As a primary national development strategy in the new era, the Yangtze River Economic Belt (YREB) still faces the problem of unbalanced regional development in the current stage.It is of great significance to study the comprehensive carrying capacity of the old industrial cities in the YREB to revitalize them and promote the coordinated and sustainable development.Based on the panel data of 32 old industrial cities from 2012 to 2022, the comprehensive carrying capacity index evaluation system of old industrial cities was constructed.Five dimensions were included, such as society, economy, infrastructure, resources and environment.The Dagum Gini coefficient, optimal parameter geographic detector and spatiotemporal weighted regression (GTWR) model were used.The results showed that: (1) The comprehensive carrying capacity of the old industrial cities increased significantly during the study period, and its mean value showed a trapezoidal distribution of "high in the east and low in the west".(2) There existed development differences in the comprehensive carrying capacity, among which regional differences were the main one that affected the overall differences.(3) It was found that urbanization level, science and technology expenditure, economic development, foreign investment, consumption level, green innovation, and digital infrastructure had apparent driving effects on the comprehensive carrying capacity of the old industrial cities, and the driving interpretation would be significantly improved after the dual effects.(4) The urbanization level had the most significant effect of an increasing trend on the comprehensive carrying capacity.The catalytic role of green innovation and digital infrastructure continued to wane over time.This research provided a reference value for promoting the comprehensive carrying capacity of the old industrial cities in the Yangtze River Economic Belt.

As China enters the digital economy era, digital transformation has catalyzed innovative business models, injected new economic vitality, and provided critical technological support for enhancing urban ecological resilience. This study constructed a comprehensive evaluation system for digital economy development and ecological resilience. The panel data from 105 cities in the Yangtze River Economic Belt from 2010 to 2022 were used to examine the impact and mechanism of digital economy on enhancing the ecological resilience. The results indicated that the positive development of the digital economy significantly enhanced the ecological resilience. This promoting effect was stronger in the cities with low levels of economic development, the cities in the middle and upper reaches of the Yangtze River, and the resource-based cities. Mechanism analysis revealed that this enabling effect operated through two key pathways: reducing energy consumption intensity and advancing technological innovation. Robustness checks and instrumental variable approaches confirmed the reliability of these findings. Policies and suggestions were proposed to further promote the ecological resilience, which included the increased support for the development level of the digital economy, the focusing on reducing energy consumption and waste, and the vigorously supporting technological innovation activities.

Accurately assessing urban resilience and identifying core obstacle factors are of great significance to high-quality urban development.Taking the Yangtze River Economic Belt (YREB) as the study area, this paper measured urban resilience from five dimensions: economic resilience, social resilience, institutional resilience, ecological resilience, and infrastructure resilience.This study revealed the spatiotemporal evolution characteristics of urban resilience from 2003 to 2021 by coupling the methods of spatial autocorrelation and time series clustering.The core obstacle factors were identified based on the obstacle degree model.The main results were as follows: (1) The urban resilience level of the YREB had increased year by year, and the growth trend could be divided into three stages: the germination period, the steady growth period, and the rapid improvement period.(2) The urban resilience levels in the upper, middle, and lower reaches had all shown a continuous upward trend.Among them, the average urban resilience in the lower reaches was always significantly higher than that in the middle and upper reaches, while the relative difference between the middle and upper reaches was small.(3) The urban resilience level of the YREB presented a spatial pattern of high at both ends and low in the middle, with significant positive spatial autocorrelation.The results of local spatial autocorrelation showed that the scope of the high-high agglomeration area in the Yangtze River Delta had shrunk, and the low-low agglomeration area in the upper reaches had gradually disappeared.(3) The urban resilience in the study area indicated four main evolution modes, namely, the continuous improvement type, the continuous decline type, first rise then fall type, and the fluctuating decline type.(4) Response infrastructure, industrial transformation, municipal infrastructure, and ecological environment were the main obstacles to improving urban resilience.Cities in the YREB should promote the steady improvement of urban resilience through cross-regional cooperation in urban industrial innovation, response infrastructure upgrading, and ecological restoration.

Against the backdrop of China’s "Prospering the Nation with Quality" and "Beautiful China" initiatives, the co-evolution of regional industrial upgrading and green development has become imperative. Drawing on panel data for the 41 cities of the Yangtze River Delta from 2006 to 2019, this study employed a panel vector autoregression (PVAR) model, impulse response functions (IRF) and forecast-error variance decompositions to examine the bidirectional interaction between industrial structure and green development. The main findings were as follows: (1) The industrial structure across the Yangtze River Delta advanced toward greater sophistication and rationality, yet intra-regional disparities remained pronounced. Shanghai, southern Jiangsu, northern Zhejiang and a handful of cities in Anhui simultaneously improved both the rationalization and sophistication of their industrial structures, whereas other areas lagged substantially. (2) Overall green-development performance in the Yangtze River Delta became better, but the trajectories diverged between steady ascents and fluctuating progress. Shanghai and the provincial capitals had sustained improvements, while Anhui exhibited greater volatility and was at consistently lower levels. Technological advancement emerged as the primary constraint on further green-development gains in the region. (3) Industrial-structure optimization and green development exhibited a dynamic pattern of “short-term inhibition, long-term synergy.” Both processes displayed significant self-reinforcement. Notably, the rationalization of industrial structure explained a larger share of the forecast-error variance in green development than the sophistication dimension. These conclusions provided scientific guidance for high-quality, coordinated development in the Yangtze River Delta and offered theoretical support for exploring win-win pathways of integrating economic growth with ecological improvement.

To explore the structural characteristics and the influencing factors of the phytoplankton community in Dongting Lake, an investigation  was carried out in different parts of the Lake during three hydrological periods in 2023.The results showed that a total of 44 genera belonging to 6 phyla of phytoplankton were identified in the Lake, which included 16 genera of Chlorophyta, 12 of Bacillariophyta, and 10 of Cyanophyta.The average density of phytoplankton was 83.69×104 cells/L.Bacillariophyta was identified as the most abundant one, followed by Pyrrophyta and Cyanophyta, which accounted for 62.0%, 13.1%, and 10.1% respectively.In terms of the hydrological period distribution, the average density of phytoplankton followed the order of the wet season > the normal season > the dry season.Spatially, the density was in the order of West Dongting Lake > South Dongting Lake > East Dongting Lake, with Bacillariophyta being the dominant group.The Shannon-Wiener diversity index of Dongting Lake ranged from 2.76 to 3.17.East Dongting Lake was rated as excellent, while West and South Dongting Lakes were in a good state.The comprehensive trophic state index of the whole lake was 46.7, indicating a mesotrophic level.The results of the redundancy analysis showed that the main factors affecting the distribution of phytoplankton were water temperature and dissolved oxygen.This study reflected the status of the aquatic ecological environment in Dongting Lake and provided data support for the ecological restoration, protection, and management of the Lake.

The ten-year ban on fishing in the Yangtze River is a major ecological strategy in China.To grasp the dynamics of fish resources is an important basis for scientific ban on fishing.Based on systematic survey data from 12 sections of the Hanjiang River in Shaanxi Province from 2022 to 2023, and combined with a historical data comparison, this study analyzed fish community structure and its spatiotemporal evolution characteristics, using the Shannon-Wiener diversity index, G-F index, relative importance index (IRI), and fish individual ecology matrix.A total of 93 fish species (belonging to 60 genera, 15 families, and 5 orders) were collected during the survey, with 55 Cyprinidae species and 13 Bagridae species accounting for 73.1% of the total.Three national protected species including Hucho bleekeri were recorded.Hemiculter leucisculus (IRI=1237) and Xenocypris davidi (IRI=1158) were the absolutely dominant species, accounting for 21.9% of the total catch.Compared to 1985, the overall similarity of fish communities was 0.56 (moderate similarity), indicating a significant species loss.Fish biodiversity in the main stream (H’=2.00) was significantly higher than that in the tributaries (H’=1.52).The G-F index (0.521) increased by 3.8%, compared to historical values, which reflected an increased inter-family diversity and a reduced intra-family diversity.The results showed that fish communities in the study area exhibited the trends of slow-flow adaptation (81.0% proportion), omnivorous feeding (81.0%), and miniaturization (<50 g individuals accounting for 65.7%).Although fish diversity had recovered to some extent after the implementation of the fishing ban, ecological functions had not yet fully recovered.It was recommended to restore habitat connectivity, regulate ecological water flow, and implement rescue protection for the endangered species to provide scientific support for ecological conservation in the Yangtze River Basin.

Heavy metal pollution in fish is a global concern.To investigate the accumulation characteristics of heavy metals in fish species in Chishui River, muscle tissue from 14 fish species (Onychostoma sima, Bangana rendahli, Garra pingi, Schizothorax grahami, Hypophthalmichthys molitrix, Hemibarbus labeo, Mystus macropterus, Spinibarbus sinensis, Procypris rabaudi, Pelteobagrus vachelli, Cyprinus carpio, Carassius auratus, Silurus asotus and Siniperca chuatsi) were collected in September 2023.Differences in the concentration of heavy metals (including Cr, Mn, Fe, Cu, Zn, As, Cd, Pb and Hg) among species and dietary functional groups, as well as pollution levels, were analyzed in this study.The distribution of heavy metals such as Cr, Mn, Fe, Cu, Zn, As, Cd, Pb and Hg was explored from multiple perspectives, including interspecies differences, differences in feeding functional groups and pollution levels.The results showed that the contents of essential elements such as Cr, Fe, Zn, Cu and Mn were higher in fish, while the contents of non-essential elements such as As, Cd, Pb and Hg were relatively lower.There were significant interspecies differences in heavy metal contents.The Mn and Pb contents in Hypophthalmichthys molitrix, Fe content in Garra pingi, Cu content in Silurus asotus, Zn content in Carassius auratus, As content in Cyprinus carpio, and Hg content in Mystus macropterus were significantly higher than those of other species (P < 0.05), and there were no significant differences in the contents of Cr and Cd in different species (P > 0.05).The contents of heavy metals in different dietary fishes showed obvious differences.The total accumulation of heavy metals was the highest in phytoplanktivorous fishes, followed by planktonic algal dietary fishes, omnivorous and ichthyophagous fishes, and the lowest in benthic invertebrate dietary fishes.The Mn and Pb contents of planktonic algal-feeding fish, As content of entomopathogenic algal-feeding fish, and Hg content of fish-feeding fish were significantly higher than those of other fish-feeding species (P<0.05), while no significant differences were observed for Cr, Zn, Fe, Cd and Cu (P>0.05).The distribution pattern of Bioconcentration Factor (BCF) of different heavy metals was Cu>Fe>Cr>Zn>As>Mn>Pb>Hg>Cd.The logarithmic values of Bioconcentration Factor (log10BCF) of different heavy metals were less than 3, indicating that the level of bioaccumulation of heavy metals by fish was low.The values of heavy metal pollution index (MPI) in fish muscle tissue ranged from 0.161 to 0.341, revealing that the overall heavy metal content in fish muscle was at a low level.This study provided basic information for understanding the heavy metal pollution status of fish in Chishui River, and provided scientific basis for future ecological risk assessment and environmental protection.

Enhancing the efficiency of territorial space utilization and promoting the coordinated development of urban, agricultural, and ecological space utilization are effective pathways to alleviate the tension between population and land resources and achieve sustainable regional development.The Yangtze River Economic Belt, as a core area of national strategy, still faces severe challenges such as the compression of ecological space and the misallocation of resources in its three major urban agglomerations.Scientifically evaluating the territorial spatial utilization efficiency and its coupled coordination characteristics of the three major urban agglomerations is of great significance for achieving regional sustainable development, optimizing resource allocation, and promoting the integration and high-quality development of the study area.This study took the period from 2000 to 2020 as the research period, and selected 70 prefecture-level cities in the three major urban agglomerations of the Yangtze River Economic Belt as the research objects.The Super-SBM model was constructed to measure the utilization efficiency of urban, agricultural, and ecological spaces.The exploratory spatial data analysis was used to parse the spatial association characteristics between subsystems.The coordinated development level of the utilization efficiency of the three types of spaces was quantified using the coupled coordination degree model. The results showed that: (1) There were significant differences in the spatial utilization efficiency of each subsystem in the three major urban agglomerations.The utilization efficiency of urban and agricultural spaces continued to rise, with the average annual growth rates of 16.3% and 5.9%, respectively.The utilization efficiency of ecological space generally declined, with the average efficiency value decreasing from 0.302 in 2000 to 0.251 in 2020.(2) The global spatial autocorrelation of each subsystem gradually increased, and there was a positive correlation between the utilization efficiency of urban-agricultural space and urban-ecological space, while there was a negative correlation between the utilization efficiency of agricultural-ecological space.The local spatial autocorrelation characteristics were mainly characterized by significant high-high and significant low-high clusters.(3) The coupled coordination of territorial spatial utilization efficiency in each region of the three major urban agglomerations showed an upward trend.The spatial distribution of the degree of coupled coordination showed the characteristic of "center-periphery" distribution.The number of coordinated areas increased from 9 to 16, but 54 cities were still in a state of disharmony (accounting for 77.1%).In the future, it is necessary to promote the coordinated development of the three major urban agglomerations, optimize the layout of urban, agricultural, and ecological spaces.It is also important to explore the spatial development strategies that meet the characteristics of different regions, and to promote the complementarity of advantages between regions to achieve sustainable high-quality development.

The development of urban blue-green spaces is highly recommended as a nature-based solution for mitigating the urban heat island (UHI) phenomenon, improving urban sustainability, and enhancing resident well-being.Therefore, accurately and conveniently quantifying their cooling effect and mechanisms is crucial for effective urban spatial planning and high-quality development.In this study, Landsat 8 cloud-free images from the summer of 2021 were used to retrieve land surface temperature (LST) and related indices.Five evaluation methods, including the study area method (SAM), equal radius method (ERM), impervious surface method (IMM), maximum perspective method (MPM), and accumulative perspective method (APM), were applied to estimate the cooling intensity (CI) for a total of 375 green space, water body, and urban park patches in 25 cities within the Yangtze River Delta region.This study also explored the spatial characteristics and environmental impacts on CI.The results indicated that: (1) CI estimated by the five methods showed a significant correlation for most categories of blue-green spaces.All landscape categories exhibited a high correlation between IMM and ERM with MPM, while APM showed the highest correlation coefficient with MPM in green spaces and urban parks.(2) The cooling effects obtained by different estimation methods varied, with IMM presenting the highest average CI values, followed by MPM and ERM, while APM exhibited the lowest CI values.SAM demonstrated instability at the city scale.(3) Dominant factors influencing the cooling effect of different blue-green spaces exhibited significant differences.Green spaces were mainly influenced by internal vegetation coverage and human activities, water bodies displayed a relatively notable correlation with patch spatial characteristics, and the cooling capacity of urban parks was highly related to their surrounding environment.These findings are essential for city planners to understand the cooling effect in comparable urban contexts and provided scientific references for sustainable urban management.

Water yield not only has a significant impact on the hydrological cycle and water balance of a basin but also closely related to regional natural environments and human activities.Investigating the spatiotemporal variation patterns and driving mechanisms of water yield is of critical practical importance for optimizing regional spatial planning and enhancing ecosystem services.This study evaluated water yield in the Wuling Mountain Area from 2000 to 2022 using the InVEST model, analyzed its spatiotemporal characteristics and future trends through coefficient of variation (CV), Theil-Sen trend analysis, Mann-Kendall significance test, and Hurst index, and explored driving factors using geodetector and multi-scale geographically weighted regression (MGWR) models.The results indicate that:1) The water yield in the Wuling Mountain Area exhibited pronounced fluctuations with a slight upward trend, showing spatial heterogeneity characterized by a "high in northwest and southeast, low in southwest and northeast" distribution pattern.2) The coefficient of variation for water yield fluctuated significantly, and although a weak increasing trend was observed historically, future projections suggest a nonsignificant decline.3) The water yield in the Wuling Mountain Area results from the combined effects of natural factors and human activities.From 2000 to 2022, the driving factors were ranked by their influence magnitude as follows: GDP, slope, NDVI, population, aspect, topographic relief, NPP, elevation, and temperature.Notably, the interaction between NPP and slope (0.801) exhibited the strongest combined influence, followed by NPP∩topographic relief (0.787), slope∩population (0.772), and NPP∩NDVI (0.756).4) The impacts of driving factors on water yield in the Wuling Mountain Area exhibit distinct spatial heterogeneity.Precipitation, elevation, temperature, and population demonstrate strong positive driving effects on water yield services, whereas evapotranspiration, NDVI and GDP show pronounced negative effects.Spatially, the influence of precipitation, evapotranspiration, temperature, and GDP on water yield is more prominent in the northeastern part of the study area, while NPP, elevation, slope, and aspect dominate in the southeastern region.A pivotal finding is the shift in NPP’s impact on water yield from positive to negative in 2010.Additionally, aspect and topographic relief exert positive effects on water yield in low-altitude zones but transition to negative effects in high-altitude areas.This study provides scientific support for water resource utilization, management, and ecological sustainability in the Wuling Mountain Area, offering guidance for ensuring water security in the Yangtze River Basin.

With the promulgation of the Yangtze River Protection Law and the implementation of the critical campaign for ecological conservation and restoration of the Yangtze River, significant progress has been made in the ecological and environmental protection of the Yangtze River Basin. However, under the pressure of rapid economic development, the ecological and environmental protection of the basin still faces multiple challenges. These include the imbalance between socioeconomic development and ecological conservation, regional disparities in water quality improvement, high intensity of water resource exploitation, unabated degradation of aquatic ecosystems, and persistent pressures from water environmental risks. To effectively address these challenges, the 15th Five-Year Plan, as a crucial phase for consolidating the foundation of ecological and environmental protection and achieving comprehensive improvements, should prioritize the following measures: coordinating the relationship between ecological conservation and socioeconomic development, promoting green and low-carbon development models, enhancing the implementation of water pollution control, sustainable water resource utilization, and aquatic ecosystem protection, strengthening risk prevention in key regions and across the basin, and comprehensively improving the effectiveness of ecological conservation and restoration in the Yangtze River Basin.

The Yangtze River Economic Belt is densely populated, with diverse human activities such as urbanization, economic investment, and energy consumption, causing complex changes in ecosystem service functions and their spatial carrying capacity. Clarifying the impacts of human activities on ecosystem services from spatial, economic, and energy perspectives is crucial for the high-quality development of the region. This study focuses on the Yangtze River Economic Belt, selecting meteorological data and ecological remote sensing data from 2002 to 2022, and using the InVEST model, Human Footprint Index model, bivariate spatial autocorrelation, and geographically weighted regression model to quantify and analyze the intensity of human activities in the Yangtze River Economic Belt and their impacts on ecosystem services in spatial, economic, and energy dimensions. The results show that: (1)The intensity of human activities in the Yangtze River Economic Belt has significantly increased over time, with the Human Footprint Index increasing by 0.022 from 2002 to 2022; spatially, it exhibits a pattern of “weaker in the west and stronger in the east, higher in the north and lower in the south”, and the downstream region has the highest intensity of human activities from all perspectives. (2)The ecosystem services in the Yangtze River Economic Belt show a spatial distribution pattern of “higher in the west and lower in the east, higher in the south and lower in the north”; the capacity of ecosystem services slowly decreased from 2002 to 2012, and generally increased from 2012 to 2022; areas with lower ecosystem service capacity accounted for the largest proportion during the study period, with an average of 33.39%, while areas with high ecosystem services capacity accounted for the smallest proportion, with an average of 7.78%. (3)The intensity of spatial human activities in the Yangtze River Economic Belt has a significant negative impact on ecosystem services. From an economic perspective, there is a synergistic effect between the intensity of human activities and ecosystem services in economically developed areas; while a mismatched relationship is observed in economically underdeveloped areas. The negative impact of energy-related human activities intensity on ecosystem services is relatively small and shows a weakening trend.

The analysis of the spatial-temporal characteristics of the influencing factors of tourism ecological security in the Yangtze River Economic Belt (YREB) can provide useful reference for the high-quality development in the region. The DPSIR model was used to construct the city-scale tourism ecological security evaluation index system of the YREB. The spatial-temporal characteristics of the tourism ecological security were explored from 2010 to 2020. The GTWR model was used to analyze the influencing factors of tourism ecological security. The findings were as follows: (1) In terms of temporal changes, the level of tourism ecological security showed an approximate “W” type evolution trend, the overall level of tourism ecological security was rising, and the risk level gradually changed from risky level to sensitive level and critical level. (2) In terms of spatial pattern, tourism ecological security presented significant spatial heterogeneity, showing the spatial features of “agglomeration in low-value areas and discrete distribution in high-value areas”, and the “core-edge”decreasing effect was obvious; The spatial agglomeration of tourism ecological security level in cities was weak, the agglomeration in the downstream area was higher than that in the upstream area. The number of “low-low” agglomeration areas was on the rise, and the number of “high-high” agglomeration areas was on the decline. (3) From the perspective of impact degree, GDP growth rate and per capita disposable income had a significant positive impact on tourism ecological security, while per capita tourism income, green space and education expenditure had a small impact on the proportion of general public budget; The spatial heterogeneity of influencing factors was significant. The influencing coefficient of GDP growth rate and per capita disposable income showed a distribution pattern of “high in the west and low in the east”. The influencing coefficient of population density showed a trend of gradual decline from east to west, and the influencing coefficient of the proportion of education expenditure in the general public budget showed a negative gradient pattern of “weak in the east and strong in the west”.

In this work, to understand systematically the intensity of endogenous pollution in urban streamways, 73 sampling points were selected, the sediment stock was calculated, and the distribution characteristics of carbon, nitrogen and phosphorus in sediment and interstitial water were analyzed in a large scale area (100.8 km2), taking Suzhou water network area as the research object. Meanwhile, the changes of the water quality under water exchange, water diversion, and dredging scenarios were predicted by designing a comprehensive treatment of the water environment according to the average loads of pollutants along the rivers. The results showed that the total mass of sediment in Suzhou water network area was about 4.7×106 t, in which the average contents of TOC, TN, NH4+-N, TP and available phosphorus were 1.5%, 1270 mg/kg, 121.7 mg/kg , 1339 mg/kg and 44.4 mg/kg respectively, and 79% of the sampling points were in polluted condition. The average concentrations of TOC, BOD5, COD, TN, NH4+-N, TP and phosphate in the interstitial water of the rivers in the Suzhou water network area were 5.9, 9.6, 124.2, 12.4, 8.4, 5.9 and 0.5 mg/L respectively, and the concentrations of TP in 70% of the sampling points after 20 times dilution were belonged to class III surface water quality. Correlation analysis results showed that the partition coefficient of NH4+-N was negatively correlated with the TOC content in the sediment, and the increase of TOC content would cause NH4+-N migration from the interstitial water to the sediment. The total mass of TN in the water was reduced by 1.4 t and 1.2 t respectively and the total mass of TP was reduced by 2.4 t and 2.3 t respectively under the changing water scenario and the diversion water scenario; the total mass of TN in the water was reduced by 18.4 t and the total mass of TP was reduced by 10.1 t under the scenario of changing water after dredging; and the total mass of TN was reduced by 18.5 t and the total amount of TP was reduced by 10.2 t under diversion water scenario.  The results of this work have theoretical reference significance for understanding the sources of river pollution and designing the treatment projects in Suzhou water network area.

Understanding the effects of hydrological connectivity loss on lake water quality is critical for developing targeted restoration strategies. As China’s largest freshwater and a historically river-connected lake, Poyang Lake has experienced progressive fragmentation since the 20th century due to dam and levee construction, isolating its subsidiary lakes (e.g., Zhuhu, Junshan, Kangshan, Xinmiao, and Nanbeigang). However, systematic comparisons of water quality between the main lake and these isolated subsystems remain scarce. To address this gap, we conducted a comprehensive survey analyzing spatiotemporal variations in physicochemical parameters. Key findings revealed: (1) Isolated lakes exhibited greater fluctuations than Poyang Lake, particularly for Chl-a (CV: 79% in Kangshan Lake vs. 73% in Junshan Lake) and nutrients (CODMn, NH3-N, PO4-P, TN, TP). (2) Kangshan Lake (γ = 1.25) and Nanbeigang (γ = 1.14) reached moderate pollution levels, significantly exceeding Poyang Lake in TN (p < 0.05 vs. Junshan/Zhuhu/Xinmiao) and TP (p < 0.05 vs. Zhuhu/Nanbeigang). (3) Anthropogenic pressures (fertilizer use, industrial density) dominated water quality disparities, while hydrological factors (water depth) exerted secondary effects. These results underscored the need for dual interventions: (i) stringent control of watershed pollutant loads and (ii) engineered reconnection to restore natural flow regimes.

In order to clarify the impact of extreme precipitation and human activities on sediment transport in the Jinsha River Basin,  daily precipitation data from 1974 to 2018 at 27 meteorological stations in the basin and its surrounding areas were collected. Seven extreme precipitation indices were selected and calculated using RClimDex model. The spatiotemporal distribution characteristics of each extreme precipitation index were analyzed. The double accumulation curve method and random forest model were used to quantitatively calculate the contribution of extreme precipitation to the reduction of sediment transport. The conclusions were as follows: (1) All the extreme precipitation indices showed an upward trend except CWD. The duration of the heavy precipitation events gradually extended, and the precipitation intensity increased significantly. The southeast of the basin was the main area of heavy precipitation. The precipitation intensity gradually decreased from the southeast to the northwest, while the precipitation duration was the longest in the middle of the basin. (2) Abrupt changes occurred in the annual sediment transport in 2002 and 2013. The double accumulation curve method showed that CWD, the number of consecutive rainy days, had the greatest impact on the reduction of sediment transport during 2003-2013, with a rate of 3.8%. The heavy precipitation index (R95P), had the greatest contribution rate during 2014-2018, with a rate of 4.1%; The random forest model revealed that the influence of extreme precipitation index on sediment transport reduction was less than 10%. (3) The effects of human activities on sediment transport were further analyzed through the changes of land use types in the basin and sediment containment of nearby reservoirs during 1980-2018. Since the 21st century, human activities in the basin had become more intense, and a large amount of unused land had been transformed into grassland. The sediment retention rate of large hydropower stations in Shigu - Pingshan Station during 1974-2013 was calculated, and the sediment retention rate was all above 60%, i.e., the sediment retention effect of the reservoir was obvious.  In summary, human activities were the main factors leading to the decrease of sediment transport in the basin. The extreme precipitation had little influence on the change of sediment transport in the basin. The contribution of different precipitation indexes was different from each other.

The water level fluctuation zone of reservoirs represents a transitional area between terrestrial and aquatic ecosystem. Clearly defining the spatial distribution characteristics of this fluctuation zone is crucial for both the protection of ecological environments and ensuring the safe operation of reservoirs. In this study, 35 large reservoirs in Sichuan Province were selected as the research objects. The gradient distribution of the landforms and the corresponding driving factors were explored within the 5-km buffer zone. Additionally, the change in explanatory power (q) was explored by progressively expanding the buffer zone range. The results indicated that: (1) The water level fluctuation range in low-slope area was primarily concentrated in the regions with a low altitude, whereas in the high-altitude and high-slope areas, the gradient distribution of water level fluctuation zone tended to be more uniform. (2) Within the 5-km buffer zone surrounding the water level fluctuation zone, the optimal parameter geographic detector was employed. It was revealed that the primary driving factors were geomorphology, annual evaporation and annual average temperature. (3) The explanatory power (q) of most factors exhibited a decreasing trend as the buffer zone was progressively expanded by 5 km increments, which indicated that the influence of the buffer zone on the fluctuation zone was distance-dependent. This study provided valuable data support and a theoretical foundation for the formulation of policies on ecological restoration and operational management of regional reservoir water level fluctuating zones.

In the context of the “dual-carbon” goal, it is of great significance to explore the impact of digital village development on agricultural carbon productivity. Based on the panel data of 30 provinces in China from 2010 to 2022, we empirically examined the effect of digital village development on agricultural carbon productivity. The results of this study showed that: (1) the level of digital village development and agricultural carbon productivity in all provinces showed an upward trend from 2010 to 2022. A spatial distribution pattern of “strong in the east and weak in the west”was indicated. (2) Digital village development promoted the increase of agricultural carbon productivity, and this conclusion still held after a series of robustness tests such as instrumental variables. (3) Digital rural development affected agricultural carbon productivity through two paths: one was through the improvement of the level of green innovation. The other was through the increase of farmers′ income. (4) Heterogeneity analysis showed that digital rural development had a significant effect on agricultural carbon productivity in the eastern, central and western regions, but not so in the northeastern region. There was a significant promotion effect of digital village development on agricultural carbon productivity in the main grain production area, the grain production and marketing balance area and the main grain marketing area. The promotion effect was the greatest in the grain production and marketing balance area. There was a significant promotion effect in both steep and gentle zones, however, the promotion effect was more obvious in the steep zones. (5) The results of the threshold effect showed that the positive impact of digital rural development on agricultural carbon productivity was characterized by a non-linear increment.

Accurately monitoring and analyzing the dynamics of carbon emissions from grain cultivation is crucial for guiding the transformation of low-carbon agriculture, ensuring regional ecological balance and achieving sustainable development goals. In this paper, the life cycle method was used to measure the carbon emissions from grain planting in the Yangtze River Economic Belt (YREB). Based on the functional production zoning of grain, the fairness was analyzed by using the dagum Gini coefficient. The change trend of carbon emissions from grain planting under the benchmark scenario from 2023 to 2030 was predicted based on STIRPAT extended model and scenario analysis. The results showed that: (1) The total net carbon sink of grain cultivation in the YREB showed a fluctuating upward trend from 2011 to 2022, and a spatial pattern of “high in the north and low in the South”. (2) The overall fairness was fair and showed an improvement trend. Regional differences in carbon emissions were the main source of overall inequity. (3) Carbon emissions from grain planting in most provinces and cities of the YREB had reached the peak. (4) The carbon emission intensity of grain planting formed a pattern of main grain sales area>main grain production area>grain production and marketing balance area. The results provided suggestions for regional carbon control and emission reduction according to local conditions.

To scientifically evaluate the spatiotemporal evolution laws of agricultural land suitability (ALS) in the upper reaches of the Yangtze River, this study constructed a comprehensive evaluation model that integrated geographic information system (GIS), entropy weight method, and dominant factor identification method. This study conducted a spatiotemporal analysis of ALS in the study area from 2005 to 2020. Results showed that: (1) ALS exhibited significant spatial differentiation. Sichuan Basin area (SCB) had favorable natural conditions and was an ideal area for agricultural production. Spatial distribution of Western Sichuan and eastern Tibet areas (WS-ET) was similar to that of Yunnan Plateau area (YNP). The concentrated and contiguous area of moderately and generally suitable level constituted a relatively favorable region for agricultural production. 60% of Guizhou Plateau area (GZP) belonged to the relatively suitable area, but it had obvious patchy characteristics and was a potential area for agricultural production and development. The rest of the agricultural zoning demonstrated a small territorial space area, mostly being at the general suitable level or below, which was rather unfavorable for agricultural production. (2) The agricultural land suitability area (ALSA) continued to decrease. From 2005 to 2010, the reduced area was concentrated in the unsuitable level of YNP and WS-ET and the suitable level of SCB and Southern region of Qiangtang (QT). From 2010 to 2015, the reduced area was concentrated in the relatively suitable level of YNP and SCB and the generally suitable level of WS-ET and SCB. The reduced area from 2015 to 2020 was concentrated in the relatively suitable level areas of WS-ET and GZP. (3) The centroid of overall suitability and all the suitability levels showed differentiated shift trajectories. Shift trajectory of agricultural land centroids was the result of joint driving effect of optimization and concentration of cultivated land and climate change. (4) Soil erosion (SEro), annual precipitation (AP), and soil texture (STex) were the dominant factors of ALS, and the dominant regions were QT, SCB and GZP, WS-ET and YNP, respectively. The results showed that the spatiotemporal evolution characteristics and decreasing trend of agricultural land suitability area (ALSA) in the study area were significant. It was necessary to implement zonal regulation strategies based on the dominant factors to optimize the utilization of cultivated land resources and ensure regional food security.