[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.

[Objective] Previous studies in China on slope erosion characteristics under rainfall patterns have primarily focused on the loess region of Northwest China and red soil region of South China. Research on the purple soil region remains limited. Purple soil is the dominant cultivated soil in the Three Gorges Reservoir Region. Following the reservoir’s construction, substantial cultivated land was submerged, compelling local residents to reclaim more steep slopes for cultivation. This has exacerbated soil erosion issues in this region. Considering both rainfall patterns and land characteristics, this study conducted a comparative analysis of runoff and sediment reduction effects under different soil and water conservation (SWC) measures on purple soil slopes in the reservoir area. Understanding the response characteristics of runoff and sediment yield on purple soil slopes to SWC measures under different rainfall patterns could provide theoretical basis for evaluating the effectiveness of SWC measures in purple soil regions. [Methods] Using runoff and sediment yield data from 37 rainfall events across 10 runoff plots under different SWC measures in purple soil regions, rainfall patterns were classified using K-means clustering based on four indicators: average intensity (I_ave), maximum 30-minute intensity (I₃₀), duration (T), and erosivity (R_r). [Results] The results showed that the 37 rainfall events were classified into five patterns: Type I (low erosivity, long intensity, long duration), Type II (medium-low erosivity, medium-low intensity, medium-long duration), Type III (medium erosivity, medium intensity, medium duration), Type IV (medium-high erosivity, medium-high intensity, medium-short duration), and Type V (strong erosivity, high intensity, short duration).. Among these, Type III rainfall was identified as the primary rainfall pattern causing slope soil erosion, with runoff and sediment yields being 1.2-6.4 times and 2.7-19.4 times higher than the other four types. Narrow-terrace cultivation and platform planting exhibited optimal runoff reduction effects under light (Types I-II) and heavy (Types IV-V) rainfall patterns, respectively. [Conclusion] This was primarily because terraces effectively intercepted runoff sediment from low-intensity, small-volume rainfall, whereas under high-volume and high-intensity rainfall, terraces tended to become saturated, and platform fields were more effective in intercepting runoff sediment. Furthermore, the grass strips in forested areas demonstrated optimal runoff reduction effect under Type I rainfall pattern, primarily because the vegetation effectively slowed runoff velocity, enhanced infiltration, and facilitated sediment deposition. These findings provide a basis for further clarifying the relationship between rainfall and runoff sediment in purple soil regions.

[Objective] Current studies on the causes of water-sediment variation in the Yellow River mainly focus on the middle reaches’ hyperconcentrated sediment region or the Hekou-Longmen reach. Fewer studies have addressed the evolution of water-sediment relationships in typical tributaries of the upper reaches. Most existing research focuses on influencing factors of total water-sediment changes, with limited investigations on the driving factors behind water-sediment relationship evolution. The basin’s water-sediment effects under large-scale ecological restoration measures urgently need to be revealed. [Methods] This study took the Qingshui River Basin (QRB), the largest and most severely eroded tributary in the Ningxia section of the Yellow River, as the research object. Based on the actual water and sand data measured in the research area from 1955 to 2016, trend analysis and water-sediment relationship curves were used to reveal the characteristics of water-sediment changes. Multi-source data were employed to analyze the response of water and sediment to key influencing factors, ultimately exploring the evolution of basin water-sediment relationships under soil and water conservation. [Results] The interannual variations in runoff and sediment transport in the QRB were drastic. Annual runoff and sediment transport in Guyuan showed a significant downward trend. Annual runoff in Hanfuwang exhibited a significant decline, while annual sediment transport showed a non-significant decrease. Annual runoff and sediment transport in Quanyan Mountain showed no significant changes. Significant abrupt change years were observed in both annual runoff and sediment transport in the QRB. The abrupt change in annual runoff occurred in the 1990s, while that in annual sediment transport occurred after 2000. The periods of strong soil and water conservation measures in the Loess Plateau were close to the above abrupt change years of water-sediment factors. Sediment production in the QRB was jointly influenced by climate change (precipitation) and human activities. Drastic changes in the underlying surface caused by human activities were the primary factor leading to the sharp reduction in water and sediment in the QRB, further driving the evolution of basin water-sediment relationships. After 2000, the basin’s water-sediment relationship underwent a distinct transformation, specifically manifested as a significant decrease in the coefficient “a” of the water-sediment relationship curve and a notable increase in the downstream index “b”. Drastic changes in the underlying surface caused by human activities remained the primary factor driving water-sediment changes and the evolution of basin water-sediment relationships. [Conclusions] The water-sediment relationships in the basin have evolved as a result of large-scale soil and water conservation measures. Based on the sediment “storage-release” effect, the probability of strong sediment transport events still exists under new water-sediment conditions, necessitating strengthened preventive measures.

[Objective] In practical remediation projects, leaching heavy metal-contaminated soils with high clay content is highly challenging. This is not only due to the low permeability of high-clay-content soils, but also because of the unclear influencing patterns and mechanisms of clay content on soil leaching. Current studies on the effects of clay content primarily focus on mixtures of sand and fine-grained soils, lacking systematic investigations into clay soils. Moreover, previous studies investigate the physicomechanical properties of soils with different clay contents, without comparing their effects on heavy metal adsorption and desorption. Studies on the correlation between heavy metal and clay content rely on field sampling methods. However, due to varying soil samples and contamination types, along with complex influencing factors, the conclusions are inconsistent. Therefore, this study intends to artificially prepare soil samples with different clay contents to eliminate complex influencing factors, investigate differences in their leaching performance and geotechnical properties, and analyze their correlations. In doing so, the single-factor influencing pattern of clay content can be obtained. [Methods] Based on the principle that soil particles of different sizes had different settling speeds in solution, soil samples with clay contents of 20%, 30%, 40%, and 50% were prepared via sedimentation method. First, the basic physical properties of soil samples were analyzed, followed by consolidation tests to investigate the porosity ratios, compression characteristics, permeability, and consolidation behaviors of soils with different clay contents, as well as their microscopic characteristics under scanning electron microscope (SEM). Through batch oscillation-centrifugation experiments, the adsorption of heavy metals (Cu and Zn) by the soil samples and their desorption characteristics during heavy metal removal using citric acid were studied, with analysis incorporating pH values and particle size variations. [Results] Soils with different clay contents exhibited significant differences in physicomechanical properties. Soils with a high clay content had larger specific surface areas, lower relative densities, more muscovite and chlorite minerals, and fewer quartz and albite minerals. Additionally, these soils had higher liquid-plastic limits and greater compressibility, while showing lower permeability and porosity ratios, with more soil particle aggregates observed microscopically. The increase in clay content significantly enhanced the soil’s adsorption capacity for heavy metal ions, while deteriorating the desorption performance of citric acid during leaching. As the clay content increased from 20% to 50%, the maximum heavy metal adsorption increased by up to 50%, whereas the maximum desorption rate decreased by up to 20%. Notably, pronounced differences were observed between 20% and 30% clay contents, mainly attributed to the formation of numerous aggregates during this stage, which enhanced the adsorption performance of the soil for heavy metals. In addition, the correlations of clay content with Zn and Cu differed. Zn was more difficult to remove than Cu in high-clay-content contaminated soils. [Conclusions] The experimental findings demonstrate that the differences in various physicomechanical and adsorption-desorption characteristics caused by different clay contents significantly influence the selection of technologies and parameters for soil leaching. Therefore, practical remediation projects must integrate relevant research and experimental analyses to fully consider the effects of clay content, so as to better achieve the goals of contaminated soil remediation.

Biochar is an environmentally friendly soil modifier due to its porous and high specific surface area. To investigate its impact on the water-holding capacity of red clay and the growth of common slope grass species, we selected red clay from Guilin as the research subject. Different types and dosages of biochar were incorporated into the red clay. Subsequently, water-holding capacity tests, pot-planting tests, and pH tests were conducted. Scanning electron microscopy (SEM) was employed to elucidate the mechanism by which biochar affects the water-holding capacity of red clay. Results revealed that the saturated water-holding capacity and pH value of red clay increased with the rising content of four types of biochar, effectively improving the environmental conditions for plant growth. Specifically, adding biochar increased the germination number and plant height of grass seeds. However, a biochar content exceeding 5% negatively affected the growth of grass seeds. Microscopic tests indicated that biochar filled the pores between red clay aggregates, thereby enhancing the saturated water-holding capacity of red clay thanks to its porosity and hydrophilicity.

To investigate the effect of sand content on the growth of slope ecological restoration plants, we used the Analytic Hierarchy Process to select suitable plant species and then conducted planting experiment with sand added in Yili loess slopes. By analyzing changes in plant coverage, cumulative soil evaporation, and maximum crack rate, we found that adding sand to the planting soil can speed up plant germination and improve the soil germination rate. During early growth stage with sufficient water supply, the germination rate and plant coverage are positively correlated with sand content. Nevertheless, under drought conditions, plant coverage decreases as sand content rises. The cumulative evaporation of soil moisture is positively correlated with sand content and varies significantly with temperature fluctuations. Higher temperatures lead to larger differences in cumulative evaporation among samples with different sand contents, but these differences gradually narrow as the temperature drops. Taking 40% sand content as the threshold for optimal conditions: when sand content is below 40%, it is positively correlated with the maximum crack rate, and an increase in the maximum crack rate corresponds to an increase in the peak plant coverage of each sample. However, when sand content exceeds 40%, sand content and the maximum crack rate display a negative correlation. As maximum crack rate increases, the peak plant coverage of sample decreases. For wild or poorly maintained ecological restoration sites, an optimal sand content of 20% is recommended. For artificially maintained ecological restoration sites, a 60% sand content is optimal. In flat, human-intervened ecological restoration and maintenance sites, full sand coverage is the best choice.

Exploring the spatiotemporal evolution patterns of Net Primary Productivity (NPP) of vegetation in Hutuo River Basin is of great significance for understanding and improving the surrounding ecological environment. Based on MOD17A3 NPP data, the spatiotemporal evolution of vegetation NPP in Hutuo River Basin from 2003 to 2022 was analyzed using methods such as univariate linear regression analysis and coefficient of variation. The vegetation NPP was combined with land cover types and terrain factors for zoning statistics. Results show that from 2003 to 2022, the average vegetation NPP in Hutuo River Basin ranged from 300 gC/(m²·a) to 400 gC/(m²·a). The maximum NPP peak occurred in 2020, reaching 828 gC/(m²·a), while the average NPP peak was in 2022, at 424.33 gC/(m²·a). Areas where vegetation NPP increased linearly from 2003 to 2022 accounted for 96.46% of the study area. The relative annual change rate of vegetation NPP mainly fell within the range of 20%-40%, and the long-term stability of vegetation NPP was characterized by low fluctuations. Among the land-cover types in the Hutuo River Basin from 2003 to 2022,agricultural land had the lowest average vegetation NPP,at 331.92 gC/(m²·a), whereas grassland had the highest, at 384.40 gC/(m²·a). Vegetation NPP increased with rising elevation and slope. In terms of aspect, planes featured the lowest vegetation NPP.

Taking Landsat images in 2000, 2010, and 2020 as data sources, we examined the dynamic changes of ecosystem types in the Ali prefecture in Tibet autonomous region over the past two decades by using ecosystem dynamics degree and transfer matrix model. Within the “Sensitivity-Pressure-Resilience” assessment framework, we selected 14 indicators to establish a sensitivity evaluation index system to delineate ecological sensitive zones, aiming to maintain ecosystem stability and scientifically build ecological security barriers. The findings demonstrate that 1) All eight ecosystem types experienced varying degrees of changes.The degree of dynamics for urban ecosystem and agricultural ecosystem displayed the most significant changes. 2) Deserts and grasslands served as crucial “sources” and “sinks” during the ecosystem evolution in the Ali prefecture. 3) The ecological sensitive areas mainly consisted of medium- and high-sensitivity zones, covering an area of 168 800 km², which accounted for nearly 50% of the total. Spatially, the northwest part of Ali prefecture exhibited high sensitivity, while the southeast part low sensitivity, with low-sensitivity areas encircling high-sensitivity areas.

Understanding the runoff and sediment yield processes on slopes are of crucial significance in enhancing the research on rainstorm and flood dynamics in mountainous areas. To examine the effects of slope soil permeability and gradient on runoff and sediment yield characteristics in mountainous terrain, an indoor artificial simulated continuous rainfall experiment was conducted. The experiment was conducted on a soil trough with shallow upper section and deep lower section using soil samples from the Guanshan River Basin. The study aimed to investigate and summarize the variations in runoff and soil erosion with different slope gradients. Findings reveal that 1) At 5° and 25° slopes, surface runoff rates increased with escalating rainfall intensity, with higher rates observed on slopes featuring impermeable bottom layers compared to those with permeable layers. At a 15° slope, however, runoff increased with notable fluctuations, and differences in runoff rates between impermeable and permeable bottom layers were not statistically significant. 2) Interflow rates escalated over time during each rainfall simulation, displaying significant variations across different slope gradients. Generally, interflow rates were higher on slopes with impermeable bottom layers than on those with permeable layers. Notably, the relationship between interflow rate and surface runoff rate was negatively correlated at 5° slopes and positively correlated at 25° slopes. 3) Surface runoff velocities increased with rising rainfall intensity. At 5° and 15° slopes, velocities were significantly higher on impermeable bottom layers compared to permeable ones, whereas at 25°, no significant differences were observed. 4) Soil erosion was most pronounced during the second and third rainfall simulations across different slope gradients. Erosion rates were higher on impermeable bottom layers compared to permeable ones at 5° and 25° slopes, but showed fluctuations at 15° slopes.

The hydro-fluctuation belt (HFB) of reservoir tail is a critical area for ecological restoration due to the frequent changes in its water levels and land uses which lead to simplified ecosystem structures and degraded wetland functions. The efficiency of current ecological restoration technologies for managing high water levels in summer and prolonged droughts in autumn and winter in HFB are unsatisfactory. This study proposes a comprehensive restoration model that combines wetland-forest engineering construction and habitat diversification for the HFB in Yutian Lake of Jingdezhen City as a case study. Initially, low weirs and shallow lakes, along with habitat islands, were constructed in the HFB. These structures were then optimized by planting trees (such as Taxodium), shrubs, and grasses on the low weirs and habitat islands. This approach created a nearly natural “tree-shrub-grass” wetland ecosystem in the HFB of Yutian Lake reservoir. Our findings indicate that this comprehensive restoration technology is suitable for reservoir wetland HFB characterized by high water levels in summer and extended dry periods in autumn and winter. After restoration, the landscape quality of the Yutian Lake area has significantly improved. The Shannon biodiversity index reached 1.69, marking a substantial increase in biodiversity. The wetland function and ecosystem health in the HFB have also enhanced. This restoration mode and its effects have important implications for ecological management in similar reservoir wetland HFBs.

The diffusion of leachates from phosphate solid wastes is a major source of contaminants. Based on the existing and increment of phosphate solid waste in China as well as its environmental impacts, this study reviews the current status of researches on phosphate solid waste accumulation in China focusing on the composition, diffusion, and migration of leachates from phosphate solid wastes. More stringent requirements for leaching experiments and the design of impermeable barriers are essential as the permeability coefficient of impermeable materials may increase due to high pollutant concentration in leachate, low pH value of phosphogypsum, and large overburden pressure. Current researches on leachate release and diffusion often fail to replicate actual landfill conditions. Future studies should integrate field-specific parameters such as ambient temperature, rainfall infiltration, and effective stress from overburden weight. Thermal-humid-mechanical (THM) leaching test apparatus is also recommended for multifield coupling investigation. This approach will provide a more comprehensive theoretical understanding of leachate prevention and control in phosphate waste landfills.