ObjectiveAffected by multiple factors such as extreme hazard events and climatic forcing, the Joshimath town on the southern slope of the Himalayas exhibits complex deformation characteristics. Joshimath is located in Chamoli district, Uttarakhand, northern India, between two major active faults—the Main Central Thrust and the Munsiari Thrust—and the town is largely built on paleo-landslide deposits. This study aims to analyze the spatiotemporal evolution patterns of deformation of the Joshimath landslide body and its associations with climatic factors and extreme hazard events. MethodsThis study integrated time-series SBAS-InSAR, change-point detection, and signal decomposition methods to monitor ground deformation across nine areas in Joshimath town and to derive subsidence and uplift displacement time series. The decomposed displacement components (trend and periodic terms) were independently related to monthly air temperature and precipitation to identify deformation mutations and quantify their climatic associations. Finally, SARIMAX and LSTM models were compared to predict future deformation trajectories and assess the robustness of nonlinear trend extrapolation. Results1) Deformation showed strong spatial heterogeneity within the paleo-landslide body. Subsidence areas exhibited greater deformation intensity than uplift areas. Areas III and VII were strong-subsidence, high-risk areas, with sustained downward motion and clear dominance of the long-term trend component; by contrast, other areas showed weaker subsidence or alternating uplift–subsidence behavior. 2) Abrupt changes in displacement rate were detected in multiple areas. These change-point signals provided evidence that the 2021 Ronti ice-rock avalanche acted as a key external perturbation capable of altering deformation behavior. The clearest change point signatures and post-event trajectory shifts were observed in areas VI and VIII, where the displacement evolution showed a distinct change relative to the pre-event stage, demonstrating a stronger sensitivity to extreme-event forcing than in other areas. 3) The deformation time series showed a significant lagged response of 1−2 months to climatic factors. Air temperature exerted a more pronounced influence on deformation than precipitation, with partial correlation coefficients of 0.5−0.8, highlighting its dominant role in modulating deformation at the monthly scale. 4) LSTM outperformed SARIMAX in capturing nonlinear deformation and periodic climate-driven responses. The LSTM-based risk heat map indicated that the subsidence areas III and VII were future high-risk areas, while the uplift-dominant area VIII should also be considered as a potentially unstable area. ConclusionsThis study reveals the joint control of extreme events and lagged climatic effects on deformation of a reactivated paleo-landslide, and predicts deformation trends using an SSA–LSTM framework. The results provide a scientific basis for stability assessment and hazard prevention for paleo-landslides on the southern Himalayan slope under ongoing climate change.
ObjectiveThis study aims to systematically evaluate the cultivability of sloping farmland in Hunan province, where extensive hilly terrain and a high risk of soil erosion constrain the sustainable use of farmland. MethodsA province-wide sloping farmland database was constructed using sloping farmland polygons identified from the 2024 National Land Survey. Seven indicators were selected for the evaluation: slope gradient, soil erosion severity, soil layer thickness, soil texture as represented by gravel content, soil pH, cation exchange capacity (CEC), and soil organic matter content. The limiting factor method was applied to evaluate the cultivability of sloping farmland. Results1) Sloping farmland in Hunan province covered 3 754.51 km2, accounting for 10.08% of the total farmland area. Farmland on gentle slopes of ≥ 6° –15° accounted for 65.07% of the total sloping farmland area. Farmland on steep slopes of ≥ 25° covered 311.77 km2 and was mainly distributed in Huaihua, Xiangxi prefecture, and Shaoyang. The mean sloping farmland characteristic index for the province was 0.19. Changsha (0.35), Zhuzhou (0.32), and Huaihua (0.31) had relatively high index values, indicating greater difficulty in the development, utilization, and management of sloping farmland. 2) Very slight and slight erosion were the predominant soil erosion classes across the province. The mean values of the comprehensive index of soil erosion on sloping farmland in Yongzhou, Loudi, and Hengyang were 11.83, 11.69, and 11.64, respectively, identifying these cities as priority areas for soil and water conservation. 3) The areas of sloping farmland classified as suitable and unsuitable for cultivation were 2 251.86 and 1 502.66 km2, respectively. The proportions of sloping farmland classified as suitable for cultivation exceeded 80% in both Zhuzhou and Hengyang, while areas unsuitable for cultivation were concentrated mainly in Shaoyang, Huaihua, and Loudi. The main limiting factors included low CEC, high gravel content, and excessive slope gradient, corresponding to areas of 824.08, 400.01, and 311.77 km2, respectively. ConclusionsSloping farmland in Hunan province exhibits pronounced spatial heterogeneity, and soil erosion risk increases with slope gradient. Unsuitability for cultivation is jointly constrained by topographic conditions and soil physicochemical properties. Management measures should be tailored to cultivability grades and dominant limiting factors and should include category-specific protection, soil improvement, soil and water conservation, and the ecological conversion of unsuitable sloping farmland.
ObjectiveGiven that field experiments on soil nutrient loss in the black soil region of Northeast China are currently insufficient, this study analyzes the characteristics of runoff, sediment generation, and nitrogen loss on gentle slope farmland, aiming to provide a scientific basis for regional soil erosion control and prevention. MethodsIn the Qinggou small watershed in Nanguan district, Changchun city, Jilin province, six runoff plots were established at the hydraulic erosion observation station. Three slope gradients of 3°, 6°, and 9° were set up, along with two tillage patterns: conventional downhill ridge tillage (corn) and straw-covered downhill ridge tillage (corn). Based on monitoring data of runoff and soil loss production from May to September 2024, the characteristics of nitrogen loss (total nitrogen, nitrate nitrogen, and ammonium nitrogen) during the runoff and sediment generation were analyzed in the conventional tillage and straw-covered runoff plots. Results1) Nitrogen loss in runoff and sediment accounted for 56.15% and 43.85% of total nitrogen loss, respectively. The loss of nitrate nitrogen and ammonium nitrogen in runoff accounted for 53.32% and 8.34% of nitrogen loss in runoff, respectively. 2) With the increase of slope, runoff and sediment generation increased, and the loss of total nitrogen in sediment generation and total nitrogen and nitrate nitrogen in runoff also increased, while the change in ammonium nitrogen loss in runoff was not obvious. The nitrogen concentration showed a pattern consistent with the loss amount. 3) Straw cover had a significant inhibitory effect on runoff, sediment generation, and nitrogen loss. At slopes of 3°, 6°, and 9°, the runoff control efficiency was 95.55%, 89.37%, and 90.62%, respectively, and the sediment control efficiency was 95.56%, 89.03%, and 99.95%, respectively. 4) Nitrogen loss is significantly positively correlated with runoff and sediment generation, with correlation coefficients of 0.99 (P < 0.05) and 0.96 (P < 0.05), respectively. Runoff was mainly related to rainfall and the interval time between rainfall events that produce runoff and soil loss.ConclusionsImplementing straw mulching on slopes of different gradients can effectively reduce runoff, sediment generation, and nitrogen loss, but it can lead to an increase in nitrogen concentration in the runoff. The nitrogen loss from sloped farmland is mainly determined by the amount of runoff and sediment generation.
ObjectiveUrbanization has resulted in the occupation of gentle-slope cultivated land, whereas newly added cultivated land is concentrated on steeper slopes. As a major grain-producing province, it is of great significance to explore the evolution of cultivated land slope to ensure cultivated land quality and food security. MethodsBased on multi-source data from 1990 to 2020, this study employed methods including slope spectrum curve, slope index, and geodetector to analyze the upward trend of cultivated land slope and the occupation-compensation characteristics under different slope gradients, and to quantitatively identify the key driving factors. Results1) The proportion of cultivated land with a slope > 15° in the province increased by 0.55%. The slope of newly added cultivated land was consistently higher than that of lost cultivated land. The proportion of areas with "significant upward-sloping" was the highest during 2000–2005 (55.13%), which was mainly concentrated in Zone Ⅲ-4-1xt and Zone Ⅲ-4-2t. 2) The net change rate of cultivated land remained negative, with the highest intensity of construction occupation. Specifically, the proportion of cultivated land with a slope > 2°−6° occupied by construction reached 27.95%, and this phenomenon was most prominent in Zone Ⅲ-5-3fn. Gained cultivated land was mainly from the reclamation of forestland and grassland, with the proportion of supplementation in the > 6°−15° slope range accounting for up to 10.17%. The proportion of cultivated land gained from other reclamation was relatively high in Zone Ⅲ-5-2w. 3) Among single driving factors, precipitation had the strongest explanatory power (q = 0.201), followed by GDP (q = 0.164) and human activity intensity (q = 0.153). Two-factor interactions exhibited an enhancement effect. In Zone Ⅲ-5-3fn, the interaction between distance to roads and human activity intensity was relatively strong, while in other zones, the interaction between precipitation and human activity intensity exerted a dominant influence. ConclusionsThis study confirms that the upward-sloping phenomenon of cultivated land in Shandong province is the result of the synergistic effects of natural and anthropogenic factors, thereby providing a scientific basis for optimizing the cultivated land protection pattern from the perspective of slope.
ObjectiveIn the black soil region of Northeast China, the soil surface remains bare for a relatively long period after harvest and before snowfall, as well as after snowmelt and before seedling emergence, leading to a high erosion risk. In particular, snowmelt erosion intensifies soil and water loss and soil quality degradation in this region. Therefore, it is urgent to explore effective cover measures during the fallow period and evaluate their effectiveness. MethodsUsing Zea mays monoculture as the control, five winter cover crop treatments were established: Triticum aestivum, Agropyron cristatum, Medicago sativa, Vicia villosa, and Medicago sativa-Vicia villosa mixture. Soil basic physicochemical properties, aggregate stability, soil anti-erodibility, and soil anti-scourability were systematically measured, and the entropy weight–fuzzy comprehensive evaluation method was applied for comparative analysis. Results1) T. aestivum significantly reduced soil bulk density and increased soil total porosity. M. sativa significantly increased soil organic matter content (4.36 g/kg higher than that of Z. mays), and the M. sativa-V. villosa mixture significantly increased soil total nitrogen content (0.23 g/kg higher than that of Z. mays). 2) A. cristatum significantly increased the proportion of soil macroaggregates ( > 0.250 mm) and mean weight diameter, showing the highest aggregate stability. 3) The anti-erodibility indices of T. aestivum and M. sativa-V. villosa mixture were 35% and 45% higher than that of Z. mays, respectively. M. sativa had the highest anti-scourability index, which was 5.5 times that of the control. 4) The comprehensive evaluation indicated that the order of winter cover crops in improving black soil erosion resistance was: M. sativa-V. villosa mixture > A. cristatum > V. villosa > T. aestivum > M. sativa > Z. mays. ConclusionsPlanting winter cover crops after Z. mays harvest significantly improves the physicochemical properties and structure of black soils, thereby enhancing soil erosion resistance. The effects vary among different cover crops. Among them, the legume (M. sativa)-legume (V. villosa) mixture performs best, demonstrating its potential for application during the fallow period in the black soil region of Northeast China. The findings provide a scientific basis for erosion control on sloping farmland and sustainable utilization of black soil resources.
ObjectiveEcosystem resilience reflects the capacity of an ecosystem to resist, adapt to, and recover from disturbances, and is a key indicator for assessing ecosystem stability. Analyzing changes in ecosystem resilience can effectively reflect the benefits and potential risks of forestry ecological projects, which is of great significance for the continuous improvement of ecological governance quality. MethodsTaking Ji county on the Loess Plateau as a case study, this study analyzed the spatiotemporal changes in ecosystem resilience from 2000 to 2023 based on the framework of ''resistance-adaptability-recovery''. Furthermore, by integrating the system dynamics model and the intPLUS model, this study projected the status of ecosystem resilience in 2035 under different development scenarios (current trend continuation, green transition, and high-carbon economy).Results1) With the continuous implementation of forestry ecological projects, ecosystem resistance increased markedly, while adaptability and recovery showed slight improvements, and overall ecosystem resilience was progressively enhanced. 2) Areas of high ecosystem resilience were concentrated in forestland, while low-value areas were distributed in arable land and construction land, exhibiting a significant spatial cold and hot spot clustering pattern, which provided spatial guidance for differentiated management strategies. 3) Under the current trend continuation scenario, ecosystem resilience improved moderately; under the green transition scenario, it improved markedly; whereas under the high-carbon economy scenario, a trend of degradation emerged within the ecosystem resilience grades. ConclusionsForestry ecological projects have effectively enhanced ecosystem resilience, yet it remains necessary to formulate precise, dynamic, and collaborative strategies for its further improvement. The findings can provide a case study and reference for the Loess Plateau and other similar regions.
ObjectiveTo improve the ecological environment and sustainable development status of vegetation in the Hutuo River Basin, this study investigates the poor soil structure and weak water and nutrient retention capacity of sandy soil in the Hutuo River of Shijiazhuang city. MethodsThrough simulated experiments, five different soil water-retaining agents (attapulgite-sodium polyacrylate water-retaining agent, biochar-bentonite water-retaining agent, humic acid-type water-retaining agent, polyacrylate water-retaining agent, and starch-based SAP) were selected as research subjects to explore their improvement effects on sandy soil. Furthermore, through an orthogonal experiment, different proportions of water-retaining agent, corn straw, and biochar were added to the soil to investigate the water- and nutrient-retention effects of soil under different substrate ratios. ResultsWhen the dosage of the water-retaining agent was 1.0%, except for the humic acid-type and polyacrylate water-retaining agents, the soil moisture content of the other water-retaining agents was > 85%, and soil electrical conductivity was > 1 500 μS/cm. However, soil compaction occurred when 0.1%–1.0% of the humic acid-type water-retaining agent and 0.5%–1.0% of the starch-based SAP water-retaining agent were applied. Therefore, the attapulgite-sodium polyacrylate water-retaining agent was more suitable for the sandy soil in this region and exhibited better water retention performance. The effects of the three factors—water-retaining agent, corn straw, and biochar—on substrate soil moisture were ranked in descending order as follows: water-retaining agent > corn straw > biochar. The order of influence on substrate soil electrical conductivity was as follows: water-retaining agent > biochar > corn straw. The effect of the water-retaining agent was significant. With increasing water-retaining agent dosage, soil moisture and electrical conductivity were significantly higher than those of the control group. However, with the addition of corn straw, its effects on soil moisture content and electrical conductivity gradually decreased. When the water-retaining agent was 10 g, corn straw was 0 g, and biochar was 20 g, the soil exhibited the best water retention performance. ConclusionsThe attapulgite-sodium polyacrylate water-retaining agent exhibits the best performance. The optimal formulation for substrate water retention performance is 10 g of water-retaining agent, 0 g of corn straw, and 20 g of biochar per kg of substrate, which is suitable for ecological restoration and plant growth in the sandy soil of the Hutuo River Basin.
ObjectiveThe analysis of runoff evolution trends and the quantitative assessment of the impacts of both climate change and human activities on annual runoff are critically important for achieving efficient and rational utilization of water resources, promoting ecological construction, and ensuring sustainable socioeconomic development within river basins. MethodsBased on runoff and precipitation data for the Yihe River Basin from 1951 to 2020, this study employed the Mann-Kendall trend test and a time series comparison method to analyze variation trends in annual precipitation and runoff. An empirical statistical precipitation–runoff model was then used to quantify the impacts of precipitation change and human activities on annual runoff, thereby revealing the evolutionary mechanisms of annual runoff in the basin. ResultsThe results indicated that from 1951 to 2020, annual precipitation and annual runoff in the Yihe River Basin both exhibited a declining trend. Human activities, including water conservancy projects, water resource development and utilization, ecological construction, and land use change, led to a reduction in annual runoff. The runoff evolution process could be divided into a baseline period (1951−1965) and an intervention period (1966−2020). During the baseline period, annual runoff variations were predominantly influenced by precipitation changes. In the intervention period, runoff was jointly affected by precipitation and human activities, and the impact of human activities was relatively larger. ConclusionsThe findings can provide a scientific basis for the Yihe River Basin to coordinate ecological construction with water resource development and utilization, and to formulate differentiated water resource management strategies in the context of intensifying human activities.
ObjectiveIn arid and semi-arid regions, the ecological functions of farmland shelterbelts are critically dependent on soil quality, which is profoundly shaped by irrigation water sources. In the Ulan Buh Desert area, characterized by high evapotranspiration and scarce precipitation, a trade-off is observed between using mineral-laden Yellow River water and using saline groundwater for irrigation. However, the long-term effects of these two water sources on the coupled dynamics of soil nutrients and salt content in shelterbelt systems remain unclear. This study aims to elucidate the regulatory mechanisms of different irrigation water sources on soil nutrient-salt content interactions, thereby providing guidance for sustainable irrigation management. MethodsA typical farmland shelterbelt system in Dengkou county, Inner Mongolia, was selected for this study. Two irrigation treatments were compared: long-term Yellow River water irrigation and long-term groundwater irrigation, each with six replicate plots. Soil samples were collected in July (two weeks after the final irrigation) from five soil depth layers (0–100 cm, at 20 cm intervals). Eight soil nutrient indicators (e.g., organic matter, total nitrogen, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium) and nine salt ions (e.g., Na+, Cl−, and SO42−) were measured. Data were analyzed using one-way ANOVA and correlation analysis. ResultsCompared with groundwater irrigation, Yellow River water irrigation significantly increased the mean contents of soil organic matter (6.85 vs. 3.41 g/kg), total nitrogen (0.45 vs. 0.27 g/kg), ammonium nitrogen (10.39 vs. 8.78 mg/kg), and available potassium (282.11 vs. 234.97 mg/kg) in the 0–100 cm soil layer. Higher spatial stability of these nutrients (coefficient of variation, CV: 4.07%–21.64%) was also observed under Yellow River irrigation. However, under Yellow River irrigation, nitrate nitrogen showed significant leaching in the 40–60 cm layer (P < 0.05). Conversely, groundwater irrigation led to surface accumulation of nitrate nitrogen (4.27 mg/kg) and available phosphorus (13.24 mg/kg). Critically, the mean total salt content under groundwater irrigation was three times that under Yellow River irrigation. In the 80–100 cm layer, Cl− and Na+ concentrations under groundwater irrigation were 23.8 times and 8.23 times higher, respectively, than those under Yellow River irrigation. Correlation analysis revealed that, under Yellow River irrigation, organic matter was negatively correlated with salt ions (e.g., Na+, Cl−), whereas a synergistic accumulation of nutrients and salts was observed under groundwater irrigation. ConclusionsLong-term irrigation with Yellow River water is more effective in maintaining surface soil nutrients and preventing salt accumulation, thereby resulting in a lower risk of soil salinization. Although groundwater irrigation provides short-term benefits for certain nutrients, it induces a high risk of severe salt accumulation in deep soil layers, particularly Cl− and Na+. Therefore, groundwater irrigation should be complemented with drainage systems or mixed with Yellow River water to balance nutrient supply and salt hazard control. The objectives of this study are achieved, as the differential mechanisms of the two water sources on soil nutrient and salt dynamics are clearly identified.
ObjectiveThis study aims to investigate the impact of long-term land use changes on the spatiotemporal variation of soil erosion and to predict the spatial distribution of land use in 2030. MethodsThis study employed GIS spatial analysis techniques and the RUSLE model to quantitatively analyze the spatiotemporal variation of soil erosion in the Xinshui River Basin in the middle reaches of the Yellow River. On this basis, the PLUS model was utilized to simulate and visualize the land use distribution in 2030 under three scenarios: baseline development, farmland protection, and ecological protection. Results1) The area of forestland in the Xinshui River Basin showed an increasing trend from 1995 to 2020, rising from 8.85 × 104 hm2 to 1.16 × 105 hm2. The areas of farmland and grassland decreased to 9.48 × 104 hm2 and 2.16 × 105 hm2 in 2020, which were 3.27% and 11.48% lower than those in 1995, respectively. The construction land area continuously increased from 773.23 hm2 in 1995 to 2.99 × 103 hm2 in 2020. 2) The soil erosion modulus in Xinshui River Basin showed a trend of first decreasing and then increasing. It decreased from 76.37 t/(hm2·a) to 64.24 t/(hm2·a) in 2015, and then increased to 97.31 t/(hm2·a) in 2020. The area of moderate and lower erosion increased, while the area of high-intensity soil erosion above moderate erosion decreased significantly. The area of slight erosion increased from 2.41 × 105 hm2 in 1995 to 2.58 × 105 hm2 in 2020. 3) Under the baseline development, farmland protection, and ecological protection scenarios, both forestland and construction land area in the Xinshui River Basin showed an increasing trend. Among them, the increase in construction land area was the smallest under the ecological protection scenario. ConclusionsIn the Xinshui River Basin, the coverage of forest and grass has been continuously increasing, and the intensity of soil erosion has shown a decreasing trend over the past 25 years.
ObjectiveThe aeolian sandy soil in western Jilin province is characterized by poor structure, organic carbon deficiency, susceptibility to wind and water erosion, and low crop yield, which severely restrict sustainable agricultural development. This study explores effective approaches to improve aeolian sandy soil fertility, enhance soil erosion resistance, and increase crop yield through co-application of organic materials. MethodsUsing Sorghum bicolor as the test crop, seven treatments were established: no organic application (CK), straw return (G), straw + manure (GF), manure (F), straw + microbial agent (GS), microbial agent (S), and manure + microbial agent (FS). Soil aggregate stability, active organic carbon fractions, and crop yield in the aeolian sandy soil were measured under different combined organic material treatments, followed by principal component and correlation analysis. Results1) GF treatment increased the content of water-stable macroaggregates ≥ 0.25 mm (R0.25) and the mean weight diameter (MWD) by 12.11% and 55.6%, respectively. 2) Soil organic carbon (SOC) and its active fractions significantly increased. GF treatment exhibited the greatest increases in SOC, particulate organic carbon (POC), and easily oxidizable organic carbon (EOC), while GS treatment significantly increased dissolved organic carbon (DOC). MWD, geometric mean diameter (GMD), and R0.25 showed high consistency in loading vectors with SOC and POC, all closely distributed along the positive direction of PC1. 3) POC was highly correlated with aggregate stability indices MWD, GMD, and R0.25, with correlation coefficients of 0.90, 0.96, and 0.93 (P < 0.05), respectively. 4) In terms of crop yield, GF treatment significantly increased S. bicolor yield by 104.0% compared to CK. ConclusionsThe co-application of straw and sheep manure (GF) effectively promotes macroaggregate formation, enhances organic carbon sequestration, and improves soil resistance to wind and water erosion through a synergistic mechanism where ''slow-release carbon from straw builds the framework, and fast-release carbon from manure provides cementation.'' This approach achieves high crop yield and represents an optimized management model for the region, integrating soil improvement, carbon sequestration, and yield increase benefits.
ObjectiveIn central Yunnan, engineering excavation has led to the exposure of the eluvial and parent material layers in subalpine meadows, resulting in slope soil erosion. Currently, there is a lack of research on the erosion mechanisms of these two soil layers under different slope gradients after engineering disturbance, which hinders erosion prevention and control in this region. MethodsSoil samples from the eluvial and parent material layers of typical subalpine meadows in Xundian county, Yunnan, were collected. Indoor simulated rainfall experiments were conducted under a rainfall intensity of 90 mm/h and three slope gradients (8°, 15°, and 25°). The runoff characteristics, erosion rate (Dr), and hydrodynamic parameters such as Reynolds number (Re), Froude number (Fr), resistance coefficient (f), runoff shear stress (τ), and runoff power (ω) of the two soil layers were monitored and analyzed. Results1) Regarding runoff and Dr, the runoff yield of the parent material layer was 6.53% to 21.74% higher than that of the eluvial layer at the same slope gradients. The Dr of the eluvial layer increased linearly with slope, increasing by 257% (from 8.44 to 30.34 g/(m2·min)) from 8° to 25°. At 8°, the Dr of the parent material layer (10.4 g/(m2·min)) was slightly higher than that of the eluvial layer; however, the rate of increase slowed significantly after the slope exceeded 15°, with an overall increase of only 104% (from 10.4 to 21.28 g/(m2·min)) from 8° to 25°. 2) Regarding hydrodynamic parameters, the Re of the parent material layer was 33.76% and 20.87% lower than that of the eluvial layer at 8° and 25°, respectively. The Fr of the parent material layer was 68.62% lower at 8° but increased by 17.74% at 25°. The f of the eluvial layer exhibited a "V"-shaped trend across the three slopes, reaching its minimum at 15°, whereas the parent material layer exhibited an "∧"-shaped pattern, peaking at 15°. The increase in τ with slope for the eluvial layer (2.75 times) was significantly higher than that for the parent material layer (1.65 times). ω at 25° was 3.76 times higher than that at 8°, and the fitting degree of ω with Dr (R2 = 0.39−0.85) was superior to that of the parent material layer (R2 = 0.43−0.69). ConclusionsThe eluvial layer is more sensitive to external hydrodynamic conditions, with significantly intensified erosion at slope gradients greater than 15°. The parent material layer shows a decelerating trend in erosion increase as the slope gradient exceeds 15°. Therefore, attention should be focused on runoff concentration and gully erosion occurrence within the slope gradient range around 15°, and surface roughening and drainage management should be strengthened in this slope zone.
ObjectiveSoil moisture, as a key factor limiting vegetation growth on the Loess Plateau, further affects regional ecological restoration effectiveness by regulating plant uptake of soil elements. MethodsThis study investigated the coupling relationships between soil moisture and macronutrients (N, P, K, Ca, Mg), micronutrients (Fe, Cu, Mn, Zn, Ni), and non-essential elements (Cr, Pb, Cd, Al, Na) in soils and needles of Pinus tabuliformis forests with different stand ages (8, 10, 12, and 16 years) in rocky mountain area of the Loess Plateau. ResultsSoil moisture content in P. tabuliformis forests initially increased and then decreased with stand age. Additionally, soil moisture content in the 0−10 cm soil layer (9.52%−13.59%) was generally higher than that in the 10-20 cm soil layer (7.84%−12.23%) across different stand ages. Soils with different stand ages contained relatively high proportions of macronutrients K (19%−69%), Ca (10%−69%), and Mg (10%−23%), as well as the micronutrient Fe (97%−99%) and non-essential elements Al (68%−89%) and Na (11%−32%). Significant differences in elemental concentrations were observed among different stand ages and soil layers. Needles of P. tabuliformis contained relatively high proportions of macronutrients N (32%−43%), P (4%−32%), K (11%−26%), and Ca (6%−34%), as well as the micronutrients Fe (76%−90%) and Mn (4%−18%), and the non-essential elements Na (68%−83%) and Al (16%−31%). Among these elements, the concentrations of P, Ca, Mn, Cd, and Na were relatively sensitive to changes in stand age. P. tabuliformis exhibited strong absorption capacity for N and P across different stand ages. It showed strong enrichment effects for N, Mg, Mn, and Na under drought conditions, suggesting a certain degree of drought tolerance. ConclusionsSoil moisture significantly affects the elemental accumulation processes of P. tabuliformis forests. Therefore, rational regulation of soil moisture and elemental levels is essential for maintaining the health and stability of P. tabuliformis forest ecosystems.
ObjectivePlant-derived residue carbon (PRC) is a core component of soil organic carbon (SOC), and its transformation process directly determines the stability of farmland carbon pools. Biochar has been widely applied to enhance soil carbon sequestration capacity, yet its regulatory mechanism for plant-derived residue carbon remains unclear. MethodsThis study was conducted in farmland of the Yellow River Delta, with ten biochar treatments established using different application rates (0, 4, 8, and 12 t/hm2) and frequencies (annual, biennial, one-time application) to analyze their effects on SOC, lignin phenols, and lignin phenol degradation. ResultsAll biochar treatments significantly increased SOC content by 15.2% to 52.2%, compared to the control. However, the SOC increase in most treatments was not attributable to the promotion of PRC transformation. The regulation of lignin phenols by biochar exhibited strict application rate-frequency specificity. Only annual application of 8 t/ha and biennial application of 4 t/hm2 significantly increased total lignin phenol content by 30.2% and 36.6%, respectively. In contrast, the biennial application of 12 t/hm2 biochar and one-time biochar application treatments significantly increased the acid/aldehyde ratios of vanillyl phenol and syringyl phenol monomers, indicating accelerated lignin phenol degradation and reduced PRC retention.ConclusionsBiochar regulates the transformation and retention of PRC in farmland soils of the Yellow River Delta through the coupled effects of application rate and frequency. Considering environmental and economic benefits, biennial application of 4 t/hm2 biochar effectively maintains the balance between degradation and accumulation of lignin phenols and enhances SOC stability. The findings provide a theoretical basis for regional farmland carbon sequestration and optimizing biochar application strategies.
ObjectiveSoil erosion poses a global threat to ecological and agricultural sustainability. In 2024, soil erosion affected 15.70% of Hubei province's total land area. While the RUSLE model is widely used as an empirical statistical model, the value of its key parameter—the soil and water conservation practice factor (P)—is mainly determined based on literature-derived experience and land use types, leaving room for improvement in accuracy. Although field runoff plot observations can provide critical data for the P factor, existing studies are often limited to single measures or short-term observations. Moreover, the data are mostly used for model validation, failing to systematically optimize the P factor. This study aims to systematically optimize the P factor values in the RUSLE model, enhance the simulation accuracy of the RUSLE model, and evaluate its impact on the simulation accuracy using measured data. MethodsThis study obtained a series of P values based on the definition of P, utilizing runoff plot monitoring data from different soil and water conservation practices across Hubei province. Layer-by-layer integration of DEM, soil type, land use, vegetation cover, and terraced field datasets was performed, and the obtained P values were assigned to corresponding grid cells to optimize the P factor values. To validate the accuracy of the optimized model, the predicted values were compared with measured values using the coefficient of determination (R2) and root mean square error (RMSE) for each runoff plot. Additionally, the simulation accuracy was evaluated by comparing pre- and post-optimization model predictions with measured soil loss quantities across small watersheds. ResultsThe results showed that: 1) high P values (P ≥ 0.600) were distributed in western, northeastern, and southeastern Hubei province, while low P values (P < 0.300) were concentrated in the central plain area. 2) The average value of the optimized P factor was 0.457, representing a decrease of approximately 10.42% compared with the original value. 3) The accuracy assessment based on runoff plot observation data showed that R2 was 0.816, RMSE was 214.6, and the relative error was 11.22%, with 98% of the data points in the optimized RUSLE predictions falling within the 95% prediction band. 4) The accuracy assessment based on small watershed monitoring data showed that the optimized simulation accuracy reached 86.630%, an improvement of 9.798% over the pre-optimization results. The proportions of severe erosion, extremely intense erosion, and intense erosion before optimization were all higher than those after optimization. This was due to the excessively high values assigned to the P factor before optimization. ConclusionsIt is feasible to use the measured data from runoff plots combined with multi-source data to optimize the P factor values. The optimized P factor values are more consistent with the configuration of soil and water conservation practices in the study area, which significantly improves the simulation accuracy of the RUSLE model. The findings provide strong support for optimizing RUSLE model factors and for regional soil erosion research.
The northern sand prevention belt is a key area for combating sandification and desertification in China. This region is characterized by arid conditions, water scarcity, barren soil, severe desertification, and salinization, with prominent conflicts between open-pit mining and ecological conservation. Taking the large-scale open-pit mining areas in Inner Mongolia, which have the largest area and production capacity in the northern sand prevention belt, as the research object, this study adhered to the systematic engineering concept of addressing both symptoms and root causes. Following the research framework of "damage-reduction mining → three-dimensional water conservation → soil construction and activation → systematic restoration → integrated supervision" this study adopted a whole-chain integrated technical route of ''theoretical research → technology development → equipment development → integrated demonstration → promotion and application''. Key scientific issues in large-scale open-pit mining areas of the northern sand prevention belt were analyzed, including ecological degradation mechanism, damage-reduction mining mechanism, and ecological self-maintenance mechanism. A technical system was developed and established for ecological damage reduction, protection, and restoration in these mining areas. The research results will contribute to achieving damage-reduction mining, scientific restoration, precise management and control, and self-maintenance of ecosystems in large-scale open-pit mining areas, as well as constructing ecological protection-oriented coal bases and an important ecological security barrier in northern China.
ObjectiveAiming at the limitations of traditional cross-section methods in the special survey of check dam siltation on the Loess Plateau, such as sparse spatial sampling, rough interpolation, and channel morphology interference, this study systematically evaluates the applicability of three spatial interpolation methods—Kriging, inverse distance weighting (IDW), and spline function method—and proposes a high-precision algorithm for calculating siltation volume. MethodsTaking typical gullies in the hilly-gully region of the Loess Plateau as the research objects, based on high-resolution DEM data, the theoretical channel baseline was generated. The elevation points outside the siltation area and node data of the thalweg were merged, and three interpolation methods were used to reconstruct the channel DEM, respectively. The closed volume between the specified siltation elevation and the DEM was calculated to represent the silted storage capacity. Nine check dams in Yulin and Yan'an cities of Shaanxi province were selected to compare the simulation results of this method with those of the traditional cross-section methods at different elevations. ResultsThe Kriging method showed the best performance in gully microtopography restoration and storage capacity calculation, with a DEM reconstruction root mean square error (1.54 m) significantly lower than that of IDW (5.67 m) and the spline function method (2.32 m). In the calculation of siltation volume, the absolute deviation rate of the Kriging method was 5.78%, which was significantly better than that of the spline function method (16.03%), IDW (46.40%), and the optimized cross-section method with 2.5 m spacing (13.27%). The absolute deviation rate of the Kriging method was 1.06%–8.33% in the low elevation range (≤ 10 m), and increased nonlinearly to 15.80%–19.63% when the elevation exceeded 20 m, showing significant elevation dependence. ConclusionsThe Kriging method can effectively improve the calculation accuracy of siltation volume by quantifying the spatial heterogeneity of topography through a variogram, but its deviation rate increases nonlinearly with the increase of elevation. In the future, the error should be optimized using methods such as segmented slope correction and data fusion.
ObjectiveThis study aims to evaluate the effectiveness of a composite practice consisting of a hillside ditch and a daylily (Hemerocallis citrina) vegetative hedgerow in controlling soil erosion and nitrogen and phosphorus losses on sloping cropland in the red soil region of southern China. MethodsField experiments were conducted on red soil sloping cropland at the Jiangxi Soil and Water Conservation Ecological Science and Technology Park. Treatment plots with the composite practice and untreated control plots were established under a summer peanut (Arachis hypogaea)–winter rapeseed (Brassica napus) rotation system. Runoff and sediment yield characteristics, as well as nitrogen and phosphorus losses, were systematically investigated under different rainfall amounts, rainfall intensities, and fertilization stages. ResultsCompared with the control plots, the treatment plots showed significant mitigation effects. 1) Under moderate and heavy rainfall conditions, the average surface runoff depth was reduced by 28.82% and 39.57%, respectively, and the average soil loss was reduced by 46.76% and 73.39%, respectively. 2) Under rainfall intensities of < 1 mm/h, 1–5 mm/h, and > 5 mm/h, the average surface runoff depth decreased by 46.49%, 41.92%, and 11.99%, respectively, while the average soil loss decreased by 30.74%, 69.36%, and 59.47%, respectively. 3) As rainfall amount increased from moderate to heavy, the reduction rate of dissolved nitrogen loss in the treatment plots showed a downward trend, decreasing from 31.01%–39.07% to 21.98%–36.87%, whereas that of dissolved total phosphorus loss increased from 14.73% to 46.57%. As rainfall intensity increased from < 1 mm/h to > 5 mm/h, the reduction rate of dissolved nitrogen loss decreased from 45.02%–57.72% to 8.03%–39.97%, whereas that for soluble phosphorus loss increased from 4.25% to 26.66%. 4) Within 30 days after fertilization, the treatment plots reduced nitrogen and phosphorus losses by 7.42%–32.08%. After 30 days, the reduction rate further increased, reaching a maximum of more than 39%. ConclusionsThe composite practice of hillside ditch and daylily vegetative hedgerow effectively reduces runoff and sediment yield, and nitrogen and phosphorus losses on red soil sloping cropland in southern China. These findings provide a scientific basis for the wider promotion and application of this conservation practice.
ObjectiveThis study aims to scientifically evaluate the operational risk level of check dams on the Loess Plateau in Inner Mongolia, thereby providing theoretical support for risk warning and engineering management of check dams in this region. MethodsFirst, a multi-dimensional and hierarchical risk evaluation indicator system was constructed by identifying key influencing indicators using the decision-making trial and evaluation laboratory (DEMATEL) method. Second, the weights of the indicators were determined separately via the fuzzy analytic hierarchy process (FAHP) and the order relation analysis (G1) method, and game theory was applied for weight fusion to ensure the rationality of weight allocation. Finally, quantitative assessment was performed based on the cloud model. Specifically, the cloud characteristic values of the indicators were calculated using the backward cloud generator, and the comprehensive evaluation cloud was generated by combining indicator weights with the forward cloud generator. Additionally, cloud similarity was introduced to quantify the membership degree of the comprehensive evaluation cloud to different evaluation grades. ResultsAn empirical analysis was conducted with the Housha Check Dam in Inner Mongolia as the research object, and the results showed that the operational risk evaluation level of the check dam was “basically safe,” with a normalized membership degree of 70.5%. This result was highly consistent with those obtained using the fuzzy comprehensive evaluation method and the set pair analysis method and matched the actual engineering situation. ConclusionsThis study confirms that the constructed evaluation system and method are effective and reasonable. It can accurately reflect the operational safety and risk status of check dams, and provide reliable references for risk management and control of check dams in similar regions.
ObjectiveIn the context of global climate change, drought has become a critical issue on the global governance agenda. This study aims to examine the evolutionary trajectory of drought issues within the framework of the United Nations Convention to Combat Desertification (UNCCD), and to analyze China's role positioning and selected pathways of engagement in the relevant negotiations. MethodsFrom the perspective of international regime effectiveness, this study adopted a combination of process tracing, SWOT (strengths, weaknesses, opportunities and threats) analysis, the best-worst method (BWM), and Boston Matrix analysis to evaluate China's negotiation behavior on drought issues across the Conference of the Parties (COP1-COP16), operationalized through two primary dimensions: willingness to participate and capacity to participate. ResultsThe results showed that the drought agenda under the UNCCD progressed through five distinct stages: the initial regime-building stage, the monitoring initiation stage, the scientific support stage, the agenda-upgrading stage, and the deep governance stage. The thematic focus shifted progressively from institutional frameworks and monitoring and assessment toward science-policy interfaces, operational mechanism development, and multilateral cooperation. In the drought negotiations, China's role gradually evolved from an ordinary participant, to an active participant, a contributor, a promoter, and ultimately to a leader. Correspondingly, its matrix position shifted from "low willingness-low capacity" during COP1-COP9, to "relatively high willingness-relatively high capacity" during COP10-COP11, and then to "high willingness-high capacity" during COP12-COP16. Overall, China's strategic pathway exhibited a gradual evolutionary pattern characterized by "willingness taking the lead, capacity following suit".ConclusionsIn conclusion, China should adopt measures such as "improving internal capacity building" "strengthening external risk response" and "enhancing negotiation capacity", so as to contribute a "Chinese solution" to institutional progress and international consensus-building under the drought agenda framework of the UNCCD.
