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Clipping management, which alters vegetation conditions by removing aboveground vegetation while preserving the underground root system, directly impacts hydrological processes and flow dynamics, ultimately affecting soil erosion processes. This study conducted field experiments (2 × 6 m) encompassing four clipping intensities (with vegetation coverage of 70%, 50%, 25%, and 0%), three rainfall intensities (60, 90, and 120 mm·h−1), and three slope gradients (10°, 20°, and 30°). The results showed that clipping treatments significantly reduced the Darcy–Weisbach resistance coefficient (f). Elevated levels of clipping intensity, rainfall intensity, and slope gradient led to increased flow velocity (v), Reynolds number (Re), and stream power (ω). The shear stress (τ) exhibited an upward trend with rising slope and rainfall intensity, with no significant difference in the effect of clipping intensity. Variation partitioning analysis demonstrated that the influence of steep slopes amplified the effects of rainfall intensity while diminishing the impact of clipping intensity on v values. Critically, the Bayesian network model suggested that, in comparison to the influence of raindrop splashing, soil detachment and transportation by runoff were the predominant driving mechanisms for erosion on slopes with clipped vegetation. Rainfall intensity and clipping intensity were found to raise the runoff depth and enhance the v value, which ultimately influenced soil erosion. Overall, these results contribute to an improved comprehension of the hydraulic dynamics of soil erosion on slopes with clipped vegetation and provide invaluable perspectives for developing effective clipping management strategies to ensure sustainable land utilization and judicious water resource governance. [ABSTRACT FROM AUTHOR]

Sheet erosion has been the major erosion process on steep grassland since the Grain-for-Green project was implemented in 1999 in the Loess Plateau with serious soil erosion in China. Quantifying sheet erosion rate on steep grassland could provide scientific support for effectively controlling soil erosion and rationally managing grassland. Simulated rainfall experiments were conducted on grassland plot with vegetation coverage of 40% under complete combination of rainfall intensities of 0.7, 1.0, 1.5, 2.0 and 2.5 mm min−1 and slope gradients of 7°, 10°, 15°, 20° and 25°. Results showed that sheet erosion rate, varying from 0.0048 to 0.0578 kg m−2 min−1, was well described by binary power function equation (SE = 0.0026 I1.306S0.662) containing rainfall intensity and slope gradient with R2 = 0.940. The logarithmic equation of shear stress (SE = 0.084 + Ln (τ)) and the power function equation of stream power (SE = 1.141 ɷ1.073) could be used to predict sheet erosion rate. Stream power (R2 = 0.903) was a better predictor of sheet erosion than shear stress (R2 = 0.882). The stream power was an excellent hydrodynamic parameter for predicting sheet erosion rate. The study results can reveal the mechanism of sheet erosion process. [ABSTRACT FROM AUTHOR]

Highlights • Another method was provided to determine T c of raindrop-impacted interrill flow. • T c can be calculated using power function equation of slope gradient and rainfall intensity. • Stream power together with rainfall kinetic energy can best describe T c. Abstract Interrill erosion processes typically involve such scientific issues as detachment-limited and transport-limited erosion behaviour. An accurate estimation of the sediment transport capacity ( T c ) by raindrop-impacted overland flow is critical for interrill erosion modelling and for evaluating sediment budgets under erosion-limiting conditions. Simulated rainfall experiments with rainfall intensities from 0.8 to 2.5 mm min−1 over a three-area soil pan with slope gradients from 12.7% to 46.6% were conducted to identify the transport-limited cases and determine T c by raindrop-impacted overland flow within the transport-limited systems of interrill erosion processes. Results indicated that T c increased as a power function of rainfall intensity and slope gradient ( R2 = 0.84, NSE = 0.75), and T c was more sensitive to rainfall intensity than to slope gradient. In terms of R2 and NSE , stream power was the key hydraulic parameter that influenced T c among flow velocity ( R2 = 0.64, NSE = 0.39), shear stress ( R2 = 0.53, NSE = 0.23), stream power ( R2 = 0.76, NSE = 0.52) and unit stream power ( R2 = 0.49, NSE = 0.16). The addition of rainfall physical parameters in response equations of T c in addition to hydraulic parameter, could improve an accuracy of T c modelling. Stream power combined with rainfall kinetic energy can best describe the T c of raindrop-impacted overland flow within the transport-limited system of interrill erosion processes by a power-exponent function ( R2 = 0.90, NSE = 0.72). Rainfall kinetic energy can reduce the Darcy-Weisbach resistance coefficient of raindrop-impacted overland flow and thus benefit sediment transporting. This study provides another method for directly identifying the T c of raindrop-impacted overland flow in interrill erosion processes on steep loess slopes, and points out that rainfall impacts should be particularly considered when studying T c by raindrop-impacted overland flow. [ABSTRACT FROM AUTHOR]

• Soil detachment rate by sediment-laden rill flow decreased with the sediment load. • Flow discharge made the greatest contribution to D r , followed by slope gradient and sediment load. • Taguchi method can effectively minimize the number of tests and ensure low relative error. • Taguchi method could replace full-factorial design in the indoor flume experiments of soil erosion. Soil detachment by rill flow is a key sub-process of rill erosion on hillslope areas; however, many studies have focused on soil detachment by clear rather than by sediment-laden rill flow and most studies have used the time- and labor-consuming full-factorial design. This study used three experimental design methods, including the full-factorial design, orthogonal design, and Taguchi method for indoor flume experiments to explore the process of soil detachment by sediment-laden rill flow. We analyzed and quantified the effects of the slope, flow discharge, and sediment load on the soil detachment rate by sediment-laden rill flow, and compared the results of the three experimental design methods to evaluate the applicability of the orthogonal design and Taguchi method in indoor flume experiments. The results showed that the flow discharge and slope were positively correlated with the soil detachment rate, while the sediment load was negatively correlated with it. The main effects of slope, flow discharge, and sediment load on the soil detachment rate, which were obtained from the three methods, had the same trends. The contribution rates of the flow discharge, slope, and sediment load were 46.20–47.83, 34.42–40.88, and 7.45–12.87%, respectively. The contribution rates of each factor obtained from the three methods were slightly different, but the overall ranked order was the same. The Taguchi method and the orthogonal design can effectively reduce the number of tests and ensure low relative errors. The prediction of the soil detachment rate from the Taguchi method was closer to the full-factorial design than the orthogonal design. Therefore, the Taguchi method proved was most efficient for flume experiments on soil detachment processes by the sediment-laden rill flow. [ABSTRACT FROM AUTHOR]

• Soil detachment capacity by rill flow of SM sandy loess was the largest of the five soils. • D c decreased with soil cohesion and effective silt content. • D c increased with effective median particle size and effective sand content. • D c could be modeled by stream power, soil cohesion and effective median particle size. The loess region of China is one of the most heavily eroded areas in the world. Soil detachment capacity by rill flow (D c) is a key parameter for quantifying intensity of rill erosion in many process-based erosion models. However, only a limited number of studies have been devoted to soil detachment capacity for the various types of loess soil such as is found on the Loess Plateau, where there is variation from south to north and in terms of soil particle size composition. The objectives of this study were (1) to discriminate differences in soil detachment capacity by rill flow (D c) among five loess soils, (2) to investigate the relationship between D c and hydrodynamic parameters, and the relationship between D c and soil properties, and (3) to establish an equation to model soil detachment capacity by rill flow for the loess region. Soil detachment capacity by rill flow for five typical loess soils found on the Loess Plateau of China was investigated through a flume experiment by varying five flow discharges and five slope gradients. The results show that D c of SM sandy loess is the largest with a mean of 2.2145 kg m−2 s−1, followed by YL clay loess, DB sandy loess, AS loess, and CW loess. Stream power is the best hydrodynamic parameter to describe the dynamic process of soil detachment capacity by rill flow for these five loess soils. Soil detachment capacity by rill flow was negatively correlated with soil cohesion and effective silt content (P < 0.05), while it was positively correlated with effective median soil particle size (P < 0.01) and effective sand content (P < 0.05). Soil detachment capacity by rill flow for various hydraulic and soil conditions in the loess region could be modeled using a quaternary power function of slope gradient, flow discharge, soil cohesion and effective median particle size (NSE = 0.96), or it could be modeled by a ternary power function which calculates the variation of soil detachment capacity with stream power, soil cohesion and effective median size (NSE = 0.96). The results of this study reveal the mechanism of soil detachment by rill flow and advance development of a physically-based rill erosion model. Future research should focus on the impact of effective particle size on D c to ensure a full understanding of soil erosion processes. [ABSTRACT FROM AUTHOR]

Understanding sheet erosion processes and improving estimates of soil erosion on biological soil crustal (biocrustal) slopes requires a deep understanding of the factors influencing sheet erosion and its detachment- and transport-limited processes. Simulated rainfall experiments were conducted on plots of biocrust to simultaneously measure the rates of splash detachment and sheet erosion with 0%, 20%, 40%, 50%, 60%, and 80% of coverage at 90 mm h−1 rainfall intensity and 15° slope. The splash detachment rate decreased rapidly during the first 5 min of rainfall and stabilised as rainfall continued, while the sheet erosion rate increased gradually and eventually became relatively stable. The rates of splash detachment and sheet erosion decreased substantially as biocrusts coverage increased and average values of them can be effectively weakened when biocrusts coverage increased from 20% to 40%. Transport-limited processes, dynamic equilibria between detachment- and transport-limited processes, and detachment-limited processes all occurred on biocrustal slope within the same rainfall event. The mean duration of transport-limited processes was longer (16.3 min vs. 9.1 min) when bare slopes were covered by biocrusts, and the latest change in the time from transport-limited to detachment-limited processes appeared at 40% biocrusts coverage. The existence of biocrusts could effectively affect the sheet erosion and its detachment- and transport-limited processes, especially when the coverage was close to 40%. These results can improve our understanding of impacts of biocrusts on sheet erosion processes, and aid an effective way of reducing sheet erosion in arid and semiarid regions. • The effects of biocrusts on sheet erosion were explored. • Detachment- and transport-limited processes occurred on biocrustal slope. • Increasing biocrusts coverage reduced rates of splash detachment and sheet erosion. • Biocrusts with a cover close to 40% effectively affected sheet erosion processes. [ABSTRACT FROM AUTHOR]

• Raindrop detachment capacity is lower in biocrust plot than in bare soil plot. • High biocrust cover or small rain intensity lower raindrop detachment capacity. • Moss-dominated biocrust directly protect soil in cover area from raindrop impact. • Biocrusts indirectly weaken raindrop impact on bare soil by increasing flow depth. • 40% moss-dominated biocrust cover effectIVely weaken raindrop detachment capacity. Biocrusts play a critical role in prevention of erosion, but little is known on the relationship between biocrust cover and raindrop detachment capacity at the slope scale. Evaluating the raindrop detachment capacity on biocrusted slope is essential for better knowledge of the rainfall-induced erosion of biocrusted slope. Thus, laboratory simulated rainfall experiments were conducted on plots (140 × 120 cm) representing moss-dominated biocrusted slopes to measure the amounts of raindrop detachment under a complete combination of different biocrust cover (0%, 20%, 40%, 50%, 60%, and 80%) and rainfall intensities (42, 60, 90, 120, and 150 mm h−1) at 26.79% slope gradient with two replications. The results showed that the biocrust cover, rainfall intensity, and their interaction all significantly affected the raindrop detachment modulus (RDm). The RDm in biocrust plot was significantly lower than in bare soil plot under rain events with the same rainfall intensities. The lower biocrust cover or the larger rainfall intensities led to higher RDm. Reduction benefit of raindrop detachment modulus (RB-RDm) were greater than its corresponding biocrust cover values. When the biocrust cover increased from 20% to 40%, the increase range and growth trend of RDm decreased with increasing rainfall intensity. Our results indicated that the development of biocrusts on slope is an effective way of reducing raindrop detachment by protecting soil in their covered area and increasing flow depth. When moss-dominated biocrust cover reached 40%, the raindrop detachment capacity effectively weakened even under rain events with large rainfall intensities. These findings may conducive to offer a scientific guidance for soil erosion control in the Loess Plateau and in other arid and semiarid regions. [ABSTRACT FROM AUTHOR]

Sediment transport is an important aspect of soil erosion, and sediment transport capacity ( T c ) is a key to establishing process-based erosion models. A lot of studies exist that have determined T c for overland flow, however, few studies have been conducted to determine T c for loess sediments on steep slopes. Experimental data for this region are thus needed. The objectives of this study are to formulate new equations to describe T c and evaluate the suitability of these equations for loess sediments on steep slopes. The slope gradients in this study ranged from 10.51% to 38.39%, and flow discharges per unit width varied from 1.11 × 10 − 3 m 2 s − 1 to 3.78 × 10 − 3 m 2 s − 1 . Results showed that T c increased as a power function with flow discharge and slope gradient, with R 2 = 0.99 and Nash–Sutcliffe model efficiency (NSE) = 0.99. T c was more sensitive to flow discharge than slope gradient. T c increased as a power function with mean flow velocity, which was satisfied to predict T c with R 2 = 0.99 and NSE = 0.99. Shear stress (R 2 = 0.89, NSE = 0.88) was also a good predictor of T c , and stream power (R 2 = 0.96, NSE = 0.96) was a better predictor of T c than shear stress. However, unit stream power was not a good predictor to estimate T c in our study, with R 2 = 0.63 and NSE = 0.62. These findings offer a new approach for predicting T c for loess sediments on steep slopes. [ABSTRACT FROM AUTHOR]

As soil ecosystem engineers, ants considerably affect soil physical and chemical properties, and further accordingly affect soil erosion. However, few study was made on studying the effects of ant-burrowing activities on soil erosion previously. This study quantified the impacts of ant (Camponotus japonicus)-burrowing activities on runoff and soil erosion rates. Simulated laboratory rainfall experiments were undertaken on six soil tanks filled with clay-loam soil classified as a cumulic anthrosol, three of which introduced with ant colonies for two days and the other three were without ant colonies, under 40, 80, and 120 mm h−1 of rainfall intensities and a slope of 15°. Results showed that ants made mounds with a bulk density of 0.75 g cm−3, which was lower than that of the soil matrix, i.e. 1.34 g cm−3. Soil erosion rates for the tanks with ants were 6.78, 36.90, and 62.00 g m−2 min−1 under three rainfall intensities of 40, 80, and 120 mm h−1, which were much higher than those of 3.94, 23.49, and 44.48 g m−2 min−1 for the tanks without ants. Ant nests reduced the runoff rate by 31%, 20% and 13% compared with those without ants and enhanced the soil water storage within 90 cm depth. Ant nests played a positive role in soil water conservation due to the large nest entrance diameter and the continuous macropore network. However, the ant mounds provided a loose erodible material and changed micro-topography of the slope surface, thereby accelerating the rill formation and exacerbating soil erosion. This study can help understand the effects of burrowing insects on soil erosion, which is an important environmental problem on the Loess Plateau. • Ant nests reduced the runoff rate and increased soil water storage. • Ant mounds changed the micro-topography and accelerated rill generation. • Ant mounds increased soil erosion rate on bare slopes. [ABSTRACT FROM AUTHOR]

• Temporal changes in splash detachment rate and interrill wash rate were studied. • Erosion-limiting degree was defined and presented. • Erosion-limiting degree increased linearly with increasing slope gradient. Better understanding of raindrop detachment, interrill wash and erosion-limiting degree in interrill processes is critical for accurately modelling interrill erosion and implementing proper anti-erosion strategies. Simulated rainfall experiments were conducted on a clayey loessal soil at three rainfall intensities (42, 60 and 90 mm h−1), five slope gradients (7°, 10°, 15°, 20° and 25°) and rainfall duration of 40 min. Results showed that raindrop detachment rate initially decreased rapidly within a few minutes and then reached a relative steady state during rainfall. The initial and steady raindrop detachment rate increased with increased rainfall intensity. Interrill wash rate peaked early and then decreased to a relative constant rate during the rainfall. The initial, maximum and steady interrill wash rate increased with increased rainfall intensity and slope gradient. Erosion-limiting degree (ELD), defined as the ratio of interrill wash rate to raindrop detachment rate, ranged from 10.99% to 35.70% under experimental conditions, indicating that interrill erosion system was transport-limited. The ELD decreased with rainfall intensity and increased linearly (R 2 = 0.90) with slope gradient. The higher the rainfall intensity, the stronger the transport-limiting in interrill erosion processes; the steeper the slope gradient, the weaker the transport-limiting in interrill erosion processes. Raindrop detachment is the dominant process in detaching soil particles, whereas interrill flow contributes to washing out detached sediments. The findings of this study, especially ELD , largely improved the understanding of interrill erosion processes. [ABSTRACT FROM AUTHOR]

Abstract Splash erosion is recognized as an important process of water erosion on agricultural land, but evaluating and modelling splash detachment capacity on steep slopes using loessial soil were not fully studied. The objectives of this study are: (1) to evaluate the effects of slope gradient (S) and rainfall intensity (I) on splash detachment capacity (SDr), (2) to select the key rainfall physical parameters and hydraulic parameters affecting splash detachment capacity, (3) to establish new and more accurate experimental models between splash detachment capacity (SDr) and these key parameters on steep slopes for loess regions. The experiment was conducted at slopes of 12.23%, 17.63%, 26.8%, 36.4%, 40.4% and 46.63% under rainfall intensities of 48, 60, 90, 120, 138 and 150 mm h−1, respectively, using simulated rainfall. Results showed that the equation between splash detachment capacity (SDr) with both parameters of rainfall intensity (I) and slope gradient (S) (i.e. SDr = 0.000126 ln (0.36 S −0.3 I 1.3 − 14)) could predict SDr well with R2 = 0.85 and Nash–Sutcliffe model efficiency (NSE) = 0.71. SDr was more sensitive to rainfall intensity than to slope gradient. The rainfall kinetic energy (KE) was the key rainfall physical parameter and the mean flow depth (h) was the key hydraulic parameter affecting SDr. The equation between SDr with both parameters of KE and h (i.e. SDr = 0.000164 ln (0.0031 KE 1.13 h −0.3 − 4.5)) could satisfactorily predict SDr with R2 = 0.85 and Nash–Sutcliffe model efficiency (NSE) = 0.81. The new equations (i.e. SDr = 0.000126 ln (0.36 S −0.3 I 1.3 − 14) and SDr = 0.000164 ln (0.0031 KE 1.13 h −0.3 − 4.5)) could help in controlling water erosion in the loess region of China. Highlights • The experiments were conducted under six rainfall intensities and six slope gradients using loessial soil samples. • The key rainfall physical parameter for evaluating splash detachment capacity was revealed. • The key hydraulic parameter for evaluating splash detachment capacity was revealed. • Two reliable equations were derived for predicting splash detachment capacity. [ABSTRACT FROM AUTHOR]

Highlights • Response of soil detachment rate by sheet flow (D s) to sediment load was quantified. • Response of D s to hydraulic parameters were evaluated. • The best hydraulic parameter in relation to D s was identified. Abstract The response of soil detachment rate by raindrop-affected sediment-laden sheet flow to sediment load and hydraulic parameters was investigated within a detachment-limited sheet erosion system on steep slopes to understand sheet erosion processes fully and derive an accurate experimental model. An experiment was conducted at slopes of 12.23%, 17.63%, 26.8%, 36.4%, 40.4% and 46.63% under rainfall intensities of 48, 60, 90, 120, 138 and 150 mm h−1, respectively, by using simulated rainfall. Results showed that the soil detachment rate by raindrop-affected sediment-laden sheet flow decreased as the sediment load by sheet flow increased, and the decrease was a power function of sediment load by sheet flow with NSE = 0.58, MSE = 0.0099 and R 2 = 0.58. In addition, the soil detachment rate by raindrop-affected sediment-laden sheet flow increased as a linear function of shear stress, stream power and unit stream power. Shear stress and stream power could be used to predict the soil detachment rate by raindrop-affected sediment-laden sheet flow accurately through a linear equation. Stream power (R 2 = 0.87, MSE = 0.003 and NSE = 0.87) was a better predictor of soil detachment rate by raindrop-affected sediment-laden sheet flow than shear stress (NSE = 0.83, MSE = 0.004 and R 2 = 0.83). However, prediction based on unit stream power (NSE = 0.43, MSE = 0.01 and R 2 = 0.43) was poor. These findings can improve our understanding and modelling of sheet erosion processes on steep slopes in the loess region of China. [ABSTRACT FROM AUTHOR]

The relationship of sheet erosion rate ( SE ), slope gradient ( S ) and rainfall intensity ( I ), and hydraulic parameters, such as flow velocity ( V ), shear stress ( τ ), stream power ( Ω ) and unit stream power ( P ), was investigated to derive an accurate experimental model. The experiment was conducted at slopes of 12.23%, 17.63%, 26.8%, 36.4%, 40.4% and 46.63% under I of 48, 60, 90, 120, 138 and 150 mm h −1 , respectively, using simulated rainfall. Results showed that sheet erosion rate increased as a power function with rainfall intensity and slope gradient with R 2 = 0.95 and Nash–Sutcliffe model efficiency ( NSE ) = 0.87. Sheet erosion rate was more sensitive to rainfall intensity than to slope gradient. It increased as a power function with flow velocity, which was satisfactory for predicting sheet erosion rate with R 2 = 0.95 and NSE = 0.81. Shear stress and stream power could be used to predict sheet erosion rate accurately with a linear function equation. Stream power ( R 2 = 0.97, NSE = 0.97) was a better predictor of sheet erosion rather than shear stress ( R 2 = 0.90, NSE = 0.89). However, a prediction based on unit stream power was poor. The new equation (i.e. SE = 7.5 × 10 12 S 1.43 I 3.04 and SE = 0.06 Ω - 0.0003 and SE = 0.011 τ - 0.01 ) would improve water erosion estimation on loess hillslopes of China. [ABSTRACT FROM AUTHOR]

• Optimal clipping increases surface runoff and limits soil erosion. • Rainfall intensity and slope magnified the clipping effect on soil loss. • The recommended vegetation cover after clipping is 23% − 48%. • The slope gradient of clipped vegetation should not exceed 36%. Clipping management by reducing the above-ground parts of grassland has been gradually introduced to offset some of the additional issues caused by large-scale vegetation restoration, such as the formation of a dry soil layer, approaching the limits of watershed water resources, and reducing the sustainability of vegetation. Therefore, there is a scientific and practical need to evaluate the effectiveness of clipping management on runoff and erosion processes to ensure a balance between erosion control, surface water supply, and vegetation sustainability. In this study, simulated rainfall experiments with four levels of clipping intensities (no clipping, light clipping, heavy clipping, and clear clipping) were conducted to explore the mechanism of runoff and soil loss response under three rainfall intensities (i.e., 60, 90, and 120 mm·h−1) and three slope gradients (i.e., 18, 36, and 58 %) using structural equation modeling and variation partitioning. The results showed that the runoff depth increased by 42 %, 119 %, and 299 %, respectively, and the soil loss increased by 76 %, 80 %, and 470 %, respectively, in the light, heavy, and clear clipping treatments compared with the no clipping treatment, indicating that the increase in the percentage of runoff production and soil loss was not synchronized. According to the optimizing results of response surface method, the recommended vegetation cover after clipping was 23 % − 48 %, and the slope gradient of clipped vegetation should not exceed 36 %, which increased surface runoff while limiting soil erosion within an acceptable range. Runoff production and soil loss were primarily determined by rainfall intensity, followed by clipping intensity and slope gradient. Increasing rainfall intensity and slope gradient increased the effect of clipping on soil loss. Therefore, local rainfall and topography need to be considered in the application of clipping management. This study provides valuable insights into the use of clipping treatment as a sustainable management strategy for mitigating soil erosion and conserving surface water resources, and has important implications for developing restoration plans to promote sustainability in semi-arid ecosystems. [ABSTRACT FROM AUTHOR]