Most prior research on cold region ecosystems has focused on the growing season, even though plant and microbial activity, and biogeochemical turnover, continue under snow cover and sub-zero temperatures – affecting plant productivity, phenology and diversity year-round. Permafrost peatlands are vital components of the northern hydrological system and act as sources of carbon, nutrients and potential contaminants to aquatic ecosystems, but such linkages between the terrestrial and aquatic domain also remain understudied. Establishing both winter baselines and responses to climate warming is critical to gain a comprehensive understanding of high latitude and Alpine ecosystems year-round, their vulnerability to climate change, and to accurately project future environmental changes.
The goal of this session is to facilitate an interdisciplinary discussion on the dynamics of cold region ecosystems under a rapidly changing climate. We aim to bring together varied perspectives from researchers working on biogeochemistry, microbiology and plant-soil processes. We welcome studies focusing on observational, experimental, remote sensing and modelling approaches to understand plant and microbial functioning, biogeochemical cycling, ecosystem disturbances, export to aquatic systems, and associated impacts during the growing season and non-growing season – emphasizing responses to changing seasonality and climatic regimes.
High Arctic peatlands are among the most remote and climate- sensitive ecosystems on Earth. While they are globally recognised as important carbon sinks, their capacity to accumulate and archive atmospheric pollutants remains underexplored. This study investigates the deposition and accumulation of trace metals in peat cores from four sites across the Canadian High Arctic (Axel Heiberg Island, Banks Island, Ellesmere Island, and Kugaaruk) to assess the influence of long- range atmospheric transport on contaminant inputs.
Peat cores were collected from wetlands and analysed using inductively coupled plasma mass spectrometry (ICP-MS) for lead (Pb), cadmium (Cd), copper (Cu), zinc (Zn), chromium (Cr), and nickel (Ni). Concentration profiles were evaluated alongside enrichment factors (EFs), calculated relative to crustal reference elements, to distinguish anthropogenic contributions from natural lithogenic sources.
Across all sites, distinct enrichment of Pb, Cd, and Zn was observed in the upper peat layers, with enrichment factors exceeding 5 at several depths, particularly on Axel Heiberg and Ellesmere Island. In contrast, Cr and Ni displayed near-crustal EF values (close to 1), suggesting primarily natural origins. The enrichment patterns for Pb and Cd indicate deposition peaks likely corresponding to periods of heightened industrial emissions in the mid- to late 20th century, consistent with known global trends in atmospheric metal fallout. The widespread detection of anthropogenic metals across geographically isolated High Arctic wetlands underscores the efficacy of long- range atmospheric transport processes in dispersing contaminants from lower- latitude industrial regions.
These findings demonstrate that Arctic peatlands serve as dual-function environmental archives: they sequester both carbon and anthropogenic pollutants over millennial timescales. However, as climate warming intensifies permafrost thaw and alters hydrological and biogeochemical conditions, these historically sequestered metals risk remobilisation into Arctic freshwater systems. Such release could have cascading effects on sensitive ecosystems and local food webs, further illustrating the interconnectedness of global human activity and polar environmental change.
By coupling concentration and enrichment factor analyses across multiple Arctic sites, this study provides the first regional- scale evidence of widespread metal enrichment in High Arctic peatlands attributable to atmospheric transport. It highlights the necessity of incorporating contaminant storage and release processes into broader models of Arctic biogeochemical cycling. Understanding how these systems mediate both carbon and pollutant fluxes under a warming climate is critical for predicting future Arctic ecosystem responses and for developing effective environmental protection strategies.
How to cite: Purdy, E., Swindles, G., Fewster, R., Roland, T., Galloway, J., Blaauw, M., Bishop, T., Yarwood, J., Shuttleworth, E., Clay, G., and Cole, B.: Evidence of long- range transport of toxic metals in High Arctic wetlands, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-378, https://doi.org/10.5194/egusphere-egu26-378, 2026.
Microbial carbon use efficiency (CUE) is a cornerstone metric for predicting soil organic carbon (SOC) storage globally. However, its predictive power in vulnerable frozen boreal forests, where physical preservation can override biological processing, remains a critical unknown. Here, we investigated the CUE-SOC relationship across the climatically sensitive permafrost transitional zone in the Greater Khingan Mountains. Our results revealed a stark dichotomy that challenges the universal applicability of this microbial efficiency–SOC paradigm. In the warmer, non-permafrost soils, microbial CUE was the primary positive driver of SOC accumulation, consistent with global patterns. Conversely, this relationship completely vanished in adjacent permafrost soils, in which SOC accumulation was decoupled from microbial efficiency and was instead overwhelmingly controlled by high retention of plant carbon residues (e.g., NDVI, particulate organic matter) and their physical cryo-preservation. This fundamental decoupling of microbial processing from soil carbon storage demonstrated that the biogeochemical rules governing SOC in much of the world do not apply in these frozen landscapes. Our findings provide critical mechanistic evidence that ecosystem carbon model must shift priority toward controls on plant inputs and physical cryo-preservation over microbial CUE to accurately forecast the fate of the vast and vulnerable northern carbon stocks in a future climate.
How to cite: Zhou, X. and Kong, T.: Decoupling of microbial carbon use efficiency from soil carbon storage in boreal forests, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17692, https://doi.org/10.5194/egusphere-egu26-17692, 2026.
Global warming and associated permafrost thaw in the Arctic raise concerns about increased greenhouse gas emissions. Nitrous oxide (N2O) is a potent greenhouse gas produced in soils, but the magnitude of N2O fluxes from permafrost regions remains highly uncertain. While high N2O emissions for nutrient-rich, bare Arctic soils have been reported, for nutrient-poor soils that dominate the region the magnitude and drivers of N2O fluxes have rarely been investigated. We present an unprecedented dataset of 1487 chamber flux observations covering three snow-free seasons in a nutrient-poor thawing permafrost peatland in northern Sweden. Our results show that this ecosystem can act as a continuous and non-negligible, albeit small, sink of N2O during the snow-free season, which has not been reported from in-situ studies before. We also discovered a continuous N2O hotspot that indicates potential for substantial N2O production and net emissions in specific areas of the peatland. Our study identifies complex controls of N2O fluxes, highlighting interactions between photosynthetically active radiation (PAR), carbon dioxide (CO2) fluxes, and other environmental factors. We show that PAR is an important but not exclusive driver, with differences in the set of drivers and shape of dependencies between light and dark conditions.
Our results underscore the non-negligible N2O fluxes in nutrient-poor Arctic soils and the presence of hot spots which may be important for the total landscape scale N2O budget. The crucial role of soil-plant-atmosphere interactions in N2O dynamics and the role of light as a driver of N2O flux may have implications for global greenhouse gas budgets and climate mitigation and should be further investigated in future studies.
How to cite: Triches, N. Y., Bolek, A., Rovamo, M., Lamprecht, R. E., Ivanova, K., Hashmi, W., Yazbeck, T., Eves, N. J., Paul, D., Virkkala, A.-M., Vesala, T., Biasi, C., Marushchak, M. E., and Göckede, M.: Between light and dark, source and sink: N2O dynamics in a subarctic, nutrient-poor permafrost peatland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11121, https://doi.org/10.5194/egusphere-egu26-11121, 2026.
In polygonal peatlands, typical of continuous permafrost, numerous small aquatic ecosystems are found in ice-wedge troughs but also in larger depressions. These ponds reflect permafrost evolution and degradation, which influences their functioning. Permafrost ice is enriched in carbon and nutrients, and its degradation leads to the transfer of Dissolved Organic Carbon (DOC), nutrients (N, P) and microorganisms to ponds. These aquatic ecosystems act as CH4 emission hotspots. An important proportion of the CH4 produced by ponds is mitigated in the water column by methanotrophic activity. We refer to the hydrological and biological exchange between permafrost pore ice and aquatic ecosystems, which is driven by ongoing permafrost degradation, as permafrost-pond connectivity. The effects of permafrost-ponds connectivity on microbial communities and CH4 oxidation activity remain to be assessed, to understand how permafrost degradation could influence future Greenhouse Gas (GHG) fluxes of polygonal peatland.
In this study, we combined in situ monitoring and incubation approach of small ponds of polygonal peatlands. Study sites were located near Churchill (Manitoba, Canada) and across Wapusk National Park, in the Hudson Bay lowlands, the second largest complex of permafrost peatland in the world. To investigate the diversity and functioning of aquatic ecosystems, we characterised GHG concentration and fluxes, organic carbon, nutrient concentrations and microbial communities, in and around forty waterbodies covering a large range of permafrost degradation context, from small trough ponds to larger depressions. Additionally, we tested the effect of permafrost-pond connectivity on CH4 oxidation activity in an experimental setting by adding inorganic nutrients (N, P) or permafrost pore ice into methanotrophic incubations of pond water. Ponds selected for these experiments covered a range of different permafrost connectivity context.
We found that the degree of connectivity between permafrost ice and ponds strongly structures their microbial community composition, nutrient content and CH4 mitigation potential. Higher connectivity to permafrost leads to higher DOC and Total Phosphorous (TP) content, whereas lower [CH4] were measured. Nutrient transfer affected CH4 oxidation activity in different ways in methanotrophic experiments. Synthetic NP inputs increased CH4 oxidation activity. On the other hand, permafrost pore ice transfer led to strong decrease of CH4 oxidation activity. Labile DOC and nutrients contained in permafrost pore ice increased heterotrophic activity and competition for O2. Ponds with low connectivity to permafrost (influenced by the active layer) were more sensitive to nutrient inputs than the ponds highly connected with permafrost. These results suggest that methanotrophic activity could be less nutrient-limited as a result of higher nutrient input from permafrost to ponds. These results show that nutrient transfer from permafrost alters CH4 mitigation activity and influences CH4 emissions from aquatic ecosystems in a polygonal peatland context. This study provides new insights into understanding biogeochemical processes and estimating permafrost thaw positive feedback to climate change.
How to cite: Trémouille, R., Barret, M., Allain, A., Arsenault, J., Bouchard, F., Coquereau, G., Germain, L., Vivant, M., and Gandois, L.: Permafrost degradation inputs shape mitigation potential of methane emissions from aquatic ecosystems in a polygonal peatland context, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12212, https://doi.org/10.5194/egusphere-egu26-12212, 2026.
Permafrost thaw in subarctic peatlands alters ecosystem methane (CH4) fluxes. Collapsing permafrost peat plateaus (palsas) change soil hydrology, oxygen availability, and vegetation composition, and each of these factors contribute to net CH4 flux by influencing CH4 production, consumption and transport. However, changes in plant-mediated CH4 fluxes have mostly been estimated with aboveground characteristics, such as biomass and leaf area, leaving belowground parts (roots and rhizomes) understudied despite their direct contact to depth-dependent CH4 flux processes. Here, we explored the potential of using root and rhizome traits as proxies for plant-mediated CH4 cycling along a peatland permafrost thaw gradient in subarctic Sweden. We investigated changes in plant belowground traits along the thaw gradient and the relationships between root and rhizome biomass, surface area (SA), diameter, tissue density (TD), and specific root length (SRL), and early, middle, peak and season median CH4 fluxes by utilizing chamber CH4 flux and pore water CH4 concentration and isotopic measurements during the productive season. Shrub SRL, diameter and isotopic data suggested increased plant-mediated carbon substrates for acetoclastic methanogenesis along the thaw gradient. Root TD (root porosity proxy) decreased with thaw and had negative correlations with CH4 fluxes throughout the season, and together with positive herbaceous rhizome SA-CH4 flux associations and lower pore water CH4 concentrations in the fully thawed stage. These results indicated increasing herbaceous plant-mediated transport of acetoclastically-produced CH4 with thaw. Altogether, while confirming previous findings of increased plant-mediated acetoclastic methanogenesis with thaw, this study also demonstrated the benefit of belowground traits in revealing new aspects of plant-mediated CH4 cycling in permafrost peatlands.
How to cite: Määttä, T., Kallingal, J. T., Bosman, S., Chanton, J., Hodgkins, S., Wilson, R., Varner, R., and Malhotra, A.: Plant belowground traits reflect increased plant-mediated methane transport along a peatland permafrost thaw gradient, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17197, https://doi.org/10.5194/egusphere-egu26-17197, 2026.
Seasonal snow cover plays a critical role in regulating soil freeze-thaw dynamics by forming an insulating layer on top of the soil and modifying the soil thermal regime in high latitude regions. In natural wetlands, which have a significant contribution to global methane (CH4) emissions and are sensitive to rising surface temperatures, snow cover influences the seasonality and magnitude of these emissions. Despite its importance, snow-soil-atmosphere interactions remain a major source of uncertainty in current land surface models, particularly with respect to methane dynamics during the cold season. The net methane flux is regulated by the processes of CH4 production, oxidation, and transport, with methane transported from the soil to the atmosphere via diffusion, ebullition and plant-mediated transport. Snowpack slows down the diffusion of methane and high emissions can occur during spring snow melt and soil thaw.
In this study, we utilize the JSBACH ecosystem model and run it coupled with the HIMMELI peatland process model with a novel snow resistance implementation to assess how snowpack modifies the methane microbe and transport processes in high-latitude peatlands. The model framework is forced, calibrated and evaluated using observational data from an established pristine mire eddy covariance (EC) measurement site located in northern Finland within the Arctic-boreal region. Simulated methane fluxes and snow dynamics are compared against EC, chamber, and snowpack CH4 diffusion gradient observations in addition to manual and automated observations of snow properties. Our preliminary results indicate that the snowpack impacts the soil freeze/thaw, anoxic conditions, methane concentrations and plant-mediated transport, therefore demonstrating the complex and non-linear relationship between seasonal snow cover and methane production, transport and oxidation processes.
How to cite: Orttenvuori, S., Leppänen, A., Markkanen, T., Aurela, M., Kontu, A., Lemmetyinen, J., Männikkö, M., Raivonen, M., and Aalto, T.: Understanding how snow cover controls methane emissions in high-latitude peatlands through ecosystem modeling, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12456, https://doi.org/10.5194/egusphere-egu26-12456, 2026.
Global warming accelerates the breakdown of carbon stored in permafrost regions, releasing it into the atmosphere and amplifying climate change, particularly during winter when photosynthesis ceases. The Northern Hemisphere's permafrost is primarily concentrated in two key regions — the Arctic and the Tibetan Plateau — each with distinct environmental characteristics. However, previous studies often treat these regions separately, missing the opportunity to compare their winter CO2 emissions within a unified framework. Here, we synthesized 2,487 monthly CO2 flux measurements from 166 in-situ sites to quantify the spatial and temporal variations and key drivers of winter CO2 emissions in these two regions. Our analysis reveals that combined winter emissions from the Arctic and Tibetan Plateau are estimated to be 1,289 ± 25 Tg C yr-1. From 1982 to 2022, winter CO2 emissions increased by 2.10 ± 0.23 Tg C yr-1. Notably, since 2001, winter CO2 emissions have surged in the Arctic while declining in the Tibetan Plateau. The driving factors also differ: soil temperature dominates in the Arctic (51%), whereas soil moisture plays the most significant role on the Tibetan Plateau (33%). These findings highlight the contrasting mechanisms governing winter carbon emissions in these regions and underscore the importance of incorporating region-specific factors when predicting permafrost-carbon feedbacks in a warming world.
How to cite: Wei, Y., Mu, C., Chen, D., Mo, X., Elberling, B., Zhang, W., Zhang, G., Zhang, C., Li, K., Li, X., Shi, M., Mu, M., Wang, X., Wei, D., Dou, T., Du, X., Peng, X., Jin, Y., Xiao, J., and Ciais, P.: Global warming driving increased winter CO2 emissions in the Northern Hemisphere permafrost region, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20267, https://doi.org/10.5194/egusphere-egu26-20267, 2026.
In recent decades, the temperature and precipitation patterns in Arctic ecosystems have been highly affected by climate change. Previous studies suggest that changing air circulation and more evaporation from ice-free Arctic seas could increase snowfall and winter snow accumulation in parts of the Arctic, which in turn can change the onset of the growing season. In combination with ongoing and projected temperature rise, such shifts will alter the physical and biogeochemical processes that are associated with soil respiration and production/release of greenhouse gases like CO2 from Arctic tundra soils.
Arctic tundra soils experience strong seasonal hydrological dynamics, ranging from frozen conditions in winter to near water saturated and partially water saturated conditions following snowmelt infiltration in early spring. These conditions exert controls (i) on the transport behavior and delivery of O2 into the soil, (ii) on the kinetics of soil respiration and (iii) on the release of CO2 to the atmosphere. Despite the importance of these complex interactions for Earth’s climate, there is still a considerable limitation on the accurate quantification of the interplay between thermo-hydrological, transport and microbial respiration in controlling CO2 emissions from tundra ecosystems under transient field conditions.
We investigated how physical and biogeochemical processes, including oxygen transport, soil respiration and CO2 emissions respond to seasonal thermo-hydrological dynamics in a typical well-drained Arctic tundra ecosystems by combining lab experiments and field observations with process-based modelling. Our results show that respiration and CO₂ emissions are strongly constrained by low temperatures during most of the year as oxygen concentration remains close to atmospheric levels and therefore oxygen availability is not a limiting factor. The onset of spring is accompanied by a gradual increase in temperature and melting of snowpack, which reduces the thermal limitation on soil respiration. However, the resulting snowmelt infiltration exerts a series of biochemical and physical controls on soil respiration dynamics and CO2 emission by (i) inducing water saturated conditions in soil; (ii) limiting oxygen transport into the soil and CO2 migration toward the atmosphere due to slow gas diffusivity in water and (iii) reducing oxygen concentration to values close to half saturation constant of oxygen, thereby exerting metabolic constrains. These results highlight the importance of considering the impact of climate forcing (e.g., thermal and hydrological dynamics) on physical and biogeochemical processes that regulate carbon dynamics in Arctic tundra ecosystems.
How to cite: Ahmadi, N., Kortegaard Danielsen, B., Schurgers, G., Deepagoda, C., Rinnan, R., Nordberg Nilsson, K., and Elberling, B.: Thermal and hydrological controls on subsurface gas transport and soil respiration in Arctic tundra ecosystems, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14046, https://doi.org/10.5194/egusphere-egu26-14046, 2026.
The snow cover changes driven by climate change are profoundly altering the structure and function of alpine ecosystems. Based on a review of the effects of snowpack variation on soil processes in terrestrial ecosystems of the Northern Hemisphere (with the most significant soil insulation effect observed at snow depths of 40-70 cm; increased snow cover accelerates carbon and nitrogen cycling, leading to their loss, with more pronounced effects in moist habitats), this study, combined with snow cover manipulation experiments in the alpine meadows of the Tibetan Plateau, focuses on examining the response of plant above-ground and below-ground functional traits to increased snow depth. The study found that increased snow depth significantly improved the water-thermal conditions of the shallow soil during the growing season, which in turn drove an "inconsistent response" in plant above-ground and below-ground parts: while there was no significant change in above-ground biomass, leaf chemical traits (carbon, nitrogen, and phosphorus concentrations) were significantly enhanced, and morphological traits (such as specific leaf area) decreased. In contrast, root biomass in the below-ground part increased significantly, and root morphology was significantly optimized (specific root length and specific root area increased, root diameter decreased). Further analysis indicated that variation in leaf traits was primarily driven by nutrient chemical properties, whereas variation in root traits was predominantly influenced by morphological adjustments. The sensitivity of below-ground processes in the alpine meadows to snowpack variation was higher than that of the above-ground processes. This differential response strategy reflects the trade-offs between above-ground and below-ground resource allocation, highlighting the adaptive strategy of alpine plants to prioritize root investment for enhanced resource acquisition under changing snow conditions. This study deepens the understanding of the cascading mechanisms of snow-soil-plant interactions and provides a theoretical basis for predicting the feedback of alpine meadow ecosystems to climate change.
How to cite: Tan, X. and Yang, Y.: Changes in Snow Cover and Underground Ecosystems in the Northern Hemisphere, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-285, https://doi.org/10.5194/egusphere-egu26-285, 2026.
The cryosphere hosts diverse microbial communities adapted to steep temperature gradients, low water availability, and prolonged darkness. Despite evidence for sub-zero metabolic activity and long-term survival in ice cores, winter microbial ecology, particularly during the polar night, remains poorly constrained, with most studies focused on sunlit seasons. This has led to an incomplete, photosynthesis-centric view of polar ecosystem function, leaving open whether winter represents a period of dormancy or sustained metabolic activity. Here, we present the first multi-habitat metagenomic and metatranscriptomic study of High Arctic (79°N) microbial communities from glacier ice, snow, lake ice, and soils, sampled during mid-polar night. We examine transcriptional and translational activity to test for winter metabolic function, identify active taxa and pathways, and assess habitat-specific strategies. We evaluate how nutrient availability constrains winter metabolism and whether low-abundance taxa contribute disproportionately to activity. Our results indicate that cryospheric microbial communities maintain diverse metabolic functions throughout the polar night, redefining winter as a dynamic biogeochemical period with implications for Arctic ecosystem processes under changing climate.
How to cite: Larose, C., Singh, H., Bradley, J. A., and Vogel, T. M.: Winter Metabolism in the High Arctic: A Multi-Habitat Metatranscriptomic Perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12726, https://doi.org/10.5194/egusphere-egu26-12726, 2026.
We conducted, to our knowledge, the first multi-decadal, peatland-specific assessment of canopy greening and browning trends across northern peatlands using a gap-filled, sensor-independent climate data record of leaf area index (LAI) for 2001–2023. We hypothesise that northern peatlands exhibit spatially coherent greening or browning trends in LAI and that these trends can be explained by (i) climate-related changes, including warming, precipitation and recent lake drainage in the northern permafrost zone; (ii) differences in protection status; and (iii) variation in tree cover type and density. We found that although greening was widespread (77% of peatlands; greening-to-browning ratio 3.5:1), there was no statistical evidence for an area-weighted LAI trend at the map scale. Overall, peatland canopy change was not a uniform increase in greenness; rather, LAI responses were moisture-sensitive and dependent on tree-cover context and were further modulated by decadal climate variability.
How to cite: Burdun, I., Pu, J., Myneni, R. B., and Rautiainen, M.: Beyond greening and browning in northern peatlands: the roles of warming, precipitation, lake drainage, and tree cover, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-239, https://doi.org/10.5194/egusphere-egu26-239, 2026.
Submarine groundwater discharge (SGD) can deliver land-sourced chemicals to coastal waters, influencing coastal biogeochemistry and ecosystems. In cold regions, submarine groundwater discharge commonly occurs under seasonal freeze-thaw conditions, but how freeze-thaw processes affect SGD in coastal unconfined aquifers remains unclear. This study examines the fluctuation of water efflux in coastal aquifers under seasonal freeze-thaw conditions, based on a two-dimensional conceptual model. Simulations were conducted using a modified SUTRA-MS model that incorporates freeze-thaw processes into variably saturated, density-dependent groundwater flow coupled with salt and heat transport. The response of frozen layer thickness and SGD to seasonal freeze-thaw will be discussed here in detail.
How to cite: Yu, X., Li, Y., and Xin, P.: Seasonal freeze-thaw effects on submarine groundwater discharge in coastal unconfined aquifers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2070, https://doi.org/10.5194/egusphere-egu26-2070, 2026.
Plant-microbe symbiotic relationships are critical for ecosystem stability and functional maintenance, particularly in extreme alpine ecosystems. Takakia lepidozioides, one of the most primitive moss species in the world, has unclear mechanisms of interaction with microbes. This study focused on T. lepidozioides distributed along an altitudinal gradient (3800-4200 m) on Galongla Snow Mountain in southeastern Tibet. Through in situ field sampling, 16S rRNA and ITS amplicon sequencing were used to analyze microbial community structures in the rhizoidsphere and endophyte compartments, combined with metagenomic sequencing to examine functional characteristics. The study systematically investigated the T. lepidozioides-microbe symbiotic system and its cooperative adaptation mechanisms to alpine environments. Key findings are as follows:
(1) Significant differences existed between rhizoidsphere soil bacteria and endophytic bacteria in community composition, diversity, network structure, and assembly processes, with relatively smaller differences in fungi; altitude had no significant effect on symbiotic microbes (rhizoidsphere and endophyte), but they were influenced to some extent by physicochemical properties;
(2) Symbiotic microbes potentially assisted the host in basic element cycling, immunity, and antioxidant production, while supplementing indole-3-acetic acid synthesis pathways; symbiotic microbes relied on ABC transporters for N/S/P/Fe(III) transport but lacked transporters for sugars, organic acids/aromatics, metals/partial vitamins, amino acids, and defense-related proteins; endophytes contributed to host growth and stress resistance through enhanced amino acid metabolism, energy flow, terpenoid precursors, and carotenoid precursor synthesis compared to rhizoidsphere microbes;
(3) The symbiotic compartment contained many novel microbes (unclassifiable to species level by GTDB-Tk); endophytic metabolic modules were more diverse than those in the rhizoidsphere; endophytes exhibited pronounced community-function decoupling, with more frequent horizontal gene transfer events, consistent with weaker selection processes in endophytes.
In summary, this study revealed the roles of rhizoidsphere and endophytic microbes in supporting T. lepidozioidessurvival at the community and functional levels, providing the first comprehensive analysis of potential T. lepidozioides-microbe symbiotic relationships. These findings have significant implications for understanding early patterns of plant-microbe cooperative adaptation to extreme environments and for conserving endangered species.
How to cite: Liu, W. and Wei, Y.: Symbiotic strategy of endophytic-rhizoidsphere microbiome with Takakia lepidozioides in alpine mountain of Tibetan Plateau, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4937, https://doi.org/10.5194/egusphere-egu26-4937, 2026.
Estimating the carbon balance of Arctic ecosystems is challenging because of their high spatial heterogeneity, which is difficult to account for using traditional methods: static chambers linked to fixed points allow for tracking the seasonal dynamics of processes but are limited in spatial coverage, whereas the Eddy Covariance method provides only an integral assessment of fluxes from large areas, averaging the contribution of various microlandscapes.
In this work, we present the results of a STORDALENX25 field campaign conducted during the 2025 growing season at Stordalen Mire (Abisko, Sweden), during which over 650 measurements of CH4 and CO2 (NEE) fluxes were obtained using the mobile chamber technique, quasi-randomly distributed within and beyond the Eddy Covariance footprint, covering a total area of approximately 0.1 km2. The unique density of this spatial dataset allows it to be used not only for calculating the regional budget but also as a testbed for evaluating various spatial upscaling strategies.
As a first key methodological task, we compare the effectiveness of different base maps describing the study domain: we contrast classical upscaling based on land cover types (Palsa, Fen, Bog) with the use of data-driven functional zonation. Another research objective is to determine the factors contributing most to model accuracy: we conduct a comparative analysis of predictors, assessing the "value added" by remote sensing data (Sentinel-2, UAV) compared to direct field measurements such as soil temperature and moisture. Furthermore, we analyze the "performance plateau" to identify the minimum necessary number of measurement points and compare the efficiency of classical vegetation-based scaling against clustering based on environmental response functions. The results, validated by data from static chambers and the Eddy Covariance tower, allow for the optimization of future field campaign designs by determining the balance between labor effort and the accuracy of spatial estimates.
How to cite: Ivanova, K., Bolek, A., Eves, N. J., Heimann, M., Kanakassery, S. B., Oxley, L., Pratt, E., Schlutow, M., Triches, N., Vogt, J., Wahl, E., Yazbeck, T., Widhalm, B., Bartsch, A., and Göckede, M.: Evaluating spatial upscaling strategies for Arctic carbon fluxes: high-density mobile chamber measurements at Stordalen Mire, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8163, https://doi.org/10.5194/egusphere-egu26-8163, 2026.
Trees growing in mountain regions have evolved adaptations to withstand extreme winter conditions, primarily through dormancy and frost-avoidance mechanisms. However, frost events occurring after the growing season begins pose a substantial risk, as ice formation can damage newly developing tissues. A warm episode in late winter or early spring that triggers premature growth, followed by a subsequent hard freeze, is termed a false spring.
In the alpine treeline ecotone in the High Tatras, Pinus cembra, a native, long-lived mountain conifer, experienced such a false spring in 2024. Weather conditions in late winter led to an unusually early bursting of vegetative buds, which was interrupted by an 11-day cold spell. During this period, minimum air temperatures dropped to −8.3 °C, with a mean daily temperature of −2.0 °C, as recorded at the Skalnaté Pleso Observatory (1778 m a.s.l.). This freezing event occurred shortly after vegetative buds had lost their protective resin layer and begun to burst. The aim of this study was to assess the impact of this event on the life cycle of P. cembra.
In the weeks following the false spring, affected individuals exhibited pronounced needle yellowing and defoliation. While senescence and shedding of older needles typically occur between August and September, frost-induced stress led to the premature loss of approximately one-third of needles as early as May, at the beginning of the growing season. Although new shoots and needles developed normally, reproductive organs were severely affected. Cone bud formation was observed approximately two months after vegetative budburst; however, male (pollen) cones were degenerated and showed minimal pollination potential. Following the false spring, P. cembra individuals developed several seed cones, which subsequently abscised between July and August 2025. These cones were immature, small, and deformed.
Our results demonstrate that false spring events associated with ongoing climate change can disrupt the life cycles of P. cemba, substantially limiting its reproductive potential in the alpine treeline ecotone of the High Tatras.
Acknowledgement: This study was funded by the project VEGA 2/0048/25.
How to cite: Lukasová, V., Varšová, S., and Škvarenina, J.: Negative effects of false spring on P. cembra in the alpine treeline ecotone of the High Tatras, Slovakia, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10758, https://doi.org/10.5194/egusphere-egu26-10758, 2026.
Carbon exchange in Arctic ecosystems shows strong seasonality, yet winter processes remain poorly constrained despite their potential importance for annual carbon budgets. In permafrost regions, CO₂ produced in the active layer during late summer and autumn may accumulate beneath frozen soil and snow cover, when gas diffusion to the atmosphere is restricted. Observed wintertime increases in subsurface CO₂ concentrations therefore raise the question of whether they primarily reflect reduced diffusivity or enhanced CO₂ production under relatively warm subnival conditions.
We combined year-round eddy covariance measurements of ecosystem CO₂ exchange, growing-season chamber flux observations, and winter subsurface CO₂ concentration profiles from an Arctic heath ecosystem on Disko Island, West Greenland, to constrain the process-based CoupModel. The model represents soil CO₂ production and transport as functions of soil temperature, moisture, air-filled porosity, and CO₂ concentration, allowing winter physical controls on gas diffusion to be explicitly evaluated.
The calibrated model reproduces observed vertical soil CO₂ concentration patterns between 10 and 80 cm depth as well as the seasonal dynamics of ecosystem CO₂ fluxes. Simulations indicate that elevated winter subsurface CO₂ concentrations are largely explained by reduced gas diffusivity in frozen and snow-covered soils, while the direct influence of high CO₂ concentrations on production rates is limited. Laboratory measurements of CO₂ diffusion under frozen and unfrozen conditions support the strong sensitivity of gas transport to changes in air-filled porosity.
Interannual variability in snow conditions exerts a strong control on non-growing-season CO₂ emissions. Winters with unusually deep snowpacks show substantially higher CO₂ efflux, reducing the annual net CO₂ sink. In contrast, warmer and wetter growing seasons enhance both gross primary production and ecosystem respiration, partially compensating for increased winter losses. These results underline the importance of winter soil physical processes for Arctic carbon dynamics and illustrate how combining observations with process-based modelling can improve estimates of year-round CO₂ exchange.
How to cite: Zhang, W., Danielsen, B., and Elberling, B.: Modeling year-round CO₂ fluxes and winter subsurface CO₂ dynamics in an Arctic heath ecosystem, West Greenland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21349, https://doi.org/10.5194/egusphere-egu26-21349, 2026.
Spring and autumn, often termed shoulder seasons, represent key transitional phases in Arctic tundra ecosystems, during which nutrient dynamics become highly variable. Biogeochemical cycling during these periods is particularly responsive to warming. Here, we quantify nitrogen uptake and allocation across soil, plant, and microbial fractions in tundra ecosystem at Abisko, northern Sweden, where experimental warming has been maintained for 7 and 17 years, alongside ambient controls. A dual-labeled ¹³C¹⁵N-glycine tracer was used to trace nitrogen incorporation over short-term (24 h) and longer-term (one month) timescales. Isotope recovery across ecosystem pools will be used to determine how warming duration alters the partitioning of nitrogen during seasonal transitions. Based on fieldwork completed last year, this work reports preliminary results from ongoing analyses, with only a limited number of initial findings presented. Once analyses are complete, the results will contribute to improve our understanding of nitrogen dynamics during transition periods under warming in Arctic tundra ecosystems.
How to cite: Jung, J. Y., Andersen, E. A. S., Jeong, S., Nam, S., Kim, J., Jeon, J., and Michelsen, A.: Effects of Long-Term Experimental Warming on Nitrogen Uptake and Partitioning During Arctic Tundra Shoulder Seasons, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16383, https://doi.org/10.5194/egusphere-egu26-16383, 2026.
Snow cover strongly affects Arctic tundra soils, regulating temperature, moisture, and nutrient availability across seasons. Although warming increases winter snowfall and prolongs snow cover, the biogeochemical impacts remain uncertain in contrasting tundra types. We installed snow fences in moist tundra (Council, Alaska) and dry tundra (Cambridge Bay, Nunavut) for five to six years to assess how deeper snow cover modifies soil conditions, biological activity, and soil organic matter (SOM) fractions, focusing on mineral-associated organic matter (MAOM). Deeper snow cover raised winter soil temperatures at both sites. However, only the moist tundra showed higher summer soil temperature and moisture, leading to higher plant greenness and a slight rise in SOM vulnerability. At this site, free particulate organic matter fraction rose while MAOM declined, indicating that MAOM, less chemically processed (high C/N, low δ¹⁵N), was more susceptible to decomposition. In contrast, the dry tundra’s colder conditions showed no major shifts in soil chemistry, vegetation, microbes, or SOM fractions, likely because temperatures stayed below thresholds for winter biological activity. These site-specific results indicate that soil temperature and moisture drive Arctic tundra responses to deeper snow cover, highlighting the importance of understanding such differences when predicting biogeochemical feedback under rapid climate change.
How to cite: Kim, J., Kim, Y. J., Jung, J. Y., Nam, S., and Jeong, S.: Divergent ecosystem responses: Biological activity and soil organic matter vulnerability under increased snow depth in Arctic tundra, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16767, https://doi.org/10.5194/egusphere-egu26-16767, 2026.
Recent climate warming in the Arctic is driving accelerated permafrost degradation (Biskaborn et al., 2019), representing one of the most severe consequences of contemporary climate change (Rantanen et al., 2022; Schuur et al., 2022), with profound impacts on terrestrial ecosystems and the global climate system (Calvin et al., 2023). Although Arctic greening has been widely documented, ecosystem responses remain spatially heterogeneous and include both vegetation expansion and degradation (Kropp et al., 2025; Frost et al., 2025).
The aim of our study is to investigate the spatial patterns of Arctic ecosystem dynamics over the past four decades in relation to recent climate warming and permafrost degradation, using multi-temporal satellite observations and spatial analysis techniques. Time series of satellite-derived vegetation (NDVI, GNDVI, SAVI, MSAVI, EVI) and water indices (NDWI, AWEIsh) from Landsat (1984–2025) and MODIS (2000-2025) were analyzed to identify trends and anomalies in vegetation productivity and surface water dynamics. The analysis was conducted using a reproducible workflow based on the Microsoft Planetary Computer STAC and automated Python scrips, enabling efficient data extraction and consistent processing across temporal and spatial scales.
Results reveal widespread greening across large areas of the Arctic tundra, with a general increase up to 0.03 – 0.04 in vegetation indices. However, localized browning and declining vegetation are observed in areas affected by permafrost thaw, surface subsidence, and altered hydrological regimes. Contrasting patterns are also revealed by water indices, with increasing values indicating the formation of new lakes, and decreasing values associated with drainage or vegetation encroachment. These patterns highlight strong spatial linkages between climate warming, permafrost dynamics, and ecosystem response.
Overall, this study emphasizes that Arctic ecosystem change is characterized by complex and heterogenous trend and underscores the importance of spatially explicit monitoring frameworks for assessing Arctic ecosystem vulnerability and resilience under ongoing climate change.
Acknowledgement
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No. 101086386, EO-PERSIST - A Cloud-Based Remote Sensing Data System for Promoting Research and Socioeconomic Studies In Arctic Environments (https://www.eo-persist.eu).
References
- Biskaborn et al. (2019). Permafrost is warming at a global scale. Nature Communications, 10(1), 264. https://doi.org/10.1038/s41467-018-08240-4
- Calvin et al. (2023). IPCC, 2023: Climate Change 2023: Synthesis Report. Contribution of Working Groups I, II and III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Core Writing Team, H. Lee and J. Romero (eds.)]. IPCC, Geneva, Switzerland. (First). Intergovernmental Panel on Climate Change (IPCC). https://doi.org/10.59327/IPCC/AR6-9789291691647
- Frost, G. V. et al. (2025). The changing face of the Arctic: Four decades of greening and implications for tundra ecosystems. Frontiers in Environmental Science, 13. https://doi.org/10.3389/fenvs.2025.1525574
- Kropp, H. et al. (2025). Heterogeneous long-term changes in larch forest and shrubland cover in the Kolyma lowland are not captured by coarser-scale greening trends. Environmental Research: Ecology, 4(1), 015002. https://doi.org/10.1088/2752-664X/ada8b1
- Rantanen et al. (2022). The Arctic has warmed nearly four times faster than the globe since 1979. Communications Earth & Environment, 3(1), 168. https://doi.org/10.1038/s43247-022-00498-3
How to cite: Vîrghileanu, M., Daia-Creinicean, T., Berbecariu, A., Bizdadea, C.-G., Miron, F., and Șandric, I.: Spatial patterns of Arctic ecosystem changes under recent climate warming and permafrost degradation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16981, https://doi.org/10.5194/egusphere-egu26-16981, 2026.
As scientists continue to better understand climate change, it is becoming increasingly apparent that ecosystems around the polar regions are warming at an accelerating rate. This poses a particular problem for climate-sensitive ecosystems, particularly permafrost peatlands. Permafrost peatlands are an exceptionally important ecosystem for carbon storage. representing ~45% of soil organic carbon in northern peatlands; however, as cooler conditions are imperative for preserving carbon-rich permafrost sediment, these peatlands are extremely vulnerable to warming. Degradation of permafrost peatlands could be damaging, as thawing permafrost turns the ecosystem into a source of carbon dioxide (CO2), and subsequent waterlogging of the surface can increase methane. The long-term effects of permafrost degradation remain uncertain; as warming trends continue, permafrost thaw is expected to create a positive feedback loop which would further accelerate climate change. However, thawed permafrost peatlands also have the potential to create a negative feedback loop; productivity and peat/carbon accumulation rates can benefit from the increased nutrient availability and the proliferation of wetland habitats resulting from thawed permafrost.
The focus of this study is Šuoššjávri, a palsa mire located in northern Norway, within the discontinuous permafrost zone. Our project aims to assess the formation/collapse of palsas, their relationships with fire regimes and climate change, and their impacts on in-situ vegetation and carbon storage. We collected three peat cores in a ~10m transect from the top of a palsa to a thermokarst pond, around 3m apart. These cores were analysed using multiple palaeoecological proxies at high resolution (1 cm contiguous samples), to reconstruct past fire frequency, vegetation, hydrological change, and carbon storage over the past ~5000 years.
We hypothesise that (1) regional climatic warming has accelerated palsa degradation at Šuoššjávri, expressed through coupled shifts in ground subsidence, hydrological regime, vegetation composition, and a long-term decline in carbon accumulation; (2) hydrological reorganisation, reconstructed from plant macrofossils and peat physicochemical properties, is the dominant mechanism controlling vegetation succession during palsa destabilisation and collapse; and (3) early warning signals of an approaching critical transition—manifested as local wetting, directional vegetation change, and transient increases in carbon accumulation—systematically precede major palsa collapse events in the palaeoecological record.
This study is funded by NCN project no. 2021/41/B/ST10/00060
How to cite: Roberts, H., Słowiński, M., Marcisz, K., Kołaczek, P., Coathup, D., Lyngstad, A., Kucharzyk, J., Grygoruk, M., and Lamentowicz, M.: Permafrost peatland dynamics during the Holocene: evidence of palsa transformation at Šuoššjávri, northern Norway, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21405, https://doi.org/10.5194/egusphere-egu26-21405, 2026.
