Freeze-thaw effects on erosion process in loess slope under simulated rainfall

Seasonal freeze–thaw processes have led to severe soil erosion in the middle and high latitudes of the world, so understanding the freeze–thaw erosion process is of great significance for soil and water conservation as well as for ecological engineering. The area affected by freeze–thaw erosion in China exceeds 13% of the national territory. However, there is little data regarding the impact of rainfall intensity and initial thaw depth on soil erosion. Here, the effects that different rainfall intensities (0.6 mm/min, 0.9 mm/min and 1.2 mm/min) and different initial thaw depths (0 cm, 2 cm, 4 cm and 6 cm) had on the soil erosion process on the loess slope were studied under simulated rainfall conditions. The results showed that the infiltration rate decrease with prolonged runoff time, and then stabilized. Runoff occurred more quickly during increasingly intense rainfall, especially when little soil had thawed. The variation in runoff and sediment yield occurred in two stages: slow growth and rapid growth. As soil thawed to greater depths, rainfall intensity had less influence on the sediment. A linear relationship existed between the cumulative runoff and the sediment yield of all treatments. (R2 > 0.92, p < 0.01). Rainfall intensity and thaw depth had interacting effects on erosion. At low rainfall intensities, the initial thaw depth played a leading role in the erosion process, but at higher rainfall intensities, rainfall intensity played a larger role. Stage II erosion amount accounted for more than 90% of the total erosion across all treatments. The results of this research provide a guide for furthering the understanding of the soil water erosion mechanism of thawing slopes.

Soil degradation and erosion in semi-arid regions can significantly impact agricultural development, environmental sustainability, and hydrological balance. Understanding the impacts of land use changes and soil and water conservation (SWC) technique implementation on soil erosion and sediment yield is critical to planning effective watershed management. This study aims to evaluate the impacts of environmental changes in the Merguellil watershed (Central Tunisia) over the last forty years. To achieve this, remote sensing techniques and a geographic information system (GIS) will be employed to classify Landsat images from 1980 to 2020. Additionally, the Revised Universal Soil Loss Equation model will be utilized to estimate soil erosion rates, while the sediment delivery distributed model will be employed for sediment yield modeling. Spatiotemporal changes in land use and land cover and in areas treated with SWC techniques were analyzed as the main factors influencing changes in erosion and sediment yield. The combined impact of land use change and SWC techniques resulted in a decrease in the annual soil erosion rate from 18 to 16 t/ha/year between 1980 and 2020 and in sediment yield from 9.65 to 8.95 t/ha/year for the same period. According to the model’s predictions, both soil erosion and sediment yield will experience a slight increase with further degradation of natural vegetation and a reduction in the efficiency of SWC works. This emphasizes the importance of continued efforts in adopting and sustaining SWC techniques, as well as preserving natural vegetation cover, to proactively combat soil degradation and its adverse effects on the environment and communities. Continuous dedication to these measures is crucial to preserving our ecosystem, promoting sustainable practices, and protecting the well-being of both the environment and society.

Characterizing erosion processes on a convex slope based on 3D reconstruction method

The indoor fine simulated rainfall experiment was conducted to reveal the variation regularity of the rill boundary and the response of the erosion and sediment yield under the fixed slope gradient (20°) and three rainfall intensities (66, 94, 127 mm/h). Results showed that the response of the slope sedimentation process to the rill boundary changes is obvious. Rill traceability is the most active way of determining sediment yield during rill formation and development; it is the main source of sediment in the early stages of rill development. Rill wall collapse and bed cut are the more active ways of sediment yield during rill network development and formation; they directly lead to increase in soil erosion rate in the middle stages of rill development. Rill bed cut is the more active way of sediment yield during rill network adjustment. The change in the relationship between runoff shear and sediment concentration directly leads to the continuous fluctuation of soil erosion rate in the later stage of erosion. The sand production is affected by the development of the rill. There is a correspondence between the rill network at different developmental stages and the sediment yield. The sediment concentration of runoff is relatively low before the formation of the rill, and then fluctuates continuously in the rill development stage and tends to be relatively stable in the stable development stage; while the sediment concentration of runoff is proportional to the rain intensity. This study can provide basic data for the establishment of rill erosion dynamic model.

Surface roughness and slope gradient are two important factors influencing soil erosion. The objective of this study was to investigate the interaction of surface roughness and slope gradient in controlling soil loss from sloping farmland due to water erosion on the Loess Plateau, China. Following the surface features of sloping farmland in the plateau region, we manually prepared rough surfaces using four tillage practices (contour drilling, artificial digging, manual hoeing, and contour plowing), with a smooth surface as the control measure. Five slope gradients (3°, 5°, 10°, 15°, and 20°) and two rainfall intensities (60 and 90 mm/hr) were considered in the artificial rainfall simulation experiment. The results showed that the runoff volume and sediment yield increased with increasing slope gradient under the same tillage treatment. At gentle slope gradients (e.g., 3° and 5°), the increase in surface roughness prevented the runoff and sediment production, that is, the surface roughness reduced the positive effect of slope gradient on the runoff volume and sediment yield to a certain extent. At steep slope gradients, however, the enhancing effect of slope gradient on soil erosion gradually increased and surpassed the reduction effect of surface roughness. This study reveals the existence of a critical slope gradient that influences the interaction of surface roughness and slope gradient in controlling soil erosion on sloping farmland. If the slope gradient is equal to or less than the critical value, an increase in surface roughness would decrease soil erosion. Otherwise, the increase in surface roughness would be ineffective for preventing soil erosion. The critical slope gradient would be smaller under higher rainfall intensity. These findings are helpful for us to understand the process of soil erosion and relevant for supporting soil and water conservation in the Loess Plateau region of China.

Soil erodibility and hillslope erosion processes affected by vegetation restoration duration

1. Soil Erosion by Wind and Water: Problems and Prospects, R. Lal The Need for Improved Data Data Extrapolation Standardization of Methodology and Data Reliability Record Duration and Data Continuity Toward Standardization of Research Methods 2. Laboratory and Field Plots for Erosion Research, C. K. Mutchler, C. E. Murphree, and K. C. McGregor The Project Outline The Soil Erosion Process Small Plots Conclusions 3. Measuring Sediment Yield from River Basins, D. E. Walling Introduction Reliability of Existing Sediment Yield Data Designing Sediment Yield Monitoring Programs Additional Sources of Information on Sediment Yields 4. Rainfall Simulators for Soil Erosion Research, L. D. Meyer Characteristics of Rainfall Simulators Types of Rainfall Simulators Personnel Requirements and Related Equipment Rainfall Simulators: Asset or Burden? 5. The Revised Universal Soil Loss Equation, K. G. Renard, J. M. Laflen, and D. K. McCool R-factor K-factor L- and S-factor C-factor P-factor Comparison of RUSLE and USLE Summary 6. Modeling Soil Erosion, M. A. Nearing, L. J. Lane, and V. L. Lopes Mechanics of Erosion by Water Development of a Physically-Based Erosion Model Model Analysis Modeling on Watershed Scales Integrated Systems for Water Erosion Prediction 7. Research Progress on Soil Erosion Processes and a Basis for Soil Conservation Practices, C. W. Rose Types and Objectives of Soil Erosion Models Basic Approach to Sediment Erosion and Transport Erosion/Deposition Process Model A Simplified Erosion Process Model The Effect of Plot Length on Soil Loss per Unit Area Effect of Surface Contact Cover and Slope on Soil Loss 8. Erodibility and Erosivity, R. Lal and W. Elliot Soil Erosion Process Soil Erodibility Summary 9. Assessing Vegetative Cover and Management Effects, M. A. Stocking How Vegetative Cover and Management Work Key Areas in Crop Cover and Management Research Methodologies 10. Monitoring the Impact of Soil Erosion on Crop Productivity, F. J. Pierce and R. Lal The Need for Erosion-Productivity Research Approaches to the Problem Toward a Minimum Data Set The Erosion-Productivity MDS Model Building and Validation Summary and Conclusions 11. Wind Erosion, E. L. Skidmore Soil Erodibility by Wind Wind Erosivity Ridge Roughness Field Length Vegetative Factor A Wind Erosion Model Management Effects Conclusions 12. Methods for Investigating Basic Processes and Conditions Affecting Wind Erosion, E. L. Skidmore, L. J. Hagen, D. V. Armbrust, A. A. Durar, D. W. Fryrear, K. N. Potter, L. E. Wagner, T. M. Zobeck Wind Databases and Simulation Particle Detachment and Transport Aggregate Stability Dry Aggregate Size Distribution Surface Roughness: Shelter Angle Distribution Surface Roughness: Digitization of Pin Meter Photos Surface Crusting Loose Surface Particles Soil Wetness Canopy Structure Field Scale Wind Erosion Measurement Index

A model of soil erosion and sediment transport on hillslopes is used to illustrate the role of process understanding in determining dominant processes as a function of spatial scale. Erosion and sediment yield from hillslopes are primarily determined by surface runoff, topography, vegetative canopy cover, ground surface cover, soil erodibility, and sediment properties. In areas where winter processes (snow, snowmelt, soil frost, etc.) are important, erosion and sediment yield also determined by these factors. The Hillslope Erosion Model (HEM) incorporates these factors in simulating erosion and sediment yield. The world's largest rainfall simulator database for arid and semiarid areas and data from small hillslope-scale watersheds are used to calibrate and validate the spatially distributed, processed-based HEM. Spatially distributed estimates of sediment transport and yield along hillslopes from the HEM are used with an understanding of dominant processes as a function of spatial scale as the scientific basis to determine stability of slopes at plot to hillslope scales. Interrill processes of raindrop splash and thin sheetflow transport are diffusive. Concentrated flow (rill erosion) processes are advective. Spatial loci of transition from diffusive to advective processes are inherently zones of landscape instability and channel formation. The HEM is used to define these areas of instability on hillslopes. Stability criteria for hillslopes are in turn used as criteria for geomorphic designs. Field data taken on a mine rehabilitation site in Queensland, Australia and at the Yakima Training Center in Washington State were used to extend the erosion model to disturbed site rehabilitation problems. These example applications from natural and designed slopes are used to illustrate model predictions and their applications in scaling and geomorphic designs.

Investigations on temporal and spatial variation of slope-scale SOC erosion and deposition

PDF HTML阅读 XML下载 导出引用 引用提醒 东北黑土区片蚀和沟蚀对土壤团聚体流失的影响 DOI: 10.5846/stxb201303230498 作者: 作者单位: 西北农林科技大学 资源环境学院,西北农林科技大学 资源环境学院,西北农林科技大学 资源环境学院,西北农林科技大学 资源环境学院,西北农林科技大学 资源环境学院,西北农林科技大学 资源环境学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目（41271299，40871137） The impact of sheet and gully erosion on soil aggregate losses in the black soil region of Northeast China Author: Affiliation: College of Resources and Environment,Northwest A＆F University,College of Resources and Environment,Northwest A＆F University; Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources,College of Resources and Environment,Northwest A＆F University,College of Resources and Environment,Northwest A＆F University,College of Resources and Environment,Northwest A＆F University,College of Resources and Environment,Northwest A＆F University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:土壤侵蚀方式的差异必然会导致土壤团聚体破碎程度及流失过程的不同。基于室内模拟降雨试验，对比研究了黑土坡耕地片蚀和沟蚀对土壤团聚体流失的影响。结果表明，在50和100 mm/h降雨强度下，沟蚀试验处理的侵蚀量分别是片蚀试验处理的1.42倍和3.51倍左右。在片蚀试验处理下，当降雨强度由50 mm/h增加至100 mm/h时，侵蚀泥沙中微团聚体（< 0.25 mm）含量由45.7%增加至74.2%；而在沟蚀试验处理下，侵蚀泥沙中以大团聚体（≥0.25 mm）为主，其占团聚体流失量为65.5%。片蚀试验处理下，50 mm/h降雨强度时，侵蚀泥沙中 > 5和2-5 mm粒级的团聚体含量均小于沟蚀处理，而其它粒级的团聚体含量均大于沟蚀处理；在100 mm/h降雨强度下，侵蚀泥沙中团聚体各粒级的含量均小于沟蚀处理。与试验土壤相比，表征团聚体流失的两个特征指标平均重量直径（MWD）和几何平均直径（GMD）均明显减少；在两种降雨强度下，片蚀试验处理的MWD和GMD均明显小于沟蚀处理。研究还发现MWD和GMD两种团聚体指标均能反映黑土农耕地坡面片蚀和沟蚀方式下的团聚体流失特征，且MWD能够更好的反映出雨强变化时两种侵蚀方式下土壤团聚体的流失特征。 Abstract:Different patterns of soil erosion cause differences in soil aggregate breakdown and its loss processes. Previous studies concentrated mainly on the variation in soil aggregates under various land uses and breakdown mechanisms. This paper used simulated rainfall experiments to investigate how sheet and gully erosion affected soil aggregate losses. The tested soil is black soil collected from Yushu city in Jilin Province and the experiment was conducted in the simulated rainfall hall of the Institute of Soil and Water Conservation. The lateral spraying nozzles, whose height was 16 m above the ground, were used in this study. The size of the test soil pan was 8 m long, 3 m wide and 0.6 m deep. The experimental design covered two rainfall intensities of 50 and 100 mm/h, one slope of 10°, and two erosion patterns of sheet and gully, and each treatment had two replications. During the rainfall process, runoff samples were collected and lost aggregates were collected through a set of sieves with different apertures of 5, 2, 1, 0.5 and 0.25 mm in every five minutes. The dry sediment was used to calculate erosion rate and different sizes of dry lost aggregates in the sediments were used to compute aggregate loss. The results showed that under rainfall intensities of 50 and 100 mm/h, the gully erosion rate was almost 1.42 and 3.51 times greater than that of sheet erosion, respectively. When the rainfall intensity increased from 50 to 100 mm/h, the < 0.25 mm micro-aggregates in the sediments from sheet erosion treatment increased from 45% to 74%; while for the gully erosion dominated treatment, the aggregate in the sediments was mainly comprised of ≥0.25 mm of macro-aggregates, which occupied 65.5% of total aggregate loss. Under the rainfall intensity of 50 mm/h, > 5 and 2-5 mm aggregates in the sediments from the sheet erosion treatment were lower than those from the gully erosion dominated treatment; while the other sizes of aggregates in the sediments from the sheet erosion treatment were greater than those from the gully erosion dominated treatment. Under 100 mm/h of rainfall intensity, all sizes of aggregates in the sediments from the gully erosion dominated treatments were greater than those from the sheet erosion treatment. The results also demonstrated that, for the sheet erosion treatment, raindrop impact was the main driving force for aggregate breakdown, while for the gully erosion dominated treatment, concentrated flow detachment, transportation in gully channel and friction function of the different aggregates during transportation processes were the main driving forces for aggregate breakdown. Compared with the test soil, mean weight diameter (MWD) and geometric mean diameter (GMD) of aggregates in the sediments were lower for both treatments of sheet and gully erosion. Under the two rainfall intensities of 50 and 100 mm/h, MWD and GMD in sediments from the sheet erosion treatment were smaller than those from the gully erosion dominated treatment. This paper also proposed that under the experimental conditions, two indicators of MWD and GMD could reflect the lost aggregate characteristics, and MWD could better reflect aggregate variation with an increase in rainfall intensity. 参考文献 相似文献 引证文献

Pulp fibre, a primary type of sludge of pulp and paper mills containing approximately 40% organic C, is usually disposed of in landfills causing a potential environmental problem. This material may be used as a soil amendment to restore the productivity of organic-matter-depleted potato-producing soils in Atlantic Canada. The effect of incorporating this material at rates equivalent to 0.5, 1.0, 2.0, and 4.0% organic matter in the plow layer of a gravelly loam soil on selected soil physical properties and soil erosion was evaluated. The objectives were to determine the effect of pulp fibre additions on selected soil properties, which are pertinent to water retention and movement and to evaluate its effectiveness in reducing runoff and soil loss, major contributing processes to soil degradation . Chemical analysis of pulp fibre revealed that all heavy metal concentrations were well below allowable concentrations for Category A compost. One year after incorporation, bulk density of the Ap horizon had decreased with increasing rates of organic matter addition. On the other hand, the saturated hydraulic conductivity and specific moisture content increased with increasing rates of treatments. Results on water-stable aggregates revealed that the organic matter in the pulp fibre combined smaller aggregates to form larger aggregates, resulting in a larger proportion of macropores as compared to micropores. In the 4% organic matter treatment, a 27% increase was found in the 1.0 to 5.0 mm-diameter aggregates whereas a 23% reduction was found in aggregates smaller than 1.0 mm diameter. In spite of the higher specific moisture content of the organic-matter-treated soils, soil moisture content measured immediately prior to the erosion test indicated that field soil moisture contents were lower than those of the control. Time of runoff initiation, rates of runoff and soil loss were greatly improved with the amendments. The beneficial effects of the 4% organic matter treatment include 2.1 times delay in runoff initiation, and 23 and 71% reduction in runoff and soil loss, respectively. Although the beneficial effects in soil and water conservation are apparent, a minor drawback appears to be lower field soil moisture content. Large-scale implementation of the addition of this material in potato fields should proceed only with caution. Key words: Saturated hydraulic conductivity, moisture retention, water stable aggregate, mean weight diameter, sediment yield, soil amendment

Introduction to the special issue ‘Tracer Applications in Sediment Research’

Rainfall intensity, slope length, and slope gradient are the important factors affecting runoff and sediment yield. In order to quantitatively analyze the effects of rainfall intensity, slope length, and slope gradient on the erosion process of Ansai loess slope in loess hilly and gully region, we analyzed the variation of runoff and sediment yield on Ansai loess with two slope lengths (5, 10 m), three slopes (5°, 10°, 15°) and two rainfall intensities (60, 90 mm·h-1) in an indoor simulated rainfall experiment. The results showed that the initial runoff generation time decreased with the increases of slope length, though the overall change was not significant. The initial runoff generation time decreased with the increases of rainfall intensity. Compared with the intensity of 60 mm·h-1, the initial runoff generation time decreased by 5.7-18 min under the intensity of 90 mm·h-1. Among them, the runoff initiation time on the slope of 10° was the fastest. With the duration of rainfall, runoff yield rate increased rapidly at first, and then gradually fluctuated around a certain value. The sediment yield rate increased rapidly in a short period of time at the initial stage of runoff generation, and then decreased after reaching the maximum, and being gradua-lly stable. The rates of runoff and sediment yield increased with the increases of slope length and rainfall intensity, but the law of change with slope was not obvious. With the increases of rainfall intensity, slope length and gradient, the total sediment yield increased accordingly. Under the rainfall intensity of 90 mm·h-1, the slope surface with the length of 10 m and slope of 15° generated rill, leading to the highest total erosion amount (11885.66 g). Under the rainfall intensity of 60 mm·h-1, the erosion amount per unit area decreased with the increases of slope length, and there was a critical erosion slope length in 5-10 m slope section. Slope length, slope and rainfall intensity all played a promoting role in runoff process. Rainfall intensity, slope length, and their interaction contributed more to runoff yield rate and total erosion amount. Rainfall intensity contributed the most to runoff yield rate, with a contribution rate of 49.8%. The contribution rate of slope length to the total erosion was the largest, which reached 37.8%.

Assessment of soil erosion change and its relationships with land use/cover change in China from the end of the 1980s to 2010

Long-term monitoring of soil bulk density and erosion rates in two Prunus Persica (L) plantations under flood irrigation and glyphosate herbicide treatment in La Ribera district, Spain