Promoting the green and low-carbon transformation of the economy is the inevitable requirement of implementing Xi’s ecological civilization thought in the new era. Green technology innovation is the core support to achieve the “double carbon” goal, but the academic community is still lack of in-depth discussion on the impact of green technology innovation on carbon emissions and its spatial effect in developing countries.Based on the panel data of 110 cities in the Yangtze River economic belt from 2006 to 2020, the spatial effect of green technology innovation on carbon emissions is studied by using GIS spatial analysis and spatial econometric model. The results show that: (1) from 2006 to 2020, the spatial distribution of green technology innovation and carbon emissions in the cities of the Yangtze River economic belt is unbalanced, and the spatial polarization of green technology innovation is significant. The innovation pattern dominated by the core cities in the Yangtze River Delta and promoted by the capital cities in the central and western regions is increasingly prominent, and the high-carbon regions are distributed in the downstream regions and scattered in the upper and middle regions; There is a significant positive spatial correlation between green technology innovation and carbon emissions, and the evolution of spatial agglomeration shows spatial lock-in and path dependence. (2) The impact of green technology innovation on carbon emissions shows a significant “U” shaped relationship, and the spatial spillover effect shows an inverted “U” shaped opposite relationship, reflecting the “rebound effect” and “polarization trickle down” effect of technological innovation. (3) Heterogeneity analysis shows that compared with resource-based cities, the carbon emission reduction effect of green technology innovation in non resource-based cities is stronger, while the carbon emission increase effect is weaker; The impact of green technology innovation in upstream cities on carbon emissions is mainly reflected in the short term, with the direct effect of “U” type and the indirect effect of “inverted U” type. The impact of green technology innovation in midstream cities is mainly reflected in the long term, with the direct effect and indirect effect of “inverted U” type. The impact of downstream cities is not significant in both the short term and the long term.

Under the dual goals of achieving economic growth and carbon emission reduction in China, the new digital infrastructure provides a new opportunity and a practical path for improving regional carbon productivity. Based on the latest and available panel data of 108 cities in the Yangtze River Economic Belt (YREB) from 2009 to 2019, the paper used kernel density estimation model, spatial durbin model, mediation effect model to explore the spatial evolution trend of the new digital infrastructure and carbon productivity. The impact and transmission mechanism between the new digital infrastructure and carbon productivity was also explored. The results were as follows: (1) The development level of the new digital infrastructure and the level of carbon productivity in the YREB showed a spatial differentiation, with an evolution trend of spatial mismatch. (2) The new digital infrastructure significantly improved carbon productivity, which was still valid after a series of robustness tests. (3) The new digital infrastructure could improve carbon productivity by promoting green technological innovation. The influence of the new digital infrastructure on carbon productivity showed an obvious spatial spillover effect. (4) The heterogeneity analysis showed that the positive promoting effect was more significant in non-resource cities and Chengdu-Chongqing urban agglomerations. These conclusions may provide new empirical evidence for promoting the realization of the“carbon neutral”goal towards a high-quality urban development.

High-quality development of the Yangtze River Economic Belt with the promotion of comprehensive economic strength as the core is the key to achieve a new era of regional coordination pattern. Based on this, a regional economic comprehensive level measurement system was constructed in this paper. The spatiotemporal evolution characteristics and the driving mechanisms of the regional economic comprehensive level of the Yangtze River Economic Belt were analyzed from a multi-scale and multi-mechanism perspective from 2001 to 2020. The results indicated that: (1) Regional economic differences showed a fluctuating downward trend, with scale differences of provincial-level>prefecture level>district level, which indicated a significant imbalance in regional economic development at the provincial level. Internal development at the prefecture level was shown as relatively balanced. (2) The development of regional economy showed a positive agglomeration feature, with obvious regional scale effects and strong spatial correlation pattern stability. There was a circular hot and cold point agglomeration distribution from downstream to upstream; The spatial classification was mainly based on low to medium level areas, with a distribution pattern of planar agglomeration and point inlay from low to high levels; Path dependent was the subject of spatial evolution. (3) The spatial differentiation of regional economy was obvious, exhibiting agglomeration characteristics. The development level of coastal and riverside cities was relatively high; In term of clustering characteristics, urban agglomerations had a higher development; In terms of hierarchical characteristics, the higher administrative level of a city had a better development; In term of functional characteristics, comprehensive cities were superior to resource-based cities; In terms of stepped features, the eastern cities were superior to the central and western regions. (4) Multiple factors of location, economy, society, and politics acted together in influencing the spatiotemporal evolution of regional economic differences at different spatial scales. (5) The high-quality development of the economic belt economy should resolve issues of making systematic improvement to promote overall regional development, implementing economic belt strategy to promote regional spatial coordination, and strengthening regional policies to promote high-quality development.

The upper reaches of the Yangtze River is an important region supporting China's hinterland economy. At the stage of the synergistic development of high-quality economic development and ecological environmental protection, industrial ecological agglomeration is an important path for industrial transformation. On the basis of the connotation of industrial ecological agglomeration, this paper constructed the industrial ecological agglomeration index system from three dimensions of industrial scale agglomeration, innovative agglomeration, and green agglomeration. Based on the panel data of 33 cities in the upper Yangtze River region from 2009 to 2019, the improved entropy method and geographical detector were used to analyze the spatial difference characteristics and associated driving factors of industrial ecological agglomeration. The spatial econometric model was used to explore the spatial spillover effects. The results showed that: (1) The industrial ecological agglomeration level in the study area increased year by year, with a distribution characteristics of "center-periphery" gradient and decreasing diffusion, and presented a spatial pattern of "high in the northeast region and low in the southwest region". (2) Most of the driving factors in the industrial ecological agglomeration system passed the significance test. The strength of the driving forces from stronger to weaker was in the order of industrial innovation agglomeration factor > industrial scale agglomeration factor > industrial green agglomeration factor. Among them, the strength of the influence of industrial green agglomeration factor was much lower than that of industrial scale and innovation agglomeration factor. (3) The interaction between different driving factors in the industrial ecological agglomeration system showed an enhanced relationship. The interaction results of the two-factor enhanced relationship were more abundant than those of the nonlinear enhanced relationship. (4) There was a spatial spillover effect of industrial ecological agglomeration in the upper reaches of the Yangtze River. The environmental regulation, informatization level, social security level and transportation infrastructure construction were shown to have significant driving effects,  and the industrial structure and social security level demonstrated exogenous interaction effects.

Ecological resilience is the ability of the ecological environment to resist, recover and adapt to uncertainty. Urbanization is prone to lead to a series of ecological and environmental problems. Balance of urbanization and ecological resilience is the key point that should be considered in achieving sustainable development and ecological preservation. In this paper, a 4-dimensional ecological resilience evaluation index system of urbanization and ecological risk, resistance, adaptation and recovery was constructed. The coupling coordination degree model and coordination influence index were used to calculate the coupling coordination degree of urbanization and ecological resilience in the Three Gorges Reservoir Area from 2000 to 2020. The spatial-temporal evolution pattern was further analyzed. The results showed that: (1) during the study period, the urbanization level of the Three Gorges Reservoir area showed a fluctuating upward trend, indicating a decreasing distribution pattern from southwest to northeast; The level of ecological resilience also showed an upward trend, and demonstrated the spatial distribution characteristics of "misalignment" with the level of urbanization. (2) The coupling and coordination degree of all districts (county) remained basically unchanged, mainly at the stage of "slight imbalance", "impending imbalance", "reluctant coordinated" or "intermediate coordination", most of which showed uncoordinated types of lagging ecological resilience or being hindered from urbanization. There was spatial heterogeneity in space, showing a three-region vertical distribution pattern of "northeast-southwest direction". (3) The effects of different ecological resilience subsystems on the coordination degree of urbanization and ecological resilience were different. Ecological risk, adaptation and recovery index generally hindered the overall coupling coordination degree, while the ecological resistance index generally promoted the overall coupling coordination degree, and its intensity was stable throughout the year. In the future, paths of leading coordinated regional development by new urbanization, improving ecological resilience by reasonably distributing urban green space, establishing a nature reserve system, and protecting key areas of ecological diversity were suggested for the coordinated and sustainable development of urbanization and ecological resilience in the Three Gorges Reservoir Area.

Green urbanization is an inevitable choice for China to deeply promote the new type of urbanization and ecological civilization; Rocky desertification is the key factor restricting the social and economic development of karst area in southwest China. It is of great practical significance for the new type of urbanization and regional coordinated development of China to deeply analyze the coupling coordination relationship between green urbanization and the evolution of rocky desertification, and to explore their interactive promotion mechanism. This paper measured the coupling coordination level of green urbanization and rocky desertification at the county scale, analyzed the spatial pattern characteristics, and identified the main obstacle factors. The coupling coordination model, GIS spatial analysis and obstacle degree model were used. The results showed that: (1) During 2015-2020, the coupling coordination level of green urbanization and rocky desertification in the study area was generally low. (2) The order of spatial pattern of coupling coordination was central > eastern > western. HH cluster counties were mostly concentrated in Guiyang and expanded to the north. The LL cluster counties were mainly distributed in the west of Guizhou. (3) During the study period, the coupling coordination degree of a line from Daozhen County to Ceheng County increased significantly, and decreased to the southeast and northwest. (4) The obstacle factors of the coupling coordination degree mainly came from the green urbanization system, and the influence of the rocky desertification system was gradually decreasing. The eastern part of Guizhou Province was greatly affected by the green urbanization system. The western part and Daozhen county - Ceheng County were greatly affected by the rocky desertification evolution system. (5) The organic integration of green urbanization construction and rocky desertification control should be strengthened in southwest karst area. According to the main obstacle factors of each county, it was suggested that the differentiated coupling and coordinated development path be explored, to achieve the high-level coupling and coordinated development of green urbanization and rocky desertification.

The extreme weather caused by the global greenhouse effect results in substantial losses in agricultural production. Consequently, the reduction of agricultural carbon emission intensity has emerged as a prominent subject of interest among governments and academia worldwide. This paper explored the effects of agricultural socialized service pilot policies on carbon emission reduction, impacting mechanisms, and the heterogeneity. This paper analyzed these aspects from the perspective of policy effects, by using the difference-in-difference method and other relevant methodologies. The findings of the study suggested that: (1) The implementation of pilot policies for agricultural socialized services was found to have a sustained inhibitory effect on the intensity of agricultural carbon emissions, leading to successful reduction of carbon reduction in agricultural sector. After a series of robustness tests, the results of the model remained robust. (2) The implementation of pilot policies for agricultural socialized services could indirectly reduce the intensity of agricultural carbon emissions. This could be accomplished by reducing the intensity of fertilizer application, facilitating land transfer, and promoting the adjustment of planting structure towards grain orientation. (3) The carbon reduction effect of the pilot policy for agricultural socialized services exhibited a spatial heterogeneity. The policy demonstrated a larger carbon reduction effect in areas of higher agricultural carbon emission intensity, major grain producing areas, and non-western areas. Therefore, in order to effectively reduce the intensity of agricultural carbon emissions, it is necessary to steadily promote land transfer, accelerate the establishment of a sound agricultural production socialization service system, increase policy support and build incentive mechanisms, respond adequately to the fertilizer and pesticide reduction action, and improve the service of agricultural green socialization.

In order to screen and rationally allocate pioneer plants suitable for vegetation restoration in the riparian zone of the lower reaches of the Yangtze River, the dominant herbaceous plants (importance values greater than 1% and ranking in the top 20) in the riparian zone of the Nanjing section of the Yangtze River were used for this study. Niche measurement, variance ratio (VR), χ2 test, association coefficient (AC), Pearson's correlation test, Spearman's rank correlation test and M. Gordon's stability analysis were employed to analyze the niche and interspecific relationships among 20 species, and ecological species groups were classified. The results showed that: (1) A total of 179 species of plants belonging to 36 families and 113 genera were recorded, among which Artemisia caruifolia, Phragmites australis, Leonurus japonicus, Phalaris arundinacea, Cnidium monnieri, Potentilla supina, Hemisteptia lyrate and Rumex dentatus had larger importance values and niche widths, holding the absolute advantage. (2) The ecotope overlap and similarity among dominant plants were in a moderate degree, with mean values of 0.54 and 0.48, respectively. (3) The overall dominant plants were significantly positively linked. The community stability analysis results showed that the community was currently in an unstable state. In addition, four tests (χ2, AC, Pearson and Spearman) all showed that the positive and negative association (correlation) ratios between dominant species pairs were greater than 1, and the number of non-significantly associated pairs accounted for the majority of the species. In summary, the dominant herbaceous plant communities in the riparian zone of the Nanjing section of the Yangtze River were generally in a dynamic process of positive succession, and the interspecific relationships were loose, with most species tending to share the environmental resources in the riparian zone. In conclusion, the above eight dominant herbaceous plant species were recommended as the pioneer species. According to the divided ecological species group, the simulation of configuration test was suggested to carry out along the corresponding riparian zone space, so as to construct a stable suitable plant community in the riparian zone.

Based on the settlement hierarchy distribution framework of "town-village-historical block", we comprehensively used GIS spatial analysis and geographical detector methods to compare and analyze the spatial characteristics of 421 settlements at different levels in the Grand Canal cultural belt in Jiangsu and Zhejiang Province. We also analyzed the influencing factors from three dimensions of natural geography, human society and canal basin. The results showed that: (1) The distribution of settlements cultural heritage was clustered on the whole, and the smaller the scale of the settlements, the more significant the aggregation of the settlements. However, there was a random or discrete distribution in the city area and the distribution of settlements in each city was uneven. (2) The high-density areas of settlements cultural heritage were located in Hangzhou, Ningbo and Tai Lake area of Suzhou, and there were differences among different types of settlements density areas. (3) The spatial distribution characteristics of settlements cultural heritage were the result of multiple factors, among which the Grand Canal had the greatest influence on the spatial distribution characteristics of settlements. Under the influence of physical geography and canal basin, the overall settlements had low altitude directivity, low slope directivity and adjacent canal directivity, but no obvious exposure directivity. Under the influence of human society factors, the overall settlements tended to be in areas with low traffic accessibility, small population, far away from the city center, and relatively slow economic development. There were differences in various settlements under different influences. (4) Due to the different terrains in the eastern Zhejiang Canal cultural belt, village settlements demonstrated a mountain-oriented, but large-scale settlements were more likely to form near water, rather than near mountain. Based on this, relevant suggestions were put forward to further improve the study of the spatial distribution of settlements cultural heritage in the Grand Canal cultural belt and provide scientific reference and realistic basis for the protection, utilization and inheritance of the Grand Canal culture.

Arable land contributes to both carbon emission and absorption, and thus plays a significant role in achieving carbon peak and carbon neutrality ("dual carbon") goals.  Using the emission coefficient method, gravity transfer analysis and geographically weighted regression (GWR) analysis, we investigated the spatio-temporal variations in the carbon effects of arable land changes in Jiangsu province over the past 30 years.  We found that: (1) The majority of the region exhibited an overall carbon absorption effect in terms of net carbon emissions over the 30-year period.  In comparison to southern Jiangsu, the carbon absorption effect was relatively higher in northern and central Jiangsu.  All counties demonstrated a decrease in the net carbon emission of arable land inflows, with northern Jiangsu experiencing a pronounced decline compared to southern Jiangsu.  Conversely, an increase in net carbon emission increment was observed for arable land outflows in all counties, with central and northern Jiangsu witnessing a faster annual increase.  The overall carbon sequestration of arable land was higher in coastal and southern regions, while lower in other counties.  (2) An increase in economics led to an intensification of arable land carbon emissions, while the secondary and tertiary industry GDP contributed negatively across the region.  The increase of urban and industrial land use imposed the greatest positive contribution to the intensity of carbon emissions.  Rural land use also exhibited a positive effect.  The contribution of transportation location factors varied across different regions, whereas elevation, vegetation, and water-related factors revealed a positive contribution.  Conversely, slope exhibited a negative contribution, and the distance to geological hazards also had negative contributions in most regions.  This study revealed the spatio-temporal variations in the carbon emission contribution and the associated driving forces of arable land changes.  Based on this, relevant policy recommendations were proposed from the perspective of land resource management to promote Jiangsu Province in achieving the "dual carbon" goals.  These results provided scientific decision support for formulating corresponding strategies to reduce carbon emissions and to increase carbon sequestration.  This study might also serve as a methodological reference for relevant studies in other regions. 

The ecological compensation mechanism of Xin'an River basin is a property rights innovation that introduces market mechanisms into local environmental collaborative governance. The basin ecological compensation policy promotes ecosystem services and enhances green water resources utilization efficiency to become an important focus of current ecological civilization construction. This paper used panel data of 27 prefecture-level cities in Anhui Province and Zhejiang Province from 2007 to 2020 to construct an evaluation index system for green water resources utilization efficiency for Xin'an River basin. The effects of ecological compensation on green water resources utilization efficiency was empirically tested, by comprehensively using the super-efficient SBM model and differences-in-differences method. The study found that the policy significantly contributed to the improvement of green water resources utilization efficiency in the pilot area, and this conclusion still held after a series of robustness tests. Moreover, the policy was observed to have little effect in the upstream area, but a significant effect in the downstream area, and the positive effect became larger and larger with time. In terms of the influential mechanism, the policy would promote the green water resources utilization efficiency through the path of scientific and technological innovation. A number of suggestions were proposed in this paper. These included the in-depth promotion of basin ecological compensation policy, the encouragement of building a dynamic cooperation mechanism in upstream and downstream areas, the increase of scientific and technological innovation and a strong interactions with other supporting policies to support the overall sustainable development of the basin.

Spatial distribution modelling of invasive species is crucial for deepening the understanding, predicting, and managing of biological invasions, in order to provide a scientific foundation to effectively address this challenge.In doing so, providing reliable pseudo-absence species (negative samples) is one of the core components of spatial distribution modelling of invasive species.Based on 124 invasive samples of Canada goldenrod (Solidago canadensis L.) and 11 climate variable datasets within the Yangtze River Economic Belt, this study employed cosine similarity to calculate the association between candidate negative samples and invasive species.The Getis-Ord Gi* statistical method was integrated to generate z-score variables for measuring spatial autocorrelation.A framework for identifying pseudo-absence samples of invasive species, by considering climate similarity and spatial correlation, was constructed to reveal potential suitable areas for invasive species.The results indicated that: (1) Compared to previous studies, the pseudo-absence samples generation method presented in this study demonstrated a superior performance in model prediction, feasibility and effectiveness.(2) The pseudo-absence sample sampling strategy helped address the challenge of potential invasive points that might be mis-sampled due to random sampling.This sampling strategy was able to identify suitable areas for invasive species of different levels.(3) Apart from the northwest part of Sichuan Province, most areas within the Yangtze River Economic Belt were suitable for the growth of Canada goldenrod, especially in Shanghai, Jiangsu, Zhejiang, and Anhui.Therefore, it was necessary to pay focused attention, and to actively share experiences of joint prevention and control measures.

Human activity is an important cause of ecosystem service value change. It is important to analyze the spatial and temporal evolution characteristics and the coupling relationship to achieve the harmonious development of human-land relationship. Taking the Yangtze River Economic Belt (YREB) as an example, a comprehensive index system was established to quantify the human activity intensity, based on the land use data of 2000, 2010 and 2020. (HAI) and Ecosystem Service value (ESV) were calculated using equivalent factor method. Based on the relationship between the two, a four-quadrant model was used to divide ecological quality zones. The results showed that: (1) HAI was mainly in the range of low to lower intensity, showing a significant spatial differentiation. The high-intensity areas were distributed in patches in the lower reaches of the Yangtze River and in the provincial capitals. The low-intensity areas were mainly located in the central, southeastern and northwestern regions of the study area, with an expansion of area. (2) In the past 20 years,the overall ESV of the YREB showed a decreasing trend, with a total reduction of 40.975 billion yuan; The high-value ESV areas were concentrated in the municipalities in the lake wetlands and the surrounding areas in the middle and lower reaches of the Yangtze River. The low-value areas were mainly distributed in the cities in northern Jiangsu and northern Anhui, where construction land and arable land were concentrated. (3) The overall ecological quality of the study area was good, with 95 per cent of the counties in the areas of excellent, fair and good ecological quality. The ecological quality has shown a downward trend from 2000 to 2020. The study provided a reference basis for the refined management of regional ecosystems towards a rational protection and restoration of ecological environment.

As an important strategic and demonstration area for national development, scientific monitoring and analysis of carbon emission changes and associate influencing factors is of great significance to the high-quality development of the Yangtze River Basin. In this paper, the long time series DMSP/OLS and NPP/VIIRS nighttime light datasets were constructed to estimate carbon emissions in the Yangtze River Basin. The spatial autocorrelation analysis and GTWR model were used to explore the spatio-temporal pattern and spatial heterogeneity of carbon intensity. The results showed that:(1)The goodness of fit of the two types of night-light data fusion models was 0.93, at the significance level of P<0.001, which met the accuracy requirements; The carbon emission estimation models for provinces had a fitting accuracy of 0.85 and an  average relative error of 14.54%, at the significance level of P<0.001, which met the requirements of estimation accuracy.(2)The global autocorrelation analysis found that the global Moran's I of the municipal-scale carbon emissions from 2000 to 2021 were all greater than 0, at significance level of 1%. The municipal-scale carbon intensity had a significant spatial positive correlation. (3) In the local autocorrelation analysis, a significant aggregation at the municipal scale was found to decrease from 51.82% in 2000 to 43.52% in 2021, with certain spatial aggregation of carbon intensity. (4) The regression results of the GTWR model showed that the influence of land use on carbon intensity was the largest and had positive effects. The influence of industrial structure was the second largest, the population density had a bidirectional influence, and the level of economic development had the lowest and negative effects. The results of the study showed that it was of great significance to give full play to the demographic and economic advantages of the Yangtze River Basin in terms of rational planning of land use, promotion of low-carbon transformation of industries and upgrading of the industrial structure, in order to encompass the ecological environment and to accelerate the realization of the goal of "dual-carbon".

The total nitrogen (TN) flux from the Yangtze River into the sea has a significant impact on the water environment and aquatic ecology of the coastal waters.Based on the selected cross-section, TN concentration and flux into the sea of the Yangtze River Estuary from 2005 to 2022 were studied.The results showed that: (1) Annual TN flux fluctuated greatly.The maximum (2.63 million ton/a) flux was 2.7 times of the minimum.The flux showed the trend of first increasing and then decreasing.During 2008 through 2019, fluxes were relatively high with greater 2.00 million ton/a in most years.Since 2016, the yearly TN flux showed an overall downward trend, from 2.63 million ton/a in 2016 to 1.16 million ton/a in 2022.(2) The annual TN flux and runoff fluctuated with the similar rhythm.A higher TN flux was often accompanied with a higher runoff.Comparisons under the condition of similar runoffs, the change of annual TN flux indicated the significant effectiveness in water pollution control.(3) TN concentration in the Yangtze River Estuary was higher during the dry season than during the wet season, with an average increase of 24%; However, TN flux into the sea was significantly higher during the wet season than that during the dry season, and the former was approximately 1.93 times that of latter.(4) During 2016~2022, TN loads from the upper reach of the Yangtze River, Dongting Lake, Han River, and Poyang Lake accounted for 43.8%, 24.4%, 4.9%, and 10.8%, respectively, of the total flux.The net increase in TN load in the mainstem of the middle and lower reaches of the Yangtze (excluding sources from the upstream, Dongting Lake, Han River, and Poyang Lake, i.e.TN loads from other tributaries and those entering directly the mainstem) accounted for 16.2%.

The concentration of dissolved organic carbon (DOC), UV-visible light absorption characteristics and three-dimensional fluorescence spectrum characteristics of chromophoric dissolved organic matter (CDOM) were measured in surface water collected from typical tidal creeks of Chongming Dongtan during the spring tide in July 2018. Combined with parallel factor analysis and statistical analysis, the sources, composition and influencing factors of dissolved organic matter in salt marsh wetland during the flood and ebb tides were discussed. The results showed that the UV absorption coefficient at 355 nm, a(355), during the tidal process was significantly correlated with DOC concentration, which characterized DOC concentration and behavior to a certain extent. The spectral slope Sg and specific ultraviolet absorbance SUVA254 indicated that the aromaticity of salt marsh water was stronger than that of estuarine water, suggesting the important role of terrestrial input. The three-dimensional fluorescence spectrum of CDOM revealed that it contained terrestrial humic-like substances, protein-like substances and marine humic-like substances, which were significantly correlated with tidal changes, in which C2 components from terrestrial higher vegetation were consistent with tidal height changes. The fluorescence index (FI) and humification index (HIX) of the sampling water were 1.19 ~ 1.40 and 1.71 ~ 2.75, respectively, and biological index (BIX)< 1. The dissolved organic matter in the water was mostly terrestrial input, but the humification degree was relatively low. Based on the results of principal component analysis and fluorescence characteristics analysis, the terrestrial organic matter from higher plants or soil organic matter dominated the source of CDOM. The composition of dissolved organic matter in salt marshes was complex and changeable due to the combined effects of local resuspension, pore water release and tidal lateral transport. In the future, it is necessary to expand the time and space comparison to explore the generation, demise and trajectory of CDOM. 

Understanding the spatiotemporal characteristics and interrelationships among ecosystem services and ecological risks is crucial for crafting targeted ecosystem management strategies, ensuring regional ecological security and sustainable development. Wetlands provide various crucial ecosystem services to humanity, yet they exhibit high ecological sensitivity and are susceptible to disturbances from urbanization and human activities. This study focused on the Hangjiahu Plain, and utilized data from land use and socioeconomic statistics for 2000, 2010, and 2020. By employing the InVEST ecosystem service model, landscape ecological risk index, bivariate spatial autocorrelation analysis, and geographically weighted regression model, a quantitative assessment was conducted to explore the spatiotemporal trends and correlations between ecosystem service functions and landscape ecological risks. The results showed that: (1) From 2000 to 2020, the wetland ecosystem services in the study area decreased gradually from the high-value area in the southeast, and expanded outward sequentially. A transition from aggregative to dispersive with time was found. (2) The landscape ecological risk indices were 0.0286, 0.0277, and 0.0266, respectively. The overall ecological risk level in the study area shifted from a moderate risk level to a lower risk level. High and moderately high-risk areas were mainly distributed in patches in the western and northern parts of the study area. (3) Landscape ecological risks and ecosystem services exhibited spatial clustering characteristics. The relationship between landscape ecological risks and comprehensive ecosystem services showed a significant negative correlation, indicating a feedback effect. This negative impact and correlation gradually weakened over time. This study provided a theoretical basis for the development of policies aimed at reducing regional ecological risks and enhancing the capacity of ecosystem services to sustain the continuous health and stability of wetland ecosystems.

With the rapid urbanization and frequent artificial construction activities, the water network area in southern Jiangsu Province is facing a series of ecological and environmental problems, and ecological risks are becoming increasingly prominent. Constructing an ecological security pattern based on landscape ecological risk assessment is a powerful way to enhance the stability of the regional ecological environment. In this study, we took the Baixian Lake area of Suzhou as an example, and we adopted the landscape pattern index to construct a landscape ecological risk assessment model. The spatiotemporal differentiation characteristics of landscape ecological risks were analyzed in the study area from 2010 to 2020. We simulated the land use pattern under urban expansion scenarios based on the CA-Markov model, and predicted the spatial distribution of landscape ecological risks. On this basis, we explored the construction of ecological security pattern under the spatiotemporal dynamic evolution. The results indicated that: (1) The land use pattern changed significantly from 2010 to 2020. The area of construction land increased by 59.32 km2, while the area of farmland and water area decreased by 17.98km² and 53.61km² ,respectively. The area of forest land and grassland slightly increased by 12.27 km². The urban expansion scenario simulation indicated that the construction land would extend the most by 2030, with an increase of 134.14 km². The area of farmland and water area would decrease by 174.06km² and 6.76km² respectively. The total area of forest land and grassland would increase by 46.68km2. (2) From 2010 to 2020, the landscape ecological risk continued to increase. The proportion of medium risk and high risk areas increased by 6.55% in total, while the low and medium-low risk areas decreased by 4.62% and 1.92% respectively. The simulation of urban expansion in 2030 indicated that the proportion of medium-high ecological risk areas would increase by 10.12%, while the medium-low and low risk areas would decrease by 19.14%. (3) Based on the land use pattern in 2020 and the ecological security pattern under the urban expansion scenario simulation in 2030, we identified 23 ecological source areas, 50 ecological corridors, and 21 ecological nodes in the study area. A comprehensive ecological security pattern under spatiotemporal dynamic changes was constructed. The results may provide theoretical basis for protecting the ecological environment in water network areas and for resisting external ecological risks, which is significant for promoting regional ecological security development.