Riverine buffer zones are critical terrestrial-aquatic interfaces for regulating hydrochemistry in watershed landscape management. However, the optimal spatial scale for riverine buffer zone management to synergistically enhance water quality and mitigate greenhouse gas (GHG) emissions remains poorly understood. This study identified a potentially optimal management scale for water quality improvement and GHG mitigation in a river system characterized by landscape patterns. By integrating field-measured water quality and GHG (CO2, CH4, N2O) data with a high-resolution (10 m) land use/land cover (LU/LC) dataset developed from Sentinel-2 imagery using machine learning, we assessed landscape pattern effects across three riverine buffer zone types: riparian strips, circular zones, and sub-basins. The results showed that riparian landscape patterns exhibited stronger correlations with water quality and GHG fluxes than circular zones or sub-basins, and the 300 m buffer width was identified as an optimal management scale in the Yongding River Basin. Within the 300 m riparian strip, dissolved organic carbon and total phosphorus concentrations were negatively correlated with riparian forest coverage (p < 0.01), highlighting the role of riparian vegetation in intercepting organic matter and nutrient inputs. Furthermore, CH4 fluxes were strongly related to riparian landscape configuration, with lower edge density (ED) and landscape shape index (LSI), but higher contagion (CONTAG), being associated with reduced CH4 emissions. Riparian forest shading may indirectly affect CO2 and N2O emissions by regulating water temperature, oxygen conditions, and nitrogen dynamics. These findings emphasize that targeted management of riparian landscape patterns could improve water quality and mitigate riverine GHG emissions.

In this brief communication, we examined the effects of 4‐year experimental warming on plant species‐specific root exudation dynamics and their associated rhizosphere microbial communities in a temperate grassland ecosystem in Inner Mongolia, China. Our results revealed that Artemisia scoparia exhibited greater sensitivity in carbon and nitrogen exudation rates compared to Stipa krylovii . Furthermore, we identified species‐specific interactions between root exudates and rhizosphere microbiomes: S. krylovii primarily established stronger associations with fungal communities, whereas A. scoparia showed tighter linkages with bacterial communities. These findings underscore the need for future research to investigate how global warming may differently affect above‐ and belowground processes across plant functional groups in grassland ecosystems, particularly with respect to plant‐microbe‐soil feedback mechanisms. These findings suggest that the rhizosphere of different plants recruits different microbial groups to cope with climate warming. These species‐specific compensatory mechanisms could have important implications for nutrient cycling dynamics and ecosystem stability in grasslands under future climate warming.

Plateau zokors create newly formed mounds that introduce freshly disturbed microsites in alpine meadows, but it remains unclear whether soil, vegetation, and plant community contrasts between mounds and adjacent grassland follow similar patterns across site contexts or vary in size and pattern among sites. Newly formed mounds were marked in 2021 and sampled in 2023, the third growing season after marking, in three alpine meadow sites representing light, moderate, and heavy degradation. Soil properties, plant diversity, vegetation characteristics, biomass, and community composition were compared between mounds and adjacent grassland using mixed-effects models and ordination analyses. Plant community composition was assessed using ordination and PERMANOVA, and indicator species analysis was used to identify species associated with each microhabitat. Mounds differed from adjacent grassland in soil properties, vegetation structure, biomass, and community composition, but the size and pattern of these contrasts varied among sites. Adjacent grassland generally had higher species richness, plant cover, and biomass than mounds, whereas several soil and diversity variables showed site-specific mound–grassland patterns. Community composition differed significantly overall and within sites. Indicator species analysis showed that mound-associated species were fewer and more site-specific than those of adjacent grassland. Newly formed plateau zokor mounds remained distinct from adjacent grassland during the third growing season after marking, but the size and pattern of these contrasts varied among sites. These mounds are best interpreted as context-dependent early-stage microsites rather than as uniformly beneficial or detrimental features for vegetation recovery.

Humic substances, including fulvic acid (FA) and humic acid (HA), are major refractory organic pollutants in landfill leachate. Although their individual effects on anaerobic digestion (AD) are well studied, FA and HA coexist in leachate with concentrations varying by landfill age. Herein, this study systematically investigated the successive changes of FA/HA concentrations across different landfill ages on AD performance and mechanisms. Results showed FA addition alone decreased methane yield by 67.04% with caproic acid reaching 2.43 ± 0.05 g/L. Co-addition of FA and HA further suppressed methane yield to 12.71 ± 3.91 mL/(gCOD·d), while caproic acid peaked at 2.59 ± 0.08 g/L. Microbial analysis revealed that FA enriched chain elongating bacteria of Caproiciproducens (44.41%) and Ethanoligenens (26.12%) with hydrogenotrophic methanogens Methanobacterium (>95%) dominating, while co-addition further enriched lactic acid producing bacteria (Olsenella) with Caproiciproducens and Methanobacterium remained dominant. FA channeled acetyl-CoA toward the fatty acid biosynthesis pathway to promote caproic acid production, while coenzyme M/B synthesis genes for methane production declined. Co-addition inhibited methanogenesis by blocking methane precursor (5-methyl-THMPT) production, as indicated by reduced key gene abundances (e.g., frhA, frhB, frhG). Thermodynamic calculations validated that FA/HA addition triggered H2 accumulation, making chain elongation thermodynamically preferable to butyric acid oxidation and consequently repressing acetic acid formation and methanogenesis. These findings provide mechanistic insights into the metabolism change that caused by microbial metabolites of FA/HA in AD process.

Abiotic clay mineral fixation and release of ammonium (NH₄⁺) is a key process regulating nitrogen (N) retention and supply in Northeast China's black soil region. However, the long-term effects of chemical fertilizer, manure, and nitrification inhibitors on NH₄⁺ fixation capacity, as well as their relationship with organic matter and yield,remain unclear. This study evaluated 42-year fertilization practices (CK, NPK, NPKM1 with low-level manure, NPKM2 with high-level manure) and the nitrification inhibitor DMPP on fixed NH₄⁺ and maximum fixation capacity in thin-layer black soil (0-100 cm). Results showed that fixed NH₄⁺ ranged from 134.9–225.4 mg kg⁻¹ after 42 years. All fertilization treatments increased fixed NH₄⁺ in the 0-20 cm layer, but only NPKM2 increased it in 20-100 cm depth. Fixed NH₄⁺ accounted for 9.9-32.9% of total N across the 100 cm profile. Maximum fixation capacity (511.0-810.4 mg kg⁻¹) was much higher than actual fixed NH₄⁺, indicating high fixation potential. Manure application (NPKM1 and NPKM2) significantly increased soil organic matter (SOM) in 0-20 cm and promoted maize yield. However, although NPKM2 had higher SOM than NPKM1, yields did not differ between the two treatments. DMPP increased fixed NH₄⁺ by 6.6-15.5% in the early stage (3-7 days) and consistently enhanced fertilizer-derived fixed NH₄⁺, though this effect was weaker under NPKM treatments. In conclusion, integrated fertilizer-manure application (especially with nitrification inhibitors) can increase the fixed NH₄⁺ pool, thereby enhancing N retention and supply, SOM, and crop yield in Northeast China's thin-layer black soil.

Abstract Urbanization and river damming represent profound anthropogenic disturbances that alter hydrological processes and watershed characteristics, thereby influencing riverine methane (CH 4 ) emissions. However, the mechanisms of how these activities drive CH 4 emissions within the watershed scale remain inadequately understood, especially in densely populated regions. To address this, here we measured CH 4 emissions along a 747 km transect in a populated northern China river during late summer. Our results show that CH 4 emissions were 70%–110% higher in reservoir‐affected and lower reaches than in the upper reaches (3.30 and 2.64 vs. 1.58 mmol m −2 d −1 , p < 0.01). CH 4 emission hotspots were closely associated with fine sediments, which were most pronounced in urbanized and impounded reaches. Reduced flow velocity and increased water residence time in these reaches promoted fine sediments and nutrients accumulation, which enhanced organic substrate availability, created anoxic conditions, and reshaped methanogenic communities. Furthermore, urbanization and damming markedly altered carbon metabolic pathways, as evidenced by the increase in the CH 4 : CO 2 ratio from 0.03 in the upperstream to 0.08 in urbanized‐reaches and to 0.16 in reservoir‐affected reaches, along with a higher pmoA / mcrA gene ratio in the upper reaches. Oxygen‐depleted conditions and elevated organic inputs from sewage created a favorable environment for methanogens' growth and activity, ultimately contributing to more CH 4 emissions in urbanized reaches. These findings highlight the critical role of human activities in controlling riverine CH 4 emissions and shifting CH 4 : CO 2 ratios along anthropogenic gradients by changing sediment and hydrological regimes as well as methanogenic communities.

Tungsten is an emerging pollutant commonly assumed to occur as the simple oxyanion tungstate, yet it often condenses into a suite of polytungstates in polluted waters. Despite growing recognition that tungstate polymerization modulates tungsten's environmental fate, its effects on toxicity remain largely unexplored. Here, we tracked the (de)polymerization behavior of three representative (poly)tungstates and examined its associations with multiple measures of acute toxicity to Daphnia magna, including the median lethal concentration (LC50), toxicokinetics, reactive oxygen species (ROS) content, metabolomics, and histology. While tungstate remained stable, W12 metatungstate and phosphotungstate depolymerized to different extents, yielding three distinct polymerization regimes in the exposure media. Monomeric tungstate exhibited high LC50, rapid uptake and efficient excretion, weak ROS signals, and minimal disruption of intestinal integrity. Oligomeric tungstates displayed lower LC50 than tungstate, consistent with slow depuration that generated high internal burdens, ROS accumulation, and suppression-oriented metabolic responses. High-order polytungstates, despite limited uptake and low ROS levels, were associated with structural disruption including irreversible gut barrier damage and mitochondrial collapse and displayed the lowest LC50. Together, these results suggest that tungstate polymerization not only amplifies tungsten toxicity but also alters its mode of action, supporting mechanistic interpretation and prediction of its ecotoxicological dynamics.

Tungsten is an emerging pollutant commonly assumed to occur as the simple oxyanion tungstate, yet it often condenses into a suite of polytungstates in polluted waters. Despite growing recognition that tungstate polymerization modulates tungsten's environmental fate, its effects on toxicity remain largely unexplored. Here, we tracked the (de)polymerization behavior of three representative (poly)tungstates and examined its associations with multiple measures of acute toxicity to Daphnia magna, including the median lethal concentration (LC50), toxicokinetics, reactive oxygen species (ROS) content, metabolomics, and histology. While tungstate remained stable, W12 metatungstate and phosphotungstate depolymerized to different extents, yielding three distinct polymerization regimes in the exposure media. Monomeric tungstate exhibited high LC50, rapid uptake and efficient excretion, weak ROS signals, and minimal disruption of intestinal integrity. Oligomeric tungstates displayed lower LC50 than tungstate, consistent with slow depuration that generated high internal burdens, ROS accumulation, and suppression-oriented metabolic responses. High-order polytungstates, despite limited uptake and low ROS levels, were associated with structural disruption including irreversible gut barrier damage and mitochondrial collapse and displayed the lowest LC50. Together, these results suggest that tungstate polymerization not only amplifies tungsten toxicity but also alters its mode of action, supporting mechanistic interpretation and prediction of its ecotoxicological dynamics.

Global warming affects both plant growth and soil microbial decomposition, creating uncertainty for the storage and persistence of soil organic carbon (SOC) stock. Limited decomposition rates often characterise cold alpine ecosystems. Yet, warming may increase their microbial activity, affecting SOC sequestration. Here, we present findings from a 14-year field warming study carried out in an alpine meadow on the Qinghai-Tibetan Plateau. Warming significantly increased mineral-associated organic carbon (MAOC) by 11% in topsoil and 6% in subsoil-primarily through an increase in iron/aluminium-bound organic carbon (Fe/Al-OC) in topsoil and calcium-bound organic carbon (Ca-OC) in subsoil. On the contrary, warming did not affect particulate organic carbon (POC). MAOC content was strongly positively correlated with soil fungal biomass and fungal necromass carbon, highlighting the role of fungal-derived carbon inputs. Our results reveal distinctly different responses of SOC pools to long-term warming and underscore the importance of organo-mineral interactions in shaping SOC dynamics in cold ecosystems under climate change.Read the free for this article on the Journal blog.

Microplastics (MPs) are ubiquitous in freshwater environments owing to their widespread use and persistence. Understanding the factors governing the vertical sedimentation of MPs is crucial for assessing their ecological risk and developing effective pollution control strategies. This review systematically examines the intrinsic particle characteristics, environmental drivers, and biological mediators that influence the settling behavior of MPs in freshwater systems. The density, shape, and size of MPs are critical determinants of their buoyancy, hydrodynamic properties, and aggregation potential. Environmental conditions, including hydrodynamics, water physicochemical properties, and surrounding media, regulate MP transport and deposition through complex interactions. Biological processes such as biofouling, ingestion and egestion by aquatic organisms, and bioturbation further modify the vertical distribution of MPs. Microbial colonization and extracellular polymeric substance (EPS) production alter MP density and surface properties, facilitating aggregation and sedimentation. Aquatic plants, zooplankton, and fish influence MP redistribution via interception, uptake, and excretion. Benthic macroinvertebrate bioturbation affects MP burial and resuspension at the sediment-water interface. Despite recent progress, knowledge gaps persist in understanding the synergistic effects of multiple factors under realistic environmental conditions. Future research should focus on developing integrated aggregation models that incorporate biofilm growth, environmental factors, and hydrodynamics, as well as creating high-precision vertical-flux models. Addressing these challenges will enhance the accuracy of MP fate predictions and inform targeted risk assessments and pollution control strategies for freshwater ecosystems.

Agricultural soils are major sources of reactive nitrogen (N) gases, yet distinguishing fertilizer-derived emissions from those originating in the soil remains a key challenge for accurate N management. We conducted an in situ 15N tracing experiment in a maize field in Northeast China using 15N-labeled urea (49.7 % 15N, 200 kg N ha-1), integrating passive adsorption and static chamber techniques to quantify source-specific emissions of ammonia (NH3), nitric oxide (NO), and nitrous oxide (N2O). The results revealed distinct timing in the peak emissions of these N gases. NH3 emission peaked first (6.4 kg N ha-1 cumulative loss) and was mainly driven by soil ammonium levels whereas subsequent NO (3.8 kg N ha-1) and N2O (1.4 kg N ha-1) peaks were primarily regulated by temperature and soil nitrate availability. The synchronous bimodal 15N dynamics of NO and N2O indicated coupled nitrification-denitrification processes, with higher 15N enrichment in NO (mean 20 %) than in N2O (11 %), suggesting stronger nitrification control on NO production. Fertilizer-derived N accounted for 67 %, 52 %, and 30 % of total NH3, NO, and N2O emissions, respectively. However, fertilizer-induced soil N transformations via priming and legacy effects led to underestimation of the total influence of fertilizer in 15N tracing. These findings challenge conventional emission factor models, which may overlook indirect N emissions from agricultural inputs, and highlight the need to incorporate soil N priming and legacy dynamics into agricultural N footprint assessments.

Urbanization and river damming represent profound anthropogenic disturbances that alter hydrological processes and watershed characteristics, thereby influencing riverine methane (CH4) emissions. However, the mechanisms of how these activities drive CH4 emissions within the watershed scale remain inadequately understood, especially in densely populated regions. To address this, here we measured CH4 emissions along a 747 km transect in a populated northern China river during late summer. Our results show that CH4 emissions were 70%-110% higher in reservoir-affected and lower reaches than in the upper reaches (3.30 and 2.64 vs. 1.58 mmol m(-2) d(-1), p < 0.01). CH4 emission hotspots were closely associated with fine sediments, which were most pronounced in urbanized and impounded reaches. Reduced flow velocity and increased water residence time in these reaches promoted fine sediments and nutrients accumulation, which enhanced organic substrate availability, created anoxic conditions, and reshaped methanogenic communities. Furthermore, urbanization and damming markedly altered carbon metabolic pathways, as evidenced by the increase in the CH4: CO2 ratio from 0.03 in the upperstream to 0.08 in urbanized-reaches and to 0.16 in reservoir-affected reaches, along with a higher pmoA/mcrA gene ratio in the upper reaches. Oxygen-depleted conditions and elevated organic inputs from sewage created a favorable environment for methanogens' growth and activity, ultimately contributing to more CH4 emissions in urbanized reaches. These findings highlight the critical role of human activities in controlling riverine CH4 emissions and shifting CH4: CO2 ratios along anthropogenic gradients by changing sediment and hydrological regimes as well as methanogenic communities.

Returning organic amendments to saline-alkali soils constitutes a key strategy for soil amelioration, as it enhances crop productivity by modulating the rhizosphere microenvironment. In this study, straw, biochar, and peat were selected as representative organic amendments, and a two-year field experiment-employing a rotational cropping system of Sesbania and Triticale-was conducted to investigate their differential regulatory effects on rhizosphere properties and root development. Results demonstrated that all three amendments induced coordinated shifts in the rhizosphere "extract-microbiota-enzymes-nutrients" nexus, concomitant with significant stimulation of root growth. The hypothesized pathways through which different organic amendments improve the rhizosphere environment vary mechanistically: straw application appears to enhance alkaline phosphatase activity and enrich phosphorus-solubilizing microorganisms; it is hypothesized that this promotes root growth by facilitating the mineralization of organic phosphorus. In contrast, peat amendment induces the most pronounced increases in esterase content and sucrase activity, and its growth-promoting effect is likely attributable to accelerated carbon and phosphorus cycling. Biochar, meanwhile, is associated with elevated catalase activity, improved potassium retention, and enhanced organic carbon sequestration; its beneficial function is postulated to stem from mitigation of oxidative stress. Collectively, this study provides initial evidence that distinct organic amendments modulate rhizosphere processes via divergent biochemical and microbial mechanisms-offering a theoretical foundation for their rational selection and application in saline-alkali soil remediation.

The substitution of mineral fertilizer with organic fertilizer can help improve soil fertility and reduce environmental emissions, but the extent to which organic fertilizer should replace chemical nitrogen (N) fertilizer with respect to phosphorus (P) risk management remains unclear. In this study, we aimed to investigate the effects of organic fertilizer substitution on soil P and crop yield through a five-year field experiment. Four treatments were arranged, including chemical fertilizer N but no P (C1), chemical fertilizer (C2), 25 % organic fertilizer substitution based on N addition (M1), 50 % organic fertilizer substitution (M2) and 100 % organic fertilizer substitution (M3). The results indicated that the overall yield of the three organic fertilizer substitution treatments was lower than that of the C2 treatment, but only M3 and C2 showed significant differences. Compared with the C1 treatment, the C2, M1, and M2 treatments did not increase TP, Olsen-P or labile-P, while their contents were high in the upper soil of M3. Path analysis between different P fractions and Olsen-P revealed that resin-P, NaHCO3-Pi, and NaOH-Pi had the greatest direct effect on Olsen-P, but NaHCO3-Po and NaOH-Po might transform into OlsenP through NaHCO3-Pi and NaOH-Pi. Our results suggested that partial substitution of chemical fertilizers not only ensured yield but also did not increase the risk of P leaching, making it more feasible than full substitution with organic fertilizers. The substitution of organic fertilizer would lead to more conversion of organic P into inorganic P to maintain the soil Olsen-P level. These results contribute to a better understanding of the influence of the substitution of organic fertilizer on the P pool and thus clarify the appropriate proportion of substitution.

Trichoderma has proved to enhance plant growth under saline stress. However, there is limited research on Trichoderma-induced alterations of rhizosphere microbial communities in woody plants, and the subsequent effect on their yield is poorly understood. This study was to investigate the growth-promoting mechanism of Trichoderma asperellum on wolfberry (Lycium chinense) in coastal saline land from bacterial community and diversity aspects through a field trial with Trichoderma agent application. Trichoderma agent application significantly increased fruit yield, plant dry weight and nitrogen accumulation, demonstrating that Trichoderma enhanced salt tolerance of wolfberry. Despite no obvious influence on the structure of bacterial community, Trichoderma agent application significantly increased rhizosphere soil bacterial diversity, with beneficial bacterial genera including Shinella and Flaviaesturariibacter showing increased relative abundances. In addition, Trichoderma agent application enhanced the stability of soil bacterial co-occurrence network, as evidenced by higher counts of nodes and edges in the network. Furthermore, Trichoderma agent application reduced the abundance of the complete nitrifier Candidatus Nitrospira nitrificans, inhibited soil nitrification and significantly increased soil ammonium nitrogen content, contributing to the improvement of plant nitrogen nutrition. According to random forest analysis, the most significant predictive importance for wolfberry yield was Shannon index, followed by the relative abundances of beneficial bacteria and soil nitrate nitrogen content, highlighting that the growth-promoting role of Trichoderma could be realized by elevating rhizosphere soil bacterial diversity. Moreover, SEM indicates that in contrast to the pathway of nitrogen accumulation, the increased yield was primarily achieved by enhancing rhizosphere soil bacterial diversity with Trichoderma agent application. Therefore, Trichoderma promotes wolfberry growth and yield in saline land mainly by elevating rhizosphere bacterial diversity, with improved nitrogen nutrition providing an additional contribution. This study deepens our understanding of the mechanisms by which Trichoderma promotes plant growth, and provides a promising biostimulant for wolfberry cultivation in saline land.

The chemical forms of nitrogen (N) are crucial to soil biogeochemical processes, with soil aggregates serving as the primary reservoirs for these N forms. However, the response of these N forms to different application rates remains inadequately understood in current N management strategies. A seven-year field experiment was conducted on reclaimed soil to evaluate effects on N forms in soil aggregates after application of four N rates (0 [CK], 100, 150, and 200 kg N ha(-1)) under two fertilization regimes: inorganic N fertilizer alone and a combined organic-inorganic fertilizer application (1:1 ratio). The results showed that combined fertilization significantly improved soil nutrient content, microbial biomass, and aggregate stability compared to single fertilizer treatments. At 200 kg N ha(-1), combined fertilization increased transformable N (TF-N) by 99.80 - 201.35% across all aggregate sizes, surpassing the 61.47 - 170.14% increase observed under equivalent sole fertilization treatments. Organic matter-sulfide-bound N (OSF-N) and ion-exchangeable N (IEF-N) were the dominant TF-N fractions, accounting for 62.47 - 70.85% and 10.23 - 20.28%, respectively. These forms exhibited distinct size-dependent distributions: OSF-N, IEF-N, and carbonate-bound N (CF-N) were mainly concentrated in aggregates < 0.25 mm, while iron-manganese-oxide-bound N (IMOF-N) was more abundant in aggregates > 0.25 mm. In addition, sole fertilization lowered soil pH (P < 0.01), suppressing enzymatic activity (P < 0.05) and indirectly limiting TF-N transformation. In contrast,combined fertilization directly enhanced TF-N transformation by improving nutrient availability and microbial biomass. This study highlights the effectiveness of organic-inorganic N application in enhancing N transformation in reclaimed soils, promoting agricultural waste recycling, and offering new insights into soil N cycling.

Soil organic matter (SOM) is crucial for the productivity of greenhouse soils, yet its chemical composition over time has not been well explored, particularly under high-intensity tillage practices. This study analyzed the dynamic changes in the chemical composition of SOM based on 78 soil samples collected across different cropping years in Eastern China. The study site features a typical temperate continental monsoon climate, and the surveyed greenhouse and farmland soils are all cinnamon soils. Soils were categorized into four groups based on land use and cropping years. Fourier transform infrared (FTIR) spectroscopy was used to assess the chemical composition of SOM. High-intensity greenhouse cultivation induces significant and non-linear alterations in SOM chemical composition. The specific manifestations are the selective consumption of labile functional groups and the gradual intensification of SOM aromatization. Compared to field soils, polysaccharide-C decreased by 5.47