Reconstructing glacier retreat from the Last Glacial Maximum （LGM） to the early Holocene using cosmogenic ¹⁰Be exposure dating of moraines is essential for understanding the climatic transition between glacial and interglacial periods. This period， spanning approximately 26.5~10 ka， is marked by major reorganizations in the global climate system， including rapid temperature shifts， fluctuations in atmospheric CO₂， changes in ocean circulation， and variations in orbital forcing. These processes collectively shape ice sheet dynamics and influence cryospheric feedbacks in the Northern Hemisphere. However， the fragmented preservation of moraine sequences at individual sites has hindered efforts to resolve the spatiotemporal patterns of glacier retreat on a continental scale. Single-site records often fail to capture the timing and magnitude of broader deglacial trends. To overcome this limitation， this study compiled a comprehensive dataset of 4 003 published ¹⁰Be exposure ages from 802 well-dated moraines spanning the period between 26.5 and 10 ka. The dataset encompassed a wide range of glacial settings and climates， offering a rare opportunity to conduct integrated regional and hemispheric-scale analyses. The moraines were grouped into four major regions—Asia， Europe， North America， and Greenland—to enable comparative analysis. All ¹⁰Be exposure ages were recalculated using a consistent， globally averaged ¹⁰Be production rate and the LSDn （time-dependent） scaling scheme. This recalibration ensured inter-study comparability and minimized biases caused by inconsistent production rates or scaling methods across different studies. To resolve the temporal distribution of glacier retreat events， the Probabilistic Cosmogenic Age Analysis Tool （P-CAAT） was employed based on probability density estimation （PDE） of exposure ages. This method identified statistically significant clusters of moraine ages by fitting the composite age distribution with multiple Gaussian components， enabling the identification of peak periods of moraine formation or abandonment. Gaussian component analysis was conducted independently for each region and for a combined Northern Hemisphere dataset excluding Greenland. The Greenland moraines were analyzed separately due to preservation patterns heavily constrained by the spatial extent and temporal evolution of the ice sheet margin， differing from other regions. This analytical framework enabled the identification of eight statistically significant hemispheric-scale glacier retreat episodes， centered at （23.9±1.0） ka， （20.5±1.3） ka， （18.3±0.7） ka， （16.6±0.8） ka， （14.7±0.8） ka， （13.0±0.7） ka， （11.4±0.4） ka， and （10.3±0.6） ka. The first two episodes occurring before 19 ka were primarily attributed to increases in Northern Hemisphere summer insolation due to orbital forcing. In contrast， the third through seventh episodes occurred after 19 ka and broadly coincided with abrupt increases in atmospheric CO₂， indicating that greenhouse gas forcing became the dominant driver of glacier retreat. The final retreat episode around 10.3 ka aligned with the peak in summer insolation during the early Holocene. Regional comparison showed a high degree of synchronicity in retreat timing， although the earliest phase （~24 ka） was absent from the Greenland and North American records， likely due to differing responses between ice sheet and mountain glacier systems. Some variability in the number or prominence of retreat episodes across regions could also be attributed to differences in sample density and uncertainties in exposure ages. This study represents one of the most extensive syntheses of ¹⁰Be moraine chronologies in the Northern Hemisphere to date. By integrating a large， globally distributed dataset and applying a standardized analytical workflow， this study improves the temporal resolution of deglacial patterns and provides critical geological constraints for climate-cryosphere interaction models. The findings enhance the understanding of the timing and drivers of glacier retreat and have implications for refining ice sheet reconstructions， glacial isostatic adjustment models， and past sea-level estimation. Moreover， the observed regional differences highlight the importance of glacier type， geographic context， and climate forcing in shaping the heterogeneous responses of ice masses to global climate change.

With global warming and increasing human activities， slope geohazards such as landslides， thaw collapse， and gelifluctions have become increasingly frequent on the Qinghai-Xizang Plateau. A large number of slope geohazards have developed along the Gongyu High-grade Highway on the eastern edge of the Qinghai-Xizang Plateau， posing serious threats to infrastructure construction and safe operation in the region. However， the distribution patterns and factors influencing unstable slopes along the entire highway remain unclear， which severely constrains the construction and development of highways. Using IPTA-InSAR technology， this study conducted surface deformation monitoring， early-stage identification of unstable slopes， and field validation along the Gongyu High-grade Highway. Then， the spatial distribution and types of unstable slopes were summarized， and their influencing factors of deformation were analyzed. The results showed that the surface deformation rate along the radar line-of-sight direction in the study area ranged from -249 to 335 mm·a^-¹. The overall area remained relatively stable， with significant surface uplift observed near the Duogerong Basin and Bayan Har Mountains. Based on the InSAR deformation monitoring results， a total of 974 unstable slopes were identified. Unstable slopes were widely distributed in the study area， mainly concentrated in the Heka Mountain to Wenquanxiang segment and Qingshuihe County to Yushu segment， with minor distributions near Maduo County and Yeniugou. Types of unstable slopes included creep， colluvial landslides， and bedrock landslides. Among them， one large-scale bedrock landslide was located along the Qinggenhe in Wenquanxiang. The development of this landslide was structurally controlled. Under the influence of rainfall and river erosion， the slope experienced sliding. In the future， it may block the Qinggen River， potentially triggering disaster chain effects such as barrier lake and dam break. One colluvial landslide was located in the mountainous area of Heka Mountain， mainly influenced by rainfall and temperature. The persistent and cyclic freeze-thaw actions caused extensive cracks on the slope surface. Precipitation infiltrated through cracks， altering the thermal state at the base of the colluvium and promoting ground-ice melting on the bedrock interface. This process formed a sliding surface. Meltwater and rainwater further eroded and transported the colluvium， triggering sliding. Additionally， the sliding of the lower gully channel at the slope’s toe exerted a retrogressive pull， causing the middle section of the slope to slide. There were 972 creep slopes distributed along the entire highway. One typical creep slope was located near the Heka Mountain. This slope was located in a small watershed catchment area with consistently high water or ice content. Under the influence of road construction and excavation disturbances， the underground ice layer was exposed and gradually melted. As the underlying materials became saturated with water， the soil structure was damaged， leading to an increase in pore water pressure and a reduction in shear strength. This resulted in the formation of a weak sliding surface， triggering slope failure. In the future， this landslide may gradually evolve into other types of geohazards. The deformation of unstable slopes in the study area is primarily controlled by the loose soil characteristics of grassland and desert areas. Increased rainfall and temperature variations serve as the direct driving factors for slope deformation. This study reveals the development characteristics and influencing factors of slope geohazards along the Gongyu High-grade Highway， providing scientific support for risk prevention， hazard control， and the safe operation of the Gongyu High-grade Highway.

The rapid formation， expansion， and outburst of glacial lakes are the prominent consequences of global warming and glacier recession. Large-scale glacial lake mapping， glacial lake outburst flood （GLOF） compilations， and risk assessments are essential for understanding regional environmental changes and implementing effective disaster prevention and management strategies. Centered on the Tibetan Plateau， the Asian Water Tower is one of the major global glacial lake regions and has experienced rapid glacial lake expansion and significant disaster impacts over the past few decades. This study focuses on glacial lake changes， outbursts， and associated risks in the Asian Water Tower and summarizes recent advances in glacial lake research. The results show that： （1） The overall rate of glacial lake area expansion in the Asian Water Tower from 1990 to 2018 ［（31.6±4.0） km²·（5a）^-1］ exceeded the average rate observed during 2018—2022 ［（22.7±8.5） km²·（5a）^-1］. Proglacial lakes， accounting for 83% of the total area increase during 2018—2022， emerge as the primary contributor to the current expansion of glacial lakes in the Asian Water Tower， with changes mainly concentrated in the eastern Himalayas and southeastern Xizang. Under the future ice-free scenarios， a total of 15 826 potential glacial lakes with areas exceeding 0.02 km² are projected to emerge， covering an area of （2 253.95±1 291.29） km² with a water volume of （60.49±28.94） km³. The western glacier-rich region is projected to experience a greater emergence of new and rapidly expanding lakes， although with a time lag compared to eastern regions such as the eastern Himalayas and southeastern Xizang， due to different climate patterns. （2） From 1900 to 2020， 145 credible moraine-dammed GLOFs were recorded in the region， with a marked increase in frequency after the 1980s. Specifically， the average annual number increased from 1.5 GLOFs during 1981—1990 to 2.7 GLOFs during 2011—2020. Spatially， GLOF activity has intensified in southeastern Xizang and China-Nepal border area. Additionally， 183 GLOFs stemming from ice-dammed lakes are documented， mainly concentrated in the Karakoram and western Tianshan Mountains， demonstrating watershed-scale clustering and periodic outbursts. （3） The ongoing expansion and frequent outbursts of glacial lakes have significantly increased disaster risk across the region. A systematic hazard assessment has identified 1 499 glacial lakes classified as high or very high hazard level， potentially affecting a flood inundation area of 6 353 km². In terms of disaster-bearing bodies， approximately 55 808 buildings， 105 existing or planned hydropower projects， 194 km² of farmland， 5 005 km of roads， and 4 038 bridges are vulnerable to potential GLOFs. Approximately 190 000 peoples are directly exposed along GLOF-prone pathways. Subsequently， 85 lakes are classified as very high risk level and 113 as high risk level. The eastern Himalaya and southeastern Xizang exhibit the highest levels of GLOF hazard， exposure， and risk. This situation is exacerbated by the rapid expansion of glacial lakes， the increased frequency of GLOFs， the density of dangerous glacial lakes， and the significant potential disaster volume in the Asian Water Tower. These findings highlight the urgent need for more proactive GLOF prevention and mitigation efforts and the necessity of constructing a regionally coordinated and dynamic disaster management system. Overall， while glacial lake research in the Asian Water Tower has progressed rapidly over the past decade， critical challenges remain. These include the need for standardized and high-precision lake mapping， improved understanding of GLOF-climate relationships， and more refined and watershed-scale risk assessments.

On 7 January 2025 at 09：05 （UTC+8）， an earthquake with a surface-wave magnitude （M_s） of 6.8 struck Tingri County （28.50° N， 87.45° E）， Shigatse City， Xizang Autonomous Region. This earthquake and its aftershock sequence may have affected glacier system stability， potentially triggering secondary hazards such as ice avalanches. To investigate the dynamic evolution patterns of glaciers in the affected region， this study systematically analyzed the spatial distribution characteristics and dynamic changes of glaciers within the seismic intensity VI zone of the Tingri earthquake using Landsat series remote sensing images and two phases of China’s glacier inventory data， combined with spatial analysis methods. The results showed that： （1） as of 2023， the study area contained 659 glaciers with a total area of 811.70 km² and an ice volume of 74.44 km³. （2） Since 1974， the number of glaciers in the study area decreased by 307 （a reduction of 31.78%）， while the total glacier area diminished by 333.13 km² （a decline of 29.10%）， demonstrating a significant retreat trend. The retreat rates of glaciers across the three study periods （1974， 2010， and 2023） exhibited a phased characteristic of “rapid initial decline followed by gradual deceleration”. （3） Climate warming （with a temperature increase of 2.7 °C from 1990 to 2024） was identified as the primary driver of glacier retreat， while glacial lake expansion further accelerated melting at the glacier terminus. The thickness and surface flow velocity of typical glaciers in the study area have undergone substantial changes. Glacier projection models predicted that glaciers in this region would continue to melt in the future. It is recommended to focus on the potential impact of earthquakes on the internal structures of glaciers and strengthen the quantitative assessment of the impact of earthquakes on glacial dynamics. Additionally， dynamic evolution monitoring of large glaciers and critical glacial lakes should be enhanced to effectively mitigate potential disaster chain effects triggered by earthquakes.

Variations in the characteristics of Arctic vortex and their impact on snowfall in mid- to high latitudes， especially extreme snowfall events， are of great significance for understanding extreme weather or climate events. This study used the climate system index dataset released by the Institute of Atmospheric Physics， Chinese Academy of Sciences， along with meteorological station observation data. Statistical methods such as trend analysis and correlation analysis were employed to analyze the variation characteristics of the polar vortex area and intensity， as well as the variation characteristics of snowfall amounts and days in the Songhua River Basin （SRB） from 1961 to 2021， thereby revealing the correlation between polar vortex indices and snowfall in the SRB. The results showed that： （1） The polar vortex characteristics changed significantly from 1961 to 2021. Specifically， the polar vortex area reduced remarkably， polar vortex intensity enhanced markedly， and polar vortex central intensity weakened considerably， at rates of -0.807·（10a）^-1， -33.291·（10a）^-1， and 5.576·（10a）^-1， respectively， while the polar vortex center location showed no significant change. （2） From 1961 to 2021， although the annual snowfall amounts and light snowfall amounts showed no significant trends， substantial changes were observed in annual snowfall days and snowfall amounts/days at various intensity levels across the SRB. Among them， annual snowfall days and light snowfall days decreased significantly， while the amounts and days of moderate/heavy snowfall increased significantly. （3） Except for light snowfall amounts， which had no significant correlation with the polar vortex， variations in polar vortex central intensity， polar vortex intensity， and polar vortex area all showed significant correlations with snowfall indicators in the SRB. The weakening of the polar vortex central intensity and the strengthening of the polar vortex are the main influencing factors leading to the increases in total snowfall， as well as the amounts and days of moderate/heavy snowfall in the SRB.

To explore the feasibility of fiber-reinforced slag concrete in cold-region engineering and determine the optimal sisal fiber content and slag replacement ratio， this study investigated the mechanical properties and microstructure of fiber-reinforced slag concrete under freeze-thaw cycles. The results showed that replacing fine aggregates with slag in concrete had potential application value under freeze-thaw cycles， and sisal fiber significantly enhanced the mechanical properties of concrete. Under freeze-thaw cycles， the compressive strength of concrete initially increased and then decreased with the increase in slag replacement ratio， reaching a maximum of 40.9 MPa at a replacement ratio between 13.2% and 26.4%. When the slag replacement ratio exceeded 39.6%， the compressive strength of concrete declined significantly， accompanied by substantial mass loss. The incorporation of sisal fiber markedly improved the compressive strength of concrete. After 120 freeze-thaw cycles， the concrete with 1 kg·m^-3 sisal fiber exhibited the highest compressive strength and the lowest strength loss rate， with values of 36.1 MPa and 10.2%， respectively. Additionally， the concrete with 2 kg·m^-3 sisal fiber demonstrated the lowest mass loss. Microscopic analysis revealed that freeze-thaw cycles caused surface and internal damage in concrete， affecting hydration reactions and reducing concrete durability.

The mining area in western Sichuan， situated in a high-altitude seasonally frozen soil region， is characterized by harsh environmental conditions， complex engineering geology， and a fragile ecosystem. Mining activities have generated extensive rock slopes， causing significant damage to the local ecology and environment. To implement the concept of green mining， the ecological restoration of rock slopes in open-pit mining sites in alpine regions requires urgent implementation. External-soil spray seeding is commonly employed for slope ecological restoration. However， the surface soil layer on rock slopes in mines in these alpine regions is highly susceptible to cracking， loosening， and detachment due to freeze-thaw cycles， leading to unsatisfactory restoration effects. Therefore， it is essential to modify the ecological restoration soil to meet the requirements of freeze-thaw durability and mechanical performance. In this study， soil was modified using sisal fiber， polyacrylamide （PAM）， and carboxymethyl cellulose （CMC）. Through unconfined compressive strength （UCS） tests， triaxial shear tests， and scanning electron microscopy （SEM） analysis， the modification mechanisms of sisal fiber， PAM， and CMC on soil under freeze-thaw cycles were systematically investigated. The influencing patterns of fiber content and fiber length on the compressive strength， shear strength， and microstructure of soil under different freeze-thaw cycles were analyzed. The results showed that sisal fiber and PAM-CMC significantly enhanced the mechanical properties and freeze-thaw resistance of the modified soil through the coordinated effect of the fiber-soil spatial network structure and binder cementation. With the increasing number of freeze-thaw cycles， the compressive strength and shear strength of pure soil （PS）， PAM-CMC modified soil （PC）， and sisal fiber-PAM-CMC modified soil （SPC） first declined rapidly and then gradually stabilized. At 0 freeze-thaw cycle， SPC0.15-20 （0.15% sisal fiber content， 20 mm length） exhibited superior performance in compressive strength， failure strain， deviatoric stress， cohesion， and internal friction angle compared to PS and PC. Specifically， compressive strength increased by 47.7% and 39.6%， failure strain by 44.2% and 35.0%， deviatoric stress by 49.3% and 38.8%， cohesion by 81.1% and 56.3%， and internal friction angle by 8.7% and 7.9%， respectively. After 12 freeze-thaw cycles， SPC0.15-20 demonstrated superior performance in compressive strength， failure strain， deviatoric stress， cohesion， and internal friction angle compared to PS and PC. Specifically， the compressive strength increased by 78.3% and 39.0%， failure strain by 84.8% and 39.0%， deviatoric stress by 39.8% and 29.0%， cohesion by 93.9% and 51.7%， and internal friction angle by 9.6% and 8.9%， respectively. The optimal parameter combination was a sisal fiber content of 0.15% and a length of 20 mm. At 0 freeze-thaw cycle， SPC0.15-20 outperformed all other combinations in compressive strength， failure strain， peak deviatoric stress， cohesion， and internal friction angle， with improvements ranging from 7.3% to 28.0%， 3.7% to 22.8%， 5.1% to 18.5%， 4.3% to 20.8%， and 3.9% to 5.5%， respectively. After 12 freeze-thaw cycles， SPC0.15-20 remained superior to the other combinations， showing enhancements of 2.6% to 26.9% in compressive strength， 1.1% to 25.0% in failure strain， 6.5% to 8.4% in deviatoric stress， 0.6% to 16.7% in cohesion， and 0.8% to 3.9% in internal friction angle. Analysis of macroscopic failure patterns revealed that the addition of fibers and binder could effectively inhibit crack propagation， reduce radial deformation， and mitigate freeze-thaw damage， integrating soil particles into a cohesive mass， thereby enhancing compressive strength and deformation resistance of the soil. SEM images demonstrated that the interaction between fibers and binder improved mechanical and frost-resistant properties of the soil. PAM-CMC gel could fill pores between soil particles and provide adhesion. Sisal fibers could form a fiber-soil spatial network structure， simultaneously enhancing the integrity of the PAM-CMC gel. This established a synergistic mechanism of “fiber crack resistance and binder pore filling”， effectively restricting pore expansion induced by freeze-thaw cycles. This study addresses the mechanical strength requirements of ecological restoration materials under freeze-thaw cycles and proposes a viable scheme for mechanically enhancing soil used in slope spray seeding， providing theoretical support for the improvement of external-soil techniques in the ecological restoration of mine slopes in alpine regions.

In cold-region tunnel engineering， during long-term service， freeze-thaw cycles can lead to increased seepage， reduced bearing capacity， frost heave damage， and other issues that severely compromise the structural stability and operational safety of tunnels. There is an urgent need to explore a new reinforcement method for surrounding rock that is efficient， durable， environmentally friendly， and freeze-thaw resistant. Based on an analysis of the mechanism of microbial-induced calcium carbonate precipitation （MICP） for seepage reduction and reinforcement of tunnel surrounding rock in cold regions， this study developed an MICP reaction solution suitable for cold-region rock engineering. Test research was conducted on the application of MICP for seepage reduction and reinforcement of tunnel surrounding rock in cold regions. The microbial activity， urea hydrolysis efficiency， and distribution patterns of calcium carbonate precipitation under low-temperature conditions were analyzed. The biomineralization mechanism of MICP under freeze-thaw cycles was revealed， and the improvement effects of MICP on the permeability and frost heave resistance of surrounding rock were clarified. This provided a green and long-term solution for reinforcing surrounding rock in cold-region tunnel engineering， while also contributing to the theoretical research on bio-mediated reinforcement in cold environments. The main work and conclusions were as follows： （1） Considering the characteristics of cold-region environments， Sporosarcina pasteurii was selected. Although its metabolic activity was inhibited at low temperatures， its non-Newtonian fluid characteristics helped maintain the permeability of the cementation solution， demonstrating good cold resistance. During the MICP hydrolysis reaction， Sporosarcina pasteurii not only provided urease for microbial-induced calcium carbonate precipitation but also served as a nucleation site for calcium carbonate crystal formation. Additionally， it had low free energy， a simple reaction mechanism， and ease of process control， making it an ideal choice for this test. （2） The bacterial growth activity and urease activity were monitored using spectrophotometry and conductivity methods， determining an optimal cultivation time of 72 hours. Quartz sand with a mesh size of 200 was selected as the MICP filling aggregate. The MICP cementation solution was prepared using a 1.0 mol·L⁻¹ urea-CaCl₂ solution as the reaction agent. The bacterial solution （with an OD₆₀₀ value of 4.60） and urea-CaCl₂ solution were mixed at a volume ratio of 1∶1. The MICP slurry was injected into pre-fractured rock samples. After a 28-day repair period and a 7-day curing period， freeze-thaw cycle tests， capillary water absorption tests， shear strength tests， and compressive strength tests were conducted. Additionally， SEM analysis of the cementation morphology and X-ray diffraction analysis of the biomineral phases were performed to analyze the permeability and reinforcement performance of MICP on the frost-thaw fractured rock. （3） The test results showed that calcium carbonate precipitation generated by MICP effectively sealed sandstone fractures. A high-concentration bacterial solution promoted uniform distribution of microbial cells， enhancing MICP reaction efficiency and producing a large amount of CaCO₃ crystals. These crystals effectively filled pores and strengthened particle connections， significantly improving the permeability characteristics of fractured sandstone. The microorganisms simultaneously served dual functions： urease catalysis and nucleation supply. （4） After MICP treatment， the internal structure of the sandstone was dominated by micropores and small pores. The permeability coefficient decreased by 45.2% compared to untreated sandstone. The calcium carbonate precipitation by MICP effectively blocked water migration pathways， maintaining excellent seepage reduction performance even after freeze-thaw cycles. （5） MICP treatment significantly enhanced the mechanical properties of freeze-thaw sandstone. After 60 freeze-thaw cycles， the shear strength of MICP-treated samples increased by 40.25%， and the compressive strength improved by 15.97%. The enhancement in mechanical properties was primarily attributed to the calcium carbonate cementation layer， which strengthened interparticle friction and interlocking. Meanwhile， MICP mitigated fracture propagation induced by frost heave stress， and the cementation layer reduced unfrozen water migration by narrowing pores， thereby decreasing the cumulative effects of freeze-thaw damage. A strong correlation was observed between the changes in the mesostructure of freeze-thaw rock and the improvement in macroscopic mechanical properties due to MICP treatment. （6） MICP achieved fracture filling and structural densification through microbial-induced calcium carbonate precipitation. Microscopically， it optimized pore distribution and cementation morphology， while macroscopically， it significantly enhanced impermeability and mechanical strength. Even under high-frequency freeze-thaw cycles， MICP maintained excellent repair performance， providing a novel approach for preventing and controlling frost damage in tunnel surrounding rock in cold regions that combines biological compatibility with long-term stability.

The western Sichuan region is rich in mineral resources and is one of the areas with the most abundant resources of hard-rock lithium ores in China. Most mines in this region are located in seasonally frozen soil zones of alpine regions， characterized by large temperature fluctuations， intense rainfall， and high annual evaporation. The ecological and geological environment in the region is fragile， making the balance between resource development and environmental protection a major challenge. Open-pit mining exposes slope rocks to intense evaporation and significant temperature fluctuations over prolonged periods， creating conditions for dry-wet and freeze-thaw cycles. These cycles alter the internal pore structure and the permeability of rocks， further affecting slope stability and groundwater systems. Therefore， investigating the evolution of rock pore structure and permeability under different environmental conditions is critical. This study selected slate samples from an open-pit mine slope in the alpine region of western Sichuan. The samples underwent cyclic tests under three conditions， including dry-wet cycles， freeze-thaw cycles in air， and freeze-thaw cycles in water. Additionally， multiple experimental techniques were employed， including nuclear magnetic resonance （NMR） testing， permeability testing， and scanning electron microscopy （SEM）. NMR could nondestructively detect the porosity and pore size distribution of samples under different numbers of cycles and different working conditions. Permeability tests could directly measure changes in permeability， thereby investigating the influence of the number of cycles on the permeability of samples. SEM was used to observe microstructural changes， such as internal cracks and pores of the samples. To analyze and reveal the variation patterns among the number of cycles， porosity， and permeability under different working conditions， a damage variable based on porosity was introduced. The results showed that the porosity of slate samples gradually increased with the number of cycles under all conditions. After 40 cycles， porosity increased from 0.28% to 0.33% （dry-wet cycles）， 0.64% （freeze-thaw cycles in air）， and 0.66% （freeze-thaw cycles in water）， indicating that freeze-thaw cycles had a significant influence on the increase in porosity， with an especially pronounced influence on the internal small pore structure of the slate samples. Compared with freeze-thaw cycles in air， freeze-thaw cycles in water more easily induced the formation of microcracks. This was because the continuously supplied external water during freeze-thaw cycles promoted an increase in rock porosity and the formation of new cracks. Meanwhile， the permeability of the rock samples increased gradually with the number of cycles. After 40 cycles， permeability increased from 2.7×10^-3 mD （1 mD=0.987×10^-15 m²） to 2.9×10^-3 mD （dry-wet cycles）， 4.2×10^-3 mD （freeze-thaw cycles in air）， and 6.4×10^-3 mD （freeze-thaw cycles in water）， indicating that freeze-thaw cycles had a greater influence on permeability than dry-wet cycles. Permeability and damage variables exhibited a nonlinear positive correlation. However， under the three different working conditions， the R² between permeability and damage variable varied slightly， with the highest R² for freeze-thaw cycles in air， followed by those of freeze-thaw cycles in water and dry-wet cycles. This study provides practical engineering guidance for future mining activities and offers a scientific basis and theoretical support to assess slope stability and ecological environmental impact in the open-pit mines of alpine regions.

Due to the large temperature difference between day and night and the significant seasonal freezing and thawing， the water-ice phase transition occurs frequently within the rock mass in the alpine region. Especially in the main control structural planes in dangerous rocks， the volume changes and stress disturbances caused by the freeze-thaw process can easily lead to the gradual propagation and penetration of the structural planes. This further induces the instability and collapse of dangerous rocks， posing serious threats to engineering facilities and the lives and property of nearby residents. Recent frequent collapses of high-level dangerous rocks in areas such as the Qinghai-Xizang Plateau and alpine canyons in western Sichuan demonstrate that， under global climate change， the spatiotemporal distribution characteristics and failure mechanisms of freeze-thaw geological disasters require further investigation. Most existing studies have conducted freeze-thaw tests using artificial prefabricated fracture specimens. Although the fundamental patterns of fracture propagation have been revealed， these studies cannot fully capture the complex mechanisms of the propagation of main control structural planes in dangerous rocks under natural conditions. Especially at different stages of water-ice phase transition， the propagation driving force， fracture path， and fatigue life of structural planes remain insufficiently studied， affecting the prediction and prevention of dangerous rock disasters in alpine regions. To explore the propagation mechanism of the main control structural planes in dangerous rocks under water-ice phase transition， a propagation driving force model was established based on the theory of fracture mechanics for the freezing and melting periods， and analytical expressions for the stress intensity factors at each stage were derived. On this basis， a method for predicting the fatigue propagation life of the main control structural planes was proposed to quantify their evolution under multi-year freeze-thaw cycles. Based on the analysis of the driving mechanism of the water-ice phase transition， this study systematically evaluated the theoretical basis and applicability of existing frost heave force calculation methods and proposed a mixed frost heave force model integrating the effects of water migration， ice deformation， and boundary constraints， effectively mitigating the overestimation of traditional methods in calculating frost heave forces on structural planes. In this study， a dangerous rock in Aba Tibetan and Qiang Autonomous Prefecture was used as an engineering example to obtain the main control structural plane parameters， and the model application and evolution analysis were performed. The results showed that the error between the proposed frost heave force model and the measured data was less than 5.03%， demonstrating high calculation accuracy. The critical cracking length of the main control structural plane under water-filling condition was 0.0036 m， while it increased to 5.87 m under freezing condition， differing by nearly three orders of magnitude and highlighting the significant influence of water-ice phase transition stages on propagation thresholds. The freezing stage was the dominant period of structural plane propagation， which mainly caused small local collapse. During the melting stage， hydrostatic pressure more easily triggered propagation in structural planes with larger initial lengths， consequently leading to larger-scale collapses. The prediction results showed that the fatigue life of the main control structural plane in the dangerous rock was about 26 years. In summary， this study systematically establishes a mechanical model for the propagation of the main control structural planes of dangerous rocks under different stages of water-ice phase transition， and proposes the corresponding fracture criteria and life prediction method， which provides a theoretical basis for understanding the instability process of dangerous rocks under freeze-thaw action. The findings can provide scientific references for monitoring， early warning， and protection design of dangerous rock geological disasters in alpine regions， with important theoretical and engineering implications.

The freezing of the drainage system in high-speed railway tunnels in cold regions can cause a series of frost damage problems， seriously affecting tunnel operation. To more effectively mitigate frost damage in drainage ditches， this study first established a calculation model for water flow and heat transfer in tunnel drainage ditches in cold regions， and revealed the evolution mechanisms of water freezing within the ditches. Then， by monitoring and recording the temperature field of the high-speed railway tunnels in cold regions from December to May of the following year， the longitudinal temperature field of the tunnels was obtained. Finally， based on the longitudinal temperature distribution of the Hufengling Tunnel on February 6 and the water freezing mechanisms， the sections of the tunnel drainage ditch prone to freezing were predicted. The results showed that the cooling rate of water in the drainage ditch decreased with increasing water flow velocity and equivalent radius of the ditch， and increased with decreasing ditch wall temperature. The convective heat transfer coefficient between the water and the ditch wall had little effect on the cooling rate. The water temperature in the drainage ditch fluctuated with the temperature variations in ditch walls， and the flow velocity had insignificant effect on the fluctuation range of the water temperature. When the equivalent radius of the drainage ditch remained constant， the flow rate was the dominant factor determining the flow distance of the water before freezing. From December to February of the following year， the monthly average temperature in the Hufengling Tunnel increased with increasing distance from the tunnel entrance， showing an asymmetric distribution. From March to May， the monthly average temperature rose rapidly within 100 meters of the tunnel entrance， while the temperature variations in the middle section remained minor. From December to the following April， the monthly average temperature at the entrance of Hufengling Tunnel remained below 0 ℃， and the monthly average temperature at all monitored cross-sections in January and February was below 0 ℃. The monthly average temperature of the Zhishan Tunnel showed a symmetrical distribution along its longitudinal direction， increasing with distance from the tunnel entrance. From December to April of the following year， the monthly average temperature remained below 0 ℃. With the warming climate， the monthly average temperature differences between the tunnel cross-sections gradually decreased. No freezing was observed in the drainage ditch of the Hufengling Tunnel during the cooling season. However， during the warming season， when the water flow rate reached 6.28 L·s^-1， freezing occurred in the insulated side ditch within approximately 3 000 m from the tunnel entrance and in the insulated central ditch within 1 000 to 3 700 m. Moreover， as the flow increased， the frozen section became shorter， with freezing occurring within specific ranges under different flow rates. Based on the prediction results， preventive measures taken in advance can effectively prevent freezing of drainage ditches and ensure the safe operation of tunnels.

Artificial ground freezing （AGF） is a geotechnical technique widely used in underground construction. It provides temporary stabilization of the soil by freezing the pore water to form a “frozen wall” with sufficient strength and impermeability. This technique is crucial in applications such as foundation pit excavation， shaft sinking， and tunnel excavation， as it can effectively prevent groundwater infiltration， support surrounding strata， and reduce the risk of soil collapse. However， groundwater seepage significantly disrupts the heat conduction mechanism during freezing， leading to a series of critical engineering issues such as redistribution of the temperature field， irregular development of the frozen wall， and increased risk of frost heave deformation at the surface. These issues may eventually cause construction delays， compromise structural stability， and even pose potential threats to surrounding buildings and infrastructure， thereby posing major engineering risks. The influence of groundwater seepage on AGF mainly manifests in three aspects： （1） uneven temperature distribution； （2） irregular development of the frozen wall； and （3） increased risk of frost heave deformation at the surface. First， the convective heat transfer caused by groundwater flow disrupts the temperature gradient distribution that originally relies on heat conduction， resulting in an increased temperature difference between the upstream and downstream sides of the frozen wall. Second， as the freezing front on the upstream side develops slowly due to the obstruction caused by seepage， the frozen wall may exhibit asymmetric growth， thereby weakening its overall structural strength. Third， frost heave deformation is closely related to water migration. Groundwater seepage transports unfrozen water into the freezing zone， where it crystallizes and causes heave deformation within the soil matrix. If not properly controlled， surface uplift may exceed the warning thresholds specified in engineering codes， potentially damaging surrounding buildings. To thoroughly investigate and address the above issues， this study established a numerical model on the COMSOL Multiphysics platform， which enabled the coupled simulation of multiple physical processes of heat conduction， fluid flow， and mechanical deformation. The core objective of this model was to investigate the spatiotemporal evolution patterns of soil temperature and deformation fields during the AGF under different groundwater seepage velocities. By systematically analyzing the influence of groundwater seepage on the formation and evolution of the frozen wall， as well as the mechanisms affecting frost heave deformation at the surface， this study revealed the complex regulatory effects of groundwater flow on the freezing process. The results showed that groundwater seepage significantly increased the temperature gradient between the upstream and downstream regions of the frozen wall. The development of the frozen wall exhibited significant asymmetry because the freezing speed at the upstream front was strongly suppressed by seepage. This asymmetry not only reduced the overall structural performance of the frozen wall but also extended the freezing duration. After construction was completed， the maximum frost heave deformation at the surface may exceed the warning thresholds specified in relevant engineering standards， necessitating measures to prevent damage to surrounding structures. To address this problem， this study proposed a non-uniform layout strategy for freezing pipes， dynamically adjusting the spatial density based on the direction and velocity of groundwater flow. This optimized layout significantly improved the efficiency of cold energy utilization， limited its migration within the soil， promoted the uniform development of the frozen wall， and shortened the freezing duration. Under high seepage velocity conditions （v=0.8 m·d^-1）， the optimized model confirmed the effectiveness of this strategy. After construction， the maximum surface frost heave deformation was controlled below the warning threshold， preventing potential damage to surrounding buildings. By integrating numerical simulation with engineering optimization strategies， this study provides theoretical support and practical guidance for the design and implementation of AGF technology under groundwater seepage conditions. The findings highlight the importance of incorporating groundwater dynamics into AGF system design and provide feasible solutions to enhance the safety and efficiency of underground engineering under complex hydrogeological conditions.

Research on the shear failure process of frozen soil has long been an important topic in geotechnical mechanics in cold regions. The instability of roads and slope failures in frozen soil regions are often accompanied by the progressive failure of frozen soil materials， highlighting the importance of in-depth research on the shear failure behavior of frozen soil. However， conventional triaxial tests face limitations in directly observing the shear failure process under loading. Consequently， the discrete element method （DEM） becomes essential for investigating the mechanical behavior of frozen soil from both macroscopic and microscopic perspectives. In this study， the parallel bond model in the DEM was used to simulate the bonding effect of ice in frozen soil， and a series of discrete element simulations of triaxial compression were conducted to investigate the shear failure process in frozen soil. Additionally， orthogonal experiments were used to study the influence of microscopic parameters such as particle linear group stiffness， bond group stiffness， bond group strength， and friction coefficient on the strength of frozen soil. Multifactor variance analysis was used to explore the sensitivity of these microscopic parameters. The results showed that： （1） Through discrete element simulation of triaxial compression tests on frozen sandy soil under different temperatures and confining pressures， it was found that the stress-strain curves obtained from the simulation closely matched the experimental results， enabling full simulation of the generation， development， and formation of shear bands in frozen soil. （2） A method for determining the width of frozen soil shear bands based on normal distribution functions was proposed. By analyzing the shear bands of frozen sandy soil under different temperatures and confining pressures， it was found that within the experimental conditions of this study， temperature and confining pressure had little influence on the inclination angle of the shear bands. As the temperature decreased or the confining pressure increased， the width of the shear band showed a gradually widening trend. This was because the higher the strength of frozen sandy soil， the larger the plastic zone generated when the soil sample failed. （3） Through sensitivity analysis of the microscopic parameters in the discrete elements， it was found that when the temperature was relatively high， each microscopic parameter had a significant influence on the strength of frozen soil， with the degree of significance ranked in the order of： bond strength > friction coefficient > bond stiffness > linear stiffness. When the temperature was relatively low， the bond strength and friction coefficient had a particularly significant influence on the strength of frozen soil， while the influence of bond stiffness and linear stiffness on frozen soil strength could be neglected. This study mainly explored the discrete element simulation of the triaxial shear failure process of frozen soil under specific temperature and confining pressure conditions. In the future， more extensive experimental data will be used for numerical simulation to further verify the universality of the results. Meanwhile， the correlation between the sensitivity analysis results of discrete element microscopic parameters and the macro- and micro-mechanical mechanisms of frozen soil should be further explored. This study provides a valuable reference for conducting in-depth research on the mechanical properties of frozen soil using DEM.

Sulfate saline soil has the characteristics of salt heave， dissolution-induced subsidence， corrosion， and poor water stability， which cause its physical and mechanical properties to be complex and unstable. Loess-like sulfate saline soil is widely distributed in the seasonally frozen soil regions of northwest China. It exhibits the common unfavorable engineering characteristics of loess and sulfate saline soil and complex occurrence （irregular spatial distribution， poor continuity， surface agglomeration， etc.）. Additionally， it is highly concealed and difficult to control， often leading to engineering issues such as bulging， subsidence， and cracking in various structures. Moreover， due to the influence of the unique climate and environmental changes in northwest China， the salt-frost heave characteristics of loess-like sulfate saline soil are particularly pronounced， often causing engineering problems. Therefore， it is urgent to find an economical， practical， and technically reliable stabilization method. In response to the ineffectiveness of traditional curing agents such as cement and lime in improving the salt-frost heave properties of sulfate saline soil， numerous preliminary tests have found that three materials—zeolite， polypropylene fiber， and calcium lignosulfonate—significantly improved the salt-frost heave properties of loess-like sulfate saline soil， though their influence on soil strength varied， each with its own advantages and disadvantages. Accordingly， this study considered both the strength of saline soil and the improvement in salt heave， proposing the composite use of these three amendments. Based on the response surface method， the optimal mix ratio of these amendments was determined. The composite-improved loess-like sulfate saline soil was prepared under different test conditions using the optimal mix ratio of amendments. The influence of salt content， water content， dry density， amendment dosage， curing age， and number of freeze-thaw cycles on the unconfined compressive strength of saline soil before and after improvement was investigated. The experimental results showed that the unconfined compressive strength of saline soil and improved soil decreased with increasing salt content， water content， and number of freeze-thaw cycles， but increased with higher dry density， amendment dosage， and curing age. Overall， curing age had a minor influence on the compressive strength of saline soil. The composite amendment significantly improved the compressive strength of saline soil， reduced the weakening effects of salt content and freeze-thaw cycles， and enhanced the strengthening effects of dry density and curing age. However， the improvement effectiveness weakened with increasing water content. Furthermore， the composite amendment significantly inhibited the accumulated salt-frost heave deformation and residual salt heave deformation of saline soil under freeze-thaw cycles.

Through resonant column tests， freeze-thaw cycle tests， and scanning electron microscopy （SEM） tests on loess specimens from Xining， Qinghai， the dynamic shear modulus， normalized dynamic shear modulus ratio， and damping ratio of undisturbed loess and remolded soils （with compaction degrees of 80% and 95%） under small strain conditions were systematically analyzed. The analysis was conducted under different freeze-thaw cycle counts （0， 2， 4， 6， 8， and 10） and confining pressures （40 kPa， 80 kPa， and 120 kPa）， and their changes with shear strain γ were examined. The tests used a resonant column device， freeze-thaw cycle chamber， and scanning electron microscope （SEM）. Undisturbed loess samples were extracted from a depth of 6 meters at a construction site in Xining and processed into standard cylindrical specimens. Remolded specimens with compaction degrees of 80% and 95% were prepared by crushing， sieving， and compacting the undisturbed loess while maintaining its natural moisture content. Freeze-thaw cycles were simulated using a bidirectional temperature-controlled chamber to replicate natural conditions. The GDS-RCA resonance column system was used to measure the dynamic shear modulus （G） and damping ratio （λ） under drained consolidation， within the small strain range from 10^-6 to 10^-3. SEM imaging， combined with PCAS software， was utilized for quantitative microstructural analysis， including calculation of porosity and fractal dimension.The results showed that the initial structural properties of loess significantly affected its dynamic properties， with the maximum dynamic shear modulus following the order： remolded soil （95% compaction） > undisturbed soil > remolded soil （80% compaction）. With the increase of freeze-thaw cycles， the dynamic shear modulus decreased， while the damping ratio increased. The maximum dynamic shear modulus of Xining loess decreased most significantly after two freeze-thaw cycles， with a reduction of 17% to 29%， and the dynamic properties stabilized after 4 to 6 cycles. For example， the maximum dynamic shear modulus of the undisturbed soil decreased to 24.37 MPa after 10 freeze-thaw cycles， representing a reduction of 43%. Electron microscopy analysis revealed the microscopic mechanism of freeze-thaw action： the freeze-thaw process dissolved the cementing material between particles， leading to the expansion of the pore network and inducing the development of microfractures. After eight cycles， the porosity increased， and the fractal dimension also increased， indicating the intensification of the disorder in pore distribution. These microstructural changes weakened the internal stress transfer efficiency of the soil， while enhancing its energy dissipation capacity， thus explaining the macroscopic decrease in the maximum dynamic shear modulus and the increase in the damping ratio at the microscopic level.Overall， this study reveals the key deterioration effects of freeze-thaw cycles on the small-strain dynamic properties of Xining loess， with the most significant effects occurring during the initial cycles， after which the effects gradually stabilize. Through quantitative microanalysis， the study clearly establishes the intrinsic connection between microscopic damage mechanisms， such as the dissolution of cementing materials， pore expansion， and microfracture development caused by freeze-thaw cycles， and macroscopic mechanical responses， such as the attenuation of dynamic shear modulus and the increase in damping ratio. This enhances the understanding of the dynamic behavior mechanism of freeze-thaw loess and provides references for engineering applications： when seismic design and infrastructure construction are conducted in cold loess regions， effective protective measures must be adopted to mitigate the deterioration effects of freeze-thaw cycles， thereby ensuring the safety and long-term durability of the projects. This study quantifies the deterioration of small-strain dynamic properties of loess in Xining due to freeze-thaw action and reveals its microscopic damage mechanism， providing valuable references for engineering construction and disaster prevention in the region.

Based on the collected monthly data from 1959 to 2022， including runoff at the mountain outlets of four rivers in the Hotan region， temperature and precipitation from four meteorological stations， and the standard high-altitude temperatures from the Hotan radiosonde station， this study analyzed the trends and abrupt change characteristics in surface water resources on the northern slope of the central Kunlun Mountains. A univariate regression model for the time series was established using the least squares method， with the regression coefficient used to analyze the linear trend of the series. The Mann-Kendall （M-K） test and standardized cumulative anomaly method were employed to identify the years with abrupt changes in the time series. The Pearson correlation coefficient was used to examine the relationship between surface water resources during the flood season and basic meteorological factors， and to test their significance. A response model for surface water resource changes was established based on a multiple regression model to account for variations in multiple factors. Furthermore， the quantitative response of surface water resources on the northern slope of the central Kunlun Mountains to changes in regional climatic factors under different climate backgrounds was discussed. The results showed that from 1959 to 2022， annual surface water resources on the northern slope of the central Kunlun Mountains exhibited 10 years of abnormally high and 10 years of abnormally low values， while the surface water resources during the flood season had 11 years of abnormally high and 11 years of abnormally low values. The annual and flood-season water resources of the four rivers on the northern slope of the central Kunlun Mountains increased at rates of 0.572×10⁸ m³·（10a）^-1 and 0.375×10⁸ m³·（10a）^-1， respectively， both of which passed the 95% significance test. The M-K test indicated that a sudden increase was observed in the annual and flood-season water resources in 2009 and 2010， respectively， with mean values increasing by 28.2% and 21.4% compared to the period before the abrupt changes. Over the past 64 years， the annual average temperature at the four stations on the northern slope of the central Kunlun Mountains in Hotan increased at a rate of 0.319 °C·（10a）^-1， and the precipitation increased at a rate of 4.83 mm·（10a）^-1. The annual and flood-season precipitation in the mountainous areas were 128.7 mm and 110.4 mm， increasing at rates of 10.6 mm·（10a）^-1 and 10.5 mm·（10a）^-1， respectively. The warming rates of the upper-air levels from 700 to 400 hPa for the annual and flood seasons were 0.144 °C·（10a）^-1 and 0.096 °C·（10a）^-1， respectively. Across the 700 hPa， 500 hPa， and 400 hPa levels， the warming rate increased with altitude， with the 400 hPa level showing warming rates of 0.186 °C·（10a）^-1 and 0.180 °C·（10a）^-1 for the annual and flood seasons， respectively. The surface water resources during the flood season on the northern slope of the central Kunlun Mountains exhibited the strongest correlation with the simultaneous 400 hPa temperature， and the correlation with mountain precipitation also passed the significance test. A multivariate linear response model for surface water resources was established based on mountain precipitation and 400 hPa temperature. A comparison of model results under different scenarios showed that from 1959 to 2022， for every 10 mm increase （decrease） in mountain precipitation， the surface water resources during the flood season would increase （decrease） by 0.379×10⁸ m³. For every 1.0 °C increase （decrease） in 400 hPa temperature， the surface water resources during the flood season would increase （decrease） by 10.57×10⁸ m³. From 1991 to 2022， for every 10 mm increase （decrease） in precipitation， the surface water resources during the flood season would increase （decrease） by 0.921×10⁸ m³. For every 1.0 °C increase （decrease） in 400 hPa temperature， the surface water resources during the flood season would increase （decrease） by 11.2×10⁸ m³. Since 1991， the surface water resources on the northern slope of the central Kunlun Mountains have become more sensitive to changes in 400 hPa temperature and mountain precipitation， with the contribution of precipitation variability to surface water resources increasing year by year.

Water resources play a crucial role in achieving the goals of “carbon peak and carbon neutrality”. The shared socioeconomic pathways （SSPs） are divided into a dual-carbon pathway and a high-carbon pathway. This study used climate model data from seven global climate models （GCMs） in the Coupled Model Intercomparison Project Phase 6 （CMIP6） under two shared socioeconomic pathways （SSP1-2.6 and SSP2-4.5）， along with SWAT hydrological models， to project the changes in climate and hydrological variables in the Datong River Basin from 2021 to 2060. The results showed that： （1） Under the dual-carbon pathways， the Datong River Basin was projected to experience a warming and wetting trend from 2021 to 2060. Compared to the baseline period （1995—2014）， the annual average air temperature was projected to increase by 1.4 ℃ and 1.7 ℃， and annual precipitation to increase by 7.4% and 6.9% in the SSP1-2.6 and SSP2-4.5 scenarios， respectively. The increase in precipitation was more pronounced in winter and spring than in other seasons. （2） The multi-model ensemble mean （MEM） annual discharge for 2021—2060 was projected to increase by 3.6% and 5.7% under the SSP1-2.6 and the SSP2-4.5 scenarios， respectively. Discharge was projected to increase in each decade from the 2020s to the 2050s in both scenarios. The increase in the 2040s and 2050s was higher than in the 2020s and 2030s. （3） Under both scenarios， discharge from July to September during 2021—2060 was projected to decrease by less than 1.6%， while it was projected to increase by 0.1%~1.0% from January to June and October to December for most GCMs in the SSP1-2.6 and the SSP2-4.5 scenarios， respectively. （4） For the next 40 years， extremely high monthly discharge was expected to increase by 0.6%~8.2% during the dry season （February-May） in both scenarios but to decrease by 0.1%~3.8% during other periods. Extremely low discharge was projected to increase by 2.1%~9.2% in March and from June to September （flood season） but to decrease by 0.8%~8.3% during other periods in both scenarios from 2021 to 2060. The research findings provide a scientific basis for the ecological environmental protection and rational allocation of water resources in the Datong River Basin.

Soil carbon pools are among the largest carbon reservoirs in the Earth’s surface ecosystems and play a key role in the global carbon cycle due to their large storage capacity. This study took the northern Xizang （Tibet Autonomous Region） as the study area and obtained measured data of soil organic carbon stock and physicochemical properties in the 0~30 cm soil layer through field experiments. Combined with meteorological station data in the study area and meteorological and soil data from sampling points from 2014 to 2023， the DNDC model was driven， calibrated， and validated. Subsequently， the model was employed to simulate soil organic carbon stocks across the study area of northern Xizang. Statistical methods including the coefficient of variation， spatial interpolation， correlation analysis， and partial least squares regression analysis were used to analyze the spatiotemporal characteristics of soil organic carbon stocks in different soil layers of northern Xizang， and quantitatively assess the influence of climatic and environmental factors on soil organic carbon stocks. The results showed that： （1） Based on the results of previous studies and the actual data of the grasslands on the Qinghai-Xizang Plateau， the model parameters were iteratively adjusted through repeated experiments. The R² value between the simulated and measured values from the DNDC model was greater than 0.8， with a root-mean-square error （RMSE） of 5.16 and a Nash-Sutcliffe efficiency coefficient （NSE） of 0.61. The localized DNDC model demonstrated strong applicability for simulating soil organic carbon stocks in the grasslands on the Qinghai-Xizang Plateau， though its simulation results required simple correction. （2） On the time scale， from 2014 to 2023， the soil organic carbon stock in the 0~10 cm soil layer in northern Xizang showed a fluctuating decline trend. The soil organic carbon stock in the 10~20 cm soil layer remained relatively stable， with a slight increase in 2023. In the 20~30 cm soil layer， the soil organic carbon stock was stable from 2014 to 2022 but declined significantly in 2023. On the spatial scale， the soil organic carbon stock exhibited a distribution pattern characterized by low values in the central area and high values around the periphery. The soil organic carbon stock was concentrated in the eastern part of the study area， such as Baqen County， Sêni District， and Lhari County， while it was lower in the central and western parts of the study area， such as Nyima County， Xainza County and Gar County. （3） Average precipitation and soil water content were the main factors positively correlated with carbon storage. In contrast， soil bulk density， pH value， sand-to-gravel ratio， and elevation were negatively correlated factors， and the annual average temperature had a weak influence on the soil organic carbon stocks in northern Xizang. The results of partial least squares （PLS） regression showed that elevation， soil bulk density， sand-to-gravel ratio， and soil water content had relatively strong explanatory importance for the dependent variable （soil organic carbon stocks）. This study holds significant implications for grassland management and ecosystem conservation in northern Xizang. In future carbon pool management， attention should be paid to environmental factors， land use， and ecological restoration measures， especially the importance of precipitation and elevation in the dynamic changes of soil organic carbon. This will promote the stabilization or growth of soil organic carbon stocks. This study provides data support for the carbon cycling processes of grassland ecosystems and offers a practical basis for ecological environmental protection and construction in northern Xizang.

High-altitude glacial ecosystems serve as sensitive indicators of global climate change. Within these systems， aquatic microbial communities， acting as core carriers of biodiversity and ecological function， are crucial for maintaining ecosystem stability. Selin Co， the largest glacier-fed endorheic lake on the Qinghai-Xizang Plateau， provides a unique environment that serves as an ideal platform for investigating the ecological patterns of microbial communities under extreme conditions. This study focused on analyzing the diversity patterns and assembly mechanisms of bacterial communities in the waters of Selin Co Lake and assessing their potential response dynamics to environmental changes. Systematic sampling was conducted in June 2022 at the south shore， north shore， and main inflow of Selin Co. Key physicochemical parameters， including pH， total dissolved solids （TDS）， turbidity （TUR）， and nutrients， were measured concurrently. Using 16S rRNA gene high-throughput sequencing， the bacterial community composition and structure were deeply analyzed， yielding a total of 1 327 612 high-quality sequences clustered into 8 587 operational taxonomic units （OTUs）， spanning 28 phyla and 98 genera， thereby revealing exceptionally high taxonomic diversity. Community structure analysis showed that Proteobacteria， Bacteroidota， and Actinomycetota were the absolutely dominant phyla， with Loktanella， Belliella， and Aquiluna as the predominant genera at the genus level. Although α-diversity indices exhibited no statistically significant differences among sampling regions， richness and diversity showed an increasing spatial trend from the south shore to the north shore and inflow， indicating potential influence of local environmental heterogeneity or hydrological inputs. β diversity decomposition （based on Bray-Curtis dissimilarity） demonstrated that differences in bacterial community composition across the regions in Selin Co were primarily driven by species turnover rather than nestedness， reflecting strong environmental filtering or dispersal limitation. Microbial co-occurrence network analysis showed that bacterial taxa were mainly significantly positively correlated， indicating widespread cooperative interactions or niche overlap within the community. This pattern suggested that implementing “a simultaneous multi-region conservation strategy without prioritization” might be more effective for protecting aquatic microbial diversity than prioritizing specific areas. To further analyze community assembly mechanisms， this study applied both the neutral community model （NCM） and checkerboard score （C-score） test. The results showed that deterministic processes predominated in structuring bacterial communities in Selin Co， while stochastic processes played a relatively minor role. Further linear regression modeling of the relationship between bacterial OTU niche breadth and environmental factors identified pH， TDS， and TUR as key drivers significantly influencing bacterial niche breadth. Using multiple community ecological analytical approaches， this study systematically revealed the high diversity， spatial pattern characteristics， and assembly mechanisms of bacterial communities in Selin Co， Qinghai-Xizang Plateau. The findings provide an important case for understanding microbial biogeography in high-altitude glacial lakes， highlighting the central role of environmental selection in shaping microbial communities within extreme aquatic environments. More importantly， the identified key environmental driving factors （pH， TDS， TUR） are highly susceptible to regional climate changes （e.g.， accelerated input of debris from glacial retreat， altered precipitation patterns， and rising water temperatures）. Therefore， the community-environment relationship model established in this study provides a solid scientific foundation for predicting the dynamic responses of microbial community structure and function in Selin Co and similar high-altitude glacial lake ecosystems under future climate change scenarios. This study holds significant scientific value for assessing the impact of global change on vulnerable alpine aquatic ecosystems and for formulating conservation strategies.

The Narati-Baluntai section of the G218 Highway （Naba Highway） in Xinjiang is located in the central region of Tianshan Mountain. The region experiences frequent and severe blowing snow disasters， making risk level assessment critical for the prevention and control of highway snowstorms. However， current blowing snow risk level prediction methods for mountain highways suffer from overly complex indicator selection， resulting in low operational applicability for engineering design. This study utilized meteorological station data from Naba Highway， combined with reanalysis of snow depth data and other auxiliary data， to identify 13 indicators influencing blowing snow risk level. Based on the above indicators， this study established the GA_XGBoost prediction model for blowing snow risk level on highways. This model employed Lasso feature selection to identify five high-contribution disaster-inducing indicators， including snow depth and wind-road angle. Then， using genetic algorithm-based hyperparameter optimization， this study searched for the optimal solution of the XGBoost model to establish the wind-blown snow risk level prediction model. Finally， the simulation results were validated using field data from the Naba Highway. The validation results showed that： （1） the blowing snow risk level predicted by the proposed model was accurate， and the model outperformed traditional models. （2） The distribution of blowing snow risk levels on the Naba Highway was relatively complex. Both model calculations and field surveys indicated that the core high-risk zones were located at Aiken Daban and Chahan Nuur Daban， where westerly winds dominated blowing snow.