Agriculture is expected to play a significant role in supporting carbon (C) sequestration globally. Microbial carbon use efficiency (growth yield, Y-strategy) and enzyme production (resource acquisition, A-strategy) are fundamental life history traits that affect soil C balance. Yet, uncertainties persist concerning microbial adaptations to long-term fertilization and the ensuing regulation of C cycling. Here, we investigated the trade-offs between Y-strategy and A-strategy, as well as their impacts on C accumulation in red soils (C-poor) and yellow soils (C-rich) subjected to 30 years of chemical and organic fertilization. We found that long-term fertilization exerts context-dependent effects on microbial Y-strategy (growth yield) and A-strategy (resource acquisition): in red soils, microbial Y- and A-strategies exhibit a significant trade-off—microbial Y-strategy is enhanced whereas A-strategy is reduced, jointly regulating C accumulation. Conversely, in yellow soils, a synergistic trend emerges only under mineral (NPK) and organic (NPKM) fertilization, with Y-strategy alone driving C accumulation. Further analysis revealed that soil stoichiometry and microbial traits strongly account for strategy variations by driving C-stable genes across soils: in red soils, higher C:P and N:P ratios (reflecting nutrient availability) favor dominance of k-strategist Acidobacteria, strengthening microbial A-strategy by upregulating C-stable genes related to resource acquisition, which creates a marked trade-off with the Proteobacteria-dominated Y-strategy. In yellow soils, however, altered nutrient availability weakens such functional differentiation among microbial groups, dissipating the Y-A trade-off. Notably, specific fertilization (e.g., N, NPK, NPKM) drives a synergistic trend via sufficient nutrient supply. Overall, our findings suggest that trade-offs between microbial growth yield and resource acquisition govern soil organic carbon (SOC) after long-term fertilization, revising the previous assumption that a high CUE promotes microbial biomass, enzyme production, and organic matter decomposition.

Soil microbially derived carbon is essential for soil carbon sequestration, yet its dynamics under organic matter addition in croplands remain poorly understood, largely owing to the interactions among microbial carbon, nitrogen, and phosphorus metabolic functions and their divergent responses to soil environmental changes. Here, based on a long-term field experiment, we investigated the effects of combined application of chemical fertilizer with straw or manure on microbially derived carbon accumulation in soils. The 18O-H2O tracer method and soil extracellular enzyme were used to quantify microbial carbon use efficiency and carbon acquisition capacity, and metagenomic sequencing was performed to determine microbial carbon, nitrogen and phosphorus functional genes, aiming to unravel the intrinsic relationship between microbial metabolism and microbially derived carbon. The results showed that, compared to the chemical fertilizer treatment, the chemical fertilizer treatments with straw or manure both significantly increased the accumulation of microbially derived carbon. Furthermore, the microbially derived carbon was significantly positively correlated with microbial carbon use efficiency but negatively correlated with carbon acquisition capacity. Specifically, chemical fertilizer treatments with straw or manure increased microbial carbon use efficiency but reduced carbon acquisition capacity, thereby shifting the microbial metabolic pattern from a "high decomposition" state to a "high utilization" state, which associated with the retention of microbially derived carbon. Correlation analysis showed that microbial carbon use efficiency was significantly positively correlated with nitrate nitrogen, SOC but negatively with microbial carbon and nitrogen functional genes (e.g., those involved in disaccharide metabolism, dissimilatory nitrate reduction, and nitrogen fixation), whereas carbon acquisition capacity exhibited the opposite pattern. Especially, the increased nitrate nitrogen and SOC under chemical fertilizer with straw or manure effectively alleviated microbial resource limitation and were negatively correlated with both nitrogen and carbon functional genes. These findings elucidate the role of nitrogen and carbon availability in regulating the relationships among microbial metabolic functions, carbon acquisition and utilization, improving our understanding of the mechanisms governing microbial-derived carbon accumulation under organic matter addition.

The synergistic optimisation of agricultural productivity enhancement and N2O emission reduction presents a core challenge in global agricultural sustainability. Integrating 792 field trials (6,678 observations) with meta-analysis and machine learning, this study evaluates nine management practices for their impacts on N2O emissions, crop yields, and yield-scaled N2O emission. Compared to standard synthetic fertilization (SY), biochar (BI), organic fertilizer substitution (OF_SY), and enhanced-efficiency nitrogen fertilizer (EENF) exhibit synergistic effects: reducing N2O emissions (15.6-32.2%), increasing yields (4.6-7.6%), and decreasing yield-scaled N2O emission (23.7-35.2%). In contrast, SY, organic fertilizers, or their combination led to a "high yield-high emission" outcome, elevating yield-scaled N2O emissions (15.7-70.5%). Global spatial projections demonstrate that optimal implementation of OF_SY (-27.6%), EENF (-45.7%), straw return (SR,-8.1%), BI (-23.9%), and reduced/no-tillage (RNT,-16.8%) concurrently enhance yields, with coordinated global deployment further reducing yield-scaled N2O emission by 46.7%. Overall, we establish a framework guiding agricultural practices to mitigate climate change.

The Loess Sandy Region, a fragile ecosystem facing severe soil degradation, requires sustainable strategies to enhance soil organic carbon (SOC) and restore ecological functions. Through a long-term split-plot experiment, we evaluated straw mulching (applied (S) or not (S0)) with nitrogen fertilizer types (none (W), conventional urea (U), slow-release urea (RU)) during critical phenological periods of soybean growth. The results indicated that SU and SRU treatments significantly increased average yields by 209.03% and 356.32%, respectively, compared to S0W. Regarding carbon pools, compared to S0W, S0U and S0RU treatments reduced SOC content by 6.31% and 5.33%, respectively. The SW and SRU treatments significantly increased SOC content by 33.53% and 45.17%, respectively, and also significantly raised mineral-associated organic carbon (MAOC) content by 35.37% and 26.20%. Furthermore, SW, SU, and SRU treatments reduced the rate of organic carbon mineralization. Enzyme stoichiometric modeling revealed that SU and SRU effectively alleviated microbial nitrogen limitation. The S0U and S0RU treatments significantly reduced bacterial Chao1 and Shannon at the pod stage (R4). By the maturity stage (R8), SU and SRU treatments increased the Shannon index. Co-occurrence network analysis demonstrated that SRU treatment significantly enhanced bacterial network complexity and exhibited the lowest average variation degree. Although favorable hydrothermal conditions stimulate microbial activity and accelerate the mineralization of native organic matter in the short term, in the long run, the efficient utilization of straw-derived carbon by microorganisms, particularly the significant increase in MAOC, drives the overall increase in SOC. Overall, this study provides important theoretical support for advancing the sustainable restoration of degraded ecosystems in the Loess Region.

Global cropland soils possess significant carbon storage potential, yet their storage efficiency is directly regulated by fertilization practices. To elucidate the impact of fertilization on soil organic carbon (SOC) in major cropland systems (paddy/upland), this study leverages a 37-year long-term field experiment. We integrate physical fractionation (particulate organic carbon (POC), mineral-associated organic carbon (MAOC)) and biomarker techniques (plant-derived carbon, microbial necromass carbon) to systematically analyze carbon pool reconfiguration pathways under four fertilization treatments: no fertilizer (CK), nitrogen-only fertilizer (N), NPK fertilizers (NPK), and combined organic-inorganic fertilization (NPKM). Key findings are as follows: NPKM significantly increased SOC by 52.6% in upland and 29.4% in paddy. In contrast, chemical-only fertilization (N/NPK) achieved no increase in carbon storage, confirming the essential role of organic carbon inputs in cropland carbon storage. In paddy soils, flooded conditions suppressed microbial decomposition and saturated the MAOC pool, leading NPKM treatment to drive preferential carbon enrichment into the POC fraction. Conversely, NPKM treatment in upland soils concurrently enhanced both POC and MAOC pools, demonstrating a synergistic dual-pool accumulation mode. NPKM induced substantial increases in plant-derived carbon (lignin phenol biomarkers) in upland (458.9%) and paddy soils (188.1%). This contributed 63.5% and 65.7% of SOC under NPKM in upland and paddy soils, respectively, highlighting its dominant contribution to SOC accumulation. NPKM treatment also increased microbial necromass carbon but shifted its composition toward fungal necromass dominance in upland soils and bacterial necromass dominance in paddy soils. In conclusion, NPKM exhibits prominent carbon storage potential in both upland and paddy systems. However, distinct carbon storage patterns emerge due to differences in water management. This necessitates targeted carbon storage strategies specifically designed for the distinctive characteristics of paddy and upland systems.

Soil salinization is one of the most severe forms of land degradation in arid and semi-arid regions, posing substantial threats to agroecosystem stability and food security. In this study, saline-alkali soil collected from the Wuding River Basin in Yulin, Shaanxi Province was used to construct a three-factor amendment system comprising superabsorbent polymers (SAP), biochar, and humic acid. A systematic assessment was conducted to elucidate their combined effects on soil water-salt transport and crop growth. Results from one-dimensional constant-head infiltration experiments using indoor soil columns demonstrated that the application of amendments significantly increased cumulative infiltration and improved the uniformity of wetting-front advancement. Specifically, the treatments regulated the redistribution of salts within the soil profile; while surface salinity reduction varied, the leaching efficiency was significantly enhanced in the A2B2C2 treatment. Soil bulk density (BD) showed dynamic fluctuations during the growth cycle, peaking at 1.628 cm-3 during the branching stage, while high-rate biochar (A3) reduced BD by up to 13.64% compared to the control by the initial flowering stage. Fitting results based on the Philip and Kostiakov models further indicated that the combined amendment strategy-particularly the A2B2C2 treatment (30 kg/ha SAP, 15,000 kg/ha biochar, and 600 kg/ha humic acid)-markedly enhanced both the initial infiltration rate and the steady infiltration capacity. Field experiments corroborated the indoor findings: plant height and dry biomass of Melilotus officinalis (L.)Lam. were significantly higher under amendment treatments than in the control, driven by improved water availability, mitigated salt stress, and enhanced soil structure. Single-factor and multi-factor interaction analyses revealed that SAP exerted pronounced effects during early growth stages, whereas biochar and humic acid contributed more substantially during the middle to late stages through sustained regulatory functions. Collectively, the results demonstrate that the combined application of SAP, biochar, and humic acid improves the water-salt regime of saline-alkali soils through a coupled "water-salt-structure-plant" mechanism, ultimately enhancing crop productivity. This study provides both theoretical insights and practical guidance for the amelioration of saline-alkali soils.

Sloping cropland on the Loess Plateau faces severe challenges from soil organic carbon (SOC) depletion and structural instability due to erosion and intensive tillage. Although mulching can enhance SOC sequestration, its long-term effects on the spatial distribution of SOC and aggregates across slopes remain unclear. A 15-year field experiment evaluated five practices—conventional tillage (T), no tillage (NT), straw mulching (SM), plastic film mulching (PM), and ridge–furrow plastic film mulching (RPM)—on SOC storage, aggregate stability, and their variation with different slope positions. Compared to T, all mulching treatments significantly increased SOC concentration by 4.19% to 83.48% in the 0–30 cm layer. SM and RPM notably increased macro-aggregates (>2 mm) and their associated SOC (24.04–56.49% higher than T) by adding organic matter and optimizing micro-topography. Different slope positions strongly influenced SOC redistribution: lower slopes accumulated more SOC than upper slopes due to erosion–deposition processes. Mulching reduced SOC spatial variability and minimized differences between slope positions. Although mulching increased cumulative SOC mineralization compared to T, the long-term net SOC gain was positive, driven by improved aggregate protection and reduced erosion. SM and RPM are recommended for sustainable slope farmland management due to their dual benefits in enhancing carbon sinks and soil stability. This study offers practical strategies for improving soil health and SOC sequestration in vulnerable sloping landscapes.

Soil carbon sequestration plays a dual role in mitigating climate change and enhancing ecological resilience. Microbial necromass carbon (MNC) constitutes a critical component of soil organic carbon (SOC), yet its vertical distribution under straw mulching with fertilization remain poorly characterized. We conducted a 3 year field experiment on China's Loess Plateau, integrating straw (mulching (S) vs. removal (S0)) with nitrogen fertilizer (no fertilizer (W), conventional urea (U), slow-release urea (RU)). The results indicate that SRU treatment drove surface enrichment of labile carbon fractions, triggering microbial diversity and microbial community assembly processes. Additionally, compared to S0W, the SRU treatment significantly increased topsoil bacterial necromass carbon (BNC) by 22.2%, fungal necromass carbon (FNC) by 33.4%, and MNC by 28.9%. Conversely, the SRU treatment significantly decreased subsoil FNC content by 9.2%. In the 0-10 cm layer, compared to S0W, both straw mulching combined with chemical fertilizer treatments (SU and SRU) significantly reduced the ratios of BNC/SOC, FNC/SOC, and MNC/SOC. Regarding carbon-degrading enzyme activities, at the 0-10 cm depth, the sole fertilization treatments (S0U, S0RU) significantly increased peroxidase (POD) activity, whereas straw mulching combined with fertilization (SU, SRU) had no significant effect in this layer. Meanwhile, compared to S0W, both SU and SRU treatments significantly enhanced β-glucosidase (BG) activity, with increases of 200.5% and 122.2%, respectively. Additionally, relative to S0W, the SRU treatment also significantly increased BG activity in the 10-20 cm and 20-30 cm layers, by 106.4% and 110.5%, respectively. Using partial least squares path modeling and optimal multivariate regression model, this study revealed that FNC exhibited a significantly positive correlation with SOC accumulation in the topsoil. In the subsoil layer, the 9.2% decrease in FNC accumulation may be associated with reduced nitrogen availability and the consequent decline in fungal activity. These findings suggest that straw-fertilizer drives vertical gradient interactions between edaphic biotic and abiotic factors, thereby regulating the spatial heterogeneity of carbon sequestration.

CONTEXT: Climate-related disasters have become institutionalized risks in agricultural systems, with smallholder farmers particularly vulnerable. Conventional explanations focusing solely on "lack of perception" or "lack of resources" fail to fully account for under-adaptation. Emerging evidence suggests that structural misalignment between risk perception and resource capacity-termed "cognitive-resource mismatch"-is a critical constraint. OBJECTIVE: This study investigates how cognitive-resource mismatch suppresses adaptive behavior, identifies "willing but unable" (high perception-low resource) and "able but unwilling" (low perception-high resource) groups, and examines their differentiated effects on disaster recovery and household heterogeneity. METHODS: Using survey data from 3240 households in the Guanzhong Plain, China, we constructed indices of risk perception and resource capacity, and developed a mismatch indicator. Econometric models-including OLS, Ordered Probit, 2SLS with instrumental variables, and Lewbel-IV-were employed, alongside heterogeneity and robustness analyses. RESULTS AND CONCLUSIONS: Both mismatch types significantly reduce adaptive behavior and weaken post-disaster recovery. The effect is strongest among female-headed, resource-poor, and disaster-inexperienced households. Results reveal non-linear complementarity between cognition and resources, showing that adaptation failure arises from systemic misalignment rather than isolated individual deficiencies. SIGNIFICANCE: The study introduces the concept of alignment-sensitive governance, emphasizing differentiated policies to reduce mismatch. Financial and insurance instruments can empower the "willing but unable," while behavioral activation and risk communication can mobilize the "able but unwilling." This framework advances adaptation theory, highlights equity and climate justice dimensions, and provides actionable insights for precision governance in agriculture and beyond.

Arid cities are increasingly exposed to the dual pressures of ecological restoration and socioeconomic development, yet the long-term trajectories and future reorganization mechanisms of ecosystem services (ESs) remain insufficiently understood. Using Northern Shaanxi, a representative arid urban region on the Loess Plateau (NSR), as a case study, we developed an integrated multi-scale analytical framework that combines the PLUS model, InVEST, a composite ecosystem service index (CESI) and self-organizing maps (SOM). This framework was used to assess historical changes in ESs from 1990 to 2020 and their future responses under four policy-oriented scenarios for 2035, identify dominant driving factors, and derive ecological zoning and policy implications at different scales. The results showed that policy orientation strongly reshaped land use and ecosystem services in the NSR. From 1990 to 2020, ecological restoration was associated with a relatively increase in CESI, which became significant under baseline development scenario and ecological priority scenario (S4) by 2035, with the largest gain in soil retention under S4. CESI consistently displayed a south–north gradient that remained stable across future scenarios, indicating a strong restoration legacy and ecological memory rooted in soil and topography. Compared with 2020, CESI in 2035 became more sensitive to human activities, especially under S4, where the explanatory power of population approached 0.8 (p<0.05). These findings show that policy pathways reshape integrated ESs patterns and the composition of ES bundles across scenarios, while highlighting the value of cross-scale zoned governance for balancing restoration and development in arid urban regions.

Glomalin-related soil protein (GRSP), a key glycoprotein metabolite of arbuscular mycorrhizal fungi (AMF), plays a central role in soil carbon and nitrogen sequestration and aggregate stability. However, a systematic understanding of its response patterns and driving mechanisms under diverse global change factors (GCFs) remains limited. This study conducted a global meta-analysis to assess the effects of 14 GCFs (including land-use conversion, fertilization, and climate change) on the two GRSP fractions: easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP). The results demonstrated that T-GRSP exhibited more pronounced responses to GCFs than EE-GRSP, making it a superior indicator for characterizing long-term changes. Specifically, fertilization (nitrogen +28%; phosphorus +12%; nitrogen and phosphorus +44%; nitrogen, phosphorus and potassium +33%) and elevated CO2 (eCO2 +7%) significantly promoted T-GRSP accumulation (all relative to control, p < 0.05). In contrast, land-use conversions such as forest to bare land (-91%), farmland (-33%), shrubland (-36%), and grassland to farmland (-43%) significantly reduced T-GRSP. Warming, fire, and forest-to-grassland conversion showed no significant effects. Soil pH change was identified as the pivotal hub regulating GRSP responses to GCFs, governing GRSP accumulation dynamics by influencing its mineral adsorption and microbial decomposition. Furthermore, changes in T-GRSP were tightly coupled with soil organic carbon (SOC) and total nitrogen (TN), directly contributing to the stable C and N pool and indirectly enhancing physical protection through promoting aggregate formation. Notably, under climate change, the relationship between SOC, TN and T-GRSP showed "decoupling". Concurrently, a significant negative correlation emerged between the proportion of T-GRSP in SOC, TN and their actual contents, revealing an adaptive strategy in which T-GRSP serves as a stable component for "core protection". This study systematically elucidates the response patterns and mechanisms of GRSP to global change, highlighting its dual role in maintaining the stability of soil carbon and nitrogen pools.

Mulching is an important agronomic strategy for improving soil quality and crop productivity in arid and semi-arid agroecosystem. However, its integrated effects on soil health, microbial nutrient limitation, enzyme-mediated processes, and yield stability remain inadequately characterized. A field experiment established in 2008 was evaluated in 2019-2020 to compare straw mulching (SM), plastic-film mulching (PM), ridged plastic-film mulching (RM), and no mulching (CK), on soil quality index (SQI), microbial functionality, and soybean yield. All mulching treatments significantly enhanced soil nutrient availability and microbial biomass compared with CK. Soybean yield increased by 22.50%, 34%, and 49.50% under SM, PM, and RM, respectively, with RM showing the highest yield, stability and sustainability. SQI was elevated by 93.02%, 87.06% and 145.93% under SM, PM, and RM, respectively. Enzyme profiling indicated SM and RM promoted soil biological functioning through increased β-glucosidase activity. Eco-enzymatic vector analysis confirmed the angles below 45°, indicating microbial nitrogen limitation across treatments, while mulching differentially modified nutrient-acquisition strategies. Mantel analysis revealed strong associations among soil nutrients, microbial biomass, vector parameters, SQI, and soybean yield. Partial least square path modelling indicated that soil chemical properties exerted the strong positive effect on yield, followed by SQI. Random forest analysis identified SQI as key predicator of yield response. Overall, RM most effectively enhanced soybean productivity and microbial functionality, while SM maintained yield resilience during 2019-2020, underscoring mulching as a sustainable strategy for improving soil health, and agroecosystem stability in dryland soybean production.

Root exudates play a key role as signals and nutrients in mediating plant-microbe communication. However, critical knowledge gaps remain regarding how root exudates mediate soil-microbe-plant interactions to regulate crop yield under long-term straw mulching combined with fertilization. Therefore, we conducted a 3-year field trial integrating straw management (straw mulch (S) versus removal (S0)) with different nitrogen fertilizer types (no fertilizer (W), conventional nitrogen fertilizer (U), and slow-release nitrogen fertilizer (RU)), employing integrated metabolomic and microbiome analyses to evaluate how root exudates affect microbial communities and may contribute to improved rhizosphere soil nutrients and crop productivity. Using the S0W as a control (yield: 357.6 kg ha-1) to highlight the effects of management practices, the results showed that both the SU and SRU treatments significantly increased crop yields, reaching 1105.1 and 1631.8 kg ha-1, respectively. Compared with S0W, the SU and SRU treatments also significantly enhanced soil organic carbon content by 43.3% and 54.4%, respectively. The SRU treatment demonstrated the most pronounced improvements in total nitrogen and total phosphorus, with increases of 28.9% and 18.5%, respectively. Furthermore, the SRU treatment significantly increased the relative abundance of microorganisms such as Glomeromycota and Cladosporiaceae, as well as key lipid and organic acid metabolites in root exudates. Weighted correlation network analysis and Mantel tests revealed that putatively annotated metabolites were significantly correlated with both soil nutrient content and the enrichment of key microbial taxa (Acidobacteriota and Cladosporiaceae). Subsequent partial least squares path modelling further demonstrated that these interactions were significantly linked to improved soil nutrient status and increased crop yield. In summary, this study provides important insights for ameliorating degraded soils and optimizing extensive management practices.Read the free for this article on the Journal blog. (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)-(sic)(sic)(sic)-(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic) (sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)3(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(S)(sic)(sic)(sic)(sic)(sic)(S0))(sic)(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(W),(sic)(sic)(sic)(sic)(U)(sic)(sic)(sic)(sic)(sic)(RU))(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)S0W(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic):357.6 kg ha-1)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic), SU(sic)SRU(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)1105.1(sic)1631.8 kg ha-1.(sic)S0W(sic)(sic), SU(sic)SRU(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)43.3%(sic)54.4%.SRU(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)28.9%(sic)18.5%.(sic)(sic), SRU(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(Glomeromycota)(sic)(sic)(sic)(sic)(sic)(Cladosporiaceae)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)Mantel(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)((sic)(sic)(sic)(sic)(Acidobacteriota)(sic)(sic)(sic)(sic)(sic)(Cladosporiaceae))(sic)(sic)(sic)(sic)(sic)(sic)(sic).(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic). (sic)(sic)(sic)(sic), (sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic)(sic).

Global warming and increased drought are predicted to alter soil aggregation, biota composition, and carbon (C) balance. Microbial-derived C, such as microbial necromass C (MNC) and glomalin-related soil proteins (GRSP), are critical for soil organic carbon (SOC) stability. However, little is known about how climate change affects microbial-derived C within soil aggregates and its contribution to SOC. Here, we investigated the effects of 4-year warming (ca. 0.68 degrees C) and precipitation reduction (ca. -50% and -25%) on soil GRSP and MNC concentrations in semi-arid secondary grasslands and combined these results with a meta-analysis for GRSP. Results showed that warming increased MNC and its contribution to SOC, while precipitation reduction decreased MNC concentrations. Surprisingly, precipitation reduction increased GRSP concentrations and their contribution to SOC. Field experiments and meta-analysis also revealed that SOC and total nitrogen were negatively correlated with the C contribution of GRSP. Given the chemical recalcitrance of GRSP, this result may imply that the decrease in C and N content under precipitation reduction stimulates the formation of GRSP to enhance its subsequent protection of the SOC pool. Mechanistically, soil biota composition and its interactions dominated the variation in MNC between aggregates and climate change scenarios. The highest MNC concentrations in microaggregates may be attributed to higher fungal diversity, more stable multi-trophic networks, and weaker negative interactions across trophic levels. In addition, precipitation reduction significantly increased the abundance of modules in the multi-trophic network associated with SOC and MNC degradation, which were positively correlated with GRSP accumulation. These results suggest that climate change may regulate SOC dynamics by altering micro-food web structure in soil aggregates. Our study has direct implications for predicting the dynamics and stability of SOC fractions under future climate scenarios.

Precipitation variability induced by climate change has a profound impact on soil carbon dynamics in dryland agroecosystems. To elucidate mechanisms of carbon sequestration in rhizosphere and non-rhizosphere soils under precipitation variability, we conducted an eight-year precipitation manipulation experiment (-50 %,-25 %, ambient, +25 %, +50 %) in croplands of China's Loess Plateau. This research provided a comprehensive assessment of carbon fraction dynamics and the driving factors behind these mechanisms. Our results demonstrate that increased precipitation significantly enhanced soil organic carbon (SOC) in both rhizosphere (+20.5 %) and non-rhizosphere (+22.5 %) soils, although carbon accrual patterns exhibited spatial divergence. Rhizosphere carbon accumulation primarily stemmed from mineral-associated organic carbon (MAOC) (MAOC/ SOC ratio increased from 80.3 % to 88.8 %), whereas non-rhizosphere soil relied on particulate organic carbon (POC) contributions (POC/SOC ratio rose from 12.5 % to 17.5 %). Furthermore, microbial communities displayed functional group decoupling. Precipitation increase shifted bacteria towards r-strategies in both compartments (evidenced by declining oligo/copiotroph ratios and increased rrn copy numbers), while fungal life strategies remained unchanged. Bacterial alpha-diversity increased in both zones, but the response of fungal alpha-diversity diverged, increasing in rhizosphere soil but decreasing in non-rhizosphere soil. Partial least squares path modelling (PLS-PM) revealed compartment-specific sequestration mechanisms. In rhizosphere soil, precipitation stimulated root carbon secretion (70.7 %) and increased the exudate C/N ratio (119.8 %), thereby promoting the proliferation of r-strategists that enhanced MAOC formation and SOC accumulation. In contrast, non-rhizosphere soil depended on precipitation-mediated modulation of microbial diversity and protection of aggregates to facilitate POC formation and SOC accrual. This study proposes divergent carbon sequestration models for the rhizosphere and non-rhizosphere under variable precipitation, providing critical insights for predicting carbon trajectories in climate-sensitive agricultural ecosystems.

Diazotrophs play a vital role in biological nitrogen fixation in agroecosystems. Stoichiometric characterization of soil extracellular enzymes is a key indicator of the effectiveness of microbial nutrient acquisition. However, the mechanisms for exploring the effects of long-term mulching practices on rhizosphere diazotrophic communities and their response to enzyme stoichiometry from the soybean phenology remain unclear. In this study, based on long-term experiments, we adopted four mulching patterns no mulching (CK), straw mulching (SM), plastic mulching (PM) and ridged and plastic mulching (RM). The dynamic changes of rhizosphere soil nutrient characteristics, enzyme stoichiometry characteristics, and diazotrophic dominant communities of soybean were investigated. The study results showed that nutrient content, enzyme activity, and diazotrophic community structure of the rhizosphere soil changed significantly as the soybean growth phenology progressed. Compared to CK, SM treatment enhanced the soil organic carbon (SOC) content (four-leaf (V4) +18.78 %, full-pod (R4) +18.23 %, full maturity (R8) +28.66 %). At R8, the SM treatment significantly increased the soil total nitrogen (STN) content by 16.67 % compared to CK. Our applying vector-threshold (V-T) modeling analysis showed that rhizosphere soil was not carbon (C)-limited. Soil microbial nutrient limitation shifts from nitrogen (N) to phosphorus (P) limitation and finally to N-limitation. In addition, we found that diazotrophs were dominated by Alphaproteobacteria and Betaproteobacteria, at the diazotrophic class level. The dominant diazotrophic genera were Azohydromonas, Bradyrhizobium, and Skermanella. Furthermore, microbial nutrient limitation regressed linearly with the dominant genus. The results indicated a negative correlation between the relative abundance of Azohydromonas, Bradyrhizobium, and Skermanella and microbial N limitation; we observed that mulching measures significantly increased soil mineral N content and promoted an increase in the abundance of dominant diazotrophic genera, thereby effectively mitigating the N limitation faced by microorganisms. Finally, partial least squares path model was used to verify that mulching measures can improve the dominant diazotrophic genera by adjusting the soil physical and chemical properties and regulating VTN/P limitation. Additionally, diazotrophs modify VTN/P limitation by regulating the activity of extracellular enzyme secretion. This study presents a valuable contribution to the domain of enzymatic stoichiometry within agricultural ecosystems, enriching the understanding of relevant processes and offering scientific and technological support for agricultural production.

Soil extracellular enzymes are regulated by a range of biotic and abiotic factors, such as soil moisture and nutrients. In vegetation restoration, due to the heterogeneity of ecosystems and vertical spatial environments of soils, the differences in the response of soil surface and substrate enzyme activities to different stages of succession and the driving mechanisms are unclear. Therefore, using the method of "space instead of time," we analyzed the characteristics of four extracellular enzymes and their influencing factors in the soil surface and bottom layers during the succession of secondary forests in loess hilly areas. The results showed that： ① The activities of β-1,4-glucosidase （BG）； β-D-cellobiose hydrolase （CBH）； and β-1,4-N-acetamido-glucosidase （NAG） were significantly lower in the soil subsoil layer （40-100 cm） compared with those in the 0-20 cm soil layer； however, the activities of alkaline phosphatase （ALP） in the late successional period in the 0-20 cm soil layer were significantly lower than those in the 20-40 cm and 40-60 cm soil layers. Compared with the early and late successional stages, the soil enzyme activities reached the maximum value in the middle stage of succession. ② The succession of secondary forest changed the distribution characteristics of plant community and soil nutrient profile. In the middle stage of succession, the Gleason （G） richness index, Shannon-Wiener diversity index （H）, and Pielou evenness index （E） were the lowest. Compared with that in the early succession stage, the nitrate nitrogen content in the topsoil （0-40 cm） increased significantly in the middle succession stage. Compared with that in the middle succession stage, the soil water content and organic carbon content in the bottom soil layer （40-100 cm） increased significantly in the late succession stage. ③ Redundancy analysis and the least squares path model showed that soil nutrients were the most important factor affecting the soil enzyme activity in the surface layer （0-40 cm） of secondary forest, among which nitrate nitrogen had the highest explanation rate for the change of soil enzyme activity, and soil water content was the key factor to regulate the soil enzyme activity in the bottom layer （40-100 cm）. The results showed that the soil enzyme activity decreased significantly with the increase in soil depth in secondary forest, and the soil enzyme activity was the highest in the middle stage of succession. In the surface layer of soil, the enzyme activity was mainly affected by the content of nitrate nitrogen, and in the bottom layer of soil, and the enzyme activity was mainly regulated by soil water content. The results clarified the profile characteristics of soil enzyme activities at different succession stages and the driving factors of topsoil and subsoil, which provided a basis for formulating scientific forest soil protection policies.

Large-scale afforestation is considered an effective measure to mitigate climate change. However, due to the differences in the properties of soil organic carbon (SOC), the dynamic response of SOC to large-scale afforestation remained unclear. Therefore, we conducted paired sampling (farmland and afforestation) in plantation areas across northern China to evaluate the relationship between SOC stability and SOC increments (ΔSOC) resulting from afforestation. Our findings indicated that SOC-unstable soil supported greater carbon increments through afforestation, but at the expense of reduced SOC stability after afforestation. Additionally, we observed that this relationship exhibited geographical characteristics, with SOC-unstable soil demonstrating a stronger capacity to enhance ΔSOC at higher latitudes, particularly in the topsoil. This is primarily attributed to the fact that higher latitudes and colder climates enhance the contribution of particulate organic carbon to ΔSOC and weaken the regulatory effect of SOC chemical composition (carboxyl and aromatic carbon) on SOC stability after afforestation. These findings underscore the importance of incorporating pre-afforestation SOC stability to accurately predict soil carbon-afforestation feedback.