"People-oriented" is the core component in the process of high-quality development.The "bottom-up" demand-side multidimensional goal provides a new perspective for understanding the connotation of urban vitality.An evaluation system of urban vitality from five dimensions of economy, society, space, culture and ecology was constructed in this study.The entropy-TOPSIS model, Theil index, spatial autocorrelation analysis and obstacle degree model were used to explore the evolution law of urban vitality in the Yangtze River Delta (YRD) region from 1996 to 2021.The results showed that: (1) The urban vitality in the YRD was rising steadily.The vitality of cities in the YRD showed a steady upward trend.The economic vitality was found to play a dominant role in the vitality system.(2) The spatial differentiation and agglomeration characteristics of urban vitality were obvious.The vitality of the core city was obviously higher than that of other cities, forming a "Z-shaped" spatial agglomeration area, and the regional urban vitality showed a "core-edge" structure.(3) The classification of urban vitality patterns showed obvious inter-provincial spatial differences.The vitality of Jiangsu province decreased from south to north.Anhui province faced the dilemma of low vitality level, while Zhejiang Province showed high development potential and stability.(4) Spatial, economic and cultural dimensions were identified as the key dimensions affecting urban vitality.The number of mobile Internet users, the number of patent authorization applications and the proportion of tertiary industry in GDP had significant effects on urban vitality.Future urban development strategies should consider multi-dimensional development, strengthen support for core cities, and promote resource flow to promote coordinated development and comprehensive enhancement of vitality within the YRD region.

A reasonable spatial structure is an essential foundation for urban agglomerations to achieve regional economic synergistic development. The use of statistical data to analyze changes in urban agglomerations has problems such as weak presentability and difficulty of data acquisition. To address this problem, this study proposed a method for extracting the built-up areas by using the nighttime light remote sensing data and land use data. Considering the Middle Reaches of Yangtze River Urban Agglomerations (MRYRUA) as a case study, this study presented a two-step method for the spatial-temporal fractal analysis. First, the spatial and temporal evolution characteristics of spatial structure within the urban agglomerations were analyzed on the basis of the results of the built-up areas of the MRYRUA from 1990 to 2020. Furthermore, with the help of fractal theory and the combination of morphological, correlation, and aggregation dimensions, the morphological, correlation, and aggregation characteristics of the spatial structure of the MRYRUA were discussed. It was observed that within the period of 25 a, the MRYRUA exhibited marginal expansion from the center to the surroundings. In contrast, the urban built-up areas within the MRYRUA were distributed along the rivers in a more pronounced strip-like pattern. The results of the morphological dimension indicated that the development of the Wuhan Metropolitan was relatively well-managed, with a stable and orderly expansion of cities. The results of the correlation dimension demonstrated that the structure of the Chang-Zhu-Tan Urban Agglomeration exhibited a higher degree of similarity, suggesting a more effective synergy of development. The aggregation dimension indicated that the intensity of expansion of cities in the Urban Agglomeration around Poyang Lake was inconsistent, suggesting that the core driving role was not yet stable. The findings of this study facilitated the full exploitation of the advantageous geographical position of the MRYRUA, thereby facilitating the balanced and integrated development of neighboring cities across provincial boundaries.

The main contradiction of water security in China has changed from insufficient supply to excessive environmental carrying capacity.The water environmental carrying capacity (WECC) in many regions is in a state of overload or facing the risk of overload, to support sustainable social and economic development.It is an urgent task to explore the strategy of advanced development of regional industrial structure under the constraint of WECC.This study took 11 provincial regions in the Yangtze River Economic Belt (YREB) as an example, and constructed models to investigate the existing problems of WECC and industrial development.The dialectical analysis of the adaptation mechanism of the two was used.A two-dimensional decoupling adaptation model of WECC and advanced industrial structure was constructed.This study aimed to provide important guidance for the formulation of regional differentiated "water-based production" policy.The findings were as follows: (1) The level of WECC in 11 provincial-level regions of the YREB was generally low and did not show a significant improving trend, with the overall spatial distribution characteristics of "downstream > midstream > upstream".The WECC of the YREB varied significantly among provinces and there was no significant spatial autocorrelation.The coupling coordination level among the four subsystems did not restrict the WECC of the YREB.Ecological water consumption rate and industrial structure were the two factors that had the greatest influence on the WECC.(2) The level of advanced industrial structure of provincial areas in the YREB basically showed an upward trend, but the effect of industrial structure upgrading was not significant.There were six two-dimensional decoupling adaptation states between the WECC and advanced industrial structure, and the optimal two-dimensional decoupling adaptation state of "high-adaptation" had not been realized.This study enriched the theory and method of "water-based production" research, and also provided an important decision-making reference for regional differentiated "water-based production" policy formulation and regional regulation of WECC.

The off-site investment of enterprises in the context of flow space injects a strong impetus to the development of urban network, while ecological security affects the formation and structure of industrial investment network. The city cluster around Poyang Lake is a sensitive area of human-land conflict, and the natural ecological background has its uniqueness in the lake area. Taking the city cluster around Poyang Lake as the research area, we applied the research framework of city cluster flow space under the constraint of ecological security. The modified gravity model was used to examine the correlation strength of its industrial investment flow. The social network analysis method was used to explore the spatial correlation network characteristics and driving factors of its industrial investment under the constraint of ecological security. This study found that: ① the spatial network of industrial investment in the city cluster around Poyang Lake under the ecological security constraints had obvious characteristics of "centre-periphery", and the spatial linkage of industrial investment flows was strengthening. The structure of the network was becoming more and more stable; ② a small number of economically more developed regions occupied the centre of the network in the long term, and at the same time played the role of efficient intermediary. There existed the phenomenon of development path breakthrough in the peripheral areas; ③ There was a strong spatial dependence on the plate characteristics of the spatial network of industrial investment in the study area. The cities in the same plate showed the characteristics of embracing and warming up in geographic location; ④ The similarity of the level of opening to the outside world, the level of governmental regulation, the level of urbanisation of the population and the level of urbanisation of the land demonstrated a significant positive influence on the spatial network of industrial investment in the Poyang Lake City Cluster under the constraint of ecological security.

The adaptation of environmental regulations to the green transformation of the tourism industry is a key link in achieving high-quality development of the tourism industry. It is also an inherent requirement for building a modern harmonious coexistence between humans and nature. This article evaluated the adaptability of environmental regulation and green transformation of the tourism industry in the Yangtze River Economic Belt from 2010 to 2022. The methods of kernel density estimation and GTWR model were used to reveal the spatiotemporal dynamic characteristics and the associated influencing factors. The results indicated that: From 2010 to 2022, the formal environmental regulations and green transformation of the tourism industry had undergone an evolution process of "unsuitability relatively adaptation unsuitability", with a degree of dispersion changing from "decrease increase decrease"; From 2010 to 2022, informal environmental regulations and the green transformation of the tourism industry transitioned from being fairly adapted to being relatively adapted, and the differences within the study area were gradually narrowed. In 2010, the formal environmental regulations and green transformation of the tourism industry were mainly incompatible, while in 2016, they were mainly in a better compatible. In 2022, Anhui and Sichuan showed significant "leading" characteristics in relative compatibility; In 2010, there was a significant imbalance in the adaptation of informal environmental regulations to the green transformation of the tourism industry. In 2016, a spatial pattern of "high in the north and low in the south" was roughly formed. In 2022, only Zhejiang and Yunnan were in the stage of adaptation. In the formal environmental regulation and green transformation adaptation system of the tourism industry, the negative impact of urbanization and government regulation increased from upstream to downstream, while economic development and technological innovation mostly had a positive impact on the entire basin; In the adaptation system of informal environmental regulation and green transformation of the tourism industry, urbanization and government regulation had a positive impact on most of the provinces, while technological innovation had an overall negative impact on the adaptability of the entire basin. Financial support had a positive impact only on upstream areas.

River connectivity characterizes material and energy liquidities in the aquatic ecosystem of Yangtze River Delta. The assessment of river connectivity serves as the critical prerequisite for constructing ecological security pattern. In this study, a river connectivity indicator system of Yangtze River Delta was established, which consisted of 12 indicators covering three categories of physical structure, development feature and fractal topology. The kernel principal component analysis (KPCA) was introduced to interpret the nonlinear relationships among the individual connectivity indicators, and to reduce the feature dimensionality of the indicator space. An innovative river connectivity assessment framework was built on the basis of the KPCA method. The proposed assessment framework was applied to evaluate the river connectivity of the North branch basin of Jurong River, a typical small watershed in the Yangtze River Delta. The evolution feature was explored in the past five decades. The results indicated that since 1970, the deviation degree of river connectivity from the near-natural situation (1960) had kept rising to the peak in 2000 and then decreased in 2016. Four key drivers affecting the connectivity of the basin were identified as the water coverage rate, river network complexity, river network density and lacustrine surface area. The loss of tributaries could be the important occurrence mechanism on the degradation of connectivity in the North branch basin of Jurong River.

Water source protection is pivotal to the success of water diversion projects, yet it imposes higher conservation standards on source areas, thereby inevitably constraining economic development. Quantifying the losses in development opportunities due to these protection measures is a big challenge in establishing ecological compensation standards for water source regions. This research introduced a novel approach to estimate the development opportunity losses stemming from water source protection restrictions by comparing the cumulative growth rates of per capita GDP. Shiyan City, located within the water source area of the South-to-North Water Transfer Project, was selected as a case study. By examining the disparity in the cumulative growth of per capita GDP between Shiyan City and Hubei Province from 2006 to 2019, the study calculated the development opportunity losses incurred by Shiyan City due to its water source protection obligations. The findings indicated that Shiyan City′s development opportunity losses initially increased and then plateaued, with an average annual fiscal revenue shortfall of approximately 569 million yuan attributed to the constraints of water source protection. Compared to prevalent methods such as direct per capita GDP comparison, the cumulative growth rate comparison method proposed herein offered a more accurate reflection of actual economic losses and enhanced practicality. This study aimed to provide valuable insights for the assessment of development opportunity losses and the development of ecological compensation frameworks in the water source protection zone and other analogous areas within the South-to-North Water Transfer Project.

Effective ecological management and control zoning is crucial for the scientific formulation of protection and management strategies in key ecological function areas. Using the key ecological function areas of the Xiuhe River Basin as a study area, the spatial-temporal differentiation and spatial correlation characteristics of ecological risk and ecological resilience were comprehensively evaluated and analyzed in this paper. Furthermore, an ecological management and control zoning scheme was developed based on the four-quadrant method. The results indicated that: (1) The study area was primarily characterized by low ecological risk and high ecological resilience. Both ecological risk and resilience displayed a spatial pattern of "low in the north and south, high in the east and central west" for risk, and "low in the north and south, high in the east and west" for resilience, with the main stream of the Xiuhe River serving as the primary axis. Both factors exhibited an increasing trend. (2) The Moran index of ecological risk and resilience in the third phase was -0.597, -0.616 and -0.663, respectively, indicating a significant negative spatial correlation between the two, which increased progressively over time. (3) The study area was divided into four ecological management and control zones, among which the low-risk-high-resilience zone was the main area, accounted for more than 60% of the entire study area, which exhibited an increasing trend, and the rest of the zones exhibited a decreasing trend. The ecological management and control zoning based on the "risk-resilience" approach exhibits scientific validity and operational feasibility, allowing for the development of targeted and differentiated protection and management strategies for key ecological function areas in the Xiuhe River Basin.

The changes in water use structure in Hubei Province are crucial for implementing the "spatial balance" water management strategy and promoting regional water resource allocation. Hubei Province, classified as a region with mild water scarcity, has gradually revealed issues related to the balance of water use structure. This paper analyzed the evolution of water use structure and the spatial distribution characteristics of various water use types in Hubei Province′s cities and prefectures from 2000 to 2022, based on the theories of information entropy and the Lorenz curve. The results indicated an overall upward trend in the total water use, with the proportions of different water use types remaining relatively stable and the system′s balance gradually improving. By 2022, agricultural water use dominated the province′s total water use, with a Gini coefficient of 0.193, which indicated a balanced spatial distribution. Domestic water use showed an increasing trend, which was mainly concentrated in the western and eastern regions, with a Gini coefficient of 0.380, which suggested an increasing spatial distribution disparity. Industrial water use proportion showed a decreasing trend, with a Gini coefficient of 0.299, which indicated an increasingly unbalanced spatial distribution. Ecological and environmental water use increased in recent years, in the areas concentrated in the central region, with a Gini coefficient of 0.543, which indicated a significant and growing spatial distribution disparity. This study provided a reference for future adjustments in industrial structure and water resource optimization in Hubei Province′s cities and prefectures to further promote "spatial balance" development.

The conflict between urbanization and ecological environment protection is a major challenge for sustainable urban development. This study utilized Theil-Sen Median trend analysis and Mann-Kendall significance test to analyze the vegetation change trends in Ganzhou City from 2000 to 2020. Additionally, it explored the spatiotemporal characteristics of the relationship between urban expansion and urban vegetation changes in Ganzhou City using an improved Urban Vegetation Cover Index (UVCI). Finally, based on the Geodetector tool, this study investigated the impact of nine factors, including natural factors and human activities, on the spatiotemporal distribution of UVCI, to reveal the characteristics of the impact mechanisms of the relationship between urban expansion and urban vegetation changes within urban regions, i.e. urban centre area and expanding area. The results indicated that: (1) From 2000 to 2020, the overall vegetation in Ganzhou City showed a fluctuating upward trend, but certain areas (mainly mining regions) still experienced some degree of degradation; (2) The relationship between urban expansion and vegetation changes in Ganzhou City exhibited two periods of change from 2000 to 2020, characterized by a trend towards coordination between 2000 and 2015, and a gradual deterioration of the relationship from 2015 to 2020. This deterioration was more severe in the urban centre areas of each county compared to the expansion areas; (3) Factor detection showed that temperature, precipitation, and GDP were the core driving factors affecting UVCI. As the level of urbanization increased, the impact of human activities in the expanding areas was gradually intensified. In the future, promoting the coordinated development of urban vegetation and urban expansion in Ganzhou City requires a comprehensive consideration of various factors and the formulation of differentiated strategies to achieve the goals of ecological civilization construction and sustainable urban development.

The vegetation distribution map shows the growth state of the vegetation population and is an important indicator for assessing the quality of local ecology. In order to protect the environment, it is very important to explore the vegetation changes in the Huaihe ecological economic belt and the associated climate drivers. Based on time series data and normalised vegetation index (NDVI) meteorological data from 2000 to 2020, this study analyzed the spatio-temporal trends and abrupt changes of climate in the Huaihe River Ecological Economic Belt. Using wavelet analysis, spatial autocorrelation analysis, Sen+Mann-Kendal trend analysis, partial correlation analysis and geographical detector, this paper studied the spatio-temporal evolution of vegetation coverage in Huaihe River ecological economic Belt. The results showed that: (1) From 2000 to 2020, the vegetation area demonstrated a variable growth trend, with the average annual vegetation area of 0.754 and a reduction from southwest to east. (2) The vegetation cover level was relatively high on the whole, and the vegetation cover improvement area was larger than the degraded area in the three different stages from 2000 to 2010, 2010 to 2020 and 2000 to 2020, accounting for 89%, 44.25% and 71.6%, respectively. It was mainly distributed in Xinyang City and Zhumadian City of Henan Province, northern Anhui Province and northern Jiangsu Province. (3) The climate environment in the study area showed a gradual tend to warm and humid between 21a and 21a. The positive correlation between vegetation coverage and precipitation was higher than between relative humidity, temperature and solar radiation. The partial correlation between vegetation coverage and climate factors varied significantly between the regions. (4) The interaction of each driving factor in the region was significantly higher than that of a single driving factor, and most of them showed a nonlinear enhancement trend. The interaction of precipitation was the largest.

Figuring out the relationship between the soil pH value and the medium/trace elements of citrus orchards in the soil-leaf-fruit system is of great significance for the acidification improvement, nutrient regulation, and fruit quality improvement in citrus orchards. In this study, 362 groups of citrus soil-leaf-fruit samples were collected and measured in six provinces of Hubei, Hunan, Jiangxi, Fujian, Guangdong and Yunnan. The characteristics of pH distribution, medium/trace element content and their relationship in citrus soils were investigated by using gray correlation, correlation and multiple linear regression analysis. The results showed that: (1)The average soil pH value of citrus orchard was 4.92 (acidic), and the coefficient of variation was 14.52%, which was a small variation. There were 213 and 92 acidic and strongly acidic citrus soil sample points, respectively, indicating that more than half (84.25%) of the soil sample points were in a state of excessive acidity, which was not conducive to the growth of citrus. (2) The content of available Fe, available Mn, available Ca, available Mg, available S, FeLeaves, MnLeaves, CuLeaves, ZnLeaves, CaLeaves, MgLeaves, BLeaves, SLeaves, FeFruits, MnFruits, CuFruits, ZnFruits, CaFruits, MgFruits, BFruits, SFruits with different soil pH gradations (highly acidic, acidity, faintly acidic, neutral, alkalinity) were significantly different (p<0.05). (3)The pH value of citrus soil had the highest correlation coefficients with the contents of MgFruits, MgLeaves and CaFruits, which were 0.850, 0.814 and 0.775, respectively, while the lowest correlation coefficients with the contents of MnFruits (0.629), CuFruits (0.627) and CuLeaves (0.624). The highest correlation coefficient between medium/trace elements in the available state of the soil and the soil pH value was available B (0.727) and the lowest was available Fe (0.670). The highest correlation coefficient between medium/trace elements in leaves and the soil pH value was MgLeaves (0.814) and the lowest was CuLeaves (0.624). The highest correlation coefficient between medium/trace elements in fruits and the soil pH value was MgFruits (0.850) and the lowest was CuFruits (0.627).(4) Prediction based on soil pH and medium/trace element content showed that MnFruits, CaFruits, and SFruits were affected by the corresponding leaf element content leading to the highest degree of explanation, 0.79, 0.56, and 0.56, respectively. In summary, there was a need for the citrus orchard soils to be scientifically rationalized to regulate soil pH and to balance the content of medium/trace element in order to improve the quality of citrus fruits.

The Yangtze River Basin has an important strategic position in China's ecological security pattern and socioeconomic development. However, there exists a lack of long-term monitoring studies on the ecological environment quality in the Yangtze River Basin. In order to explore the spatial and temporal changes of the ecological quality of the Yangtze River Basin, this study utilized Google Earth Engine (GEE) and selected Landsat remote sensing images of the growing season (May-September) from 1990 to 2020. The Remote Sensing Ecological Index (RSEI) was calculated, and the GeoDetector was used for factor analysis. The results indicated: (1) The average contribution rate of humidity, greenness, dryness, and heat on the first principal component was 85.49%, and the average correlation of RSEI was higher than other single indicators. This validated the feasibility of constructing RESI based on the first principal component in the Yangtze River Basin. (2) From 1990 to 2020, the overall ecological environment quality remained at a good level, showing a slow upward trend of decreasing and then increasing. The ecological quality in the middle and lower reaches generally was higher than that in the upper reaches, and the ecological quality in the southern part was higher than that in the northern part. From 1990 to 2005, areas of mild deterioration were relatively scattered. While from 2005 to 2020, areas of mild improvement were mainly concentrated in the Jinsha River Basin, Dongting Lake Basin, and Poyang Lake Basin, and the areas of minor changes were mainly distributed in the central region. (3) The main driving factors were altitude, average temperature and annual precipitation. The results of multi-factor detection showed a synergistic enhancement effect among these factors. (4) Among different land use types, the RSEI value of forest land was the highest, while that of bare land was the lowest. At the county scale, the proportion of forest land had the highest correlation with RSEI and had a positive effect on RSEI, with an average correlation of 0.69; The proportion of impervious surface, population density, and economic density had negative effects on RSEI, with average correlations of -0.39, -0.43, and -0.45, respectively. These findings provided important theoretical and technical support for the ecological environment protection and development of the Yangtze River Basin.

The Yangtze River Delta (YRD) is the region with the highest level of economic and social development and the most active region in China. Analyses of the spatial and temporal characteristics of the carbon emissions and the associated affecting factors can provide important references for other regions of China. This study employed spatial autocorrelation analysis and standard deviation ellipse, based on nighttime lighting data from 41 cities in the YRD region from 2006 to 2021, to analyse the spatial and temporal characteristics of carbon emissions. Furthermore, this study used the geographically and temporally weighted regression (GTWR) model to empirically examine the spatial and temporal heterogeneity of the factors influencing carbon emissions in the YRD region. The findings indicated that: (1) The data demonstrated a clear upward trajectory in carbon emissions in the YRD region from 2006 to 2021, with evidence of significant spatial positive autocorrelation. The junction zone of Jiangsu, Zhejiang and Shanghai in the eastern part of the YRD exhibited a high-high agglomeration, whereas the low-low agglomeration area was predominantly situated in the western part of the YRD within Anhui Province. (2) The standard deviation ellipse results indicated that the growth of carbon emissions was more pronounced in the western part of the YRD, with a tendency for the centre of gravity of shifting towards the west. (3) Environmental regulations, greening level, R&D investment and low-carbon pilot policies exerted a negative inhibitory effect on carbon emissions, whereas population size, economic level, industrial structure and openness to the outside world exerted a positive promotional effect. Furthermore, the impact of each factor on carbon emissions in the YRD region exhibited spatial and temporal differences. These results may provide valuable references for the development of differentiated carbon emission reduction strategies in the YRD region.

In the context of urban river ecological environment governance, a new paradigm of "diversified" governance entities has emerged. The market and social stakeholders are involved in this new paradigm. However, these multiple stakeholders have not yet reached an optimal state of co-governance. Exploring the determinants of multi-stakeholder co-governance can help overcome the operational dilemmas of this governance model and improve the urban river ecological environment governance system. From the perspective of dynamic governance, the collaborative process of multi-stakeholder co-governance in urban river ecological environment is divided into two stages: "formation" and "maintenance". Based on the SFIC model, a theoretical model of the influencing factors for multi-stakeholder participation in urban river ecological environment governance was constructed in this study. Using questionnaire survey data from the Yangtze River Delta region and employing Partial Least Squares Structural Equation Modeling (PLS-SEM) and Fuzzy-Set Qualitative Comparative Analysis (fsQCA), an empirical analysis of the pathways and configurations of influencing factors was performed in this paper. The research findings indicated: (1) in the "formation" stage of multi-stakeholder co-governance relationships, trust among stakeholders, market cooperation, social cooperation, and environmental information disclosure had a significant positive impact on multi-stakeholder participation in urban river ecological environment governance. Meanwhile, expected returns, governance capacity, market cooperation, and environmental information disclosure had a significant positive effect on the "maintenance" of multi-stakeholder co-governance relationships. (2) Trust among stakeholders, high governance capacity, expected returns, market cooperation, social cooperation, and environmental information disclosure could not individually serve as necessary conditions for the "formation" and "maintenance" of multi-stakeholder co-governance in urban river ecological environment. There was a need to consider their combined effects with other factors in exploring the way these factors exerted influence. (3) There were 4 equivalent causal paths that promoted the formation of multi-stakeholder co-governance in urban river ecological environment and 3 equivalent causal paths that promoted its maintenance. The effective combination of multiple factors promoted the development of multi-stakeholder co-governance in urban river ecological environment in a "different paths, same destination" manner. The research findings provided decision-making references for the sustainable governance of urban river ecological environments.

In the context of global climate change, enhancing forest carbon sink capacity is a crucial measure to mitigate global warming. This study proposed a tree species planning strategy for arboreal forest land based on carbon sink objectives. Taking Sanfengsi Town, Huarong County, Yueyang City in Hunan Province as a case study, a BP neural network was used to construct growth models for tree species (or species groups) suited to the local environment. This was to enable a comprehensive analysis of the carbon sink potential of different species across various forest plots. Additionally, the D-ANP method was applied to evaluate the afforestation suitability of 1862 forest plots by integrating factors such as land use, transportation accessibility, and forest quality, which helped to establish an appropriate sequence for species replacement. The results indicated that: (1) There were significant differences in the carbon sink capacities of different tree species (or species groups). In monoculture afforestation, Cedrela, Liquidambar, and Phoebe exhibited strong carbon sink potential, contributing 202242 tCO2e, 184669 tCO2e, and 177884 tCO2e, respectively. In contrast, Cupressus and Quercus contributed a lower value of 95386 tCO2e and 74527 tCO2e, respectively. (2) Optimization of tree species configurations could significantly increase the overall regional carbon sink. Through scientific tree species planning, the carbon sink potential of the study area for the period of 2021-2041 could be increased from the originally projected value of 116924 tCO2e to 259590 tCO2e, which was an increase to 222.01% of the original one. (3) A comprehensive multi-factor analysis supported the stable growth of the carbon sink. The phased planning of tree species replacement ensured a smooth transition in carbon sink capacity, especially for the case of the replacement of low-efficiency species by the high-efficiency species. These findings provided valuable reference and practical guidance for tree species planning and management in arboreal forest lands, with a potential broad applicability.

Dongjiang Lake is a critical drinking water source in Hunan Province. The total phosphorus and ammonia nitrogen concentrations in Dongjiang Lake are rising, which causes that the water quality is on the critical line of cross-decline. However, the surface source pollution of Dongjiang Lake has a complex pathway into the lake. The existing water quality monitoring sections are not able to comprehensively reflect the water quality status of all rivers entering the lake. In this study, a surface source pollution model was developed based on the SWAT model. The model was used to identify the sources of pollution and to estimate the loads of surface source pollution in the basin. The reduction rate of different measures was also evaluated. The simulation results showed that the high loads nitrogen and phosphorus was located in the eastern part of the basin and the Guangqiao River, Tianzhuang River and Changwu River. The low loads of pollution was located in the middle part of the basin. The pollution source in the basin was dominated by urban life and agricultural fertilization. Based on the in-depth investigation of the current situation of surface source pollution management in the Dongjiang Lake watershed, specific reduction measures were proposed nted for urban living and agricultural fertilization pollution. The effects of these measures were evaluated in the model. The simulation results showed that the effects of the five management measures were, in a descending order, stubble mulching > contour farming > livestock farming > reduction of fertilizer application > urban life. A comparison with the actual water quality changes proved that the established model was applicable to the simulation of pollution reduction measures in Dongjiang Lake Basin. However, it should be noted that the risk of endogenous pollution still existed in the inlet of Dongjiang Lake. This study aimed to provide theoretical basis and data support for the control of exogenous nitrogen and phosphorus inputs towards a better management of water quality of the basin.

Study on the resilience of the agricultural products supply chain in the Yangtze River Economic Belt (YREB) is conducive to the optimization of the regional industrial layout. It is also of great significance to realize "Chinese modernization" and to build a new pattern of regional agricultural products supply chain development. Combined with the five characteristics of Chinese modernization, this study constructed a comprehensive evaluation index system for the resilience level of agricultural products supply chain in the YREB. The regional differences, temporal and spatial evolution and obstacle factors of the resilience were explored, for 2012-2022. The entropy method, Dagum Gini coefficient, Markov chain method, kernel density estimation and obstacle degree model were used. The main conclusions were as follows: (1) The resilience level showed a sustained growth trend for the studied period, with significant differences showing a decreasing trend in resilience levels among provinces and cities. The resilience level in various regions showed an obvious regional imbalance pattern. (2) The overall differences were mainly due to regional differences, and the contribution rate of regional differences was generally decreasing. (3) The resilience level in various provinces and cities demonstrated a strong stability, and the radiation effect of high-level provinces and cities was significant. (4) There was a severe imbalance and polarization in the regional development. (5) Local financial support, full-time equivalent of local R&D personnel and the proportion of agricultural product imports and exports were found to be the  the main obstacles that affected the resilience level. The full-time equivalent of local R&D personnel, the proportion of agricultural products import and export and the intensity of the fixed assets investment of agricultural products were the highest proportion among the barrier factors of upstream, midstream and downstream provinces and cities, respectively.

Food security is a crucial pillar for maintaining national stability and long-term peace, and increasing the multiple cropping index is an effective approach to tapping the potential of arable land and enhancing food production capacity. This study optimized the suitability evaluation factor system for double-cropping rice in paddy fields. The methods of the evaluation and constraint factor analysis, multi-factor weighted evaluation model, and a four-quadrant approach were employed to conduct a comprehensive suitability evaluation and spatial optimization for double-cropping rice cultivation in Hunan Province. The results indicated that: (1) The overall suitability for double-cropping rice cultivation was relatively high, with the majority of suitable areas classified as moderate to high suitability zones. Specifically, the proportions of high, moderate, low, and unsuitable suitability areas were calculated as 31.05%, 35.83%, 20.00%, and 13.12%, respectively. This implied that most regions had favorable conditions for double-cropping rice cultivation. (2) In 2020, there was an additional potential area of 2540.07 thousand hectares for double-cropping rice cultivation in Hunan Province, which accounted for 51.68% of the total suitable paddy field area. Among these, the potential increase in rice yield was 5.31 million tons, representing 20.13% of the total rice production in Hunan Province in 2020, which indicated the substantial potential for yield enhancement. (3) Based on a comprehensive analysis of current farming conditions and suitability evaluation results, Hunan Province is divided into four optimization zones for double-cropping rice cultivation structure, i.e. the key protection areas, the priority remediation areas, the status quo protection areas, and the structural adjustment areas. The number of counties corresponding to each optimization zone was 32, 42, 21 and 27, respectively. It was recommended to implement differentiated governance and management measures for each zone to maximize the utilization of regional resources and potential, to ensure sustainable agricultural development. The findings of this study provided scientific support for the formulation and implementation of differentiated rice planting subsidy policies in Hunan Province. Additionally, they offered strategic guidance for optimizing the double-cropping rice cultivation structure, to enhance the multiple cropping index, and to ensure regional food security. Implementing these measures would enhance the utilization of valuable arable resources, boost food production capacity, and contribute to both national food security and high-quality agricultural development.