Subalpine forest soils are critical yet underexplored regulators of terrestrial carbon (C) cycling, and climatedriven changes in litter input may trigger nonlinear feedbacks between soil respiration (Rs) components and microbial network dynamics. This study presents a comprehensive three-year (2019-2021) field experiment investigating the differential impacts of litter addition and removal on Rs components and soil microbial communities in coniferous and broad-leaved subalpine forests. Litter addition increased Rs and autotrophic respiration (Ra) but had limited effects on heterotrophic respiration (Rh), leading to a decrease in Rh/Rs ratio (57.33%-63.48%) in both forests. In contrast, litter removal suppressed Rs, Ra, and Rh across the two forests, with a more pronounced reduction in Ra than Rh, resulting in increased Rh/Rs ratio (72.47%-74.19%). The effects were more pronounced in broad-leaved forest. Litter manipulation also significantly altered soil microbial community structure and co-occurrence network topology. Litter addition increased fungal network complexity, whereas litter removal enhanced the complexity of the fungal network and promoted bacterial network cooperation (evidenced by reduced modularity and shortened path length), ultimately reducing the stability of fungal and bacterial networks. Root exclusion amplified shifts in fungal diversity and microbial biomass C (MBC) under litter manipulation, thereby highlighting the reliance of microbial restructuring on root-derived resources. Structural equation modeling identified 16S rRNA gene abundance as the primary regulator of Rs, surpassing the effects of microbial diversity and network complexity, while Rh was co-regulated by bacterial network complexity and 16S rRNA gene abundance. These findings highlight the dual role of litter in driving microbial community restructuring and respiratory partitioning, emphasizing the critical role of microbial functional traits over taxonomy and the divergent regulation of respiration components by microbial abundance versus network architecture, for predicting soil C feedbacks.

Understanding how soil nitrogen (N) responds to climate warming is critical for predicting permafrost carbon–climate feedbacks, yet long-term N responses and their underlying mechanisms remain elusive. Here we show that divergent topsoil N responses to warming are associated with warming-induced shifts in soil moisture. Twelve-years of high-level warming increases topsoil N stocks in mesic alpine meadows but triggers substantial topsoil N losses in waterlogged swamp meadows. Enhanced topsoil N retention in the alpine meadow coincides with warming-driven soil drying, reduced gross protein depolymerization, and elevated microbial N immobilization. By contrast, declining topsoil N stocks in the swamp meadow coincide with elevated soil moisture, accelerated N transformation rates, greater plant N accumulation, and elevated potential N losses. A meta-analysis further indicates that such moisture-associated divergent N responses are widespread across permafrost-affected ecosystems. These findings highlight the necessity of hydrological shifts when projecting N cycling and permafrost-climate feedbacks under climate warming. A 12-year warming experiment shows divergent responses of topsoil nitrogen stocks to warming in alpine and swamp meadows, with these contrasting responses associated with warming-induced shifts in soil moisture.

Divergent phenological shifts among trees, shrubs, and grasses in forest ecosystems have the potential to fundamentally reshape forest structure and productivity across vertical strata. However, our understanding of the interrelationships among these plant functional types under long-term climate warming remains limited due to a lack of systematic and extended studies. Here, we present results from a 20-year phenological monitoring experiment in an alpine forest ecosystem, systematically tracking the phenology of trees, shrubs, and grasses under climate warming. Our results show that the growing season of trees lengthened by an average of 0.2 days per year, primarily driven by a significant delay in leaf discoloration and defoliation. In contrast, shrubs and grasses experienced shortening growing seasons, with average reductions of 0.43 and 2.62 days per year, respectively. While shrubs exhibited delayed budding, leafing, and flowering, grasses showed significant advancement in defoliation timing. Changes in vegetation cover corresponded to phenological shifts: tree cover increased, while shrub and grass cover declined. These findings suggest that climate warming may weaken forest hierarchical structure by disproportionately enhancing tree growth over understory vegetation. Differential phenological responses across forest strata should be a focal point in climate impact assessments.

Determining the optimal measurement timing for soil greenhouse gas (GHG) emissions is essential for improving the accuracy of GHG budgets and deepening understanding of underlying biogeochemical mechanisms. However, due to a lack of high-temporal-resolution and continuous data, the optimal measurement timing of CH4 and N2O emissions remains poorly understood-especially compared to the extensively studied CO2. Based on hightemporal-resolution and continuous in-situ observations, we found clear differences in the optimal measurement windows among CO2, CH4, and N2O. The optimal timing for capturing daily mean CO2 fluxes was relatively stable across seasons (around 09:00-11:00), whereas no well-defined optimal daily measurement windows could be identified for CH4 and N2O. Instead, their fluxes exhibited highly variable and irregular temporal patterns. Importantly, applying the CO2-based timing to estimate N2O fluxes resulted in a substantial underestimation (up to 24%), underscoring the risk of using uniform measurement strategies for different gases. This study reveals that the applicability of optimal daily time windows differs strongly among CO2, CH4, and N2O and across seasons, offering key insights for improving flux estimates.

Permafrost regions store vast amounts of soil organic carbon (SOC), yet SOC responses to warming have remained inconsistent across studies. In particular, previous research has primarily focused on bulk SOC measurements, an approach that obscures fraction-specific responses and hinders mechanistic understanding. We therefore investigated responses of SOC and its fractions in two representative permafrost grasslands contrasting in their hydrological and biogeochemical conditions on the Qinghai–Tibetan plateau. Open-top chamber warming experiments were conducted in an alpine meadow and a swamp meadow to yield average warming of + 2.4 °C (future 2 °C scenario) and + 4.9 °C (future 4 °C scenario) over 9 and 12 years, respectively. We analyzed SOC and its fractions, particulate (POC), mineral-associated (MAOC), calcium-bound (Ca-OC), iron-chelated (Fe3⁺-OC), and reactive mineral–associated carbon (OCDP) at 0–10 and 10–20 cm soil depths. Additionally, we characterized the chemical composition of SOC fractions (derived from UV and fluorescence spectroscopy), aboveground biomass, and soil mineralogical properties to identify the drivers of SOC responses to warming. In alpine meadows, 12-yr high warming significantly increased bulk SOC, Ca-OC, Fe3⁺-OC at both depths (p < 0.05). Swamp meadows showed stable bulk SOC, but increased Ca-OC and decreased OCDP. Regression and redundancy analyses revealed alpine SOC accumulation via enhanced plant inputs and metal associations. In contrast, swamp SOC was constrained by Ca-OC formation offset by OCDP decomposition under waterlogged conditions. Ecosystem-dependent SOC responses to warming are mediated by fraction-specific dynamics. Incorporating fraction-specific responses into carbon cycling models is critical for improving predictions of permafrost soil carbon dynamics under future climate change.

Global warming has increased the frequency and severity of climatic extremes, reducing the predictability of vegetation responses in the Hindu Kush Himalaya (HKH), a region warming at about twice the global rate. Here we show that vegetation loss is partitioned along elevation, with grasslands experiencing the largest reductions at 2500 to 4500 m (11 to 16%). Drought remains the dominant single stressor across 43.09% of the study area, while losses intensify under compound extremes, averaging 14.4% compared with 1.39% under single stressors. Compound drought and heat (CDHW) produces the broadest footprint, affecting about 76% of the region. Amplification is driven by coordinated drought and heat deviations, rather than additive effects, and is strongest in humid zone, increasing from −1 to 1.8σ, with peak sensitivity at 2000 to 3500 m. About 61.6% of CDHW events reflect an extreme deviation in a single stressor, whereas events driven by concurrent increases in both stressors occur mainly above 4500 m. Furthermore, controls shift from drought in dry areas to other stressors in humid zones and at lower elevations, while compound extremes exhibit mode diversity during the monsoon, most clearly in low elevation humid zones during January to March and August to December. Rare severe loss events are linked to cold stress (0.68σ), whereas compound losses depend more on event occurrence than on the specific stressor combination. These findings highlight the need to incorporate compound extremes and elevational sensitivity into future HKH vegetation risk assessments rather than relying on single stressor responses alone.

Soil organic carbon (SOC) comprises particulate (POC) and mineral-associated organic carbon (MAOC), which differ in formation, stabilization, and loss mechanisms. While the current global distribution of POC and MAOC is characterized, their vulnerability under future climate scenarios remains unclear. Using 3284 topsoil (0-30 cm) observations from six continents, we identify high-latitude soils as global hotspots of SOC vulnerability under shared socioeconomic pathway scenarios (SSP126, SSP245, and SSP585). Under a high-emission scenario (SSP585), high-latitude soils are projected to lose substantial POC by 2100, accounting for about 81 ± 10% of total SOC losses. These declines are driven by the high proportion of SOC stored as POC (fPOC) and its high temperature sensitivity. We show that fPOC is a robust indicator of SOC vulnerability to climate change. Globally, the projected POC decline corresponds to a cumulative carbon dioxide (CO2) release of 81.34 Pg CO2-equivalent by 2100, highlighting the importance of preserving POC to mitigate climate feedbacks.

The lateral transport of dissolved organic carbon (DOC) from terrestrial uplands to aquatic ecosystems, particularly headwater streams, plays a critical role in linking terrestrial and aquatic carbon cycles, but its spatial distribution and magnitude at the global scale remain highly uncertain. Here, we compiled 20,403 field-based DOC concentration measurements and modeled them against catchment properties to generate monthly predictions across over 90,000 forested catchments (30°S-70°N). These models explain between 64% and 90% of the total variability in DOC concentrations (R2 values from predictions versus withheld observations), revealing previously unrecognized hotspots of terrestrial-aquatic carbon transfer. By coupling these predictions with a physically-based hydrological routing scheme (HydroBASINS database), we provide the first catchment-resolved estimates of DOC yields. This dataset represents a valuable resource for the carbon-cycle community, supporting the validation of terrestrial biosphere models and cross-checking of datasets.

Carbon (C), nitrogen (N), and phosphorus (P) are fundamental elements for plant growth and metabolism. Leaf C-N-P stoichiometry provides critical insights into plant nutrient use efficiency and ecosystem-scale carbon-nutrient interactions, particularly under global change. However, comprehensive long-term records of leaf C, N, and P concentrations remain scarce. Here we compiled and publicly released the Leaf Carbon-Nitrogen-Phosphorus Concentrations in China's Forests (CNP-China) dataset, containing 628 standardized records from 52 dominant tree species across 11 representative China's forest ecosystems from 2005 to 2020. All samples were collected and analyzed following the Chinese Ecosystem Research Network (CERN) protocols, with accompanying plot-level geographic and environmental data, species taxonomy and functional traits, and surface soil properties (0-20 cm depth). The dataset underwent rigorous quality control, including unit harmonization, error checking, and outlier detection, and is provided in accessible CSV format. CNP-China enables critical assessments of stoichiometric responses to environmental change, supports improved ecosystem modeling, and facilitates cross-biome comparisons of nutrient cycling dynamics, providing an essential foundation for understanding forest carbon-nutrient feedback under global change.

Huge phages (genome size ≥ 200 kb) have been detected in diverse habitats worldwide, infecting a variety of prokaryotes. However, their evolution and adaptation strategy in soils remain poorly understood due to the scarcity of soil-derived genomes. Here, we conduct a size-fractioned (< 0.22 μm) metagenomic analysis across a 130-year chronosequence of a glacier foreland in the Tibetan Plateau and discovered 412 novel viral operational taxonomic units (vOTUs) of huge phages. The phylogenomic and gene-shared network analysis gained insights into their unique evolutionary history compared with smaller phages. Their communities in glacier foreland revealed a distinct pattern between the early (≤ 41 years) and late stages (> 41 years) based on the macrodiveristy (interspecies diversity) analysis. A significant increase in the diversity of huge phages communities following glacier retreat were observed according to current database. The phages distributed across sites within late stage demonstrated a remarkable higher microdiversity (intraspecies diversity) compared to other geographic range such as the intra early stage, suggesting that glacial retreat is key drivers of the huge phage speciation. Alongside the shift in huge phage communities, we also noted an evolutionary and functional transition between the early and late stages. The identification of abundant CRISPR-Cas12 and type IV restriction-modification (RM) systems in huge phages indicates their complex mechanisms for adaptive immunity. Overall, this study unravels the importance of climate change in shaping the composition, evolution, and function of soil huge phage communities, and such further understanding of soil huge phages is vital for broader inclusion in soil ecosystem models.

Soil aggregate stability is profoundly influenced by elevated atmospheric nitrogen (N) deposition, although the mechanisms remain elusive. Here we evaluate the role of microbial-derived soil organic carbon (SOC) of different origins in mediating soil aggregate stability under N addition. We conducted an N addition experiment with three-level (0, 8, and 40 kg N ha−1 yr−1) in a subalpine forest to study the alteration of soil aggregate stability using mean weight diameter (MWD) and geometric mean diameter (GMD) as proxies. SOC content of aggregates, glomalin-related soil proteins (GRSP) and amino sugars were measured to indicate SOC associated with aggregates, derived from arbuscular mycorrhizal fungal hyphae and microbial necromass, respectively. The relative importance of these factors in regulating aggregate stability were explored using multivariate analysis. Nitrogen addition tended to enhance the stability of soil aggregates. In the top 5 cm soil, the N addition level of 40 kg N ha−1 yr−1 significantly (p < 0.05) increased MWD and GMD by 99

How co-existing species of canopy trees and understory shrubs differentially respond to global warming may affect treeline ecotone dynamics, yet their growth trends and potential underlying ecophysiological mechanisms remain understudied. Here, we used dendrochronology and stable carbon isotope analysis to compare the stem radial growth, intrinsic water-use efficiency (iWUE) and climate sensitivity of co-occurring coniferous trees (Abies fabri Craib) and broadleaved shrubs (Rhododendron faberi subsp. prattiiradial) at a treeline ecotone site in the southeast Tibetan Plateau. The results revealed that the shrub's growth rate has increased significantly over the past 50 years (1973-2022) (P < 0.05), while the growth trend of co-existing trees did not increase significantly. Furthermore, compared with nearby trees, the radial growth of shrubs was more strongly positive correlated with temperature and moisture conditions during the growing season (May-October). Nonetheless, during the more recent 1990-2022 period, iWUE of both woody plant species steadily increased with a rising atmospheric CO2 concentration. Overall, our results suggest that at the treeline ecotone, morphological growth and functional trait differences between coniferous trees and broadleaved shrubs, as well as interactions within and between species, may drive divergent plant physiological processes and ecological strategies in response to rapid global warming.

Soil extracellular enzymes play a central role in regulating soil organic carbon (SOC) dynamics. However, the effects of varying warming magnitudes and duration on permafrost soil carbon-degrading enzyme activities remain poorly understood. Here, we investigated warming effects on three representative carbon-degrading enzymes (β-1,4-glucosidase (BG), peroxidase (PER), phenol oxidase (POX)) in alpine and swamp meadows on the Qinghai-Tibet Plateau. The warming experiments were conducted using Open-top chambers at different warming magnitudes (+2.4 and +4.9 °C) and duration (3 and 6 years) in both meadows. The activity of BG increased with warming duration in alpine meadows regardless of the warming magnitude (69

Abrupt shifts in vegetation biomass are increasingly widespread in a warmer and drier world. Understanding the underlying mechanisms is essential for adapting to these changes. However, the mechanisms underlying abrupt changes in vegetation biomass remain highly uncertain, primarily due to a lack of experimental analyses addressing the interactions among limiting environmental factors, plant traits, and biomass dynamics. In this study, we examined a suite of ecosystem attributes to investigate abrupt shifts in vegetation biomass along an aridity gradient. We observed sudden transitions in key plant traits-specifically leaf area and plant height-coinciding with abrupt changes in vegetation biomass and species richness. Moreover, the relationship between relative soil phosphorus (P) content and plant biomass shifted from positive to negative as aridity increased, with a critical threshold identified at an aridity index of 1-AI similar to 0.76. Soil water content also played a pivotal role, inducing a sharp decline in aboveground biomass allocation along the aridity gradient. Network analyses of ecological interactions further revealed that ecosystem components became more tightly coupled-and the consequences of disturbance more pronounced-once the aridity threshold was crossed. These findings advance our understanding of the mechanisms driving abrupt ecological shifts in dryland ecosystems, providing essential insights for forecasting and adapting to such changes under global climate warming.

Alpine lakes on the Qinghai-Tibet Plateau (QTP) are rapidly expanding under climate change, yet their role in the regional carbon budget remains unclear. Here we analyze carbon flux data from 156 alpine lakes of varying sizes and find that these lakes acted as a net carbon sink of 6.7 Tg C yr−1 during 2011–2022, approximately one-fifth of the terrestrial carbon sink over the QTP. This sink is dominated by alpine large alkaline lakes that sequester substantial carbon dioxide far outweighs carbon emissions from smaller lakes. Projected lake expansion under Shared Socioeconomic Pathway (SSP) scenarios indicates an increase in the lake carbon sink by 2100, with the magnitude of this increase varying inversely with scenario level due to the effect of rising water temperatures. When combined with reduced terrestrial carbon sequestration by inundated grasslands, the overall impact of lake expansion on regional carbon budgets depends on future warming rates. Our results highlight alpine lakes act as an important carbon sink and stress the need to account for carbon uptake by large alkaline lakes in regional carbon budget assessments. Carbon flux data from 156 Qinghai-Tibet Plateau lakes reveal a net sink of around 7 Tg carbon per year during 2011–2022, about one-fifth of the regional terrestrial carbon sink, with projections indicating future changes under lake expansion and warming.

Large amounts of dissolved organic carbon (DOC) are transported laterally from uplands and wetlands to headwater streams; however, the global magnitude of this flux and its role in the carbon (C) budget remain unclear. By compiling 20,403 DOC concentration observations and applying machine learning models, we estimated the annual DOC flux from forested headwater streams north of 30°S to be 116.2 Tg C yr −1 (90% CI: 86.5–145.2). Higher yields were observed in tropical regions (3.8 g C m −2 yr −1 ), where vegetation productivity is high, and in boreal regions (3.1 g C m −2 yr −1 ), where peatland cover and soil organic C stocks are substantial. When comparing our results with global terrestrial C flux estimates upscaled from eddy covariance data, we found that the fraction of net ecosystem production (NEP) lost annually as DOC ranged from negligible (<0.1%) to 20.7%, with discharge explaining 34% of the variation. Our study suggests that neglecting the lateral export of DOC could lead to an overestimation of NEP in forested headwater catchments, a bias that is further amplified by increased discharge.

Depolymerization of macromolecular soil organic nitrogen (N) is the first step in converting high-molecular weight organic N (e.g., proteins) into inorganic N, making it a crucial driver of soil N availability and plant productivity. However, the patterns, along with the influencing factors of protein depolymerization in soils across broad geographical expanses have remained unknown. In this study, soil gross protein depolymerization rates (GPDR) across continental scale were analyzed, drawing on 275 observations sourced from 27 published papers. Within the compiled dataset, soil GPDR exhibited a parabolic relationship with latitude (ranging from 30 degrees N to 70 degrees N), while showing a positive linear relationship with elevation (ranging from 0 to 2000 m a.s.l.). The grand mean of soil GPDR was 92.6 +/- 11.1 mg N center dot kg- 1 center dot day- 1, with the highest rates observed in grasslands followed by forests, cropland, and other ecosystems. Soil GPDR was significantly associated with multiple factors. These included soil microbial biomass carbon and N, soil total and inorganic N, mean annual precipitation and soil water content. However, no significant associations were found with mean annual temperature or soil texture. Soil microbial biomass was identified as the most important factor regulating soil GPDR, whereas soil total N and climatic factors indirectly influenced soil GPDR likely via their effects on microbial biomass. Moreover, soil GPDR was the most important factor controlling the content of soil NH4+-N, confirming the important role of protein depolymerization in regulating soil N availability. This study provides a comprehensive understanding of controls of soil N depolymerization by combining climatic, edaphic, and soil microbial factors cross continental scale. These findings emphasize the significance of considering the role of microbial biomass in regulating protein depolymerization, which could provide insights to improve global soil N cycling models.

The freeze-thaw cycle mediates permafrost soil hydrothermal status, nitrogen (N) mineralization, and loss. Furthermore, it affects root development and competition among nitrophilic and other species, shaping the pattern of N distribution in alpine ecosystems. However, the specific N dynamics during the growing season and N loss during the non-growing season in response to climate warming under low- and high-moisture conditions are not well documented. Therefore, we added 15N tracers to trace the fate of N in warmed and ambient alpine meadows and alpine swamp meadows in the permafrost region of the Qinghai-Tibet Plateau. During the growing season, warming increased 15N recovery (15Nrec) in shoots of K. humilis, litters, 0-5 and 5-20 cm roots in the alpine meadow by 149.94 % f 52.87 %, 114.58 % f 24.43 %, 61.11 % f 32.27 %, and 97.12 % f 42.92 %, respectively, while increased 15Nrec of litters by 151.55 % f 27.06 % in the alpine swamp meadow. During the non-growing season, warming reduced 15N stored in roots by 486.77 % f 57.90 %, though increased the 15N recovery in 5-20 cm soil depth by 76.68 % f 39.42 % in the alpine meadow, whereas it did not affect N loss during the non-growing season in the alpine swamp meadow. Overall, warming promoted N utilization by increasing the plant N pool during the growing season, and enhanced root N loss and downward migration during the non-growing season due to the freeze-thaw process, which may result in fine root turnover and cell destruction releasing N in the alpine meadow. Conversely, the N dynamics of alpine swamp meadows were less responsive to climate warming.

A substantial body of evidence sustains that biodiversity enhances ecological stability in changing environments, but the underlying mechanisms in intact natural forest ecosystems remain unresolved. Using data from seven permanent plots, we test the influence and driving factors of plant diversity on stability and variability of diameter at breast height (DBH). We show that species richness under different soils and climate variability indirectly increases stability by species asynchrony rather than a direct influence. Beta diversity (plant species composition dissimilarities over time) has a strong positive effect on stability and soils indirectly increase stability by beta diversity. Soils and climate variability cause a larger effect on variation in standard deviation of DBH by species richness, beta diversity and species asynchrony relative to mean DBH. The study provides a new insight into how plant species diversity affects the process of ecosystem stability under various soil conditions and climatic variability.

Climate warming is a pressing global issue with substantial impacts on soil health and function. However, the influence of environmental context on the responses of soil microorganisms to warming remains largely elusive, particularly in alpine ecosystems. This study examined the responses of the soil microbiome to in situ experimental warming across three elevations (3,850 m, 4,100 m, and 4,250 m) in the meadow of Gongga Mountain, eastern Tibetan Plateau. Our findings demonstrate that soil microbial diversity is highly resilient to warming, with significant impacts observed only at specific elevations. Furthermore, the influence of warming on the composition of the soil microbial community is also elevation-dependent, underscoring the importance of local environmental context in shaping microbial evolution in alpine soils under climate warming. Notably, we identified soil moisture at 3,850 m and carbon-to-nitrogen ratio at 4,250 m as indirect predictors regulating the responses of microbial diversity to warming at specific elevations. These findings underscore the paramount importance of considering pre-existing environmental conditions in predicting the response of alpine soil microbiomes to climate warming. Our study provides novel insights into the intricate interactions between climate warming, soil microbiome, and environmental context in alpine ecosystems, illuminating the complex mechanisms governing soil microbial ecology in these fragile and sensitive environments.