Slope regulation and storage measures (SRASM) are critical for soil and water conservation in the Middle Reaches of the Yellow River (MRYR). These functions are largely delivered by specific land use/cover (LULC) types, such as forest, grassland, and terrace. However, the resilience (recovery and resistance) of these LULC under flood stress is still unclear. This study focuses on the three LULC mentioned above, using the resistance and recovery performance of the three LULC after a flood event as the basis for determining resilience under flood stress. Evaluation methods for flood events and calculation methods for resistance and recovery are proposed, and the resilience under flood stress of different LULC and sub-watersheds in the MRYR are analyzed. The results indicate that, flood events in the MRYR mostly occur in summer (61.8%), and the number of floods decreases from southeast to northwest; three LULC exhibit flood resilience, with grass showing superior recovery and forest demonstrating great resistance; as the slope increases, the number of severe flooding increases and resilience decreases; From a spatial perspective, the recovery of the MRYR is higher in the western region than in the eastern region. The resilience of the MRYR is strongest on the sub-watershed Right bank above Wubao (D040200). This study aims to provide scientific basis for improving water resource management and ecological protection under flood stress environment in the MRYR.

Extreme precipitation，severe flooding，widespread droughts，and compound disasters occur more frequently as the "non-stationary" features of the global water cycle become more obvious. When confronted with "low-probability，high-impact" natural disasters，the traditional approach of "defense based on historical patterns," which assumes climate stationarity，suffers from a lack of adaptation. By investigating the conceptual chain of "flood-drought-disaster-impact-prevention-resilience," this study points out a systemic bias in the present approach. This bias emphasizes structural prevention over adaptive resilience and disaster control over damage mitigation. We establish a new paradigm of "intelligent adaptation to uncertain extreme" in response，along with its practical applications. According to the study，a modernized flood and drought defense system should: apply the National Water Network as a strategic carrier to improve spatiotemporal water reallocation capacity; use smart water management as the main driver for establishing a closed-loop system that combines "perception-forecasting-simulation-decision making"; with ecological measures as a resilience foundation to promote "grey-green synergy" in systemic governance. Additionally，the perspectives of energy dynamics and social psychology expand the theoretical bounds of disaster comprehension and defense evaluation. The aim of this study is to offer a theoretical foundation and workable solutions to establish a new-generation flood and drought mitigation system that will withstand unpredictable conditions in the future.

Drought-flood abrupt alternation (DFAA) events are an important manifestation of instability in the global climate system and pose substantial risks to society and ecosystems. However, the risks that DFAA events impose on affected systems have not yet been systematically quantified at the global scale. Based on the three key components of hazard, exposure, and vulnerability, this study applies a multiplicative model to assess global DFAA risk, develops a "double-mean, double-threshold, and double-driver" analytical framework, quantifies the effective risks of DFAA events to social and ecological systems, and identifies their major influencing factors. The results showed that, although the global mean DFAA hazard increased slightly, regional differences are pronounced. The social system exhibited a pattern of increasing exposure and decreasing vulnerability, whereas the ecosystem showed simultaneous increases in both exposure and vulnerability. Although the spatial extent of flood-to-drought risk was smaller than that of drought-to-flood risk, it was more destructive in some regions. The overall centroid of social system risk shifted toward the southeast and southwest, whereas that of ecosystem risk shifted toward the northeast. The mechanisms driving risk also showed pronounced asymmetry, with socioecological system factors dominating during the drought-to-flood stage and climatic factors playing a leading role during the flood-to-drought stage. Overall, this study reveals the differences in DFAA risk and the asymmetric driving characteristics affecting social and ecological systems at the global scale, providing a scientific basis for risk warning, adaptive management, and sustainable development decision-making related to DFAA events.

Groundwater in alpine source regions plays a crucial role in sustaining regional water cycles and safeguarding downstream ecological security. However, a systematic understanding of its dynamic response to climate change and associated hydrological functions remains limited. In this study, we employed a distributed hydrological model that integrates ground observations and CMIP6 climate projections under four SSP scenarios (SSP126, SSP245, SSP370, and SSP585) to simulate groundwater-depth evolution and quantify its runoff contribution in the Nu-Salween River headwaters (Qinghai-Tibet Plateau) for 1960-2100. Results reveal that groundwater depth deepened overall during the historical period, with pronounced spatial heterogeneity. Future projections exhibit distinct nonlinear behaviour: widespread deepening is expected before 2060, followed by regionally divergent trends thereafter. This nonlinear groundwater response appears to be driven not only by climate change but also by the degradation of permafrost. In the composition of runoff, the long-term mean groundwater contribution remains stable at roughly 10 %, while its seasonal regulatory effect intensifies. Specifically, the groundwater share of runoff in winter and spring is projected to increase by 2.0-2.6 %, highlighting its critical role in sustaining dry-season flows in cold plateau environments. These findings reveal the nonlinear evolution of groundwater depth under climate change and its regulatory influence on runoff, providing a solid scientific basis for advancing research on alpine water cycle mechanisms and for guiding adaptive water resource management in cold plateau regions.

Climate warming has impacted the sustainability of freshwater supply in the global water tower unit (WTU) zone. The rainfall infiltration process, a key component of WTUs supply, is affected by freeze-thaw cycles, yet it remains uncertain whether it has undergone corresponding changes. We propose a temperature-mediated infiltration model considering changes in soil water holding, water potential, and hydraulic conductivity due to varying degrees of freezing under negative temperature. Using this model, we calculate the infiltration of 78 WTUs globally from 1980 to 2023. Our results indicate that global WTUs have a multi-year average infiltration of 26 similar to 2359 mm/year. Notably, WTUs in the key latitudinal zone (24 degrees S-42 degrees N) contribute 54 % of the total infiltration volume, showing expanding differences in infiltration characteristics compared to other regions. While rainfall primarily influences infiltration and infiltration capacity, soil temperature and initial soil water content also significantly impact these characteristics. Enhanced infiltration capacity promotes vegetation growth, though the relationship is not linear. Variations in infiltration characteristics threaten the water resource buffering and the stability of downstream living ecological water supply of WTUs. This study provides crucial references for the integrated management of water resources and ecological conservation amid changing infiltration characteristics.

Under global climate change, agricultural and ecological droughts in the Middle Reaches of the Yellow River (MRYR) severely threaten agricultural production and ecological security. However, the lack of large-scale, highspatiotemporal-resolution layered soil moisture data constrains the precise identification of droughts. This study innovatively integrates a Multi-Layer Perceptron (MLP) model with RegCM4 climate scenario data to generate a layered daily-scale soil moisture dataset for the 0-289 cm profile in the MRYR from 2001 to 2100 (Abbreviated as MLP_D). The MLP_D dataset features a spatial resolution of 0.01 degrees x 0.01 degrees and demonstrates superior performance to traditional data products across multiple metrics. Analysis of the MLP_D dataset reveals: During 2001-2022, surface soil moisture (0-7 cm) exhibited a slight, non-significant increasing trend at a rate of 0.0002 m3 /m3 /year, while soil moisture in layers below 7 cm declined, in 100-289 cm, the soil moisture decreasing significantly at 0.0016 m3 /m3 /year. Moreover, MLP_D data accurately captured typical drought events, demonstrating high consistency between simulated and actual observations. Future drought frequency and duration in the MRYR increase with more intense scenarios, under the RCP8.5 scenario, areas experiencing a significant increase in drought duration account for 71 % of the total region. By bridging a critical data gap in high-resolution, long-term, layered soil moisture data for the MRYR, this study provides pivotal insights into climate change impacts on soil moisture and drought regimes. It thereby serves as a scientific basis for enhancing precision agriculture and water management, with profound implications for mitigating drought risks and safeguarding regional agro-ecological security.

The fluctuation of groundwater levels during the freeze-thaw period exhibits a close connection with the hydrothermal variations in the surface soil. However, the underlying mechanisms and the extent of their correlation have not been thoroughly explored, which is crucial for understanding the evolution of groundwater circulation in permafrost regions under the context of climate change. This study utilizes field observation data from different permafrost regions in the central Qinghai-Tibet Plateau, proposing a calculation method for soil water potential and permeability coefficients suitable for freeze-thaw environments. It quantifies the contribution of freeze-thaw action to the fluctuation of shallow groundwater levels and analyzes the changes in the hydraulic conductivity of surface soil and their driving effects on shallow groundwater level fluctuations. The results indicate that groundwater level fluctuations are synchronized with the freeze-thaw process. The movement of the freeze-thaw front exhibits a quadratic polynomial relationship with the cumulative changes in groundwater level, with the highest amplitude of fluctuation and fitting degree observed in the continuous permafrost regions of high mountains. During the freeze-thaw period, hydrothermal variations in the soil lead to changes in hydraulic conductivity (comprising permeability coefficient and water potential gradient), thereby driving groundwater level fluctuations by modifying the direction and efficiency of water transport. The extent of freeze-thaw effects on groundwater level decline during this period varies between 3.97 +/- 1.66 % - 64.49 +/- 35.17 %, and is governed by various factors including initial groundwater depth, soil particle size distribution, and lateral water recharge and discharge conditions. These research results are instrumental in evaluating the impact of climate change on water resources in cold regions, and offer a scientific foundation for water resource management and ecosystem conservation.

Climate warming has been documented to amplify evapotranspiration (ET) in alpine meadows through multifaceted mechanisms. However, how root tip morphological adjustments-a critical control point for belowground water acquisition-mediate warming-induced ET intensification remains unresolved at the ecosystem scale, particularly across the Qinghai-Tibet Plateau (QTP) where these processes govern regional hydrological sustainability. This study employed a five-year field experiment using open-top chambers along an altitude gradient in central QTP, used root morphology parameters such as root tip density (RTD) as an entry point to explore the morphological characteristics of the root system under climate change, and improved the root water uptake model based on the distribution function of RTD to analyze the effects of warming on the water uptake pattern and transpiration characteristics of the root system of alpine meadow on the QTP. Key findings revealed that: (1) Root morphological adaptation: Increasing temperature promotes the growth of root in alpine meadows. About 80 % of the roots are distributed in the 0-25 cm soil layer, and the RTD first increases and then decreases with the increase of soil depth. (2) Altitude-specific water uptake: In lower altitude areas, the root water absorption intensity is higher. Under warming treatment, the root water absorption intensity first increases and then decreases with soil depth, with the highest root water absorption intensity in the 5-20 cm soil layer. (3) Transpiration amplification: For different climate change scenarios, for every 1 degrees C increase in soil surface temperature, the transpiration of the alpine meadow on the QTP will increase by about 21.2 similar to 22.43 %. During the growing season of the alpine meadow, the transpiration increase in August is as high as 24.62 similar to 25.87 %. The study highlights a mechanistic link between root functional traits, soil thermal regimes, and ecosystem water fluxes. The study helps to understand the hydrothermal balance under climate change and provides theoretical support for ecological restoration in high-cold regions.

Study region: Northern Anhui Plain, China. Study focus: This study analyzed the nitrogen (N) mitigation (N storage in soil, plants, and surface runoff) under drought-flood abrupt alternation (DFAA) in summer maize farmland systems based on field experiments. Soil N loss due to DFAA in the summer maize planting area of the Northern Anhui Plain was simulated based on the critical threshold obtained from the field experiments. New hydrological insights for the region: The experimental results showed that DFAA events reduced soil N storage and plant N storage by 14.9 % and 54.1 % compared to the control systems, respectively, while N storage in the water component of surface runoff in the DFAA treatments was 54.1 % higher. Numerical simulations revealed that the proportions of average annual soil N loss in topsoil were 14.98-19.58 % from 1964 to 2017 and 10.22-22.75 % from 2020 to 2050 in the study area. The highest average annual soil N loss shifted from the southwestern to the central and southeastern Northern Anhui Plain. The highest soil N loss in the hypothetical natural scenario was 49.0 % and 46.7 % lower compared to historical and future scenarios, respectively. The findings indicate that DFAA has significantly negative impacts on water quality. The quantitative analysis provides a reference for developing targeted regulation measures for the Northern Anhui Plain facing compound extreme events.

Considering that active layer (AL) thickening is a phenomenon of permafrost degradation, early observations primarily focused on frozen ground types (i.e., permafrost and seasonally frozen ground) or the Active Layer Thickness (ALT). However, existing studies have paid little attention to the correlation between lateral degradation of permafrost and vertical thickening of the AL, as well as the contribution of meltwater during the thickening of the AL to vegetation greening on a large scale. Using 1,053 records of AL observation data from 2000 to 2020, five causal relationship models, and three data-driven methods, this study estimates the relationship between the vertical evolution trend of ALT and the lateral degradation of permafrost, while also exploring the contribution of meltwater from permafrost to vegetation growth. The results indicate that the average ALT on the Tibetan Plateau (TP) ranged from 1.03 to 3.73 m during 2002-2020. Furthermore, the TP is delineated by the Yarlung Zangbo, Nujiang, Lancang, Yangtze, and Yellow River basins. Permafrost degradation in the northwest region accelerates the thickening of AL in permafrost areas at a rate of 0.006 m/a. In contrast, in the southeast, it accelerates the thickening of AL in degraded permafrost areas at a rate of 0.004 m/a. Meanwhile, frozen ground degradation is more susceptible to extreme values of temperature, Land surface temperature, precipitation, and wind speed. During the thawing process, soil moisture may accumulate in deeper layers, resulting in an average contribution rate of the altered hydrological environment caused by degraded permafrost to vegetation growth of less than 2.29 %. This research provides a deeper understanding of the interactions among frozen ground, soil, and vegetation at a large scale. The interannual variations in ALT will further reduce the uncertainty about the thermal state of permafrost and its future response.

Drought-flood abrupt alteration (DFAA) events threaten global food security, exacerbated by global warming, particularly in China. Given this, a more refined and comprehensive analysis of DFAA events in China can provide valuable insights for global mitigation efforts. This study examines the frequency, intensity, and coverage of DFAA events during the historical periods (HIS, 1961-2014) and under future climate projections based on Shared Socioeconomic Pathways (SSPs: SSP126, SSP245, SSP370, SSP585, 2015-2100) using a daily-scale determination method. The results revealed that regions with frequent DFAA events also experience higher intensity and broader impact areas. Compared to HIS, DFAA event frequency, intensity, and coverage increased by 31 %, 3 %, and 37 % under SSPs, reaching 7.31 events/year, 1.069, and 0.422 %. Across both HIS and SSPs, the proportions of light (75 %-78 %), moderate (18 %-21 %), and severe (4 %-5 %) DFAA events remained relatively stable. YGP, HHHP, MLYP, NCP, and NASR are the five hotspot areas. Analysis attributes 45 % (P < 0.05) of DFAA frequency variability to drought and flood frequency (74.45 %) and duration (25.55 %). Furthermore, low to medium emission scenarios show significant potential to reduce DFAA occurrence, offering direction to mitigate the impacts of global warming, particularly as mid-latitude regions have emerged as DFAA hotspots over the past 30 years. These findings provide critical insights for countries addressing climate change and ensuring food security.

Groundwater is a crucial water resource of the Qinghai-Tibet Plateau (QTP), accounting for about 85% of the total water resources. However, the scarcity of data on groundwater storage (GWS) changes limits our understanding of its response to climate warming and cryosphere degradation. In this study, we combined GRACE/ GRACE-FO satellite gravimetry, ICESat-2 altimetry, GLDAS land-surface model outputs, and in situ groundwater observations to quantify spatiotemporal GWS changes across the QTP from 2004 to 2020 and analyse the controlling factors of GWS changes. Results indicate that internal and external factors jointly control GWS on the QTP. With the Pamir-Karakoram-Gangdise-Tanglha-Hengduan Mountains as the boundary, GWS exhibits an increasing trend in northern QTP and a decreasing trend in southern QTP. Accelerated permafrost degradation both increases soil permeability and enhances its water-holding capacity. In the gently sloping central-northern region, abundant glacier-snow meltwater combined with favourable topography creates conditions for GWS to rise. Conversely, the pronounced relief of the southern, western, and eastern sectors restricts effective meltwater recharge to aquifers. At the same time, higher evapotranspiration and reduced precipitation in the south and west may also lead to declines in groundwater storage. These findings highlight the heterogeneous impacts of climate change on groundwater resources across different hydrogeological zones of the QTP. The results provide important scientific support for regional water resource management and adaptation planning in the face of ongoing environmental change.

Thermokarst lakes (TLs) and retrogressive thaw slumps (RTSs) are common thermokarst landscapes that play a crucial role in regulating hydrology, ecology, and biogeochemical elements in permafrost regions. However, how TLs, as water accumulation units, affect regional water imbalances remains unclear, and whether the slow movement of shallow soil material from RTSs disrupts ecosystem barriers is still unknown. Additionally, it is uncertain whether the expansion of TLs is influenced by RTS-induced disruptions to surface water flow paths. In this study, we integrated previous research, field surveys, and remote sensing imagery to determine the evolution patterns, spatial extent, and interactions between 39,766 TLs and 1,680 RTSs on the Qinghai-Tibetan Plateau (QTP). We further employed the eXtreme gradient boosting algorithm and ICESat-2 ATL08 laser altimetry data to quantify changes in water storage due to TLs. The results revealed that TLs and RTS followed different evolutionary trajectories from 2000 to 2020. Overlapping impact areas were observed only in the headwaters of the Changjiang River, where 22 TLs and 21 RTSs co-occurred, indicating that TL formation is mainlyunaffected by RTSs. Additionally, 98% of RTS patches showed increasing NDVI trends after losing their mattic layer, demonstrating that RTSs do not impose irreversible suppression on vegetation growth. This study also comprehensively quantified how TLs contribute to regional water imbalances across regional, sub-basin, and patch scales. Summarizing and identifying the links between TLs and RTSs at a large scale can provide valuable insights into the feedback mechanisms between ecological hydrological processes and climate warming in permafrost regions, offering a reference for similar studies.

Study region: Typical alpine meadow soils on the central Qinghai-Tibet Plateau Study focus: This study applied the DHC-FVAM (Dual-Porosity Hydraulic Conductivity–Flow Velocity in Alpine Meadows) model to quantify contributions of connected and isolated pores to soil permeability during frozen soil thawing. Despite their established roles in permeability, quantitative insights remain limited. New hydrological insights for the regions: The results show that during the initial thawing stage, connected pores contribute 62.83 % more to total soil permeability than isolated pores, with values of (1.53 ± 1.13) × 10−10 m/s and (8.87 ± 0.30) × 10−11 m/s, respectively. Upon complete thawing, this contribution rises to 83.74 % greater, with permeability values of (2.20 ± 1.17) × 10−10 m/s and (8.67 ± 0.30) × 10−11 m/s, respectively. As frozen soil transitions from initial to complete thawing, the volume fraction of connected pores increases by 10.49 %, and connectivity rises by 155 %, driving the nonlinear permeability surge. This surge is attributed to the freeze-thaw-induced coalescence of isolated pores into connected pores, where the increase in connectivity enhances flow path efficiency and reduces tortuosity, thereby amplifying soil water transport capacity in a nonlinear manner. These findings highlight the dominant role of connected pores in water transport in alpine meadow soils, improving understanding of hydrological processes in alpine regions and offering a scientific foundation for climate-adaptive water management and ecological conservation.

Soil's water-holding and conducting properties are crucial for studying soil-water relations. This research explores how soil pore structure affects water-holding capacity and hydraulic conductivity in alpine meadow soils of the central Tibetan Plateau. The study critiques the Campbell formula for inaccurately predicting these factors, citing a lack of consideration for specific soil properties and contexts. Incorporating soil pore curvature, a revised method enhances the accuracy of the Campbell formula. During the growing season, independent pores in alpine meadow soils often interconnect, featuring large surface areas but small volumes. These soils, with higher clay content than loamy and sandy soils, demonstrate a high water-holding capacity. However, in the growing season, this capacity diminishes, and hydraulic conductivity rises due to reduced pore curvature in these cold alpine meadows.

Under the influence of global change, precipitation amounts and extreme precipitation frequency during non-growing seasons in mid-high latitude grasslands have been increasing. However, the ecological effects of non-growing season precipitation in the desert steppe have long been overlooked due to an insufficient understanding of the correlative mechanisms linking non-growing season precipitation to plant growth. Therefore, a 3-year non-growing season precipitation manipulation experiment was conducted to reveal the response of desert steppe plants to non-growing season precipitation changes. Our study indicates that, by influencing water budget and availability, non-growing season precipitation directly or indirectly impacted community structure, plant biomass allocation, and water-carbon utilization intensity. Adaptive strategies of communities and plants included: ① Dominant species enhanced their dominance in the community to adapt to non-growing season precipitation changes. ② Stipa krylovii exhibited different biomass allocation strategies in response to non-growing season precipitation variations. Plants in the precipitation shading plots tended to allocate biomass to the roots, while those in the precipitation increase plots favored aboveground development. ③ Persistent drought during the growing season intensified early insufficient development of plants in the precipitation shading plots. Upon entering the wet period, plants in the precipitation shading plots shifted into a compensatory growth mode with high water-carbon activity intensity, while those in the precipitation increase plots entered a moderate growth mode with relatively low water-carbon activity intensity. Additionally, our study found that the regulatory effects of non-growing season precipitation were more pronounced in the growing seasons with less precipitation in the early to middle stage. Moreover, increased non-growing season precipitation enhanced plant water use efficiency (WUE) and strengthened their resilience to drought conditions. Our study suggests that the ecological role of non-growing season precipitation may be further highlighted in the future climate change pattern. Given the worldwide increase in frequency of extreme precipitation events, particular vigilance should be paid to the underlying long-term adverse effects of severe droughts during the non-growing season. Our findings provide new insights and valuable experimental observational evidence for the climate change impact assessment and response in xerophytic grassland ecosystems.

It has been widely reported that anthropogenic influences are detectable with high confidence in global warming. However, whether human activities have an impact on snowfall changes is still unclear. Here we based on phase 6 of the Coupled Model Intercomparison Project (CMIP6) multi-forcing dataset and the regularized optimal fingerprint method, the detection and attribution of various grades of snowfall (including annual snowfall (>0.1 mm/day), light snowfall (<2.5 mm/day), intense snowfall (>5 mm/day), and their corresponding days) changes in Eurasia (20°-90°N, 10°W-180°E) were carried out. Results show that anthropogenic activity forcing (ANT) and greenhouse gas forcing (GHG) well reproduced the spatial-temporal characteristics of snowfall indices. The ANT influence is robustly detected in the decreased trend of snowfall days (snowday), light snowfall, and light snowfall days (light_day) at the 90% confidence interval, clearly separated from the natural forcing. Moreover, the GHG signals are detectable for decreases in the three snowfall indices, which only could be distinguished from the natural and aerosol forcings for snowday and light snowfall. Thus, anthropogenic activities may considerably account for the decreases in snowday, light snowfall, and light_day across Eurasia, wherein the changes in the first two indices dominated by GHG emissions. However, human influence detections fail for intense snowfall, and it is hard to detect on regional scales, except for North Asia. Finally, by the end of this century (2081–2100), the observation-constrained projections based on the detection and attribution analysis under two SSPs (new Shared Socioeconomic Pathway) scenarios exhibit that the scaled snowday, light snowfall, and light_day are expected to decrease by approximately 13.9 days (28.3 days), 24.8% (48.7%), and 4.3 days (8.8 days) under the SSP2–4.5 (SSP5–8.5) scenario with reference to the current climate (1995–2014). Our study highlights the need to improve climate model performance in simulating extreme snowfall to clear whether and to what extent human influence impacts it.