Streptomyces kryoterrae sp. nov. and Streptomyces yamdrokensis sp. nov., two novel actinobacteria isolated from the Qinghai-Tibet Plateau.

Drained thermokarst (thaw) lakes of permafrost regions represent potentially important but poorly constrained hot spots of greenhouse gas (GHG), carbon, and nutrient cycling. To elucidate the biogeochemistry of residual water bodies (RWB) formed after thermokarst lake drainage in permafrost peatlands, we measured dissolved CO₂ and CH₄ concentrations, CO₂ emissions, and dissolved (<0.45μm) carbon, major, and trace element concentrations in the continuous and discontinuous permafrost zones of the Western Siberian Lowlands. Residual water bodies located within drained lake basins were examined across early and late successional stages. Carbon dioxide emissions from RWB surfaces ranged from 0.1 to 2.0g C-CO₂ m-2 d-1 and did not exhibit systematic variation with successional stage or permafrost zone. In contrast, dissolved CO2 (200-1200μmolL-1) and CH4 (1-30μmolL-1) concentrations followed a consistent pattern of "Early stage > Late stage > Lake." Partial mismatch between dissolved CO₂ concentrations and CO₂ fluxes arises because concentrations integrate longer-term biogeochemical processes, whereas fluxes respond to short-term physical controls on gas exchange. The isotopic composition of dissolved inorganic carbon (δ13C-DIC; -14 to -28‰) indicated dominant DIC production from terrestrial organic matter (plants and peat), with additional contributions from in-lake biogeochemical processing and gas exchange. Labile and highly soluble components of lake water-including DIC, major ions (Na, Mg, Ca, Cl), nutrients (P, K, Si), redox-sensitive elements (Fe, Mn), and several trace elements (Co, Ni, Sr, Rb, Mo, As)-showed similar stage-dependent decreases in concentration. This pattern is attributed to intensive biogeochemical cycling driven by vegetation establishment and nutrient uptake on drained lake bottoms. In contrast, low-solubility lithogenic elements and several trace metals (e.g., Cr, V, Cu, Zn, Pb) showed no consistent successional trend, and in some cases increased from early to late stages, suggesting inputs from mineral sources via suprapermafrost inflow. Overall, residual water bodies formed after thermokarst lake drainage differ markedly from mature lakes in their carbon, GHG, and solute composition. Their biogeochemistry is primarily regulated by terrestrial vegetation succession and peat soil inputs, highlighting drained thermokarst lakes as critical yet underrepresented hot spots in Pan-Arctic carbon and nutrient cycling under ongoing climate warming.

Spatiotemporal variations in radiocarbon age of freshwater organic carbon in the Northern Hemisphere cryosphere: Mechanisms and implications.

Abstract Near‐surface seismic refraction tomography is a powerful tool for imaging shallow subsurface structures, yet conventional approaches often fail to resolve sharp velocity contrasts at geological interfaces due to inherent smoothness constraints. We present a hybrid methodology that combines Hagedoorn's Plus–Minus ( T ±) method with refraction tomography, constructing geologically plausible 2D starting models with predefined interfaces to overcome these limitations. Validation through synthetic benchmarks and field applications—performed with identical iteration counts and inversion parameters for fair comparison—demonstrates consistent superiority in scenarios involving abrupt velocity transitions (permafrost boundaries, water tables and bedrock interfaces). Synthetic tests show that although conventional tomography fails to recover plausible models for interfaces with significant topography, the hybrid approach accurately resolves both interface geometries and velocity distributions. Field applications confirm these advantages. In a hydrological survey, the method delineated horizontal water tables at 5.2 ± 1.0 m depth versus smooth, non‐physical solutions from conventional tomography. In Alpine permafrost zones, it resolved extreme lateral velocity contrasts (such as 2.1–5.3 km/s at 20 m depth) while maintaining inversion stability. This work establishes a practical and robust workflow for generating geologically constrained starting models directly from refraction data, significantly advancing the resolution of sharp interfaces in near‐surface seismic tomography for both academic and industrial applications.

Introduction. The construction of civil buildings in permafrost areas is accompanied by risks associated with the formation of a thawing bowl at the base. Materials and methods. Numerical modeling of the "building – foundation – base" system under seismic impacts of various frequency compositions has been performed. Aim. Assessment of the impact of the thawing bowl on the earthquake resistance of civil buildings with various structural systems, taking into account seismic impacts of various frequency compositions. Results. It has been established that the presence of a thawing bowl changes the dynamic behavior of a building depending on its structural system and the frequency characteristics of an earthquake. The most pronounced increase in horizontal displacements is observed for medium–rigid and flexible structural systems in the low- and medium-frequency range, while rigid frameless systems maintain a more stable behavior. Conclusions. The results show that when calculating seismic impacts in permafrost conditions, it is necessary to consider the integral system "building–foundation–base". Taking into account the joint work of the structure and the thawing ground allows for a more accurate assessment of the seismic response of buildings with various structural systems.

Abstract The transformation of permafrost-derived dissolved organic carbon (DOC) to CO 2 is mediated by interacting photodegradation and biodegradation processes that influence DOC lability and persistence in Arctic aquatic systems. Here, we experimentally evaluated the relative roles of photodegradation and biodegradation pathways on DOC concentration and age along a hydrologic continuum from soil pore water to a first-order stream to a second-order stream draining permafrost soils during spring freshet. Spring freshet is characterized by pulses of DOC, resulting from interactions of snowmelt with modern surface soils and vegetation as well as pulses of older DOC, stored overwinter. In our study, we incubated spring freshet waters and exposed these waters to photodegradation, biodegradation, and combined photo-biodegradation pathways. We observed a 7%–72% DOC loss at all sites within the 2 month incubation. Photodegradation produced the greatest losses and strongest radiocarbon (Δ 1 ⁴ C) shifts, particularly when combined with biodegradation. Radiocarbon signatures revealed three DOC pools: young, labile carbon; old, labile carbon; and old, stable carbon. Soil pore waters released from a warming permafrost landscape exhibited rapid DOC losses and large radiocarbon shifts within 24 h, indicating the presence of a highly labile, old DOC pool that may be released with increased permafrost thaw. Contrary to expectations, photodegradation remained important in second-order streams, with greater DOC losses observed over time than from biodegradation alone. These results suggest that photodegradation enhances microbial access to otherwise resistant DOC, especially older, permafrost-derived fractions. Our findings provide mechanistic insight into how light and microbial processes interact to transform permafrost DOC, with implications for understanding DOC fate following permafrost thaw.

This study shows that the structural features of humic acids reflect the specific characteristics of organic matter in permafrost soils of the southern Vitim Plateau. The region's extracontinental climate determines the rate of decomposition, the depth of humification, and the chemical structure of humic acids. Brown forest soils (Haplic Cambisols) and sod-brownzems (Leptic Cambisols Skeletic) contain high amounts of organic carbon and total nitrogen in their upper horizons but differ in their vertical distribution. Brown forest soils are characterized by a sharp decrease in organic carbon content with depth and the presence of humus pockets enriched in carbon and exchangeable bases. Sod-brownzems contain more organic carbon with increase in acidity and base loss with depth. Both soil types retain satisfactory natural fertility. 13C nuclear magnetic resonance spectroscopy data reveal marked differences in the structural maturity of humic acids. Humic acids from the A horizons of brown forest soils contain an equilibrium combination of aliphatic and aromatic structures, a well-developed system of oxygen-containing groups, and moderate condensation, indicating an intermediate stage of humification. Humic acids from humus pockets are more aromatic and highly humified. They reflect an advanced stage of humification and possess high chemical stability. Humic acids from sod-brownzems also exhibit high aromaticity, which facilitates the formation of stable organomineral complexes. A comparison of the samples reveals a consistent increase in aromaticity, condensation, and stability from the A horizons of brown forest soils to the A horizons of sod-brownzems and further to humus pockets. This progression corresponds to an increase in humification and a decrease in the mobility and bioavailability of organic matter. These results confirm that the structural characteristics of humic acids are determined by soil type and formation conditions. Elemental composition revealed that humic acids from brown forest soils are characterized by the highest aromaticity and maturity, while humic acids from HA-brown forest soils-A have a less condensed structure. Humic acids from sod-brownzems occupy an intermediate position, combining high aromatization with a moderate degree of humification. Overall, the obtained elemental composition data are fully consistent with the results of 13C NMR spectroscopy, mutually confirming the identified structural features and the degree of transformation of soil organic matter.

As the second largest permafrost carbon reservoir in China, the stability of soil organic carbon (SOC) in the permafrost region of the Greater Khingan Moutains plays an important role in regulating climate change. To reveal the molecular characteristics of SOC and their influence on mineralization process, we collected surface soil samples (0-10 cm) from both the discontinuous and sporadic permafrost zones. Soil organic carbon molecular composition and diversity were characterized using Fourier transform attenuated infrared (FTIR) spectroscopy. SOC mineralization dynamics at 10 ℃ and 20 ℃ were examined with a 9-week laboratory incubation experiment. We further explored the coupling relationship between temperature sensitivity (Q10) and molecular characteristics. The results showed that: SOC functional group composition and molecular diversity showed significant spatial heterogeneity, primarily governed by permafrost type. The discontinuous permafrost zone exhibited significantly higher abundances of aromatic (C=C, COO-) and alkyl (C-H) groups but a lower abundance of alcohol and phenol (O-H) groups compared to the sporadic permafrost zone. Molecular diversity was significantly higher in the discontinuous zone and was correlated with soil pH and water holding capacity (WHC). Warming significantly enhanced SOC mineralization, with cumulative mineralization at 20 ℃ being 2.1-2.3 times greater than that at 10 ℃. The Q10 values ranged from 1.1 to 1.9, and showed significant positive correlations with labile components, such as aliphatic (C-H) and amide (N-H) groups. Those results indicated that the rapid response of these active carbon pools was key to driving temperature sensitivity. Through elucidating the regional coupling between SOC molecular characteristics and temperature sensitivity in the permafrost of the Greater Khingan Mountains, our results offer a molecular-scale theoretical basis for accurately assessing the permafrost carbon-climate feedback potential.

Organic and inorganic solute fluxes from soils to rivers follow a hydrological continuum linking terrestrial and aquatic compartments, yet this cascade remains poorly constrained in permafrost regions despite its importance for carbon and greenhouse gas (GHG) cycling. We investigated six hydrological continuums-soil water, fen, lake, riparian zone, stream, and river-across a 1500 km north-south transect of the Western Siberian Lowland, spanning the full gradient from permafrost-free taiga to continuous permafrost tundra. During summer baseflow, surface and soil waters were analyzed for dissolved organic carbon (DOC), CO2, CH4, and 40 major and trace elements. DOC, CO2, and CH4 concentrations systematically decreased from soils and fens toward lakes and rivers, highlighting headwaters as dominant sources of carbon and GHGs. Aluminum covaried with DOC, consistent with organic complexation and downstream pH increases, whereas Fe and Mn reflected local redox variability. In contrast, Ca, Mg, Sr, and soluble anions increased downstream in southern, permafrost-free systems, indicating active groundwater inputs, while no such trend was observed in tundra sites under continuous permafrost, pointing to strong hydrological isolation. DOC declined with increasing drainage area, whereas CO2 and CH4 showed no consistent dependence on watershed size. Nutrients (Si, P) increased downstream mainly within discontinuous permafrost zones, suggesting enhanced subsurface contributions. Principal component analysis revealed two dominant patterns of covariation: one linking DOC, Fe, Al, and low-mobility lithogenic trace elements, consistent with colloidal transport of organic and organo-ferric complexes, and a second associated with electrical conductivity and labile ions, reflecting variable groundwater influence and subsurface-surface connectivity. GHG concentrations were largely independent of these patterns and instead related to local redox conditions and subsoil CO₂-CH₄ inputs. Overall, this study provides the first integrated, pan-regional assessment of coupled organic carbon, greenhouse gases, and major-trace element dynamics along complete hydrological continuums spanning the full permafrost gradient of the Western Siberian Lowland. By combining multi-compartment sampling with a space-for-time framework, we identify two fundamental controls-colloidal transport limitation and groundwater-driven source limitation-that unify solute behavior across climate zones. The results demonstrate how permafrost extent governs hydrological connectivity, biogeochemical processing, and GHG regimes, offering a mechanistic basis for predicting Arctic river responses to thaw, warming, and changing water-groundwater exchange.

Unravelling methylmercury formation in high-altitude Tibetan thermokarst lakes.

• Two-scale regular grids reveal scale-dependent spatiotemporal heterogeneity with amplified fine-scale TDD and FDD. • Medium FVC (0.5–0.75) optimizes permafrost thermal stability with the lowest MAGST and SO. • Variograms reveal coherent spatial autocorrelation during spring transition but stochastic noise in winter. Ground surface temperature (GST) serves as the upper thermal boundary condition governing the thermal regime of permafrost, yet its fine-scale spatial heterogeneity associated with complex surface characteristics remains a critical uncertainty, largely due to a scarcity of high-density in-situ observations. To bridge this gap, we established a multi-scale systematic monitoring network in June-July 2023 at a representative alpine meadow site in the Headwater Area of the Yellow River, northeastern Qinghai-Xizang Plateau. The network comprises two regular grids with extents of 100 m × 100 m and 1000 m × 1000 m (121 nodes each), capturing hourly GST dynamics. By integrating thermal data with high-resolution (0.1 m) unmanned aerial vehicle (UAV)-derived fractional vegetation cover (FVC), we identified a non-linear vegetation forcing mechanism. A cooling optimum was observed at medium FVC (0.5–0.75), yielding the lowest MAGST (−0.56 ± 0.06 °C and −0.71 ± 0.12 °C for the 100-m and 1000-m grids, respectively) by effectively offsetting summer radiative heating against winter insulation. Conversely, low FVC grid points showed amplified diurnal variability (up to 6.09 °C). Spatial analysis revealed scale-dependent thermal regimes: the fine-scale 100-m grid highlighted localized heat accumulation linked to micro-scale surface heterogeneity, while the 1000-m grid showed seasonal structural instability, where coherent spatial patterns disintegrated during winter. These findings provide critical, scale-dependent constraints for calibrating process-based permafrost models.

Abstract δ 13 C in particulate organic carbon (POC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), carbon dioxide (CO 2(g) ) and methane (CH 4(g) ), together with geochemical modeling, were applied to describe carbon cycle evolution in 40 boreal lakes situated across a permafrost thaw gradient in northeastern Alberta, Canada, where hydrological and geochemical trends had previously been established in a multi‐decadal study. Progressive carbon cycle succession, characterized by enhanced allochthonous carbon loading, methanogenesis, methane oxidation, and alteration of in‐lake DIC regulation, is found to progress in response to periodic water input increases associated with permafrost thaw, and has resulted in modification of the carbon cycle processes in post‐thaw lakes. Hydrologic indicators, including water yield (WY), groundwater—surface water ratio (GW/SW), and tritium content appear to undergo evolution across the thaw gradient, and proceed consistently among softwater, circumneutral, and hardwater lakes, although site‐specific differences in underlying organic versus inorganic carbon source balances are apparent. Progressive CO 2 supersaturation and CH 4 increases generally accompany permafrost thawing. Isotopic signatures suggest mainly acetoclastic methane production, found in previous studies to be common for newly‐thawed peatlands, subsequently modified by methane oxidation in 50% of lakes. Alteration of hydrologic, geochemical and carbon cycling processes has important implications for understanding potential trajectories of climate‐driven changes near the southern margin of the zone of discontinuous permafrost.

Abstract. Permafrost soils have the potential to release large amounts of soil carbon to the atmosphere under climate change. However, in the Sixth Coupled Model Intercomparison Project (CMIP6), only two Earth System Models (ESM) represented permafrost carbon, both sharing the same land surface model. This makes future permafrost carbon dynamics highly uncertain and underscores the urgent need to include permafrost carbon in ESMs to enable more reliable future projections of climate change and remaining carbon budget estimates. Here, we present IPSL-Perm-LandN, an improved version of the Institut Pierre-Simon Laplace (IPSL) ESM (used for CMIP6) aiming at better representing high-latitude land ecosystems. The main developments are the inclusion of an explicit nitrogen cycle and of key permafrost physical and biogeochemical processes. The latent heat associated with soil water freeze/thaw is taken into account in the energy budget, as well as soil thermal insulation by soil organic matter and a surface organic layer (e.g. litter or moss). Soil organic carbon and nitrogen are vertically resolved with depth-dependent decomposition dynamics, a key feature for representing the effect of gradual permafrost thaw on soil biogeochemistry. Cryoturbation is represented as a diffusion process that buries organic matter in the deeper soil layers. Compared to the previous version of the model used for CMIP6, we show that the extent of the permafrost region has improved significantly and that the simulated active layer thickness in the Arctic is in better agreement with observations. Permafrost soil carbon stocks have increased 20-fold to reach 1006 PgC in the top 3 m of soil, which is consistent with observation-based estimates. We simulate that the permafrost region has been a net carbon sink over the past 150 years (+0.32 ± 0.04 PgC yr−1 on average between 2005 and 2014), primarily due to carbon uptake from boreal forests. This is comparable with recent pan-Arctic carbon balance estimates, when accounting for unrepresented processes in our model (fire and riverine carbon losses). Overall, the inclusion of permafrost processes has improved the response of the model to anthropogenic perturbations in high latitudes over the past century, marking a step forward in the representation of Arctic ecosystems.

Abstract Permafrost soils contain approximately twice the amount of carbon as the atmosphere and this carbon could be released with Arctic warming, further impacting climate. Mosses are major component of Arctic tundra ecosystems, but the environmental drivers controlling heat penetration though the moss layer and into the soil and permafrost are still debated, especially at fine spatial scales where microtopography impacts both vegetation and soil moisture. This study measured soil temperature profiles (1-15cm), summer thaw depth, water table depth, soil moisture, and moss thickness at a fine spatial scale (2 m) together with meteorological variables to identify the most important controls on the development of the thaw depth during two Arctic summers. We found a negative relationship between the green moss thickness (up to 3 cm) and the soil temperatures at 15 cm, suggesting that mosses insulated the soil even at high volumetric water contents (&gt;70%) in the top 5 cm. A drier top (2-3 cm) green moss layer better insulated deep (15 cm) soil layers by reducing soil thermal conductivity, even if the moss layers immediately below the top layer were saturated. The thickness of the top green moss layer had the strongest relationships with deeper soil temperatures, suggesting that the top layer had the most relevant role in regulating heat transfer into deeper soils. Further drying of the top green moss layer could better insulate the soil and prevent permafrost thawing, representing a negative feedback on climate warming, but damage or loss of the moss layer due to drought or fire could reduce its insulating effects and release carbon stored in the permafrost, representing a positive feedback to climate warming.

The soils of the Lena River Delta contain significant reserves of soil organic matter, and as a result of riverine erosion and permafrost degradation, the coastal zone is undergoing rapid transformation, releasing substantial amounts of buried carbon from organic‐rich permafrost soils and Ice Complex deposits. To investigate the influence of fluvial processes and cryogenesis on the physical stabilization of SOM, we analyzed the microstructure of Cryosols (15 soil samples) and Ice Complex (4 deposit samples) using polarization microscopy (Leica DM750P) and ImageJ software (National Institute of Health, USA). The study revealed the specifics of soil formation in the Lena River Delta, as well as the features of organic matter release from the frozen state. Thin sections of soils subjected to periodic flooding and long‐term freeze/thaw cycles were examined, alongside organomineral deposits exposed by degradation of the Ice Complex. Results indicate that soils affected by prolonged cryogenic processes (long‐term freezing and thawing cycles) exhibit the highest degree of soil organic matter physical stabilization, likely due to microaggregate formation. In contrast, freshly thawed Ice Complex deposits show lower aggregation stability, suggesting a potential vulnerability to biodegradation upon release from permafrost. These findings highlight the critical role of cryogenic and fluvial dynamics in regulating Arctic carbon cycling under climate change.

Spatial modelling of polycyclic aromatic hydrocarbon distribution in a Canadian ice wedge polygon tundra landscape.

Abstract Arctic permafrost soils store vast amounts of carbon (C)‐rich organic matter that has accumulated due to low temperatures that suppress microbial decomposition. As Arctic warming intensifies, soil microbes become increasingly active, even while plant growth remains dormant. Seasonal decoupling between plant and microbial decomposer growth can accelerate carbon dioxide (CO 2 ) release from soils, however, most Earth system models underestimate cold‐season C emissions and do not accurately represent the freeze–thaw transitions that govern microbial access to substrates during these critical periods. These model–data mismatches often stem from empirical formulations, such as using a fixed Q 10 functions to represent microbial respiration, an oversimplification of a complex interplay of temperature, moisture, and substrate diffusion. To address this, we incorporated explicit, temperature‐dependent diffusional constraints on microbial activity, (the Dual Arrhenius Michaelis–Menten (DAMM) model), into the Stoichiometrically Coupled Acclimating Microbe–Plant–Soil (SCAMPS) model which uses the Q 10 function to represent microbial respiration. We used this enhanced model (SCAMPS_DAMM) to simulate Arctic ecosystem responses to a 50‐year winter warming scenario and compared outcomes to the original SCAMPS framework. While both models predicted overall soil C losses under warming, SCAMPS_DAMM produced more constrained increases in microbial respiration and plant productivity. These differences led to similar total ecosystem C declines but divergent patterns of C and N allocation between plant and soil pools. Thus, incorporating mechanistic constraints on microbial access to substrates through explicit representation of temperature and moisture controls altered model projections of Arctic biogeochemical responses to climate change.

Technological justification of constructive solutions for railway roadbed on permafrost soils using an expert system

A model is proposed in which the capacity of the road network section depends on the technical and operational condition of the road surface – the presence of sinkholes, potholes, ruts, as well as their predictive depth. Appearing of these defects on the road surface is associated with excessive thawing and permafrost soil settlement in the formation occurring under the influence of the climate change. The soil thawing depth is modelled on the basis of predictive climatic parameters during the full average year, and then the maximum thawing depth and the corresponding soil settlement is determined. Three main scenarios of the climate change are considered: temperature contrast increasing, uniform warming and their combination. The assumed value of warming or temperature contrast increasing is considered to be a random value distributed according to the normal law; the predicted decrease in the road section capacity is defined as a weighted average over the entire range of possible climate changes. According to the results of the numerical implementation of the model on the road network sections for natural and climatic conditions of Yakutia, it is shown that in the third scenario of the climate change the road network section capacity is predicted to decrease from 17% (the formation is dry sandy permafrost soil) to 50% (the formation is clay soil of high humidity). The impact of natural and climatic features of the territory is predicted to be at a level up to 10% of the total reduction in the capacity of road network sections.

Introduction. The article presents differentiated studies of the stress-strain state of foundation structures of an industrial frame structure in case of emergency situations associated with the thawing of permafrost soil. The object of the study is a pile foundation with a high grillage for a frame industrial building. Aim. Determination of the ultimate deformation values at which structural elements fail. Materials and Methods. The research materials are computational models in the LIRA SAPR software package, which make it possible to determine probable emergency situations. The main research method is the calculation-theoretical method. It allows determining the most probable emergency situations associated with thawing of the soil base based on observations. During the study, not only the results of relative deformations were obtained, but also the structures susceptible to destruction were identified, and the redistribution of forces in the piles due to base deformation was observed. Results and Conclusions. The results obtained showed that changes in the deformation properties of soil due to thawing, depending on the degree of thawing, affect the stress-strain state of the building foundation. The considered thawing options reflect the nature of the structure deformation and make it possible to determine the most dangerous or probable case. The results obtained can be used to form an automatic geotechnical monitoring system and establish criteria for its assessment.