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[Objective] The impact of soil erosion on nutrient content and stoichiometric ratios in soil is crucial for further comprehending and effective control of quality degradation in the sloping farmlands of black soil regions. [Methods] Selecting straight slopes cultivated for over a century and a convex slope cultivated for more than five decades in the typical black soil area of Keshan County as the research objects, utilizing 137Cs tracing method to estimate soil erosion rates on the slopes. Quantitative analysis was conducted on the relationship between soil erosion and key parameters such as soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) contents, along with the stoichiometric ratio in the ecological chemistry. [Results] (1) Using 137Cs tracing technique, the average annual erosion rate of the whole slope was 4 428.56 t/(km2·a), the average erosion rates of the linear and convex slopes were 3 284.53, 5 884.59 t/(km2·a), and the total erosion volumes were calculated at 3.21×105, 2.94×105 t/km2, respectively. (2) The overall carbon/nitrogen ratio (C/N) on the slopes showed a highly significant positive correlation with SOC (p0.05). [Conclusion] Ultimately, soil erosion redistributed SOC, TN and TP on the slopes, affecting the stoichiometric ratios of soil nutrients and leading to substantial nutrient loss on the slopes.

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]

Aims: With the wide application of 7Be (Beryllium-7) in soil erosion investigations, retention and interception of 7Be by vegetation plays an important role in documenting soil 7Be redistribution, with a large impact on the interpretation of 7Be measurements. However, the dynamic and temporal changes in plants and the relationship with soil 7Be concentration remain unclear, and the significance of dead plants in 7Be interception is under-researched. Methods: The samples of single plants (6 different species), compositive plants (including living and dead plants), along with soil reference on the Loess Plateau were collected individually to analyze the variations of 7Be concentration during the growth period from 2010 to 2012. Results: The accumulation of 7Be per mass is significantly higher in leaves than stems. The 7Be activity per mass and per area in living plants with seasonal trends ranged from 173.9 to 703.1 Bq kg–1 and 21.5 to 190.1 Bq m–2, respectively, and in dead plants ranged from 381.8 to 964.5 Bq kg–1 and 30.4 to 285.7 Bq m–2. Precipitation accounted for the largest contribution to the accumulation of 7Be in plants, followed by plant growth, species and parts. Plants accounted for 7Be interception on slope up to 66% (living plants accounted for 7% ~ 31% and dead plants accounted for 6% ~ 44%). The interception of living plants is low at first, then increases with the accumulation of rainfall and biomass together. Conclusions: Our results highlight that 7Be in plants (especially for the dead plants) is of great significance for 7Be in soil on the slope, and is controlled by precipitation, growth status and plant characteristics. The reference information obtained in this work will contribute to improving the accuracy of 7Be tracing technology, and broadening its scope. [ABSTRACT FROM AUTHOR]

Biochar addition to soil has increasingly demonstrated the potential to improve soil and mitigate climate change. However, the effects of biochar additions for sloping cropland amendments and soil erosion remain unclear. In this study, experiments with simulated rainfall (25, 50, 75, and 100 mm hr‐1) were conducted on a soil box (0.45‐m length × 0.3‐m width) to assess the effects of different biochar addition rates (2%, 5%, and 8% [wt/wt]) and incubation time (i.e., 140 days) on runoff, soil loss, and interrill erodibility. The soil and biochar were loess‐derived Miami soil and commercial charcoal made from seasoned oak and hickory hardwoods, respectively. Compared with the control soil, biochar addition decreased the total runoff by 2.4–10.8% (p > 0.05) and significantly increased the total soil loss and interrill erodibility (p <.05) by 20.8–50.8% and 20.4–29.2%, respectively. The changes in runoff, soil loss, and interrill erodibility were ruleless with an increase in the rate of biochar addition from 2% to 8%. The differences in runoff, soil loss, and interrill erodibility were nonsignificant among most biochar‐added treatments. After a 140‐day incubation period, total runoff and soil loss increased by 1.5–6.2% and 5.7–10.3%, respectively, and interrill erodibility increased for the 2% biochar addition and decreased for the 5% and 8% biochar additions. However, nonsignificant differences in runoff, soil loss, and interrill erodibility were observed before and after incubation. Our results implied that biochar addition to soil could increase the risk of erosion on sloping croplands, and thus, one should exercise caution when amending soil with biochar on sloping croplands. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • We studied sheet erosion on sloping plots affected by tillage when water and wind erosion alternatively occurred. • Results obtained through beryllium-7 measurements were verified by sediment yield estimation. • Sheet erosion rates were linearly or exponentially associated with slopes. • Steeper slopes weakened the effects of tillage patterns on sheet erosion. • Farming on steep cropland (>20°) should be forbidden in the study region. Abstract Tillage complicates erosion on sloping fields, especially in regions of combined wind and water erosion. The wind-water erosion crisscross region of the Chinese Loess Plateau is an example of such a region wherein erosion is caused by the stimulating effects of tillage, rainfall, and wind. Sheet erosion is an important form of cropland soil erosion and is closely correlated to the productive capacity of land. It is important to better understand the influence of tillage on soil sheet erosion in order to estimate the loss of fertile surface soil and to provide suitable tillage recommendations for the cultivation of sloping cropland in this region, which is susceptible to multiple erosion factors. This study aims to clarify spatial distribution and variation of sheet erosion rates as affected by different tillage patterns on sloping cropland under different slope conditions. We applied beryllium-7 measurements and sediment collection methods to estimate sheet erosion rates to reveal the distribution of sheet erosion on bare sloping fields, to determine correlations between sheet erosion rates and slopes (0°, 5°, 10°, 15°, 20°, and 25°), and to analyze variation in sheet erosion affected by tillage patterns on a plot scale. Results show that sheet erosion increased in a top-down direction and achieved maximum values at the mid- or lower-mid section of slopes, then erosion rates decreased or sediment deposition occurred at the base of slopes. Sheet erosion intensified with an increase in slope gradient fitting to linear or exponential functions regardless of the tillage pattern used (i.e., whether solely applying autumn plowing or a combination of autumn and spring plowing). However, tillage patterns had an obvious effect on sheet erosion. Differences in sheet erosion caused by tillage patterns increased from 5° to between 15° and 20° before decreasing at 25°. This demonstrates that steep slope gradients will weaken tillage pattern effects on sheet erosion, thus becoming a significant impacting factor on sheet erosion. Based on sheet erosion rates, we recommend that cropland be converted to grassland or shrubland when slope gradients are greater than 20° in the study region. Notably, a decrease in tillage intensity (frequency) helped in the reduction of sheet erosion on sloping croplands, and further tillage practices associated with conservation tillage should be applied on sloping cropland to obtain better soil erosion control results. [ABSTRACT FROM AUTHOR]

Purpose: The crisscross region of the Chinese Loess Plateau is affected from both wind and water erosion, and their relative contributions remain unclear. A combination analysis of 137Cs inventories, surface soil sample properties, and the local wind condition allows the measurements of total soil erosion, as well as the rates of wind and water erosion that are independently affected by slope aspect at a experimental site in the study area.Materials and methods: This study selected eight straight slope for investigation. Although the slopes had similar gradients, lengths, elevations, shapes, vegetation conditions, soil types, and land-use types, they faced different aspects. This study tested the soil organic matter content, particle size, specific surface area, and 137Cs inventory, including the mean 137Cs reference inventory from a region of flat grassland near a century-old temple located on the top of a hillslope. Water erosion were assumed to be similar for slope aspects on condition that rainfall and environmental conditions were similar, and differences in erosion on slope aspects were mainly attributable to wind erosion. This assumption was confirmed by stepwise linear regression analysis, and wind erosion was estimated from total erosion and water erosion.Results and discussion: The east-facing slope experienced almost no wind erosion, and erosion (91.4 t ha−1 year−1) it experienced was primarily caused by water according to estimation of total erosion and analysis to wind conditions. Based on the assumption that water erosion was similar on all slopes, the west-facing slope exhibited a similar rate of water erosion to the east slope, while the rate of wind erosion was 16.9 t ha−1 year−1. The northwest slope had the highest wind erosion rate (42.3 t ha−1 year−1), while the slope opposite to it (the southeast slope) had the highest wind deposition rate. Wind erosion on average contributed 27.4% to total erosion on windward slopes (northwest and north), while deposition occurred on the opposite leeward slopes (southeast and south).Conclusions: Although water erosion was found to be the primary driver of soil loss in this watershed, the effect of wind erosion cannot be neglected. It was mainly response for the erosion difference on slope aspects. [ABSTRACT FROM AUTHOR]

Soil erosion is a severe problem on China's Loess Plateau due to its fine-grained soils and the increasing frequency of extreme rainfall events. Accordingly, this study used a 100-year frequency rainstorm dataset to analyse sediment deposition and sources in a 27-km2 catchment with a dam field area of 0·14 km2 based on the hypothesis that sediments were intercepted by the dam (before collapse) during the rainstorm event and deposited in the dam field. This study applied composite fingerprinting, which revealed the sediment source contributions and estimated sediment deposition. Sediment deposition (626·4 kg m−2) decreased linearly or exponentially with increasing distance from the dam. Composite fingerprints based on the optimal parameters revealed relative sediment contributions of 44·1% ± 25·5%, 37·7% ± 35·0%, 9·0% ± 11·4% and 9·2% ± 11·5% by bare ground, croplands, grassland and forests, respectively. The 5-year cumulative sediment deposition from normal rainfall was 2·3 × 104 t less than the extreme rainstorm. Bare grounds and croplands were the dominant sediment sources following both the extreme rainstorm and normal erosive rainfall events but varied at different areas of the check-dam. Erosion patterns and start times depended on land use type, thereby affecting sediment profiles in the dam field. Furthermore, severe erosion from bare ground that were all gully slopes and gully walls occurred throughout the rainfall, whereas grasslands and forest erosion occurred earlier and croplands later. Finally, extreme rainfall promoted mass wasting on slopes, gully slopes and gully walls, which are important in determining extreme rainstorm erosion pattern variation. This study aimed to reveal erosion pattern variation under extreme rainstorm events. Copyright © 2017 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the processes of erosion-transport-deposition of sediments is necessary to develop more effective soil erosion prediction models. In this study, Beryllium-7 (7Be) was used as a tracer to describe the dynamics of soil erosion during a simulated rainfall event on outdoor cultivated plots. The quantitative results of interrill and rill erosion on slopes are discussed in this paper. And the calculated results using 7Be tracer are in good agreement with the measured ones. Therefore, 7Be tracer could accurately quantify the processes of erosion on the cultivated slope. [Copyright &y& Elsevier]

[Display omitted] • Applies a novel approach based on the check dam deposit of an individual event. • Establishes the inter-gully areas as the main source of the sediment-associated TOC. • The main sources of the two organic C fractions (POC and MOC) were different. • Approximately 10% of the TOC mobilized by erosion was lost during delivery to the dam. • The lost carbon was dominated by POC, while MOC accounted for ca. 13% of the loss. Information on the sources and fate of organic carbon mobilized by soil erosion is crucial for understanding the impact of erosion on carbon (C) cycling. However, few studies have evaluated this in low-order stream systems. In this study, we adopted a novel approach, that used the sediment deposited behind a check dam constructed at the outlet of the Fengzigou catchment (0.91 km2) on the Chinese Loess Plateau by a single high magnitude storm event, to simplify the field sampling requirements. The total sediment-associated organic carbon (TOC) was fractionated into particulate organic carbon (POC) and mineral associated organic carbon (MOC). These results were combined with those from a sediment source tracing exercise. This made it possible to explore further the source and loss of the sediment-associated organic carbon. The results showed that the inter-gully areas contributed the most eroded TOC (52.3 ± 7.6 %) and, together with the gully walls, represented the main TOC source. The primary contributor of the POC fraction in the deposited sediment was the inter-gully areas (80.5 ± 12.6 %), whereas the gully walls were the main contributor of the MOC fraction (54.9 ± 10.2 %). The total output of sediment produced by the event was 1304 ± 48 t and the equivalent value for sediment-associated TOC was 2.94 ± 0.26 t, of which the POC fraction accounted for 27.6 ± 3.6 % and the MOC fraction 72.4 ± 9.8 %. The TOC lost (0.3 ± 0.02 t) through the mobilization and delivery processes was 10.2 ± 1.2 % of the TOC mobilized by erosion, and the lost carbon was dominated by the POC fraction (86.7 ± 8.8 %). The specific TOC output from the catchment associated with the event documented was 0.3 t km−2. This work demonstrates the potential for erosion-induced carbon redistribution to provide a source for atmospheric CO 2 in the study area. [ABSTRACT FROM AUTHOR]

• The gully was the main sediment source, and the contribution of the gully to the slope was 8:2 between 1978 and 2010. • Erosion was dominated by the collapse of gully walls under the effect of gravity, which was triggered by rainstorms. • Changes in sediment contribution correlated to soil, landform, rainfall, coal mining and soil conservation. • Uncertainties of the fingerprinting approach are more significant and influential in complex environments. Sediment sources in catchments under the control of check dams in the wind-water erosion crisscross region are more complicated compared to other regions on the Chinese Loess Plateau. This is due to their general complexity, which mainly results from variation in soil, landform, vegetation, and erosion agents. Accordingly, we used the composite fingerprinting approach to trace sediment sources in a typical small catchment in this region. The aim was to reveal the erosion characteristics of the catchment throughout the trapping history of the check dam. Sediment sources were classified into three-source (paleosol, loess and sand) and four-source (paleosol-gully, loess-gully, slope bare of sand and slope covered by sand) groups on the basis of soil and landform types, respectively. Sediment sources throughout the whole trapping history of the check dam (1978–2010) could be classified into three stages according to variation in sedimentation rate. Results showed that depositional sediment in the check dam was primarily from gullies (averaging 80.1%), especially the paleosol-gully (>54.1%). The large contribution of gullies indicated that the main erosion agents were streamflow from rainstorm events and gravity. Coal mining also had a significant impact on contribution of sediment sources, especially for slopes. Since 1987, mining began to change the structure of hills in this region, leading to slope fissures, collapse, and landslides at junctions where gullies meet slopes, which increased the risk of slope erosion. This has caused an increase in sediment from slopes bare of sand distributed under condition of continues implementation of soil conservation measures, which converted sloping cropland into grassland or forest. Further studies are necessary to gain better insight into sediment transport and deposition within such complex environments, as well as to distinguish between the effects of multiple erosion agents. [ABSTRACT FROM AUTHOR]

Biochar's potential impact on soil erosion has gained attention, but remained inconsistent, particularly lacks the results from continuous field monitoring under diverse rainfall conditions. This study aimed to explore the long-term variation in soil erosion induced by biochar addition under distinct natural rainfalls. Six runoff plots, treated with different amounts of biochar derived from apple tree branches (0, 1%, 2.5%, 4%, 5.5% and 7%), were established. Over a four-year period from 2017 to 2020, runoff and soil loss from these plots were continuously monitored and analyzed. Among 215 recorded rainfall events, 27 events resulted in runoff and sediment production were classified into three rainfall patterns (R I , R II and R III) using K -means clustering. R III characterized by high mean rainfall depth (138.80 mm), duration (3443 min), and erosivity (879 MJ.mm (ha. h)−1), but infrequent occurrence, followed by R II and R I with moderate and low mean depth, duration and erosivity, but higher frequency. Biochar addition, relative to control, resulted in an average annual runoff reduction, ranging from 9% to 36%, with a mean reduction of 28%, and reduced runoff for each rainfall, ranging from 4% to 28%, with a mean reduction of 12%. Similarly, biochar addition also reduced average annual soil loss, ranging from 43% to 79%, with a mean reduction of 61%, and reduced soil loss for each rainfall, ranging from 29% to 74%, with a mean reduction of 52%. The reduction of runoff and soil loss was positively correlated with biochar addition rates. Notably, the soil loss reduction was exceeded that of runoff. Soil erosion was negatively linked to surface area of soil particles (p < 0.05), total carbon, and total organic carbon (p < 0.01), but positively correlated with sand content (p < 0.01) and bulk density (BD) (p < 0.05) under biochar addition. Comparison of the mean reduction of runoff and soil loss among three rainfall patterns, the order was as follows: R II >R I >R III. The optimal controlling of soil erosion was observed in 7% biochar addition under R II. Runoff-soil loss relationships well-fitted by power equation, showed soil incorporated with biochar treatments exhibited heightened susceptibility to erosion under R III with high intensity compared to R II and R I with moderate or low rainfall intensity. Thus, the findings indicate biochar is a potential soil amendment to improve a degraded or degrading sloping farmland, however, the rainfall characteristics need to be considered when it is applied to the sloping farmland prone to erosion. • Impacts of rainfall patterns on soil erosion were investigated under biochar addition. • Biochar inhibited persistently soil erosion over the entire four-year period. • Reduction of soil loss caused by biochar addition was greater than that of runoff. • High rainfall intensity weakened soil erosion reduction induced by biochar addition. [ABSTRACT FROM AUTHOR]

Abstract Adding biochar to soil is an efficient method to improve soil physicochemical properties. Understanding the effect of this method on soil and water loss is also important. However, there is insufficient data available to assess this effect. Thus, a simulated rainfall (intensity 90 mm h−1) study was conducted to explore the effect of biochar particle sizes (2–1, 1–0.25, and <0.25 mm) and incubation times (0 and 8 months) of biochar and soil mixture on soil and water loss. Our experiments consisted of measuring soil loss, surface runoff, >2 mm water-stable soil aggregate content, and soil saturated hydraulic conductivity (K sat) from a perforated box (1 m long and 0.4 m wide) with a 27% slope gradient that contained soil, with a constant application rate of biochar at 1% (wt/wt). Soil without biochar was used as the control. The results indicated that biochar-treated soil delayed the time to runoff compared to the control by 12.67% to 32.58%, with the smallest particle size (<0.25 mm) and 8 months incubation being the most effective. In general, all tested biochar particle sizes had some control on soil and water loss. The total runoff volume after biochar additions of 2–1, 1–0.25, and <0.25 mm particle sizes decreased by 2.04%, 24.21%, and 29.63% and by 14.72%, 13.83%, and 30.76% with no incubation and 8 months of incubation, respectively, while the total erosion decreased by 12.86%, 34.30%, and 34.29% and by 20.41%, 11.85%, and 31.93% with no incubation and 8 months of incubation, respectively, compared to the control. Eight months of incubation could effectively decrease both the total runoff and amount of erosion only for soil amended with 2–1 mm biochar particles compared to those with no incubation. Furthermore, 2–1, 1–0.25, and <0.25 mm biochar treatments could increase >2 mm water-stable soil aggregate content and K sat relative to the control. We speculated that the positive effects of biochar on soil and water loss were possibly due to an improvement in soil physical properties, such as an increase in the >2 mm water-stable soil aggregate and K sat. Graphical abstract Unlabelled Image Highlights • Biochar particle sizes affect hydro-erosional parameters on loess slope. • Biochar-treated soil delayed runoff initiation time and decreased runoff and erosion. • Runoff and erosion rates usually decreased with decreasing biochar particle size. • Longer incubation time might be the more effective in mitigating runoff and erosion. [ABSTRACT FROM AUTHOR]

Declines of soil organic carbon (SOC) and degradation of soil function are caused by long-term soil erosion and cultivation. Although the variations of bulk SOC have been extensively studied, the driving mechanisms of variations in SOC fractions, i.e., carbon in coarse particulate, fine particulate, and mineral-associated organic matter (CPOM-C, FPOM-C, and MAOM-C), and their relationship with soil erosion remain unclear on sloping farmland. In this study, two areas of farmland with different slope types (convex vs. straight) and reclamation periods (50 years vs. ≥100 years) in the black soil region of Northeastern China were chosen to explore the roles of soil erosion on the variations of SOC and their size fractions based on the 137Cs tracer technique. The results showed that the average net erosion rate of the straight slope was 2810.09 t km-2a-1 and the convex slope was 3801.71 t km-2a-1 with higher spatial variability. When compared with uncultivated land, SOC contents of convex and straight slopes have decreased by 13.58% and 35.18%, with a reduced rate of 0.089 g kg-1 a-1 and 0.116 g kg-1 a-1, respectively. Although the CPOM-C fraction showed the most significant relative decreases (over 73.24%), the absolute declines of MAOM-C were more significant, especially in the straight slope with a more extended cultivation period. The contributions of erosion to the SOC decreases on convex and straight slopes were 69.54% and 13.09%, respectively. Erosion exerted a significant influence on finer particles such as FPOM-C and MAOM-C. With increasing cumulative erosion, the absolute magnitude of each SOC fraction in soils decreased. But the proportion of MAOM-C increased, while FPOM-C and CPOM-C decreased. Overall, our findings demonstrated that soil erosion not only induced the loss of SOC fractions but also transformed the proportional distribution of their fractions, and then affected the functions of SOC. Moreover, the effects of tillage (i.e., an increase in microbial activity) on straight slopes are not negligible in farmland that has experienced long-term cultivation but relatively little erosion. Apart from erosion reduction in areas of severe erosion, appropriate fertilization for farmland with a long history of cultivation should also be adapted to achieve sustainable development of black soil resources. • The erosion rate, estimated by 137Cs, is greater on convex than on straight slope. • Most SOC fractions are on a depletion trend in both farmlands. • The main forms of SOC loss differ between convex and straight slopes. • Erosion contributes more to SOC loss in convex slope than in straight slope. • The proportion of MAOM-C increased with erosion, while FPOM-C and CPOM-C decreased. [ABSTRACT FROM AUTHOR]

• Wind erosion and deposition were affected by moss crust coverage rates and distribution pattern. • Both erosion and deposition were decreased with an increase in moss crust coverage rates. • Erosion rates decreased with moss crust distribution pattern changes in the order of SC > P/S > CS > SCS. • Composite indices should be developed to quantify impacts of BSCs spatial distribution on wind erosion. Although biological soil crusts (BSCs) provide considerable control over wind erosion in arid and semiarid regions, understanding of BSCs coverage rates and distribution patterns impacts on wind erosion is remain limited, which further causes poor quantification of BSCs factors in wind erosion prediction models. This study estimated wind erosion affected by moss crust coverage rates and distribution patterns using the weighting approach and beryllium-7 measurements through wind tunnel experiments, and screened factors that significantly influence wind erosion based on landscape metrics and multiple linear regression. Results showed that both moss crust coverage and distribution pattern significantly affected wind erosion and deposition. When moss crust coverage increased from 10% to 80%, average erosion rates in bare soil areas of trays almost all decreased logarithmically from 623.0 to 27.4 g m−2 min−1, while the average deposition rates in moss crust covered areas decreased from −21.7 to −16.7 g m−2 min−1. Moss crust located at the middle area of trays (SCS) showed better overall erosion control effects, while moss crust located at downwind of sand (SC) showed better sediment trapping effects compared to other distribution patterns when moss crust coverage was the same. The SCS and SC patterns decreased wind erosion and deposition rates reached up to 81.9% and 38.0%, respectively. Moreover, wind erosion rates when arranged moss crust parallel to the wind direction resulted in significantly higher soil erosion (i.e., by a factor up to 7.3) compared to that of perpendicular to the wind direction. Stepwise regression showed that only wind velocity and moss crust coverage were included in the linear regression equation with a relatively low R 2 value (R 2 = 0.35), but excluded other landscape metrics. This is indicated the importance of developing composite indices and their associative algorithms should be considered when quantifying spatial distribution impacts of BSCs on wind erosion. [ABSTRACT FROM AUTHOR]

• Taguchi method is generally superior to the orthogonal design method. • Taguchi method presented better results for dependent variables with complex variations. • Taguchi method presented better results for small-scale slopes than large-scale slopes. • Taguchi method could act as a substitute for the full-factorial design method. The benefits of the Taguchi method have been demonstrated in diverse fields. However, its applicability to soil erosion experiments at the slope scale under various conditions remains unclear. Using 6 published datasets that included the dependent variables of erosion rate (D), runoff rate (R), sediment concentration (C), flow velocity (V) and transport capacity (Tc), we compared the results from the full-factorial design method with those from the Taguchi and orthogonal design methods to validate the applicability of the Taguchi method to simulated soil erosion experiments at the slope scale under different conditions. The statistical parameters of the dependent variables from the orthogonal design and Taguchi method were very close to those from the full-factorial design for all dependent variables. The trends of the main effects based on different factor levels were consistent for 35 out of 45 sets from the full-factorial design and Taguchi method and for 27 sets from the orthogonal design. The optimum conditions for 10 and 7 dependent variables (out of 14) for the Taguchi and orthogonal design methods were the same as those for the full-factorial design, respectively. In addition, 13 and 8 dependent variables (out of 14) for the Taguchi and orthogonal design methods had the same factor rank order of percentage contributions as the full-factorial design method, respectively. Based on a univariate analysis of variance, the evaluating indicators for predictive power, including the determination coefficient, Nash-Sutcliffe efficiency, relative root mean squared error, mean absolute percentage error and Thiel inequality coefficient, indicated that the Taguchi method predictions were better than the orthogonal design predictions. Overall, the Taguchi method could obtain more reliable conclusions for soil erosion than the orthogonal design method at the slope scale. These findings suggest that the Taguchi method could be successfully applied to soil erosion experiments and could better replace the full-factorial design method at the slope scale compared with the orthogonal design method. [ABSTRACT FROM AUTHOR]

• Sediment PSD was mainly susceptible to rainfall patterns and intensity. • The enrichment of MOC varied with rainfall patterns and slope length. • MOC was removed preferentially in selective erosion process than POC. • Rainfall patterns and slope length affect SOC loss by erosion and PSD indirectly. The effect of soil erosion processes on the properties of sediment and organic carbon fractions is not well understood under complex erosion environments, such as various rainfall characteristics and transport distances, which leads to a gap in knowledge regarding the role of soil erosion in the global carbon cycle. This study investigated the impact of different rainfall characteristics (patterns and parameters) and slope lengths (5 m ∼ 20 m) on the sediment yield, particle size distribution (PSD) and properties of organic carbon fractions on China's Loess Plateau. The results show that runoff was highest under rainfall pattern A (extreme rainfall), while the sediment concentration peaked under rainfall pattern B (heavy rainfall), with significant correlation with slope length, rainfall intensity, kinetic energy, rainfall erosivity and precipitation (p less than 0.05). Silt- and clay-sized fractions were transported as primary particles and enriched under rainfall patterns B and C with no differences between slope lengths. The enrichment ratio (ER) of sediment, effective and ultimate particles were primarily influenced by rainfall intensity-related parameters. In contrast, the aggregation ratio (AR) tended to be influenced by rainfall kinetic energy. The content and loss of organic carbon fractions correlated to rainfall parameters and slope length, although no significant difference was observed between different rainfall patterns and slope lengths. Lost organic carbon fractions were predominantly Mineral-associated organic carbon (MOC), with great enrichment under rainfall pattern C and rapid depletion as the slope length increased. Structural equation models (SEM) indicated the effect of rainfall characteristics and slope length on organic carbon loss was mainly due to the regulation of soil loss and particle size distribution of sediment in selective transport erosion processes. We highlighted the need to consider the effect of soil erosion and particle size distribution comprehensively on the carbon cycle from the perspective of organic carbon fractions to describe the potential effects of soil erosion on the carbon budget quantitatively, especially in complex environmental conditions with consideration of scale effect. [ABSTRACT FROM AUTHOR]

Soil erosion significantly affects the dynamics of the terrestrial carbon (C) cycle. Erosion removes C-rich topsoil and deposits it in lower-elevation areas and exposes deeper C-poor horizons at the surface. However, the mechanisms responsible for the mobilization and deposition of microaggregate soil organic carbon (SOC) due to soil erosion at the catchment scale remain unclear. The main objective of this study is to illustrate the effects of different erosion processes on the distribution and deposition of microaggregate SOC. The activity of 137 Cs and extreme rainfall events were used as dating methods Based on the microaggregate size distribution and the K-means clustering approach, 75 flood couplets were identified in an 11.3-m sediment deposit profile of the check dam in the Nianyangou catchment and classified into three couplet types. In each flood couplet, the SOC concentrations and amounts in three microaggregate fractions (250–50, 50–20 and <20 μm) were quantified. The following results were obtained. (1) 137 Cs activity and a record of extreme rainfall events can be used to characterize the sediment deposition process. (2) Sediments with fine microaggregate fractions (Couplet Type I) contained abundant SOC and were mainly associated with low-intensity rainfall conditions, whereas sediments with coarse microaggregate fractions (Couplet Type III) had higher SOC concentrations and were mainly associated with high-intensity rainfall conditions. (3) Couplet Type I sediments were most likely related to sheet and interrill erosion, whereas Couplet Type III sediments were likely associated with rill and gully erosion. Our study contributes to the understanding of the effects of soil erosion on microaggregate SOC dynamics at the catchment scale and further illustrates the carbon sequestration mechanism active in check dams of the Loess Plateau. [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]

• Soil erosion rate and vegetation factors display significant variation on the slope. • The relationship between plant and erosion is complicated at the sampling point scale. • Erosion rates should be carefully extrapolated to other scales due to scale effect. • Be-7 method is potential for interaction study of soil erosion and its environment. Scale effects, the phenomena of runoff and sediment yield differ from different spatial and temporal scales, exist in the whole process of soil erosion. Vegetation cover can reduce the degree of soil erosion at the plot and slope scales, but there is little research on the reduction effect of vegetation on soil erosion at a specific point on the plot, due to the limitations of traditional methods. Based on in situ sampling on a representatively abandoned farmland slope, the corresponding relationship between vegetation and sheet erosion was analyzed quantitatively using the modified 7Be tracing model with vegetation factor. The results showed that 7Be activity per unit mass and per unit area in soil ranged from 2.45 to 27.05 Bq kg−1 and 50.09 to 528.11 Bq m−2, and in plants ranged from 378.20 to 691.82 Bq kg−1 and 72.61 to 307.33 Bq m−2, respectively. Plants were responsible for 22.6 %±7.3 % of total 7Be interception on the slope, affected by vegetation coverage, leaf area index, dry biomass and flesh weight. Plants were mainly distributed on the backslope and toeslope, with vegetation coverage, leaf area index, dry biomass and flesh weight ranging from 0.26 to 0.75, 0.48 to 2.45, 0.17 to 0.45 kg m−2 and 0.38 to 0.85 kg m−2, respectively, while the peak area of soil erosion was concentrated on the backslope, with a rate ranging from 0.06 to 16.76 kg m−2. At the specific point scale, the corresponding relationships between soil erosion and vegetation coverage, leaf area index, dry biomass, and flesh weight of plants are not as significant as in the previous study at the plot or slope scale. This indicates that the reduction of erosion for plants varies with scale dependency, which is more complicated at the specific point scale, rather than simply decreasing with the increase of vegetation. Our results highlight that there is a scale effect of plants on soil erosion, and the 7Be measurement is of great potential to explore this effect at the specific point scale. [ABSTRACT FROM AUTHOR]

Assessing and predicting soil erosion requires knowledge of the influences of antecedent soil moisture and vegetation cover as well as of their combined effects on soil erosion processes. Past research typically focused on either vegetation cover or antecedent soil moisture. Even though these parameters are likely related under field conditions, studies on their synchronous combined effect on soil erosion processes are scarce. We conducted laboratory experiments on soil erosion using simulated rainstorms (intensity 77 ± 4.5 mm h −1 ; 60 min duration) on a light loamy soil under different levels of wheat-seedling cover and antecedent soil moisture that were both produced by different sprayed applications of water (30, 40, 50, 60 or 70 mm) during a 40- to 44-day growing period. The objective was to explore the effect of the combined effects of wheat-seedling cover and antecedent soil moisture on soil erosion. Wheat-seedling cover and antecedent soil moisture increased with applied water levels from 9.7% to 37.2% and from 8.4% to 12.2%, respectively. The shortest time to runoff was observed for intermediate values of cover and antecedent moisture (60-mm water level). Infiltration rates and total infiltration generally decreased with increases in water applications. Runoff rate and soil loss were not significantly different ( P > 0.05) among the 40-, 50- and 60-mm water treatments, but abruptly increased under the 70-mm treatment. At the 70-mm level, the total runoff volume and total soil loss were, respectively, between 15% and 37% and between 15% and 45% higher than those at the other water levels were. Antecedent soil moisture was the predominant factor affecting infiltration, runoff and soil loss during the rainstorms. In this study, the effects of the relatively low wheat-seedling covers were obscured by those of the antecedent soil moisture at the small-flume scale. This suggests that the effects of vegetation cover and antecedent soil moisture on soil erosion should be considered together when assessing and predicting soil erosion. [ABSTRACT FROM AUTHOR]

• Reasonably low biochar application rates (1% or 3%) can reduce soil loss to runoff. • 1–2 mm biochar particles had less runoff loss of soil, biochar, and total nitrogen than finer particles at 3% application rate. • ≤5% biochar addition reduced total nitrogen loss through soil but increased total nitrogen in sediment. • High biochar application rates (7%) increased the risk of soil, biochar, and total nitrogen losses. Biochar is known to improve soil physical properties, but its role in influencing soil erosion and nutrient losses, as well as biochar itself loss is poorly understood. The objectives of this study were to determine the magnitude of soil, biochar and nitrogen losses in runoff and quantify the degree of sediment enrichment with biochar and nitrogen in a soil amended with biochar. A loessial soil was amended with five rates of nitrogen-rich biochar [0, 1%, 3%, 5%, and 7% (w/w)] that had <0.25 mm particles and incubated for 8 months. A companion study compared three biochar particle sizes (<0.25, 0.25–1, and 1–2 mm) applied at 3% rate. A series of simulated rainfall events (90 mm h−1) were applied to the soil which was held in a box at a slope of 27%. The results showed that biochar addition of 1% or 3% reduced soil loss rates while the 7% biochar addition rate increased soil loss. Biochar loss rate was proportional to the biochar addition rate when the biochar particle size was <0.25 mm. Coarser biochar particles (1–2 mm) are retained in the soil better than the finer <0.25 mm biochar particles. Total nitrogen loss and sediment enrichment with nitrogen and biochar were also lowest with the coarse biochar particles (1–2 mm) addition. The finer biochar particle sizes (<0.25 mm) were more vulnerable to erosion losses and its application caused greater total nitrogen enrichment in sediment. When finer biochar particles (<0.25 mm) are used, 1% biochar application leads to the best results for soils with risks of erosion but 7% biochar increased the risk of soil, biochar, and total nitrogen losses. Our study overall shows that knowledge of the pros and cons of applying biochar should be carefully considered before providing biochar application recommendations as a soil supplement on loess hillslopes. [ABSTRACT FROM AUTHOR]