This session focuses on ecosystem responses to global change and extreme events, emphasizing the tight coupling between biogeochemical and water cycles and their effect on vegetation. Plant physiological responses to stress, such as changes in photosynthesis, transpiration, carbon allocation, and nutrient uptake, directly alter ecosystem-scale carbon, water, and nutrient fluxes and interact with soil processes by shaping soil moisture regimes, microbial activity, and the decomposition and stabilization of organic matter. Conversely, biogeochemical changes triggered by extremes include altered nutrient availability, mineral transformations, soil chemistry changes, and can have strong feedbacks on vegetation functions, recovery, and competitive interactions. Studying these interconnected processes is essential to improve mechanistic understanding of ecosystem resistance, resilience, and legacy effects following stress and disturbance in order to develop sustainable management interventions.
We welcome contributions across multiple spatial and temporal scales using laboratory experiments, field observations, remote sensing, modelling, novel analytical techniques, data synthesis, and/or presenting innovative management strategies. The session aims to foster interdisciplinary discussion at the interface of vegetation functioning, soil processes, and biogeochemical cycling, to advance understanding of ecosystem responses in a rapidly changing world.
Invited Speakers: Jordi Martínez-Vilalta, Marco Keiluweit
Orals: Wed, 6 May, 08:30–10:15 | Room 2.23
Hotter and drier conditions under ongoing climate change are altering forest dynamics worldwide, frequently inducing events of forest mortality. These mortality events have profound implications for the carbon and water balances of ecosystems, from the plot to the global scale. However, their prediction remains a substantial research challenge, even if the mechanisms involved are relatively well understood. I will discuss this apparent paradox highlighting the limitations of current approaches, which rely almost exclusively on the use of traits and process-based modelling. These are powerful approaches but also face important challenges due to the scale- and context-dependency of trait effects on individual performance and vegetation dynamics. I will argue that better predictions require multi-scale approaches that complement the essentially reductionistic view based on traits with systems thinking. Current developments of forest monitoring schemes through continuous, on-site measurements and enhanced remote sensing tools provide excellent opportunities to reconcile our detailed mechanistic understanding at fine scales (e.g., ecophysiology) with patterns and processes at coarser scales.
How to cite: Martínez-Vilalta, J.: Predicting drought-induced impacts on forests: mechanisms, challenges and novel approaches, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1826, https://doi.org/10.5194/egusphere-egu26-1826, 2026.
Sustainable cocoa production underpins rural livelihoods across the tropics and offers significant potential for both climate change adaptation and mitigation. Although the biodiversity value of cocoa agroforestry systems is well documented, their functional capacity to buffer drought stress and enhance climate resilience remains insufficiently understood. In particular, scalable methods for monitoring plant physiological responses to water stress across structurally heterogeneous agroforestry landscapes are urgently needed. In this study, we assess the potential of multispectral drone imagery to detect drought-related physiological dynamics in cocoa agroforestry systems, with a specific emphasis on the role of shade tree leaf phenology.
We integrated high-resolution multispectral drone imagery with in situ physiological measurements across ten smallholder cocoa plantations of comparable age in the northern cocoa belt of Ghana. Thirteen shade tree species, representing distinct functional groups based on leaf phenology, were selected. For eight individuals per species, we quantified structural traits (diameter at breast height, tree height, and canopy area) and phenological status, and measured leaf-level transpiration and stomatal conductance using a LI-600 porometer. Multispectral imagery acquired during the late wet, mid-wet, and peak dry seasons between 2021 and 2023 was used to derive the Green Normalized Difference Vegetation Index (GNDVI), a spectral proxy sensitive to chlorophyll content and photosynthetic activity. We observed pronounced seasonal and functional-group-specific differences in canopy reflectance, with significant interactions between season and shade tree phenology. GNDVI was strongly correlated with key physiological traits, particularly stomatal conductance, and exhibited consistent responses to seasonal climatic variation. These results demonstrate that drought-induced physiological stress, expressed as reductions in stomatal conductance, can be reliably predicted from spectral traits derived from high-resolution multispectral drone imagery, highlighting its potential as a scalable tool for assessing drought resilience in cocoa agroforestry systems.
How to cite: Abdulai, I., Grünther, N. P. K., Asare, R., Habib-ur-Rahman, M., Rötter, R. P., and Hoffmann, M.: Linking Canopy Phenology to Drought-Induced Physiological Stress in Cocoa Agroforestry Systems Using Multispectral Drones, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21306, https://doi.org/10.5194/egusphere-egu26-21306, 2026.
Long-term fertilization alters plant traits and is widely thought to reduce grassland drought resilience. While these effects are often attributed to species turnover, trait responses can also arise within species, through phenotypic plasticity and evolutionary divergence among populations. However, whether intraspecific evolutionary changes in response to long-term fertilization alter ecosystem responses to drought remains poorly understood. Here, using the >100-year Park Grass Experiment (UK), we tested whether long-term fertilization has led to heritable trait divergence and altered drought resilience in a dominant grass species. We collected 20 genotypes of Anthoxanthum odoratum from each of two fertilized plots and control plots and grew them under common garden conditions to isolate genetic differentiation from phenotypic plasticity in plant traits. Plants were then subjected to a two-week simulated drought followed by two weeks of recovery, during which CO2 fluxes were measured. We found that genotypes originating from fertilized plots showed higher vegetative and reproductive height compared to those from control plots, indicating heritable divergence after a century of nutrient enrichment. Nevertheless, drought resilience of CO2 fluxes, including drought resistance and recovery, did not differ among genotypes from different plots. Across all genotypes, drought recovery was positively associated with shoot biomass, root tissue density, and root diameter, but negatively associated with reproductive height. Our findings reveal that long-term fertilization can drive evolutionary shifts in plant height-related traits without affecting intrinsic drought resilience, highlighting a decoupling between evolutionary responses to nutrient enrichment and functional responses to climate extremes. This underscores the need to integrate eco-evolutionary processes into predictions of ecosystem responses to global change.
How to cite: Jing, Y., Davison, J., and Semchenko, M.: Long-term fertilization drives genetic trait differentiation without changing intrinsic drought resilience in grassland populations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14405, https://doi.org/10.5194/egusphere-egu26-14405, 2026.
Pathogens, insects, and parasites (PIPs) are a common disturbance in many forest ecosystems that lead to reduced tree growth and increased mortality over time. While native PIPs can be key to maintaining biodiversity, PIP outbreaks are becoming more common and devastating to forests in a changing climate. Outbreaks of invasive PIPs pose a particular risk as host trees may have no evolved defences. Process based models are ideal for studying and predicting forest responses to disturbance as they can be used to test hypotheses about processes, test conditions that are challenging to experimentally create, and can inform further experimentation. PIPs have been incorporated in some forest ecosystem models to determine the effects of a PIP on tree growth and mortality. However, the host response to PIPs, including defences that lead to resistance or tolerance of a particular pest, have not been represented in process-based models, despite their demonstrated role in determining the resulting severity of PIP impacts on tree growth and mortality. Modelling both sides of the host-PIP interaction will provide more accurate forecasts of tree mortality and growth in the face of disturbance and allow us to test hypotheses about host defence processes and tolerance to disease. We develop a process-based model to quantify the impacts of pathogen infection on tree growth and function, while incorporating host defence and tolerance mechanisms, to simulate the effects of the widespread invasive pathogen, Hymenoscyphus fraxineus, on ash (Fraxineus excelsior) across Europe. H. fraxineus, is the causal agent of ash dieback disease that has led to the steep decline of native ash trees in Ireland, UK and Europe, killing up to 85% of trees in some areas. A small percentage of trees are genetically tolerant to the disease, but tolerance levels are variable and environmental conditions, tree age, and pathogen load may all further influence the level of susceptibility. Combining the model with ash tree trial data, we show that disease tolerance has a genetic component, but even among genetically tolerant trees, high disease pressure in wet environments may outweigh genetic tolerance. Further the effects of the environment and site characteristics on disease severity are mediated primarily through effects on pathogen abundance rather than tree growth. In addition to providing insights into drivers of ash dieback tolerance, our study showcases the power of process-based models combined with field trial and genetic data to reveal aspects of plant function that cannot be inferred from data alone.
How to cite: Watkins, C., Rathore, D., Huang, J., Pimenta, R., Fuchs, S., and Caldararu, S.: Interactions between genetics and the environment determine tolerance to ash dieback disease in an ecosystem model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10605, https://doi.org/10.5194/egusphere-egu26-10605, 2026.
Combining carbon flux measurements with tree above- and belowground phenology enables a holistic assessment of plant functioning and ecosystem carbon balance under future climatic conditions. The stress caused by rising air temperature and drought affecting the asynchrony in trees above- and belowground phenology might cost more than the carbon gains, weakening future forest carbon sinks.
Norway spruce seedlings were grown in organic soils (drained Histosol) in climate chamber separately in transparent boxes for 13 weeks in 2023. Ten trees were grown under ambient conditions based on June-July 2021 data, which reflects long term average weather conditions in the Estonian forest. Another ten under low air relative humidity (-10% of ambient) and ten under high temperature (+6°C) treatment, whereas both treatments are equivalent to +30% increase in water vapor deficit. The treatment period lasted for 30 days, whereas half of the trees had 65% of soil moisture from field capacity and other half experienced drought (45%). The recovery period with ambient conditions lasted for 20 days. The ecosystem gas exchange (NEE, Rs) was measured in four key time points during the experiment; photosynthesis, other physiological parameters, shoot length and fine root area was measured weekly. Destructive measurements such as biomass and fine root carbon exudation was measured at the end of the experiment.
Elevated air temperature caused a stronger carbon sink, although there was an increase in soil respiration. However, in the recovery phase the ecosystem-level gas exchange decreased and reached the same level as the ambient condition indicating that some of the physiological changes were strongly tied to the changes in temperature conditions. Soil moisture was a critical constraint to reduced photosynthesis and diminished root relative growth rate highlighting water limitation as a dominant stressor for both carbon assimilation and belowground development. Interestingly, low humidity showed positive effects on fine root growth compared to elevated temperature (but only under 65% of soil moisture), perhaps indicating a compensatory carbon allocation to belowground biomass, which enhances water uptake under drier climate. Meanwhile the aboveground growth increased significantly only under high temperature. Other parameters, including fine root carbon exudation, will be discussed in the context of tree ecosystem carbon flux.
How to cite: Sell, M., Kupper, P., Klaus, M., Kull, A., Sultonova, A., Rohula-Okunev, G., Kukumägi, M., and Ostonen, I.: Linking tree physiology, carbon fluxes, and root growth dynamics under constraining soil water and atmospheric treatments , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19783, https://doi.org/10.5194/egusphere-egu26-19783, 2026.
Climate change is intensifying environmental extremes, subjecting soil ecosystems to unprecedented and overlapping stressors. Yet the impact of such stressors on the mechanisms that protect soil carbon—the largest terrestrial carbon reservoir—remains poorly understood. In this presentation, I will explore how climatic extremes and their associated stressors impact carbon protection mechanisms in soils. Drawing on evidence from controlled model systems, climate manipulation experiments, and field studies, I will highlight how key stressors—including water and nutrient limitation, viral infection, and oxidative stress—alter the effectiveness of multiple carbon protection mechanisms. Together, our results highlight the immediate response of otherwise “protected” soil carbon to environmental stressors, underscoring the soil carbon persistence is not fixed, but dynamically regulated by environmental conditions. I will conclude by discussing the implications of these findings for predicting short- and long-term soil carbon dynamics in a rapidly changing climate.
How to cite: Keiluweit, M.: Feeling Stressed? How Soil Carbon Protection Mechanisms Respond to Climate Extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18219, https://doi.org/10.5194/egusphere-egu26-18219, 2026.
Extreme weather events, such as heatwaves, can disrupt biogeochemical cycling at a regional and global scale, leading to devastating environmental and socioeconomic impacts across the agrifood system. Previous studies exploring extreme heat-stress events rarely exceed 35 °C or have replicated global surface air temperature models where soils are subjected to mean annual temperature (MAT) ± 1.5 to 5 °C. However, this overlooks the rapid, short-term temperature extremes where soil surfaces heated by solar irradiation can reach >40 °C, exceeding the microbial thermal optima.
This study replicated heatwave conditions recorded in July 2025 in North Wales, UK, where bare, unshaded soil surface temperature reached up to 59.7 °C. Using 14C-radioisotope tracing, we explored the impact of varying duration (15-minutes to 7-days) of extreme heat-stress and thermal diffusion within the upper soil profile (0-5 cm) on microbial carbon (C) cycling, carbon use efficiency (CUE), and biogeochemistry.
We found that 14C-glucose mineralisation rapidly increased 1.5- to 2-fold from 37 ± 1 % in the control (20 °C) to 44-77 % in soils subjected to 59.7 °C for >1-hour, with a noticeable lag-phase in C cycling occurring in the first 8-hours following 14C-glucose addition. This subsequently reduced microbial CUE at a rate of 0.01 units min-1 from 0.62 ± 0.01 (control) to 0.19 ± 0.01 after 2-hours exposure to extreme heat, after which no further decline occurred. Soil pH and extractable ammonium increased with heat exposure due to nitrification inhibition, with microbial biomass C decreasing stepwise (from 2.36 ± 0.15 to 0.63 ± 0.06 g C kg-1) with increasing heat-stress duration. Notably, after a 14-day recovery period these trends still occurred, indicating that the critical temporal threshold reached (>1-hour) has a legacy effect on microbial activity and soil nutrient cycling, with implications for soil C sequestration.
How to cite: Cooledge, E. C., Davis, C. J., Chadwick, D. R., and Jones, D. L.: Extreme heat-stress events rapidly alter soil microbial carbon use efficiency and nutrient cycling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11208, https://doi.org/10.5194/egusphere-egu26-11208, 2026.
The Arctic is warming faster than the rest of the globe, leading to intense disturbances including permafrost thaw, thermokarst development, and wildfire. These disturbances alter rates of biogeochemical cycling of nitrogen (N) and phosphorus (P), further altering the ecology and permafrost dynamics of the region. My goal is to understand the effects of wildfires on soils and plants in the western Canadian Arctic tundra. Ash is high in available nutrients which promote plant growth immediately after fire, but may increase N and P loss after fire. In tundra ecosystems, nitrate and ammonium concentrations are particularly low, meaning that an increase in concentrations of these nutrients after a wildfire can have a particularly large effect on biological activity. Not all plant species are equally able to take advantage of the pulse of nutrients available after a wildfire; some will have an advantage over others. Large woody shrubs can outcompete smaller evergreen shrubs, lichens, and mosses during the recovery period, which increases the amount of above-ground biomass and thus the risk of future wildfires. This may result in a positive feedback loop where wildfire increases shrub growth and shrub growth increases wildfire risk, leading to major changes in plant species and biogeochemical cycles in the ecosystem. I examine whether wildfire can be a realistic mechanism for providing the nutrients necessary for shrub growth, leading to permanent changes in the tundra ecosystem.
To study the effects of fire on plants and soil nutrients, I collected soil and vegetation samples from five burned sites and one unburned control site near Inuvik, Northwest Territories, during the summer of 2024. Tunda fires occurred in 1968, 1983, 2003, 2012, and 2023. In the field, I measured the active layer depth, soil temperature, soil moisture, and plant community composition. In the laboratory, I measured available phosphate, nitrate, and ammonium concentrations in soils through wet chemical extraction, measured heavy metal concentrations using X-ray fluorescence (XRF), measured microbial phosphate concentrations, performed sequential phosphate fractionation to measure a gradient of phosphorus availability, and measured basic soil parameters such as soil texture, gravimetric soil moisture, soil organic carbon content, and soil pH.
This work is necessary to understand the future of tundra ecosystems in a changing climate. At present, carbon emissions due to permafrost thaw and potential carbon uptake by increased plant growth in the tundra are poorly understood and must be quantified if we are to understand the carbon budget of the circumpolar Arctic-boreal region. As such, my work will inform terrestrial biosphere models. Of greater local importance is the future of culturally relevant tundra plant species and the future of ecosystem services that determine the identity and livelihoods of local communities.
How to cite: Jones, C., Cornette, L., Sonnentag, O., and von Sperber, C.: Effects of Wildfire on Nitrogen and Phosphorus Availability in Arctic Tundra Soils, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14803, https://doi.org/10.5194/egusphere-egu26-14803, 2026.
Soil nitrogen (N) cycling and nitrous oxide (N2O) production and consumption dynamics have received relatively little attention in Arctic biogeochemistry, largely because of the classical understanding of general N limitation and negligible N gas losses. Now, this understanding is becoming outdated by recent studies, which have revealed active N cycling in permafrost-affected soils by looking into processes and habitats previously ignored and possibly also because of actual intensification of soil N cycling with warming and permafrost thaw. Since enhanced N availability versus N limitation is of crucial importance for future carbon balance and ecosystem-climate feedback in the rapidly warming Arctic, there is a dire need for more information on N cycling in permafrost soils. Soil incubations can be used to study N turnover rates in controlled conditions and to tease apart various processes, but they need to be well designed to realistically represent the soil N cycle in its full complexity.
Here, we summarize our experience from N cycling studies by soil incubations over the years, with an emphasis on the ongoing Thaw-N project which investigates the fate of permafrost N following thaw. We give our suggestions for the balancing act between simple experiments that can be easily conducted over large numbers of samples to improve spatial representativeness, and detailed experiments with advanced methods to uncover the actual rates of individual processes and link them with microbial activities. . Our experience highlights the role of microbial versus substrate limitation in shaping the soil N cycle as time passes following disturbances, such as permafrost thaw. We also discuss the special challenges of studying N2O production in comparison to the other, more commonly studied greenhouse gases carbon dioxide and methane.
How to cite: Marushchak, M. E., Hashmi, W., Martínez-Risco Martínez, P., Palacin-Lizarbe, C., Paul, D., Kohl, L., and Gil, J.: Effective soil incubations for studying nitrogen cycling in permafrost soils — practical and ecological considerations, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15828, https://doi.org/10.5194/egusphere-egu26-15828, 2026.
Pedogenesis is the complex interplay of biogeophyical and biogeochemical mechanisms operating simultaneously. Resolving the interactions and feedbacks requires experimental and analytical approaches that provide and integrate multiple, highly resolved signals into a coherent process-based framework (Totsche et al. 2024). Here, we investigate the response of loess-derived Regosol and Luvisol topsoils to controlled hydraulic and chemical stress using water-unsaturated column experiments conducted over seven months. Effluent, including pH, electrical conductivity (EC), major ions and elements, inorganic carbon, particle concentrations, and organic matter (OM) quality and quantity, was monitored with high frequency.
To evaluate parameter interdependence and their joint response to forced perturbations, we applied a multivariate decomposition. Our analysis yielded distinct “effluent patterns” that represent recurring combinations of physicochemical parameters that evolve coherently over time. These patterns reflect the interplay among multiple processes, including solute release, particle mobilization, and OM transport, rather than isolated parameter responses.
The effluent course of both soils was dominated by four patterns, which together explained approximately 90% of the total variance. Pattern one reflects EC-driven transport and tracer-induced cation exchange, integrating conservative solute movement with the release of exchangeable mono- and polyvalent cations. Pattern two combines particle export with the mobilization of aluminum, iron, and phosphorus and fluorescence signatures of recalcitrant OM, indicating the destabilization and transport of organo-mineral associations (Lehmann et al., 2021). Pattern three is dominated by inorganic carbon dynamics and alkaline earth cations, revealing carbonate dissolution and diffusion-controlled release processes, following hydraulic stress. The fourth pattern is linked to the reversible exchange of surface-associated OM, coupled to the dynamics of monovalent cations, and the re-establishment of cation bridging after chemical perturbation (see Ritschel et al., 2023).
Clear differences in pattern expression were observed between soil types. Regosol responded to chemical stress primarily through carbonate dissolution and cation exchange, thereby buffering ionic strength gradients and limiting particle mobilization. In contrast, the Luvisol exhibited pronounced disaggregation and enhanced particle and hydrophobic, pedogenic OM export under electrolyte shifts, reflecting advanced pedogenic development and reduced stress resistance.
By capturing these contrasting responses to the forced stresses, we demonstrate how soil development governs the susceptibility of soils to environmental perturbations and, consequently, the (im-)mobilization pathways of particles, ions, and OM. The study addresses challenges associated with fluctuations in salinity, wetting and drying cycles, and the extensive use of liquid mineral fertilizers, as well as their effects on soil aggregation, organic matter dynamics, and nutrient availability. Together, these findings provide the basis for a conceptual framework for enhancing soil resilience in vulnerable agroecosystems under changing climate/environmental conditions.
Lehmann, K., Lehmann, R., Totsche, K. U. (2021) Event-driven dynamics of the total mobile inventory in undisturbed soil account for significant fluxes of particulate organic carbon. Sci. Total Environ. 756, 143774, doi: 10.1016/j.scitotenv.2020.143774
Totsche, K.U., Ray, N. and Kögel-Knabner, I. (2024), Structure–function co-evolution during pedogenesis—Microaggregate development and turnover in soils. J. Plant Nutr. Soil Sci., 187: 5-16. https://doi.org/10.1002/jpln.202400012
Ritschel, T., Aehnelt, M., Totsche, K.U., (2023). Organic matter governs weathering rates and microstructure evolution during early pedogenesis. Geoderma 429, 116269, https://doi.org/10.1016/j.geoderma.2022.116269
How to cite: Totsche, K. U., Guhra, T., Ritschel, T., van Overloop, L. F., and Siebers, N.: Loess-derived soils under stress: Lessons learned from pedogenic response patterns, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21836, https://doi.org/10.5194/egusphere-egu26-21836, 2026.
Posters on site: Wed, 6 May, 10:45–12:30 | Hall X1
Fires are a common and probably the most pervasive disturbance to many terrestrial vegetated ecosystems. By burning a great portion of aboveground biomass and producing gases, aerosols, and solid residues deposited on the ground surface, as well as changing other ecosystem properties, fires not only immediately transform aboveground pools of ecologically important elements but, more importantly, has a lasting impact on their post-fire cycling. In this work, we focus on the immediate changes of fire to the chemistry of manganese (Mn) and evaluate the effects of vegetation-fire interactions. Leveraging field and laboratory studies, we characterized the chemical speciation and reactivity of Mn in ash samples and revealed the effects of vegetation and fire thermal conditions. Combined with ecosystem-dependent fire behaviors, the results were extrapolated to reveal the differential impacts of fires, in terms of immediate changes to and long-term effects on Mn cycling.
How to cite: Huang, R., Mariano, S., D. Birch, J., Miesel, J., Sánchez-García, C., Santin, C., and Neris, J.: Fire disturbances to manganese cycling in the plant-soil continuum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-45, https://doi.org/10.5194/egusphere-egu26-45, 2026.
Understanding how ecosystems function under frequent climatic disturbances is crucial for predicting their long-term stability. Although previous research indicates that stable ecosystems can mitigate the impacts of climate extremes, there remains debate over whether this stability is primarily driven by resistance, resilience, or a combination of both. In this study, we analyzed annual net primary productivity (NPP) in relation to the Standardized Precipitation Evapotranspiration Index (SPEI) and the aridity index (AI) to examine: (i) the spatiotemporal variations in NPP, (ii) the correlations between NPP, SPEI, and AI, and (iii) the resistance and resilience of four grassland types—meadow steppe, typical steppe, desert steppe, and steppe desert—across Inner Mongolia during the period 2000–2019. Despite noticeable interannual fluctuations, all grassland types exhibited an overall increase in NPP, with rates ranging from 1.21 g C m⁻² yr⁻¹ in desert steppe to 4.54 g C m⁻² yr⁻¹ in meadow steppe. Meadow steppe recorded the highest average NPP (251 g C m⁻²), followed by typical steppe (160 g C m⁻²), steppe desert (95 g C m⁻²), and desert steppe (83 g C m⁻²). NPP was significantly correlated with increasing SPEI values across all grasslands, and with higher AI values in steppe desert and desert steppe. Species richness varied from 9–14 in meadow steppe, 7–17 in typical steppe, and 5–10 in steppe desert, with NPP rising with greater species diversity—indicating a positive biodiversity–productivity relationship. Vegetation showed lower resistance but higher resilience under dry conditions, and the opposite under wet conditions, across most grasslands except desert steppe. Although typical steppe, meadow steppe, and steppe desert were more vulnerable to extreme droughts due to low resistance, their strong resilience suggests a quicker recovery following dry periods compared to wet conditions. The identified positive relationship between biodiversity and productivity suggests that preserving higher species richness may help mitigate productivity declines during climatic extremes.
How to cite: Hossain, Md. L. and Lai, D. Y. F.: Ecosystem stability and productivity dynamics of Inner Mongolian grasslands under climate extremes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-119, https://doi.org/10.5194/egusphere-egu26-119, 2026.
The area burned by high severity wildfire is increasing in many regions on the planet as a product of fuel accumulation, fire suppression, and climate change. As more forested land is impacted by high severity wildfires, there is greater potential for short-interval reburns, where the same area is burned by two or more wildfires within 20 years. Though reburn effects on vegetation are gaining significant research attention, it remains unclear how soil biogeochemical processes will respond to short-interval reburns. Studies in some forests have shown that short-interval reburns drive compounding losses of soil carbon (C) and nitrogen (N), but results vary based on ecosystem type, age, and fire dynamics. A key uncertainty is how reburn history influences dissolved organic carbon (DOC) quantity and composition and microbial respiration, which together influence C processing and organic matter (OM) cycling in soils.
To address this knowledge gap, we quantified differences in soil biogeochemistry across soils from forest stands that experienced zero, one (in 2023), or three (in 2003, 2017, and 2023) wildfires within a 20-year period, and classified those stands as unburned, long-interval reburn, and short-interval reburn, respectively. These fires occurred in the Pacific Northwest, USA, in wet conifer forests with higher productivity than most previously studied reburns. We collected five replicate soil samples from 0–5 cm mineral soil depths and quantified microbial biomass C and N, soil organic C and N, and OM concentrations, pH, and DOC and total dissolved N concentrations. Additionally, we carried out a 35-day lab incubation to quantify microbial CO2 respiration and net inorganic N fluxes. Finally, we characterized the chemical quality of DOC using excitation-emission indices and parallel factor analysis.
While wildfire decreased soil C and microbial biomass C and N in both short-interval and long-interval reburns, we observed no effect of fire nor short-interval reburn on soil N, pH, or OM. However, soil from short-interval reburn sites had lower DOC concentrations (F2,12 = 14.5, p < 0.001) and CO2 fluxes (F2,10 = 26.6, p < 0.001) than both long-interval reburn and unburned stands. Chemical quality analyses indicated that “fresh” DOC comprised a larger proportion of overall DOC contents after short-interval reburn (F2,10 = 4.2, p = 0.048) compared to long-interval reburn, with similar “freshness” between unburned and short-interval reburn soils.
Taken together, our preliminary results suggest that the short-interval reburn soils exhibited lower DOC concentrations and suppressed microbial respiration. Interestingly, these lower CO2 fluxes were not fully explained by microbial biomass C and N, which appeared to be buffered, possibly due to less fuel consumption during the third fire. Instead, we hypothesize that reduced DOC quantity, rather than DOC composition (“freshness”), was the primary constraint on microbial processing under our experimental conditions. As such, carbon quantity appears to exert stronger control than DOC composition. These results suggest that slower decomposition may facilitate soil C retention following short-interval reburns. Our findings have implications for soil recovery trajectories, as decreased microbial processing may contribute to rebuilding soil OM over time after short-interval reburns.
How to cite: McCool, K., Fate, B., Seyfried, G., Perakis, S., and Bladon, K.: Soil microbial and organic matter responses to short-interval reburns in the Pacific Northwest, USA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8089, https://doi.org/10.5194/egusphere-egu26-8089, 2026.
The global atmospheric CO₂ concentration and the surface temperature keep rising since the industrial era. This ongoing change profoundly affects crop photosynthesis and yield formation. Therefore, accurately and timely monitoring the combined effects of elevated CO₂ (eCO₂) and warming on crop production is of great scientific and practical importance. In recent years, the development of continuous spectral observation technology, which captures a range of vegetation indices (VIs) and the solar-induced chlorophyll fluorescence (SIF) signal, has provided a new approach for vegetation dynamic monitoring. However, the responses and underlying mechanisms of SIF and various vegetation indices to the interactive effects of eCO₂ and warming remain unclear.
This study investigates the responses of two rice cultivars, Ningxianggeng (NXG) and Yongyou (YY), to elevated CO₂ (C⁺) and warming (T⁺), both individually and in combination, using a T‑FACE system in Nanjing, Jiangsu Province. The experiment included four treatments: ambient control (CT), elevated CO₂ (C⁺T), warming (CT⁺), and combined elevated CO₂ and warming (C⁺T⁺). Continuous canopy spectral observations, covering both full‑range (400–1000 nm) and hyperspectral (650–800 nm) measurements, were integrated with key physiological parameters such as net photosynthetic rate (Aₙ), biomass, and yield.
SIF proved to be a more sensitive and earlier indicator of photosynthetic dynamics than VIs. Under elevated CO₂ alone (C⁺T), SIF increased in both cultivars, reflecting a clear CO₂ fertilization effect. The interaction with warming (C⁺T⁺), however, revealed a diurnal dual effect: SIF was higher in C⁺T⁺ than in C⁺T during the morning, but slightly lower in the afternoon, indicating the complex effects of temperature on modulating photosynthetic activity. YY generally exhibited higher photosynthetic capacity than NXG across treatments, with a marked afternoon enhancement (up to 40%) under C⁺T⁺ during certain growth stages, though this advantage varied seasonally. In contrast, NXG showed a stronger positive response in photosynthetic efficiency under the combined C⁺T⁺ treatment. The Photochemical Reflectance Index (PRI) indicated that light‑use efficiency (LUE) declined at midday during periods of sustained high temperatures (mid‑July to early August), particularly for NXG under C⁺T, while YY under C⁺T⁺ maintained relatively higher LUE, suggesting a greater warming tolerance in YY.
The approach by integrating SIF with multiple VIs may provide a robust methodology for rapid, non‑invasive assessment of cultivar‑specific climate adaptability, offering valuable insights for precision agriculture management and climate‑resilient breeding strategies that deserve further investigation.
How to cite: Zhang, Q., Cai, C., Wang, X., Wang, Z., and Song, L.: Continuous monitoring of rice responses to elevated temperature and CO2 in a T-FACE experiment using tower-based hyperspectral observation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8617, https://doi.org/10.5194/egusphere-egu26-8617, 2026.
Radiocarbon measurements indicate that nonstructural carbohydrates (NSCs) in trees can be decades old. The NSCs can be critical resource during ecological disturbances that impede carbon assimilation, however, it is unclear to what degree old NSCs are accessible to tree metabolism and growth, or how their allocation and use differ between above- and belowground. To address these knowledge gaps, we girdled the stems of 60–70-year-old aspen trees, a species which can grow in clones and establish root connections with neighboring trees. During the first years after girdling (2018–2021), the girdled tree stems contained six times less NSC than the controls, respired at a rate five times slower, and increasingly used older carbon for respiration, reaching 10 years old by 2021 (Helm et al., 2024). Although most root sampling took place later, during 2021–2023, the roots’ response to the girdling was much milder. In cross sections of roots > 10 cm in diameter in 2022, the girdled trees had two to three times less NSC and NSC that was 8–14 years older than the controls. Individual NSCs showed inverted trends along the annual rings: the oldest sugars (as estimated by water-soluble carbon) were found in the bark and outer rings, whereas the oldest starch was found in the interior rings. Some rings contained NSCs aged 20–30 years. In fine roots (less than 2 mm in diameter), compared to the controls, the girdled trees contained half of the NSC, respired 30% slower while emitting 1–5 years older CO₂, and contained 1–6 years older NSC. In contrast to these relatively young ages, fine roots collected from screens buried in the soil for up to one year – probably representing growth from spring and early summer – had radiocarbon ages of 16–33 years with no clear effect of girdling. Overall, the NSC pools in the tree stems depleted faster than those in the large coarse and fine roots, suggesting either that the root NSCs were replenished by carbon from neighboring trees or that the tree stems play a more significant role in storage at the tree level. The extremely old radiocarbon ages of new fine roots suggest that old reserves in large roots are accessible and have a physiological function, even in undisturbed trees.
Helm, J., Muhr, J., Hilman, B., Kahmen, A., Schulze, E. D., Trumbore, S., Herrera-Ramirez, D., & Hartmann, H. (2024). Carbon dynamics in long-term starving poplar trees-the importance of older carbohydrates and a shift to lipids during survival. Tree Physiol, 44(13), 173-185. https://doi.org/10.1093/treephys/tpad135
How to cite: Hilman, B., Helm, J., Schulze, E.-D., Varga, T., Muhr, J., Hartmann, H., and Trumbore, S.: Differences in nonstructural carbohydrates use and radiocarbon ages between fine roots, coarse roots, and stems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10342, https://doi.org/10.5194/egusphere-egu26-10342, 2026.
Alpine shrublines are assumed to be highly sensitive to climate change and play a vital role in maintaining biodiversity and ecosystem functions. However, where and how alpine shrublines are distributed is poorly understood due to the difficulty in distinguishing between dwarf shrubs and grass. In this study, we proposed a novel framework to map alpine shrublines in Xizang Rezhen National Forest Park in 2020 using multi-source spatial data, probabilistic vegetation mapping, and seed-filling algorithm. Validation against high-resolution Google Earth imagery demonstrated a high accuracy, with a mean absolute error (MAE) of 3.13 m and R² of 0.99. The results indicated that the average elevation of alpine shrublines was about 4,873 m, ranging from 4,518 m to 5,195 m. South-facing alpine shrublines averaged approximately 145 m higher than north-facing counterparts. Meanwhile, shrublines at higher elevations exhibited lower EVI2 and NDVI values along with reduced soil quality compared to those at lower elevations. This study reveals geographical influencing factors of alpine shrubline patterns, thus offering insights into the ecological responses of high-altitude woody ecosystems to climate change.
How to cite: Ren, Z., Zhang, L., Wang, Q., Hu, W., and Shi, Z.: A novel framework for assessing shrublines and their geophysical constraints in alpine regions through probabilistic vegetation mapping and seed-filling algorithm, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10840, https://doi.org/10.5194/egusphere-egu26-10840, 2026.
Drought- and heat-induced tree mortality has been increasingly observed and is expected to intensify under ongoing climate change, raising urgent concerns about forest vulnerability across Europe. Identifying the forest ecosystems most susceptible to climate extremes and understanding the mechanisms underlying their responses are therefore critical. Here, we integrate multiple hydrological and satellite-based proxies of large-scale forest growth with long-term ground-based forest monitoring data across Switzerland. From 2000 to 2024, hydrological stress, quantified by the Standardized Precipitation Evapotranspiration Index (SPEI), has increased consistently across the country. In contrast, vegetation structure (represented by Normalized Difference Vegetation Index, NDVI) and carbon uptake (represented by gross primary productivity, GPP) exhibit coherent but spatially contrasting trends, with pronounced declines in northwestern regions and increasing trends in the southeastern Alpine areas. Ground-based observations corroborate these patterns, showing higher crown defoliation rates, stronger declines in net primary productivity, and reduced tree growth in areas characterized by decreasing NDVI and GPP, while tree mortality rates remain comparable across regions. Species-specific responses were also evident, with European beech exhibiting increasing growth trends, whereas other dominant Swiss tree species show overall growth declines in recent decades. By jointly analyzing these patterns with environmental drivers, including meteorological factors and soil conditions, we aim to identify the dominant forcing mechanisms driving forest growth stress and to develop models for predicting forest GPP in Switzerland. We further quantify how interacting environmental stressors, such as vapor pressure deficit and soil water availability, jointly regulate forest productivity dynamics, providing an integrated assessment of forest vulnerability to climate extremes.
How to cite: Luo, Y. and Gessler, A.: Integrating ground observations and remote sensing to assess Swiss forest growth over the past 25 years, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11799, https://doi.org/10.5194/egusphere-egu26-11799, 2026.
Phenotypic plasticity is essential for plant adaptation to environmental change and competition, yet the mechanisms that constrain or enhance it remain unclear. In alpine tundra ecosystems experiencing rapid climate change, we examined how phenotypic integration and within-environment trait variation jointly shape plasticity in the invasive herb Deyeuxia angustifolia and the native shrub Rhododendron aureum. Along an elevation (2050–2200 m) and encroachment gradient on Changbai Mountain, we measured 42 functional traits to assess whether integration limits plasticity, how this relationship is mediated by within-environment variation, and how trait relationship influences these dynamics. We found that in D. angustifolia, synergistic trait networks—characterized by high edge density, unique correlations, and a predominance of positive interactions—enhanced plasticity, whereas in R. aureum, trade-off–dominated networks imposed structural constraints that limited plasticity. Within-environment trait variation was the primary driver of plasticity in both species, with a stronger influence in D. angustifolia, particularly at higher elevations. This variation enabled D. angustifolia to exploit micro-environmental heterogeneity more effectively, while R. aureum’s limited variation and trade-off constraints reduced its adaptive capacity. Our results reveal that the combination of high trait variation and synergistic integration confers D. angustifolia a competitive advantage, facilitating its upward encroachment. In contrast, R. aureum’s restricted plasticity may hinder its persistence under ongoing environmental change, highlighting the importance of trait network structure and within-environment trait variation in shaping species responses to global change.
How to cite: Li, N.: Phenotypic integration predicts phenotypic plasticity in the invasive species Deyeuxia angustifolia but not the native shrubby species Rhododendron aureum, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11994, https://doi.org/10.5194/egusphere-egu26-11994, 2026.
The biological activity of a sandy pasture was quantified and modeled by integrating multiple categories of attributes and reducing the set of explanatory variables to the smallest subset with a highly statistically significant influence on the response variable. The attribute groups consisted of terrain-related factors (surface heterogeneity, altitudinal difference, topographic position index, etc.), soil properties (soil carbon, soil moisture, etc.), meteorological conditions (e.g., air temperature and precipitation), botanical characteristics (species abundance and diversity metrics), reflectance-based variables (vegetation indices), and physiological activity-related indicators (leaf area index, gross primary production). The datasets were collected from a one-ha spatial grid with a 10 m × 10 m resolution. The data collection spanned 10 occasions during the vegetation periods from autumn 2016 to autumn 2019.
Vegetation biological activity exhibits strong sensitivity to variability in both biotic and abiotic drivers, and species richness represents a key determinant of grassland response capacity. To quantify these processes, we constructed a composite variable that integrated below-ground functioning (derived from soil respiration measurements), above-ground productivity (based on above-ground biomass values), and the diversity of the sandy pasture. This composite metric was termed the biological activity factor (BF). To account for interannual and seasonal variability, all components of BF were rescaled before aggregation.
To gain a deeper insight into the key factors responsible for BF prediction and predictability, the upper and lower quartiles of the BF were modeled separately. This approach enabled the identification of the key drivers determining the biological activity of the vegetation under optimal (upper BF quartile) and stressed (lower BF quartile) conditions. We used linear and generalized additive models (GAMs) to estimate BF quartiles employing a reduced set of explanatory attributes selected through stepwise procedures based on statistical significance.
How to cite: Fóti, S., De Luca, G., Süle, G., Koncz, P., Pintér, K., Nagy, Z., and Balogh, J.: Predictability of the biological activity of a sandy grassland under optimal and stress conditions , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12181, https://doi.org/10.5194/egusphere-egu26-12181, 2026.
Banana (Musa sp.) is the most important fruit worldwide, as well as a major food crop. It is a semi-perennial herb that reproduces vegetatively through suckers. After bunch formation, the main banana plant senesces and the sucker forms the start of the next cycle. The belowground corm and the aboveground pseudostem are hypothesized to function as carbon storage organs supplying energy for fruit and sucker growth, particularly under stress. However, neither the existence of such reserves nor their role under stress has been experimentally confirmed. Accordingly, a field experiment was initiated in Guadeloupe (Caribbean) with a twofold objective: to quantify carbon storage and remobilization throughout the banana growth cycle and to assess its potential role under stress. More specifically, we evaluated the impact of stress caused by Black Sigatoka disease, one of the most important biotic limitations to banana production worldwide and the number one constraint in the region. The disease, as well as its management (sanitary leaf removal) causes a substantial reduction in source strength. We hypothesize that carbon reserves become particularly important under stress causing carbon depletion, as can be deducted indirectly from research on drought stress. Two banana varieties (Cavendish (AAA) and Big Ebanga (AAB)) were subjected to two contrasting leaf removal treatments (minimal and severe de-leafing). De-leafing, as well as leaf surface measurements were carried out on a weekly basis. Corm samples were taken at six predetermined times during the plant cycle, using a tree increment borer. During the vegetative phase and during fruit filling, four plants per treatment were furthermore destroyed for pseudostem sampling and in order to assess biomass allocation between leaves, pseudostem, corm, sucker and fruit. NSC (non-structural carbon) content of corm and pseudostem samples were determined through alcohol and enzymatic extraction, followed by spectrophotometric quantification. This is the first study focusing on carbon storage in banana and its potential role under stress. As climate change is expected to exacerbate a wide range of biotic (Black Sigatoka, Fusarium wilt) and abiotic (drought, heat) stresses, it is critical we gain insight into the role of carbon reserves in the banana plants' stress response.
How to cite: Vantyghem, M., Peraire-Brudey, L., Ramassamy, R., Lakhia, K., and Damour, G.: Carbon storage in banana – a key trait under stress?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13722, https://doi.org/10.5194/egusphere-egu26-13722, 2026.
Soils store a considerable amount of global carbon. Landslides, meanwhile, impair the soil’s ability to store carbon by disturbing vegetation and removing organic soil layers. In this context, it is becoming increasingly important to account for post-failure soil carbon recovery, and more specifically, for both structural and functional components of soil carbon recovery. We hypothesise that soil CO₂ efflux follows soil organic carbon content during post-event recovery. However, field evidence is still scarce, particularly regarding soil carbon recovery mechanisms and CO₂ efflux dynamics in slow-moving post‑landslide systems in temperate grasslands. This study compares soil organic carbon and CO₂ effluxes in post-failure and non-failure slow-moving landslides and suggests potential sources of carbon inputs in landslide-susceptible pre-Alpine managed grasslands.
To achieve this, we conducted two years of observations in control areas and slow-moving landslide areas that experienced a large landslide event in 2013 and have since exhibited slow creep with varying dynamics. Monthly monitoring includes land displacement velocities derived from manual and automatic inclinometer measurements, UAV surveys, greenhouse gas sampling, vegetation parameters, and land-use activity. Additionally, we collected a number of physico-chemical soil characteristics such as soil texture and structure, soil nitrogen and carbon properties, soil pH and electrical conductivity. All of this enabled us to analyse the recovery of CO₂ fluxes and soil organic carbon under different landslide conditions.
We found that CO₂ fluxes in the post-failure area recovered to 39% over a decade, which is slower than in lower-latitude regions. However, soil organic carbon recovered even more slowly, reaching only 17% relative to other slow-moving landslide areas and 25% relative to the control site. This divergence between CO₂ effluxes and soil organic carbon recovery dynamics is consistent with current literature. Our observations reveal a clear decoupling between CO₂ fluxes and SOC, suggesting that functional recovery may precede structural carbon recovery; we assume that CO₂ effluxes are influenced mostly by inputs of dissolved and labile organic carbon via surface and groundwater runoff. These findings may have implications at the global scale, given the thousands of landslides occurring worldwide each year and their potential influence on the global carbon cycle. Moreover, highlighting the distinct roles of structural and functional components of soil carbon recovery could support the development of more robust approaches to assess the soil carbon recovery trajectories and management strategies for post-event landslide areas.
How to cite: Grachev, K., Glade, T., and Glatzel, S.: The Influence of Slow-Moving Landslides on Soil Carbon Recovery: Decoupling Soil Organic Carbon and CO₂ Fluxes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13728, https://doi.org/10.5194/egusphere-egu26-13728, 2026.
We enhance the observation capabilities of existing high-grade ICOS flux tower site by implementing continuous proximal remote sensing and tree scale measurements to build a unique integrated multiscale, high frequency (10-30 min) observational system to address critical knowledge gap regarding how Mediterranean tree species respond and recover from climate extremes such as compound heat and water stress. This issue is particularly relevant for Quercus ilex, the dominant species in Mediterranean area, which combines drought tolerance with limited understanding of its threshold responses to stress.
The main objective is to explore the potential of these combined observations in monitoring and understanding the mechanistic processes that regulate the functional response of Mediterranean holm oak open woodlands to heat and water stress, where structural heterogeneity and fast stress responses remain poorly captured by current limitations of remote sensing based Earth Observation systems (medium spatial resolution, revisit frequencies of days to weeks) and by standard monitoring approaches, insufficient to capture short-term adaptive physiological responses occurring at hourly or minute timescales, such as stomatal closure, water transport regulation, photoprotective mechanisms, and xanthophyll cycle dynamics.
The flux tower and related infrastructure deliver continuous ecosystem scale measurements of turbulent fluxes of energy, evapotranspiration (ET) and CO2 (NEE, GPP), together with a comprehensive suite of meteorological variables and enhanced dense soil water observations (i.e. multiples soil water content and soil water potential profiles), complemented by point dendrometers, micro-tensiometers and sap flow measurements providing detailed information on tree water status and water transport dynamics at tree scale, and an innovative integration of state-of-the-art proximal remote sensing techniques: Thermal Infrared Imaging (TIR) coupled to a multispectral camera to resolve spatial patterns of vegetation surface temperature variations; Short-Wave Infrared Spectroscopy (SWIR) with novel Fabry-Perot micro-spectrometers for monitoring vegetation water content; Sun-Induced Fluorescence (SIF) and Visible-NIR Reflectance via FLOX system to distinguish active photosynthesis from photoprotective responses; and LED-Induced Fluorescence (LEDIF) to measure basal photosynthetic state and plant recovery.
In addition to provide comprehensive information to assess physiological and functional vegetation response to drought and heat stress, the integrated observational dataset is foreseen to be used for: (i) improving TSEB/3SEB evapotranspiration models to better characterize hydraulic and physiological constraints on water and energy fluxes and to enhance model performance; (ii) contribute to FLuorescence EXplorer (FLEX) mission Cal/Val activities by testing upscaling strategies in heterogeneous dehesa ecosystems within SPAFLEX project.
How to cite: Carrara, A., Alonso, L., Pacheco-Labrador, J., Burchard-Levine, V., and Martin, M. P.: Integrated Proximal Sensing and Ground-Based observations for drought and heat stress monitoring in a Mediterranean holm oak savanna, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14075, https://doi.org/10.5194/egusphere-egu26-14075, 2026.
Climate change imposes increasing stress on ecosystems worldwide through rising temperatures, altered precipitation regimes, and more frequent extreme events. In high-elevated environments, these pressures are often compounded by geomorphological disturbances, which represent a major stress factor shaping vegetation dynamics and biodiversity. Understanding how plant traits and functional diversity respond to such disturbances is therefore essential for predicting ecosystem responses to ongoing environmental change.
In this study, we investigated how geomorphic disturbance influences plant functional traits and biodiversity along elevational gradients in subalpine to alpine ecosystems. We hypothesised that: (i) disturbance-driven differences in species composition leads to functional differentiation at the community level, (ii) disturbance acts as a stressor inducing intraspecific variability in functional traits, and (iii) the proportion of thermophilic species increases on disturbed plots, particularly at higher elevations. Across three study sites, we sampled the five most abundant species per plot to test the interspecific variability as well as the three most frequent species shared across plots to test the intraspecific variability along elevation gradients. Key plant functional traits (leaf area, leaf dry weight, SLA, plant height) were measured and analysed using t-tests and non-parametric statistical approaches. For explaining the differences found Generalise Additive Models were performed.
Our results showed that, at the community level, only Specific Leaf Area (SLA) differed significantly between disturbed and undisturbed plots for the five most common species (interspecific variability). Furthermore, we could observe significant differences for the relative cover of bryophytes, lichens, dwarf shrubs, and trees. For herbs and graminoids the climate-induced growth (RC1) and the improved edaphic conditions (RC2) revealed to be more important. At the species level, disturbance-related stress led to significant intraspecific trait variability in several species, highlighting flexible trait responses under changing environmental conditions. Contrary to our expectations, the proportion of thermophilic species was consistently lower on disturbed plots compared to undisturbed plots across the entire elevational gradient, although it decreased with elevation in both plot types as expected.
Overall, differences in SLA likely reflect shifts in functional group composition under disturbance stress. Observed intraspecific trait variability along abiotic and disturbance gradients provides valuable insight into the capacity of alpine plant species to adjust their morphology and physiology in response to environmental stress, with important implications for biodiversity and ecosystem resilience under climate change.
How to cite: Ramskogler, K., Castlunger, S., Kinzner, S., and Tasser, E.: Geomorphic Disturbance as a Driver of Species Phenotypic Plasticity, Vegetation Cover, and Biodiversity in High-Elevation Belts, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16298, https://doi.org/10.5194/egusphere-egu26-16298, 2026.
Warming is expected to increase both soil organic matter decomposition and plant growth in alpine ecosystems, leading to an uncertain fate of soil carbon (C) stocks in these temperature-vulnerable ecosystems. There are very few empirical data over decadal timescales to address this uncertainty. Here, we conducted a 10-year warming experiment in which surface soil C stocks, together with C inputs (plant production) and outputs (microbial respiration), were measured each year under ambient and elevated temperatures in an alpine grassland. We observed that the decadal warming enhanced soil C stocks, particularly in the late stages of the experiments, due to warming-induced increases in plant C inputs. The increase in soil C stock was mainly due to the following three mechanisms. First, plant C input significantly increased under warming by shifting plant community composition towards grass dominance that had taller plant height and higher belowground productivity and allocation. The mechanisms were also related to the higher temperature optimum of grasses compared to non-grass species. Second, abundant precipitation and humid environments facilitated positive responses of ecosystem carbon uptake to warming. Third, ecosystem carbon fluxes showed optimal temperatures and were able to thermally adapt to climate warming, which benefit ecosystem carbon uptake. The above findings revealed the key response mechanisms of soil C stocks in alpine ecosystems to long-term climate change, enriched the understanding of the feedback relationship between the carbon cycle and climate change, and provided important parameters and experimental evidence for carbon cycle models.
How to cite: Niu, S.: Decadal warming-induced shifts in plant community composition and biomass allocation enhance alpine soil carbon accrual, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16473, https://doi.org/10.5194/egusphere-egu26-16473, 2026.
Freeze-thaw events (FTE) induce stress in the soil matrix, leading to the disruption of soil aggregates and consequently causing the release and mobilization of natural soil colloids. Hence, it is fundamental to understand the effect of FTE on the formation of natural soil colloids and colloid-facilitated transport of elements, especially nutrients such as P. In this study, the influence of FTE on natural colloids mobilized after precipitation was investigated. Therefore, columns were packed with 17 cm of disturbed forest topsoil. The soil columns were exposed to either ambient temperature throughout the experiment (control) or to freeze-thaw (FT) conditions, which involved 2 days of freezing at -14 °C followed by 1 day of thawing at ambient temperatures. The FT cycles were repeated five times. Leachate was collected from the columns a day after precipitation (or irrigation using artificial rainwater) after each FTE. Size-resolved elemental composition of colloids in the leachates was determined using Asymmetrical Flow Field-Flow Fractionation (AF4). Findings showed that FTE resulted in higher colloidal organic C (+135%) and P (+85%) loads in the leachates than the control at first FTE, and Fe (+37%) and Al (+67%) at the second FTE. Moreover, higher loads of the smaller colloidal Fe and Al were observed with FT than with the control at first and second FTE. For larger colloids, FT showed higher organic C and P than the control from the first to fourth FTE, and Ca, Mg, Mn, and Zn at the fourth FTE. In terms of bulk elemental load, FT released lower Ca, Mg, Mn, and Zn than the control at the second and third FTE. At the last FTE, higher cumulative colloidal Al (+122%) and P (+114%) were observed with FT than with the control. FT resulted in lower cumulative bulk load of Ca, Mg, Mn, and Zn than the control after the second FTE. Furthermore, colloidal Fe, Al, Ca, Mg, Mn, and Zn mainly consisted of smaller colloids, while larger colloids dominated colloidal P. The findings from this study suggest that repeated freeze-thaw cycles can increase mobilization of colloids and colloid-associated elements in the soil.
How to cite: Cacerez, J. C., Berns, A. E., Kruse, J., Weihermüller, L., and Siebers, N.: Influence of freeze-thaw cycles on natural colloids release of a forest soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17045, https://doi.org/10.5194/egusphere-egu26-17045, 2026.
Permafrost regions are highly vulnerable to global warming, as they warm much faster and store large amounts of organic matter (OM), which makes them key to the carbon-climate-cycle. Thermokarst processes, and coastal erosion strongly reshape permafrost landscapes. As thermokarst lakes (TL) have been shown to release organic carbon due microbial decomposition, drained thermokarst lake basins (DTLBs) can sequester OM again due to the potential to reaggregate permafrost in a cold climate, though this potential will slow or not occur in a warming climate. Therefore, understanding these processes is key to predict future potential greenhouse gas (GHG) emissions.
This study investigates the OM characteristics in such a TL-DTLBs landscape on the Baldwin Peninsula, located in the continuous permafrost zone of Alaska. A multiproxy approach of biogeochemistry, hydrochemistry, sedimentology and n-alkane biomarker analysis was used to investigate (1) the paleoenvironment of the landscape and (2) the characterization of the OM by its quantity, source and quality in terms of its degradation state, which is critical for mineralization processes and potential GHG release upon permafrost thaw. Four sediment cores were collected in 2024 along a transect representing multiple thermokarst stages, from an undisturbed permafrost upland through a thermokarst lake and a recently drained thermokarst basin to a nearshore marine environment.
Our findings show a continuous Pleistocene deposition in a strongly aeolian regime, with the oldest sediments of > 50 cal. ka BP in the drained lake basin (50 – 150 cm b.s.l.). The sediments are generally of coarse silt, and show with high water contents, and organic-rich layers typical characteristics of late Pleistocene Yedoma, while the deep layers show signs of an ancient fluvial environment and early Holocene thermokarst processes. Also, the biomarker analysis support a common terrestrial origin of the OM, indicating a secondary marine infiltration for the marine site, as well as a slightly aquatic influences, especially in the deeper layers, resulting from ancient thermokarst processes and the lake / marine phases. The carbon quantity decreases significantly from the upland to the marine site, with higher preserved OM in the taliks than in the perennial frozen layers (e.g. CPIthermokarst lake = 15.77 vs CPIupland = 8.08 in median).
Due the high ice amount and carbon quality, the studied deposits reveal a strong vulnerability to continued warming and thus constitute a high GHG release potential.
How to cite: Frauhammer, C., Seemann, F., Grosse, G., Schirrmeister, L., Meyer, H., Mollenhauer, G., Windirsch, T., and Strauss, J.: Deciphering organic matter degradation in the continuous permafrost zone of Alaska based on biomarker analyses., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18132, https://doi.org/10.5194/egusphere-egu26-18132, 2026.
Warming of the Arctic is causing permafrost thaw and the acceleration of the nitrogen (N) cycle. Permafrost thaw releases previously unavailable organic N reservoirs that are now available for decomposition. This is expected to increase the availability of inorganic N, which may ultimately lead to enhanced emissions of nitrous oxide (N2O). This is particularly relevant for Yedoma, ice-rich permafrost sediments that store large amounts of N and are commonly found across large areas affected by permafrost. Despite the few previous studies investigating the effects of permafrost thaw on the N cycle and N2O emissions, there is still poor understanding of the difference in N dynamics between the active and permafrost layers during and after thaw.
Here, we address this knowledge gap by conducting a N cycling study using 3 intact soil cores collected across the Baldwin Peninsula in northwest Alaska. These 2-m-long cores include the active layer, the interface between the active layer and permafrost, and more than one meter of ice-rich Yedoma permafrost. The study consisted of N2O measurements during initial thawing of the soil, detailed depth profiling of extractable N, including ammonium (NH4+), nitrate (NO3-), and total dissolved N (DN), right after the thaw, and a soil incubation experiment at 5 oC to determine N2O production under oxic and anoxic conditions. Also, we included a treatment under anoxic conditions with acetylene inhibition to estimate the total denitrification, including N2. Furthermore, we amended the soil with NO3- under anoxic conditions to investigate potential N2O production and denitrification and to reveal possible NO3- limitation of these processes.
The permafrost layers presented an accumulation of NH4+ content compared to the active layer, whereas NO3- was only found in the active layer and in minimal amounts. The active layer had the highest potential denitrification rate in the presence of NO3- and acetylene, but showed very low or negligible N2O production when NO3- was not added. No N2O production was observed in the permafrost layers in any of the treatments, even with the addition of NO3- or NO3- and acetylene, indicating that denitrification is not occurring. We suggestthat this lack of N2O production and denitrification activity is due to microbial limitation. These results can help better understand the significance of permafrost N release during permafrost thaw to the Arctic ecosystem and its climate feedback.
How to cite: Martínez-Risco Martínez, P., Hashmi, W., Strauss, J., Seemann, F., Palacín-Lizarbe, C., and Marushchak, M. E.: Differences in reactive nitrogen availability and N2O production between active layer and ice-rich Yedoma permafrost, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18948, https://doi.org/10.5194/egusphere-egu26-18948, 2026.
Agrovoltaics has been proposed as an innovative strategy to combine renewable energy production with agricultural activity, particularly in Mediterranean regions characterized by high solar radiation. In woody crops such as grapevine, the partial shading associated with these systems can modify the canopy microclimate and help mitigate the effects of excessive radiation on plant physiological status. However, information is still limited on how different shading systems affect the physiological response of grapevine.
In this study, we evaluated the effect of shading generated by agrovoltaic systems on the leaf physiological status of grapevine under field conditions. Three varieties (Tempranillo, Moscatel de grano menudo, and Garnacha) were studied under three treatments: an unshaded control, a shading net, and elevated solar panels installed above the vineyard, with the shading net and solar panels covering an equivalent shaded surface. Parameters related to incident radiation, photosynthetic pigment content, and different indicators of oxidative stress and antioxidant capacity in leaves were analyzed.
The results show that shading reduces incident radiation on the canopy, particularly in the upper part of the vine, and promotes physiological acclimation to lower radiation conditions. In this context, shaded plants tend to show higher chlorophyll content as a compensatory mechanism for reduced light availability. At the same time, a lower activation of mechanisms associated with light and oxidative stress was observed, with a stronger effect under the solar panel system. The response was variety-dependent, with Tempranillo and Moscatel showing higher sensitivity to shading, while Garnacha exhibited a more moderate response.
Overall, these results indicate that agrovoltaic systems, in addition to their role in energy production, may contribute to improving grapevine physiological status by attenuating the impact of excessive radiation. However, further studies are needed to assess how these physiological responses may translate into effects on yield and fruit quality. Within this context, agrovoltaics emerges as a promising approach for the adaptation of Mediterranean viticulture to scenarios of high radiation and climate change.
Keywords: agrovoltaics, grapevine physiology, radiation stress, mediterranean viticulture
Acknowledgements: This publication is part of project CPP2022-010020, funded by MCIU/AEI/10.13039/501100011033 and by the European Union “NextGenerationEU”/PRTR.
How to cite: Morales-Rodríguez, P. A., Peco, J. D., Villena, J., Atance, C., López-Perales, J. A., Higueras, P. L., and Moreno, M. M.: Effects of agrovoltaic shading on grapevine physiological status and stress responses, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20348, https://doi.org/10.5194/egusphere-egu26-20348, 2026.
Due to increased drought frequency following climate change, practices improving water use efficiency and reducing water-stress are needed. The efficiency of organic amendments to improve plant growth conditions under drought is poorly known. Our aim was to investigate if organic amendments can attenuate plant water-stress due to their effect on the plant-soil system and if this effect may increase upon ageing. To this end we determined plant and soil responses to water shortage and organic amendments added to soil. We compared fresh biochar/compost mixtures to similar amendments after ageing in soil.
Results indicated that amendment application induced few plant physiological responses under water-stress. The reduction of leaf gas exchange under watershortage was alleviated when plants were grown with biochar and compost amendments: stomatal conductance was least reduced with aged mixture aged mixture (-79 % compared to -87% in control), similarly to transpiration (-69 % in control and not affected with aged mixture), . Belowground biomass production (0.25 times) and nodules formation (6.5 times) were enhanced under water-stress by amendment addition. This effect was improved when grown on soil containing the aged as compared to fresh amendments. Plants grown with aged mixtures also showed reduced leaf proline concentrations (two to five times) compared to fresh mixtures indicating stress reduction. Soil enzyme activities were less affected by water-stress in soil with aged amendments.
We conclude that the application of biochar-compost mixtures may be a solution to reduce the effect of water-stress to plants. Our findings revealed that this beneficial effect is expected to increase with aged mixtures, leading to a better water-stress resistance over time. However, while being beneficial for plant growth under water-stress, the use of amendments may not be suited to increase water use efficiency.
How to cite: Vedere, C., Lebrun, M., Biron, P., Planchais, S., Bordenave Jacquemin, M., Honvault, N., Firmin, S., Savouré, A., Houben, D., and Rumpel, C.: The older, the better: ageing improves the efficiency of biochar-compost mixture to alleviate drought stress in plant and soil., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20830, https://doi.org/10.5194/egusphere-egu26-20830, 2026.
mortality, canopy die-off and forest carbon sink decline. Forest adaptation and resistance to drought stress largely rely on hydraulic diversity – the variety and range of hydraulic traits that regulate water use under drought conditions. Yet, how hydraulic diversity emerges within temperate forests and links to forest growth remains poorly resolved. To fill these gaps, we use eight hydraulic traits relating to stomatal closure, structural demand management, water storage, hydraulic resistance and rooting depth to quantify hydraulic diversity within forests, explore how it varies across temperate regions and explore its relationship with forest stem growth using the USA forest inventory data. A total of 31,304 forest plots were aggregated at a 1° grid-cell resolution and hydraulic diversity (721 metacommunities; those with fewer than three tree species are excluded) was quantified as the hypervolume size along the first two axes of principal component analysis (PCA). We found that higher diversity values were observed in the regions of the eastern USA while lower diversity values were found in the western and central USA and boreal regions. The variation in strategy diversity in temperate forests aligns mostly with changes along the acquisitive – conservative axis, spatial hydraulic diversity within temperate forest metacommunities indicates summer precipitation is more crucial than other climate variables. Interestingly, forests with low diversity are widely distributed across the full range of summer precipitation, suggesting that factors beyond water availability – such as temperature – may play an important role, particularly in the Pacific coast of Northern America. Moreover, we observed there is a positive relationship between hydraulic diversity and stem growth across the USA forest metacommunities. Our results provide a foundation for understanding forest hydraulic diversity and improving the accuracy in predicting forest carbon sink potential under a warmer and drier conditions.
How to cite: Liu, D. and Wang, S.: Understanding the role of hydraulic diversity on temperate forest growth across the USA, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21249, https://doi.org/10.5194/egusphere-egu26-21249, 2026.
Fine roots (<2 mm in diameter) are among the most functional components of the plant system, playing a critical role in nutrient and water uptake as well as in regulating the carbon cycle. Despite their importance, fine roots remain one of the least studied components of forest ecosystems, even though they make a substantial contribution to forest productivity, carbon allocation, nutrient uptake, and turnover.
In the Himalaya, banj oak (Quercus leucotrichophora) is a major forest forming species that is increasingly challenged by the encroachment of chir pine (Pinus roxburghii), along with anthropogenic disturbances and climate change. While aboveground dynamics of banj oak and chir pine forests are well documented, studies on belowground processes are limited. The present study aims to understand fine root dynamics, including biomass, productivity, turnover, and nutrient concentration, in banj oak, chir pine, and banj oak-chir pine mixed forests, and to assess the belowground impacts of chir pine encroachment into banj oak forests.
Three sites were selected for each forest type following a reconnaissance survey. Site selection was based on forest age structure determined through phytosociological analysis. Aspect, slope, elevation, and terrain were also considered to ensure comparability among sub-sites. At each selected site, a uniform plot was established, and six sub-plots were marked for fine root sampling using the sequential coring method. Five samples were collected from each sub-plot on a monthly basis. Sampling involved removal of surface litter followed by coring up to 30 cm soil depth using an 8 cm diameter corer. The separated roots are oven-dried at 65°C until constant weight achieved. Dried samples are grounded using a Willey mill and stored in plastic containers for further analysis.
Preliminary results indicate that fine root biomass production is highest in banj oak forests, followed by oak–pine mixed forests and pine forests, reflecting distinct patterns of carbon allocation and belowground dynamics among the three forest types. Fine root turnover rates are lowest in pine forests, suggesting rapid growth and mortality of fine roots in pine-dominated stands. The study will provide important insights into belowground processes associated with chir pine encroachment into banj oak forests and will aid in assessing ecosystem services related to fine root production, carbon cycling, and nutrient dynamics in Himalayan forest ecosystems.
How to cite: Verma, A. K. and Chand, T.: Fine Root Dynamics: Belowground Carbon and Nutrient Cycling in Oak, Pine, and Oak–Pine Mixed Forests of the Central Himalaya, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21730, https://doi.org/10.5194/egusphere-egu26-21730, 2026.
Posters virtual: Tue, 5 May, 14:00–18:00 | vPoster spot 2
EGU26-19408 | Posters virtual | VPS5
Enhancing carbon sequestration in water stressed plant–soil systems through soil amendment with a Superabsorbent Nanocomposite derived from natural materialsTue, 05 May, 14:45–14:48 (CEST) vPoster spot 2
Climate change and intensifying droughts represent a critical challenge to agricultural productivity and soil sustainability. This study evaluated the effect of two superabsorbent amendments with contrasting chemical compositions (polyacrylate-based polymer and a biodegradable polysaccharide nanocomposite) on carbon dynamics in common beans grown under drought conditions. The experimental design included analyses of morphological parameters, elemental composition, 13C allocation, and soil density fractionation. The results showed that drought drastically reduced biomass and nitrogen in leaves and roots, increased C:N ratios, and decreased root-derived carbon (RDC) incorporation, especially in stable soil fractions. The application of superabsorbents reversed these effects, increasing 13C translocation to roots and RDC in soil. NSN stood out for its ability to increase total RDC compared to the drought control parallelling the irrigated control in the heavy fraction associated with minerals, a key indicator of stable carbon sequestration. In contrast, Com mainly promoted flow to labile fractions, with less impact on stabilisation. These findings demonstrate that superabsorbents might be an effective tool for sustaining crop productivity and strengthening carbon sequestration in agroecosystems under conditions of increasing aridity.
How to cite: Guarda Reyes, M., Calabi Floody, M., Biron, P., Salvidar, M., Mora, M. D. L. L., and Rumpel, C.: Enhancing carbon sequestration in water stressed plant–soil systems through soil amendment with a Superabsorbent Nanocomposite derived from natural materials, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19408, https://doi.org/10.5194/egusphere-egu26-19408, 2026.
