• Volume 38,Issue 2,2024 Table of Contents
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    • Response and Mechanism of Source-Sink-Flow Caused by the Compensation Effect of Crop Rehydration After Drought

      2024, 38(2):1-12,338. DOI: 10.13870/j.cnki.stbcxb.2024.02.002

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      Abstract:[Objective] Crops often suffer from interval drought and rehydration (rainfall or irrigation) during the whole growth period, especially in arid and semi-arid areas. Under drought stress, the growth and development of crops are inhibited, and the yield is reduced; meanwhile, the plants drought tolerance will be induced. In order to compensate loss of yield or growth induced by drought stress, crop often shows compensatory after rehydration, which produces compensation or even over compensation effect on yield. The compensation effect of post drought is the result of crop’s positive response to drought stress and compensatory growth after rehydration. It can effectively improve crop yield and water use efficiency in crop production in arid areas. [Methods] Source sink relationship is widely used to explain the crop yield formation, and regulating the source sink relationship is one of key way to improve crop yield. The compensation effect of post drought is highly related to the source sink response of crops. Based on the current research progress, this paper tries to explain the compensation effect of post drought in source and sink way. [Results] Under the drought stress, in the source, the stomata were closed, photosynthesis was decreased and soluble carbohydrate accumulation was increased, while sink activity was often increased. After rehydration, the metabolism of soluble carbohydrate in the source (leaf) was enhanced, which enhanced the photosynthesis and the ability of carbohydrate synthesis; meanwhile, the sink activity (grain) was maintained at a high level, and the rate of assimilate unloading and accumulation was accelerated; the assimilate in the flow remained at a high level. During this process, the activities of sucrose invertase (INV), cell wall invertase (CW-INV) and fructan exohydrolases (1-FEH w3) play important roles in the source sink response to the compensation effect of post-drought. [Conclusion] This paper integrated the mechanism of compensation effect of post drought in the perspective of source sink relationship, which provides a theoretical basis for understanding the mechanism of compensation effect of post drought and improving crop water efficient in arid areas.

    • Research Progress and Prospect of Mechanical Effects and Model Construction of Root-soil Complex

      2024, 38(2):13-28,196. DOI: 10.13870/j.cnki.stbcxb.2024.02.017

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      Abstract:[Objective] In order to investigate the mechanism of mechanical effect of root-soil complex and the application of modeling method. [Methods] The concept and connotation of root-soil complex, the principle of mechanical effect and mechanical model of root-soil complex, advantages and disadvantages as well as the scope of application were summarized and analyzed by using literature analysis method and comparative analysis method. [Results] (1) The root-soil complex was a composite whole of mechanical coupling effect between root system and soil body, and the root system was intertwined in soil playing a reinforced role. (2) The mechanical relationship between root system and soil body was essentially the result of soil mechanical, hydraulic and composite mechanical properties of root-soil complex. The soil mechanical and hydraulic properties focused on the influence of roots on the soil and the influence of water on the soil and root system respectively, and the composite mechanical properties focused on the direct influence of soil properties on the properties and structure of plant roots, so that the mechanical relationship between roots and soil was in a dynamic balance through the three. (3) The study of the composite mechanical model of the root-soil complex was slightly less than that of the soil mechanical and hydraulic model, which were based on quantitative parameters and measure the soil consolidation effect by comparing parameters. However, the composite mechanical properties involves both soil and hydraulic properties, which was a comprehensive consideration and should be the key research direction in the future. [Conclusion] In-depth research was needed in the future to investigate the effects of freeze-thaw cycle, dry-wet alternation and dry-hot cycle on root and soil interaction in different regions, the shear strength of multi-type plant mixtures, the influence mechanism of chemical and microbial effects on soil-water propertiess and the construction of composite models need to be further studied. This study can provide important theoretical value and engineering reference for vegetation restoration, soil and water conservation and sustainable development in ecologically fragile areas.

    • Laboratory Simulation on Process of Soil and Water Leakage from Fissures in Karst Peak-cluster Depression

      2024, 38(2):29-37,46. DOI: 10.13870/j.cnki.stbcxb.2024.02.005

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      Abstract:[Objective] Soil and water loss control is the key to the prevention and control of rocky desertification in karst areas, so the mechanism of soil and water loss and its influencing factors are explored. [Methods] The effects of water pressure (0.3, 1.3, 2.3, and 5.5 m water head height), karst fissure width (0.25, 0.5, 0.75, and 1.0 cm), and soil aggregate size (0~1.0, 1.0~2.0, 2.0~5.0, and 0~5.0 mm) on the process of soil and water leakage in the karst peak-cluster depression were studied through laboratory simulation experiment. [Results] The greater the water pressure and the fissure width were, the smaller the soil aggregate size was, or the absence of certain soil particle groups, the more easily the overlying soil layer was broken down taking approximately 2 to 20 minutes. After the soil layer was broken down, the water leakage rate surged rapidly before stabilizing, while the soil leakage rate peaked and then settled. The rates and cumulative amounts of soil and water leakage from the disrupted soil layer were significantly greater than that of the unbroken one. The cumulative amounts of water and soil leakage increased with the increased water pressure or fissure width. When fissure width was 0.25, 0.50, 0.75, and 1.00 cm, the cumulative amount of water leakage at 1.3 to 5.5 m water pressures was 1.2 to 13.2, 2.4 to 131.0, 2.1 to 167.3, and 75.8 to 141.9 times greater than that at 0.3 m one, respectively. The cumulative soil leakage diminished notably with larger soil aggregate sizes. The absence of larger aggregates led to the decrease of soil leakage with the increase of fissure width but the opposite was true for soils lacking smaller aggregates. When fissure width was 0.25, 0.50, 0.75, and 1.00 cm, the cumulative amounts of soil leakage from 1.0 to 2.0 and 2.0 to 5.0 mm aggregate particle groups were decreased by 98.4% and 99.1%, 46.3% and 83.7%, 43.2% and 74.0% as well as 41.1% and 27.1%, respectively, compared with that of 0 to 1.0 mm one. [Conclusion] The stability of the overlying soil layer plays a pivotal role on the process of soil and water loss in peak-cluster depression, and hydraulic conditions, soil properties, and the degree of karst fissure development critically influence this stability.

    • Surface Particle Size Characteristics of Dry Lake Beds in Grasslands and Their Effects on Dust Release

      2024, 38(2):38-46. DOI: 10.13870/j.cnki.stbcxb.2024.02.022

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      Abstract:[Objective] In order to explore the typical surface wind erosion process of the dry lake basin and the mechanism of the formation of saline-alkali dust storm. [Methods] Taking the Chagannaoer dry salt lake in Abaga Banner of Xilin Gol League as the research object, four different surface types (crust surface, broken surface, activated surface and desertification surface) were selected according to the dynamic evolution process of salt lake surface from the lake center to the lake shore. The characteristics of soil particle size distribution, wind speed profile and sediment transport law near the surface from the lake center to the lake shore were analyzed. [Results] (1) Extending from the center of the lake to the shore of the lake, the grain size of 0—2 cm sediment on the surface showed a trend of gradually thickening, and the clay and silt were the main particles. (2) The wind speed from the center of the dry salt lake to the shore of the lake showed a decreasing trend. Wind speed profiles of different surfaces generally followed the logarithmic distribution of Karman’s velocity, and the fitting effect was good (R2>0.90). (3) The amount of sediment transport on the broken surface was the highest, which was about 50 times that of the crust surface, and the sediment transport rate on the crust surface showed a linear law with the change of height due to limited dust supply (R2=0.80), and the sediment transport rate on the other three surfaces showed an exponential function with the change of height (R2>0.97). (4) Near the surface at a height of 0 to 50 cm, the average particle size of sand particles carried in the wind-sand flow ranges from 2 to 8 μm, which falled under the category of silt, with poor sorting. Skewness was predominantly negative, while kurtosis was mainly medium and sharp. [Conclusion] On the whole, the wind erosion effect on the broken surface was the strongest, and the wind erosion effect on the crust surface was the weakest. The wind erosion effect in this area can be weakened by increasing the critical starting wind speed threshold of sand particles and the coverage of underlying surface.

    • Effects of Erosive Rainfall on Soil Erosion Characteristics of Black Sloping Farmland

      2024, 38(2):47-56. DOI: 10.13870/j.cnki.stbcxb.2024.02.019

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      Abstract:[Objective] Rainfall is the driving force of hydraulic erosion in black soil sloping farmland. It is of great significance to study soil erosion characteristics under natural rainfall conditions for soil erosion control. [Methods] Based on 43 erosive rainfall events observed at different ridge-row runoff plots (3°, 5° and 7°) along the slope in Guangrong Small Watershed, Hailun City, Heilongjiang Province during 2021—2022, K-Mean clustering method was used to compare the characteristics of runoff and sediment transport under different rain patterns and slopes, and the influencing factors on runoff and sediment transport were discussed. [Results] The rainfall of short duration, heavy rain and light rainfall (rain type 3) is the main one, followed by the rainfall of medium duration, medium rain intensity and medium rainfall (rain type 2), and the rainfall of long duration, light rain intensity and heavy rainfall (rain type 1) rarely occurs. Under the same rain pattern, the cumulative runoff depth and sediment transport increased with the increase of slope. Under the same slope, different rainfall types have different responses to cumulative runoff depth. Overall, rainfall type 3 has the highest contribution (50.90%~57.90%), rainfall type 2 has the second contribution (37.60%~44.10%), and rainfall type 1 has the lowest. In the event of rain type 2, rainfall erosivity and slope have direct influence on runoff depth, and runoff depth and slope have direct influence on sediment transport. In the event of rain type 3, rainfall erosivity affects runoff depth and then sediment transport through direct and indirect effects. [Conclusion] For all rainfall-type events, rainfall erosivity and slope are the main controlling factors affecting the runoff depth, and the runoff depth and slope are the main controlling factors affecting the sediment transport.

    • An Experimental Study on Effects of Rainfall, Inflow and Slope Gradient on Ephemeral Gully Slope Erosion in Chinese Mollisol Region

      2024, 38(2):57-67,75. DOI: 10.13870/j.cnki.stbcxb.2024.02.004

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      Abstract:[Objective] In order to investigate the effects of rainfall intensity, inflow rate and slope gradient on hillslope ephemeral gully erosion and implement precise soil and water conservation measures. [Methods] This research established two rainfall intensities (50 and 100 mm/h) and two slope gradients (3° and 7°), and five inflow rates under four combinations of two rainfall intensities and two slope gradients to assess the influences of rainfall intensity, inflow rate, slope gradient and their interaction on slope soil erosion with ephemeral gully, and to quantify the contribution of ephemeral gully erosion to slope erosion. [Results] (1) The impact of slope gradient and inflow rate on slope soil erosion was greater than that of rainfall intensity. Under the five inflow rates, when the rainfall intensity increased from 50 mm/h to 100 mm/h, the slope erosion on the slopes of 3° and 7° increased by 52.3%~81.8% and 29.4%~88.4%, respectively; when the slope gradient increased from 3° to 7°, the slope erosion increased by 114.3%~395.5% and 130.0%~320.9%, respectively; when the inflow rate increased from 15 L/min to 75 L/min, the slope erosion increased by 4.6~13.5 times. The increase of inflow rate aggravated slope gradient influence on slope erosion while weakened rainfall intensity impacts on slope erosion. (2) The combined effects of rainfall intensity, inflow rate, and slope gradient, and inflow rate-slope gradient interactions on slope erosion were the larger impact, followed by the rainfall intensity-inflow rate interaction, and the interplay between rainfall intensity and slope gradient had the lowest impact. Ephemeral gully erosion accounted for over 85% of total slope erosion under various experimental conditions, which increased with inflow rate and slope gradient. (4) The slope erosion rates a positive correlation existed with the flow velocity, shear stress and stream power. Conversely, a negative correlation was observed with the friction coefficient. Among the parameters, the correlation between slope erosion rate and stream power was best. [Conclusion] The research results provide a scientific basis for the development of ephemeral gully erosion prediction model, the separation of ephemeral gully erosion contribution and the study of ephemeral gully erosion mechanism based on erosion dynamic factors and topographic factors and their interaction.

    • Impact of Initial Soil Moisture and Rainfall Energy on Splash Erosion Characteristics of Black Soil Aggregate

      2024, 38(2):68-75. DOI: 10.13870/j.cnki.stbcxb.2024.02.015

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      Abstract:[Objective] To investigate the influence of rainfall energy and initial moisture content on the mechanism of soil aggregate splashing erosion. [Methods] The typical cultivated black soil in northeast China was selected as the research object. Artificial simulated rainfall experiments were conducted to explore the splashing erosion characteristics of soil aggregates with varying initial moisture content, rainfall energy, and initial particle size of aggregates. [Results] (1) The splash erosion of the four kinds of black soil aggregates with initial particle size was highest when the initial soil moisture level was 4%, and the splash erosion of the aggregates with an initial particle size <0.25 mm was 1.21 to 5.50 times that of the aggregates with different particle sizes under the same rainfall energy conditions. Furthermore, as the initial soil moisture increased, the splash erosion of the aggregates within each particle size group decreased initially, but increased when the initial soil moisture surpassed 25%. (2) The splash erosion of four initial particle size black soil aggregates increased with the increase of higher rainfall energy. When the rainfall energy reached 909 J/(m2·h) (equivalent to 5 m), the splash erosion of the different-sized black soil aggregates increased by 15.37 to 20.70 (<0.25 mm), 52.30 to 417.60 times (0.25~1 mm), 51.58~359.36 times (1~3 mm), 68.73~777.99 times (3~5 mm), respectively. Notably, a clear threshold was observed for splash erosion of aggregates with different initial particle size. When the rainfall energy exceeded 529 J/(m2·h) (equivalent to 2 m), there was a significant difference in splash erosion among different rainfall energy gradient. (3) The analysis highlighted that rainfall energy was the primary factor affecting splash erosion. It exhibited a direct effect with a correlation coefficient of 0.811, demonstrating a significant positive influence. Conversely, the direct effects of initial soil moisture and initial particle size of aggregates were significantly negative, with correlation coefficients of 0.193 and 0.352, respectively. [Conclusion] The research findings can provide a scientific basis for investigating the mechanisms of slope soil erosion in the black soil regions of Northeast China, as well as for establishing process-based models for soil erosion.

    • Attribution Identification of Runoff Change Before and After Impoundment in the Three Gorges Reservoir Area Based on Budyko Hypothesis

      2024, 38(2):76-84,245. DOI: 10.13870/j.cnki.stbcxb.2024.02.038

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      Abstract:[Objective] Runoff changes under the combined influence of climate change and human activities. Exploring the temporal and spatial evolution of runoff and its causes has important guiding significance for the scientific operation of reservoirs and the sustainable use of water resources. [Methods] Based on the meteorological and hydrological data of the Wanzhou section of the Three Gorges Reservoir Area from 1960 to 2019, Mann-Kendall trend test, Pettitt mutation analysis and wavelet analysis were used to analyze the spatial and temporal evolution characteristics of runoff before and after the impoundment in the Three Gorges Reservoir Area. Finally, two Budyko hydrothermal coupling equilibrium equations were used to quantitatively calculate the influence rate of climate change and human activities on runoff change. [Results] (1) The annual runoff in the study area showed a significant downward trend (|z|>2.58), with the inflection point appearing in 2003 (the impoundment year of the Three Gorges Reservoir Area), after which the annual distribution was more uniform. (2) Compared to the period before impoundment, the contribution rates of climate change and human activities to the reduction of annual runoff in the study area after impoundment were 27.9% to 29.2% and 70.8% to 72.1%, respectively. (3) Human activities primarily influence the annual runoff of the basin by altering the type of land use and the construction of water conservation projects. [Conclusion] This study quantitatively describes the impact of human activities on runoff changes, and provides the oretical support for the next stage of water resources management in the Three Gorges Reservoir Area.

    • Analysis of Spatial and Temporal Evolution and Dynamic Driving Force of Soil Water Erosion in the Middle Reaches of the Yellow River in the Rich and Coarse Sediment Area

      2024, 38(2):85-96. DOI: 10.13870/j.cnki.stbcxb.2024.02.014

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      Abstract:[Objective] To reveal the spatial and temporal evolution characteristics of soil water erosion in the middle reaches of the Yellow River in the rich and coarse sediment area from 2000 to 2020, and analyze its dynamic driving force. [Methods] Based on the RUSLE model, the annual soil water erosion modulus in the rich and coarse sediment area was calculated, and the variation characteristics of soil water erosion intensity in 2000, 2005, 2010, 2015, and 2020 were analyzed. The spatial-temporal characteristics of soil water erosion modulus were explored by using the Sen+MK trend analysis method combined with the Hurst index, and the factor probing in the parameter-optimal geographical detector with the interactive probing were used to quantify the explanatory power of six factors, namely average annual precipitation, elevation, slope, vegetation cover, land use/cover type, and soil type, on the spatial distribution of soil water erosion. [Results] (1) The area of moderate, intense, extremely intense and severe erosion in the rich and coarse sediment area decreased by 48.09%, 77.93%, 83.01%, and 36.13%, respectively, and the area of slight and mild erosion increased by 46.22% and 0.33%, respectively, in the five periods from 2000 to 2020. At the present stage, the sandy and coarse sandy area was dominated by slight and mild erosion, and the proportion of the two was 62.49% and 42.07% respectively. (2) The overall inter-annual change of soil water erosion modulus in the rich and coarse sediment area showed a fluctuating and significant downward trend, from 2 214.89 t/(km2·a) in 2000 to 1 169.44 t/(km2·a) in 2020. The spatial variation trend of soil water erosion modulus in the rich and coarse sediment area from 2000 to 2020 was mainly in a decreasing state, accounting for 76.13% of the total area, and would continue to be in a decreasing state in the future, with an area share of 62.50%. (3) The explanatory power of the interactions among the six factors was greater than that of single factor, and it was mainly manifested as nonlinear enhancement and double-factor enhancement; soil water erosion in the rich and coarse sediment area was dominated by precipitation and land use/cover in 2000—2005, and by vegetation cover and land use/cover in 2010—2020. [Conclusion] Soil water erosion condition in the rich and coarse sediment area will be improved continuously from 2000 to 2020; in the future, the soil water erosion modulus of 62.50% of the regions will continue to decline or decline in the future, but there is still a potential risk of increase in 20.44% of the area; the land use/cover pattern has changed by the project of returning farmland to forests and grassland, which made the soil water erosion in the rich and coarse sediment area. The driving force of soil water erosion in the rich and coarse sediment area changes dynamically; the slope factor needs to be fully considered when optimizing the land use/cover pattern for the prevention and control of soil water erosion in the rich and coarse sediment area in the future.

    • Simulation Effect Analysis of RUSLE Model on Slope Soil Erosion Restored by Reclaimed Vegetation in Loess Plateau

      2024, 38(2):97-108. DOI: 10.13870/j.cnki.stbcxb.2024.02.001

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      Abstract:[Objective] To explore the effectiveness of the Revised Universal Soil Loss Equation (RUSLE) model in simulating soil erosion on slope surfaces during vegetation restoration in the Loess Plateau. [Methods] This study utilized rainfall-runoff and sediment data from ten runoff plots in Ansai Fangta small watershed in northern Shaanxi Province during 2016—2022. Utilizing various commonly used algorithms for RUSLE model factors specific to the Loess Plateau, a total of 144 combinations of factors were simulated to estimate soil erosion on restored slopes. The Nash-Sutcliffe efficiency coefficient (NSE) and root mean square error (RMSE) were used to evaluate the effectiveness of the model simulations. [Results] The results indicated that the simulated soil erosion on restored slopes using the 144 factor combinations ranged from -38.47 to 0.19 for NSE and from 1.92 to 12.65 t/(hm2·a) for RMSE, suggesting limited model performance. The selected algorithms for RUSLE model factors appeared to be inadequate for assessing soil erosion on slopes undergoing vegetation restoration. Further improvements are needed for the individual factors within the RUSLE model. When applying RUSLE model to simulate soil erosion on restored slopes in the Loess Plateau, it is recommended to utilize data with high temporal resolution to reduce errors in calculating the R-factor, and comprehensively consider the effects of soil physical and chemical properties such as soil organic matter content, soil particle size and aggregate structure and bulk density on K-factor, and the the effects of vegetation coverage, vegetation height, litter, and biological crust and C-factor, full consider to slopes steeper than 10° in refining the LS-factor. [Conclusion] The RUSLE model is not well-suited for simulating soil erosion in the context of vegetation restoration on abandoned slopes in the Loess Plateau.This study provides some reference for the research and development of soil erosion model and the application of RUSLE model on the slope of vegetation restoration in the Loess Plateau.

    • Effects of Freeze-thaw Cycles on Gully Wall Collapse in the Black Soil Region of Northeast China

      2024, 38(2):109-117,325. DOI: 10.13870/j.cnki.stbcxb.2024.02.028

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      Abstract:[Objective] To evaluate the contribution of freeze-thaw cycle (FTCs) to gully erosion by measuring the collapse volume of gully wall collapse during FTCs. [Methods] From 2016 to 2018, a total of 463 collapse points in 36 gullies were selected for field investigation. Based on the investigation results, there were two types of wall collapse: massive collapse and loose accumulation. The morphology parameters of two kinds of accumulations were measured at each collapse point, including the volume of the collapsed soil, the width and depth of the gull coross-section, and the shear force and hardness of soil of the corresponding gully wall soil. [Results] (1) The average collapse strength of gully wall collapse caused by FTCs during the three-year study period is 16.12 m3/(km·a). The two types of collapse occurred randomly within the gully, and the single point freeze-thaw collapse mainly concentrated in 0~3 m3, but the amount of soil caused by massive collapse was larger. (2) The transverse width and depth of the gully were the main factors affecting the collapse of the gully wall, and the collapse amount increased with the increase of the width-depth ratio. When the width-depth ratio>2.71, the collapse amount increased rapidly. (3) The amount of gully collapse was closely related to the shear force and hardness of the soil on the gully wall. [Conclusion] The freeze-thaw collapse of the gully wall was closely related to the width and depth of the gully cross-section, the freeze-thaw collapse accounted for 3.28% to 23.68% of the sediment yield of the gully erosion, and its influence was equivalent to that of the headward erosion of gully head. The research results provide data support for quantitatively evaluating the contribution of FTCs to gully erosion.

    • Effects of Slope Gradient and Rainfall Intensity on Sediment Yield in the Colluvial Deposits of Southern Guangxi Under Simulated Rainfall

      2024, 38(2):118-125. DOI: 10.13870/j.cnki.stbcxb.2024.02.011

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      Abstract:[Objective] To reveal the influences of slope gradient and rainfall intensity on the erosion and sediment yield characteristics of the colluvial deposits from Benggang, and to provide a scientific basis for soil and water loss prediction and control of the colluvial deposits in southern Guangxi. [Methods] The indoor experiment of simulated rainfall was carried out to investigate the erosion and sediment yield phocesses of colluvium slope under different slope gradients (15°, 20°, 25°) and rainfall intensities (60, 90, 120 mm/h). [Results] The results showed that the variation processes of the erosion rate of the colluvium were relatively stable, and the erosion rate was mostly lower than 5.0 g/(m2·s), and showed a certain downward trend when the rainfall intensity was 60 mm/h under different slope conditions. While, the erosion rate fluctuated to increase first, and then decreased under the rainfall intensity of 90 to 120 mm/h. The maximum erosion rate during each rainfall increased with the increase of rainfall intensity and slope gradient, and the maximum erosion rate occurred within 0 to 25 min and tended to advance with the increase of slope gradient. The sediment yield amount (from 3.64 to 48.07 kg/m2) increased with the increase of rainfall intensity and slope gradient, and the nonlinear regression result (a power function) between the sediment yield amount and rainfall intensity and slope gradient was better than the linear regression result. The correlation between sediment yield amount and the interaction of slope gradient and rainfall intensity was the most significant and showed a high-significant linear function relationship. [Conclusion] The sensitivity coefficient of the sediment yield amount to rainfall intensity was higher than that to slope gradient, and the influence of rainfall intensity on sediment yield was stronger than slope gradient. gradient Slope drainage measures should be taken in the prevention and control of colluvial deposit erosion.

    • Soil Quality Evaluation and Obstacle Factors of Erosion Slop in Karst Trough Valley Area

      2024, 38(2):126-135. DOI: 10.13870/j.cnki.stbcxb.2024.02.007

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      Abstract:[Objective] In order to accurately evaluate the soil quality characteristics of the dip/anti-dip erosion slope in the karst trough valley screen out suitable soil quality evaluation methods and explore the obstacle factors limiting soil quality in this area. [Methods] Five typical land use types (forest land, grassland, bare land, corn land, pepper land) were selected as the research objects in Qingmuguan Karst trough Valley of Chongqing, and the minimum data set (MDS) was established by principal component analysis combined with Norm value. The nonlinear soil quality evaluation method and membership function were used to evaluate the soil quality of the diplanti-dip erosion Slope and down-slope in the karst trough valley. [Results] (1) MDS of soil quality evaluation indexes in karst troughs valleys included capillary water capacity, capillary porosity and total phosphorus. (2) According to the nonlinear soil quality evaluation method, the soil quality of anti-dip erosion slope (0.519) was better than that of dip erosion slope (0.451). The soil quality of anti-dip erosion slope forest land was the best (0.653), and that of pepper field was the worst (0.426). (3) The coefficient of determination (R2) of the nonlinear evaluation method was higher than the membership function in the dip erosion slope and the anti-dip erosion slope, so the non-linear scoring model was more suitable for the karst trough valley. (4) There were significant differences in soil quality barrier factors, and only total nitrogen was the common barrier factor. [Conclusion] Appropriately increasing grassland and forest cover can improve soil quality in karst trough and valley area. The results of this study can provide basis for soil quality control and rational fertilization of slope erosion along/against slope in karst trough valley according to local conditions.

    • Evaluation of the Accuracy of Extraction of Slope and Length Based on DEM of GF-7 Satellite

      2024, 38(2):136-146. DOI: 10.13870/j.cnki.stbcxb.2024.02.008

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      Abstract:[Objective] Slope and slope length are essential topographic factors, and their calculation accuracy directly affects the evaluation accuracy of slope soil erosion model. The high-precision elevation measurement capability of Gaofen-7 satellite has great potential in the accurate extraction of terrain factors, and it is expected that it can be used in the extraction of slope and slope length to achieve accurate expression of terrain. It is necessary to evaluate the accuracy of the results of slope length extraction using the DEM of Gaofen-7 satellite. [Methods] The slope and slope length of DEM generated by Gaofen-7 satellite, 1∶10 000 topographic map and LiDAR images in 4 small basins in Wubu County, Shaanxi Province were extracted by using the terrain factor (LS) calculation tool. Correlation coefficient (r), relative deviation (RE) and absolute deviation were used as evaluation indexes to evaluate the accuracy of extraction of topographic factors by Gaofen-7. [Results] Compared with the slope and slope length of LiDAR and 1∶10 000 topographic map, the average slope extracted by GF-7 was 7.50%~9.02% lower, and the slope length was 1.83%~19.35% larger. However, the area distributions of slope length and slope derived from the three data sources had no significant difference. Comparing the results of slope and slope length, the discrepancy in slope (RE: 16.46%~44.26%) derived from different sources is significantly lower than that (RE: 75.25%~140.87%) was slope length. The discrepancy between different sources was enhanced in gully areas (RE of slope 15.48%~56.63%, slope length: 50.02%~130.79%), while being decreased in inter-gully areas (RE of slope 21.28%~63.61%, RE of slope length 93.01%~192.51%). [Conclusion] It was feasible to obtain areal grading characters of slope or slope length and slope of specified locations using DEMs generated from Gaofen-7 satellite, while the results of slope length for specified locations were less reliable. In conclusion, the Gaofen-7 satellite had a great advantage in describing the spatial distribution of slope length and slope at the watershed scale, while being less capable of capturing slope length and slope at a specific site.

    • Effects of Snow Cover Change on the Content of Base Ions and Available Silicon and Aluminum of Black Soil in Northeast China

      2024, 38(2):147-156,164. DOI: 10.13870/j.cnki.stbcxb.2024.02.006

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      Abstract:[Objective] In order to investigate the seasonal changes of base ions and available silicon and aluminum contents of black soil in northeast China under the change of snow depth in winter. [Methods] The environmental factors (temperature and humidity, moisture content, pH, total organic carbon), base ions, available silicon and activated aluminum of black soil in northeast China farmland were measured in snow removal group (SR), snow reduction group (SL), natural snow control group (C) and snow enhancement group (SA) were determined by artificial control of snow depth. The change process of the content of base ions and available silicon and aluminum in soil and their response to soil environmental factors were analyzed. [Results] The decrease of snow depth weakened the heat preservation effect of snow on black soil under seasonal snow cover, and the temperature and humidity (unfrozen water content) of 0—30 cm soil decreased significantly, which reduced the HCO3- content carried by unfrozen water during water and salt migration. The average pH of the soil was affected by the HCO3- content by the changes of -0.06, -0.04, - 0.02, and 0.01, respectively. With the decrease of soil alkalinity, the substitution ability of low-priced cations to high-priced cations in soil colloidal adsorption potential was enhanced, which increased the contents of exchange monvalent cations (Na+, K+), and decreased the contents of exchange and carbonate bivalent cations (Ca2+, Mg2+). Carbonate bivalent cation and exchange Na+ had positive and negative effects on TOC content, respectively, and the mean total organic carbon (TOC) content increased by 0.87, 1.09, 1.32 and 1.48 g/kg with the decrease of snow depth, respectively. The interaction between base ions and soil pH and TOC resulted in the decrease of soil pH and TOC content under the condition of reduced snow depth, which had an indirect effect on soil available silicon and aluminum content. The decrease of TOC content weakened the soil retention of low-active aluminum humate (Al-HA), and the decrease of pH promoted the conversion of low-active aluminum to high-active exchange aluminum (Ex-Al) and monomer hydroxyl aluminum (Hy-Al), which increased the soil aluminum toxicity, and promoted the dissolution of available silicon, resulting in the loss of soil silicon. [Conclusion] The reduction of seasonal snow cover in the middle and high latitudes caused by climate warming will affect the material and energy distribution of the black soil in Northeast China in winter, and thus change the growth and development environment of crops in the growing season. This study provided a certain scientific basis to reveal the seasonal variation process of soil mineral elements in the black soil region in Northeast China in winter.

    • Effect of Algae Crusting Cover on Soil Structure Under Freeze-Thaw Conditions

      2024, 38(2):157-164. DOI: 10.13870/j.cnki.stbcxb.2024.02.003

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      Abstract:[Objective] To investigate the effects of biological crustal cover and freeze-thaw on soil structure. [Methods] The effects of different freeze-thaw times, initial soil water content before freeze-thaw and biological crusting (algae crust) cover on soil structure characteristics was employed to analyze the indoor simulated freeze-thaw method. [Results] (1) The soil structure index (IGSS) obtained by orthogonal experiment was between 75.57~96.57, the signal-to-noise ratio (S/N) was between 37.55~39.70 dB, and the optimal factor combination ascertained by the Taguchi method was 15 freeze-thaw cycles, 15% initial water content, and 80% algal crust coverage, and the predicted results were IGSS=98.09, S/N=39.89 dB. (2)A positive correlation was observed between IGSSIGSS was positively correlated with freeze-thaw times, initial water content and algal crusting coverage, and the primary influences on the soil structure index were ranked as initial water content > freeze-thaw times > algal crusting coverage. The contribution rates of each factor to alterations in the soil structure index were initial water content (52.17%) > freeze-thaw frequency (31.95%) > algae crusting coverage (2.12%). (3) The change of soil structure index comes from the loss of soil water and pore expansion during the freeze-thaw process, and algae crusting can slow down the loss of water during the freeze-thaw process, thereby decelerating the IGSS alteration. [Conclusion] Orthogonal experiments in this research explored the effect of algae crusting cover on soil structure under freeze-thaw conditions, and the results could provide a theoretical reference for the study of soil freeze-thaw process under complex conditions.

    • Spatiotemporal Characteristics of Land Use/Cover Changes in the Yellow River Basin Over the Past 40 Years

      2024, 38(2):165-177,189. DOI: 10.13870/j.cnki.stbcxb.2024.02.030

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      Abstract:[Objective] The study on the spatial-temporal change characteristics of land use/cover is of great significance for the protection and rational development of land resources in the Yellow River Basin, and can provide an important reference for the implementation of ecological protection and high-quality development strategy in the Yellow River Basin. [Methods] Based on the annual land use/cover data of the Yellow River Basin from 1980 to 2021, the characteristics of land use/cover change in the Yellow River Basin in recent 40 years were investigated by using Mann-Kendall and sliding t-test, geographic information TUPU standard deviation ellipse and gravity shift model. [Results] (1) From 1980 to 2021, forest land, shrub, water area, and construction land increased significantly, while the cultivated land, grassland, and wetland decreased significantly. (2) The periods of land use/cover change in the basin can be divided into 1980—1992, 1993—2001, 2002—2012, and 2013—2021, and the quantitative structure gradually presented by rapid changes, and the changes of construction land, wetland and water area were sensitive. The balance of land-use structure was gradually increased, and the stage changes showed a high correlation with the implementation of major strategic measures, and more consistent with the divided stage. (3) In the middle and upper reaches of the basin, the main changes were from 2012 to 2021 and intermittent changes, and the main changes were from 2001 to 2012 and from 2012 to 2021, and the main changes were from 2001 to 2012 and from 2012 to 2021, and the main changes were from arable land to construction land and grassland. The basin changed frequently in northern Ningxia, eastern inner Mongolia and some areas along the Yellow River system. (4) The centers of gravity of wetland, water and construction land moved westward, showing concentrated distribution to the southwest, east and northwest, respectively. [Conclusion] The overall trend of land use structure becomed better under the guidance of policies. In the future, we should pay more attention to wetlands and areas with frequent land use changes.

    • Ecosystem Service Functions in the Upper Reaches of the Yellow River in Sichuan Based on Land Use Change Value Evaluation

      2024, 38(2):178-189. DOI: 10.13870/j.cnki.stbcxb.2024.02.026

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      Abstract:[Objective] To quantitatively study the relationship between land use change and ecosystem service value in Sichuan section of the upper reaches of the Yellow River in the past 20 years, and to evaluate the effect of comprehensive ecological management in this section, so as to provided a basis for improving ethnic regional spatial planning, ecological environmental protection and management, and promoted the high-quality development of the Yellow River Basin. [Methods] Using the land use data of the upper reaches of the Yellow River in Sichuan in 2000, 2010 and 2020, land use change was analyzed based on land use dynamic attitude and land use matrix, and the economic value of the ecosystem service value equivalent per unit area of the terrestrial ecosystem in China was revised. The effects of land use change on the ecosystem service value in the upper reaches of the Yellow River from 2000 to 2020 in Sichuan were quantitatively studied. [Results] (1) From 2000 to 2020, the land use area of forest, desert, wetland and water system in the upper reaches of the Yellow River in Sichuan showed an increasing trend, while the land use area of cultivated land, shrub, grassland and glacial and snow in the upper reaches of the Yellow River showed a decreasing trend, and the land use change in 2010—2020 was more significant than that in 2000—2010. (2) The ecosystem service value of the upper reaches of the Yellow River in Sichuan in 2000, 2010 and 2020, was 1.27×1010, 2.51×1010, 3.92×1010 yuan, respectively, showing an increasing trend. The sensitivity analysis showed that the analysis results were reliable. Amongall land use types, grassland made the most significant contribution to total ecosystem value, and the contribution rate of grassland ecological service was 93.90% and 72.90% in 2000—2010 and 2010—2020, respectively, followed by wetland and forest land. (3) In the study area, the value of each individual ecosystem service showed an increasing trend in the past 20 years, and the sub-value of regional ecological service function was regulatory service>support service>supply service>cultural service. Among the 11 individual functions, the significant service value was climate regulation, hydrology regulation, soil conservation and biodiversity. The sum of the four items accounted for more than 69.50% of the total value. Land use change in the upper reaches of the Yellow River in Sichuan affected the changes of regional ecosystem service value, and grassland was the most significant, followed by wetland and forest land. [Conclusion] The results showed that the results of ecological governance in the past 20 years have been gradually enhanced, and the ecological environment has continuously improved.

    • Effects of Different Ecological Measures on Water Use Characteristics of Amorpha fruticosa in Open Pit Coal Mine Areas

      2024, 38(2):190-196. DOI: 10.13870/j.cnki.stbcxb.2024.02.018

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      Abstract:[Objective] To explore the water use characteristics of typical plants under different ecological measures at the waste dump, improve plant water use efficiency, and accelerate the ecological restoration process in mining areas. [Methods] Six ecological measures (control, inoculation, green fertilizer, inoculation+green fertilizer, inoculation+weathered coal, inoculation+green fertilizer+weathered coal) were implemented at the waste dump of the Heidaigou Coal Mine to treat Amorpha fruticosa. Stable isotopes of hydrogen and oxygen in water were combined with other techniques. [Results] (1) The soil moisture content of the waste dump was 3% to 9%, which was lower in the 0-30 cm and 70-100 cm soil layers, and higher in 30-70 cm soil layer. (2) Amorpha fruticosa obtained water from precipitation and soil. The soil water undergoes significant fractionation processed in the 0-30 cm soil layer, and exhibited significant differences among different ecological measures, with the green fertilizer treatment showing the highest and inoculation+green fertilizer treatment being the lowest. (3) Significant differences existed in the water use characteristics of Amorpha fruticosa under various ecological measures. The inoculation treatment exhibited a higher water use ratio of 53.4% in the 50-100 cm soil layer; The green fertilizer treatment mainly utilized the soil water in the surface layer (0-20 cm), which was 42.6%; The treatment of inoculation and green fertilizer had a relatively uniform proportion of soil water use in each layer. [Conclusion] The inoculation + green fertilizer treatment optimized the water use characteristics of Amorpha fruticose plants, increased the utilization ratio of surface and deep soil water, and can be used as an ecological reclamation measure for waste disposal sites, which promoted the ecological recovery rate and effect of arid mining areas in the western region.

    • Soil Water Distribution and Water Supply Characteristics of Farmland to Apple Orchard in Their Adjacent Areas on the Loess Tableland

      2024, 38(2):197-204,215. DOI: 10.13870/j.cnki.stbcxb.2024.02.029

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      Abstract:[Objective] To investigate the spatial distribution and cooperative utilization characteristics of soil water under the orchard-farmland mosaic pattern in the southern Loess Tableland. [Methods] The 10-year-old, 21-year-old, and 25-year-old apple orchards (AO10, AO21, and AO25) and their adjacent farmland were selected in Changwu tableland were selected to quantitatively calculate the contribution of soil water storage to water consumption of orchard. By measuring the soil water content at relevant sites in the orchard-farmland interface zone after the rainy season in 2021. [Results] The precipitation in 2021 is 756 mm, which was a typical wet year. The rainfall infiltration depth of farmland and AO21, AO25 orchards reached 8.4, 7.0, and 5.0 m at the end of November, respectively. AO10 orchard-farmland boundary zone is 4 m deep, the soil water content in the lower part is larger than that in the upper part, and the average soil water content was 25.5% in the 4—10 m soil layer. In AO21 orchard, the average soil water content of the 0—7 m soil layer was 22.1%, and that of the 7—10 m soil layer was 15.0%. the average soil water content of the 0—5 m soil layer of AO25 orchard was 20.9%, and that of 5—10 m was 13.6%. The soil dry layer of AO21 and AO25 orchard was below 7.0 and 5.0 m, respectively. In the horizontal direction, the distance of soil water used by AO21 and AO25 orchards from adjacent farmland reached 5 and 8 m, respectively, and the water supply from fields to orchards at the agro-fruit interface was 0.08 and 0.25 m3/m2 when the soil profile was divided by the upper boundary of the dry layer. Below is the actual water supply, which is 0.45 and 0.81 m3/m2, respectively. [Conclusion] The mosaic layout of apple orchards and farmland in the Loess tableland region is a reasonable utilization structure, and factors such as the age of apple trees and the width of adjacent farmland should be considered in land planning and management. The research results will contribute to promote the sustainable utilization and spatial optimization of regional soil water resources.

    • Temporal and Spatial Evolution Characteristics of Carbon Storage in Hefei Ecosystem Based on PLUS and InVEST Models

      2024, 38(2):205-215. DOI: 10.13870/j.cnki.stbcxb.2024.02.033

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      Abstract:[Objective] To seek a new urban development plan of Hefei under the guidance of "double carbon" goal. [Methods] Based on the land use data of Hefei City in the 5th period from 2000 to 2020, under the guidance of territorial spatial Planning of Hefei City, the spatio-temporal evolution law of land use in 2035 was simulated by the PLUS model, and the spatio-temporal change characteristics of carbon storage in Hefei City under multiple scenarios were explored by coupling the InVEST model. And further explore the effect of the comprehensive land use on the carbon storage. [Results] (1) The main characteristics of land use change in Hefei City from 2000 to 2020 were the decrease of cultivated land and forest land, among which cultivated land was the main source of construction land expansion. The law of land change in the natural development and farmland resource protection scenarios was roughly the same, mainly represented by the reduction of cultivated land, forest land and water body. In the green urban development scenario, the area of forest land changed from decreasing to increasing compared with the other two scenarios. (2) Carbon storage in Hefei City decreased year by year from 2000 to 2020, and the carbon loss was the most 2005 to 2010. By 2035, the carbon reserves of natural development scenario, farmland resource protection scenario and green urban development scenario were 138.96×106 t, 140.13×106 t, and 139.81×106 t, respectively. Under the farmland resource protection scenario, the area with the lowest increase of carbon storage significantly slowed down the expansion of the construction land. under the scenario of urban development, forest land changes from carbon loss to carbon sequestration, which was the most potential trend of carbon sequestration. (3) The land utilization rate of green urban development scenario was the highest, which can effectively reduce the threat of comprehensive land use degree to carbon storage loss. [Conclusion] Both farmland resource protection scenario and green accumulation urban development scenario were conducive to urban carbon sequestration development. Implementing parallel policies of ecological protection and urban development, and adjusting comprehensive land use mode were conducive to improving urban carbon loss.

    • Simulation of Runoff and Sediment Changes in the Minjiang River Basin Under Climate and Land Use Change Scenarios

      2024, 38(2):216-233,245. DOI: 10.13870/j.cnki.stbcxb.2024.02.034

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      Abstract:[Objective] Simulating the change of runoff and sediment changes in the watershed under the influence of land use and climate in the future is conducive to making suitable management plans. [Methods] Based on land use and meteorological data, combined with CMIP6 climate model data, PLUS model and SWAT model, the temporal and spatial changes of land use and runoff and sediment under different climate scenarios in 2030 were quantitatively simulated. [Results] (1) The SWAT model exhibited good accuracy in monthly scale in simulation of Minjiang River Basin, in which the R2 and NSE (Nash-Sutcliffe Efficiency) ranged from 0.80 to 0.95 and 0.75 to 0.91, respectively. The R2 and NSE ranged from 0.75 to 0.98 and 0.64 to 0.94 respectively. (2) Using the land use data of 2020 to evaluate the accuracy of the PLUS model, the Kappa coefficient was 0.77, and the simulated construction land and cultivated land in the Minjiang River Basin in 2030 would increase by 325.64 km2 and 1 157.51 km2, respectively. (3) Under the SSP2-4.5 and SSP5-8.5 scenarios, the average precipitation in 2025—2035 would increase by 0.15% and 2.18%, and the average annual temperature would increase by 0.23 and 0.62 ℃, respectively. (4) In the low carbon and high carbon scenarios, only land use change led to an increase of 0.08% and 0.07% in annual mean runoff, and an increase of 0.24% and decreased of 0.05% in annual mean sediment transport, respectively, compared with the baseline period. Compared with the baseline period, the mean annual runoff decreased by 4.76% and 4.11%, and the mean annual sediment transport increased by 18.12% and 0.13%, respectively. The combined effects of land use and climate resulted in a decrease of 4.57% and 3.93% in annual average runoff and an increase of 18.28% and 0.33% in annual average sediment transport compared with the base period, respectively. (5) Under the scenario of future climate and land use comprehensive change, the areas with higher and larger increase in surface runoff and sediment yield were concentrated in the northwestern of the basin centered on Shaowu City in Nanping and the southwest of the basin centered on Jiangle County in Sanming. [Conclusion] These research results provide some reference for the reasonable development and construction of Minjiang River basin in the future.

    • Vertical Characteristics and Seasonal Dynamics of Soil Nitrogen Components at Different Elevations in Liziping Nature Reserve, Sichuan

      2024, 38(2):234-245. DOI: 10.13870/j.cnki.stbcxb.2024.02.016

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      Abstract:[Objective] To reveal the vertical distribution differences of soil nitrogen components (total nitrogen, hydrolyzed nitrogen, ammonium nitrogen, nitrate nitrogen) in Liziping National Nature Reserve in Sichuan Province and their relationships with physicochemical factors. [Methods] In March, June, September and December 2022, the vertical variation characteristics of soil nitrogen components and physicochemical factors at altitudes of 1 800 m, 2 100 m, 2 400 m and 2 700 m in Liziping, Sichuan Province were determined and analyzed, and the relationship between environmental factors and nitrogen components and their seasonal differences were analyzed by multivariate analysis of variance and redundancy analysis. [Results] (1) Altitude, season and their interaction had significant effects on soil nitrogen composition, and in March, June, September and December the ammonium nitrogen content was 2 100 m>2 400 m>1 800 m>2 700 m above sea level, and the nitrate nitrogen content was 2 400 m>2 100 m>2 700 m>1 800 m above sea level, and the gradient increased over the month, the contents of total nitrogen and nitrate nitrogen showed a trend of increasing first, with the maximum content of total nitrogen and nitrate nitrogen being 1.25 g/kg and 8.26 mg/kg, respectively, in December, and the maximum content of hydrolyzed nitrogen and ammonium nitrogen in March being 185.14 mg/kg and 5.80 mg/kg respectively. The variation of total nitrogen, hydrolyzed nitrogen, ammonium nitrogen and nitrate nitrogen along the soil layer was consistent, and formed a "V" shape. (2) The vertical variation characteristics between physicochemical factors and nitrogen components in different seasons and altitudes were significantly different, and the contents of total phosphorus, available phosphorus and available potassium increased first and then decreased along the depth of soil layer. (3) Seasonal differences in the key factors affecting soil nitrogen composition, organic matter, non-capillary porosity, available potassium, total phosphorus, available phosphorus and capillary porosity in March and December, and organic matter, total potassium and capillary porosity, total phosphorus and available potassium in June and September. [Conclusion] This study provides a specific production practice basis for the response mechanism of soil nutrients to altitude and season and the comprehensive management of ecological conservation in nature reserve.

    • Evaluation of Land Use Change and Carbon Storage in Fujian Province Based on PLUS-InVEST Model

      2024, 38(2):246-257. DOI: 10.13870/j.cnki.stbcxb.2024.02.013

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      Abstract:[Objective] The forest coverage rate of Fujian Province is as high as 66.8%, ranking first in China. To investigate the impact of land use changes on carbon storage in Fujian Province is the theoretical basis for exploring the balance between social development and ecological protection. [Methods] Based on the carbon storage module of PLUS model and InVEST model, relationship between the spatiotemporal change characteristics of carbon storage and land use types in Fujian province during 2000—2020 was revealed, and the spatial and temporal changes of carbon storage in Fujian Province during 2020—2030 were predicted from three scenarios: natural development, ecological protection and urban development. [Results] The total carbon reserves in the study area in 2000, 2010 and 2020 were 214.77×107, 214.51×107 and 212.93×107 t, respectively, indicating a downward trend year by years. The development and transformation of land by human activities was the dominant factor leading to changes in carbon stocks, and the conversion of large areas of cultivated land and forest land into urban areas was the primary reason for the decline in carbon stocks. The prediction results showed that compared with 2020, carbon storage under natural development, ecological protection and urban development in 2030 would decrease by 1.47×107 t, increase by 0.17×107 t, and decrease by 1.85×107 t, respectively. The ecological protection scenario was the only development scenario that reversed the decline in carbon stocks. Compared with 2020, the forest area had expanded by 1 900.87 km2 and the forest carbon storage had increased by 2.08×107 t, which could effectively protect the ecology and meet the land requirements for urban development. [Conclusion] Prioritizing forest land protection and controlling the expansion of construction land are crucial prerequisites for Fujian Province to achieve carbon peaking and carbon neutrality goals.

    • Analysis of Landscape Patterns and Spatio-temporal Evolution of Habitat Quality in the PU River Basin Based on the InVEST Model

      2024, 38(2):258-267. DOI: 10.13870/j.cnki.stbcxb.2024.02.024

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      Abstract:[Objective] Through the spatio-temporal dynamic analysis of landscape ecological pattern and habitat quality, the response of habitat quality before and after the implementation of soil and water conservation measures in PU River Basin of Shenyang City was deeply studied, aiming to provide scientific basis for soil and water conservation strategies in small river basins, so as to promote the coordinated growth of the eco-economy and the sustainable and healthy development of regional ecology. [Methods] Based on the land use data and Digital Elevation Model (DEM) of PU River Basin in 2000, 2010 and 2020, combined with the FRAGSTATS and InVEST models, land use transfer matrix, landscape pattern index, habitat quality and habitat degradation degree were used to analyze land use change and explore quality response situation. [Results] (1) During the period from 2000 to 2010, the cultivated land development activities in the PU River Basin were frequent, resulting in a significant decline in the proportion of forest, grassland and other land types; In the period from 2010 to 2020, the construction of the PU River ecological corridor will promote the change of land use, and the cultivated land area will flow to artificial surfaces, forests and grasslands. (2) During 2000 to 2020, the overall landscape pattern of the PU River Basin experienced a process of first becoming complete and then fragmentary. The landscape on both sides of the Puhe River formed a dense pattern of multiple elements, and the habitat in the northern edge of the urban center continued to fragment. (3) From the overall analysis of the basin, the average habitat quality in 2000, 2010, and 2020 was 0.349, 0.329, and 0.354, respectively, showing a trend of first decreasing and then increasing. The mean values of habitat degradation were 0.098, 0.112, and 0.086, which were consistent with the trend in habitat quality. With the construction of the PU River Ecological Corridor, the quality of habitat will be improved significantly in 2020, and the threats to the ecosystem will be reduced. From the analysis of spatial pattern, the northeast and southwest show obvious spatial distribution characteristics. The quality of habitat in the mountainous areas of northeast China and the wetlands of southwest China is generally good, but there is a threat of habitat degradation. [Conclusion] Under the influence of soil and water conservation measures, the ecological pattern of the PU River Basin can be and the degradation of habitat can be effectively inhibited.

    • Impact of Land-use Change on the Value of Ecosystem Services Based on SDG 15.3.1

      2024, 38(2):268-277. DOI: 10.13870/j.cnki.stbcxb.2024.02.032

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      Abstract:[Objective] Sustainable Development Goal 15.3.1 (SDG 15.3.1) is one of the important indicators to characterize land degradation.Exploring the impact of land use change and ecosystem service values (ESVs) on SDG 15.3.1 is a key factor to improve land degradation. [Methods] Based on land use and carbon stock changes, a new evaluation rule was established for SDG15.3.1 index, and the completion of SDG 15.3.1 was evaluated. The equivalent factor method was used to calculate the value of ecosystem services to quantitatively analyse the impact of land use change on ESV. [Results] (1) The land use type change was frequent in the study area, which mainly showed that high forest land, water body and construction land increased, cultivated land, grassland and shrub decreased, and unused land remained basically unchanged; (2) The spatial distribution pattern of ESV was high in the middle, low arround, high in the west and low in the east; From 2000 to 2020, the total ESV loss was 7.32×108 yuan. From 2000 to 2010, the ESV loss of land degradation area was 3.03×109 yuan. From 2010 to 2020, the ESV loss in land degradation areas was 2.28×109 yuan. (3) According to the evaluation results of SDG15.3.1, the indicators of SDG15.3.1 for 2000—2010 and 2010—2020 are 5.22 percent and 4.77 percent, respectively, while the net land restoration area was -1.62×105 hm2 and -2.4×105 hm2. The SDG15.3.1 target had improved, but the zero land degradation growed target is still not achieved. [Conclusion] The research results provided a reference for the impact of land use change on ecosystem services in the process of achieving SDG 15.3.1 in plateau urban agglomerations.

    • Analysis on the Evolution Characteristics and Driving Forces of Territorial Space Pattern in the Qinling-Daba Mountain Area

      2024, 38(2):278-293. DOI: 10.13870/j.cnki.stbcxb.2024.02.025

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      Abstract:[Objective] To scientifically understand the spatio-temporal evolution process and formation mechanism of urban space, agricultural space and ecological space in Qinling-Daba Mountain area is the key to promote the overall coordination of the national spatial development pattern and the rise of the central and western regions, and it is also an urgent need for high-quality transformation and development of the region. [Methods] Based on the methods of spatial transfer matrix, topographic location analysis and random forest regression, the spatial and temporal evolution characteristics and driving mechanism of Qinba Mountain region during 2000—2020 were studied from two dimensions of "pattern scale-topographic location". [Results] (1) In the past 20 years, the cities and towns in the Qinba Mountain area expanded dramatically, and the agricultural and ecological space continued to shrink. While the population of 58.33% of the counties decreased, the urban land was still expanding, and the "total population and urban size" showed a serious polarization. (2) The phenomenon was characterized by urban and agricultural space "climbing up the hills", while ecological space "descended into the valleys". The newly added urban and agricultural space was moved up 1 to 2 topographic positions on average. The dam elevation project of Danjiangkou Reservoir downstream had a significant impact on the overall spatial distribution gradient of the mountainous areas. (3) The dynamic adjustment and replacement of "agricultural space to ecological space" was the leading type of transformation in Qinba Mountain area, and the influence of fiscal expenditure was the most significant. Agricultural space was the main source of new towns, and the scale of urban degradation into agricultural and ecological space was significant in Qinba mountain area. (4) Land development policies, mountain terrain attributes, traffic location conditions and social and economic factors jointly restrict and affect the results of territorial spatial evolution in Qinba Mountain area, and there were obvious differences in the effect intensity and the number of significant factors of various types of factors in different conversion directions. [Conclusion] Promoting the concentration of new towns to the key development zones, scientifically guiding agricultural and ecological space to conform to the topographic gradient layout, carefully carrying out water conservancy project construction, and planning the overall regional layout of the "Three districs and Three lines" will have a positive impact on the optimization of territorial spatial pattern in Qinba Mountain area.

    • Analysis of the Changes in Wetland Landscape Pattern and Driving Factors in the Genhe Basin Over the Past 30 Years

      2024, 38(2):294-303. DOI: 10.13870/j.cnki.stbcxb.2024.02.035

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      Abstract:[Objective] In order to understand the spatiotemporal changes in the wetland of the Genhe Basin, the impacts of climate change and land use change on wetland landscape pattern was clarified. [Methods] The driving factors of changes in wetland landscape pattern in the Genhe Basin between 1990 and 2019 were investigated by analyzing the changes in wetland extent and combining them with climate change during the same period. [Results] The results showed that over the past 30 years, the area of wetlands in the Genhe Basin had decreased by 31.89%, the number of patches had increased by 3.74%, and the landscape fragmentation index had increased by 4.48. The overall degradation of wetland areas in the watershed was significant, while the overall number of wetland patches in the watershed had increased. From 1990 to 2004, wetland areas in the watershed showed a significant degradation trend (p<0.05). There was a significant positive correlation between wetland areas and annual precipitation, while there was a significant negative correlation between landscape fragmentation index and annual precipitation. It was inferred that annual precipitation was the main factor causing significant changes in wetland landscape patterns in the Genhe Basin. From 2004 to 2019, the degradation trend of wetlands in the watershed was not significant (p>0.05), and the average annual temperature showed a non-significant increasing trend (p>0.05). There was a significant negative correlation between landscape fragmentation index and average annual temperature, which might be due to the melting of shallow permafrost in the watershed due to rising temperatures, leading to a decrease in wetland fragmentation during this period. [Conclusion] The research results are of great significance for maintaining biodiversity and stability of wetland ecosystems in the Genhe Basin, promoting coordinated and interactive wetland-dryland relationships, and ensuring sustainable development of wetland resources.

    • Effect of Soil Aggregate on Preferential Path in Gully Systemof Dry-hot Valley

      2024, 38(2):304-315. DOI: 10.13870/j.cnki.stbcxb.2024.02.012

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      Abstract:[Objective] To investigate the impact of soil aggregate structure on the formation of preferential pathways in the gully system of the dry-hot valley of the Jinsha River to enhance our understanding of soil moisture and solute transport in the gully system. [Methods] We selected different sections (i.e., catchment area, gully head, gully bed, and gully bottom) of both active and stable gullies in the dry-hot valley of the Jinsha River as our research subjects. We used staining tracers and morphometric image analysis techniques to extract the preferential pathways from the soil level profile. RDA (Redundancy Analysis), gray correlation, and coupled coordination were used to explore the relationship between soil aggregate structure and preferential pathways. [Results] (1) The stability of soil aggregates in stable gullies were higher than those in active gullies. Except for specific soil layers, the contents of mechanically stable aggregates (>0.25 mm, [QX(Y12#]DR[QX)]0.25), water-stable aggregates (>0.25 mm, [QX(Y12#]WR[QX)]0.25) and average mass diameter (MWD) in active gully were significantly lower than those in the stable gully ([QX(Y12#]p[QX)]<0.05). The aggregate destruction rate (PAD) and unstable aggregate index ([QX(Y12#]E[QX)]LT) showed the opposite trend. As the gully system extends from the catchment towards the gully bottom, the fraction of large soil and the stability of aggregates all decreased. (2) The number and connectivity of preferential pathways in active gullies were higher than those in stable gullies. However, the connectivity of the preferential pathways in the gully system deteriorated as it extended from the catchment to the bottom of the gully. The preferential pathways with a diameter>10 mm served as primary channel. The Simpson index of active gullies exhibited an increase by 3.12% compared to stable gullies, indicating a higher richness of preferential pathways across different diameter classes. (3) The formation and distribution of preferential pathways were affected by the stability of soil aggregates, and MWD and WR0.25 were strongly correlated with the number of preferential pathways and had the most significant influence ([QX(Y12#]p[QX)]<0.01). (4) As the gully system extended from the catchment to the bottom of the gully, the coupling coordination between the soil aggregate structure and the preferential pathways decreased. Overall, the order of performance was as follows: gully head>catchment area>gully bottom>gully bed. [Conclusion] Soil aggregate structure is an of the important driving factors for the formation of preferential paths, and the distribution of preferential paths has significant impact on the development of gully systems in dry-hot valleys.

    • Response of Growing Season Soil Carbon and Nitrogen Components to Warming and Nitrogen Addition in Marshy Meadows of the Gahai Wetland Area

      2024, 38(2):316-325. DOI: 10.13870/j.cnki.stbcxb.2024.02.020

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      Abstract:[Objective] To examine the response characteristics of soil carbon and nitrogen fractions in alpine wetland soil to climate warming and nitrogen deposition. [Methods] Using open-top box warming (OTC) and adding exogenous nitrogen (NH4NO3) to simulate future climate warming and nitrogen deposition tests, four treatments were established, namely control (CK), warming (W), nitrogen application (N), and warming nitrogen (WN). The soil carbon and nitrogen levels were quantified after 1.5 years. [Results] (1) The utilization of the open top box warming device resulted in a notable elevation of the mean temperature at 0—20 cm soil layer by 1.126 ℃. Additionally, this intervention led to a significant decrease in the water content (SMC) and pH levels, as well as the concentrations of soil total nitrogen (TN), microbial nitrogen (MBN), ammonium nitrogen (NH4+—N), organic carbon (SOC), and dissolved organic carbon (DOC) at the 0—10 cm soil layer. Conversely, there was an observed increase in the concentration of nitrate nitrogen (NO3-—N). (2) Nitrogen application considerably lowered the contents of NH4+—N and SOC in all the soil layers, as well as those of the contents of microbial biomass carbon (MBC) and DOC in soil layers 10—20 cm deep, but increased the contents of TN, MBN, and NO3-—N. (3) The application of nitrogen through warming conditions resulted in a large rise in SMC, TN, NO3-—N, and MBC content. Conversely, it led to a significant reduction in MBN, NH4+—N, and DOC. (4) Correlation analysis showed that there was a positive correlation between soil moisture and all physicochemical factors, and soil carbon and nitrogen components were positively correlated. [Conclusion] The results indicated that the simulated warming application of nitrogen alleviated the temperature and nitrogen limitation of plant growth in the Gahai wetland, promoted the accumulation of TN, and had a greater impact on the soil microbiota biomass carbon and nitrogen , which led to the conversion of soil microbial biomass carbon and nitrogen activities and distribution characteristics.

    • Effects of Contour Reverse-Slope Terrace on the Microecology of Rhizosphere in Different Farming Systems

      2024, 38(2):326-338. DOI: 10.13870/j.cnki.stbcxb.2024.02.027

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      Abstract:[Objective] To study the effect of contour reverse-slope terrace (CRT) on micro-ecological characteristics of rhizosphere soil in maize continuous cropping and maize-kidney bean rotation system. [Methods] With corn bean wheel as the study object and corn bean joint as the control, the crop root exudates and soil microbial community composition and structural characteristics of were analysed by GC-MS and high-throughput sequencing technology by combining field in-situ monitoring and sampling with laboratory analysis. To study the effects of CRT on the species and content of root exudates and the composition and diversity of soil microbial community in maize continuous cropping and maize-kidney bean rotation. [Results] (1) The relative content change of root exudates was more prominent in CRT measures and more significant in crop rotation mode. (2) CRT2 treatment had a more significant effect on improving the quantity, richness and diversity of soil microbial community. (3) Under the interaction between root exudates and soil microorganisms, the pair-based correlation between root exudates, soil microorganisms, and soil environmental factors was more significant under CRT2 treatment. [Conclusion] CRT changed the root soil microecological environment of crops by changing the root secretion content of maize continuous cropping and maize-kidney bean rotation, and improved the number, diversity and richness of soil microorganisms. Moreover, the combination of this measure and corn-kidney bean rotation can improve the micro-ecology of root soil more significantly. The research results provide theoretical basis for crop planting, cultivation method selection, soil microenvironment improvement and soil erosion control.

    • Effects of Understory Vegetation on Soil Phosphorus Morphological and Availability in Larix gmelinii Forest in the Cold Temperate Zone

      2024, 38(2):339-350,363. DOI: 10.13870/j.cnki.stbcxb.2024.02.031

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      Abstract:[Objective] Due to the large differences in understorey vegetation and soil physicochemical properties of Larix gmelinii forest in the cold temperate zone of the Rreater Khingan Mountains, the characteristics and availability of soil phosphorus morphological changes of Larix gmelinii forest under different forests were studied, so as to provide scientific data for scientific evaluation of soil phosphorus supply level and phosphorus cycle in the cold temperate zone forest. [Methods] Four kinds of understory vegetation in the cold temperate zone of the Greater Khingan Mountains, namely, Larix gmelinii forest (Rhododendron simsii-Larix gmelinii forest, Rhododendron tomentosum-Larix gmelinii forest, Carex schmidtii-Larix gmelinii forest and Moss-Larix gmelinii forest) were selected as the research objects. Soil samples from the 0—5 cm, 5—10 cm and 10—20 cm soil layer were collected from June, August and October 2022. Hedley phosphorus classification method was used to determine the phosphorus content of different forms in soil. [Results] (1) During the observation period, soil active phosphorus (H2O—Pi, NaHCO3—Pi, NaHCO3—Po) and medium active phosphorus (NaOH—Pi, NaOH—Po) of the four understorey vegetation Larix gmelinii forest showed a decrease trend from June to October, and the content of medium active phosphorus accounted for 30.08% to 52.80% of total phosphorus.The content of inorganic phosphorus was higher than that of organic phosphorus. The content of active phosphorus and medium active phosphorus in 0—20 cm soil layer of Rhododendron simsii-Larix gmelinii forest and Rhododendron tomentosum-Larix gmelinii forest were higher than those of the Carex schmidtii-Larix gmelinii forest and Moss-Larix gmelinii forest. The soil stability phosphorus (HCl—Pi, HCl—Po, and residual—P) in the Carex schmidtii-Larix gmelinii forest was significantly higher than that in the other three larix forests, and the stable state phosphorus accounted for 58.86%~65.81% of the total phosphorus. (2) Soil total phosphorus (TP), available phosphorus (AP) and phosphorus activation coefficient (PAC) in Larix gmelinii forest were 391.81 to 1 081.02, 7.34 to 83.90 mg/kg, and 1.62% to 7.76% from June to October, respectively. The content of AP and PAC in the soil of the Rhododendron simsii-Larix gmelinii forest and Rhododendron tomentosum-Larix gmelinii forest were higher than those of the other two larix forests, showing higher phosphorus availability. On the other hand, there was insufficient phosphorus supply in the soil layer of the Carex schmidtii -Larix gmelinii forest and Moss-Larix gmelinii forest from 5—10 cm and 10—20 cm in August and October. (3) Soil moisture contentwas the main influencing factor of soil phosphorus in the Rhododendron simsii-Larix gmelinii forest and the Rhododendron tomentosum-Larix gmelinii forest, soluble carbon was the main influencing factor of the Carex schmidtii-Larix gmelinii forest, and ammonium nitrogen had a greater influence on the Moss-Larix gmelinii forest. [Conclusion] Understory vegetation had a significant effect on soil phosphorus morphological form and phosphorus availability in Larix gmelinii forest. The content of active phosphorus, medium active phosphorus and available phosphorus in the soil of Rhododendron simsii-Larix gmelinii forest and Rhododendron tomentosum-Larix gmelinii forest was higher, and the activation coefficients of P were all above 2.00%; However, the content of stable phosphorus in soil of the Carex schmidtii-Larix gmelinii forest was higher, and the availability of soil phosphorus was lower. This results are of great significance for the study of ecological function of understory vegetation and soil nutrient cycle in the cold temperate forest ecosystem.

    • Comparison of Different Two-Step Models of Three-Dimensional Mapping Approaches for Soil Organic Carbon Prediction in Hilly Woodlands

      2024, 38(2):351-363. DOI: 10.13870/j.cnki.stbcxb.2024.02.037

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      Abstract:[Objective] In order to investigate the influencing factors and variation rules of accuracy of various two-step models of 3D mapping methods. [Methods] Soil organic carbon in a forest with an area of about 5 km2 in a typical hilly region of South China was mapped. Spline functions, exponential functions and power functions were used as depth functions, ordinary kriging and random forest were used as horizontal mapping methods and two different mapping forms (called forms A and B) were used. The 3D prediction mapping of soil organic carbon was carried out, and the influence of different depth functions, horizontal mapping methods and mapping forms on the 3D mapping results of two-step model was explored. [Results] (1) The depth function largely determined the variation of mapping results in vertical and horizontal directions, which showed that the variation of the mapping results was significantly different among the three depth functions. Exponential function had the largest variation and power function had the weakest variation, while horizontal mapping methods (ie.ordinary kriging and random forest) had little influence on the vertical variation of mapping results. However, the spatial variation of surface layer was greatly affected by the horizontal mapping methods. (2) The accuracy of spline function was the best because the simulated depth curve was in the best agreement with the measured values. The consistency correlation coefficients (CCC) of the 3D mapping based on the spline function were 0.72 and 0.75, which were higher than the other functions in the same form of 3D mapping (CCC were between 0.64 and 0.74). For the horizontal mapping methods, the accuracy of the ordinary kriging was better than that of the random forest, the CCC of the former was between 0.67 and 0.75, the latter was between 0.64 and 0.72; (3) The two mapping forms of the two-step model had little influence on accuracy. Only in the case of prediction for bottom layer, form A (i.e., horizontally mapping simulated walues of a depth function was better than form B (i.e., simulating parameters of a depth function).(4) Among all 3D mapping methods, the form A, with ordinary kriging and spline functions, had the highest accuracy, generating coefficient of determination (R2) of 0.76, CCC of 0.75, and root mean square error (RMSE) of 3.50 g/kg. [Conclusion] In the two-step model of 3D soil mapping, firstly, the spline function should be considered as the depth function. Secondly, the horizontal mapping method should be considered according to the landscape conditions and sample size. Finally, the first mapping form of the two-step model should be adopted as far as possible.

    • Soil Water Infiltration of Artificial Platycladus orientalis of Nanshan Mountain inLanzhou Under Different Rainfall and Rainfall Intensity

      2024, 38(2):364-376. DOI: 10.13870/j.cnki.stbcxb.2024.02.039

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      Abstract:[Objective] Precipitation is the main source of soil water in arid and semi-arid regions. By combining field observation and model simulation to study the regularity of rainfall infiltration, the soil water deficit can be mastered more systematically. [Methods] Through fixed point observation, the Hydrus-1d model was applied to simulate the dynamic change of soil water in Platycladus orientalis on the artificial of Nanshan Mountain in Lanzhou, evaluate the applicability of the model in arid region, and analyze the soil water response and infiltration mechanism under different rainfall conditions. [Results] The Hydrus-1d model had good applicability in the artificial side of Nanshan in Lanzhou, and the deep simulation effect was better. When the rainfall was less than 30 mm, the soil moisture content at 10 cm has the strongest response to rainfall, while the influence of rainfall at 30 and 50 cm was relatively small and had an obvious lag, and there was no response below 70 cm. There was a wetness peak when the rainfall was more than 8.2 mm. During the simulation period, the maximum infiltration depth was 70 cm and the maximum infiltration volume was 23.7 mm. The infiltration depth increased with time, while the infiltration volume and infiltration rate decreased with time. Rainfall was positively correlated with infiltration volume, infiltration depth and infiltration rate (p<0.05). When the rainfall was less than 20 mm, the rainfall intensity had a significant effect on the infiltration amount, infiltration depth and infiltration rate. [Conclusion] The Hydrus-1d model can be used to simulate the dynamic change of soil water in Platycladus orientalis on the artificial of Nanshan in Lanzhou and calculate the infiltration amount, infiltration rate and infiltration depth. Moreover, it is found that the rainfall has a more significant effect on the soil water infiltration process.

    • Effects of Nitrogen and Phosphorus Additions on Aggregate-associated Soil Carbon and Interactions with Phosphorus Fractions in Evergreen Broad-leaved Forest

      2024, 38(2):377-386. DOI: 10.13870/j.cnki.stbcxb.2024.02.023

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      Abstract:[Objective] To explore how phosphorus input regulates the effects of atmospheric nitrogen deposition on soil aggregate organic carbon content and the relationship between carbon and phosphorus. [Methods] A long-term monitoring test platform for nutrient addition was established in evergreen broad-leaved forest soil for 6 years (2015—2021), including 4 treatments: Control [P0+N0, P 0 kg/(hm2·a)+N 0 kg/(hm2·a)], nitrogen addition [P0+N100, P 0 kg/(hm2·a)+N 100 kg/(hm2·a)], phosphorus input [P50+N0, P 50 kg/(hm2·a)+N 0 kg/(hm2·a)] and nitrogen and phosphorus were simultaneously input (P50+N100, P 50 kg/(hm2·a)+N 100 kg/(hm2·a)\], and each treatment was repeated 3 times, and a total of 12 plots were obtained. 0—10 cm soil samples were collected from the sample site in August 2021 to determine the basic physical and chemical properties, soil particle size distribution, phosphorus components of soil aggregates of different particle sizes, and organic carbon (SOC) content. [Results] (1) Under P0 treatment, nitrogen addition significantly increased the proportion of large aggregates, decreased the clay and powder contents, and increased the SOC content in each aggregate particle size. Nitrogen addition significantly decreased and increased the content of labile phosphorus (LP) and residual phosphorus (RP) in aggregate clay and powder, respectively. (2) Under P50 treatment, nitrogen addition significantly increased the geometric mean diameter (GMD) of soil aggregates, but had no significant effects on phosphorus components and SOC contents in aggregates of different particle sizes. (3) Under P0 treatment, soil aggregate SOC was positively correlated with refractory phosphorus. There was no significant correlation between SOC of soil aggregates and functional phosphorus components under P50 treatment. It was concluded that under P0 treatment, nitrogen addition could increase soil organic carbon retention by increasing the refractory phosphorus in soil aggregate clay and powder particle size of evergreen broad-leaved forest. Under P50 treatment, the effect of nitrogen addition on organic carbon in each particle size may be regulated by biological factors and has nothing to do with the availability of phosphorus. [Conclusion] The effect of nitrogen deposition on the internal relationship of carbon and phosphorus in soil aggregates in evergreen broad-leaved forests was regulated by phosphorus. The results of this study provide data supported for forest soil carbon cycling in response to global climate change.

    • Effects of Mushroom Residue Organic Fertilizer Combined with Desulfurized Gypsum on Active Organic Carbon and Its Sensitivity in Saline-Alkali Soil of the Yellow River Delta

      2024, 38(2):387-397. DOI: 10.13870/j.cnki.stbcxb.2024.02.021

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      Abstract:[Objective] In order to investigate the effects of mushroom residue organic fertilizer and desulfurized gypsum on organic carbon components and carbon pool management index (CPMI) of saline-alkali soil. [Methods] The newly reclaimed wheat-maize rotation land in the Yellow River Delta was used as the research subject, and the randomized block experiment method was conducted to set up four treatments: no fertilization (CK), conventional farming fertilization (CN), mushroom residue organic fertilizer (MCOF), mushroom residue organic fertilizer and desulfurized gypsum (MCOG), which were treated by field fertilization for 3 years. [Results] The combined application of mushroom residue organic fertilizer and desulfurized gypsum significantly reduced the salinity of 0—20 cm soil layer, and increased the soil nitrogen, phosphorus and potassium nutrition content and cation exchange capacity (p<0.05). The contents of total organic carbon (TOC), easily oxidized organic carbon (EOC) and microbial biomass carbon (MBC) in 0—20 cm soil layer were higher than those in 20—40 cm soil layer, while the water-soluble organic carbon (WSOC) was lower than that in 20—40 cm soil layer. In the 0—20 cm soil layer, compared with the CN treatment, the MCOG treatment significantly increased soil TOC, EOC, WSOC, and MBC by 15.48%, 23.50%, 18.98%, and 51.40%, respectively. The effective rates of EOC and MBC increased by 13.94% and 30.49%, respectively. There was no significant effect on the effective rate of WSOC. The combined applicationof organic fertilizer and desulfurized gypsum significantly increased the soil CPMI, which increased by 15.38% and 20.00% compared with the CN and the CK treatments, respectively. The sensitivity index of MBC was higher than that of other organic carbon components, and the MBC value of MCOG treatment was the highest. Correlation analysis showed that soil TOC content depended on its active components, while the main factors affecting the content and effective efficiency of organic carbon active components, as well as the CPMI, are pH, CEC, and EC. [Conclusion] Therefore, the combined application of mushroom residue organic fertilizer and desulfurized gypsum can significantly decrease soil alkalinity, improve soil fertility and enhance carbon sequestration efficiency of saline-alkali soil. This research provides a theoretical basis and data support for expanding organic improvement methods in saline-alkali soil of the Yellow River Delta.

    • Effect of Plastic Film Residue on Soil Nitrogen Emissions and Nitrogen Use Efficiency

      2024, 38(2):398-405. DOI: 10.13870/j.cnki.stbcxb.2024.02.009

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      Abstract:[Objective] The aim of this study is to investigate the effects of different residue amounts on nitrogen utilization efficiency and losses. [Methods] The experiment involved five different residue amounts (0, 180, 360, 720, 1 440 kg/hm2) and two types of residues (polyethylene and biodegradable residues). Through pot experiments, the study examined the impact of different residue contents on soil total nitrogen, nitrogen gas losses, nitrogen fertilizer utilization efficiency, and tomato growth indicators. [Results] The research indicates that with an increase in residue content, the cumulative emissions of ammonia and nitrous oxide in the soil show a trend of first increasing and then decreasing. When the residue content reaches 720 kg/hm2, the cumulative ammonia emission significantly decreases by 11.31% to 13.70%, and nitrous oxide emission decreases by 4.74% to 5.13%. There was no significant difference in nitrogen residue in the soil. When the residue content is below 180 kg/hm2, the residue promotes tomato growth; when the residue content is above 180 kg/hm2, it inhibits tomato growth. Low residue content has no significant effect on nitrogen fertilizer utilization efficiency. However, when the content is higher than 360 kg/hm2, nitrogen fertilizer utilization efficiency shows a negative correlation with residue content. Through comprehensive analysis, it is suggested that soil residue content should be controlled within 180 kg/hm2 to avoid negative effects on crop growth. Furthermore, due to the degradable nature of biodegradable residues, their adverse effects on nitrogen absorption by plants and nitrogen fertilizer utilization efficiency are weaker than those of polyethylene residues. [Conclusion] Therefore, replacing polyethylene residues with biodegradable residues is considered feasible.

    • Effects of Different Thickness of Degradable Plastic Film on the Loss of Dissolved Nitrogen and Phosphorus in Sloping Farmland

      2024, 38(2):406-413. DOI: 10.13870/j.cnki.stbcxb.2024.02.010

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      Abstract:[Objective] To explore the effects of degradable mulch film mulching on runoff and loss of dissolved nitrogen and phosphorus. [Methods] Polyethylene film mulching (PF) with a thickness of 0.003 mm, degradable film mulching with a thickness of 0.006 mm (BF1), 0.008 mm (BF2), 0.010 mm (BF3) and 0.012 mm (BF4), and no mulch (CK) were set up. In in-situ runoff plots, using mulching on ridge tillage peanut planting as the study object, the runoff and concentration of ammonium nitrogen (NH4+—N), nitrate nitrogen (NO3-—N), and available phosphorus (PO43-—P) in runoff under natural rainfall conditions were measured, and the runoff and nutrient loss characteristics under different thickness of degradable mulch film were analyzed. [Results] (1) The degradation time of degradable film increased with the increase of film thickness. (2) The order of cumulative runoff was BF1<BF2<BF3<PF<CK<BF4, and there was significant difference between BF1 and BF4 (p<0.05). (3) Compared with CK, different film mulching can reduce the cumulative loss of nitrogen and phosphorus to varying degrees. BF1 had the most significant effect on reducing the loss of NH4+-N and NO3-—N, while BF2 had the most significant effect on reducing the loss of PO43-—P. (4) Among the five laminating treatments, the NO3-—N and PO43-—P loss in BF4 treatment was the highest, while the NH4+-N loss in BF3 treatment was the highest. [Conclusion] The research results can provide a theoretical basis for the prevention and control of water, soil, and nutrient loss in sloping farmland mulching with plastic film and solving the problems of agricultural non-point source pollution, and have important significance for green agricultural development and ecological sustainable development.

    • Effects of Soil Salt Stress on Phosphorus Utilization of Alfalfa

      2024, 38(2):414-422. DOI: 10.13870/j.cnki.stbcxb.2024.02.040

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      Abstract:[Objective] In order to explore the effects of soil phosphorus (P) fertilizer and salt and their interaction on the plant growth, P nutrition and salt tolerance of alfalfa (Medicago sativa). [Methods] Alfalfa "Gannon Ⅶ" was planted by adding phosphate fertilizer (0, 40, 80, 160 mg/kg, in the form of KH2PO4) and NaCl (0, 0.4, 0.8, 1.6 g/kg) with different concentration gradients to the loess soil. [Results] The aboveground and underground biomass of alfalfa increased with the increase of P application level, but decreased with the increase of NaCl addition level. When P was added, P uptake by plants increased. When P was added at 160 mg/kg, P concentrations in roots, stems, and leaves all reached the maximum. However, the addition of salinity inhibited the absorption of P. When NaCl was added at 1.6 g/kg, P concentrations in roots, stems, and leaves all significantly decreased, when compared with that without NaCl. The content of tartrate in rhizosphere of alfalfa decreased with the increase of P compared with that without P, and the addition of exogenous salt significantly increased the content of tartrate in rhizosphere. The rhizosphere soil pH of most treatments was lower than that of non-rhizosphere pH, the decrease of soil pH under salt stress might increase the availability of soil P and P uptake by plants. A high-dose (160 mg/kg) of P significantly reduced the P-uptake efficiency of P-utilization efficiency of alfalfa. [Conclusion] In summary, there was a significant interaction between soil P fertilization and salinity, and the increase in salinity exacerbated plant P deficiency. Appropriate application of P-fertilizers can improve the salt tolerance of alfalfa and enhance its productivity in saline soils.

    • Effects of Irrigation Water Salt Compositions on Tomato Growth and Soil Salinization

      2024, 38(2):423-436. DOI: 10.13870/j.cnki.stbcxb.2024.02.036

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      Abstract:[Objective] To explore the optimal salt composition and salt concentration of irrigation water suitable for tomato field cultivation in arid and semi-arid areas. [Methods] Three salinity levels (1, 2, and 3 g/L) and five Na∶Ca molar concentration ratio levels (1, 3, 5, 7, and 9) of irrigation water were used in a 3-year field experiment of drip irrigation under tomato film in Yinbei irrigation district of Ningxia, China. [Results] The experiment found that with lower irrigation water salinity (1 g/L), appropriate increases in the Na∶Ca molar ratio of irrigation water were beneficial for the accumulation of tomato plant dry matter and nutrients. Tomato fruit weight, marketable yield, and total yield decreased linearly with the increase of irrigation water Na∶Ca molar ratios. Moreover, with each increase in Na∶Ca molar ratio of irrigation water, the tomato marketable yield decreased by 5 761.7 to 6 036.7 kg/hm2. Irrigation water with "high salinity (2, 3 g/L) and low Na∶Ca molar ratio (1 and 3)" was more profitable for tomato yield increase than irrigation water with "low salinity and high Na∶Ca molar ratio". The soil sodium adsorption ratio in 0—40 cm and the amount of soil salt accumulation in 0—100 cm increased linearly with the increase of irrigation water Na∶Ca molar ratio. [Conclusion] To alleviate the soil salt accumulation and obtain a relatively high fruit yield during the growth period of field cultivated tomatoes in Yinbei irrigation area of Ningxia, irrigation water with salinity of 2 g/L and Na∶Ca molar concentration ratio of 5 was recommended for mulched drip irrigation, under the control limit of soil matrix potential at -20 kPa.