[Objective] Algal polysaccharide is used as a curing agent in place of traditional cement, with the addition of corn fiber, water-retaining agents, and ecological fertilizers, to improve the ecological restoration performance of the substrate. In previous studies, the algal polysaccharide composite substrate has been preliminarily applied in the ecological restoration of slopes in red soil regions. However, there is still a lack of sufficient research on improving the erosion resistance of the algal polysaccharide composite substrates in red soil. This study aims to address the issues caused by the use of cement as a curing agent in sprayed vegetation techniques, including environmental pollution, difficulty in degradation, and restricted plant growth. [Methods] We selected the red soil slope of a power transmission and transformation project in southern China as the research subject. From previous 16 sets of orthogonal experiments, the best three types of substrates were selected for indoor simulated rainfall experiments. Rainfall intensities were set at 60, 90, 120 mm/h, and the slope gradients were set at 20° and 30°. With a bare slope treated only with clean water as the control group, a total of 72 rainfall experiments were conducted (2 slope angles×3 rainfall intensities×4 slope surfaces×3 repetitions), and the substrate with the best erosion resistance was ultimately selected. [Results] 1) Experimental results showed that on a 20° slope, when the rainfall intensity increased from 60 mm/h to 120 mm/h, the initial runoff yield time for substrates 1, 2, and 3 was shortened by 19.48%, 16.67%, and 30.43%, respectively, compared to the control group. The corresponding stable runoff yield rates were in the ranges of 0.56-2.08, 0.68-2.15,0.61-2.09 L/(min·m²), while the sediment yield rates at rainfall intensities of 60, 90, 120 mm/h were 0.18-0.22 L/(min·m²), 0.41-0.75 L/(min·m²), and 1.12-1.44 g/(min·m²), respectively. On a 30° slope, the initial runoff yield time was shortened by 25.80%, 48.48%, and 40.41%, respectively. The stable runoff yield rates were in the ranges of 0.63-2.21, 0.86-2.38,0.78-2.24 L/(min·m²), and the sediment yield rates under the corresponding rainfall intensities were 0.18-0.39 L/(min·m²), 0.68-0.86 L/(min·m²), and 1.27-1.77 g/(min·m²). 2) The drainage efficiency of the three substrates ranged from 16.35% to 52.73%, with substrate 2 showing the best performance, while the soil conservation efficiency remained stable at 97% to 98%. With increasing rainfall duration, both runoff yield rate and sediment yield rate exhibited a trend of first increasing and then stabilizing. The runoff yield rate of substrate 2 was higher than that of substrates 1 and 3, while the differences in sediment yield rates among the substrates were small. Both the runoff yield rate and sediment yield rate were significantly correlated with runoff shear force (p<0.05). As runoff shear force increased, both the runoff rate and sediment yield rate showed a linear increasing trend. Runoff shear force had the greatest impact on both runoff yield rate and sediment yield, with a significantly higher correlation compared to runoff power, resistance coefficient, and other factors, indicating that it was the primary controlling factor for runoff and sediment yield on the slope. [Conclusion] Algal polysaccharides significantly reduce the initial runoff yield time on substrate slopes, with the reduction becoming more pronounced as the slope angle or rainfall intensity increases. The runoff and sediment yield processes for different substrates under various slope gradients and rainfall intensities are generally consistent. Compared to bare slopes, runoff yield rates of substrate-covered slopes significantly increase, while the sediment yield rates markedly decrease. A significant positive correlation is observed between the runoff yield rate and the hydrodynamic parameters, especially with runoff shear force, which exhibits the highest correlation. However, except for runoff shear force, no significant correlation is found between sediment yield rate and other hydrodynamic parameters. Among the three test substrates, substrate 2 demonstrates superior erosion resistance and is recommended for engineering applications. The optimal formulation for this substrate is algal polysaccharide∶fiber∶fertilizer∶water-retaining agent=1%∶0.8%∶3%∶0.9%. The findings of this study can provide new materials and technical support for similar slope protection projects, promoting the development of green engineering and the high-quality advancement of soil and water conservation.

[Objective] This study aims to understand the pollution characteristics and sources of heavy metals in the riparian soil of the lower reaches of the Fenhe River. [Methods] We collected 32 soil samples from 8 sections in the lower reaches of the Fenhe River and analyzed the content and distribution characteristics of heavy metals. The degree of heavy metal pollution and potential ecological risks were evaluated using the single-factor pollution index method and the potential ecological risk index method. The sources of heavy metals were analyzed through principal component analysis (PCA) and positive matrix factorization (PMF). [Results] 1) The content of heavy metals in the riparian soils of the lower reaches of the Fenhe River was generally low, but the enrichment effects of Pb and Hg were significant. The points with higher contents of Cu, Zn, Cr, Pb and Hg were mainly distributed in urban suburbs and the industrial areas concentrated along the riverbanks. The content of heavy metals in the Yellow River estuary area was relatively low. 2) The potential ecological risk index (PERI) was the highest downstream of Linfen City, at river confluences, and in Hejin City. Hg and Pb were at moderate-severe and moderate ecological risk respectively. This may be affected by the emission of Hg vapor from coal-fired power plants and coking plants downstream of Linfen City and Hejin City, as well as the sedimentation of smoke dust from lead smelters. The river confluences were areas where substances precipitated and accumulated, which was conducive to the enrichment of heavy metals. Industrial parks were scattered in areas such as Xiangfen County and Jishan County, resulting in a higher content of heavy metals in the middle of the lower reaches than in areas flowing into the Yellow River. In the areas with moderate ecological risks of heavy metals Hg and Pb, the contribution rates of Hg and Pb were 54.92% and 31.28%, respectively, indicating that Hg and Pb were the key elements for controlling soil heavy metal pollution in the lower reaches of the Fenhe River. 3) The correlation analysis results among heavy metals showed that there was a significant correlation between Zn and Pb, with a correlation coefficient of 0.671, indicating the influence of human activities on heavy metals in the soil. The high content of Pb in the soil may be caused by the waste gas and waste residue from surrounding industrial and mining enterprises. Dust and wastewater from human activities also caused Zn to enter the soil. The results showed that agricultural production was an important source of Zn and Pb. The unreasonable use of chemical fertilizers and pesticides for agricultural irrigation in the lower reaches of the Fenhe River led to the long-term accumulation of Zn and Pb in the soil, and the exhaust emissions from agricultural machinery also caused the accumulation of Pb in the soil. The dust and waste gas from mining, smelting, and electroplating production of minerals in the study area were deposited into the soil after rainfall, resulting in an increase in the contents of Zn and Pb in the soil. 4) According to PMF simulation, the main source of Hg was industrial production. Cu in the soil had multiple sources, including industrial production, agricultural activities, and transportation. Cr was relatively stable and less affected by human activities. The changes in Cr content were mainly influenced by soil parent materials and geological activities. [Conclusion] In summary, the main sources of heavy metal pollution in the soil along the lower reaches of the Fenhe River are human activities and industrial production. Controlling heavy metal sources at the origin can gradually reduce the heavy metal pollution in basin soils. At the same time, it can also reduce the heavy metal content in the tributary basins of the Yellow River, which is conducive to the overall ecological protection of the Yellow River.

[Objective] The Poyang Lake floodplain wetland ecosystem plays an irreplaceable role in regulating the hydrology of the Yangtze River Basin and maintaining biodiversity. However, due to the combined effects of climate change and human activities, problems such as water quality deterioration and vegetation community degradation have become increasingly prominent, highlighting the urgent need for systematic investigation. This study aims to address two core scientific questions by constructing a multi-element collaborative analytical framework: (1) to reveal the spatiotemporal change patterns and driving mechanisms of wetland water quality under the dual stress of climate change and human activities; (2) to analyze the combined impact of hydrological regime shifts and land use pattern changes on vegetation community structure and benthic species communities. [Methods] This study integrated multi-source data fusion and spatiotemporal coupling analysis techniques. Six typical monitoring sites were selected, covering three types of habitats: dish-shaped lake areas, tailing areas, and flood detention areas. Water quality parameters (e.g., DO and TP, six indicators in total) and benthic species data were obtained through continuous observations during three hydrological periods (normal, flood, and dry seasons) in 2024. Remote sensing image interpretation was used to obtain land use changes and vegetation conditions. Based on water quality index (WQI), Pinkas’ index of relative importance (IRI), and other methods, the spatiotemporal change characteristics of the wetland ecosystems were systematically analyzed. [Results] (1) The WQI of the Poyang Lake floodplain wetlands was influenced by both temporal and spatial scales. Temporally, it exhibited a migration pattern of pollutants characterized by “dilution in the flood season and enrichment in the dry season”. Spatially, it exhibited a gradient pattern of “poorer conditions in the upper and middle reaches and better conditions in the lower reaches”, with the best water quality observed in the dish-shaped lake areas, while the overall wetland water quality reached the “good” level (60<WQI≤80). Changes in land use patterns led to water quality deterioration during the dry season, and the expansion of farmland in the western region was spatially coupled with areas of water quality deterioration. (2) The vegetation community structure of the Poyang Lake floodplain wetlands deteriorated from 2023 to 2024. The high-density vegetation coverage area (NDVI≥0.7) nearly disappeared in 2024, and the area of the medium-density zone (0.2≤NDVI<0.5) decreased by 12.7%. Vegetation degradation was significant, while overall vegetation coverage increased by 38%. The benthic species communities were significantly influenced by hydrological conditions. Except during the dry season, there were notable interannual variations in the dominant benthic species. Spatially, it was affected by human activities, with community distribution in areas of frequent human activities being lower than that in natural ecological areas. [Conclusion] This study identifies three types of ecological problems in the Poyang Lake floodplain wetlands. The first is the “water quality imbalance under the combined effects of hydrological regimes and human activities”, characterized by significant seasonal variations in pollutants, following a pattern of “dilution in the flood season and enrichment in the dry season”. The second is “degradation of biological community structure and decline in ecological functions”, characterized by deterioration of vegetation community structure, disappearance of high-density areas, reduction of medium-density areas, and lower biomass of benthic species in areas with frequent human activities compared with natural ecological areas. The third is “conflict between land use and ecological functions”, characterized by adverse changes in land cover, forming a positive feedback chain of “farmland encroachment-non-point source pollution-vegetation degradation”. A coordinated governance system of “hydrological regulation-ecological restoration-social participation” is proposed to address these three types of problems. In future, the monitoring scope can be further expanded, and long-term research on the response of wetland ecology to climate change can be strengthened to provide more comprehensive scientific support for sustainable wetland management in the context of the Yangtze River protection strategy.

[Objective] Rural ditches are major pathways through which agricultural nitrogen and phosphorus pollutants enter surface waters. Ditch ecological landscape systems typically consist of multiple interconnected units, including buffer zones, constructed wetlands, and ecological ponds. The overall spatial allocation of these systems critically determines their performance. This study addresses this issue by developing a methodological framework for optimizing the spatial allocation of ditch ecological units in plain regions, thereby overcoming subjectivity and the lack of theoretical and data-driven approaches in traditional designs. [Methods] Representative rural ditches in the Chezhegou watershed of the Huaibei Plain were selected for the spatial optimization of ecological units. A coupled modeling framework was developed in MATLAB, integrating a spatial optimization model of rural ditch ecological units with pollutant proxy functions. The computational procedure involved three key steps: (1) spatial parameters of suitable construction areas for ecological units at each node were input together with hydrological and water quality data under rainfall scenarios; (2) proxy functions were developed using multiple linear regression based on simulation data from 13 ecological units; and (3) a cost-constrained optimization model was developed to maximize pollutant removal efficiency under practical budget limitations. Using TN and TP as key performance indicators, the model aimed to optimize multiple pollutant reduction in rural ditch systems while satisfying prescribed cost constraints. Optimization was conducted using a bi-level particle swarm optimization (BPSO) algorithm to obtain the optimal allocation solution. [Results] (1) Implementation of ecological landscape systems effectively reduced the total pollutant load within rural ditch systems. Although higher construction costs improved pollutant removal efficiency, diminishing marginal returns on investment were observed. Specifically, the incremental improvement in purification efficiency per unit investment decreased progressively with additional spending.(2) Comprehensive analysis under different budget scenarios indicated that buffer zones B and C, together with wetlands D, C, G, and E, achieved superior pollutant reduction performance in the Huaibei Plain, providing valuable guidance for future rural ditch management strategies.(3) This study proposed a novel optimization framework for the spatial allocation of rural ditch ecological units. By integrating optimization algorithms with proxy functions, the framework reduces the subjectivity and empirical limitations of traditional design approaches. The method improved the scientific rigor of spatial allocation schemes and enhanced pollutant removal efficiency across multiple scenarios, demonstrating its feasibility and effectiveness. [Conclusion] The effectiveness of integrating the BPSO algorithm with proxy functions for optimizing the spatial allocation of ditch ecological units is demonstrated. This approach overcomes the limitations of previous designs, including subjectivity and limited theoretical and data support. Nevertheless, several challenges remain, including (1) high data demands, as the model requires extensive preprocessing and detailed input parameters for the target area; (2) uncertainty-related limitations, since simplifications are still necessary to accommodate uncertainties in pollutant removal simulations and surface runoff dynamics in plain regions; and (3) scalability constraints, as large-scale applications may encounter data scarcity and computational challenges due to the extensive and complex nature of rural landscapes. Future research should prioritize the development of high-resolution terrain and land-use databases tailored to rural environments, aim to streamline data requirements for the ecological unit spatial allocation module, and enhance the computational efficiency and generalizability of the optimization framework.

[Objective] This study aims to conduct a scientific and objective dynamic assessment of ecological quality in megacities to monitor the spatiotemporal changes and to analyze the effects of land use transition on ecological quality, thereby providing insights and recommendations for addressing the safety and ecological issues arising from spatial expansion and spatial factor aggregation in megacities. [Methods] We selected the urban area of Wuhan, Hubei Province, which was newly designated as a megacity in 2022, as the research subject. First, we collected Landsat remote sensing images, digital elevation model (DEM), land use data, and other required datasets from reliable online scientific repositories. Subsequently, the remote sensing ecological index (RSEI) method was applied to systematically process and analyze the remote sensing images to extract the spatiotemporal dynamics of urban ecological quality. Second, Moran’s I was used to perform spatial autocorrelation analysis of the RSEI results to quantify the spatial dependence and clustering characteristics of ecological environment changes, enabling the identification of hotspots and coldspots of ecological quality changes. Finally, ecological quality changes were spatially coupled with land use change data using spatial overlay analysis and statistical correlation methods to derive the quantitative relationship between spatiotemporal changes in ecological quality and land use transition processes. [Results] (1) During the study period, Wuhan’s overall ecological quality exhibited a fluctuating upward trend, with the mean value increasing from 0.57 in 2014 to 0.63 in 2023. The improvement was most pronounced from 2014 to 2017, when the mean RSEI rose from 0.57 to 0.64. (2) Moran’s I for Wuhan’s ecological quality was 0.32, and the “high-high” clusters in the local spatial autocorrelation analysis exhibited spatial continuity, indicating that the ecological quality of Wuhan showed a pronounced spatial clustering pattern. (3) Ecological degradation was mainly concentrated on the periphery of the central urban area, indicating that construction expansion in Wuhan contributed to an overall decline in ecological quality. Meanwhile, ecological quality improved along the shorelines at the confluence of the Yangtze River and the Han River and around wetlands such as East Lake and Liangzi Lake, demonstrating the effectiveness of Wuhan’s ecological restoration initiatives. (4) Analysis of ecological quality changes across land use types further showed that disparities within Wuhan’s built environment widened during the study period. Specifically, the gap in ecological quality between construction land and cultivated land increased from 0.34 in 2014 to 0.38 in 2023, suggesting that the ecological cost of converting cultivated land to construction land increased. [Conclusion] (1) Wuhan’s riverbank and wetland restoration activities have a significant positive impact on ecological quality improvement. Therefore, future efforts should continue to promote ecological governance initiatives such as landscape enhancement in urban renewal areas, riverbank protection, and wetland conservation. (2) In subsequent ecological governance, Wuhan should, while following socioeconomic development, consider the spatial agglomeration characteristics of regional ecological quality changes and adopt region-specific measures for hotspots with sharp ecological degradation, such as appropriate artificial restoration and landscape enhancement. (3) From the perspective of ecological quality advancement, Wuhan, as a megacity, should place greater emphasis on intensive urban development by slowing its expansion pace in line with socioeconomic needs and promoting the ecological renewal of existing urban built-up spaces to improve the ecological quality of human settlements. (4) The data indicate a significant ecological quality gap between cultivated land, forest land, and other ecological spaces and construction land. Therefore, Wuhan should strengthen the supervision and protection of cultivated land and forest land during urban construction and development to mitigate substantial ecological losses arising from land transition.

[Objective] To address the lack of carbon footprint accounting and insufficient multi-objective synergy in evaluating existing gray-green infrastructure in Sponge Cities, this study proposes a game theory-based method for life-cycle synergistic optimization evaluation of water-carbon-economic performance. [Methods] By analyzing the synergistic relationships among water environment improvement, carbon emission reduction, and economic cost over the life cycle of gray-green infrastructure, a three-dimensional (3D) indicator system—“water environment-carbon reduction-economic cost”—was developed. This system integrated key indicators such as runoff reduction rate, pollutant removal rate, life-cycle carbon emissions, and economic cost. The entropy weighting method and the analytic hierarchy process (AHP) were integrated with a game theory model to optimize indicator weights based on multi-source weighting and multi-criteria decision-making theory. The Nash equilibrium was applied to balance conflicting objectives, and the TOPSIS method was employed for the comprehensive evaluation of multiple schemes. [Results] The main campus of Hebei University of Water Resources and Electric Engineering was selected as a case study, with seven gray-green infrastructure combination schemes designed. The results indicated that Scheme 5 (a combination of storage tank, sunken green space, and rain barrel) achieved effective runoff reduction, pollutant removal rates above 48%, low economic cost, and a significant carbon sink effect, demonstrating the best overall performance. The subsequent ranking of schemes was: Scheme 3, Scheme 7, Scheme 6, Scheme 1, Scheme 4, and Scheme 2. Sensitivity analysis confirmed that Scheme 5 exhibited good stability. [Conclusion] Case study indicates that, in the game theory-based comprehensive weighting model, the carbon emission indicator carries the highest weight. This highlights the critical importance of advancing low-carbon development goals within the current decision-making framework. Concurrently, the study reveals a significant divergence in the weighting of the life-cycle cost indicator between subjective and objective weighting methods. This reflects inherent differences arising from distinct evaluation perspectives—namely, expert judgment versus quantitative data. Notably, the advantage of the game theory model lies in its ability to integrate and balance the contributions of these two methods through an equilibrium optimization mechanism, thereby effectively mitigating potential systemic biases inherent in single weighting methods. Importantly, water environment indicators, such as runoff reduction rate and pollutant removal rate, play an essential “bottom-line” role within the entire evaluation system. In pursuing low-carbon goals, these critical water environment performance indicators cannot be compromised, and the core requirements for water environment management must be strictly maintained. This research addresses the limitations of traditional methods that overemphasize technology at the expense of synergy, providing methodological support for transforming and upgrading Sponge Cities from “engineering compliance” to achieving “synergistic benefits in water-carbon-economic performance”. It provides both theoretical foundations and practical pathways for promoting low-carbon development of Sponge Cities and facilitating their synergy with the “dual carbon” goals (carbon peaking and carbon neutrality).

[Objective] The eastern Gansu Province is an important ecological transition zone and a fragile area on the Loess Plateau, and understanding the dynamic variation mechanisms of vegetation NDVI (Normalized Difference Vegetation Index) provides a crucial basis for regional ecological restoration. [Methods] This study investigated the response of vegetation NDVI to climate change and human activities in the eastern Gansu based on MODIS NDVI, climate, and land use data from 2000 to 2024, using methods including Theil-Sen trend analysis and the Hurst exponent. [Results] (1) Vegetation NDVI in the eastern Gansu exhibited a spatial pattern of “high in the southeast and low in the northwest”, and areas with significant improvement accounted for 54.74%. However, the Hurst exponent (0.35-0.65) indicated that the future improvement trend had weak persistence. (2) Human activities were the dominant driver, with a contribution rate exceeding 80% in 57.53% of the area, mainly influenced by the Grain for Green program (2 248 km² of cropland converted to grassland) and urbanization (an increase of 35.14% in the urbanization rate). The contribution rate of climate change was mainly in the 0%-20% range (45.04% of the area), and improved hydrothermal conditions (precipitation increased by 180.95 mm) provided essential support for vegetation growth. (3) A total of 86.68% of the area was jointly driven by climate and human activities, forming a distribution pattern characterized by “human activities as the primary driver and climate as the supporting factor”. [Conclusion] From 2000 to 2024, vegetation NDVI in the eastern Gansu showed a significant improving trend, but with obvious spatial differentiation. The improvement is mainly attributed to the strong driving effect of human activities. However, its rapid intervention leads to weak future sustainability of the ecosystem, posing a significant risk of “degradation after greening”.

[Objective] As a hotspot region of soil respiration and carbon pool dynamics, the Three Gorges Reservoir area is most extensively covered by Pinus massoniana forests, whose soil organic carbon storage is the largest among all forest types. Therefore, investigating soil carbon release is particularly important. Soil carbon emissions are mainly regulated by microbial decomposition of aboveground litter, organic matter substrates, and root exudates; however, studies on the coupling relationship between soil respiration and microorganisms in Pinus massoniana forests in the Three Gorges Reservoir area are scarce, which affects the accurate quantification of the reservoir-area carbon pool. [Methods] This study used a Li-8100 automated soil CO₂ flux system (Li-Cor Inc., Lincoln, NE, USA) and the chloroform fumigation-extraction method (FE) to monitor soil respiration rates and microbial biomass carbon and nitrogen in two Pinus massoniana forest types (a Pinus massoniana pure forest and a Pinus massoniana-Quercus acutissima mixed forest) across spring, summer, autumn, and winter. The trenching method was further used to determine the contributions of autotrophic and heterotrophic respiration components, and one-way analysis of variance was used to analyze differences. [Results] Both total respiration and heterotrophic respiration rates in the mixed forest were higher than those in the pure forest. Under both forest types, heterotrophic respiration accounted for an average of 88%, while autotrophic respiration accounted for an average of 12%, which was also a consequence of Pinus massoniana being the main constructive or dominant species in the Three Gorges Reservoir area. The proportions of autotrophic and heterotrophic respiration exhibited significant seasonal variation: the contribution of heterotrophic respiration first decreased and then increased with season, whereas autotrophic respiration first increased and then decreased. Autotrophic respiration contributed approximately 3%-25% to total soil carbon release. In the pure forest, heterotrophic respiration contributed 75%-97% of total soil carbon release, while in the mixed forest, heterotrophic respiration accounted for 82%-98% of total soil respiration. During the growing season (May-October), the average rates of all respiration components were higher and reached their maximum in summer. Microbial biomass carbon and nitrogen contents in the mixed forest were higher than those in the pure forest, reaching 259.54 and 20.25 mg/kg, respectively. After root exclusion treatment, microbial biomass carbon and nitrogen only decreased by 30.53% and 34.56%, respectively. The microbial biomass C to N ratio was 15.70 in the pure forest and 12.82 in the mixed forest. Both microbial biomass carbon and the C to N ratio drove soil carbon release. [Conclusion] In both Pinus massoniana pure and mixed forests, the contribution of heterotrophic respiration is much higher than that of autotrophic respiration, indicating that heterotrophic respiration is the main pathway of soil carbon release in the Three Gorges Reservoir area. After root exclusion treatment, the decreases in microbial biomass carbon and nitrogen are relatively small, suggesting that microorganisms mainly release carbon by decomposing litter and organic matter substrates rather than root exudates. Soil respiration, in both pure and mixed forests, is significantly positively correlated with microbial biomass carbon and the C to N ratio (P<0.05), but is not correlated with microbial biomass nitrogen. The positive correlation and similar patterns between microbial biomass carbon and soil respiration can directly reflect soil carbon release. Microbial biomass in the mixed forest is higher than that in the pure forest both before and after root exclusion, resulting in greater soil carbon emissions. In the absence of roots and their exudates, the C to N ratio in the mixed forest increases to facilitate the decomposition of more recalcitrant substrates. The findings of this study provide an important reference for research on carbon cycling and ecological construction in the Three Gorges Reservoir area.

[Objective] This study aims to explore the role of river riparian zones in southern China as sources or sinks of greenhouse gases during winter. Traditional studies often focus on individual greenhouse gases, lacking simultaneous observation and comprehensive assessment of multiple greenhouse gases such as CO₂, CH4, and N₂O. Therefore, the core objectives of this study are: (1) to quantify the winter fluxes of CO₂, CH₄, and N₂O under three common riparian herbaceous plants (Ophiopogon japonicus, Allium tuberosum, and Cynodon dactylon) and in bare soil control plots; (2) to comprehensively assess the contribution of different vegetation types to the net winter greenhouse effect in riparian zones based on the global warming potential (GWP) model; (3) to identify the key environmental drivers affecting greenhouse gas fluxes; and (4) to provide a scientific basis for vegetation selection and ecological management in southern riparian zones from the practical perspective of promoting “carbon neutrality”. [Methods] This study took the riparian zone of the Xiongxi River, a typical river in southern China, as the study area. Three widely distributed and representative herbaceous plant communities, along with bare soil as control areas, were selected. Throughout the winter, on one sunny day in the middle of each month, high-precision LI-7810 and LI-7820 trace gas analyzers were used for in-situ simultaneous observations to obtain flux data for the three greenhouse gases. Meanwhile, key environmental parameters such as air temperature, soil temperature, and soil moisture were synchronously recorded. To integrate the overall impact of the three greenhouse gases on global warming, the global warming potential model was adopted. On a 100-year time scale, with CO₂ as the reference, all fluxes were uniformly converted into CO₂ equivalents, thereby obtaining the daily comprehensive GWP for each study area. Data analysis was conducted using statistical methods including one-way analysis of variance (ANOVA), Pearson correlation analysis, and regression analysis. [Results] Herbaceous plants significantly reduced the net carbon emissions in riparian zones during winter. After comprehensive assessment of CO₂, CH4, and N₂O, significant differences were found in winter GWP values across different areas. The average GWP in the Cynodon dactylon area, Ophiopogon japonicus area, Allium tuberosum area, and bare area was 3 817.77±249.24, 3 963.31± 265.66, 6 876.89±536.17,8 653.71±756.08 mg/(m²∙d), respectively. Although all areas functioned as net carbon sources during winter, the GWP was effectively reduced in the three herbaceous plant-covered areas compared to bare land. This result, for the first time, quantified the mitigation effect of herbaceous plants on the greenhouse effect of riparian zones under a winter, multi-gas comprehensive assessment framework. The impact of different vegetation types on greenhouse gas composition was species-specific. In-depth analysis of each gas component showed that CO₂ emission fluxes in all vegetated areas were significantly lower than in bare land. CH₄ fluxes mostly exhibited weak absorption, with the lowest average in bare areas and the highest in Ophiopogon japonicus areas. Regarding N₂O flux, bare areas showed the highest average, while the Cynodon dactylon areas had the lowest. Observations also indicated a distinct diurnal variation in riparian GWP, with higher values at noon and lower values in the morning and evening. Pearson correlation analysis revealed that soil temperature was the key environmental factor driving this diurnal pattern, showing a highly significant positive correlation with the GWP value. This finding clarified the central role of temperature in regulating the carbon emission process of riparian zones in winter. [Conclusion] (1) This study overcomes the limitations of traditional single-gas studies, systematically revealing for the first time in southern China’s winter riparian environment that common herbaceous plants significantly and differentially influence regional net greenhouse effects by altering CO₂, CH₄, and N₂O emission profiles. It confirms that vegetation cover in winter also has a certain emission-reduction function.(2) From the perspective of the synergy between riparian ecological engineering management and carbon neutrality goals, vegetation selection is crucial. Among the three plants examined in this study, Cynodon dactylon proves to be the optimal choice in winter due to its lowest GWP, whereas Allium tuberosum, though visually appealing, has the highest GWP and is therefore not recommended for planting from an emission-reduction perspective.(3) Soil temperature is the key environmental factor controlling the diurnal variation of winter greenhouse gas fluxes in riparian zones. This implies that under future global warming, rising winter temperatures may significantly enhance the carbon emission intensity of such ecosystems and should be fully considered in carbon cycle models.

[Objective] Clarifying dynamic changes of vegetation activities and time lag in response to hydrothermal conditions in Tianjin can provide a scientific basis for regional ecological environment management and sustainable development. Previous studies have investigated urban vegetation dynamic differentiation based on different data sources and time scales, while spatiotemporal patterns of vegetation over long time series, as well as the direction and extent of vegetation response to changes in hydrothermal conditions, still remain uncertain. Most current studies lack specific quantification of the lag duration of climate change. [Methods] This paper took the MODIS13 dataset, air temperature, and precipitation dataset of Tianjin from 2000 to 2022 as research objects. Based on the MatLab platform, methods such as the Hurst index, Theil-Sen trend analysis, Mann-Kendall test, geographic information system (GIS) spatial analysis, and time-lagged partial correlation analysis were adopted to investigate the characteristics of vegetation dynamics and their response to hydrothermal effects in Tianjin over the past 23 years. Additionally, this study analyzed vegetation evolution characteristics and their response to climate change, providing references for understanding ecological environment response under climate change. [Results] The results showed that: (1) annual average NDVI in Tianjin was 0.782, showing an overall trend of first increasing and then decreasing. Areas with high vegetation cover were mainly distributed in northern Jizhou District, northern Baodi District, and Ninghe District. The intra-annual fluctuation trend showed a certain positive correlation with changes in temperature and precipitation. (2) The mean Hurst index for the entire city was 0.493, with 45.225% of the areas having a Hurst index >0.5. Overall, vegetation in Tianjin showed a trend of past degradation but future improvement. Areas with continuous NDVI degradation were mainly distributed in Xiqing District, Ninghe District, and Dongli District. (3) 10.943% and 61.408% of the areas in Tianjin had time-lag effects on temperature and precipitation, respectively. The average lag time of vegetation response to temperature across the city was 2.737 months. The vegetation response to precipitation had a time lag of 1 to 3 months, with an average lag time of 1.016 months. Overall, vegetation was more sensitive to precipitation, and the average lag time of vegetation response to precipitation in the city was shorter than that to air temperature. (4) The responses of different vegetation types to air temperature and precipitation varied. Broad-leaved forests had the shortest response time to precipitation, while herbaceous cover had the longest response time. Sparse vegetation had the fastest response to air temperature, and broad-leaved forests had the slowest response. [Conclusion] From 2000 to 2022, the overall vegetation cover level in Tianjin was good, with NDVI showing a trend of first increasing and then decreasing, indicating past degradation but future improvement. The correlation between precipitation and vegetation is higher, and the lag time of air temperature is longer. Vegetation in Tianjin exhibits lag response characteristics to both air temperature and precipitation, and lag time varies among different vegetation types.

[Objective] The Three-North Shelterbelt Program represents a pivotal ecological conservation initiative in China. However, over the past decade, varying degrees of degradation and functional decline have been observed in shelterbelt forests across the region. Further research is warranted to explore the process by which water affects tree degradation and the overall decline of the Three-North Shelterbelts. [Methods] To elucidate the role of water availability in driving tree degradation and to unravel the mechanisms underlying shelterbelt decline, the Populus simonii shelterbelts in northern Hebei Province were taken as the research subjects. Tree-ring samples of P. simonii with different degradation degrees from the same area were collected. Using tree basal area increment (BAI) and multi-year meteorological data, the degradation processes of P. simonii shelterbelts with different degradation degrees and their differential responses to drought events were analyzed. Based on tree-ring carbon isotope technology, the changes in intrinsic water use efficiency (iWUE) of P. simonii were examined. Additionally, combined with the ecosystem resilience index (ERI), the possible reasons for why some poplar trees in the same area grew normally while others degraded were explored. [Results] (1) The growth period of P. simonii in Zhangbei could be divided into three stages: rapid growth stage (1976-1995), slow growth stage (1996-2005), and declining growth stage (2006-2017). During the rapid growth stage, P. simonii grew stably with a slight increase, and the impact of the external environment on its growth was relatively small. In the slow growth stage, the growth of P. simonii tree-ring width showed a fluctuating trend, and growth differentiation gradually occurred. In the declining growth stage, the tree-ring width of P. simonii showed a steady increase at a gradually decreasing rate, with growth differentiation becoming obvious. (2) ERI quantified the resistance, recovery capacity, and resilience level of trees under external disturbances. Significant differences in the resistance index and resilience index were observed among P. simonii with different degradation degrees: the resistance index and resilience index of non-degraded P. simonii were higher than those of slightly degraded and severely degraded individuals, with these differences being particularly significant during the slow growth stage and declining growth stage of P. simonii. (3) The iWUE, an important physiological indicator for drought adaptation of trees, displayed significant variation across P. simonii with different degradation degrees, and all presented a significant upward trend. Severely and slightly degraded P. simonii demonstrated significantly higher iWUE values than non-degraded trees, while severely degraded P. simonii exhibited significantly higher iWUE values compared to slightly degraded ones. Among P. simonii with different degradation degrees, severely degraded trees experienced the most severe drought stress. [Conclusion] Insufficient and infrequent short-term precipitation, combined with climate warming and drying may be the main causes of shelterbelt degradation. The extreme drought in 1997 and prolonged dry spell from May 1999 to June 2001 likely initiated the decline of P. simonii shelterbelts in Zhangbei County, while persistent drought between September 2006 and August 2012 further exacerbated this deterioration. Differences in the inherent resistance of trees played a critical role in the observed partial degradation and partial non-degradation. Poplars are fast-growing and highly water-consuming species, which mainly cope with water stress by consuming water stored in heartwood. During the rapid growth process of P. simonii, the trees have larger vessels and higher water conductivity. When water stress occurs, some poplar trees with poor resistance suffer from hydraulic failure, which in turn leads to growth decline. In contrast, non-degraded plants may delay the depletion of stored water through the utilization of deep water sources, more flexible stomatal regulation, and more efficient resource allocation.

[Objective] Under the influence of climate change, the rainfall pattern in the Poyang Lake Basin has changed, potentially affecting local soil erosion and subsequently threatening water and ecological security in the basin. However, current research on soil erosion within the basin mostly focuses on historical periods, with relatively limited research on future soil erosion predictions. The lack of clarity regarding future soil erosion dynamics under climate scenarios constrains local soil and water conservation planning and erosion management. To address this gap, future soil erosion predictions are conducted for the Poyang Lake Basin to elucidate its spatiotemporal evolution characteristics under climate change impacts, thereby providing scientific references for local soil and water conservation planning and soil erosion management. [Methods] The SSPs-USLE coupled model at the Poyang Lake Basin scale was developed by integrating the Shared Socioeconomic Pathways (SSPs) and the Universal Soil Loss Equation (USLE) in this study. Tailored to the specific conditions of the Poyang Lake Basin, the SSPs-USLE coupled model was applied to simulate soil erosion both during the historical period (2000-2022) and under three future climate scenarios (SSPs2-4.5, SSPs4-6.0, and SSPs5-8.5) for the period 2030-2060. Through statistical and comparative analysis of the results, the spatiotemporal evolution characteristics of soil erosion under different future scenarios were elucidated. The underlying causes were further analyzed based on existing literature, thereby providing targeted measures and recommendations. [Results] Temporally, the total area affected by soil erosion in the Poyang Lake Basin was projected to decrease in the future, while the total soil erosion volume was expected to increase. Specifically, under the SSPs2-4.5, SSPs4-6.0, and SSPs5-8.5 scenarios, the soil erosion area decreased by 906 km²/a, 916 km²/a, and 912 km²/a, respectively, predominantly occurring in areas with slight intensity erosion. Meanwhile, the total soil loss increased by 2 022.60×10⁴ , 2 098.61×10⁴ and 3 154.35×10⁴ t/a under the same scenarios, mainly affecting areas with moderate or lower erosion intensity. Spatially, the northeast of Poyang Lake Basin in the historical period exhibited severe soil erosion, with a higher proportion of areas classified as strongly eroded or above. In the future, the northwestern and southern regions would experience a significant expansion of strongly eroded or above areas, leading to a more severe overall soil erosion problem in the basin. Among the different socioeconomic scenarios, the SSPs5-8.5 scenario resulted in the most severe soil erosion within the basin, with a total soil erosion volume of 17 247.61 × 10⁴ t/a. The overall erosion intensity shifted from moderate to strong, indicating substantial pressure for future soil erosion control. In contrast, under the SSPs2-4.5 scenario, the basin experienced the least soil erosion, with a total soil erosion volume of 16 115.86×10⁴ t/a. The overall erosion intensity transitioned from moderate to mild, suggesting lower pressure for subsequent soil erosion control. [Conclusion] Future soil erosion in the Poyang Lake Basin is predicted by developing an SSPs-USLE coupled model at the watershed scale, thereby addressing a critical data gap in future soil erosion in this region. The model results show that with the impact of climate change, soil erosion within the Poyang Lake Basin will exhibit an intensifying trend in the future, particularly with increased erosion volumes at areas with slight to moderate erosion intensities. This phenomenon is predominantly attributed to terrain and rainfall, with significant exacerbation concentrated primarily in localized heavy rainfall centers and mountainous/hilly terrain. Besides, among the three future scenarios, the SSPs2-4.5 scenario has the lowest degree of soil erosion deterioration in the watershed, which is a more desirable outcome for the future. Based on this, the local soil erosion control work should be taken seriously, and attention should be paid to addressing slight-to-moderate soil erosion areas in the Poyang Lake Basin. Multiple measures should be implemented in coordination to alleviate the impact of climate change on soil erosion in the basin, and promote social development towards SSPs2-4.5 or even better scenarios.

[Objective] Water-level fluctuation zone (WLFZ) represents a key challenge for managing carbon emissions from global reservoirs. The Three Gorges Reservoir (TGR) has become a key focus for investigating the emission of greenhouse gases, such as carbon dioxide (CO₂). Previous studies have not yielded consistent findings regarding the correlation between different elevations and soil carbon release — a gap that limits an accurate understanding of carbon cycling mechanisms in the reservoir’s WLFZ and hinders effective carbon emission management. [Methods] This study explored soil carbon emission characteristics in the near-dam WLFZ of TGR under fluctuating water levels. Soil respiration rates were measured using the Li-8100 Automated Soil CO₂ Flux System. Two representative WLFZs—Longtanping and Lanlingxi—were selected, and within each area, three elevation intervals were established: below 160 m, 160-170 m, and above 170 m. This design ensured that the data would reflect the impact of water level fluctuations on soil carbon emissions across different WLFZ segments. One-way analysis of variance (ANOVA) in SPSS 25.0 was applied to examine differences in soil respiration across elevations and seasons. [Results] No positive correlation was found between elevation and soil respiration. Instead, as elevation increased, soil respiration across the entire study area exhibited a trend of first rising and then falling, with the maximum rate observed under moderate flooding stress. Specifically, the peak soil respiration rate reached 3.91 μmol/m²/s in Longtanping and 2.69 μmol/m²/s in Lanlingxi, with an average of 3.30 μmol/m²/s. This suggested that moderate flooding created optimal conditions for soil microbial activity and organic matter decomposition—two processes that drove carbon emission—whereas excessive or insufficient flooding inhibited these biological activities, reducing respiration rates. When the two WLFZs were analyzed comprehensively and Lanlingxi individually, no significant difference in soil respiration was found between the below-160 m and above-170 m intervals. However, in Longtanping, soil respiration above 170 m was slightly higher than that below 160 m. This regional discrepancy might be attributed to differences in local environmental factors, such as soil texture, organic matter content, vegetation coverage, or microbial community composition. Soil respiration exhibited significant temporal variability. Overall, the seasonal trend showed rates in July and August being highest, followed by September, June, and May. Minor differences existed between the two WLFZs: Longtanping showed a pattern where rates in July and August were highest, followed by September and June, and then May, while Lanlingxi displayed a pattern where rates in July, August, and September were equal and higher than June and May. Nevertheless, both areas recorded their peak soil respiration in August, with the highest rates occurring in the 160-170 m interval: 6.97 μmol/m²/s in Longtanping and 4.58 μmol/m²/s in Lanlingxi. The elevated summer respiration rates (especially in July and August) were primarily linked to vigorous vegetation growth and metabolic activity during this period. Vegetation contributed to carbon emission by releasing organic matter through root exudation and litterfall (providing substrates for microbes) and enhancing soil aeration via root respiration (facilitating microbial decomposition). [Conclusion] Moderate dry-wet alternation (i.e., moderate flooding stress) maximizes soil carbon emissions in the study area, while extreme flooding (either too high or too low) suppresses emission intensity. Summer, characterized by robust vegetation growth and metabolism, shows significantly higher soil respiration than other seasons—with July and August showing particularly high rates, and the moderately flooded zones in August recording the peak. The findings of this study have both theoretical and practical value. Theoretically, they enhance the understanding of carbon cycling in large reservoir WLFZ and contribute to global carbon cycle research. Practically, they provide a scientific basis for the quantitative analysis of carbon emissions in the Three Gorges Reservoir’s WLFZs and support future studies on carbon cycling following WLFZ ecological restoration. This information can further guide water level management strategies to regulate soil carbon emissions, aiding global carbon neutrality efforts and the sustainable development of the reservoir ecosystem.

[Objective] Taking Wannian County in Jiangxi Province as a representative case, this study presents the analysis results of the pilot projects on soil and water conservation supervision for agricultural and forestry development and other production and construction activities in five counties (or cities) across four provinces in the middle reaches of the Yangtze River. This study aims to assess the current status of these activities and their soil and water conservation supervision, explore regulatory technologies and methods, and invesstigate effective institutional mechanisms for supervision. [Methods] We employed 3S technology, automated image recognition technology, computer technology, database technology, wireless networks, and mobile terminals, together with field verification, surveys, and spatial analysis. Key technologies included the automatic extraction of remote sensing information, enabling fast, automatic, and accurate identification of disturbance patches and soil erosion problem patches. Based on GIS spatial analysis and processing functions, approved production and construction projects were automatically excluded, and relevant information of agricultural and forestry development was automatically integrated. Additionally, a regulatory app was developed. [Results] (1) The disturbance patches of production and construction activities exhibited high accuracy. Through field verification of 910 patches with an area ≥ 1 hm², only 28 patches with a total area of 108.89 hm² were identified as actual production and construction projects. The automatic extraction accuracy for disturbance patches and total area reached 96.92% and 98.41%, respectively. (2) The disturbance caused by agricultural and forestry development was significant. In 2023, a total of 1 048 disturbance patches were extracted in Wannian County, with a total area of 6 924.60 hm², accounting for 6.07% of the county’s land area. The density of disturbance patches reached 0.92/km². (3) The scale of disturbance was generally large. The average area of disturbance patches was 6.61 hm², among which 910 patches were over 1 hm², with a total area as high as 6 859.12 hm². (4) Regarding spatial distribution, agricultural and forestry development and other production and construction activities in 2023 were distributed across the entire Wannian County, generally showing a uniform distribution pattern, with slightly more disturbance patches in the east than in the west. (5) In terms of types, the main activities included economic forest projects, land consolidation projects, farmland improvement projects, and land requisition-compensation balance projects. (6) An analysis of investment entities revealed that over 93% were projects or subsidized programs under governmental forestry, natural resources, rural and agriculture, and related departments. (7) Approximately 78% of the production and construction activities had not implemented effective soil and water conservation measures, posing significant soil erosion risks. Furthermore, soil and water conservation supervision was largely absent in practice. [Conclusions] Given the high intensity of agricultural and forestry development activities, limited implementation of conservation measures, and high risks of severe soil erosion, it is essential to strengthen soil and water conservation supervision for these activities, particularly for government-funded projects. Regulatory measures for soil and water conservation in such activities should be developed, supervision systems and mechanisms featuring “industry-based regulation and coordinated soil and water conservation” should be established, and categorized supervision should be implemented.

[Objective] Dry-hot valley regions are characterized by fragile ecological environment and severe soil erosion. Clarifying the differences in soil anti-scourability and the influencing factors under different ecological restoration models is crucial for revealing the soil anti-scourability mechanism and optimizing ecological restoration measures in this region. [Methods] The drawdown zone of Wudongde Hydropower Station in the dry-hot valley of the Jinsha River was selected as the study area. Three typical ecological restoration models were designed, namely tree forest land, slope-to-terrace + farmland, and shrub-grassland. Undisturbed soil samples were collected from three soil layers (0-20 cm, 20-40 cm, and 40-60 cm), and anti-scourability tests were conducted. The anti-scourability indices and runoff sediment amounts of each soil layer under different models at different scouring times were measured. Physicochemical indicators such as soil bulk density, water content, and particle composition were determined through laboratory experiments, and the influencing factors of soil anti-scourability were identified through correlation analysis. [Results] (1) Different ecological restoration models and soil layer depths significantly affected soil anti-scourability. The anti-scourability indice of tree forest land was the largest (0.566 L/g), followed by slope-to-terrace+farmland (0.501 L/g) and shrub-grassland (0.428 L/g). The total runoff sediment yield exhibited an opposite trend, with the shrub-grassland showing the highest value, 28.03% higher than that of the tree forest land. As soil depth increased, the anti-scourability indices of all three ecological restoration models demonstrated significant declining trend. For all three models, the runoff sediment concentration dropped rapidly during the initial scouring period (0-6 min) and stabilized after 6-10 minutes, while the anti-scourability indices exhibited regular temporal patterns that could be fitted by either quadratic or power functions(R²> 0.92 in all cases).(2) Significant differences in soil particle composition and particle fractal dimension were observed among the three models, reflecting variations in soil structural stability. Coarse silt (35.82%-46.10%, mean 41.85%) dominated the particle composition, while coarse sand (0-1.93%, mean 0.42%) was the least abundant fraction. The contents of clay, coarse clay, and fine silt followed the order of shrub-grassland > slope-to-terrace + farmland > tree forest land, whereas fine sand and coarse sand showed the opposite trend, with the highest values in the tree forest land and the lowest in the shrub-grassland. The soil particle fractal dimension ranged from 2.540 to 2.648, with the shrub-grassland exhibiting the highest values, followed by slope-to-terrace + farmland and then tree forest land (all differences significant), indicating that the tree forest land’s soil structure is more stable, which is favorable for soil anti-scourability. (3) Anti-scourability index exhibited significant correlations with multiple physicochemical indicators. Negative correlations were observed between anti-scourability index and soil bulk density, fine clay, coarse clay, fine silt, coarse silt, cumulative eroded soil mass, and fractal dimension, whereas positive correlations were found with fine sand and coarse sand contents. Water content showed a positive correlation with anti-scourability index during the early scouring stage (1-6 min) but turned negative in the later stage (7-10 min). Among these factors, fine clay content and particle fractal dimension demonstrated the most pronounced influences on the anti-scourability index. [Conclusions] Among the three typical ecological restoration models in dry-hot valley regions, tree forest model effectively enhances soil anti-scourability, followed by slope-to-terrace + farmland model. Soil particle composition and structural characteristics significantly affect anti-scourability performance, with fine clay content and particle fractal dimension being the dominant factors. For future ecological restoration measures in drawdown zones, it is recommended to prioritize tree-dominated and tree-shrub-grass composite configuration, tailored to regional topography and soil structural features, to improve soil anti-scourability.

[Objective] Red soils are widely distributed in Yunnan Province, leading to prevalent ecological issues such as soil degradation, runoff erosion, and vegetation deterioration in the region. Under alternate wetting and drying conditions formed by rainfall, high temperature, and evaporation, red soil bodies are prone to structural deformation, shrinkage cracking, surface erosion, and overall instability. This study aims to reveal the mechanism by which glutinous rice gel reconstruction affects the water retention characteristics of red soil under alternate wetting and drying conditions. [Methods] Four gradients of glutinous rice gel concentration levels were designed: 0% (control group), 0.5%, 2.5%, and 5.0%. At each concentration level, two ring cutter samples (separated by filter paper) were prepared, with three replicates for each concentration, resulting in a total of 24 test samples. Ten groups of glutinous rice gel-reconstructed soil samples with different moisture contents were prepared using the gravimetric method, with moisture content gradients evenly distributed from the air-dried state (4.1%) to the saturated state (42.0%). Five equally spaced moisture content gradients were set for each wetting-drying cycle. Two complete cycles of alternate wetting and drying were performed. Matric suction was measured using the filter paper method. By achieving moisture balance exchange between the filter paper and the soil samples, the matric suction of the soil samples was determined based on the standard relationship between the filter paper’s balance moisture content and suction values. Parameter fitting of the soil-water characteristic curve (SWCC) was performed based on the Logistic model. [Results] Alternate wetting and drying significantly influenced soil matric suction. The matric suction of plain soil decreased by 79.43%, while the glutinous rice gel-reconstructed soil exhibited notable protective effects, with the concentration level of 5.0% demonstrating optimal performance and only decreasing by 8.56%. Hysteresis analysis of the SWCC showed that glutinous rice gel effectively suppressed the hysteretic effects caused by alternate wetting and drying. At the concentration level of 5.0%, the hysteresis degrees of the first and second cycles were reduced by 80.76% and 72.42%, respectively, significantly outperforming plain soil (p<0.01). The Logistic model exhibited high fitting accuracy for SWCC (R²>0.99). Parameter analysis indicated that the 2.5% concentration level exhibited optimal water retention performance during the drying phase, while the 5.0% level performed best during the wetting phase. During alternate wetting and drying, the air-entry value and residual value of the glutinous rice gel-reconstructed soil showed regular differences. With increasing cycle numbers, the air-entry value of the sample with 5.0% concentration level decreased by only 36.64% (95% in the control), while the residual value decreased by only 20.24% and 25.43% during drying and wetting, respectively, demonstrating excellent stability. [Conclusions] The incorporation of glutinous rice gel significantly enhances the water retention capacity and matric suction maintenance of red soil, with the 5.0% concentration level demonstrating optimal performance in suppressing suction reduction, followed by 2.5% and 0.5%. Although alternate wetting and drying causes pronounced hysteresis effects in the SWCC of glutinous rice gel-reconstructed soil, higher concentration levels of glutinous rice gel significantly reduce the hysteresis degree and moisture content variation amplitude. The data reveal a significant negative correlation between glutinous rice gel concentration and hysteresis degree (R²=0.92). The 5.0% sample has the maximum hysteresis reduction and is least affected by alternate wetting and drying. The Logistic model can accurately represent the SWCC parameters of glutinous rice gel-reconstructed soil (R²>0.99). Notably, the sample of 2.5% concentration level shows optimal water retention performance during the drying phase, while the 5.0% sample shows the strongest water absorption capacity during the wetting phase, both significantly outperforming the plain soil control group (p<0.01). With increasing numbers of alternate wetting and drying cycles, both the air-entry value and residual value of the soil exhibit decreasing trends. However, the decline in the air-entry value of glutinous rice gel-reconstructed soil is significantly reduced (the 5.0% group decreased by 63% compared to the control group), and the decline rate of residual value tends to stabilize as cycle numbers increase. The residual values of the samples with 5.0% concentration level decrease by 20.24% and 25.43% during drying and wetting phases, respectively, showing optimal water retention stability. Further in-depth research is required on the degradation rate of glutinous rice gel, number of cycles, time variations, and how these affect the properties of red soil and subsequently alter its matric suction.

[Objective] Water and soil loss on cultivated land is characterized by high erosion intensity and poor capacity of soil to retain water, conserve soil, and maintain fertility. Currently, national dynamic monitoring results on water and soil loss cannot be fully applied to the comprehensive management of water and soil loss on cultivated land. Based on existing national dynamic monitoring results on water and soil loss, this study proposes a multi-scale identification method using aggregation analysis to prioritize comprehensive management targets for cultivated land water and soil loss. Priority levels are determined for each treatment unit, providing technical support for efficient and precise evaluation and management planning. [Methods] This study selected Yuexi County in Sichuan Province as the research area. Through spatial overlay analysis of land-use raster data and soil erosion intensity raster data, the data reclassification, regional merging, and removal of small patches were performed to construct contiguous management zones. Depending on water and soil loss characteristics, cultivated land distribution patterns, and patch fragmentation degree, the study extracted cultivated land management targets of varying sizes and calculated their respective erosion grid ratios. A composite evaluation index was then derived by multiplying three graded indices: soil erosion grid ratio, management area level, and average slope level. The comprehensive management priorities were ultimately determined according to the evaluation index values. [Results] Using the proposed method, Yuexi County was classified into five comprehensive management zones for cultivated land water and soil loss, effectively covering the main severely affected cultivated areas. As the priority level increased, the land area, proportion of water and soil loss area, and erosion intensity increased. According to the zoning results of cultivated land in Yuexi County, Zone Ⅰ exhibited mild water and soil loss, with limited impact on the county’s overall loss conditions. Zone Ⅱ showed an increase in water and soil loss, with scattered distribution, suitable for decentralized strategies as a short-term comprehensive management area for cultivated land. Zone Ⅲ comprised large, contiguous areas of cultivated land and was the focus for medium- to long-term soil and water loss comprehensive management. Zone Ⅳ had large areas of high-intensity, concentrated erosion and served as the main area for reducing and mitigating soil and water loss in the county. It was a key area for planning medium- to long-term management of cultivated land. Zone Ⅴ suffered from the most severe water and soil loss, with large area, high proportion of high-intensity loss, and great difficulty in treatment. It should be treated as a priority area for intensive, long-term management efforts. [Conclusion] By comprehensively considering slope, loss area, and erosion ratio and setting appropriate thresholds for decision-making factors, the resulting comprehensive management area can effectively cover severely affected cultivated lands in the county. These zones accurately reflect the spatial distribution patterns of water and soil loss and clarify the priority levels of treatment intensity. To enhance the accuracy and applicability of this study, it is recommended to incorporate additional decision-making factors, including local topography, precipitation patterns, soil properties, and engineering measures. This multidimensional approach will enable more precise identification of representative comprehensive treatment targets, thereby providing a robust scientific basis for regional planning and formulation of optimal remediation strategies.

[Objective] Accurately estimating the carbon sources and sinks of ecosystems and exploring their spatiotemporal evolution patterns are of great significance for optimizing territorial space management and promoting the low-carbon transition in Hebei Province. [Methods] This study utilized energy consumption data, remote sensing data, carbon density data, water carbon flux data, and salt marsh and coastal aquaculture data to calculate the carbon emissions from energy consumption, terrestrial ecosystem carbon sinks, and water carbon fluxes in Hebei Province. Additionally, a scientific analysis of the degree of carbon neutrality was conducted. [Results] (1) The overall carbon emissions from energy consumption in Hebei Province showed a continuous upward trend from 2000 to 2019, with emissions in 2019 reaching approximately four times those of 2000, at an average annual growth rate of about 6.98%. (2) The total NEP (Net Ecosystem Production) in Hebei Province from 2000 to 2020 showed significant fluctuations but an overall upward trend. The interannual variations in carbon fluxes from inland waters were minimal, showing a slight increasing trend. Blue carbon from marine aquaculture demonstrated overall growth, increasing from 6 600 tons in 2000 to 35 600 tons in 2020. (3) A comprehensive analysis of the carbon sources and sinks in Hebei Province’s territorial space revealed that the total ecosystem carbon sinks in 2020 could offset approximately 3.54% of the carbon emissions from energy consumption. [Conclusion] This suggests that Hebei Province currently has a relatively low carbon neutrality capacity, below the national average (15%), and faces enormous pressure to reduce carbon emissions and increase carbon sinks.

[Objective] Reservoir construction has severely degraded the ecological environment of reservoir banks. The high-frequency, large-amplitude water level fluctuations make ecological restoration in the drawdown zone particularly challenging. After the operation of Henan Tianchi Pumped Storage Power Station, the water level exhibits significant weekly regulation fluctuations, resulting in large areas of exposed concrete on reservoir banks, severe fragmentation of the drawdown zone, and extreme habitat stress that greatly impedes vegetation restoration. This study focuses on the ecological restoration of the rocky slope drawdown zone in the Henan Tianchi Pumped Storage Power Station reservoir to ensure water resource security. [Methods] To address the severely impaired ecological function of the drawdown zone, this study conducted systematic analysis of habitat characteristics, including hydrological patterns, bank characteristics, non-point source pollution, and plant communities. Focusing on the critical need for ecological restoration in rocky slope drawdown zones of pumped storage reservoirs, this study investigated regreening approaches targeting growth substrate construction, plant community rehabilitation, and vegetation management. [Results] After more than one year of implementation, vegetation in the drawdown zone showed robust growth. No slope failure or soil erosion was observed. Plants exhibited strong resilience in terms of post-submersion recovery, expansion, and colonization, achieving an overall survival rate of 83.2%. Bamboo Willow (Salix sp), Bamboo Willow cuttings (Salix sp), Zhongshan Fir (Taxodium hybrid), Wallich Willow (Salix wallichiana), Chaste Tree (Vitex negundo), Lax-flowered Myricaria (Myricaria laxiflora), Variegated Willow cuttings (Salix variegata), Small Dogwood (Swida paucinervis), and Chinese Distylium (Distylium chinense) all achieved survival rates exceeding 85% and exhibited long-term tolerance to complete submersion. Planting Variegated Willow (Salix variegata) using cuttings was recommended to enhance its survival rate. Through practical restoration efforts within the test area, 13 plant species tolerant to submersion, drought, and barren conditions were selected: Zhongshan Fir (Taxodium hybrid), Bamboo Willow (Salix sp), Wallich Willow (Salix wallichiana), Lax-flowered Myricaria (Myricaria laxiflora), Variegated Willow (Salix variegata), Small Dogwood (Swida paucinervis), Chinese Distylium (Distylium chinense), Chaste Tree (Vitex negundo), Bermuda Grass (Cynodon dactylon), Indian Shot (Canna indica), Lamb’s Quarters (Chenopodium album), Violet Orychophragmus (Orychophragmus violaceus), and Cosmos (Cosmos bipinnatus). [Conclusion] Ecological restoration of rocky slope drawdown zones in pumped storage reservoirs requires an integrated approach combining engineering and biological measures. Engineering measures provide the essential soil substrate for plant growth and ensure vegetation survival. Based on a comprehensive consideration of topography, geology, and water level fluctuation patterns, the geogrid + ecological bag + hanging net composite technique is applied in permanently exposed and alternately submerged zones, while the long-fiber ecological bag + mesh reinforcement composite technique is used in permanently submerged zones. Vegetation measures should adopt a tree-shrub-herb configuration model tailored to the degree of submersion stress and the desired landscape effect. ①Permanently exposed zone. Trees: Bamboo Willow (Salix sp), Zhongshan Fir (Taxodium hybrid), Wallich Willow (Salix wallichiana)+Shrubs: Chaste Tree (Vitex negundo) +Herbs: Cosmos (Cosmos bipinnatus), Violet Orychophragmus (Orychophragmus violaceus), Lamb’s Quarters (Chenopodium album), Indian Shot (Canna indica), and Bermuda Grass (Cynodon dactylon). ②Alternately submerged zone. Trees: Bamboo Willow (Salix sp), Zhongshan Fir (Taxodium hybrid) +Shrubs: Variegated Willow (Salix variegata), Small Dogwood (Swida paucinervis), and Lax-flowered Myricaria (Myricaria laxiflora) +Herbs: Bermuda Grass (Cynodon dactylon). ③Permanently submerged zone. Shrubs: Variegated Willow (Salix variegata), Small Dogwood (Swida paucinervis), and Chinese Distylium (Distylium chinense) +Herbs: Bermuda Grass (Cynodon dactylon). The findings hold significant implications for scientifically guiding regreening efforts in rocky slope drawdown zones of pumped storage power station reservoirs.

[Objectives] In the context of global climate change, studies on coastal wetlands and their carbon sink capacity face both major opportunities and challenges. Therefore, investigating their spatiotemporal distribution is crucial for achieving the “dual carbon” goals. [Methods] Taking the coastal wetlands of Chongming Island, Shanghai, as the study area, Sentinel-2 remote sensing images in 2015, 2017, 2019, and 2021 were used. Based on corrected carbon density and land use derived from supervised classification, the spatiotemporal distribution characteristics of carbon storage were obtained. The influencing factors of carbon storage were quantitatively analyzed using the geodetector method. [Results] The periphery of Chongming Island is dominated by wetlands, with natural wetlands (mainly river-lake water bodies, grasslands, reed beds, and tidal flats) primarily distributed along the shoreline, while the inner area is non-wetland. The area of both artificial and natural wetlands increased significantly, by approximately 20 000 hm². The carbon storage of Chongming Island first increased and then decreased, but wetland carbon storage remained high, showing an overall positive trend of annual increase (approximately 600 000 tons). Conversions from non-wetland to both natural and artificial wetlands led to increases in carbon storage, indicating the high carbon sequestration potential of coastal wetlands. Natural factors had a weak influence on wetland carbon storage in Chongming Island, whereas socioeconomic development had a stronger impact. The geodetector q-values for economic added value and land use intensity reached 0.79 and 0.82, respectively. The interactive effects of natural and human factors, such as GPP combined with economic added value and population, yielded a q-value of up to 0.99, highlighting the importance of human-nature harmony in enhancing carbon sequestration in wetlands. [Conclusion] Using meteorological data from Shanghai and Chongming Island, together with a carbon density correction model, the local carbon density of Chongming District was derived. This method has low data acquisition difficulty, as most meteorological data required for local carbon density calculations can be obtained from the study area’s statistical yearbooks, and pre-correction carbon density can be retrieved from other literature. The method is applicable to coastal wetlands and other “dual carbon” focus areas, enabling accurate acquisition of localized parameters and improving the accuracy of carbon storage estimation to some extent. Additionally, directly applying geodetector to carbon storage simplifies the analysis process compared to indirect detection via land cover types and improves accuracy. The results show that wetland areas are generally increasing, with a significant growth in the proportion of natural wetlands. Carbon storage in Chongming’s coastal wetlands has increased annually, indicating initial success in wetland conservation. Dual-factor interactive effects have a greater impact on coastal wetland carbon storage than single-factor effects, and carbon storage is greatly influenced by socioeconomic factors.