In the context of global climate change, carbon emissions have become an increasingly pressing concern.As one of the world’s largest carbon emitters, it is a critical strategic objective for China to achieve both carbon peaking and carbon neutrality.The Yangtze River Delta region (YRDR), as a significant growth pole of China′s economy, plays a pivotal role in enhancing carbon emission efficiency and overall carbon performance to meet national reduction targets.Utilizing data from the urban agglomeration of the YRDR from 2004 to 2022, this study analyzed the effects of regional integration on carbon performance.The fixed-effect models and spatial Durbin models were used.The empirical findings were summarized as follows: Firstly, regional integration fostered improvements in urban carbon performance.However, there existed a lag effect alongside a "snowball" effect in the development of such performance.This enhancement primarily occurred through three mechanisms: high-quality economic development, increased openness to external markets, and promotion of investment.Secondly, environmental regulation amplified the positive impact that regional integration imposed on urban carbon performance.Conversely, energy intensity exerted a negative moderating influence.Thirdly, while regional integration positively influenced carbon performance within the YRDR itself, it exhibited a negative spatial spillover effect on the neighboring areas, presenting a demonstration of a "siphon" effect.It was imperative to expedite the establishment of a unified regional carbon market along with an efficient division-of-labor system within green industrial chains.Strategies were suggested to facilitate the achievement of the "dual carbon" goals, which included the acceleration of the development of a regionally unified carbon market and a green industrial chain allocation system, the establishment of consortia for green technology research, and the optimization of the structure of foreign capital utilization.

Under the background of “double carbon” target, the construction of a new energy system, the photovoltaic (PV) industry is facing significant development opportunities.The Yangtze River Delta (YRD) is the main agglomeration area for China′s PV industry and its leading enterprises.The study of the spatial distribution evolution and the influencing factors of the PV industry chain is of great significance.Based on the industrial and commercial registration data of PV enterprises, this paper constructed a spatial database of the PV industry chain in the YRD region from 2005 to 2023, by combining urban socio-economic statistical data to portray the spatio-temporal evolution characteristics of the key upstream, midstream and downstream of the PV industry chain.The driving mechanism of the PV industry distribution and location selection was explored by using the fixed-effects model.The results showed that: (1) The spatial agglomeration and diffusion of PV enterprises in the YRD coexisted from 2005 to 2023.A spatial evolution trend of “large diffusion and small agglomeration” was presented; (2) The links of the PV industry chain were mainly concentrated in Southern Jiangsu and Northeastern Zhejiang, showing the spatial evolution of “sporadic distribution - belt distribution” or “sporadic distribution - piece distribution”; (3) The spatial diffusion of the PV industry in YRD was mainly manifested in neighborhood diffusion and channel diffusion; (4) The key factors affecting the location of PV enterprises included the urban industrial and economic base, low-carbon development policy, scientific and technological innovation capacity, and the level of globalization.There existed significant spatio-temporal heterogeneity in the driving mechanism of the different factors, as well as significant differences in the spatial distribution response of the upstream, midstream, and downstream segments.The above results helped to enrich the empirical research on the distribution of strategic emerging industries in humanistic economic geography, and had reference value for promoting the collaborative innovation and high-quality development of PV industry in the YRD.

Low-carbon development of natural gas industry is an important way for China to achieve the goals of carbon peaking and carbon neutrality.Based on the two units of fuel combustion and system diffusion, the calculation system of carbon emissions of natural gas industry was constructed in this study.By introducing the principle of material conservation, the improved Super-SBM-Undesirable model was established.Combined with the panel data of Beijing-Tianjin-Hebei, Yangtze River Delta and Sichuan-Chongqing regions from 2010 to 2022, the spatial-temporal differentiation of industrial carbon emissions and low-carbon economic efficiency was empirically investigated.The results showed that: (1) the carbon emissions of natural gas industry in the three clusters showed a fluctuating upward trend, which was due to the increase of industrial carbon contribution driven by the large-scale development of natural gas under the goals of carbon peaking and carbon neutrality.The carbon emission of fuel combustion was dominant.The carbon contribution of energy processing and conversion in Beijing-Tianjin-Hebei region was large, due to the demand for central heating in winter.The carbon contribution of system diffusion was small.However, due to the aggregation characteristics of the upstream industrial chain, some diffusion emissions occurred in the exploration, mining, processing, and treatment stages.(2) The resource endowment advantage in Sichuan-Chongqing region leaded to the high-quality development of natural gas industry, resulting the highest efficiency of low-carbon economic.The political orientation of Beijing and Tianjin ensured the regional energy supply, but their self-sufficiency in natural gas was low.In addition, Hebei was facing the problem of air pollution in the process of industrial undertaking.Therefore, the efficiency of Beijing-Tianjin-Hebei region was lower than that of Sichuan-Chongqing region.The efficiency in the Yangtze River Delta region showed a significant regional difference.This was mainly due to the fact that in recent years, Jiangsu, Zhejiang and Shanghai had taken the full advantages of regional coordinated development and intelligent transformation, and had vigorously expanded the emerging growth points of natural gas industry.However, the development foundation of Anhui's natural gas industry was relatively weak.

Smart city construction is a critical pathway to promote green and low-carbon urban development, yet its mechanism for influencing the carbon total factor productivity requires further exploration.Based on the panel data of 108 cities in the Yangtze River Economic Belt (YREB) from 2007 to 2022, this study used the non-radial directional distance function (NDDF) to measure the carbon total factor productivity.While the smart city pilot policy is treated as a quasi-natural experiment, and through the multi-time point difference-in-differences model and the four-stage mediating effect model, this study systematically analyzed the direct effect, heterogeneity characteristics and green technology innovation transmission path of impact of smart city construction on the carbon total factor productivity.The results showed that: (1) The carbon total factor productivity in the YREB exhibited an overall upward trend with fluctuations, yet significant regional disparities existed, with a spatial gradient pattern of "downstream > midstream > upstream"; (2) Smart city construction significantly enhanced the carbon total factor productivity in the YREB, especially for midstream and downstream cities, large-sized cities and non-resource-based cities; (3) Green technology innovation served as the key intermediary channel for smart city construction to promote the carbon total factor productivity.Based on these results, it was suggested that the provinces and cities in the YREB establish regional collaborative mechanisms, implement differentiated smart carbon reduction strategies according to the endowments of cities, and strengthen the innovation and transformation of green technologies to promote the low-carbon transformation across the whole basin.

The pilot policy of low-carbon cities is a major strategic initiative for China′s socio-economic development.It is also a significant opportunity to accelerate the transformation of the economic development model and structural adjustment.As a key engine of China′s economic growth, the Yangtze River Economic Belt (YREB) is more urgent to achieve its green and efficient development.Based on the panel data of 108 prefecture-level and above cities in the YREB from 2007 to 2021, this study employed the multi-period DID method to explore the impact of low-carbon city pilot policies on their green total factor productivity (GTFP).The findings revealed that: (1) low-carbon city pilot policies had significantly enhanced the GTFP of cities in the YREB; (2) the pilot policy had a significant positive impact on the GTFP of cities (Shanghai, Jiangsu, Zhejiang, Anhui) in the lower reaches of the YREB, while the impact on cities in the middle and upper reaches was not significant; The GTFP of key environmental protection cities was significantly positively affected by the low-carbon city pilot policies; Old industrial base cities' GTFP was significantly positively influenced by low-carbon city pilot policies; Non-resource-based cities were significantly positively influenced by low-carbon city pilot policies; (3) The low-carbon city pilot policies could enhance GTFP by promoting the optimization of energy consumption structure and industrial agglomeration.Finally, the study provided relevant policy recommendations for the low-carbon transformation of cities in the Yangtze River Economic Belt.

Based on panel data from 110 cities in the Yangtze River Economic Belt (YREB) from 2011 to 2021, this study constructed a comprehensive evaluation for the digital new-qualitative productivity and high-quality agricultural development in the YREB.Panel regression, coupling coordination degree models, and spatial variation function were employed to explore the coupling relationship and spatio-temporal evolution.The results indicated that there was a significant dynamic coupling relationship between the two systems.The digital new-qualitative productivity had a stronger impact on high-quality agricultural development.The mean level was in the order of the middle reaches < the upstream reaches < the downstream reaches.Regarding spatial distribution, the coupling coordination degree exhibited a spatial positive correlation globally.The high-high agglomeration areas were mainly concentrated in the Yangtze River Delta urban agglomeration and the low-low agglomeration areas were mainly in the Chengdu-Chongqing urban agglomeration and Central Guizhou urban agglomeration.The spatial randomness effect on the coupling coordination degree was gradually increasing, while the structural effect was gradually decreasing.Overall, the spatial differences were decreasing, and the local imbalances still existed.

Based on data from 124 prefecture-level and above cities in the Yangtze River Economic Belt from 2012 to 2022, this study constructed a comprehensive evaluation index system for high-quality tourism development under the common prosperity goals.Utilizing the entropy-TOPSIS method, exploratory spatial data analysis (ESDA), and Dagum Gini coefficient, we systematically investigated the spatiotemporal characteristics, evolutionary trends, and regional disparities of tourism high-quality development.Furthermore, the geographical convergent cross-mapping (GCCM) model was employed to analyze causal relationships among variables within the tourism development system.Key findings included: ① The high-quality tourism development in the Yangtze River Economic Belt maintained medium-low levels with a steady growth during the study period, where ecological conservation and coordinated development demonstrated relatively strong performance while other dimensions lagged; ② A distinct east-west gradient pattern emerged, characterized by an “east-hot-west-cold” spatial distribution; ③ Spatial disparities gradually narrowed, with interregional differences constituting the primary source (>60%) of overall variation; ④ Government intervention, financial services, infrastructure, consumption, and population exhibited causal relationships with tourism development quality, though the direction of causality showed significant heterogeneity across dimensions.

Safeguarding and improving residents′ well-being is a central objective of Chinese-style modernization.Enhancing well-being through cultural and tourism integration is both a key initiative and strategic goal in building a strong tourism nation.Based on panel data from 108 prefecture-level cities in the Yangtze River Economic Belt (2006-2023), this study employed a Spatial Durbin Model to examine the spatial spillover effects of culture-tourism integration on residents′ Well-being.The main findings were as follows: (1) Both the level of culture-tourism integration and residents′ well-being remained generally low, with absolute disparities widening over time.In the early stages, a clear polarization emerged, manifesting a “Matthew effect” where strong regions grew stronger.However, this trend weakened in later years.(2) Culture-tourism integration exhibited a spatial pattern of low-value clustering and high-value dispersion, forming a “core-periphery” structure centered around provincial capitals.The residents′ well-being followed a “downstream-midstream-upstream” gradient, with Shanghai and Chongqing forming a “dual-core” spatial layout.The pattern reflected a clear influence of administrative hierarchy, with sub-dimensional well-being showing a stepwise decline from downstream to upstream areas.(3) There existed a significant spatial correlation between culture-tourism integration and residents′ well-being, with localized clusters dominated by H-H and L-L types.Integration exerted both significant positive direct and spatial spillover effects, i.e., a 1% increase in integration could cause a 0.373% rise in local well-being and a 0.238% rise in neighboring well-being.Among the dimensions of well-being, the impact followed the order of social well-being > economic well-being > environmental well-being.(4) The spillover effects displayed a marked regional heterogeneity.At the basin level, the upstream region experienced the strongest direct effect, while the downstream region benefited mostly from positive spillovers.At the urban cluster level, Dianzhong and Chengdu-Chongqing exhibited the largest direct effects, while the Yangtze River Delta and Chengdu-Chongqing showed significant positive spillover effects.

Highway traffic accessibility plays a vital role in linking revolutionary villages with scenic areas and county towns, thereby enhancing tourism appeal, supporting service capacity. The Dabie Mountains in Anhui Province were selected, and ArcGIS tools and a coupling coordination model were employed to quantitatively examine the spatial distribution of revolutionary villages and scenic areas, measured the road accessibility of revolutionary villages-scenic areas and revolutionary villages-county towns, and analyzed the spatial coupling characteristics of these two linkages. The results showed that: (1) Revolutionary villages and scenic areas exhibited a spatial pattern of overall dispersion with localized clustering, yet their concentrated areas were spatially separated. (2) The travel time between villages and scenic areas ranges from 67.83 to 192.05 minutes, indicating low overall accessibility with significant internal disparities and a pronounced core-periphery structure. (3) Accessibility between villages and county towns was generally better, with travel times within 104.10 minutes and mostly under 60 minutes, displaying a pattern of accessibility decreasing from county centers to peripheral areas. (4) The coupling coordination degree of road accessibility exhibited a spatial gradient, declining from the north and central-eastern to the west and south, with a relatively high degree of spatial coupling between village-scenic and village-town linkages. Based on accessibility coordination, the provincial list of key revolutionary villages, and proximity to scenic routes, this study identifies high-potential villages for red-green integration. Strategies were further proposed to improve red-green integration in the Dabie Mountains by enhancing multidimensional accessibility, offering a scientific reference for promoting high-quality, integrated development in former revolutionary base areas.

This study explored the spatiotemporal evolution patterns of total water consumption, water use structure, and water use efficiency in Jiangxi Province and its 11 cities.The spatiotemporal heterogeneity of water resource carrying capacity was studied to provide a scientific basis for regional water resource management and sustainable utilization.The data of water resources, industrial water use, socioeconomic factors, and ecological replenishment were collected.The Theil coefficient was used to analyze regional distribution differences in water resource development and utilization.The information entropy was used to assess the rationality of water use structure, and the entropy-weighted TOPSIS model was used to evaluate water resource carrying capacity.The results indicated that the proportion of total water consumption by each city remained relatively stable over time.However, in recent years, due to differences in industrial development levels among the cities, the disparities in industrial water use and ecological water use had increased.Agricultural water use dominated in all cities of Jiangxi Province, while the proportion of industrial water use was gradually decreasing, and the proportion of ecological water use was significantly increasing.Overall, there were considerable differences in water use structures among the cities, e.g.Nanchang and Pingxiang cities demonstrated the most optimal water use structures.The water resource carrying capacity in the northern part of Jiangxi Province was better than that in the southern part.The provincial capital Nanchang city outperformed the neighboring cities.Nanchang and Xinyu had the highest water resource carrying capacity.Yichun and Shangrao were ranked high in terms of water resource subsystem carrying capacity, and Nanchang and Xinyu had the best performance in social subsystem, and Nanchang and Jingdezhen cities had the highest carrying capacity in ecological subsystem.

Optimizing land use structures in metropolitan areas from a carbon-oxygen balance perspective is critical for enhancing ecosystem services and advancing sustainable development.This study constructed a multi-objective optimization framework that integrated ecological status assessment, land demand forecasting, and multi-scenario simulation.The carbon-oxygen balance method, ARIMA model, and NSGA-II algorithm were adopted.Taking 2020 as the base year and 2030 as the target year, the carbon-oxygen balance of land use and multi-scenario land-use optimization plans in Wuhan-Ezhou-Huanggang-Huangshi (WEHH) metropolitan area were evaluated and analyzed.The results showed that: (1) From 2010 to 2020, the carbon emissions in WEHH increased by 31.8%, and oxygen consumption by 27.34%, which indicated a significant increase of pressure for the ecosystem.Meanwhile, a notable decrease was identified in the carbon fixation and oxygen release capacity of the ecological land.The decrease for the cultivated land and forest land was at a rate of4.18% and 3.64%, respectively.(2) Elasticity analysis revealed that there existed a greater adjustment potential for the construction and cultivated land, while the wetlands and the unused land should remain restricted.The forest land, unused land, cultivated land, and grassland exhibited a high sensitivity (≈0.6) to uncertainty, which implied a need for prioritized and adaptive allocation.(3) Multi-scenario optimization highlighted trade-offs across development pathways.The scenario 1 of ecological-economic balance might moderately expand the construction and forest land, and improve ecological benefits by 1.6% and economic output by 19.3%.Scenario 2 of prioritizing ecological integrity by an increase of forest land of 6.6% and an enhancement of wetland and grassland protection might achieve an ecological benefit of 3.1% at a cost of 3.5% decline in economic performance.This scenario was appropriate for ecologically sensitive areas.Scenario 3 that emphasized economic growth through a 33.8% expansion of construction land, might boost economic benefit by 38.3%, but might reduce ecological benefits by 1.6%.Scenario 3 was more applicable to highly industrialized areas.Overall, it was essential to incorporate ecological carrying capacity as a core constraint, and to adopt differentiated, goal-oriented land governance strategies, for guiding sustainable land use transitions in metropolitan areas.

In order to further understand the current status of fish diversity in the National Aquatic Germplasm Resources Reserve of Procypris rabaudi and Spinibarbus sinensis in the Jialing River, a field study was carried out in June (summer) and November (winter) 2022.The fish resources in the core area and experimental area of the reserve were comprehensively investigated by combining the traditional fishery resources survey method and eDNA technology.A total of 63 fish species belonging to 44 genera, 9 families and 3 orders were investigated by the two monitoring methods.The Cypriniformes had the largest number of species, accounting for 73.02% of the total species.Analyzed from three ecological types of feeding habits, spawning types and habitat water layers, the fish in the reserve were mainly omnivorous fish (49.21%), fish spawning adhesive eggs (50.79%), and bottom-dwelling fish (46.03%).In terms of diversity indices, the average values of the Shannon -wiener diversity index, Simpson dominance index, Delta + index and Lambda + index of the traditional fishery resources survey method were 2.63, 0.86, 58.89 and 402.8 respectively.The average values of the corresponding indices of the eDNA method were 1.57, 0.60, 59.89 and 348.93, respectively.Both survey methods showed that the diversity index of the core area was higher than that of the experimental area, and the diversity index in summer was higher than that in winter.The T-test results showed that there was no significant difference in the diversity indices of the two survey methods (p > 0.05).One-way analysis of similarity (Anosim) and Jaccard similarity coefficient indicated that there were significant differences in the fish species composition between different habitats (core area and experimental area) and different seasons (summer and winter) in the reserve (p < 0.01) The fish communities were moderately dissimilar.The above results showed that the fish diversity in the reserve was at a general level to a rich level.The similarity of fish species composition between different habitats and seasons was low.In addition, the eDNA technology could be combined with the traditional survey method to complement each other, and it demonstrated a good applicability in the study of fish diversity.

Exploring the complexity and dynamics of the spatial association network of urban ecological resilience can provide a new research perspective for achieving ecological collaborative development in the Yangtze River Delta Region (YRDR).This study used 41 prefecture-level cities in the YRDR as the research samples, and performed a measurement of urban ecological resilience levels from 2013 to 2022.The entropy weight-TOPSIS method was adopted.A spatial association matrix was constructed, and the social network analysis was employed to examine the evolution characteristics and driving mechanisms of the urban ecological resilience.The results showed that: (1)The overall level of urban ecological resilience in the YRDR had steadily improved, and the range of high-resilience areas had gradually expanded.However, regional disparities remained evident, showing a spatiotemporal distribution pattern of high resilience in the southeast and low resilience in the northwest.The spatial association network had gradually formed, and the overall network connection density had increased, showing the features of intensification and multicentralization.(2)The overall network structure had become tighter and more stable.The core cities (such as Shanghai and Hangzhou) played a key role as central actors and intermediaries in the network, and displayed a "core-periphery" spatial distribution.The urban ecological resilience spatial association could be divided into the net spillover, main beneficiary, and "broker" sectors.The distribution of members in these sectors aligned with the geographical characteristics of the Yangtze River Delta's core economic zone, central connecting belt, and peripheral hinterlands.(3)Socio-economic factors such as economic development, technological innovation levels, foreign openness, and policy regulation had a significant impact on the formation of the urban ecological resilience spatial association network.

Promoting the integrated development of carbonreduction, pollution reduction, green expansion, and economic growth is essential for achieving sustainable high-quality development in the Yangtze River Economic Belt (YREB). A multidimensional evaluation framework integrating these dimensions was developed using panel data from 11 provincial regions (2011-2022). Through integrated application of extended measurement model, geographic detector model, and spatiotemporal geographically weighted regression (GTWR), the synergistic effects and spatial-temporal heterogeneity of the influencing factors were systematically investigated. The results indicated: (1) The synergistic development levelof pollution reduction, carbon mitigation, vegetation expansion, and economic growth in the YREB exhibited a fluctuating upward trajectory, with the regional collaborative development mechanisms progressively exerting their effects.(2) Four pivotalfactors, including R&D intensity, industrial structure, energy intensity, and foreign investment, collectively established the critical framework for coordinating environmental and economic development in this region. (3) Energy intensity and R&D intensity exerted stronger influences than industrial structure and foreign investment, while downstream regions exhibited more pronounced negative effects from R&D intensity and foreign investment. (4) Region-wide analysis revealed sustained enhancement of R&D intensity effects, an inverted "U" pattern in industrial structure coefficients, unstable energy intensity effects, and underperforming foreign investment contributions.Moving forward, it is recommended that regions leverage their respective resource endowments and development stages, capitalize on their strengths, and enhance cross-regional cooperation mechanisms to comprehensively promote a balanced development between environmental protection and economic growth.

Monitoring the effectiveness of fish passage facilities, evaluation their functions and continuously optimizing and improving them are essential for adaptive management of fish passage facilities and giving full play to their functions. This study synthesizes the reported literature to analyze the current status of effectiveness monitoring for fish passage facilities in the Yangtze River, focusing on three aspects: fish passage facilities carrying out effect monitoring; the time, content and method of monitoring, performance and influencing factors. Four key challenges identified are the monitoring gaps persist across the Yangtze River Basin with incomplete data and insufficient monitoring coverage, non-uniform indicators and technical methods for monitoring and evaluation, limited adoption of intelligent monitoring technologies and data-processing capabilities, and the weak integration of monitoring results into facility optimization and adaptive management. In order to give full play to the role of fish passage facilities in the protection of the Yangtze River, some suggestions on strengthening the effecitiveness monitoring of fish passage facilities in the Yangtze River are put forward, including promoting basin-wide monitoring coverage; establishing a standard technical system for monitoring and evaluation; increasing the development of key technologies for intelligent monitoring; building an intelligent monitoring and evaluation information platform, and strengthening the application of monitoring results in the optimization of fish passage facilities.

Controlling agricultural non-point source pollution (ANPSP) and improving water environment quality can promote the green transformation of agricultural production mode and achieve high-quality economic development.This paper used the unit survey method and equivalent standard pollution load method to calculate the ANPSP emissions of 20 water-receiving cities in the South-to-North Water Diversion Project's Central Route from 2009 to 2021.The spatial- temporal distribution characteristics was analyzed.The driving factors were investigated using the LMDI model.The results showed that: (1) The ANPSP in water-receiving areas decreased by 23%, due to the effective control of livestock breeding pollution of TN and COD emissions.(2)The ANPSP decreased by 8.02%, and the fertilizer pollution attributed to 82.68%; TP was the key pollutant, with an average proportion of 69.01%.The difference of emission of ANPSP showed an expanding trend.The difference among the water-receiving cities in Henan Province was the main source leading to the imbalance of ANPSP .(3) Economic development level and industrial structure effect had a positive effect on ANPSP , while agricultural economic efficiency and non-urbanization showed a negative effect.The effect of pollution intensity on ANPSP changed from positive to negative, and the driving effect of resource endowment showed a large fluctuation.The water-receiving cities should strengthen the prevention and control of ANPSP to promote the high-quality development of the South-to-North Water Diversion Project's Central Route.

The vegetation coverage in the upper reaches of the Yangtze River is crucial for maintaining the ecological balance of the region.The vegetation cover may also significantly impact the inflow and sediment transport processes of the Three Gorges Reservoir.In this study, the methods of Sen+Mann-Kendall trend analysis and partial correlation analysis were used.The data were based on the 250m resolution Normalized Difference Vegetation Index (MOD13Q1 NDVI), annual runoff, sediment load, land use, and meteorological data from the upper reaches of the Yangtze River.This research investigated the spatiotemporal variation characteristics and the driving factors of NDVI in various sub-basins of the upper Yangtze River (including the Jinsha River Basin, Min-Tuo River Basin, Jialing River Basin, Three Gorges Reservoir Area Basin, and Wu River Basin), as well as their impact on the water and sediment inflow processes into the Three Gorges Reservoir.The research findings indicated that: (1) From 2001 to 2022, NDVI exhibited a fluctuating upward trend, with a continuous improvement of vegetation coverage, and a spatial pattern of lower values in the west and higher values in the east.(2) From 2006 to 2022, the runoff did not show a significant upward trend overall, while the sediment load decreased significantly.During this period, the annual runoff in the Three Gorges Reservoir area exhibited a significant upward trend, whereas the sediment load in the Jinsha River Basin decreased notably.(3) The areas driven by land use factors accounted for approximately 43% of the entire study region, followed by precipitation of about 34%.Moreover, NDVI and precipitation exhibited a positive correlation in most basins, with 20% of the area passing the significance test at p < 0.05.(4) Precipitation significantly influenced runoff, and vegetation in most basins showed a negative correlation with sediment load.In the future, vegetation cover should be enhanced, which would help reduce sediment loss.However, the impact of vegetation restoration on the hydrological cycle requires further research.

To elucidate the regulatory effects and mechanisms of carbon source addition on the migration of soil dissolved organic carbon (DOC) in purple soil areas of hilly regions in central Sichuan under heavy rainfall conditions, this study aimed to provide a scientific basis for the effective control of carbon loss in sloping farmland.Taking purple soil sloping farmland as the research object, the study employed a combination of field runoff plots and laboratory analysis.Using chemical fertilizer alone (CK) as the control, six carbon source addition treatments were established: organic fertilizer (T1), compound microbial fertilizer (T2), biochar-cattle manure-mushroom residue compost (T3), corn straw biochar (T4), upgraded organic fertilizer (T5), and organic soil amendment matrix (T6).This study investigated the changes in soil dissolved organic carbon content and spectroscopic characteristics at different slope positions.The results showed that exogenous carbon addition significantly increased the DOC content at different slope positions.The DOC content at the upper slope position increased by 51.53%–61.34% compared to the control group, with the organic fertilizer treatment showing the most significant enhancement effect.At the middle slope position, the DOC content increased by 16.73%–65.86%, with the biochar-cattle manure-mushroom residue compost and upgraded organic fertilizer treatments significantly increasing by 65.86% and 61.81%, respectively, compared to CK.These treatments also exhibited a significant delaying effect on DOC migration to the lower slope.No significant differences in DOC content were observed among treatments at the lower slope position.The degree of DOC aromatization exhibited significant spatial heterogeneity: the biochar-cattle manure-mushroom residue compost treatment increased the DOC aromatization degree by 12.63% at the upper slope position, while the corn straw biochar and organic soil amendment matrix treatments significantly reduced by 10.10% and 16.93%, respectively.At the middle slope position, the DOC aromatization degree generally showed a decreasing trend.At the lower slope position, the biochar-cattle manure-mushroom residue compost treatment demonstrated the best enhancement effect, significantly increasing the DOC aromatization degree compared to the control.The proportions of DOC components were as follows: soluble microbial byproduct-like > humic acid-like > fulvic acid-like > tryptophan-like > tyrosine-like.The humic substances primarily originated from endogenous microbial decomposition processes.The corn straw biochar and biochar-cattle manure-mushroom residue compost treatments significantly increased the humification index by 56.93% and 71.84%, respectively.The application of biochar-cattle manure-mushroom residue compost not only effectively enhanced soil DOC content and aromatization degree, but also significantly delayed its migration along the slope, promoting DOC enrichment at the middle slope position.This approach achieved multiple benefits, including improved soil fertility, delayed carbon migration, and reduced potential pollution risks.