• Volume 0,Issue 3,2024 Table of Contents
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    • Influence of Headcut Height on the Developmental Processes of Gully Bed Plunge Pool on a Granite Red Soil Slope

      2024, 38(3):1-11. DOI: 10.13870/j.cnki.stbcxb.2024.03.035

      Abstract (32) HTML (2) PDF 6.42 M (1171) Comment (0) Favorites

      Abstract:[Objective] Headcut bed plunge pool point development is a key process in headcut erosion on granitic red soil slopes, but the mechanism of its formation is not clear. [Methods] We investigated the process of gully bed plunge pool development on granite red soil slopes by setting five headcut heights (25, 50, 75, 100 and 125 cm). [Results] (1) As the height of the headcut increased, the Re, τ, ω and the jet parameters (Vbottom, τmax, EKbottom, and ΔEH) showed an increasing trend. (2) After the laterite soil layer scouring to form a "V" type of small plunge pool, with the increase in the flow of the form of plunge pool gradually increased, but it is difficult to form a large area of the plunge pool, and the laterite soil layer is more stable than the sandy soil layer. During the scouring process of the sandy soil layer, the development of headcut bed drop points was more obvious, and when the flow rate increased to 120 L/min, the degree of gully bed fragmentation was gradually drastic, and the outline of the drop points was gradually clearer, and the cross-sectional area increased. (3) The random forest algorithm and Shapley values were used to construct the model and characterize the relationship between the parameters. The results showed that in the laterite layer, Fr, ω, EKbrink, and Re were negatively correlated with the cross-sectional area; and in the sandy soil layer, Fr and ΔEH were negatively correlated with the cross-sectional area. Higher accuracy of predictive models constructed by the random forest algorithm (LCCC=1.02, R2adjusted=0.876 and 0.868). [Conclusion] The results of the study can provide a theoretical basis for revealing the mechanisms of headcut erosion and gully erosion control.

    • Effects of Wind Speed on the Characteristics of Rill Erosion on Windward Slope Under Rainfall Conditions

      2024, 38(3):12-18,28. DOI: 10.13870/j.cnki.stbcxb.2024.03.014

      Abstract (31) HTML (2) PDF 1.19 M (1187) Comment (0) Favorites

      Abstract:[Objective] This study was aimed to elucidate wind-induced rill erosion characteristics on the windward slope. [Methods] Artificial simulated wind-driven rain experiments were conducted. The study investigated changes in water and sediment processes as well as rill morphology under different wind speed conditions (0, 3, 5, and 7 m/s). [Results] Compared to slopes without wind, the windward slope exhibited a 20.59%~47.06% increase in flow generation time and a 33.10%~137.78% increase in the occurrence of falling ridges. The average slope flow velocity decreased by 12.86%~22.53%. Runoff and sediment production rates notably decreased with increasing wind speed (p < 0.05). The runoff production rate on windward slopes followed a similar trend under different wind speeds, gradually increasing with rainfall before stabilizing over time, with no significant differences observed among stages at different wind speeds. Sediment yield rates increased rapidly with prolonged rainfall duration, followed by a gradual decrease and stabilization. Nodes of sediment yield rate changes aligned closely with the occurrence of falling ridges. Rill dimensions (width, depth, fluctuation degree) decreased with rising wind speed. The width-depth ratio and rill inclination ranged from 1.40 to 1.69 and 13.47 to 14.76 degrees, respectively, increasing with higher wind speeds. Under various wind speed conditions, rill volume, splitting degree, and density ranged from 4.39 to 10.27 cm3, 0.024 to 0.042, and 2.03 to 2.92 m/m2, respectively, all decreasing with increasing wind speed. [Conclusion] The volume, density and degree of fragmentation of rills are all significantly positively correlated with the amount of slope erosion, making them the preferred indicators for characterizing the morphology of rills on windward slopes.

    • The Impact of Flexible Vegetation Lodging on the Hydraulic Characteristics of Surface Runoff and Erosion

      2024, 38(3):19-28. DOI: 10.13870/j.cnki.stbcxb.2024.03.011

      Abstract (16) HTML (1) PDF 3.44 M (1164) Comment (0) Favorites

      Abstract:[Objective] This study was aimed at exploring the influence of nearsurface coverage formed by the collapse of flexible vegetation in reducing runoff and erosion yield, and in modulating the hydraulic properties of surface runoff. [Methods] Based on fundamental principles of fluid mechanics and hydraulics, the erosion patterns and hydrodynamic characteristics under lodged flexible vegetation were systemically investigated through indoor hydrodynamic experiments across five levels of coverage, five slope gradients, and three flow rates. [Results] (1) The distribution of erosion volume demonstrated an initial increase followed by a decrease with the increment of slope angle, with the influence of flow rate on the erosion process being more pronounced at steeper slopes. (2) Corresponding to an increase in the coverage of flexible vegetation, and taking 50% coverage as a threshold, the erosion volume generally exhibited a trend of initial reduction followed by an increase. (3) The average flow velocity (v) decreased with increasing vegetative coverage, with the rate of decline becoming gradual as coverage intensified. The variation in Froude number (Fr) mirrored the trend in average flow velocity. The friction coefficient (f) was positively linear correlated with coverage and decreased with an increase in slope gradient; the Reynolds number (Re) demonstrated a higher sensitivity to soil erosion compared to Fr, v, and f. (4) With the increase in vegetation coverage, morphological shear stress intensified (while particle shear stress diminished), playing a pivotal role in the changes in total shear stress, which was positively correlated with vegetation coverage. [Conclusion] The study establishes a solid theoretical foundation for the erosion patterns of slope flow vegetation and facilitates the expansion of open channel hydraulic theories in the realm of slope flows.

    • Performance of Artificially Transplanted Biocrusted Soil-surfaces in Rainwater Harvesting and Their Capability to Resist Erosion in the Hilly Region of Chinese Loess Plateau

      2024, 38(3):29-36. DOI: 10.13870/j.cnki.stbcxb.2024.03.038

      Abstract (19) HTML (1) PDF 1.24 M (1168) Comment (0) Favorites

      Abstract:[Objective] The purpose of the study was to explore the rainwater harvesting effect and erosion damage resistance of different types of artificial biocrusted soil surfaces in the hilly region of Chinese Loess Plateau. [Methods] The biocrusted soil surfaces were taken as the research object, and the bare soil surfaces as the control. The study conducted field simulated rainfall and erosion resistance experiments (slope scouring, soil disintegration, and single raindrop splash erosion experiments) on them, respectively. Differences in the erosion resistance among different types of soil surfaces were analyzed. [Results] (1) Biocrusted soil surfaces significantly improved rainwater harvesting efficiency. At a rainfall intensity of 100 mm/h, the rainwater harvesting efficiency of the biocrusted soil surfaces was significantly increased by 33.3% compared to bare soil (F = 300.12, p < 0.001). (2) Biocrusted soil surfaces significantly reduced the sand production and increased the coefficient of erosion resistance. Compared with bare soil, the sand production of cyano and moss biocrusted soil surfaces was reduced by 178.8% and 364.6%, respectively. Compared to bare soil, moss and cyano biocrusts had 4.6 and 2.8 times, respectively, the maximum coefficients of resistance to washout. (3) Biocrusts significantly reduced the soil disintegration rate and maximum disintegration rate, and the differences were significant. Compared with bare soil (6.46 g/min), the disintegration rates of cyano and moss biocrusts were reduced by 35.0% and 60.2%, respectively and the maximum disintegration rate of biocrusts was reduced by 23.8%. (4) Biocrusts significantly increased the raindrop kinetic energy and reduced soil spallation. The critical kinetic energy of moss and cyano biocrusts was 3.9 and 21.9 times higher than that of bare soil (0.5 J), respectively. Meanwhile, the soil splash erosion of the biocrusts was reduced by 75.3% on average compared to bare soil (0.156 g). [Conclusion] Biocrusted soil surfaces significantly improved the erosion resistance and rainwater harvesting effect, which is of great significance in terms of sustainable utilization and soil and water conservation in dry areas.

    • Temporal and Spatial Changes of Soil Erosion and Its Response to Landscape Pattern in Dabie Mountains of Western Anhui in Recent 30 Years

      2024, 38(3):37-44. DOI: 10.13870/j.cnki.stbcxb.2024.03.013

      Abstract (15) HTML (1) PDF 2.17 M (1163) Comment (0) Favorites

      Abstract:[Objective] The Dabie Mountain area in western Anhui Province is an important ecological transition area between the Yangtze River Basin and the Huaihe River Basin in Anhui Province. The study on the landscape pattern and soil erosion and their relationship in this area is helpful to provide a reference for the regulation of landscape pattern and soil erosion control in this area. [Methods] The RULSE model was used to calculate the soil erosion modulus in the Dabie Mountains of western Anhui in the recent 30 years. The changes of landscape pattern were described by landscape index, and the influence of landscape index on soil erosion was explored by partial least squares regression (PLSR). [Results] In recent 30 years, the soil erosion modulus showed a trend of decreasing first and increasing later. The areas with serious soil erosion were mainly concentrated in the central and western regions and the southern mountainous areas. In most areas, the soil erosion intensity was mainly slight and mild, and the erosion intensity of different land use types had obvious difference, which was grassland > cultivated land > forest land. The land use type and landscape pattern were generally stable. The change of landscape pattern was mainly manifested in the reduction of landscape fragmentation and the improvement of landscape heterogeneity and connectivity. Shannon’s Diversity Index (SHDI), Edge Density Index (ED), Proportion of Like Adjacencies (PLADJ), and Landscape Shape Index (LSI) had significant explanatory significance for the Dabie Mountain area in west Anhui Province. Shannon’s Diversity Index (SHDI), Edge Density Index (ED), and Landscape Shape Index (LSI) had significant positive effects on soil erosion, while Proportion of Like Adjacencies (PLADJ) had significant negative effects on soil erosion. [Conclusion] In the Dabie Mountains of western Anhui, the increase of landscape fragmentation and the decrease of landscape connectivity will significantly promote soil erosion.

    • Study of the Rheological Behavior of Pisha Sandstone Slurry Based on Dynamic Oscillatory Shear

      2024, 38(3):45-53. DOI: 10.13870/j.cnki.stbcxb.2024.03.007

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      Abstract:[Objective] With global warming and increased occurrences of heavy precipitation, the frequency of landslide mudflow disasters in the Pisha sandstone area will increase significantly. Understanding how water-soil interaction affect the loosening and deformation of fragile soils, ultimately leading to mudflow development, is a crucial scientific question in the evolutionary process. [Methods] This study focuses on investigating the rheological properties of Pisha sandstone (PS) slurry using a rheological method that involves dynamic oscillatory shear. The primary objective is to examine the liquefaction process and initial rheological properties of PS slurry. [Results] (1) With the increase of shear strain, the energy storage modulus (G') and loss modulus (G″) of the four PS slurries decreased and exhibited strain thinning characteristics. (2) In the samples with lower water content (w<50%), the stress and strain in the linear viscoelastic region (LVE) of purple and brown PS slurries were larger than red and white PS slurries. In the samples with higher water content (w≥50%), the stress and strain at the flow point of red and white PS slurries were larger than purple and brown PS slurries. (3) With increasing water content, G' and G″ of the four PS slurries decreased, and the stress and strain in the LVE decreased. [Conclusion] Fine particles could increase the shear strength and elasticity of the slurry in the LVE, but the fine-grained slurry was more affected by the moisture content, and the ability of the slurry structure to destroy and resist deformation was weakened immediately after the addition of water, while the phase transition was more likely to occur. The presence of coarse particles increased the extent of the elastic dominance of the nonlinear viscoelastic region and hindered the phase transition of the slurry. The results of the study can provide scientific basis for further mudflow research and disaster control in the Pisha sandstone area.

    • Simulation and Analysis of Hydraulic Erosion in Sloping Farmland Based on Gradient Boosting Decition Tree Mode

      2024, 38(3):54-63. DOI: 10.13870/j.cnki.stbcxb.2024.03.008

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      Abstract:[Objective] This article employs machine learning to quantitatively analyze soil water erosion in Loess Plateau slope farmland, addressing its complexity and quantification challenges due to human interference. We aim to simulate erosion characteristics, explore its mechanisms, and support erosion prediction. [Methods] Using 1959-1969 data from Zizhou Experimental Station, we characterized the influencing factors and analyzed erosion and runoff depth changes with a gradient boosting decision tree. [Results] The dataset showed significant variability in secondary rainfall erosion (0~122.72 t/km2), runoff depth (0.02~17.20 mm), rainfall duration (2~1 410 min), and average intensity (0.02~4.63 mm), often right-skewed. The erosion model (R2=0.81) slightly outperformed the runoff depth model (R2=0.80), despite its greater complexity (8 layers vs. 5). Using the gradient boosting tree model and SHAP algorithm, we found differing key factors for erosion and runoff. [Conclusion] Limitations in feature extraction lead to less accurate predictions for small erosion and runoff depths. Future research should explore more independent variable combinations to enhance predictions. Main influencing factors differ between runoff and sediment production. Precipitation mainly influences runoff, while erosion and sediment production depend on precipitation and terrain-related variables. In summary, this data-driven study illuminates slope farmland erosion mechanisms on the Loess Plateau, providing a scientific basis for erosion control in the region.

    • The Relationship Between Soil Crust and Infiltration Under Simulation Continuous and Intermittent Precipitation

      2024, 38(3):64-72,81. DOI: 10.13870/j.cnki.stbcxb.2024.03.012

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      Abstract:[Objective] This study was aimed at investigating the variation relationship between soil crust and infiltration performance under continuous and intermittent rainfall conditions. [Methods] Three typical cultivated layer loesses were selected, and indoor simulated rainfall experiments were conducted to analyze the relationship between soil crust strength, cohesion, and infiltration performance under different rainfall conditions. [Results] (1) The infiltration performance decreased with the increase of continuous rainfall duration and intermittent rainfall events; under the same rainfall duration and intensity, the desilting effect of intermittent rainfall was higher than that of continuous rainfall. (2) Soil crust strength and cohesion increased with the increase of continuous rainfall duration and intermittent rainfall events; the infiltration performance of cinnamon soil and black earth was significantly linearly correlated with crust strength and cohesion (p < 0.05). The longer the continuous rainfall duration and the more frequent the intermittent rainfall events, the greater the soil crust strength, cohesion, and desilting effect. The infiltration performance of sandy soil was significantly nonlinearly correlated with crust strength and cohesion (p < 0.05). (3) The smaller the MWD and GMD of the crust, the worse the infiltration performance and the greater the desilting effect; furthermore, the correlation analysis results showed that the impact of intermittent rainfall on infiltration performance is higher. [Conclusion] Finally, under the same rainfall intensity, intermittent rainfall can form a more solid crust, which has a stronger weakening effect on soil infiltration performance. This study can provide a reference for the prevention and control of soil and water loss on the Loess Plateau and the effective utilization of water resources

    • Effects of Biological Soil Crusts Development on Soil Erosion Resistance on Loessial Soil

      2024, 38(3):73-81. DOI: 10.13870/j.cnki.stbcxb.2024.03.004

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      Abstract:[Objective] The extensive development of biological soil crusts driven by the project of "Grain for Green" on the Loess Plateau can significantly inhibit soil erosion, but the characteristics of soil erosion resistance and the response mechanism with the growth and development of biological soil crusts are still unclear. [Methods] Algal crusts, moss crusts, and natural succession crusts were cultivated for 176 days to systematically study the effects of different developmental stages and types of biological soil crusts on loessial soil erosion resistance. [Results] (1)The coverage, thickness, biomass, chlorophyll and roughness of the biological soil crusts increased significantly with growth time, and the moss crusts were higher at the beginning of cultivation and the natural succession crusts were highest at the end of cultivation.(2)With the development of biological soil crusts, the cohesion increased as a power function, which increased by 39.8%~60.3% compared with the initial period; the mass loss rate decreased exponentially, which decreased by 45.6%~57.3% compared with the initial period; and the saturated hydraulic conductivity(Ks)was more complex, but the Ks was lowest at the end of cultivation(0.08~0.12 mm/min).(3)Soil cohesion increased as a power function with the increase of coverage, thickness, chlorophyll, biomass and roughness, and the mass loss rate decreased exponentially with the increase of coverage, thickness, chlorophyll, biomass and roughness. (4) The comprehensive index of soil erosion resistance (Cser) constructed based on soil properties can effectively show the effect of biological soil crusts development on soil erosion resistance. And the Cser can be expressed as a power function of coverage (Cov), thickness (T) and biomass (B) (Cser=0.279 Cov0.194 T0.188 B0.119, R2=0.73, p<0.05). [Conclusion] The development of biological soil crusts on the Loess Plateau can significantly improve soil erosion resistance, and the effect of moss crusts is the best.

    • Impacts of Rainfall Characteristics and Vegetation Cover Patterns on Slope Runoff and Sediment Yields in the Three Gorges Reservoir Area

      2024, 38(3):82-90,100. DOI: 10.13870/j.cnki.stbcxb.2024.03.020

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      Abstract:[Objective] This study was aimed to explore the impacts of rainfall characteristics and vegetation cover patterns on slope hillslope runoff and sediment yields in the Three Gorges Reservoir area, and to adapt to the new needs of the prominent contradiction between man and land and the development of rural industries for the optimal utilization of underforest land resources. [Methods] Taking a typical fallow forest in the Three Gorges Reservoir area as the research object, four runoff plots with full-slope herbaceous cover (QF), upper-slope bare ground + lower-slope herbaceous cover (XF), equidistant herbaceous strip cover (TF), and full-slope herbless coverage (WF), were set up to carry out field observation of slope runoff and sand production in 24 erosive rainfall events and to identify the effects of erosive rainfall and vegetation cover patterns on hillslope runoff and sediment yields. [Results] (1) The 24 erosive rainfall events were classified into three categories, including A-type (small rainfall, heavy rainfall intensity, and short duration), B-type (large rainfall, heavy rainfall intensity, and short duration), and C-type (small rainfall, light rainfall intensity, and long duration). A-type was the rain type with the highest occurrence frequency at 45.83%. The cumulative rainfall of B-type was the largest, accounting for 63.44% of the total rainfall. (2) The cumulative runoff depth and cumulative erosion volume of the four vegetation cover patterns generally showed QF < XF < TF < WF; The peak value of runoff depth and erosion volume all occurred in B-type rainfall, which led to an increase in runoff depth of 337.74%~410.32% and an increase in erosion volume of 283.47%~504.58% compared to A-type rainfall. (3) The proportion of runoff depth and erosion amount produced by the WF was 75.75% and 98.51%, while XF and TF accounted for only 12.20% and 1.08%, 7.28% and 0.34%, respectively. Compared with WF, the runoff interception and reduction of XF and TF were 84.18% and 75.85%, and the sediment interception and reduction were 96.99% and 93.30%, respectively. [Conclusion] By comparing the runoff and sediment yields of runoff plots under different vegetation cover patterns, it was found that the modes of upper-slope tillage + lower-slope l herbaceous coverage, strip tillage + contour hedgerow can take into account the functions of water regulation and soil conservation of forest land and ecological planting of understory, which can provide a theoretical basis for ecological restoration and the optimal utilization of understory land resources in the Three Gorges Reservoir area.

    • Comparison of Erosion Monitoring Methods in the Pisha Sandstone Areas of the Chinese Loess Plateau Based on UAV-SfM Data

      2024, 38(3):91-100. DOI: 10.13870/j.cnki.stbcxb.2024.03.030

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      Abstract:[Objective] To compare the applicability of terrain change monitoring algorithms in the pisha sandstone areas of the loess plateau. [Methods] A branch gully Telagouagou Huangfuchuan was taken as the research object, including digital elevation model of difference (DoD), cloud to cloud (C2C), cloud to mesh (C2M), and multiscale model to model cloud comparison (M3C2). Point cloud data employed to operate the four algorithms were produced using the SfM technique based on images acquired by UAV between July 2022 and March 2023. The impact of point density changes in the accuracy of the employed algorithms was also investigated. [Results] (1) All four algorithms were capable of effectively monitoring large surface changes. Among them, the M3C2 algorithm performed the best with the highest accuracy (R2=0.953, p<0.01) and the lowest error (MAE=0.016 1 m, MRE=3.37%, RMSE=0.019 4 m), followed by the C2M algorithm, DoD algorithm, and C2C algorithm. (2) The DoD algorithm was only suitable for flat areas and yielded overestimated results for steep sloping areas. (3) The M3C2 and C2C algorithms were sensitive to point cloud density, while the C2M and DoD algorithms were less sensitive. [Conclusion] The study provided a useful reference for the selection of erosion monitoring methods for the Pisha sandstone areas.

    • Soil Organic Carbon and Moisture Effects of Different Vegetation Restoration Types in the Mu Us Sandy Land

      2024, 38(3):101-110,120. DOI: 10.13870/j.cnki.stbcxb.2024.03.006

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      Abstract:[Objective] This study was aimed to explore the characteristics of soil organic carbon and moisture content under different vegetation restoration types and their relationships, and to provide a scientific basis for the selection of vegetation restoration models in the Mu Us sandy land. [Methods] Different vegetation restoration types, including natural restoration of grassland and various plants such as Artemisia desertorum, Salix psammophila, A. desertorum S. psammophila mixed (shrub-shrub mixed), Pinus sylvestris, S. psammophila P. sylvestris mixed (tree-shrub mixed), in the Mu Us sandy land, were studied. Bare sand was used as the control. The effects and correlations of different vegetation restoration types on carbon and water in the 0-5.0 m soil profile were analyzed. [Results] (1) Vegetation restoration increased, with S. psammophila P. sylvestris mixed, P. sylvestris, Grassland, A. desertorum S. psammophila mixed, A. desertorum S. psammophila mixed, and A. desertorum showing decreasing trends, with significant accumulation effects observed within the 0—0.2 m soil depth. As soil depth increased, the organic carbon content of all vegetation types gradually decreased. Within the depth range of 0.8—2.2 cm, A. desertorum, S. psammophila, and A. desertorum S. psammophila mixed exhibited carbon loss. (2) Different vegetation restoration types showed varying degrees of soil moisture deficit in deep soil layers, primarily concentrated at 1—3.0 m soil layer, with S. psammophila P. sylvestris mixed showing the most severe deficit, followed by P. sylvestris, A. desertorum S. psammophila, S. psammophila, Grassland, A. desertorum. (3) Roots were identified as the main factors influencing soil organic carbon content and moisture consumption. Soil organic carbon content exhibited a negative correlation with soil moisture within the 0—5.0 m soil depth range. [Conclusion] Vegetation carbon storage was achieved at the expense of utilizing deep soil moisture, with S. psammophila P. sylvestris mixed exhibiting the lowest water consumption per unit of fixed carbon. The study suggests that S. psammophila P. sylvestris mixed exhibits favorable effects in vegetation restoration from the perspective of soil carbon retention and water retention in the Mu Us sandy land.

    • Response of Soil Detachment Capacity to Concentrated Hydrodynamic Parameters in Citrus Orchards

      2024, 38(3):111-120. DOI: 10.13870/j.cnki.stbcxb.2024.03.033

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      Abstract:[Objective] This study was aimed to explore the mathematical relationship between soil detachment capacity and concentrated water flow hydraulic characteristics parameters in the typical slope orange orchard in the Three Gorges Reservoir Area, and to provide theoretical basis and data support for predicting soil erosion in slope orange orchard. [Methods] Through concentrated flow erosion tests, the soil detachment amount of a clear plowed sample plot and three green manure (Trifolium repens L, Poa annua L, and Vicia sepium L) covered plots under gradient hydrodynamic conditions of different slopes (10°~30°) and flow rates (18~126 L/min) combinations was analyzed. The quantitative relationships between soil detachment capacity of citrus orchard plots and hydrodynamic parameters (water shear force, water power), flow pattern parameters (Reynolds number, Froude number) and resistance parameters (Darcy-Weisbach resistance coefficient, Manning’s coefficient) were explored, and corresponding mathematical models were established. [Results] There was a significant correlation between the soil detachment capacity of green manure coverage and clean cultivation of citrus orchard and various hydraulic parameters. The soil detachment capacity was positively correlated with hydrodynamic and flow regime parameters in a power function (R2 was 0.86~0.99, NSE was 0.88~0.98, p<0.01), and negatively correlated with water flow resistance parameters in a power function (R2 was 0.32~0.60, NSE was 0.39~0.64, p<0.05), indicating that the soil detachment capacity significantly increased with the increasing of hydrodynamic and flow regime parameters, while significantly decreased with the increasing of resistance parameters. [Conclusion] In the citrus orchard covered with green manure or cleared, the predictive effect of water flow shear force on soil detachment capacity was better than that of water flow power. The reynolds number was more effective in predicting soil detachment capacity than the froude number. The prediction effect of Darcy-Weisbach resistance coefficient was better than that of Manning’s coefficient. Overall, the prediction of soil detachment capacity capacity by water flow shear force had the best effect and the highest accuracy (R2 average value was 0.96, NSE average value was 0.96).

    • Effects of Different Grazing Intensities on Vegetation Community Characteristics and Soil Aggregates in Xilamuren Grassland

      2024, 38(3):121-129,139. DOI: 10.13870/j.cnki.stbcxb.2024.03.040

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      Abstract:[Objective] In order to explore the changes of vegetation communities under different grazing intensities in grassland, the effects of community characteristics on soil aggregates were analyzed. [Methods] Taking the controlled grazing experimental area of Xilamuren desert steppe as the research object, the characteristics of vegetation community and soil aggregates under light grazing (LG), moderate grazing (MG), heavy grazing (HG), and no grazing (CK) and their relationship were analyzed by field investigation and indoor analysis, and the effects of plant community changes on soil aggregates were revealed. [Results] (1) The Shannon-Wiener diversity index (H') and Simpson dominance index (D) of LG were significantly lower than those of other grazing intensities (p<0.05). The aboveground biomass decreased with the increase of grazing intensity, and the aboveground biomass of HG was significantly lower than that of other grazing intensities (p<0.05). The underground biomass under different grazing intensities was significantly different, and the underground biomass of different soil layers was the highest in LG. (2) The change trend of mean weight diameter (MWD) and geometric mean diameter (GMD) was consistent with the content of macroaggregates. In 0—5 cm and 5—10 cm soil layers, it increased first, then decreased and then increased with the increase of grazing intensity (LG was the highest and MG was the lowest). (3) Shannon-Wiener diversity index (H'), Pielous evenness index (J'), aboveground biomass, and bulk density were significant factors affecting macroaggregate content, MWD, and GMD (p<0.05). [Conclusion] Grazing intensity had a negative feedback regulation effect on soil aggregate stability, which mainly caused the change of soil aggregate stability by affecting the changes of vegetation community diversity index (H'and J'), aboveground biomass, and soil bulk density. The results provide theoretical support and a scientific basis for the selection of grazing intensity and ecological restoration in Xilamuren grassland.

    • Effect of Rock Strata Dip on Soil Detachment Capacity of Different Land Use Types in Karst Trough Valley Area

      2024, 38(3):130-139. DOI: 10.13870/j.cnki.stbcxb.2024.03.034

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      Abstract:[Objective] This study aimed to explore the influence mechanism of rock strata dip on soil erodibility and provide references for preventing and controlling water and soil erosion in karst trough valley area. [Methods] The study focused on the dip/anti-dip slope of Qingmuguan karst trough valley area in Chongqing city. Through flume erosion experiments, we analyzed the differences in soil erodibility between different land use types on the dip/anti-dip slopes and investigated the impact of soil physicochemical properties on soil erodibility. [Results] (1) Both dip/anti-dip slopes showed a significant negative correlation with organic matter content, >0.25 mm water-stable aggregates content, and total nitrogen content (p<0.05). In particular, the anti-dip slope had higher organic matter content, >0.25 mm water-stable aggregate content, and total nitrogen compared to the dip slope. (2) Soil erodibility was higher on the dip slope than on the anti-dip slope for all four land use types studied. Additionally, grassland had lower comprehensive scores of soil erodibility than pepper fields, cornfields, and bare land on both the dip/anti-dip slopes. (3) Based on stepwise multiple regression analysis results, prediction models for soil erodibility on the dip/anti-dip slopes were established using organic matter content and >0.25 mm water-stable aggregate content as predictors with determination coefficients R2 of 0.77 and 0.85 respectively. [Conclusion] In summary, grassland had the lowest soil erodibility among all land use types studied regardless of the dip/anti-dip slopes in karst trough valley. Therefore, in order to prevent soil erosion and promote ecological restoration in karst trough valley, it is necessary to cultivate the land reasonably and increase grassland coverage appropriately, thus enhancing the soil's resistance against erosion.

    • Hydrological Characteristics and Key Influencing Factors of Typical Lakes in the Qinghai Tibet Plateau from 1985 to 2021

      2024, 38(3):140-149. DOI: 10.13870/j.cnki.stbcxb.2024.03.025

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      Abstract:[Objective] The lakes of the Tibetan Plateau are important indicators of climate change, and their expansion or contraction also have an important impact on the natural environment of the Tibetan Plateau. [Methods] Three typical lakes located in different climatic sub-regions of the Qinghai-Tibet Plateau (Qinghai Lake, Yangzhuo Yongcuo, and Ulan Ula Lake) were selected to study the temporal and spatial variation of the hydrological characteristics of the three typical lakes from 1985 to 2021 by remote sensing monitoring methods, to reveal the role of key climatic factors, and to further explore the influence of glaciers and permafrost on the typical lakes. [Results] The area and water level of Qinghai Lake showed a significant upward trend, with an area increase of 238.68 km2 and a water level increase of 1.32 m. In space, it showed a trend of expansion in the east-west direction. The area and water level of Yangzhuo Yongcuo Lake first fluctuated and then decreased, decreasing by 16.31 km2 and 3.25 m respectively. In space, the overall area showed a shrinking trend from the surrounding to the center. The area and water level of Ulan Ula Lake showed a significant upward trend, increasing by 125.57 km2 and 8.12 m, respectively, and the expansion area was mainly concentrated in the south. [Conclusion] The analysis of key climate factors shows that the lake expansion caused by the increase of precipitation and the accelerated melting of glacial permafrost in the warm and humid environment is the most prominent environmental change characteristics of the Qinghai-Tibet Plateau. The main reason for the rise in the water level of Ulan Ula Lake is the seasonal thaw of permafrost caused by rising temperatures. Exploring the changes in lake area on the Tibetan Plateau is of great guiding significance for in-depth research on global climate change and surface water resource assessment.

    • Simulation and Influencing Factors of Soil Water Storage in the Weihe River Basin Under Changing Environment

      2024, 38(3):150-158. DOI: 10.13870/j.cnki.stbcxb.2024.03.031

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      Abstract:[Objective] With the intensified influence of climate change and human activities, the climate and underlying surface conditions of the basins have changed. Accurately simulating the process of soil moisture change and analyzing its influencing factors are of great significance for regional water resource management and vegetation construction. [Methods] The Weihe River Basin in the Loess Plateau was taken as the research object. Based on the ABCD hydrological model, the EFAST method was used to analyze the parameter sensitivity of the model, and the constant parameter and time-varying parameter models were constructed. The runoff depth and soil water storage simulation accuracy of different parameter models were compared. The effects of climate change and vegetation restoration on soil water storage changes in the Weihe River Basin were discussed, and the dominant factors of soil water storage changes were clarified. [Results] The proportional parameter of soil water layer recharge groundwater c was the most sensitive, followed by the groundwater storage coefficient d, the upper limit parameter b of the sum of actual evapotranspiration and soil water storage, and the tendency parameter a of runoff that before the soil is completely saturated was the least sensitive. Compared with the ABCD constant parameter model, the time-varying parameter model increased the values of NSE, KGE, and R2 of the runoff depth simulation results by 19%, 10%, and 19%, respectively, and the NSE, KGE, and R2 of the verification period increased by 7%, 7%, and 9%, respectively. The time-varying parameter model significantly improved the runoff depth simulation results. The srtongest correlation between soil water storage in the Weihe river basin and ERA 5-Land 0-100 cm soil layer based on time-varying parameter model simulation, and the change process of the two agreed well. The degree of different influencing factors on the change of soil water storage in the Weihe River Basin from strong to weak was potential evapotranspiration>precipitation>NDVI. [Conclusion] The research results provide a scientific basis for water resources planning and management and vegetation construction in this area and they also provide references for soil water storage research in other similar areas.

    • Multi-scenario Simulation and Water Resource Effects of Integrated Utilization of Saline-alkali Land in Western Jilin Province

      2024, 38(3):159-167,176. DOI: 10.13870/j.cnki.stbcxb.2024.03.028

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      Abstract:[Objective] The integrated utilization of saline-alkali land remains a quintessential stratagem to enhance grain yield whilst embracing the principle of Greater Food. The current simplistic reclamation approaches and the intensive water demands, however, call for a thorough investigation of diversified management strategies and interventions that take into account the impact on water resources. [Methods] The study selected the western part of Jilin province as the study area and adopted the FLUS model to forecast the utilization patterns of saline-alkali land resources until 2030 under four scenarios: Natural progression, grain security, integration of grain and forage production, and ecological protection. The InVEST model was then applied to evaluate the variations in water yield across these scenarios. [Results] (1) From 2000 to 2020, 1 540.18 km2 of saline-alkali land in the study area was put to use, predominantly restored to grassland or reclaimed as cultivated land, with a substantial risk of secondary salinization in drylands. (2) Under all scenarios, the reclamation of saline-alkali land for agriculture prevailed. In the grain security scenario, the paddy fields and drylands accounted for 67.48% and 4.23%, respectively. When compared with the natural progression scenario, the grassland area was set to expand by 139.18 km2 in the integration of grain and forage production scenario, and ecological land would increase substantially under the ecological protection scenario. (3) By 2030, water yield is projected to decrease in all four scenarios relative to the baseline period, with the ecological protection scenario facing the steepest reduction at 3.71×108 m3. Conversely, the integration of grain and forage scenario offered a well-balanced solution, ensuring the output of crops and forage while easing the water pressures initiated by the management of saline-alkali land. [Conclusion] Utilization of saline-alkali land in the Songnen Plain requires a balanced and strategic approach that supports both grain and forage production. Efforts should be made on maintaining the equilibrium between the supply of agricultural and fodder resources whilst ensuring food and ecological security. The overarching goal is to regulate the ecological restoration of our territorial space and utilization of degraded lands following the concept of Greater Food.

    • Effects of Vegetation Restoration Patterns on Soil Water-stable Aggregates Composition and Their Stability in the Water Level Fluctuation Zone of the Heilongtan Reservoir

      2024, 38(3):168-176. DOI: 10.13870/j.cnki.stbcxb.2024.03.039

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      Abstract:[Objective] This study aimed at elucidating the effects of different vegetation restoration modes on soil water-stable aggregates and stability in the water level fluctuation zone (WLFZ). [Methods] The characteristics of soil water-stable aggregates and their stability indexes were determined and analyzed by the wet sieve method on the soil under artificially and naturally restored vegetation in the WLFZ in the hilly region of central Sichuan Basin. [Results] The content of >0.25 mm water-stable macroaggregates in WLFZ soils was 4.21% lower compared to unflooded area. The soil water stability macroaggregates content decreased by 12.27% under naturally restored vegetation and increased by 3.84% under artificially restored vegetation compared to unflooded area; With the rise of water elevations, the soil water stability macroaggregates content showed an increasing trend, the microaggregates content showed an overall decreasing trend, and the soil aggregate stability gradually increased with the rise of water elevations; The soil water-stable aggregates composition differed significantly (p<0.05) among the different restoration modes, and the soil water-stable aggregates particle size increased overall under the artificially restored vegetation, in which the content of soil water-stable macroaggregates under the artificially restored vegetation (69.48%) was significantly higher than that of the natural restoration mode (43.20%); With increasing flooding time, there was a decrease in soil in soil water-stable aggregates stability in the WLFZ, the values of R0.25, MWD, and GMD in the artificial recovery mode were greater than those in the natural recovery mode. and the values of D, K, and PAD were smaller than those in the natural recovery mode. Soil water-stable aggregates stability and soil erosion resistance were higher in the artificial restoration model than in the natural restoration model. [Conclusion] The soil aggregate stability of WLFZ decreased after inundation, but the artificial restoration mode could effectively improve the soil aggregate structure, and the results of the study can provide a scientific basis for the evaluation of soil structure stability and vegetation restoration of the WLFZ.

    • Accuracy Assessment of Multi-source Land Use Products in the Loess Hilly and Gully Region

      2024, 38(3):177-186,194. DOI: 10.13870/j.cnki.stbcxb.2024.03.024

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      Abstract:[Objective] The study was aimed to assess the accuracy of multi-source land use products in the loess hilly and gully regions. [Method] Using the Guanchuan River Basin, a secondary tributary of the Yellow River, as a case study, this research evaluated the accuracy of six land use products with spatial resolutions of 10 and 30 m (WorldCover 10 m, ESRI 10 m, GLC_FCS30-2020, GlobleLand30, CNLUCC, and CLCD). The evaluation was based on high-precision GCLUCC land use data and focused on four aspects: spatial distribution, area characteristics, sample point accuracy, and spatial consistency. The GCLUCC data, with a spatial resolution of 1 m and an overall accuracy exceeding 95%, was derived from GF-2 (0.8 m), DEM (5 m), 6 400 field sampling points, and 2 320 Google Earth sample points, using an object-oriented approach and manual visual interpretation. [Results] (1) In terms of classification features, most products could extract major land categories, but significant differences in extraction efficiency and accuracy were evident, especially in the spatial distribution of arable land, forest land, and construction land. (2) Regarding area consistency, significant variations were found between each product and GCLUCC in terms of area of different land categories. For instance, the grassland area in some products was more than double that of GCLUCC, while forest and water areas were only 0.13%~12.11% and 1.41%~11.27% of GCLUCC, respectively. (3) In terms of overall accuracy, GlobleLand30 and WorldCover 10 m showed relatively higher accuracy, with spatial map accuracy reaching 58.21% and 50.19%, respectively. In contrast, CLCD and CNLUCC had relatively lower accuracy, with significant classification confusion between forest and grassland, arable and grassland, and construction and arable land. (4) Significant spatial discrepancies existed between all products and the actual ground cover, particularly in the classification of trees, shrubs, bare land, and water bodies. [Conclusion] Current land use products face challenges in accurately characterizing surface cover features in the loess hilly and gully regions. Future product development should consider topographical and geographical features more thoroughly and enhance the identification of specific land use types. These results can provide a theoretical reference for ecological conservation and land resource information acquisition in the Loess Plateau.

    • Estimation and Prediction of Water Conservation Capacity in Shaanxi Province Based on the InVEST-PLUS Model

      2024, 38(3):187-194. DOI: 10.13870/j.cnki.stbcxb.2024.03.005

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      Abstract:[Objective] This study was aimed to estimate the amount of water conservation in Shaanxi Province. [Methods] The InVEST model and PLUS model were coupled to calculate the water conservation amount in Shaanxi Province from 2000 to 2020 and predict the water conservation amount under land use changes in the future in 2030. [Results] The average water conservation amount in Shaanxi Province from 2000 to 2020 was 132.25 mm, with a spatial distribution characteristic of gradually increasing water conservation from north to south. From the perspective of vegetation types, forest land was the main body of water conservation in Shaanxi Province. The average annual water conservation amount was 199.55×108 m3. From the administrative region, Ankang City had the largest water conservation amount(308.96 mm). The total amount of water source conservation in 2030 will be 285.16×108 m3 and 8.68×108 m3 less than that in 2020. [Conclusion] The water conservation amount of Shaanxi Province will show a slight downward trend from 2020 to 2030 in the future.

    • Multi-scenario Prediction of Land Use Change and Carbon Storage in Shaanxi Province Based on the SD-PLUS Coupled Model

      2024, 38(3):195-206,215. DOI: 10.13870/j.cnki.stbcxb.2024.03.015

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      Abstract:[Objective] This study was aimed to explore the impact of different land use patterns on regional ecosystem carbon storage. [Methods] In this paper, using the SD-PLUS coupled model and the coupled shared socio-economic path and representative concentration path (SSP-RCP) scenario proposed by the Coupled Model Intercomparison Project Phase 6 (CMIP6), the land use changes in Shaanxi province in 2030 were projected, and then the different future scenarios simulated by the InVEST model were used to predict the Shaanxi Province’s carbon storage and its spatial distribution under different future scenarios simulated by the InVEST model. [Results] (1) The SD model constructed was tested historically, and its error was less than 5%, and the Kappa index of land use in 2020 simulated by the PLUS model was 0.86, and the accuracy and reliability of the model generally met the requirements. (2) Under the three scenarios, the area of future construction land increased, and the scenarios with the lowest to highest growth rates were: SSP126, SSP245, SSP585. Under all scenarios, the area of forest land increased, and the area of watersheds remained stable; the area of grassland had a small increase under the SSP126 scenario, and decreased in other scenarios; and the area of arable land decreased in all three scenarios. (3) Carbon stock in Shaanxi Province decreased under all three scenarios, with the decrease in carbon stock in the Guanzhong plain being the main reason for the decrease in carbon stock in Shaanxi province. [Conclusion] The area of ecological land occupied by the expansion of construction land is the smallest under the SSP126 scenario, which takes into account both socio-economic development and the need for ecological protection, and can provide a reference model for the future protection of land resources and high-quality development in Shaanxi province.

    • Basic Characteristics of Windbreak in the Black Soil Region of Northeast China and Its Relationship with Wind Direction

      2024, 38(3):207-215. DOI: 10.13870/j.cnki.stbcxb.2024.03.001

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      Abstract:[Objective] In order to explore the relationship between the windbreak direction and the prevailing wind erosion direction in the black soil region of Northeast China. [Methods] The basic characteristics of the windbreak in the study area were obtained by remote sensing interpretation and field survey, and the angle of intersection between the windbreak direction and the prevailing wind erosion direction, that is, the wind direction declination angle, was calculated and analyzed by combining the wind speed and wind direction data of 43 meteorological stations in the study area. [Results] The westerly wind in Mengdong black soil sub-region accounted for a large proportion, the wind direction was more concentrated, the prevailing wind erosion direction dominance was strong, the wind direction in the Songnen black soil sub-region was scattered, and the prevailing wind erosion direction dominance was weak. Average windbreak density Songnen black soil sub-area > Mengdong black soil sub-region; The windbreak direction accounted for the largest proportion in the Songnen black soil sub-area was the N-S trend windbreak direction, and there was no obvious regularity in the Mengdong black soil sub-region. In the study area, the proportion of wind declination angle <30° was 29.60%, and the proportion of wind angle >30° was 70.40%, and the wind protection effect was poor. [Conclusion] The direction of a large number of windbreak in the study area is oblique to the prevailing wind erosion direction, and the protective effect is poor. The results of this study have important reference value for understanding the density and trend of existing windbreak belts, and for further construction and transformation of windbreak.

    • Spatiotemporal Distribution of Ecosystem Services and Analysis of Cold and Hot Spots in Beijing-Tianjin Sandstorm Source Region

      2024, 38(3):216-226. DOI: 10.13870/j.cnki.stbcxb.2024.03.002

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      Abstract:[Objective] This study was aimed to assess the ecological benefits and ecological impacts after the implementation of the ecological project in the Beijing-Tianjin wind and sand source area. [Methods] Based on the remote sensing, meteorological, soil, and land use data of the Beijing-Tianjin wind and sand source area from 2000-2017, the CASA (Carnegie-Ames-Stanford approach) model, the InVEST ( Integrated valuation of ecosystem services and trade offs) model, RWEQ (Revised wind erosion equation) model, and RUSLE (Revised Universal Soil Loss Equation) model, the water yield, soil conservation, carbon sequestration and wind and sand services were estimated respectively. The Getis-Ord Gi* statistical index method was used to identify the ecosystem services hot and cold spots in the Beijing-Tianjin wind and sand source area. [Results] (1) Each ecosystem service function showed an increasing trend from 2000 to 2017, and the high value areas of the four ecosystem service functions were concentrated in the southeast of the study area, and the low value areas were concentrated in the northwest of the study area. (2) All four ecosystem services showed a significant hotspot area increase in the Ordos Plateau sandy land management area in the southwestern part of the Beijing-Tianjin wind and sand source from 2000 to 2017; The area of hotspot for carbon sequestration services increased significantly, of which the cold spots in the Hunshandak-Khorqin sand land control area and the hilly mountainous area of the Damshang Plateau in northern North China had transformed into hotspots. The hotspot area of water production service did not change significantly, and the hotspot area was mainly concentrated in the southern part of the study area in the Damshang Plateau and the hilly and mountainous water conservation management area in northern China, and the distribution of the hotspot area is more scattered. The cold spot area of windbreak and sand fixation service had increased in area; The area of the cold spot area of soil conservation service had a small percentage and not much change, and the regional capacity of soil conservation and supply was relatively average. (3) The results of multiple ecosystem services showed that the southeastern region of the study area is able to provide two or more high-value ecosystem service functions and belongs to the key ecosystem service function supply area, accounting for about 15.5% of the whole study area. (4) The four ecosystem service hotspot areas of forest land accounted for a relatively high percentage of the area from 2000 to 2017, and the hotspot areas of carbon sequestration service functions of grassland and forest land increased significantly, and forest land can provide a high level of integrated ecosystem service functions. [Conclusion] The implementation of the Beijing-Tianjin wind and sand source control project has improved the overall ecosystem service function in the region, and the results of the study can provide scientific data for assessing the effectiveness of the restoration of the Beijing-Tianjin wind and sand source control project, and ultimately realizing the sustainable development of the ecological environment in the Beijing-Tianjin region.

    • Supply-Demand Balance of Ecosystem Services in the Middle Reaches of the Yangtze River Based on Land Use Change

      2024, 38(3):227-238. DOI: 10.13870/j.cnki.stbcxb.2024.03.017

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      Abstract:[Objective] This study was aimed to reveal the spatio-temporal characteristics of supply-demand balance of ecosystem services, and further to explore the dual effects and influencing mechanisms of land use change on the supply-demand balance of ecosystem services. [Methods] Taking the middle reaches of the Yangtze River as the research area and seleting 2000— 2018 as the research period, the quantitative matrix of supply-demand of ecosystem services was employed to analyze the spatio-temporal characteristics of the supply-demand balance of ecosystem service, and the ecological contribution rate of land use change was introduced to analyze the influencing mechanisms of land use change on the supply-demand balance of ecosystem services. [Results] (1) During the study period, the supply-demand balance of ecosystem services in the middle reaches of the Yangtze River had been continuously deteriorating, which was mainly caused by the large-scale expansion of construction land and the large-scale reduction of cultivated land and forest land, resulting in the decrease of supply capacity and the increase of consumption demand of ecosystem services. (2) The relationship between different supply of ecosystem services had changed from trade-off to synergy in time scale, and the synergy between different demand and supply-demand balance of ecosystem services had been further enhanced on the time scale, but the trade-off or synergy between supply, demand, and supply-demand balance was highly heterogeneous on the spatial scale. (3) Land use change in the MRYR had dual effects on the supply-demand balance of ecosystem services, and the deterioration effect was significantly larger than the improvement effect, but the types of land use change that cause the improvement and deterioration of supply-demand of ecosystem services and their sub-services had temporal heterogeneity. [Conclusion] Promote types of land use change that could improve the supply-demand balance of ecosystem services; promote types of land use change that are compatible with key ecosystem services; and curb types of land use change that would worsen the supply-demand balance of ecosystem services, in order to increase the sustainability of ecosystem services and improve the quality of the ecological environment.

    • Spatial and Temporal Changes and Driving Mechanism of Cultivated Land Conversion in Central Yunnan Urban Agglomeration from 1990 to 2020

      2024, 38(3):239-251. DOI: 10.13870/j.cnki.stbcxb.2024.03.021

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      Abstract:[Objective] By analyzing the evolution path, spatiotemporal variation characteristics, and driving mechanisms of farmland non agriculturalization in the central Yunnan urban agglomeration over the past 30 years, theoretical basis is provided for the protection and precise management of farmland resources in the central Yunnan urban agglomeration. [Methods] Based on the land use data and statistical yearbook data of the Central Yunnan urban agglomeration, the paper used methods such as gravity displacement model, change trajectory model, spatial autocorrelation analysis, and principal component analysis to reveal the process and spatial distribution characteristics of farmland conversion to non-agricultural uses in the Central Yunnan urban agglomeration from 1990 to 2020, as well as the main driving factors. [Results] (1) From a temporal perspective, the non-agricultural area of cultivated land in the central Yunnan urban agglomeration showed a fluctuating downward trend, with an average annual increase of about 6.88× 103 around 2000 hectares converted to an average annual decrease of approximately 2.66× 104 hectares, with the most drastic changes due to policy, economic, and urbanization impacts. From a spatial perspective, the non-agricultural conversion of cultivated land was concentrated in the central, eastern, southeastern, and northeastern regions of the central Yunnan urban agglomeration. (2) Over the past 30 years, the non-agricultural transformation of cultivated land in the central Yunnan urban agglomeration has tended to be balanced in spatial distribution, with smaller regional differences in the non-agricultural transformation of cultivated land and a more stable spatial pattern. (3) The cultivated land in the central Yunnan urban agglomeration was mainly converted into forests and grasslands, with a small portion converted into construction land. Among the variable cultivated land, 54.60% was related to grasslands, 29.33% was related to forests, and 4.64% was related to construction land, mainly occurring in the central, northern, southeastern, and northwestern regions of the central Yunnan urban agglomeration. (4) There was a significant spatial clustering effect in the non-agricultural transformation of cultivated land in the central Yunnan urban agglomeration, mainly characterized by high-high clustering and low-low clustering. High-high clustering was mainly distributed in the central, northern, and southeastern regions, while low-low clustering was mainly distributed in the northwest, western, and southwestern regions.(5) The non agriculturalization of cultivated land in the central Yunnan urban agglomeration was influenced by both socio-economic and natural conditions. The agricultural population, state-owned fixed asset investment, and urbanization rate were the main factors for the non-agricultural expansion of cultivated land in the social economy, with influencing coefficients of -0.18, 0.11, and 0.10, respectively; The annual average precipitation and annual average temperature of natural factors played a crucial role in the spatial distribution and expansion process of non-agricultural land, with impact coefficients of 0.17 and -0.15, respectively. [Conclusion] The results have revealed the spatiotemporal change characteristics, evolution path, and driving mechanisms of farmland converted to non-agricultural land in the central Yunnan urban agglomeration over the past 30 years. It plays an important role in rational utilization and protection of arable land resources and ensuring food security in Yunnan province, and to a certain extent, it can provide a decision-making reference for the protection and optimization of arable land layout in the central Yunnan urban agglomeration.

    • Identification of Key Areas for Ecological Restoration and Division of Restoration Zones in Qinghai Province

      2024, 38(3):252-265. DOI: 10.13870/j.cnki.stbcxb.2024.03.032

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      Abstract:[Objective] Identifying priority spaces for ecological restoration and curbing ecological degradation based on the governance idea of "holistic protection, systematic restoration and comprehensive management" is an important measure for the coordinated development of regional socio-economics, the construction of a firm ecological security barrier, and the promotion of ecological civilization. [Methods] This paper took Qinghai Province as the study area, reflects the urbanization process through land use intensity and the land use center of gravity shift, quantitatively evaluates seven ecosystem services, ecological sensitivity, and habitat degradation from 2005 to 2020, and proposes to identify the priority space for ecological restoration based on the cluster of ecosystem services, ecological sensitivity, and habitat degradation. We proposed to identify ecological restoration priority spaces based on "ecosystem service cluster, ecological sensitivity and habitat degradation degree", and combined internal defects and external coercion to delineate five types of ecological restoration priority zones and propose corresponding restoration strategies. [Results] The depth of water production in Qinghai province from 2005 to 2020 were 125.1 mm, 106.9 mm, 80.0 mm and 135.4 mm respectively, and the depth of water retention was stabilized at about 15 mm. Grain output increased from 1.42 t/hm2 to 2.02 t/hm2, wind and sand control capacity increased from 2.42 t/hm2 to 4.59 t/hm2, and soil conservation capacity decreased from 85.90 t/hm2 to 65.30 t/hm2; The ecosystem service clusters in Qinghai province were classified into five categories: harmony of habitat, harmony of soil and water, conservation of ecological sources, restoration of natural ecology, and functional cluster of wind and sand conservation. Based on the results of bivariate autocorrelation to identify the ecological restoration priority points, it can be seen that the key ecological restoration points and natural ecological restoration points are the main ones in Qinghai province, accounting for 5.26% and 2.55% of the area, respectively, in which the key ecological restoration points and ecological livability clusters increase the area of the spatial distribution of the basic coincides with each other. [Conclusion] The priority areas for ecological restoration in Qinghai province are concentrated in the ecologically fragile northwestern desert areas, high-altitude mountainous areas, water sources and river coasts and the river valley where human activities are more frequent, and in the area around Tianjun county and Xinghai-Mado-Qumalai county.

    • Multi-scenario Simulation of Land Use and Carbon Storage Assessment in the Pearl River Basin in the Next Decade

      2024, 38(3):266-275. DOI: 10.13870/j.cnki.stbcxb.2024.03.026

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      Abstract:[Objective] The temporal and spatial changes of land use and carbon storage in the Pearl River Basin in the past 20 years and the next 10 years were analyzed in order to provide a reference for the optimization of land use pattern and ecosystem carbon sequestration management in the Pearl River Basin. [Methods] Based on the land use data of 2002, 2012, and 2022, this paper analyzed the changes of land use types, used the PLUS model to simulate the land use pattern under the natural development scenario, cultivated land protection scenario and ecological protection scenario in 2032, and used the InVEST model to evaluate the changes of ecosystem carbon storage under the three scenarios. [Results] The land types in the Pearl River Basin have changed greatly in the past 20 years, and the one-way conversion of cultivated land to construction land and the two-way conversion between cultivated land and forest land were the main characteristics of land use change in the Pearl River Basin. During the same period, the carbon storage of terrestrial ecosystems showed a downward trend as a whole, with a decrease of 0.52%. The carbon storage projection in 2032 shows that the carbon storage under the ecological protection scenario is significantly higher than that under the cultivated land protection scenario and the natural development scenario, which are 4.81×106 and 10.22×106 t higher, respectively. [Conclusion] Therefore, when formulating land use planning in the future, decision-makers should consider the balance between economic development and ecological protection, strengthen the concept of ecological protection and green development in river basins, increase the function of land carbon storage, and help achieve the "double carbon" goal and regional sustainable development.

    • Characteristics of Extreme Climate Change in the Qinling-Daba Mountains and Its Impact on Vegetation Dynamics

      2024, 38(3):276-287. DOI: 10.13870/j.cnki.stbcxb.2024.03.023

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      Abstract:[Objective] This study was aimed to understand the spatiotemporal changes in extreme climate and its influence on vegetation. [Methods] Based on daily meteorological data (1960—2020) from 115 weather stations in the Qinling-Daba mountains (QBMs) and surrounding areas and satellite-derived normalized difference vegetation index (NDVI), the spatiotemporal variation characteristics of the NDVI in the QBMs and its response to 19 extreme climate indices were analyzed. Geographic detector was used to identify the contribution rate of extreme climate indices and their influence on the NDVI. [Results] (1) The NDVI significantly increased in the majority of the QBMs (80.34%) and decreased in only a few regions (1.09%) from 2000 to 2020. The interannual change rate in the study area was approximately 0.03/10 a. (2) Noticeable warming was observed in the QBMs from 1960 to 2020, with the temperature increasing more at night than during the day, and regions with a larger change in extreme temperature events were mostly found in the Western Qinling Mountains (WQMs). During the study period, extreme precipitation events showed weak changes, extreme precipitation intensity increased in the southwestern QBMs, while in the eastern QBMs, extreme precipitation intensity decreased but extreme precipitation frequency increased. (3) Extreme precipitation events were the main factor affecting NDVI in the west Qinling region, while extreme temperature events were the main factor affecting NDVI in the Qinling and Daba mountain regions; the impact of extreme climate events on NDVI was not independent, and the interaction between extreme climate indices enhances the impact of a single factor on NDVI in a double-factor or nonlinear way. [Conclusion] The spatiotemporal changes in extreme climate and its influence on vegetation were clarified, which could establish scientific evidence for the protection and restoration of vegetation in the QBMs in response to global climate change.

    • Spatial and Temporal Variation Characteristics of Vegetation Greenness in Rocky Desertification and Non-rocky Desertification Areas of Chongqing

      2024, 38(3):288-297. DOI: 10.13870/j.cnki.stbcxb.2024.03.037

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      Abstract:[Objective] The investigation of temporal and spatial variations in vegetation greenness and its response to different land use types in karst rocky desertification and non-rocky desertification areas in Chongqing is crucial for guiding ecological restoration efforts in karst regions. [Methods] This study utilized vegetation leaf area index (LAI) data and land use type information to conduct a trend analysis and Hurst index calculations, aimed at analyzing the temporal and spatial evolution characteristics of vegetation greenness in both rocky desertification and non-rocky desertification areas. Additionally, a land use transfer matrix was employed to quantitatively assess the impact of land use changes on vegetation greenness. [Results] (1) Vegetation greenness exhibited an increasing trend in both rocky desertification and non-rocky desertification areas, reaching maximum values of 1.36 and 1.69 respectively, with average annual growth rates of 0.014 and 0.012. (2) The dynamic changes observed in vegetation greenness within these areas demonstrated positive trends, with improvement trends accounting for 86.84% (rocky desertification) and 87.04% (non-rocky desertification). Furthermore, anti-continuous improvement trends were observed at rates of 52 .82% (rocky desertification) and 80.29% (non-rocky desertification), indicating the primary change trajectory for future vegetation greenness. (3) The main land use types in both rocky and non-rocky desertification areas were woodland and cropland, and cropland converted from woodland was the main occurrence of degradation of vegetation greenness, while woodland converted from cropland, shrubs and grassland was the main occurrence of improvement of vegetation greenness. (4) The conversion of land use types with high leaf area index (LAI) to those with low LAI resulted in a decrease in LAI and vegetation greenness, while the conversion from low LAI land use types to high LAI land use types led to an increase in LAI. In areas affected by stony desertification and non-stony desertification, the maximum reduction in total LAI transfer was 11 902.04 and 4 442.18 respectively, whereas the maximum increase was 14 983.78 and 17 109.46 respectively. The impact on total LAI from construction land, water area, and bare land area was minimal and not significant. [Conclusion] These research findings contribute to understanding the change characteristics of vegetation greenness and its response mechanism towards land use changes in ecologically fragile areas. Furthermore, they provide a scientific basis for controlling rock desertification, ensuring ecological security, and promoting sustainable economic development in karst areas of Chongqing.

    • Soil Microbial Biomass and Ecological Stoichiometric Characteristics of Typical Land Use Types in Loess Hilly Region

      2024, 38(3):298-305. DOI: 10.13870/j.cnki.stbcxb.2024.03.003

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      Abstract:[Objective] This study was aimed to investigate the effects of the typical ecological management model of "upward retreat and downward push" on soil-microbial C, N and P and their ecological stoichiometric ratios in loess hilly areas. [Methods] Typical land use types (artificial forest land, terrace, and Chuanland) in the loess hilly area of Ningxia were selected to study the response of soil-microbial C, N and P contents to land use changes and to analyze the ecological stoichiometric ratios, microbial entropy (qMBC, qMBN, and qMBP), and stoichiometric imbalances (C∶Nimb, C∶Pimb, and N∶Pimb) among the Relationship. [Results] (1) Under the three typical land use types, SOC, C∶P, and N∶P in artificial forest land were higher than those in terraced and Chuanland, while TP content in agricultural land (terraced and Chuanland) was higher than that in artificial forest land. (2) The contents of soil microbial biomass C, N, and P ranged from 51.56 to 133.19, 7.97 to 21.98, and 4.63 to 12.81 mg/kg, respectively. Among them, soil microbial biomass C, N, and P were in the order of artificial forest land > terrace land > Chuanland. The ratio of microbial biomass C, N, P, C∶Nimb, C∶Pimb, and N∶Pimb had certain characteristics of internal stability and had no significant difference among different land use types. (3) The three typical land use types had significant effects on microbial entropy, with the qMBC ranking as terraced land > artificial forest land > Chuanland, while the qMBN and qMBP ranking as artificial forest land > terrace land > Chuanland. Combined with RDA analysis, it was concluded that microbial biomass C∶P (R2=0.75, p<0.01) and C∶Pimb (R2=0.74, p<0.01) were the key factors affecting the change of qMB. [Conclusion] In summary, the typical ecological management mode of "upward retreat and downward push" caused significant changes in soil C, P and microbial C, N and P contents, and the soil-microbial C, N and P and their stoichiometric ratios were mainly influenced by phosphorus under the typical land-use types.

    • Effects of Grazing Intensity on Soil Microbial Community Characteristics in Desert Steppe

      2024, 38(3):306-313. DOI: 10.13870/j.cnki.stbcxb.2024.03.009

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      Abstract:[Objective] Investigating the response mechanism of soil microbial communities to changes in grazing intensity can provide scientific theoretical and technical support for ecological protection and restoration of desert steppe. [Methods] Taking the desert steppe in Inner Mongolia as the research object, we studied the effects of different grazing intensities (no grazing, light grazing, medium grazing, and high grazing) on soil physicochemical properties and the composition and diversity of soil microbial communities at different soil depths (0—20 cm and 20—40 cm), the interactions between soil physicochemical properties and soil microbial communities were analyzed. [Results] Compared to no grazing, medium grazing significantly (p<0.05) reduced the soil total nitrogen (TN) content (by 17.99%) and soil organic carbon (TOC) content (by 19.23%) at 0—20 cm depth. The maximum value of soil bulk density (SBD) appeared under high grazing conditions. The soil physicochemical properties at 20—40 cm depth showed no differences (p>0.05) under different grazing intensities. In addition, grazing decreased the abundance and diversity of bacterial communities at 20—40 cm depth, while increased the abundance and diversity of bacteria communities at 20—40 cm depth. Under light and moderate grazing conditions, the abundance and diversity of soil fungal communities at 0—20 cm depth increased, with no significant effect (p>0.05) on the abundance and diversity of soil fungal communities at 20—40 cm depth. [Conclusion] Mantel tests showed that total nitrogen of desert steppe soil was the primary factor influencing the change of desert steppe soil bacterial abundance with grazing intensity. The research results contribute to understanding the ecological sensitivity of soil microbes and offer scientific guidance for achieving sustainable management in desert steppe ecosystems.

    • Optimization of Water and Nitrogen Regime Based on AquaCrop Model for Drip Irrigation Cotton Under Nitrogen Reduction Conditions in Northern Xinjiang

      2024, 38(3):314-324,334. DOI: 10.13870/j.cnki.stbcxb.2024.03.018

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      Abstract:[Objective] This study was aimed to test the applicability of the AquaCrop model for simulating the growth and production of drip-irrigated cotton under nitrogen-reducing conditions in the northern border, and to investigate the optimal nitrogen-reducing and irrigation regimes during the reproductive period of cotton. [Methods] Through the field trials in 2022 and 2023, we clarified the effects of four nitrogen application levels (conventional nitrogen application, nitrogen reduction of 10%, nitrogen reduction of 20%, and nitrogen reduction of 30%), and three irrigation schedules (488, 444, and 400 mm) on cotton yield, water and nitrogen use efficiency, and soil nutrient content; we used measured data from the treatments to determine and validate the parameters of the model, and then simulated the model with the calibrated model. Cotton yield and water and nitrogen use efficiencies were simulated with the calibrated model under six combinations of nitrogen application levels (conventional nitrogen application, nitrogen reduction of 6%, nitrogen reduction of 12%, nitrogen reduction of 18%, nitrogen reduction of 24%, and nitrogen reduction of 30%), and six combinations of irrigation levels (300, 360, 420, 480, 540, and 600 mm), and the optimal water and nitrogen combinations were screened out by the comprehensive evaluation method. [Results] Nitrogen reduction and irrigation quota together had a significant effect on cotton yield, water and nitrogen use efficiency and soil nutrients. Nitrogen fertilizer reduction can be achieved by appropriately increasing the irrigation quota to stabilize cotton yield; Under the same nitrogen application, appropriately reducing the irrigation quota improved water use efficiency; Under the same irrigation quota, appropriately reducing the nitrogen application improved nitrogen fertilizer bias productivity; A 10% increase in the conventional irrigation quota (W1N1) when applying conventional nitrogen effectively improved the nutrient content of the tillage layer of the soil. The simulation and measurement results showed that each evaluation index of canopy cover and above-ground biomass of the 2-years experimental treatments satisfied the coefficient of determination (R2)≥ 0.936, the root mean square error (NRMSE) ≤ 40.58%, and the Nash coefficient (ENS)≥ 0.72; And each evaluation index of yield and water-use efficiency satisfied the coefficient of determination R2≥0.87, NRMSE ≤ 4.29%, and ENS≥0.81; The model achieved a better simulation effect. [Conclusion] Based on the scenario simulation under 36 combinations of nitrogen reduction and irrigation, and considering the yield, water and nitrogen utilization efficiency and the actual production cost, the nitrogen reduction irrigation system with 12% nitrogen reduction and 360 mm irrigation quota is recommended to be adopted in the northern border region. The study can provide experience for the application of the AquaCrop model under different fertilizer and irrigation regimes in the future and provide a theoretical basis and scientific guidance for the improvement of water and nitrogen fertilizer use efficiency during cotton cultivation in arid regions.

    • Spatial and Temporal Variation and Potential of NPP in Terrestrial Ecosystems in Shaanxi Province from 2000 to 2020

      2024, 38(3):325-334. DOI: 10.13870/j.cnki.stbcxb.2024.03.010

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      Abstract:[Objective] In the context of the "dual-carbon" goal, accurately assessing the status, rate and potential of carbon sequestration in terrestrial ecosystems is crucial for achieving "carbon neutrality". Shaanxi Province, which spans three climatic zones and have a large difference in climate between north and south, with abundant vegetation types. In recent years, the vegetation coverage in Shaanxi has been further improved due to the implementation of various ecological projects (Grain for Green, Three-North Shelterbelt, etc.). Its vegetation coverage reaches up to 60.7%, what resulted in huge carbon sequestration capacity. Net primary productivity (NPP), as one of the most important indicators to reflect the carbon sequestration capacity of vegetation, there are few studies on spatial and temporal dynamic changes of NPP and the spatial distribution of NPP potential in the future in Shaanxi province. [Methods] Based on these, we evaluated the temporal and spatial distribution characteristics of vegetation NPP and its potential in Shaanxi province through the CASA model and the neighborhood similarity spatial distribution method. [Results] (1) Total carbon sequestration by vegetation increased by 333 Tg, with an increase of 48.5% from 2000 to 2020 in Shaanxi province. (2) NPP was higher in the south and lower in the north, with the highest or lowest value in the middle. The average value in 2000 and 2020 were 333.2 g C/m2 and 494.8 g C/m2, respectively, with a total increasement of 161.6 g C/m2, and the increase amplitude showed a distribution trend of high in the north and low in the south in Shaanxi. (3) The carbon sequestration potential was 2 304 Tg which increased by 41.30% compared with the 2020. The spatial distribution trend was gradually decreasing from south to north, and the spatial distribution characteristics showed high spatial autocorrelation characteristics, but the local differences were large. [Conclusion] The total vegetation carbon sequestration in Shaanxi province increased significantly from 2000 to 2020, and there is huge potential for vegetation carbon sequestration in the future. This study calculated the spatial and temporal dynamic changes and predicted potential spatial distribution characteristics of NPP in the regional scale ecosystem in Shaanxi province, which can provide an evaluation systematic and theoretical reference for scientific evaluation and improvement of regional carbon sink capacity.

    • Response of Vegetation NPP to Multiscale Meteorological Drought in Southwest China

      2024, 38(3):335-344. DOI: 10.13870/j.cnki.stbcxb.2024.03.016

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      Abstract:[Objective] This study was aimed to explore the response mechanism of vegetation to drought at different times scales and clarify the frequent occurrence of extreme drought events in southwest China on vegetation growth. [Methods] Based on vegetation net primary productivity (NPP) data from 2001 to 2019 and standardized precipitation evapotranspiration index (SPEI) data on a continuous scale from 1-24 months in southwest China, correlation analysis, maximum synthesis method, significance test were used to analyze the responses of NPP of different geomorphic types and vegetation types to multi-scale SPEI in southwest China. [Results] (1) On the annual scale, seasonal scale and growing season, the responses of vegetation NPP and SPEI at 1-24 months were dominated by the January-March scale, vegetation NPP had a good response to short-term drought changes, but a relatively poor response to medium and long-term drought changes. (2) The response of NPP to SPEI at 1-24 month scale showed significant spatial heterogeneity and seasonal differences. The interannual correlation showed a trend of significant positive correlation to significant negative correlation from southeast to northwest. The seasonal correlation showed that significant negative correlation was dominant in summer, significant positive correlation was dominant in spring, autumn, and winter. This indicated that in the southwest China, the summer temperature was high and humid, which limited vegetation growth the area with the largest positive correlation was Guangxi Hills, while the area with the largest negative correlation was Zoige Plateau. (3) The responses of NPP to SPEI from 1-24 months were different among different vegetation types. Although the response characteristics of grassland, scrub and forest land to SPEI were basically similar, the trend of negative correlation between NPP and SPEI became stronger with the scales of SPEI decreased in summer for all types of vegetation. This suggested that all types of vegetation are more susceptible to drought under high temperature and drought conditions in summer. [Conclusion] The research results provide effective scientific support for the protection and restoration of the ecosystem in the southwest China, provide an important theoretical basis for disaster prevention and reduction and coping with climate change, help formulate more targeted policies and measures to promote the sustainable development of southwest China.

    • Effects of Aeration on Tomato Growth and Soil Enzyme Activity Under the Conditions of Topdressing Fertilizer Reduction

      2024, 38(3):345-355,368. DOI: 10.13870/j.cnki.stbcxb.2024.03.019

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      Abstract:[Objective] The study aimed to explore the effects of aeration on crop growth characteristics and soil environmental characteristics in the root zone under reduced topdressing conditions. [Methods] The present paper took the field cultivated tomato in Yinbei irrigation area of Ningxia as the research object. Four groups of micro-nano gas aeration ratios (0, 5%, 10%, and 15%) and three topdressing fertilizer (urea-triple superphosphate-potassium sulfate) levels (180-400-480 kg/hm2, 135-300-360 kg/hm2, and 90-200-240 kg/hm2) were set up for the two-year field experiment conducted in 2019 and 2020. [Results] With the same topdressing level, the dry matter and nutritional elements (N, P, and K) accumulation in the plant increased with the increase of aeration ratio, and increasing the aeration ratio was beneficial to the accumulation of phosphorus in roots during flowering-fruit setting period and the potassium accumulation at fruit expansion stage. With the same topdressing level, the tomato yield increased by 14.0%~44.2% as the aeration ratio increased by 5%~15%. With the same aeration ratio, the tomato yield increased by 0.4%~9.1% as the topdressing level was appropriately reduced (-25%) compared with the traditional fertilization. The increase of the aeration ratio and topdressing level was beneficial to increase the soil enzymes (catalase, alkaline phosphatase, and urease) activity significantly during the flowering-fruit setting period and fruit enlargement period of tomato. With the same topdressing level, increasing the aeration ratio by 5%~15% corresponded to an increase in soil enzyme activity by 27.5%~122.9%. [Conclusion] It was suggested that, to promote tomato plant growth, stabilize tomato yield and improve the soil enzymes activity in the Yinbei irrigation district, the suitable topdressing level of "urea-triple superphosphate-potassium" was 135-300-360 kg/hm2 (25% lower than the traditional topdressing amount), and the suitable micro-nano aeration ratio was 10%.

    • Nitrogen and Phosphorus Transformation of Soil and Growth of Maize in Black Soil Area by Different Tillage Patterns and Biochar Addition

      2024, 38(3):356-368. DOI: 10.13870/j.cnki.stbcxb.2024.03.027

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      Abstract:[Objective] This study aimed to investigate the effects of different tillage patterns and biochar addition on soil nitrogen and phosphorus transformation and maize growth and development in farmland in the black soil area. [Methods] Through a field experiment, two tillage treatments (deep tillage and shallow tillage) and five biochar addition treatments (0, 3, 6, 9, and 12 t/hm2) were set up to investigate the combined effects of different tillage patterns and biochar addition on soil nitrogen and phosphorus fractions, enzyme activities, and physiological characteristics of maize. [Results] (1) Deep tillage and shallow tillage in combination with biochar addition could effectively improve soil structure, increase the geometric mean diameter of agglomerates, and reduce the percentage of damage. The deep tillage treatment was more effective than the shallow tillage treatment. (2) The addition of biochar improved soil nitrogen-phosphorus fractions, urease activity, and alkaline phosphatase activity, and the effect of applying biochar at the rate of 9 t/hm2 was the best, which was more pronounced in the deep tillage treatment. (3) The application of biochar up to 9 t/hm2 under deep tillage treatment increased the total nitrogen and phosphorus contents and glutamine synthetase activity of leaves and decreased the acid phosphatase activity. (4) The yield of corn under deep tillage condition with the addition of 9 t/hm2 of biochar was as high as 17.37 t/hm2, which was increased by 28.9% compared with that of 0 of biochar. [Conclusion] The deep-tillage treatment and addition of 9 t/hm2 biochar provided a reference for the nutrient environment and crop growth in agricultural fields in the black soil area.

    • Effects of Organic Manure and Other Nitrogen Substitutes on Spring Maize Growth, Yield, and Water and Fertilizer Utilization Efficiency

      2024, 38(3):369-381. DOI: 10.13870/j.cnki.stbcxb.2024.03.022

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      Abstract:[Objective] This study was aimed to investigate the effects of organic manure replacing chemical fertilizer with equal nitrogen under different nitrogen application rates on the growth, yield and water-fertilizer use efficiency of spring maize in the dry zone of northern Shaanxi. [Methods] Multiple regression analysis and three-dimensional fitting models were used to establishing an optimal nitrogen management model for spring maize cultivation in northern Shaanxi. In this experiment, three nitrogen application levels (240, 180, 120 kg/hm2 for N1, N2, N3, respectively) and five organic manure replacing chemical fertilizer with equal nitrogen ratios (R0, R12.5, R25, R37.5, R50 for 100% chemical fertilizer nitrogen, 12.5% organic fertilizer nitrogen+87.5% chemical fertilizer nitrogen, 25% organic fertilizer nitrogen+75% chemical fertilizer nitrogen, 37.5% organic fertilizer nitrogen+62.5% chemical fertilizer nitrogen, 50% organic fertilizer nitrogen+50% chemical fertilizer nitrogen, respectively ), a total of 15 treatments. During the main reproductive period of spring maize, spring maize growth and yield and yield components were measured, and water consumption (ET), water use efficiency (WUE), nitrogen fertilizer partial productivity (NPFP) and economic benefits were calculated. [Results] The Logistic function had a high fit for dry matter accumulation in spring maize, the R12.5 treatment delayed the start, the end and the appearance of the maximum value of the period of rapid dry matter accumulation, and the N2 treatment enhanced the maximum daily growth rate of dry matter accumulation. Nitrogen application and replacement ratio significantly affected dry matter accumulation, yield and components, ET, NPFP and economic efficiency of spring maize (p<0.05), and the interaction significantly affected ear length, ear coarse, and ET (p<0.05). The average dry matter accumulation, yield, ET, and net income of N2 treatment were higher than those of the N1 and N3 treatment 5.58% and 15.80%, 4.25% and 16.76%, 4.96% and 3.41%, 8.76% and 29.42%, respectively. R12.5%~R37.5% treatment significantly enhanced dry matter accumulation, yield and components, ET, WUE, NPFP, net income and input/output. WUE continued to increase with increasing N application, while NPFP continued to decrease. Treatment N2R25 had the highest dry matter accumulation and ET, and treatment N2R37.5 had the highest yield, net income, and input/output. Spring maize yield was significantly and positively correlated with dry matter accumulation, ET, WUE, net income and input/output. [Conclusion] The comprehensive analysis obtained showed that dry matter accumulation, yield, WUE, NPFP, and net income of spring maize could be optimized simultaneously at the N application and replacement ratio intervals of 190~210 kg/hm2 and 17%~29%, respectively.

    • Spatial Variation Characteristics and Influencing Factors of Black Soil Quality in Typical Water-Eroded Sloping Cropland

      2024, 38(3):382-390,399. DOI: 10.13870/j.cnki.stbcxb.2024.03.029

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      Abstract:[Objective] This study aimed to clarity the role of sedimentation and erosion in shaping the spatial pattern of soil quality in black soil slope croplands. [Methods] Taking the sloping farmland in typical water-eroded areas in northeast China as the research object, we used the soil attributes of 110 sample points and the soil quality index (SQI) index based on the minimum data set to evaluate the spatial differentiation characteristics of soil quality at the slope scale, while the effects of slope gradient, slope position, and soil depth were determined using generalized linear models (GLMs). [Results] (1) Opposing patterns of soil nutrient content and spatial characteristics were observed between the surface and subsurface layers in sloping croplands. Most nutrient indicators exhibited significantly higher content in the tillage layer compared to the subsurface layer. However, the surface layer showed lower spatial heterogeneity and weaker correlation with related physicochemical indexes comparing with the subsurface layer (p<0.05). (2) Erosion and sedimentation significantly influenced the spatial distribution characteristics of soil quality. The SQI was significantly lower in slopes with severe erosion compared to up-slope areas with weakly eroded regions and down-slope areas in depositional areas (p<0.05). [WT]Compared with the upper position, the SQI of middle position was 26.2% and 31.6% lower at surface and subsurface soil layers, respectively. Sedimentation did not improve the soil quality of severely eroded slope croplands, and there were no significant differences in SQI between down-slope and up-slope areas (p>0.05). (3) Soil depth, slope position, and slope gradient emerged as key factors influencing the variability of SQI in slope croplands. The GLM results demonstrated that, for the same soil horizon, slope, aspect, and their interactions explained over 95% variation in SQI. Among them, the explanatory degree of slope position was 68%, and that of slope gradient was 22%. Considering the factor of soil depth, the explanatory degrees of soil depth, slope position, and slope gradient on the variation of SQI in the range of 0—40 cm were 39%, 31%, and 10%, respectively. [Conclusion] The combined method of SQI and GLM was used to clarify the shaping role of the erosion-sedimentation process in the spatial differentiation of black soil quality in sloping cropland, and the research results can provide technical support for the evaluation and management of the quality of eroded and degraded black soil in typical water-eroded areas.

    • Transformation of Chemical Forms and Migration Characteristics of Cadmium and Selenium During Soil Formation in Black Rock Series

      2024, 38(3):391-399. DOI: 10.13870/j.cnki.stbcxb.2024.03.036

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      Abstract:[Objective] Black rock series contain high amounts of cadmium (Cd) and selenium (Se). During weathering and soil formation on the rocks, the chemical form transformation and release of Cd and Se from the rocks can have an impact on the surrounding ecological environment. [Methods] In this study, a black rock series distribution area of Hetang formation of the Lower Cambrian was selected in northwest Zhejiang. By collecting horizonal soil samples from soil profiles along different parts of the terrain (hill upslope, hill middle slope, hill downslope, inter hill valley bottom and valley terrace), the quantity and chemical form transformation patterns of Cd and Se during the process of weathering soil formation and weathering material migration of the black rock series were discussed. [Results] The results showed that total Cd and total Se in the soil decreased from parent rock to soil. The loss of Cd and Se in the weathered matter of black rock series increased with the increasing of transportation distance along the hilly slope, and the loss of Cd and Se in the process of evolution from slope deposit to diluvium was greater than that from residual to slope deposit. The Cd and Se lost from the weathered materials could affect the contents of Cd and Se in the topsoil derived from the alluvial of the downstream river in the way of water diffusion, but the degree of influence decreased with the increasing of distance. With the increasing of the transportation distance of weathered materials and the evolution of soil, the transformation of carbonate bound Cd and residual Cd to water-soluble Cd, exchangeable Cd, organic matter bound Cd and oxide bound Cd occurred. The residual Se gradually activated and transformed into exchangeable Se, organic matter bound Se and oxide bound Se. The results also showed that soil water-soluble Cd, exchangeable Cd (Se) and organic matter bound Cd (Se) showed an increasing trend toward the surface. The organic enrichment and topsoil enrichment of Se were more obvious than those of Cd. [Conclusion] The results indicated that the weathering of black rock series could not only directly affect the contents of soil Cd and Se in their distribution area through residue, but also affect the contents of soil Cd and Se in the surrounding areas through water diffusion.