March-July). In 2024, soil layers were wetted by regular rains in April with only short rain-free periods occurring. On the contrary, frequent and longer dry spells occurred in 2025, totalling 18 days in April and 15 days in May. Moreover, in 2024, ETsoil ranged from 1.2 mm day⁻¹ to over 7 mm day⁻¹ at peak LAI, while ETEC-tower for the same period exceeded 5 mm day⁻¹. In 2025, despite high transpiration demand, ET did not exceed 5 mm day⁻¹ consistently in both methods. Soil water isotope patterns showed expected fluctuations, with deeper layers being depleted in δ²H and δ¹⁸O. We used the Craig–Gordon equation to determine xylem water isotope signatures, followed by mixing models to quantify water sources for transpiration. Xylem and soil water isotope time series suggest that despite more frequent rain events, winter wheat continued to draw water from stable, deeper sources rather than relying on enriched shallow soil layers (5–15 cm). During summer 2024 (June–July), δ²H and δ¹⁸O values in the topsoil enriched through higher soil evaporation, yet water uptake shifted to deeper layers, which agrees with ETsoil variations. Precipitation events in late spring 2024 enabled winter wheat to access deeper soil water sources (≥50 cm) to sustain high transpiration demand. During the drier conditions, barley altered water uptake depths yet transpiration demand was mainly sustained from water sources within 10–40 cm, and contribution from deeper layers was limited. Both species showed similar responses to dry spells, yet the timing of the drought shaped root plasticity and access to stable water sources. Our results demonstrate that water uptake strategies and water use efficiency are tightly linked to the timing and intensity of drought in annual crops, even when deeper water sources remain stable.
How to cite: Demir, G., Emad, A., Markwitz, C., Dubbert, D., Knohl, A., and Dubbert, M.: Drought-induced shifts in water uptake in winter cereals: Insights from multi-scale measurements across two contrasting years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1234, https://doi.org/10.5194/egusphere-egu26-1234, 2026.
Soil engineering is gaining increasing attention due to its potential to address soil scarcity while promoting waste recycling. However, functional soils do not arise from simply mixing waste materials. Instead, fundamental pedogenetic processes must be activated and supported, alongside the stabilization of organic carbon through complexation with mineral surfaces. Evidence suggests that interactions between plants and minerals could accelerate these early pedogenic processes—including carbon fixation and mineral–organic associations—while limiting carbon mineralization. This study reports the results of a field experiment conducted in Geneva to investigate these effects.
Excavated geological layers (DSH) from Geneva’s fluvio-glacial deposits were mixed with six levels of green waste compost (GWC) (10–90 %). Each plot was sown with a standardized indigenous plant mixture of 44 species, and plant diversity was maximized under the assumption that higher diversity would enhance the formation of a soil-like structure in the parent material. Treatments were replicated four times and monitored monthly for the first six months, with a final assessment at 12 months. Organic carbon forms were analyzed using Rock Eval® pyrolysis, and soil hydrostructural properties were evaluated through soil shrinkage analysis.
Results showed that a 25 % compost ratio promoted carbon stabilization, while the 10 % mixture demonstrated potential for carbon fixation and mineral–organic associations after 12 months, likely due to slower plant establishment in dry grassland. The 50 % compost mixture supported higher plant species richness, including ruderal and dry grassland species. Additionally, adding 10 % DSH to a 90 % GWC mixture reduced carbon mineralization compared with 100 % GWC, indicating potential for soilless applications. Overall, these findings suggest that pedogenic processes in engineered soils can be optimized by carefully selecting parent material-to-organic carbon ratios and plant combinations.
How to cite: Deeb, M., Deluz, C., Prunier, P., Morch, F., Frossard, P.-A., and Boivin, P.: Transforming excavation waste into functional soil: Effects of compost ratios and plant diversity on initial pedogenesis, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2609, https://doi.org/10.5194/egusphere-egu26-2609, 2026.
Deep rooting is a critical trait for drought tolerance, yet quantitative knowledge of root distributions across tree species and soil properties remains limited [1, 2]. This study characterises fine-root distribution patterns and maximum rooting depths in mono and mixed species forests based on ~2,000 soil profiles from Switzerland and it is intended to extend the study to the continental scale with root, tree and soil data from ICP Forests’ Level I and II plots.
Root presence was recorded semi-quantitatively along soil profiles together with maximum rooting depths and associated soil and stand properties. Species specific traits and soil properties were analysed, and root distribution curves (beta curves: Y=1-βd) were modelled to derive species- and soil-specific rooting patterns [3]. Trait-specific beta curves were then compared and analysed for site, stand, and soil properties, such as for topographic, and climate data, focusing on profiles only deeper than 1m soil depth, to avoid skewed beta calculations.
In monospecific stands (dominant species >50% canopy cover), linear models (LMs) explained 29.7% of beta variance across profiles. Tree species identity and soil density were the strongest contributors, while mean annual precipitation exhibited pronounced non-linear effects. Model parsimony improved strongly when tree species identity was aggregated into angiosperms and gymnosperms, although explanatory power decreased slightly to 27.4% of explained beta variance. On average, angiosperms showed a more homogenous fine-root distribution pattern (median β = 0.933) than gymnosperms (median β = 0.888).
In contrast, in mixed species stands, LMs explained 22.1% of beta variance. Tree species identity and soil type emerged as the primary drivers. In comparison, mixed species stands were more difficult to analyse and interpret than monospecific stands due to their higher structural and ecological complexity. Notably, strong collinearity was observed among soil type, hydromorphic condition, and soil density in both monospecific and mixed species stands.
Subsequently, we plan to integrate data from ICP Forests sites to test whether these relationships hold across broader climatic and edaphic gradients. With these results we aim to improve mechanistic modelling of soil water availability, root water uptake, and forest development under current and future climate conditions.
References
[1] Meusburger, K., Trotsiuk, V., Schmidt-Walter, P., Baltensweiler, A., Brun, P., Bernhard, F., Gharun, M., Habel, R., Hagedorn, F., Köchli, R., Psomas, A., Puhlmann, H., Thimonier, A., Waldner, P., Zimmermann, S., & Walthert, L. (2022). Soil–plant interactions modulated water availability of Swiss forests during the 2015 and 2018 droughts. Global Change Biology, 28, 5928–5944. DOI: 10.1111/gcb.16332.
[2] Pietig, K., Kotowska, M., Coners, H., Mundry, R., & Leuschner, C. (2026). Deep rooting revisited: Comparing the rooting patterns of European beech, Sessile oak, Scots pine, and Douglas fir in sandy soil to 3.8 m depth. Forest Ecology and Management, 600, 123288. DOI: 10.1016/j.foreco.2025.123288
[3] Gale, M. R. & Grigal, D. F. (1987). Vertical root distributions of northern tree species in relation to successional status. Can. J. For. Res. 17: 829-834.
How to cite: Ried, D. G., Carminati, A., Peters, R. L., Lehmann, M., Graup, L., Walthert, L., Waldner, P., Brunner, I., Bernhard, F., and Meusburger, K.: Quantifying Drivers of Root Depth and Distribution in European Forests: Species, Soil, and Climate Effects, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2974, https://doi.org/10.5194/egusphere-egu26-2974, 2026.
Soil-moisture memory (SMM) regulates the evolution of drought, hydrological predictability, and land–atmosphere coupling, yet many conventional diagnostic metrics simplify this complex phenomenon into a sole memory timescale. In this paper, we introduce a unified observation-driven framework—a scale-aware Linear Integro-Differential Equation (LIDE) for root zone soil moisture—to infer the complete distributed memory kernel that effectively models soil-moisture dynamics. When applied to multi-year in situ observations from energy-limited, water-limited, and intermediate hydro-climatic regimes, LIDE reveals a rich hierarchy of memory structures that conventional e-folding autocorrelation or hybrid deterministic-stochastic metrics are unable to capture. Application of LIDE in examined sites revealed a fast-memory timescale from ∼3–32 days, a short-term slow-memory timescale from 13 to 39 days, an intermediate slow-memory from ∼115–127 days, a long-term slow-memory from ∼218–541 days, and a theoretical saturation timescale from ~9 to 15 years. LIDE also provides additional quantitative information about memory strength, as assessed by actual memory capacity (Q∞), which is not available through conventional persistence analyses, with Q∞ being relatively constant over the examined sites (1.12–1.24 days⁻²) despite large hydro-climatic contrasts among sites. Applying LIDE on hourly, daily, and monthly data reveals that high-frequency data provides information on sub-daily fast memory timescales (~6 hours at the intermediate site, namely Schöneseiffen in Germany), as well as an additional very short slow-memory timescale (~14 hours at Schöneseiffen) that is not observable in daily or monthly data. The integrated kernel also accounts for the oscillatory saturation dynamics associated with soil-moisture reemergence, making it possible to retrieve this process from observations for the first time. Collectively, these results place LIDE as a state-of-the-art and state-of-the-practice approach in diagnosing multiscale memory of the soil moisture that is physically interpretable and scalable and can greatly advance drought sciences, ecohydrology, and land-surface modeling.
How to cite: Rahmati, M.: A Memory-Based, non-Markovian, Linear Integro-Differential Equation for Root-Zone Soil Moisture, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3805, https://doi.org/10.5194/egusphere-egu26-3805, 2026.
Understanding the water use patterns of artificially revegetated plants in arid and semi-arid desert regions with shallow groundwater is crucial for sustainable water resource management and effective vegetation restoration strategies. Despite extensive vegetation rehabilitation in China’s Mu Us Sandy Land, the interspecific and seasonal variations in plant water sources under similar groundwater conditions remain unclear. We conducted isotopic analysis of hydrogen and oxygen in main sand-fixing plants—Pinus sylvestris var. mongolica, Amygdalus pcdunculata Pall, and Artemisia desertorum Spreng—alongside potential water sources during the three growing seasons. Our aim was to elucidate seasonal changes in plant water uptake patterns by correcting isotopic offsets in xylem water using the MixSIAR model. Results indicated that A. desertorum predominantly utilized water from the 0–150 cm soil layer (67.52±14.44 %) throughout all seasons. Conversely, P. sylvestris and A. pedunculata shifted their primary water sources from the 60–240 cm soil layer during the dry season (55.20±2.12 and 57.96±1.45 %, respectively) to the 0–150 cm soil layer during the rainy season (68.44±4.46 and 66.19±1.68 %, respectively), suggesting greater water uptake adaptability in trees and shrubs compared to grasses. Groundwater contribution to plant water uptake showed no significant interspecies difference during the rainy season (P > 0.05). However, P. sylvestris and A. pedunculata significantly increased groundwater absorption during the dry season compared to the rainy season (P < 0.05). Correcting δ2H offsets in xylem water revealed an underestimation of groundwater contributions by 16.06±9.09 % in the dry season and 4.25±0.55 % in the rainy season. Given these interspecific and seasonal variations in water uptake patterns among sand-fixing plants, and the imperative for sustainable groundwater use, tailored water management strategies are essential to prevent the degradation of restored ecosystems in this water-limited desert region.
How to cite: Huang, L.: Adaptive water use strategies of artificially revegetated plants in a groundwater dependent ecosystem: Implications for sustainable ecological restoration, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4457, https://doi.org/10.5194/egusphere-egu26-4457, 2026.
The rhizosphere plays a key role in regulating plant water uptake during soil drying, yet it is often represented in soil–plant models as hydraulically and mechanically equivalent to bulk soil. While the influence of root mucilage and extracellular polymeric substances (EPS) on rhizosphere water retention is well recognized, their mechanical role—together with that of root hairs—in controlling root–soil contact and soil structural dynamics remains insufficiently explored.
Recent biomechanical insights into drying liquid bridges reveal that polymer-rich solutions behave fundamentally differently from water. Whereas capillary water bridges weaken and fail during drying—particularly in coarse-textured soils such as sand—mucilage can form viscoelastic filaments that persist during drying and generate increasing tensile forces as the polymer network is stretched. As a result, the mechanical contribution of mucilage on maintaining root-soil contact is negligible in fine-textured soils where capillary forces are already strong but is particularly relevant in sandy soils where water bridges alone provide little mechanical adhesion.
These biomechanical properties have important consequences for root–soil contact dynamics and rhizosphere structure. Elastic polymer bridges, in combination with root hairs that increase contact area and provide additional anchoring points, offer a mechanism by which plants can maintain physical contact with the surrounding soil as roots shrink during drying. This mechanical reinforcement may delay both hydraulic disconnection and associated mechanical loss of contact of roots from the soil, preserving water uptake at water potentials where capillary connectivity alone would already be limiting.
At the same time, tensile forces generated by drying polymeric gels promote aggregation of soil particles, contributing to the formation of a mechanically coherent rhizosphere with altered pore geometry and connectivity. Such aggregation reinforces the distinction between rhizosphere and bulk soil properties and may further modulate local water distribution and hydraulic conductivity near the root surface.
This perspective highlights the need to move beyond purely hydraulic descriptions of the rhizosphere and to incorporate the mechanical effects of mucilage, EPS, and root hairs into conceptual and numerical models of root water uptake, particularly under drought conditions.
How to cite: Di Bert, S. and Carminati, A.: Maintaining root–soil contact in drying soils: the role of mucilage and root hairs, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5037, https://doi.org/10.5194/egusphere-egu26-5037, 2026.
From Rhizotron Experiments to Functional–Structural Models: Quantifying Root Plasticity Under Soil Water Heterogeneity
Erfan Nouri, Xavier Draye, Mathieu Javaux
Abstract
Understanding root water uptake under heterogeneous soil moisture conditions is a central objective of this PhD, which aims to improve the mechanistic representation of root–soil interactions under climate-driven drought. Achieving this requires accurate, spatially resolved information on soil water availability at the scales experienced by individual roots rather than whole root systems. However, experimental approaches capable of quantifying soil moisture heterogeneity non-destructively and under controlled hydraulic conditions remain limited.
Within the HYDRA-MAIZE project, we developed a compartmentalized rhizotron platform designed to monitor root growth and soil moisture simultaneously under controlled soil water potential patterns. The system imposes stable, user-defined soil water potentials across
hydraulically isolated compartments while enabling optical measurements of soil moisture via light-transmission imaging.
We established a calibration framework that combines image-based light-transmission measurements with independent determination of soil water retention. Normalized light intensity is used to account for structural heterogeneity unrelated to water content, enabling
assessment of relationships between transmitted light, volumetric water content, and imposed suction. This provides a basis for evaluating theoretical and empirical formulations linking optical signals to soil moisture state.
The platform further enables quantification of spatial resolution and uncertainty in light-transmission-based water content estimation, both horizontally and vertically within rhizotron compartments. By resolving soil water availability at scales relevant to individual root segments, this setup will allow linking local and systemic morphological and hydraulic responses to soil water heterogeneity at high spatial and temporal resolution without
disturbing the plant or substrate. The platform will also support coupling rhizotron data with functional-structural plant models (FSPM) for quantitative analyses of root–soil interactions.
How to cite: Nouri, E., Draye, X., and Javaux, M.: From Rhizotron Experiments to Functional–Structural Models: Quantifying Root Plasticity Under Soil Water Heterogeneity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6379, https://doi.org/10.5194/egusphere-egu26-6379, 2026.
Cadmium (Cd), a non-essential and toxic heavy metal, severely disrupts plant physiological and biochemical processes by inducing programmed cell death (PCD). Nitric oxide (NO) and hydrogen sulfide (H₂S) are key signaling molecules involved in plant stress responses, but the molecular mechanisms underlying their crosstalk in Cd-induced PCD remain elusive. Here, we first demonstrated that Cd-triggered PCD is accompanied by NO bursts, where NO dynamically modulates PCD progression—exacerbating cell death when depleted and alleviating it when present. Proteomic analysis of S-nitrosylated proteins revealed that differential S-nitrosylation targets in Cd-induced vs. NO-alleviated PCD are enriched in carbohydrate metabolism and amino acid metabolism, with unique targets in cofactor/vitamin metabolism and lipid metabolism. Additionally, S-nitrosylation of proteins involved in porphyrin/chlorophyll metabolism and starch/sucrose metabolism contributes to Cd-induced leaf chlorosis, while in vivo S-nitrosylation of SEC23 (protein transport), ubiquitinyl hydrolase 1, and pathogenesis-related protein 1 was confirmed, with their expressions upregulated in Cd-induced PCD but downregulated by NO treatment (consistently observed in tomato seedlings with elevated S-nitrosylation levels). Building on this foundation, further investigation using GSNOR (S-nitrosoglutathione reductase, a key regulator of NO homeostasis) and LCD (L-cysteine desulfhydrase, a core enzyme for H₂S biosynthesis) knockout and overexpressing transgenic tomato (Solanum lycopersicum L.) demonstrated that both GSNOR and LCD inhibit Cd²⁺-induced PCD. GSNOR and LCD knockout plants exhibited increased Cd sensitivity and enhanced cell death compared to wild-type controls. Mechanistically, S-nitrosylation of GSNOR at Cys47 and LCD at Cys225 altered their subcellular localization, reduced their enzymatic activities, promoted Cd²⁺ uptake, and thereby accelerated PCD. Notably, S-nitrosylation attenuated the interaction between GSNOR and LCD during PCD progression. Collectively, our findings establish that NO modulates Cd-induced PCD via protein S-nitrosylation, and GSNOR-LCD interactions, together with their post-translational S-nitrosylation, constitute a critical regulatory node integrating NO and H₂S signaling in plant responses to Cd stress. These results provide novel insights into the molecular network underlying heavy metal-induced PCD and the regulatory roles of S-nitrosylation in NO-H₂S crosstalk.
How to cite: Huang, D., Chai, Q., and Liao, W.: S-Nitrosylation of GSNOR and LCD integrates NO and H2S signaling to regulate cadmium-induced programmed cell death in tomato, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7782, https://doi.org/10.5194/egusphere-egu26-7782, 2026.
Canopy water use efficiency (WUEc) is an important indicator for understanding the coupling between water and carbon processes in agroecosystems. In arid irrigation districts with shallow groundwater which is an important source of evapotranspiration (ET), previous studies have demonstrated that groundwater table depth (WTD) influences the crop water use efficiency. The dynamic response of water use efficiency at the maize canopy scale to WTD remains unclear, particularly regarding the physiological differences across growth stages, which is critical for understanding plant water-use regulation within the soil-plant-atmosphere continuum under shallow groundwater conditions. Based on eddy covariance observations from 2017 to 2019, along with ET partitioning and statistical modeling, this study systematically analyzed the variations in WUEc and its environmental drivers, with a focus on the stage-dependent responses of photosynthesis and transpiration to WTD. The results showed that average T/ET was 85.7% over the three growing seasons, while groundwater contribution to ET was 38.2%, 37.3%, and 29.9% in 2017, 2018, and 2019, corresponding to mean groundwater depths of 1.60 m, 1.76 m, and 1.81 m, respectively. Mean WUEc was 2.28 ± 0.75, 2.22 ± 1.14, and 3.43 ± 1.01 g C kg⁻¹ H₂O in the three years. The fluctuations in WTD significantly affected WUEc, especially in years with relatively low surface water input. The standardized WUEc (WUEz), which excluded the effects of crop development and atmospheric evaporative demand, decreased with deepening WTD during the vegetative growth stage but increased during the reproductive stage. This shift stemmed from the differential sensitivity of canopy photosynthesis and transpiration to WTD at each stage. During the vegetative stage, a deepening WTD caused the standardized photosynthesis (NEPz) to decline more sharply than transpiration (Tz), reducing WUEz. In contrast, during the reproductive stage, both NEPz and Tz increased in response to a deeper WTD, but the greater increase in NEPz led to an overall rise in WUEz. This study reveals a previously unreported, stage-dependent pattern in how crop water-carbon coupling responds to variations in groundwater depth. Our findings provide critical empirical evidence for refining the representation of plant water use regulation under soil water stress in ecohydrological models.
How to cite: Wu, P. and Huo, Z.: Stage-dependent response of maize canopy water use efficiency to groundwater depth: insights from ecosystem flux observations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9393, https://doi.org/10.5194/egusphere-egu26-9393, 2026.
High-Andean wetlands in northern Chile are fragile arid ecosystems that sustain biodiversity, water resources, and cultural heritage. These systems are increasingly threatened by climate change, water scarcity, and mining activities. Despite their ecological relevance, soil properties and their spatial variability in these environments remain poorly characterized. This study investigates the relationship between soil salinity and physical, chemical, and hydraulic properties in the Salar del Huasco salt flat. A combined field and laboratory approach was employed. In-situ measurements were conducted during the dry season and included soil moisture, soil temperature, electrical conductivity, and saturated hydraulic conductivity at a depth of 5 cm. Laboratory analyses compromised pH, organic matter content, cation exchange capacity, soluble cations, and aggregate stability. Field results showed that, in general, soil water content and electrical conductivity were higher in areas closer to water bodies, while soil temperature was lower. In the eastern and western zones, located very close to water bodies, soil water content reached 0.17 and 0.23 m³ m⁻³, electrical conductivity values were 1,435.05 and 1,429.42 µS cm⁻¹, and soil temperatures were 16.72 and 15.86 °C, respectively. In contrast, the northern zone exhibited lower soil water content (0.14 m³ m⁻³) and electrical conductivity (444 µS cm⁻¹). Regarding hydraulic properties, the northern zone showed the highest saturated hydraulic conductivity (0.0043 cm s⁻¹), whereas the southern zone exhibited the lowest value (0.0002 cm s⁻¹). Laboratory results indicated predominantly saline soils, characterized by a mean pH of 9.73 (± 0.59) and an average electrical conductivity of 1,167.84 (± 1,288.72) µS cm-1. Among soluble cations, sodium was the dominant species, exhibiting the highest mean concentration (330.17 ± 208.27 meq L⁻¹), followed by potassium (67.65 ± 75.30 meq L⁻¹). In contrast, calcium and magnesium showed comparatively lower mean concentrations of 19.72 ± 15.15 meq L⁻¹ and 11.15 ± 13.44 meq L⁻¹, respectively. Regarding anions, chloride and sulfate were the most abundant, with mean concentrations of 203.51 ± 169.18 meq L⁻¹ and 214.46 ± 155.65 meq L⁻¹, respectively, whereas bicarbonate concentrations were markedly lower (9.23 ± 6.15 meq L⁻¹). Aggregate stability ranged from low to moderate, with an average value of 50 ± 17 %. Marked spatial differences were observed across the salt flat. The northern zone exhibits higher aggregate stability (72%), sand content (71%). In contrast, the southern zone showed higher electrical conductivity (10,486 µS cm-1), silt content (49%), and higher concentrations of soluble calcium (37 meq/L), magnesium (35.42 meq/L), sodium (425.67 meq/L), bicarbonates (11.2 meq/L), and chlorides (356.57 meq/L). The western zone presented the highest pH (10.06), while the eastern zone displayed intermediate values for most variables. These results revealed pronounced spatial heterogeneity in soil properties within the Salar del Huasco salt flat, suggesting differentiated hydro-saline dynamics at the sub-basin scale. Accounting for this variability is essential to support conservation strategies and the sustainable management of high-Andean wetlands under increasing environmental pressure.
How to cite: Giraldo, C., Contreras, C. P., Acevedo, S. E., Leray, S., Peña, A., and Suárez, F.: Relations of salinity and soil physico-chemical and hydraulic properties in the Salar del Huasco, Chile, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14102, https://doi.org/10.5194/egusphere-egu26-14102, 2026.
The cultivation of medicinal plants focuses not only on biomass yield, but also on the health and quality of medicinal organs with therapeutic effects. Threatened by soil-borne pathogenic fungi Fusarium, the health and quality of Prince Ginseng Pseudostellaria heterophylla (P. heterophylla) is severely reduced. Plant growth-promoting rhizobacteria (PGPR), as a promising sustainable alternative, have demonstrated potential for biocontrol and soil fertilisation. However, PGPR efficacy is significantly influenced by abiotic factors, such as atmospheric CO2 concentration, which govern plant growth. To investigate the interactive effects of PGPR (Bacillus subtilis and Pseudomonas fluorescens) and CO2 levels (425 ppm and 1000 ppm) on P. heterophylla tuber health and quality, greenhouse experiments were conducted. Results show that Pseudomonas fluorescens, coupled with elevated CO2, synergistically decreases tuber disease incidence by 73% and increases the content of active ingredient polysaccharide by 253%. These improvements can be attributed to the suppressed abundance of Fusarium oxysporum and enhanced root development. Biocontrol bacteria, including Actinobacteria and Proteobacteria, are recruited, especially the genera Bradyrhizobium and Rhodanobacter. The reshaping of the rhizosphere microbiome is accompanied by the upregulation of biological pathways related to metabolite biosynthesis in the rhizosphere. Furthermore, increased indole-3-acetic acid production by PGPR under elevated CO2 signficantly promote root growth. Together, PGPR, particularly Pseudomonas, synergistically interact with elevated CO2 to enhance the health and quality of Prince Ginseng. This study sheds light on how PGPR interacts with abiotic factors influencing plant growth, providing a strategic framework for the sustainable cultivation of high-quality medicinal plants.
The authors would like to acknowledge the financial support provided by the State Key Laboratory of Climate Resilience for Coastal Cities (ITC-SKLCRCC26EG01) and the Research Grants Council of HKSAR (C5033-23G).
How to cite: Yan, W. H. and Ng, C. W. W.: Interactive Effects of Plant Growth-Promoting Rhizobacteria and CO2 levels on Prince Ginseng Health and Quality, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15862, https://doi.org/10.5194/egusphere-egu26-15862, 2026.
Pseudostellaria heterophylla (P. heterophylla) is a widely used Traditional Chinese Medicine plant for human healthcare due to the enriched bioactive compounds in its tubers. Sustained market demand has led to large-scale artificial cultivation of P. heterophylla, where soil nutrient use efficiency is one of the essential factors affecting plant growth. However, how fertiliser placements influence plant growth by altering soil water potential in the root zone remains mechanistically unclear, particularly with respect to osmotic effects. This study aims to investigate the effects of two fertiliser placements, i.e., broadcast and banded treatments, on the growth of P. heterophylla. Fertiliser-induced soil osmotic suction will be monitored, and soil nutrient use efficiency will be analysed during plant growth. By analysing soil osmotic suction and plant characteristics, this work will elucidate how fertiliser placement affects plant growth by altering soil osmotic suction in the root zone. The outcomes of this study are expected to provide practical guidance on fertiliser placements for the artificial cultivation of medicinal plants and insights into soil–plant interactions governed by soil osmotic conditions.
The authors would like to acknowledge the financial support provided by the State Key Laboratory of Climate Resilience for Coastal Cities (ITC-SKLCRCC26EG01) and the Research Grants Council of HKSAR (C5033-23G).
How to cite: Suryajaya, L. E. L., Yan, W. H., and Ng, C. W. W.: Effects of Fertiliser Placement on Soil Osmotic Suction and Growth of Pseudostellaria heterophylla, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15878, https://doi.org/10.5194/egusphere-egu26-15878, 2026.
Climate change represents a major environmental challenge that adversely affects soil hydrological regimes and water availability for plants. The increasing frequency and intensity of drought events lead to reduced soil moisture, limited infiltration, and deterioration of soil hydrophysical properties, thereby directly constraining crop growth, development, and yield potential. Insufficient soil water availability disrupts key physiological processes in plants, restricts nutrient uptake, and increases vulnerability to abiotic stress.
One promising adaptation strategy to mitigate the adverse effects of drought is the application of hydrogels in agricultural systems. Hydrogels are polymeric materials capable of absorbing and retaining large amounts of water within their structure and subsequently releasing it gradually into the surrounding soil environment. When incorporated into soil, hydrogels can improve soil water regimes and potentially enhance soil hydrophysical properties.
In this study, two soils differing in texture (sandy clay and sandy loam) and a lignin-based hydrogel at 2% application rate were investigated under laboratory conditions. Four incubation periods were established to evaluate the temporal effects of hydrogel application: 1 day, 1 month, 3 months, and 6 months. Saturated hydraulic conductivity was determined using the falling head method.
The results demonstrated that, in sandy clay soil, increasing incubation duration resulted in a statistically significant increase in saturated hydraulic conductivity, ranging from 400 to 800%. In contrast, sandy loam soil exhibited a statistically non-significant decrease (3–10%) during the initial incubation stages, followed by a statistically significant increase of approximately 60% after 6 months. These findings indicate that hydrogel incubation time in combination with soil texture is a key determinant of both the direction and magnitude of hydrogel effects on soil hydrophysical properties.
Overall, the application of lignin-based hydrogels may represent an innovative approach to enhancing agroecosystem resilience to climate change and drought, while supporting sustainable soil and water management at the landscape scale.
Keywords: hydrogel, saturated hydraulic conductivity, drought, climate change
Acknowledgement: The authors would like to thank the National Agency of Academic Exchange for the financial support (NAWA, Strategic Partnerships, BNI/PST/2023/1/00108) and the Scientific Grant Agency (VEGA 2/0065/24).
How to cite: Vitková, J., Šurda, P., S. Chandramohan, M., Grygorczuk-Płaneta, K., and Szewczuk-Karpisz, K.: Experimental Assessment of the Effects of a Lignin-Based Hydrogel on Saturated Hydraulic Conductivity in Soils with Different Textures, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16759, https://doi.org/10.5194/egusphere-egu26-16759, 2026.
Arbuscular Mycorrhizal Fungi (AMF) are plant symbionts that colonize the root cortex, but also extend their extraradical hyphal networks deep into the soil. These networks increase root-soil contact, modify soil structure and facilitate water- and nutrient transport towards the root. The fine, almost “invisible” bridges formed by these networks may gain relevance when soil becomes dry and water and nutrient resources scarce. Their pore-bridging function may connect the roots to soil patches containing water and nutrient resources, potentially preventing root shrinkage while maintaining transport.
Only recently, a high-resolution non-invasive imaging tool became available that now allows us to study the fine, delicate AMF structures in pore space in situ. Here we are presenting a workflow based on synchrotron-based X-ray computed microtomography imaging. We have developed setups to cultivate AMF at different levels of biotic complexity and subsequently image and analyze AMF hyphosphere and rhizosphere structures quantitatively and non-invasively. This approach has been successfully applied to two AMF species in contrasting soil textures, namely sand and loam. We present the 3D results of key architectural and morphological traits of AMF spores, hyphae and intraradical structures. These include structure counts, total hyphal length, branching frequency, volume, and surface area. Moreover, this study measured a set of novel parameters: (i) the AMF-soil and AMF-root interface areas, and (ii) the AMF pore space occupancy. These data can be linked to hyphal length densities measured destructively, as well as to the plant-scale data such as shoot biomass, C-, N- and P-contents in the leaves, and stomatal conductance.
How to cite: Braunmiller, H., Koebernick, N., Bitterlich, M., Jacob, E., Heck, A., Schnepf, A., Pausch, J., Jansa, J., and Ahmed, M.: Observing invisible bridges: Non-invasive imaging of arbuscular mycorrhizal fungal structures in soil pore space, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16789, https://doi.org/10.5194/egusphere-egu26-16789, 2026.
The application of hydrogels in soils is intended to enhance water-holding capacity, improve nutrient accessibility, and strengthen soil structure, thereby supporting plant growth and long-term soil sustainability. Therefore, we examined the impact of lignin-based hydrogel on the water evapotranspiration and wheat growth on four Polish soils: two forest soils (collected from Lasy Janowskie and Maziarnia) and two agricultural soil (from Grodzisko Górne and Lublin), as well as its degradation degree. Evapotranspiration measurements were conducted for 21 days, whereas wheat growth and hydrogel degradation were monitored at 1 day, 1 month, 3 months, and 6 months. Wheat growth experiment was conducted in a phytotron, under drought conditions.
Hydrogel degradation studies showed variability depending on soil type. The most pronounced increase in mass loss over time occurred in the soils collected from Lasy Janowskie and Maziarnia sites, while the soils from Grodzisko Górne and Felin-Lublin showed comparatively limited changes, indicating higher durability of hydrogel in agricultural soils. Evapotranspiration measurements showed that hydrogel reduced water loss over time in all soils. This phenomenon translated into increased height and dry mass of wheat shoots, especially in agricultural soils. For example, above-ground part of wheat grown in the soil from Felin-Lublin was 15.6 cm after incubation with hydrogel for 6 months, compared to the 10.5 cm in the not amended soil. On the other hand, a significant decrease of the height was observed for plants grown in the amended soil from Maziarnia (12.8 cm in the control, compared to 8.5 cm in amended soil).
Overall, the obtained results suggested that the lignin-based hydrogel can reduce water evapotranspiration from the soil, which in turn improves wheat growth on the selected soils types.
The research was founded by Polish National Agency for Academic Exchanges under Strategic Partnerships Program (BNI/PST/2023/1/00108).
How to cite: Szewczuk-Karpisz, K., Kukowska, S., Kyrychenko-Babko, M., and Siryk, O.: Impact of lignin-based hydrogel on wheat growth on different soil types, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16810, https://doi.org/10.5194/egusphere-egu26-16810, 2026.
In a large field trial on sandy loam, Lama et al. (2022)1- albeit involuntary - tested the effect of drought on the performance of 300 genotypes during two contrasting years: 2017 (cool and wet) and 2018 (hot and dry). Remarkably, some genotypes achieved yields under drought conditions (2018) comparable to established high-yielding varieties. The reason for this remains unclear.
One possible explanation is that this positive effect is linked to modifications of rhizosphere wettability. Sandy soils are known to be susceptible to water repellency upon drying, and several crops, such as maize, barley, and wheat, can modify soil wettability through root exudation2. However, it is still uncertain whether rhizosphere water repellency in sandy soils is an advantage, as it can delay rewetting and thereby reduce biological activity and potentially limit root water uptake.
In this study, we investigated the effect of rhizosphere-induced wettability modifications on water dynamics in naturally water-repellent sandy soil. Using time-series neutron radiography, we quantified rewetting dynamics following a dry-down experiment. While the bulk soil exhibited reduced rewetting, preferential rewetting was observed in the rhizosphere of maize. This finding may help to explain why certain plants benefit from reduced precipitation in sandy soils. Firstly, rewetting occurs preferentially in the rhizosphere, where it can directly support microbial activity and root water uptake. Secondly, localized rewetting may reduce nutrient leaching and promote nutrient retention and turnover through localized enzyme activity.
References
1. Lama, S., Vallenback, P., Hall, S. A., Kuzmenkova, M. & Kuktaite, R. Prolonged heat and drought versus cool climate on the Swedish spring wheat breeding lines: Impact on the gluten protein quality and grain microstructure. Food Energy Secur. 11, e376 (2022).
2. Naveed, M. et al. Surface tension, rheology and hydrophobicity of rhizodeposits and seed mucilage influence soil water retention and hysteresis. Plant Soil 437, 65–81 (2019).
How to cite: Benard, P., Jia, R., Di Bert, S., Wassermann, B., Bickel, S., Kaestner, A., Zang, H., and Carminati, A.: Preferential rhizosphere rewetting in water repellent sandy soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17300, https://doi.org/10.5194/egusphere-egu26-17300, 2026.
Arbuscular mycorrhizal fungi (AMF) are widespread symbiotic partners of most terrestrial plants and form close associations with their roots. While their role in enhancing nutrient uptake, particularly phosphorus, has been well studied, their effects on and of soil structure, and plant water uptake have not been investigated as broadly.
The complexity of interactions between plants, fungi, and soil under varying environmental conditions is difficult to disentangle experimentally. In-silico investigations offer an alternative means to explore these effects. We developed a 3D-model describing AMF colonization of a growing root structure and the growth of extraradical mycelium. We used the model to simulate how extraradical hyphae extend from colonized roots into the soil volume. The model is being implemented as an extension of CPlantBox, a functional-structural model for water and carbon processes at the whole-plant level.
Model parameterization is based on experimental and additional literature data. This includes information on root architecture, AMF colonization rates and locations, and nutrient transport and water flow in tomato plants and their associated hyphal networks. The plants were grown in sandy and loamy soils under both drought and well-watered conditions.
The 3D AMF colonization model explicitly represents hyphal extension rates, branching angles, and the spatial propagation of the extraradical mycelium from infection points along the root system. Key components of the model are the representation of the dynamics of root growth, growth of the intraradical and extraradical mycelium, anastomosis, and the ability of AMF hyphae to fuse and form complex networks.
The model is used to assess, visualize, and quantify how AMF networks develop, branch, and interconnect, providing mechanistic insight into their contribution to plant nutrition and drought tolerance.
How to cite: Heck, A. S., Leitner, D., Braunmiller, H. M., Pausch, J., Ahmed, M. A., Bitterlich, M., Pagel, H., and Schnepf, A.: Mathematical Modelling of the Root-Mycorrhiza-Soil System System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18106, https://doi.org/10.5194/egusphere-egu26-18106, 2026.
Rhizosphere microbiomes are known to enhance plants’ resistance to drought, and this effect has been mainly accredited to fungi and their capacity to transport and uptake water. Here, we studied how mechanical energy from motile bacteria can also contribute to water transport in soil, a mechanism we termed microbial pumps. We ran a series of microcosm and apparent surface tension experiments using different motility mutant strains of Bacillus subtilis, and characterised water transport in the pore space. Results confirmed that flagellar-based motility enhances the movements of water in soil reducing the apparent surface tension of the fluid and promotes the rewetting of dry hydrophobic regions of the soil. The effect was confirmed to be biomechanical because it was dependent on cell density and swimming speed. Collectively, these results highlight the potential of motile microorganisms to enhance water availability for crops.
How to cite: Meza-Manzaneque, B., Gomez, E., de las Heras, G., Martin Sanchez, I., Stanley Wall, N., Lindner, A., Clement, E., Elguezabal, N., and X. Dupuy, L.: Motile bacteria act as pump to move water through soil matrices, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18935, https://doi.org/10.5194/egusphere-egu26-18935, 2026.
Seed Priming with Silver Ions Decreased Cadmium Absorption by Wheat Grains via Reactive Oxygen Species Generation
Chenghao Ge1, Yixuan Wang1, Dongmei Zhou1*,
1 State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210023, P.R. China
Contact Email: gech@nju.edu.cn
Tel: 13011701863
Abstract: Cadmium (Cd) contamination in wheat grains poses a serious threat to human health, making the development of low-cost and environmentally friendly strategies to reduce Cd accumulation in wheat a critical need. In this study, we demonstrate that priming wheat seeds with silver ions (Ag⁺) leads to the in-situ formation of silver nanoparticles (AgNPs), which function as ROS-generating nanoparticles to improve tolerance to Cd stress across seed, seedling, and mature plant stages. Seeds treated with 0.11 mg L⁻¹ Ag⁺ showed the highest hydrogen peroxide (H₂O₂) levels and the lowest tissue Cd concentrations during seedling growth. The application of diphenyleneiodonium chloride (DPI) during Ag⁺ priming suppressed H₂O₂ production and resulted in increased Cd uptake in seedlings. Notably, elevated H₂O₂ levels were maintained even during the grain-filling period in Ag⁺-primed plants. Transcriptomic analysis revealed that Ag⁺ priming induces extensive transcriptional reprogramming in wheat. KEGG pathway enrichment combined with quantitative real-time PCR indicated activation of stress-signaling and metal-absorption-related pathways, including plant hormone signal transduction and the MAPK signaling pathway. Furthermore, Ag⁺ priming modulated the expression of key Cd-related genes, downregulating the Cd transporter gene TaABCB11, while upregulating vacuolar sequestration genes (TaABCC9 and TaHMA3) and the cellular Cd export gene TaTM20. These changes suggest that Ag⁺ priming triggers a ROS-mediated stress response, establishing a “stress memory” that persists throughout the growth cycle, enhances Cd tolerance, and ultimately reduces grain Cd accumulation by 39.5% in pot trials and 26.4% in field experiments.
Keywords: Seed priming, stress memory, cadmium, sustainable agriculture
Chenghao Ge, postdoctor of Nanjing University, School of the Environment. His research topics are focused on the safe production in heavy metal-contaminated farmland.
How to cite: Ge, C.: Seed Priming with Silver Ions Decreased Cadmium Absorption by Wheat Grains via Reactive Oxygen Species Generation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18957, https://doi.org/10.5194/egusphere-egu26-18957, 2026.
Soil organic matter (SOM) forms the foundation of microbial life in the soil and its processes. However, what drives the organization of organic matter turnover and microbial communities into growth remains unclear. In particular, we ask whether physical conditions in the soil—such as the quantity or quality of litter inputs—exist to which soil microbial processes adapt in order to maximize microbial growth as a proxy for power. We address this question in the frame of the German priority program 2322 by building on the maximum power principle. The principle suggests that biological systems tend to maximize the flux of energy into useful power under given constraints. We study a minimal model of SOM dynamics at steady state. In the model, litter inputs add to the organic matter pool, which is decomposed by microbial enzymes into compounds available for microbial uptake. The flux of Gibbs free energy provided with litter is used to build biomass while dissipating it during cycling, and the microbial decay returns as dead microbial biomass to the soil pool. We explore how different model structures, feedbacks, and parameterizations might lead to a maximum in the flux of free energy to microbial biomass, thereby providing insights into the conditions under which microbial growth is energetically optimized in soils.
How to cite: Chaturvedi, V., Wutzler, T., and Kleidon, A.: Do soil microbes maximize their growth?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20260, https://doi.org/10.5194/egusphere-egu26-20260, 2026.
Accurate representation of root water uptake processes is critical for simulating soil water dynamics under crop water stress, particularly when stress coincides with variable rainfall events. HYDRUS provide a useful framework for evaluating plant–soil interactions under contrasting moisture conditions by simulating different modes of root water uptake, such as compensated and non-compensated uptake.
An experimental study was conducted to examine soil–plant water dynamics under water stress occurring at different crop growth stages. The study focused on three distinct stress scenarios: (a) no water stress, (b) water stress during the vegetative phase, and (c) water stress during the flowering stage. Field measurements included soil water potential at 10 cm depth and root traits, specifically root length and root biomass, to characterize plant water availability and rooting behavior under contrasting moisture conditions.
The HYDRUS-1D model was applied to simulate soil water content dynamics using both compensated and non-compensated root water uptake formulations. Root length and biomass data were used to define root distribution functions in the model. Simulated soil water potential patterns were compared qualitatively across growth stages and root water uptake approaches. The results indicated that the compensated root water uptake model better represented soil moisture depletion and redistribution patterns under stress conditions, particularly when rainfall events occurred during flowering and grain filling stages. Overall, the study highlights the importance of incorporating compensation mechanisms in root water uptake models to improve the simulation of soil water dynamics under stage-specific crop water stress.
How to cite: Joshi, D. C., Dasgupta, P., and Das, B. S.: Simulation of Soil Moisture Dynamics Using Root Water Uptake Models under Stage-Specific Stress Conditions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21264, https://doi.org/10.5194/egusphere-egu26-21264, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot A
EGU26-17910 | Posters virtual | VPS8
Understanding the drivers of hydraulic redistribution under salt stressTue, 05 May, 14:30–14:33 (CEST) vPoster spot A
Hydraulic redistribution (HR), the passive movement of water through plant root systems from wet to dry soil layers, plays a critical role in maintaining plant water status and nutrient uptake in water-limited environments. While HR is well-documented under drought, its dynamics become significantly more complex in saline conditions where total soil water potential is driven by both matric and osmotic components.
In this study, we employed a split-root experimental design using young avocado trees to isolate and quantify HR. The root system of each tree was divided between two pots: a "wet pot" maintained at field capacity and a "drying pot" where irrigation was withheld. We utilized high-precision weighing lysimeters to monitor nocturnal weight changes in the drying pot, alongside soil moisture sensors and isotopic water labelling to track water movement.
Our preliminary results confirm the occurrence of HR in young avocado trees under non-saline control conditions. The phenomenon was clearly identified in two out of three trees monitored during the initial experimental phase, as evidenced by nocturnal increases in soil water content and corresponding weight changes in the drying pots. These findings provide a foundational baseline for the next phase of the research, which aims to evaluate how increasing levels of salt stress (NaCl) in the wet pot influence the osmotic gradients and root hydraulic conductivity that drive HR. By comparing control and saline treatments, we seek to determine whether salinity-induced changes in total water potential suppress or shift the patterns of hydraulic redistribution.
How to cite: Hochman, D. and Schwartz, N.: Understanding the drivers of hydraulic redistribution under salt stress, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17910, https://doi.org/10.5194/egusphere-egu26-17910, 2026.
