Over the past century, human activities have intensified heavy metal pollution in lake sediments through various pathways, threatening lake ecosystem health. To formulate effective remediation strategies, it is essential to clarify the sources, concentrations, and speciation of these heavy metals. This study analyzed the concentrations, speciation characteristics, and sources of heavy metals (Cr, Ni, Cu, As, Cd, Pb) across different time periods, based on chronological stratification of sediment cores collected from 22 sampling sites in Lake Chaohu. The results revealed that heavy metal concentrations exhibited a phased increasing trend, with significantly higher levels in the western lake region compared to the eastern region; post-1990, the increase in the west was particularly pronounced. Speciation analysis indicated that Cr, Ni, Cu, As, and Pb were predominantly present in the residual fraction, while Cd was mainly in the acid-soluble fraction, indicating higher bioavailability. Source apportionment using Principal Component Analysis (PCA) and Positive Matrix Factorization (PMF) models demonstrated that natural sources dominated from the 1900s to the 1950s; agricultural sources increased to 41.66 % during the 1950s-1990s; and industrial and traffic sources became the primary anthropogenic contributors post-1990. The average annual growth rate of the Human Activity Intensity (HAI) index increased from 0.09 during 1950-1990 to 0.12 after 1990. This shift indicates that industrialization, urbanization, and traffic development were key drivers exacerbating heavy metal pollution, particularly leading to significant accumulation of reducible and oxidizable heavy metal fractions in the western lake region.

Lakeside wetlands are increasingly exposed to overlapping pressures from eutrophication and land conversion, yet quantitative evidence linking restoration to both carbon (C) storage recovery and water-quality improvement remains limited. Here we use an integrated analytical framework combining high‐resolution remote sensing, process‐based C accounting, and machine‐learning forecasting to assess a 15‐year restoration trajectory of the Shibalianwei Wetland in China’s Chaohu Lake Basin. This approach integrates ecosystem service modeling with machine-learning predictive analytics to capture long-term, non-linear restoration dynamics beyond traditional short-term monitoring. Supervised decision‐tree classification (overall accuracy = 91

Heavy metal contamination in saline-alkali soils poses a dual challenge of excessive alkalinity and nutrient deficiency, particularly phosphorus (P). Traditional biochar remediation often exhibits limited efficacy in these complex matrices due to the high ionic strength and recalcitrant P fractions. In this study, a bamboo vinegar-modified biochar (MB) was developed to simultaneously remediate cadmium (Cd) and activate P in saline-alkali soil. Modification significantly enhanced biochar textural properties, increasing the specific surface area and pore volume by 330.6% and 298.6%, respectively. MB application substantially ameliorated soil alkalinity and salinity, achieving superior reductions in pH (12.2%), ionic strength (48.8%), and sodium adsorption ratio (41.2%) compared to pristine biochar. MB induced a profound redistribution of Cd speciation, decreasing bioavailable Cd by 42.3% and expanding the residual pool by 29.6%. Simultaneously, the P availability coefficient was enhanced by 166.2%, driven by the dissolution of recalcitrant calcium-bound P and the mineralization of organic P. Mechanistic investigations reveal that MB establishes a synergistic remediation pathway integrating persistent acidification, desalination-driven immobilization, and microbial revitalization. The reduction in Cd toxicity and improved physiochemical environment stimulated the absolute abundance of P-solubilizing bacteria and phosphatase-encoding genes (phoC and phoD). Overall, our study highlights the potential of multifunctional modified biochar to overcome chemical and biological barriers, offering a sustainable strategy for the integrated management of nutrient cycles and heavy metal risks.

Accurate prediction of soil carbon (C) and nitrogen (N) cycling is essential for understanding ecosystem functioning, supporting sustainable agriculture, and mitigating climate change. This review summarizes recent progress in predicting soil C-N dynamics, contrasting the mechanistic fidelity yet parametric rigidity of processbased models against the predictive accuracy but limited extrapolative capacity of machine learning (ML). We synthesize specific coupling strategies, from ML-driven parameter optimization and surrogate emulation to physics-informed neural networks, highlighting their potential to improve predictive skill, scalability, and interpretability. Persistent challenges include spatial scale mismatches, increasing computational demands, and the critical need to disentangle multi-dimensional uncertainties (e.g., input, structural, and prediction errors) for large-scale applications. Finally, we outline emerging pathways, particularly the integration of multi-scale remote and proximal sensing and edge-AI frameworks, advocating an interdisciplinary research ecosystem to enable more accurate and actionable predictions of soil C-N dynamics, informing sustainable land management and food security worldwide.

Extreme climate events led to a reshuffling of plant ecological niches, potentially transforming competitive interactions into cooperative ones. This presents a great challenge for future species evolution and agricultural production. Yet, the drivers and mechanistic underpinnings of such interspecific relationship shifts remain poorly understood. Here, we used Lolium perenne L. and Avena sativa L. as a model system to explore how interactions vary under normal temperature (LT) and extreme high temperature (EHT) conditions. Avena sativa L. appeared to suppress Lolium perenne L. potentially via the secretion of inhibitory compounds under LT. In contrast, EHT was associated with a shift toward facilitation: Avena sativa L. root exudates became enriched in lipids and lipid-like molecules, while Lolium perenne L. roots accumulated flavonoids and likely coordinated systemic responses. This included enhanced the accumulation of meloside L in leaves and was linked to bolstered the plant’s antioxidative and ROS-scavenging capacities, potentially contributing to the switch from competition to coordination. Additionally, EHT-induced mixed cropping reduced the abundance of Arthrobacter and MND1, which may lower octulosonic acid production and decrease flavonoids degradation. Collectively, these shifts are proposed to alleviate metabolic suppression of flavonoid biosynthesis, thereby potentially enhancing the thermotolerance of Lolium perenne L. Our findings reveal a potential ecophysiological mechanism of temperature-triggered metabolic reprogramming, informing agricultural management strategies that support food security and sustainability under climate change.

With the acceleration of global urbanization and intensified agricultural activities, approximately 61% of the world’s wetlands have degraded over recent decades, significantly weakening their carbon sequestration capacity. The Shibalianwei Wetland, a crucial tributary system of Lake Chaohu in China, has suffered severe degradation due to land use and cover change, nutrient loading and hydrological disruption. In response, large-scale ecological restoration has been implemented since 2018. To quantify the restoration outcomes, this study integrated remote sensing, GIS, and machine learning techniques, employing the XGBoost model to evaluate and predict carbon sequestration in 2017 and 2024 based on 2010 carbon data. The results reveal that the average carbon density increased from 48.70 t ha−1 in 2017 to 90.18 t ha−1 in 2024, representing an overall increase of 85.2% in total carbon storage. This substantial enhancement is primarily attributed to land use transitions and ecosystem-scale restoration effects, including vegetation recovery and hydrological rehabilitation. Model validation indicated moderate prediction errors (RMSE = 0.47–0.74), with consistent performance across repeated iterations. Together with complementary MAE and R2 metrics, the results suggest that the XGBoost model is capable of capturing relative spatial patterns and restoration-induced changes in wetland carbon sequestration, while retaining reasonable predictive stability under changing landscape conditions. Overall, the findings demonstrate that large-scale wetland restoration can rapidly and effectively enhance regional carbon sink capacity and highlight the potential of data-driven modeling frameworks to support wetland management and carbon-neutrality strategies. This provides important guidance for policymakers to promote sustainable land use and optimize ecosystem management under China’s dual-carbon development goals.

Freezing enhancing the photochemistry of dissolved organic matter (DOM), yet the mechanism of reactive intermediate (RIs) generation influenced by DOM property and structure remain elusive. Here, we demonstrate that freezing induces exceptional amplification of RIs, with steady-state concentrations in ice (-10 °C) surpassing aqueous solutions by 5-41 times. Laser scanning confocal microscopy first visualized cryo-concentration of DOM and RIs in liquid-like regions (LLR). Freeze-concentration mechanism revealed a remarkable 102-104 folds enrichment of RIs in LLR over aqueous phases. Molecular analyses identified tannins and carboxyl-rich acyclic DOM components with abundant oxygen-containing functional groups as critical ice-phase RI precursors, distinct from solution-phase pathways. This ice-specific photochemistry accelerated degradation of imidacloprid and sulfadiazine by 5.17 and 14.8 times, respectively, yielding a unique methoxy‑substituted intermediate exclusive to frozen systems. Density functional theory calculations further revealed thermodynamic selectivity, where the contaminant degradation path with an activation barrier were promoted via both the lowering the effective activation energy and concentration effect upon freezing. These findings establish frozen DOM photochemistry as a pivotal yet overlooked abiotic degradation pathway in cold ecosystems, with critical implications for predicting contaminant fate under climate-amplified freeze-thaw cycling.

China's terrestrial carbon sink, quantified by net ecosystem productivity (NEP), has exhibited significant yet spatially heterogeneous growth over the past four decades, driven by climate change, land use transitions, and ecological restoration policies. However, the nonlinearity of NEP enhancement and its coupling mechanisms with dynamic land use patterns remain poorly understood. This study integrates linear trend analysis, ensemble empirical mode decomposition, and boosted regression tree (BRT) modeling to systematically unravel the nonlinear characteristics of NEP trends (1981-2019) and their landscape-mediated drivers across four ecoregions. Key findings reveal that: (1) While 43.75% of China's land area showed a linear increase in NEP, only 13.46% exhibited monotonic growth (Trend(IN)), whereas 16.46% displayed trend reversals (Trend(DE-TO-IN)), highlighting dominant nonlinear dynamics. (2) Land use pattern indices (LUPI)-spanning fragmentation (PD), dominance (LPI), connectivity (CONTAG), shape complexity (AWMPFD), and diversity (SHDI)-demonstrated divergent trajectories: South China and the Tibetan Plateau (TP) experienced increasing fragmentation (PD increases) alongside declining connectivity (CONTAG decreases), while Northwest China (NWC) showed inverse patterns, reflecting region-specific anthropogenic and ecological pressures. (3) Trend(IN) regions (e.g., NWC and TP) were governed by LPI in NWC and CONTAG, where threshold exceedance (slope > 0) stabilized carbon accumulation. The trend reversal regions of NEP relied on PD and AWMPFD, where initial declines in edge effects (slope < 0) preceded NEP recovery. Notably, NEP responses to LUPI gradients exhibited U-shaped thresholds (slope = 0) in monotonically increasing regions but monotonic shifts in Trend(DE-TO-IN) zones, underscoring legacy effects of historical landscape configurations. By bridging landscape ecological theory with nonlinear trend decomposition, this study advances the understanding of how multiscale land use patterns regulate carbon sequestration, offering actionable insights for spatially adaptive land management to support China's "dual carbon" goals.

With the rapid advancement of agricultural modernization,biodegradable mulch(BDM)in farmland has become increasingly prevalent.However,little is known about the effects of BDM buried in soil on bacterial communities.In this study,a burial experiment was conducted on farmland using BDM(PBAT+PLA).The bacterial communities on the surface of the BDM(H8)at different burial stages were analyzed through Illumina NovaSeq high-throughput sequencing technology.The landfill experiment was carried out for a total of 75 days.The results revealed that the bacterial α-diversity in BDM was significantly lower than that in the control soil,with a notable decrease in soil bacterial α-diversity on the BDM surface in the later stages of burial compared to that in the early stages(P<0.05).The bacterial community of control soil was significantly different from that of BDM(P<0.01).The relative abundance of the Proteobacteria phylum in the BDM was significantly higher than that in the control soil(P<0.05).LEfSe analysis revealed significant differences in taxa between the buried BDM and the control group across burial stages.During the early stage,Pseudarthrobacter and Acidovorax showed significant differences.Variovorax and Mycobacterium exhibited differences in the mid-stage,whereas Hydrogenophaga and Chryseolinea differed significantly in the late stage.These taxa served as indicator species for their corresponding burial stages.Functional analysis of bacterial communities revealed an enhancement of carbon metabolism-related functions in the bacterial community on the BDM surface during the early and middle stages.Moreover,network analysis revealed that,compared to that in the control soil,BDM exhibited a simpler network structure of the bacterial community,higher modularity values,and more negative correlation connections.These findings collectively provide a scientific foundation for a comprehensive understanding of the impact of BDM on the soil microecological environment.

Polyvinyl chloride (PVC) is a widely used plastic, but the potential risk of heavy metal additive release from PVC microplastics (MPs) has not been fully explored. This study evaluates the release of lead (Pb) from recycled PVC MPs under natural conditions. The released Pb concentration in the dark was 1079.5-1109.7, 551.4-571.6, and 374.1-433.0 mu g/L in agricultural, sea, and river/lake water, respectively. In contrast, the Pb release was markedly inhibited by 34.1-59.1 % under irradiation. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), fluorescence emission-excitation matrix (EEM) spectroscopy, and Mantel test revealed that the dissolved organic matter (DOM), especially lignin/carboxyl-rich acyclic component (41.8-84.8 %), can complex with Pb to facilitate its release from PVC in the dark. However, the Pb released upon irradiation was first promoted and then inhibited. The promotion ascribed to the broken of MPs by reactive intermediates (RIs) including 3 DOM*, 1 O 2 , and center dot OH [(0.5-12.6) x 10- 13 , (1.2-10.9) x 10- 13 and (0.1-8.9) x 10-17 mol/L, respectively]. The inhibition was attributed to two reasons: the photobleaching of DOM reduced Pb dissolution complexed by DOM; the increase of oxygen-containing functional groups enhanced the Pb adsorption on the surface of MPs. In addition, the Pb released from PVC MPs significantly inhibits the growth of Nannochloropsis sp. in seawater. These findings reveal the complicated release mechanism of Pb from MPs under environmental conditions.

Aquatic ecosystems worldwide are increasingly threatened by eutrophication and anthropogenic disturbances, resulting in biodiversity loss and functional degradation. East Taihu Lake, a typical shallow lake in China, has experienced severe ecological stress due to nutrient enrichment and habitat alteration. We investigated the spatiotemporal patterns of macroinvertebrate communities to assess the degree of disturbance to aquatic ecosystems. Seasonal sampling was conducted across five functional areas from 2020 to 2021, including measurements of physicochemical water parameters, aquatic vegetation, and macroinvertebrate assemblages. A total of 28 species were identified, with Bellamya purificata, Limnodrilus, and Tubifex as dominant taxa. Statistical analyses revealed that water depth and aquatic vegetation coverage were the key drivers shaping community composition and diversity. Mollusks dominated in shallow, vegetated areas with high transparency, while Oligochaetes and Chlamydia were more abundant in deeper waters, reflecting tolerance to low-oxygen and eutrophic conditions. This study highlights the ecological benefits of aquatic vegetation in enhancing habitat complexity, supporting macroinvertebrate diversity, and improving water quality. These findings provide valuable scientific support for adaptive management of shallow lakes, emphasizing the restoration of aquatic plants and regulation of hydrological conditions as effective strategies to promote benthic biodiversity and longterm ecosystem resilience.

This study investigated the efficiencies and underlying mechanism of a combined modified zeolite and chabazite cover to the in situ control of nitrogen (N) and phosphorus (P) release from sediments through cultivation experiments. High-throughput sequencing was employed to revealed the impact of this cover treatment on sediment microbial diversity. Results indicated that modified zeolite and sepiolite cover (MZ-MSs) exhibited a higher efficiency in inhibiting N and P release from sediments than the raw material cover (RZ-RS). Compared to the control (CK), the final reduction rates of ammonia (NH4+- N) and phosphate (PO43- - P) in the overlying water of MZ-MSs reached 86.05 % and 98.36 %, respectively. Furthermore, NH4+- N and PO4 3- -P concentrations in the interstitial water under the MZ-MSs treatment condition were significantly lower than those under no and RZ-RS treatment conditions. Sediment P fractions results revealed that RZ-RS cover had minimal effect on sediment P fractions, whereas the treatment with MZ-MSs led to a significant reduction in labile P, with a predominant proportion (96.01 %) existing in the stable P form of metal oxide-bound P (NaOH-P), calcium-bound P (HCl-P) and residual P (Res-P), characterized by minimal potential for re-release. Sediment microbial analysis indicated that material covers had minor effects on community structure, mainly manifesting in bacterial abundance distribution with no impact on species composition. Overall, the combined modified zeolite and sepiolite cover presents a promising approach for controlling N and P release from sediments.

Plant-microbe interactions regulate soil greenhouse gas (GHGs) fluxes, yet their responses to climate extremes remains unclear. In a factorial experiment combining plant composition (bare soil, monoculture, intercropping) with contrasting temperatures, we found that the soil global warming potential (GWP) mitigation effect of intercropping under extreme high temperature (EHT) significantly declined by 17.4 % compared with normal temperature (LT). EHT suppressed plant biomass (-41.9 % to -86.6 %), diminished soil carbon sequestration (-0.9 % to -6.9 %), and increased the r/K strategy ratios (+0.7 % to +5.7 %). It further erased the clear separation between intercropping and monoculture microbial communities evident under LT and upregulated key N-loss genes (e.g., nirS, norC), jointly undermining the microbial basis of plant-mediated GHGs mitigation. Our findings highlight that while plant diversity stabilizes soil biogeochemistry and constrains GHGs release, its buffering efficacy is inherently fragile under EHT, providing new evidence of limits to biotic regulation in a warming world.

Saline-alkali soils co-contaminated with arsenic (As) threaten agricultural sustainability. We prepared iron-loaded biochar and applied alone or in combination with desulfurized gypsum to remediate saline-alkali soils contaminated with different arsenic species (Dimethylarsenic (DMA) and NaAsO2). Results showed that the application of iron-loaded biochar significantly reduced soil pH (by 2.4-7.0 %), while cation exchange capacity (CEC) and exchangeable Na+ concentrations also decreased with increasing biochar dosage. The availability of DMA and NaAsO2 was reduced by 46.2 % and 63.7 %, respectively, after 29 days under optimal iron-loaded biochar dosages (4 % for DMA, 2 % for NaAsO2). Arsenic immobilization was attributed to surface complexation with iron oxides, redox transformation, and time-dependent adsorption. These findings demonstrate the dual function of iron-loaded biochar in alleviating soil salinity and reducing arsenic mobility and innovatively revealed the differences of iron-loaded biochar in the remediation of organic and inorganic As contaminated saline-alkali soils, providing both efficient and sustainable solutions for the green remediation of As-saline-alkali composite contaminated soil.

South-West China (SWC) is a pivotal region for global greening, recognized as having great carbon sink potential. Multiple evidence underscores the expanding contribution of SWC's carbon sink to the global carbon sink enhancement. However, our understanding of carbon sink dynamics and the response to climate across bedrock remains limited. In this study, we investigated the divergence in trends in carbon sink across bedrocks, evaluating their respective contributions of bedrocks to the overall carbon sink in SWC. Additionally, we assessed the dominant climatic factors and examined how bedrocks shape the response of carbon sink to climate change. Our results revealed a notable increase in the regional carbon sink, with an average rate of 3.58 TgC/yr from 1981 to 2019. Continuous Carbonate Rocks (CCR) exhibited the highest increased rate of total carbon sequestration (1.57 TgC/yr), surpassing Discontinuous Carbonate Rocks (DCR) by threefold. Non-karst areas contributed the most to both the mean and interannual variations of the overall carbon sink, with CCR exerting the most contribution to the trends. Over time, the contribution of CCR to the overall carbon sink escalated, while the contributions of DCR and non-karst declined. All bedrocks displayed negative correlations between NEP and temperature, with DCR showing higher susceptibility. Non-karst areas experienced adverse impacts from vapor pressure deficit, while CCR benefited from positive soil moisture effects. Our findings implied that bedrock indeed played a critical role in the variations in NEP and the response of NEP to climate change. Bedrock regulated climatic controls on carbon sink through soil water availability as soil water availability is affected by the lithology of basement carbonate. This novel understanding emphasizes the necessity for tailored ecological restoration initiatives that consider the distinctive lithological features of the karst ecosystem, and holds significance for implementing ecologically sound projects in karst regions.

Monitoring trends in gross primary productivity (GPP) is essential for assessing changes in carbon sinks. The implementation of rocky desertification control in karst areas has led to an increase in GPP. However, its impact on the nonlinearity of GPP increase has not been determined. Based on the ensemble empirical mode decomposition (EEMD) method, this paper analyzed the nonlinear trend of GPP in the Karst region of southwest China from 1982 to 2018 and clarified the impact of rocky desertification control on the nonlinear trend of GPP, the results show that: (1) The Mann-Kendall method found that 47.17% and 50.11% of the study areas showed nonsignificant change and significant increase in GPP, however, 6.72% and 8.58% of the regions with nonsignificant change and significant increase respectively show the trend reversal from increase to decrease with EEMD method, moreover, 2.94% and 4.19% show the trend reversal from decrease to increase, respectively; (2) Rocky desertification control changed GPP more significantly in rock desertification area than nonrocky desertification area. With the aggravation of rocky desertification, the control effect becomes better, which is reflected in the increasing proportion of monotonic increases in GPP. However, for severe rocky desertification areas, the effect of governance is more reflected in the large proportion of GPP from reduction to increase. (3) The control effect is better, but the risk of carbon sink reduction is higher in changed rocky desertification areas than those in unchanged rocky desertification areas. In the meantime, the mitigation of rocky desertification can favor the increasing of GPP in the areas with severe and moderate rocky desertification, while it can just reduce the risk of decreasing of GPP in the areas with potential and slight rocky desertification. Overall, this study enhances our understanding of the impact of rocky desertification control on carbon cycle processes in both changed and unchanged rocky desertification areas.

Water availability (WA) is a key factor influencing the carbon cycle of terrestrial ecosystems under climate warming, but its effects on gross primary production (EWA-GPP) at multiple time scales are poorly understood. We used ensemble empirical mode decomposition (EEMD) and partial correlation analysis to assess the WA-GPP relationship (RWA-GPP) at different time scales, and geographically weighted regression (GWR) to analyze their temporal dynamics from 1982 to 2018 with multiple GPP datasets, including near-infrared radiance of vegetation GPP, FLUXCOM GPP, and eddy covariance-light-use efficiency GPP. We found that the 3- and 7-year time scales dominated global WA variability (61.18% and 11.95%), followed by the 17- and 40-year time scales (7.28% and 8.23%). The long-term trend also influenced 10.83% of the regions, mainly in humid areas. We found consistent spatiotemporal patterns of the EWA-GPP and RWA-GPP with different source products: In high-latitude regions, RWA-GPP changed from negative to positive as the time scale increased, while the opposite occurred in mid-low latitudes. Forests had weak RWA-GPP at all time scales, shrublands showed negative RWA-GPP at long time scales, and grassland (GL) showed a positive RWA-GPP at short time scales. Globally, the EWA-GPP, whether positive or negative, enhanced significantly at 3-, 7-, and 17-year time scales. For arid and humid zones, the semi-arid and sub-humid zones experienced a faster increase in the positive EWA-GPP, whereas the humid zones experienced a faster increase in the negative EWA-GPP. At the ecosystem types, the positive EWA-GPP at a 3-year time scale increased faster in GL, deciduous broadleaf forest, and savanna (SA), whereas the negative EWA-GPP at other time scales increased faster in evergreen needleleaf forest, woody savannas, and SA. Our study reveals the complex and dynamic EWA-GPP at multiple time scales, which provides a new perspective for understanding the responses of terrestrial ecosystems to climate change.

In recent decades, alpine meadows have experienced severe degradation owing to external disturbances. Although soil microorganisms are critical for ecosystem services, little is known about their responses to soil degradation and the potential patterns in alpine meadows. To solve this question, we collected and analyzed soil samples from three degraded alpine meadows situated on the Qinghai-Tibet Plateau. We aimed to examine the effects of degradation on soil microbial diversity and identify the ecological predictors for the diversity of bacteria and fungi. Our results showed that alpine meadow degradation significantly changed soil bacterial and fungal diversity and community composition. Specifically, the relationship between bacterial and fungal diversity and degradation intensity was a hump-shaped, with the highest diversity observed at a moderate degradation level. Additionally, alpine meadow degradation-induced changes in microbial diversity were strongly correlated with decreased plant production, with fungal diversity showing a closer link with below-ground biomass (BGB) than with bacterial diversity. Our findings offer empirical evidence that intermediate disturbance (i.e., moderate degradation) may be beneficial for supporting soil biodiversity. This has important implications for informing policy and management strategies meant to conserve soil biodiversity and ecosystem services when facing anthropogenic change.

The paddy field is a hot area of biogeochemical process. The paddy water has a large capacity in photogeneration of reactive intermediates (RIs) due to abundant photosensitive dissolved organic matter (DOM), which is influenced by the spatial heterogeneity of paddy soils but rarely been explored. Our work presents the first investigation of the role of soil properties on photochemistry in paddy water. Soil organic matter (SOM), determined by the temperature, was the dominant factor for the photo-generation of RIs in paddy water of main rice producing areas. The RI concentrations generated with abundant SOM from cool regions are 0.05-8.71 times higher than those for the warm regions in China. The humic-like substance and aromatic-like compounds of DOM plays an essential role in RIs generation, which is abundant in paddy soils rich in SOM from Chinese cool regions. In addition, RIs can efficiently accelerate the photo-ammonification of urea and free amino acids by 15.2 %-164 %, leading to 0.13-0.17 mmol/L/d photo-produced ammonium after fertilization, which is preferentially absorbed by rice. The findings of this study will extend our knowledge of the geochemistry of global paddy field ecosystem. The potential role of RIs in nitrogen cycle should be highlighted in the agroecosystem.