Soils of boreal peatlands are among the largest terrestrial reservoir of organic carbon (C), yet their long-term response to warming remains uncertain, especially regarding C turnover and stabilization.

Located in a northern American boreal peatland, the SPRUCE (Spruce and Peatland Responses Under Changing Environments) site is a unique warming experiment, which is partially exposed for ten years to warming and elevated CO₂ concentration. Here, we aim to assess how different temperature gradients (+0, +2.25, +4.5, +6.75, and +9°C) and CO₂ addition (+500ppm above ambient) affected the quantity and quality of soil organic matter (SOM) in a 2 meter deep soil over a 10-year period. Our approach integrates lignin-derived phenol analysis with stable isotope (δ¹³C) measurements to disentangle C incorporation and decomposition in SOM at the molecular level.

Ten years of applied soil warming and elevated CO₂ concentration have altered OM quality and quantity, with contrasting effects in topsoil and subsoil. Warming promoted plant-derived C loss through accelerated decomposition of labile C inputs. Although still unclear, the response to elevated CO₂ shows a pattern of increased plant productivity and OM incorporation, which may partly offset C losses. Biomarkers and isotope analyses prove that SOM molecules undergo rapid turnover, demonstrating C instability in soils subject to warming in these vulnerable ecosystems.

How to cite: Ceresa, E., Vouillamoz, C., Mayes, M., and Wiesenberg, G.: Incorporation and Turnover of Plant-Derived Polymers in a Warmed Peatland , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1725, https://doi.org/10.5194/egusphere-egu26-1725, 2026.

Ombrotrophic peatlands store a large fraction of global soil carbon, yet their long‑term response to climate warming and elevated atmospheric CO₂ remains uncertain, particularly regarding plant carbon allocation and biochemical inputs to peat. Experimental warming and CO₂ elevation can alter plant community composition, tissue chemistry and carbon partitioning, with potential feedbacks on peat accumulation and decomposition.

Previous work after 3 years of whole‑ecosystem warming and CO₂ elevation showed rapid shifts in carbon allocation and lipid composition in dominant bog plants. Ten years after the onset of these treatments, longer‑term acclimation, community changes and root responses may reinforce, dampen or qualitatively change these initial patterns. This study aims to assess how decadal warming and elevated CO₂ affect carbon partitioning and lipid composition in an ombrotrophic bog plant community, with an additional focus on roots as pathways of belowground carbon input.

The study is conducted on an ombotrophic peatland experiment (SPRUCE, Minnesota, USA), where whole ecosystems  have been exposed for ten years to a gradient of warming (+0, +2.25, +4.5, +6.75 and +9 ◦C), under ambient or elevated atmospheric CO₂ (+500ppm) concentrations in open-top chambers. Within each enclosure, representative samples of the dominant plant functional types (Sphagnum-dominated communities of mosses from hollows and hummocks, ericaceous shrubs Rhododendron groenlandicum and Chamaedaphne calyculata and trees Picea mariana and Larix laricina) were collected. For vascular plants, both aboveground tissues (leaves and branches) and belowground compartments (fine and coarse roots  retrieved from sieved peat) were collected. Bulk tissue analyses include carbon and nitrogen concentrations and stable carbon (δ¹³C) isotope composition to quantify treatment effects on carbon assimilation and partitioning among tissues. Lipids are extracted and separated into major classes such as n‑alkanes, n‑fatty acids, and n‑alcohols, which serve as biomarkers of plant functional types, membrane properties and potential stress responses.

Here, we show that long‑term warming enhanced allocation to shrubs and alter the elemental and lipid composition of both aboveground and belowground responses with species-specific differences, while elevated CO₂ did not show to alter lipid concentration or composition of plant tissues. In plant tissues, warming promoted shifts in lipid profiles towards more saturated and degradation‑resistant moieties and modified the relative abundance of lipid classes due to stress response and structural adaptation.

By combining new measurements with earlier data on the same plant community and soil profile, this work provides a decadal‑scale view of how warming and elevated CO₂ reshape plant carbon partitioning and molecular composition in an ombrotrophic bog. This will help constrain the trajectories of boreal peatland carbon cycling under global change.

How to cite: Vouillamoz, C., Ceresa, E., Mayes, M. A., and Wiesenberg, G. L. B.: From Shoots and Roots: Ten Years of Warming and Elevated CO₂ Modify Plant Carbon Allocation and Lipid Chemistry in a Boreal Peatland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1724, https://doi.org/10.5194/egusphere-egu26-1724, 2026.

Plant carbon (C) inputs through fine roots and extramatrical mycelia (EMM) play a crucial role in driving soil organic C (SOC) pools. However, few studies have explored the distinct roles of fine roots and EMM on SOC accumulation, how these inputs drive the priming effect (PE) on native SOC decomposition, and how warming affects these processes in climate-sensitive alpine meadow ecosystems. In this study, we placed ingrowth cores with different mesh sizes (2 mm, 48 μm, and 1 μm) containing C₄ soil in the field to quantify fine root- and EMMderived C into particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) and their impact on the decomposition of native SOC in an alpine meadow in the hinterland of Qinghai-Tibet Plateau for 3 years under experimental warming (~2.4 ℃). The results showed that fine roots promote SOC accumulation, particularly as MAOC. In general, newly sequestered C derived from fine roots exceeded the loss of native C via PE induced by fine root C input. In contrast, EMM had no effect on SOC as EMM-derived C inputs were counterbalanced by native C decomposition induced by EMM. Additionally, fine root-derived new SOC and new MAOC were significantly higher than that derived from EMM, while the PE induced by fine roots and EMM showed no significant difference. These findings suggested that warming (~2.4 ℃) had no detectable effect on SOC pool, new SOC inputs, and the PE on native SOC decomposition. However, warming mitigated the loss of native POC induced by either EMM or fine roots. In summary, fine roots play a leading role in SOC accumulation and warming (~2.4 ℃) has minor effects on SOC dynamics in the alpine meadows.

How to cite: Chen, L., Zhao, X., Tian, Q., Yang, Y., Jiang, Q., Müller, C. W., and Liu, F.: Differential effects of fine root- and mycelium-derived carbon on soil organic carbon in response to warming in an alpine meadow, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7296, https://doi.org/10.5194/egusphere-egu26-7296, 2026.

Alpine tundra ecosystems are widely regarded as small but persistent sinks of atmospheric methane (CH₄), yet it remains unclear how ongoing climate-driven shifts in vegetation composition and productivity will alter CH₄ exchange. As a result, predicting whether the alpine tundra will act as a CH₄ sink or source in the future requires an understanding of the governing mechanisms and links between vegetation CH₄ production and consumption. To address this gap, we explored the drivers and magnitude of CH₄ and carbon dioxide (CO₂) fluxes across fine scale alpine tundra vegetation gradients in Kaska First Nations Ancestral territory, now known as northern British Columbia. Using a systematic grid approach, we measured fluxes and environmental parameters from 100 plots over a 3-day period during peak growing season. Our design captured dominant vegetation types and key transition zones of microclimatic gradients across a south facing alpine slope. We found that CH₄ uptake was greater under light vs dark chamber conditions across most plant functional types, suggesting a link between photosynthesis and CH₄ uptake. Our light-only chamber condition statistical model further indicated that CH₄ uptake covaries most strongly with net ecosystem exchange, soil temperature, and nutrient availability (Cu, P, and total N). Together, these results suggest that climate-driven changes in vegetation structure and productivity may alter CH₄ uptake strength in alpine tundra ecosystems, underscoring the importance of resolving plant-soil processes for predicting future CH₄ dynamics.

How to cite: Castro Morales, L., McGuire, K., Morey, G., Virkkala, A., and Kuhn, M.: Enhanced Methane Uptake under Light Conditions in an Alpine Tundra Ecosystem, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15185, https://doi.org/10.5194/egusphere-egu26-15185, 2026.

Mycotoxin contamination of cereals remains a major threat to food security, as the development and toxin production of fungal pathogens are strongly controlled by climate. This study presents a continental-scale assessment of climatic suitability for three key mycotoxigenic fungi, Aspergillus flavus, Fusarium graminearum and Fusarium verticillioides, across Europe over a six-decade period from 1961 to 2020. Using daily ERA5-Land temperature and precipitation data and species-specific thermal response functions, we calculate a composite Risk Index that combines suitability for vegetative growth and sporulation. Days with index values exceeding 0.5 are classified as “risk days.” Results show a substantial increase in the annual number of risk days across Europe for all three species. Aspergillus flavus exhibits the strongest relative increase, exceeding 90 percent in several parts, together with a clear northward expansion into parts of Central Europe. By integrating these results with high-resolution maps of maize and wheat cultivation, we identify agriculturally important regions where warming has transformed fungal risk from occasional to persistent. In several hotspots, the number of risk days has doubled compared to the baseline period. This trend closely mirrors increases in the frequency of hot days above 25 °C during the growing season. These findings indicate that climate warming is rapidly intensifying and redistributing mycotoxin risk in Europe, with serious implications for cereal safety, public health, and climate adaptation strategies.

How to cite: Raj, R., Rieder, H., Balkova, D., Camardo Leggieri, M., and Battilani, P.: Spatio-Temporal Shifts in Climatic Suitability for Mycotoxins in Europe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18463, https://doi.org/10.5194/egusphere-egu26-18463, 2026.

The process of rapid urbanization is a global phenomenon that exposes the natural landscape to high levels of nitrogen (N) deposition, leading to serious ecological consequences. How does soil biological nitrogen fixation (BNF), a crucial process for replenishing nitrogen in terrestrial ecosystems, respond to urban expansion and consequent N deposition? To address this, we established a transect from the city center to the countryside to capture the urban–rural gradient. Permanent sites were set up along the gradient to encompass urban, suburban, and remote rural forests. A 5-year large-scale field experiment of N addition was conducted to simulate N deposition, aiming to investigate the impact of N deposition on soil BNF along this urban-rural gradient. We found that soil BNF activity was drastically reduced (dropped by 94.2% to 96.5%) in both urban and suburban forests compared with the rural forest without additional N application. Nitrogen addition treatments had no effect on BNF activity in the urban forest, but significantly decreased BNF activity in the rural forest by over 50% with low N addition. Further analysis revealed that reductions in BNF activity were associated with changes in the composition of diazotrophic communities, favoring facultative diazotrophs that are detrimental to soil BNF. Soil acidification was primarily responsible for limiting soil BNF and associated microbes in the urban forest. Overall, our findings indicate that external N inputs primarily pose a threat to soil diazotrophic communities and their N fixation capacity in rural forests, whereas this adverse effect is not persisted in urban forests, thereby improving our understanding of soil behavior and biogeochemical cycles in forest landscapes.

How to cite: Tao, X., Fu, R., and Zhu, B.: Diverging patterns at urban-rural forest grandients:biological nitrogen fixation responses to N addition, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4400, https://doi.org/10.5194/egusphere-egu26-4400, 2026.

Dissolved organic matter (DOM) represents one of the most dynamic organic carbon pools in soils, and its molecular composition ultimately governs carbon mobilization, transformation, and stabilization. However, the profound differentiation in both quantity and quality of DOM across the entire soil profile under long-term warming remains poorly resolved. Therefore, this study conducted an eight-year whole-soil warming experiment (+4 °C) in the alpine grasslands of the Tibet Plateau to investigate the response of DOM molecular composition to warming across four soil layers: 0–10 cm (surface), 10–30 cm (shallow), 30–60 cm (middle), and 60–100 cm (deep). Overall, warming significantly increased DOM concentrations in surface soil, whilst DOM in shallow, middle and deep soil layers showed only marginal increases that did not reach statistical significance. In contrast, warming drives the reconfiguration of DOM composition across the entire profile, primarily concentrated in molecules such as CHO, CHON, CHOS, and CHONP, exhibiting pronounced depth dependence. Concurrently, the relative intensity of aromatic and highly unsaturated compounds in the surface and shallow soils was lower under warming treatment compared to the control, whereas the aliphatic and peptide compounds exhibited the opposite trend. This finding indicates that warming induces a shift in DOM composition from relatively humic towards one dominated by aliphatic/nitrogen-rich components. Furthermore, the relative intensities of carboxyl-rich aliphatic molecules (more recalcitrant DOM fraction) in middle and deep soils significantly increased under warming conditions. Collectively, these results demonstrate that long-term whole-soil warming reshapes the DOM composition through depth-specific pathways, underscoring that deep-soil DOM can respond fundamentally differently from topsoil.

How to cite: Chen, G. and Zhu, B.: Long-term whole-soil warming restructures the molecular composition of soil dissolved organic matter, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4317, https://doi.org/10.5194/egusphere-egu26-4317, 2026.

Microbial communities and their functionality are affected by climate change, which consequently impacts the functionality of soil biogeochemical cycles and in turn the persistence of individual tree species. Despite their importance for forest ecosystems, few studies have investigated the impacts of multiple, concurrent elements of climate change on microbial communities under tree species with contrasting drought tolerance and different biogeographic origins.

In our study, we investigated how soil microbial communities of different native and non-native tree species responded to warming and warming associated with drought. The experiment was located in Switzerland and included three forest sites with different climatic and environmental characteristics where temperature and precipitation have been manipulated since 2022. Soil microbial communities were assessed using DNA metabarcoding, and extracellular enzyme activities were assessed alongside environmental variables and soil nutrient availability.

Preliminary results showed that strong differences across sites shape microbial community composition and modulate their responses to the experimental climate treatments. The strongest effects of climate manipulations were found at the warmest and driest site. Soil microbial community composition responses to the different climate change treatments further among the tree species. In addition to microbial community composition, microbial functioning, as assessed via enzymatic activities, also differed across sites and generally decreased with the climate treatments, suggesting that biogeochemical cycles are likely to change in the future.

Our research aimed to clarify the possible consequences of warming and drought on forest microbiomes and consequently soil biogeochemical cycles under global change. This will support the development of climate change mitigation strategies to maintain forest ecosystem functionality and to choose future tree species able to resist climatic stresses.

How to cite: Burini, G., Risch, A. C., Moser, B., Cordero, I., Gombeer, S., and Anthony, M. A.: Soil microbial communities' compositional and functional response to climate change and different three species, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12702, https://doi.org/10.5194/egusphere-egu26-12702, 2026.

Deforestation is a global issue, threatening carbon stock and biodiversity worldwide. African tropical regions are experiencing intense deforestation, primarily driven by agricultural expansion. The strong reliance of rapidly growing populations on forest resources further increases pressure on these ecosystems. Smallholder subsistence farming, combined with weak governance and limited soil and forestry management, has contributed to progressive forest fragmentation, declines in biodiversity, and reductions in ecosystem resilience. The rapid decline of African tropical forests raises critical questions about their ability to recover naturally. This study investigates the role of soil in explaining the persistence of grassland vegetation and the consequent limited forest recovery. Specifically, soil samples from grassland-dominated areas of Kibale National Park in Uganda are collected, air-dried, and analysed to determine key properties influencing soil water availability, including bulk density, gravel content, and soil texture. Bulk density and gravel content are measured because of their influence on porosity and soil water availability. Soil texture is obtained using spectroscopy and used to help explain potential vegetation patterns due to its effect on soil water availability. These properties are also compared with soil data from forested areas within the same park. The results reveal clear differences between grassland and forest soils. Grassland soils contain less clay and show lower porosity than forest soils. These characteristics help explain the persistence of grassland vegetation in the studied tropical landscape and support the conclusion that soil physical properties influence vegetation distribution through their effect on soil-water-plant interactions.

How to cite: Oggier, N. M.: Soil Texture as Physical Driver of Forest and Grassland Occurrence in Kibale National Park, Uganda, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18237, https://doi.org/10.5194/egusphere-egu26-18237, 2026.

Much of our understanding of the warming response of soil respiration (Rs) is derived from experiments that warm only the soil surface, potentially underestimating warming impacts on belowground processes and overestimating contributions from aboveground warming. Although many studies report increased Rs under warming when moisture is not limiting, estimates of temperature sensitivity vary widely across experiments.

The current analysis harnesses data from the Soil Warming to Depth Data Integration Effort (SWEDDIE) to assess the temperature sensitivity of Rs as a function of warming and soil moisture over time and depth across the contrasting climatic and ecosystem conditions of 16 deep soil warming experiments worldwide. We hypothesize that the seasonal pattern of soil CO2 fluxes may differ between warmed and ambient temperature plots, so we will first analyze the data from warmed and treatment plots separately, followed by a traditional synchronous comparison of CO2 fluxes between warmed and ambient plots.

Field warming studies provide a unique opportunity to observe the full complexity of the response of Rs responses to warming at an ecosystem scale, but disregarding warming impacts in biologically active deeper soil layers has the potential to create bias when interpreting the relative contributions of autotrophic and heterotrophic sources of Rs. This work is intended to address this potential bias as well as highlight potential limitations of assuming stationary or globally uniform Rs temperature responses.

How to cite: Beem-Miller, J. and the Soil Warming to Depth Data Integration Effort Team (SWEDDIE): Soil CO2 flux responses to experimental warming over time and space: The whole soil story, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-23017, https://doi.org/10.5194/egusphere-egu26-23017, 2026.

Modeling future soil organic carbon (SOC) dynamics is subject to significant uncertainty due to oversimplified representations of our mechanistic knowledge on C cycling across pedogenetically distinct soil types. To address this issue, we investigated how different calibration strategies affect modeled SOC stocks and turnover times across a pedo-climatic soil gradient in Chile. First, we performed a calibration for each site to obtain site-specific parameters and to derive empirical relationships between mineral associated organic carbon (MAOC)-related model parameters and soil mineralogical properties. Second, we performed a multi-site calibration testing (i) different site-selection strategies and (ii) the use of model parameters calculated based on the obtained relationships with mineralogical properties. Finally, we simulated an intermediate CMIP6-warming scenario (SSP2-4.5) to quantify relative changes in SOC stocks and how they related to the simulation using site-specific parameter sets. Our results show that considering soil heterogeneity through relating soil mineralogical properties to model parameters is a promising way to tackle the common oversimplification of soil landscapes in current modelling frameworks. Multi-site calibrations disregarding established empirical relationships failed to reproduce overall SOC stocks and MAOC turnover times regardless of calibration site selection. Capturing heterogeneity of MAOC turnover times was key to reflect the response of SOC to warming. We conclude that the relation to climatic and soil mineralogical properties and pedogenetic modification of MAOC turnover time, is crucial to improve the simulation of SOC stocks and its future responses to warming at larger scales.

How to cite: Mainka, M., Van de Broek, M., Wasner, D., Zagal Venegas, E., and Doetterl, S.: Mineralogical Proxies Constrain Turnover and Warming Responses at Regional Scale, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8277, https://doi.org/10.5194/egusphere-egu26-8277, 2026.

Nitrogen cycling regulates ecosystem productivity and carbon sequestration in terrestrial ecosystems, yet its response to climate warming remains uncertain. Here, we compiled the most comprehensive dataset to date, synthesizing 7,991 observations from 417 field warming experiments worldwide and combining them with random forest regression and Community Land Model (CLM) simulations. Field warming significantly accelerated nitrogen cycling, increasing N₂O emissions (+24.7%), mineralization (+25.8%), nitrification (+51.7%), and denitrification (+41.1%). Soil inorganic nitrogen also increased, while plant nitrogen remained largely unchanged. Elevated natural abundance of ¹⁵N indicated that warming alleviates nitrogen limitation and promotes more open nitrogen cycles. Soil moisture, ecosystem type, and warming magnitude were key drivers. N₂O emission and nitrification further intensified with increased warming magnitude in random forest analyses. In contrast, CLM5-BGC simulated weak responses in N₂O emissions and nitrification and negative changes in nitrogen mineralization, substantially diverging from field observations. These discrepancies highlight the omission of microbial processes and the oversimplification of large-scale ecosystem feedbacks, respectively. Uniquely, this study provides the first direct comparison among empirical data, random forest regression, and CLM simulations, revealing discrepancies and their potential causes. Collectively, our findings provide robust evidence that terrestrial nitrogen cycling is more responsive to climate warming than previously recognized and underscore the importance of integrating multiple analytical approaches to synthesize cross-scale ecological data.

How to cite: Wang, X., Ni, C., Fan, Z., Schimel, J. P., Torn, M. S., and Zhu*, B.: Terrestrial ecosystem nitrogen cycling in response to field warming: Global patterns and future trends, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1772, https://doi.org/10.5194/egusphere-egu26-1772, 2026.

The stability of soil organic carbon (SOC) governs the carbon resistance to decomposition. Thereby, its response to warming is a key determinant of SOC dynamics under warming. However, SOC stability is an ecosystem property regulated by complex mechanisms, which complicates its quantification. Recent insights suggest that SOC stabilization mechanisms collectively contribute to microbial energy limitation. Accordingly, the bioenergetic perspective provides promising approaches for quantifying SOC stability under warming. Here, based on an 8-year whole-soil warming experiment in an alpine meadow on the Tibetan Plateau, we assess warming (+4℃) effects on the bioenergetic signature of SOC across depth (0-100 cm). We find that the activation energy (E_a, representing potential microbial energy investment) increases with depth, whereas the energy density (E_d,representing potential microbial energy gain) declines. This depth-dependent pattern implies that greater energy limitation may contribute to higher SOC stability in subsoil than in topsoil. Moreover, we find that whole-soil warming decreases E_a across depth while has no significant effect on E_d. The reduction of E_a suggests that warming may lower the energy barrier of decomposition reactions. Overall, our results demonstrate that warming will alleviate microbial energy limitation and thereby may threaten SOC storage.

How to cite: Wu, W. and Zhu, B.: The effect of whole-soil warming on the bioenergetic signature of soil organic carbon, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4315, https://doi.org/10.5194/egusphere-egu26-4315, 2026.

Litter decomposition is a key process in the global carbon cycle, primarily driven by microbial communities. At the litter-soil interface, microbes interact directly with both substrates and environmental conditions, often exhibiting distinct functional traits. However, differences between interface and non-interface microbial communities remain underexplored. This study conducted a year-long field litter burial experiment on Segrila Mountain in Tibet (3500–4300 m), using high-throughput sequencing and bioinformatics to investigate how interface microbes influence decomposition in alpine forests. Our findings reveal that, although the dominant bacterial and fungal phyla are similar between interface and non-interface soils, Acidobacteria are less abundant at the interface compared to non-interface soils, whereas Proteobacteria and Actinobacteria are more abundant. Interface microbial networks, constructed by Spearman correlations and modularity detection algorithms, display greater structural dynamics and complexity than those in non-interface soils. Variation partitioning analysis reveals that core microbial modules of the interface and non-interface soils, as well as elevation, account for 32.84 %, 3.79 %, and 5.39 % of the variation in litter decomposition, respectively. In the structural equation model, core interface microbial modules exert a significant and direct positive effect on both litter decomposition and lignocellulosic component breakdown, while non-interface modules are not significantly associated. Overall, the structure and activity of interface microbial communities dominate litter degradation dynamics. This study advances our understanding of the critical litter-soil interface processes in maintaining forest soil functions and offers a basis for managing carbon and nutrient dynamics under changing climate conditions in alpine forest ecosystems.

How to cite: Wei, Y.: Interfacial microbial communities drive litter decomposition along elevation gradients in alpine forest ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21767, https://doi.org/10.5194/egusphere-egu26-21767, 2026.

Root dynamics are difficult to measure at biogeochemical-relevant scales of space and time and the source of many uncertainties in models and scaling.

Because roots grow, respire, host mycorrhizal fungi, produce exudates and eventually turn over, they drive carbon exchanges with both the soil and atmosphere which are just as critical, but more complex, than leaf-level exchanges. But because roots are hard to measure, their temporal dynamics are often ignored or assumed to be coupled to leaves (e.g. root seasonal cycles align with leaf phenology). This paradigm dominates design of field experiments, and vegetation components of climate models assume a simple parameterisation based on broadly untested assumptions.

In contrast, when root dynamics are studied directly, there is ample evidence that roots and leaves are rarely in sync and respond differently to environmental conditions. Triggers and limits to root dynamics are poorly understood. Roots and their partner organisms may grow, function, and turn over coupled, uncoupled or offset from leaves or greenhouse fluxes, as plant resource allocation shifts due to both environmental and physiological constraints.

We are implementing custom automated minirhizotron (‘root camera’) systems across a network of eddy covariance sites to make measurements of root dynamics and phenology directly. Building on previous work, where we measured root dynamics with these systems at unprecedented time frequency, we are now linking these dynamics to measured greenhouse gas fluxes from eddy covariance systems and soil respiration autochambers. But making indirect and image-based measurements belowground is challenging – many aspects of minirhizotron systems are not optimised for high frequency measurements and timeseries data 

Here I will show both some of the results from these systems, and some of the advances in the design and implementation of field root imaging which we are making to improve understanding of this critical component of ecosystems at scales from seasonal to sub-daily.

How to cite: Nair, R., Brennan, R., Dibben-Dean, P., Ganti, A., Palk, I., and Schevelier, J.: Automating Dynamic Root Measurements to Understand Soil and Ecosystem GHG Fluxes, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11273, https://doi.org/10.5194/egusphere-egu26-11273, 2026.

Soil respiration is one of the main carbon fluxes and is controlled by the activity of the heterotrophic microorganisms, in addition to environmental factors, and has a significant influence on soil carbon cycling. This study aimed to examine the temporal patterns of soil respiration under field conditions, especially regarding heterotrophic respiration (R_h), its contribution to soil CO₂ efflux, and its relationship to the microbial functional diversity in a conventionally managed cropland in Hungary. Field measurements were performed in soil-installed tubes (40 cm depth, 16 cm diameter, root exclusion) for measuring R_h  and total soil respiration (R_s) was also measured under natural field conditions during the vegetation period. Soil CO₂ fluxes were measured in the field by an automatic soil respiration system under various environmental conditions. Soil temperature and soil moisture were measured in close conjunction, and data processing was carried out along with statistical analyses using R. During the study period in 2025, we took soil samples and microbial functional activity was measured using the Biolog EcoPlates™ technique in order to gain further insights into carbon substrate utilization by the microorganisms.

Average R_s was 2.77 µmol CO₂ m⁻² s⁻¹, while average R_h amounted to 1.22 µmol CO₂ m⁻² s⁻¹. The contribution of heterotrophic respiration to total soil respiration (R_h/R_s) ranged from 0.16 to 1 depending on the phenological phase.

How to cite: Nahal, I., Posta, K., De Luca, G., Foti, S., and Balogh, J.: Heterotrophic respiration and microbial functional diversity in a conventional cropland in Hungary, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12636, https://doi.org/10.5194/egusphere-egu26-12636, 2026.

Global biodiversity manipulative experiments report positive effects of plant diversity on ecosystem productivity. Yet, there is lower confidence in predicting a positive plant diversity effect on soil carbon (C) sequestration, largely due to limited understanding of how the decomposition of native soil C responds to diversity-promoted fresh C inputs, the so-called priming effect. Combining a large-scale biodiversity manipulative experiment with stable isotope (13C-glucose) labeling, we found that the priming effect decreased with increasing tree species richness. This reduction was characterized by decreased positive priming (i.e., stimulating native soil organic C decomposition) alongside enhanced negative priming. The variation in the priming effect with increasing tree diversity was associated with increased soil phosphorus availability, enhanced C stability (characterized by physical protection and chemical recalcitrance) and improved microbial network complexity. Our findings reveal a novel mechanism by which tree species diversity promotes soil C storage through dampening microbial decomposition triggered by fresh C inputs. This suppression of the priming effect suggests that diverse forests are better able to stabilize soil organic matter, highlighting the potential of biodiversity-based afforestation strategies to strengthen nature-based climate solutions.

How to cite: He, Y. and Zhou, X.: Tree species richness reduces soil carbon loss via suppressed priming effects, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-15470, https://doi.org/10.5194/egusphere-egu26-15470, 2026.

The influence of living roots on soil organic matter decomposition is termed the rhizosphere priming effect (RPE). Although root traits are critical for understanding the RPE, it is unclear how the trade-offs among root traits, exudation and mycorrhizal symbioses mediate the RPE. The RPEs of 12 grassland species were quantified using a natural ¹³C tracer method in a mesocosm experiment. Ten root functional traits were measured to examine the trade-offs among root traits, and their linkage with the RPEs. All species produced positive RPEs, with legumes and forbs showing larger RPEs than grasses. The magnitude varied from 32% to 350% compared to the unplanted soil. After accounting for root biomass effect, specific RPEs were positively correlated with specific root length, specific root surface area, root exudation rate, and specific rhizosphere respiration, while negatively correlated with root diameter and arbuscular mycorrhizal fungi colonization. These results demonstrate that plants with thinner roots show efficient root morphology and/or more exudation by inducing larger specific RPEs, while plants with thicker roots associate more with mycorrhizal symbioses and induce smaller specific RPEs. Overall, root functional traits play key roles in mediating the species-specific RPEs and have implications for predicting soil organic matter dynamics.

How to cite: Lu, J.: Rhizosphere priming on soil organic carbon decomposition: the role of root traits, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17486, https://doi.org/10.5194/egusphere-egu26-17486, 2026.

Soils represent a massive reservoir of organic matter, storing approximately three times the carbon found in the atmosphere. While over half of this soil organic carbon (SOC) is stored in subsoils below 30 cm, our understanding of its vulnerability is hindered by a major discrepancy: most field experiments utilizing top-down warming techniques show that warming rapidly attenuates with depth, whereas Earth system models (ESMs) project synchronous warming of the entire soil profile. Here, we resolve this conflict by combining a synthesis of depth-specific soil temperature measurements from 579 in-situ monitoring sites, analysis of 322 field warming experiments, and process-based modeling. The observed warming rates across depths demonstrate that ambient climate change drives nearly synchronous warming down to 3.5 m with only a slight attenuation along depth. This starkly contrasts with the strong thermal dampening recorded in field experiments using top-down warming techniques including open-top chambers, infrared heaters and heating cables. By modifying a land surface model to explicitly simulate lateral heat transfer, we show that heat loss from warmed plots to adjacent unheated soils is the primary mechanism for this attenuation in experiments. Crucially, our modeling reveals that lateral heat loss inherent in plot-scale designs leads to an average 23% underestimation of heterotrophic respiration, resulting in a 10-fold underestimation of SOC loss after 20 years. Our findings reveal a critical bias in the widely used experimental frameworks and highlight the urgent need for whole-soil warming designs to more accurately predict soil carbon-climate feedbacks.

How to cite: Chen, Y. and Zhu, D.: Near synchronous warming of deep soils reveals prevailing underestimation in soil carbon loss in warming experiments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21607, https://doi.org/10.5194/egusphere-egu26-21607, 2026.

Over the past decades, soil organic carbon (SOC) in agricultural soils has shown a decreasing trend across Europe, reflecting the combined effects of management practices and climate change. Long-term field experiments offer a unique opportunity to study these effects and identify management strategies that can mitigate SOC losses under changing climatic conditions.

This contribution combines results from two long-term experiments located at the same site in Puch/Fürstenfeldbruck, Southern Germany: a compost amendment experiment (1994–2023) and a management comparison experiment (IOSDV, 1983–2021) with varying organic matter inputs and mineral nitrogen fertilization rates. Both experiments revealed a distinct SOC content decline, coinciding with a marked regional temperature rise and increased frequency of drought–rewetting cycles. Despite continuous or even increasing organic inputs, SOC contents declined in most cases, indicating climate-driven acceleration of SOC mineralization.

Across treatments, only management strategies combining multiple organic amendments (e.g., slurry, straw incorporation, and cover crops) or the application of compost can mitigate SOC loss to a certain extent. The results emphasize that improved management can buffer SOC losses and compensate enhanced decomposition processes under a warming climate.

The analysis of both long-term experiments highlights the necessity for improved agricultural management to mitigate SOC losses and maintain soil functionality in a rapidly changing climate.

How to cite: Schubert, D., Just, C., Dechow, R., Heigl, L., Offenberger, K., Diepolder, M., Kögel-Knabner, I., Ebertseder, F., Don, A., and Wiesmeier, M.: Management practices to mitigate long-term soil organic carbon losses in arable soils of Bavaria, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-138, https://doi.org/10.5194/egusphere-egu26-138, 2026.