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• Marsh erosion had contrasting effects on soil bacterial and fungal communities. • Bacterial diversity decreased but fungal diversity increased with marsh erosion. • Erosion had specific effects on soil microbial composition, especially bacteria. • The complexity of fungal networks increased substantially with erosion. • Erosion-induced changes in microbes may affect soil function and nutrient cycling. Coastal salt marshes, especially their seaward boundaries, are experiencing severe erosion and area loss worldwide because of human disturbances and natural changes. However, how marsh erosion affects soil microbial communities and their potential functions remains poorly understood in subtropical coastal ecosystems. Herein, simultaneous measurements of the abundance, diversity, and composition of bacterial and fungal communities were conducted along a marsh erosion gradient, based on Illumina sequencing of 16S rRNA and ITS genes. Our results indicate that marsh erosion is often accompanied by a loss of plant biomass and a decrease in soil total carbon, total nitrogen, and organic matter concentrations, but an increase in soil water content. We found that the abundance of bacteria and fungi tended to decrease with erosion, especially for bacterial communities. Marsh erosion had opposite effects on the alpha-diversity of bacterial and fungal communities, with bacterial diversity decreasing but fungal diversity increasing with marsh erosion. The beta-diversity and composition of bacterial and fungal communities were altered by marsh erosion, and in particular bacterial communities were clustered into three groups: uneroded, eroding, and eroded. Network analysis demonstrated that the inter-relationships of the bacterial community did not significantly change with the erosion gradient, but the complexity of the fungal networks increased. The diversity and composition of the bacterial and fungal communities can be jointly explained by plant biomass, soil nutrient dynamics, and bulk density. We conclude that marsh erosion-induced changes in soil properties and plant loss altered the diversity and composition of bacterial and fungal communities, which decrease bacterial abundance and diversity but increase fungal diversity and network complexity, suggesting that these microbial taxa contribute differently to soil function and nutrient cycling as marsh erosion continues. [ABSTRACT FROM AUTHOR]

• Quantified the effect of discharge on erosion and morphology characteristics. • The impact of rill depth on cumulative sediment yield was greater than that of rill width. • Unit stream power can be used to describe dynamic mechanisms of eroding rill. • Rill erodibility parameters for eroded rill were 0.574 × 10−3 s m−1. Field experimental studies on the erosion characteristics and dynamic mechanisms of rills that have already eroded (eroded rills) when rainfall occurs are limited, especially compared to the dynamics of those rills that have experienced erosion for the first time (eroding rills). The field runoff scouring experiments included two intermittent sub-experiments: flow discharge of 9, 13, 17, 21, 25, and 29 L min−1 (E1) with a scour duration of 60 min and flow discharge of 6, 9, 12, 15, 18, and 21 L min−1 (E2) with a scour duration of 10 min. Two antecedent soil moistures (15 % and 25 %) were used for the runoff plot (18 × 1 m) before starting E1. The results from E1 indicated that flow discharge and antecedent soil moisture increased the average runoff rate (19.46 % with discharge, 4.63 % with soil moisture), soil loss rate (63.94 % with discharge, 58.80 % with soil moisture), rill width (16.49 % with discharge, 4.66 % with soil moisture) and rill depth (13.40 % with discharge, 6.60 % with soil moisture). The average flow velocity varied from 0.231 to 0.344 m s−1, and the flow regimes were basically subcritical turbulent flows. The impact of rill depth on cumulative sediment yield was greater than that of rill width. Moreover, the critical values of flow velocity, shear stress, stream power, unit stream power, and unit energy under eroded rills were 0.183 m s−1, 7.532 Pa, 1.278 W m−2, 0.032 m s−1 and 0.007 m from E2, respectively, and the rill erodibility parameters for E1 and E2 were 0.252 × 10−2 and 0.574 × 10−3 s m−1, respectively. The flow unit stream power and stream power could be effectively used to simulate the dynamic mechanism under conditions E1 and E2, respectively. The study aids in understanding the dynamic mechanism of rill erosion under intermittent rainfall conditions in the field. [ABSTRACT FROM AUTHOR]

• A new method to estimate the C-factor for various LULCC scenarios. • Combined changes of climate and LULC leads to increased water erosion in the future. • Impoverished countries are increasingly vulnerable to erosion compared to wealthier nations. • Soil erosion rates are rising faster in lower-middle-income countries due to greater vulnerability. • Significant increase in global soil water erosion is projected after the 2050s. Soil water erosion presents a significant challenge to the sustainable productivity of agriculture, making the precise prediction of its future patterns essential for ensuring global food security. However, there is a notable scarcity of global-scale explorations of soil water erosion and its anticipated future changes. This study proposes a method for calculating the C-factor using the fraction of land use/land cover change (LULCC) scenario data. Subsequently, we conduct an extensive evaluation of global water erosion from the 2010 s to the 2090 s under various climate change and LULCC scenarios, providing a comprehensive analysis of historical and projected erosion patterns. Predictions indicate a rapid increase in total soil erosion, but the rate of increase may decelerate after the 2050 s, with projected average increases of 6.8 %, 9.3 % and 11.3 % per 20-year interval under the SSP1-RCP2.6, SSP2-RCP4.5 and SSP5-RCP8.5 scenarios, respectively. The most rapid increase in soil erosion rates is observed in lower-middle-income countries such as India and Tanzania, which are more sensitive to changes in climate and land use, whereas many high-income countries, predominantly in Europe, are likely to experience a reduction in erosion rates. We emphasize the roles of both climate change and LULCC in shaping future erosion dynamics. Specifically, while LULCC is the dominant factor under the SSP1-RCP2.6 and SSP2-RCP4.5 scenarios, climate change emerges as the chief influencer in the SSP5-RCP8.5 scenario, particularly after the 2050 s. This highlights the importance of devising regional and scenario-specific mitigation approaches, especially for more vulnerable nations. The findings highlight the need for enhanced international cooperation and increased support from low- to middle-income countries to address the challenges of water erosion and promote global sustainability. [ABSTRACT FROM AUTHOR]

• Soil erosion rate was 3 times greater on the south-facing hillslope as compared to the north-facing hillslope. • Soil water content was the dominant factor causing the difference in erosion rates under a water-limited condition. • Greater soil erosion rates resulted in elevational distributions of soil physicochemical properties on the south-facing hillslope. Soil erosion causes serious grassland degradation in the Three-River Headwater Region (TRHR) of the Qinghai-Tibet Plateau. Identifying source areas of erosion is important, including understanding the influences of hillslope aspect on soil erosion. However, the effect of hillslope aspect on soil erosion is a much-debated process, wherein contrasting results were previously reported. We hypothesized that aspect-induced differences in environmental variables will be related to differences in erosion magnitude and spatial pattern, and that these differences will impact soil physiochemical characteristics as well. To test this hypothesis, soil samples were collected at conjoined south- and north-facing hillslopes along elevational profiles in a small watershed in Yushu County, with measurements of soil water content (SWC), soil organic carbon (SOC), soil organic matter (SOM), soil particle size distribution, soil total nitrogen (STN) and phosphorus (STP). Soil erosion rate was estimated using 137Cs technology. The results showed that soil erosion rates of the two hillslopes ranged from 0.073 to 10.83 t ha-1 yr-1, and were 3 times greater on the south-facing hillslope. Soil water content ranged from 7.6% to 76.8% on the two hillslopes with lower values on the south-facing hillslope due to the greater solar radiation. By Spearman correlation analysis and path analysis, we concluded that lower soil water content on the south-facing hillslope restricts vegetation growth, and hence resulting in greater soil erosion under the case where vegetation growth is dominantly controlled by water availability. Greater soil erosion on the south-facing hillslope caused greater surficial accumulation of coarser materials and greater loss of soil nutrients, which are expected to complicate the hydrological erosion process. Moreover, the downslope increased soil erosion rate should be fully considered in conservation practices. These results will improve our understanding of the interaction and feedback mechanisms between soil characteristics, vegetation function, and soil erosion in the TRHR. [ABSTRACT FROM AUTHOR]

• Soil moisture content varied with soil depth, upslope distance, vegetation type, and time. • Soil organic carbon and moisture were lowest in Robinia pseudoacacia plantations. • Grassland showed lower soil moisture loss and greater organic carbon sequestration. • On the Loess Plateau, afforestation within grassland may enhance ecosystem services. Large-scale afforestation is considered controversial as an ecosystem renewal strategy for the Loess Plateau of China, since it may increase soil organic carbon (SOC) but may also exacerbate water shortages. In our study, we aimed to clarify how afforestation and slope affect soil moisture content (SMC) and SOC and their interaction particularly for deep hillslope profiles on long hillslopes, in terms of the trade-off between soil moisture and organic carbon. This study investigated SMC and SOC density (SOCD) from 0 to 400 cm hillslope depth profiles at 20 m intervals uphill to 100 m in the May and October (the beginning and end of the growing period, respectively) from 2015 to 2017. The three sampling sites were located in Robinia pseudoacacia plantation, natural forest, and natural grassland as the control. Soil moisture deficit and SOC sequestration of plantation were compared to those of grassland, and the trade-off between SMC and SOCD was evaluated. The results showed that SMC and SOCD were the lowest in the Robinia pseudoacacia plantation, indicating that the plantation exhibited a greater soil moisture deficit and SOC loss than the grassland. In the plantation and natural forestland, the subsoil (100–400 cm) exhibited greater soil moisture deficit and SOC loss than the soil (0–100 cm). SOCD increased while SMC decreased with upslope distance for all hillslope layers in both plantation and natural forestland. The downslope sites exhibited more severe soil moisture deficit, and greater SOC loss than the upslope sites. Natural grassland exhibited low water depletion and high SOC sequestration. Further, the downslope plantation sites exhibited the lowest root mean square deviation for the relationship between SMC and SOCD. Based on these findings, a vegetation restoration strategy involving afforestation of downslope patches within a contiguous grassland matrix may achieve high-level maintenance of ecosystem services. These findings provide a theoretical basis for vegetation restoration on the Loess Plateau. [ABSTRACT FROM AUTHOR]

• Catenary soils are still formed on karst hillslopes composed of pure dolomite rock. • The fundamental control on dolomite hillslope soil loss is the soil type. • The lack of large fissures in the dolomitic weathering crust results in no significant underground soil loss. Dolomite hillslopes are highly vulnerable to rocky desertification, but the linkages among soil type, runoff mechanisms, and soil erosion remain unclear. During four hydrological years (2018–2021), soil type, plot-scale hydrological and erosion behavior at the upper, middle, and lower slopes along the dolomite hillslope in karst regions of Southwest China were investigated. The results indicated that along the downward slope direction, the degree of soil development gradually increased, forming a typical soil catena pattern. The soil types along the downward direction on the dolomite hillslope gradually transitioned from Entisol to Inceptisol and to Semi-Alfisol. The Entisol was thin and gravelly, with the highest volume ratio of gravel of 75 %. In contrast, Semi-Alfisol was thick and clayey, with the highest volume ratio of fine soil of 97 %. The surface runoff coefficient of the upper slope was only 2.3 % because of the high water infiltration capacity of shallow and rocky soil, and the runoff generation mode was dominated by discontinuous infiltration–excess runoff occurring on rock outcrop patches. Due to the higher soil water content (mean value of 37 %) and frequently occurring lateral flow, the lower slope exhibited the highest surface runoff coefficient of 21 %, mainly as saturation-excess runoff. Catenary soils and their correspondingly divergent hydrological regimes led to average annual soil losses of 0.4, 0.8, and 2.8 t·ha−1·yr−1 at the upper, middle, and lower slopes, respectively. These results advance the understanding of the relationship between hydrology and erosion on karst hillslopes and provide theoretical support for further rocky desertification control. [ABSTRACT FROM AUTHOR]

The maximum depth of rainfall in any 30-minute period - I 30 - has been used as an index of erosive rainfall events for more than half a century, and is a key component of the R factor in the Universal Soil Loss Equation (USLE) and its derivatives. Other indices are in common use, including I 5 , I 10 , and I 15. However, there has been little study of the ability of I 30 to capture the erosive nature of a rainfall event in regions beyond the foundation experimental work in the USA. This paper examines several apparently neglected issues: how reliance on fixed clock-periods might diminish the efficacy of the various indices of short-interval intensity; how well a single 30-minute period is able to reflect the intensity-duration properties of long enclosing rainfall events, and hence, whether the influence of event duration should be evaluated in applications of I 30 and related indices. Results from two Australian sites with high-resolution rainfall records show that within the enclosing rainfall events, actual intensities corresponding to the I 30 value (which is an equivalent intensity or 'rainfall rate', calculated from rainfall depth in 30 min) commonly occur for both less and >30 min. Often the I 30 interval within a rainfall event excludes the most intense periods of rain, and in long events the index reflects ≪1% of the event duration. The I 30 intensity can occur for total durations of 1–3 h in the events studied, or for just a few minutes. An alternative class of indices is proposed, in which fixed clock-periods are not used, and instead, the duration of rainfall within an event that exceeds a nominated intensity is recorded as an index of intensity. This has a number of advantages, including the ability to work with events shorter than 30 min, which are frequently intense but which cannot yield an I 30 index that is strictly comparable to those of longer events. Illustrative results for this new index are presented. • Rainfall events in two high-resolution rainfall records from two Australian sites are analysed for I30. • The I30 period sometimes includes intensity peaks but frequently does not. • Determining I30 for events shorter than 30 min in a consistent way is problematic. • A new intensity index, the duration of rain at and above the I30 intensity, is explored. [ABSTRACT FROM AUTHOR]

• The parent material of the plinthosol was wind-formed deposits. • The parent material had an impact on the aggregate stability. • The aggregate stability was also affected by the initial soil moisture and OM. • The aggregate stability of the red matrix and white veins differ significantly. Soil aggregate stability is a key factor that affects soil erosion and ecological restoration. In this study, three typical plinthosol profiles in Wuhan (W), Yueyang (Y), and Jiujiang (J) were selected, and the mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimension were used as indicators of soil aggregate stability, as well as the erodibility factor (K value). Based on the end-member analysis, it appears that the plinthosols in the three profiles were wind-formed deposits, which greatly affected particle size and erodibility. There was a greater resistance to erosion among the plinthosols developed from finer grains than among those developed from coarse grains. The stability of aggregates in profiles W and Y decreased gradually with depth, while it varied little in profile J. The initial moisture content had a significant effect on the anti-erodibility of the plinthosols, and there were some differences between the profiles: in profile W, the anti-erodibility increased with the increase in initial moisture and reached its maximum value at the initial moisture content of 20%; in profiles Y and J, when the initial moisture content was 15%, the anti-erodibility was the highest. Reddish matrix had a higher anti-erodibility than white veins. Profile J had the largest stability gap between white veins and reddish matrix, followed by profile Y and W. These results provide a theoretical basis for the conservation of soil and water in the Yangtze River middle reaches by revealing the stability characteristics of plinthosols. [ABSTRACT FROM AUTHOR]

The effects of soil water content (SWC) and erodibility on available nutrient losses, as well as the influence of freeze-thaw on available nitrogen (AN) and phosphorus (AP) losses from loess soils have rarely been considered. We report on a series of laboratory simulation experiments conducted to determine SWC and soil erodibility effects on AN and AP losses under freeze-thaw conditions. Effect of freeze/thaw compared to unfrozen, two treatments were set (LS: Loess that unfrozen; FTS: Freeze-thawed a loess), and we studied five SWCs, between 10% and 30%, and we divided SWCs into two groups: lower water content areas (10% and 15%), higher water content areas (20%, 25%, and 30%). Overall, significant differences in runoff/sediment associated AN and AP concentrations of different SWCs for two treatments (p < 0.05) were noted, while the relationship between SWC and AN and AP loss show a quadratic function change trend (R 2  > 0.8). Largest runoff-associated AN and AP losses were found when the SWC was 30% and the largest sediment-associated AN and AP losses were found when the SWC was 10% in the two treatments. The soil erodibility factor ( K ) of the LS was less than that of the FTS when the SWC was low, and greater in a high water content area. The influence of runoff on sediment was positively linear. The absolute slope of the regression line between runoff rate and sediment yield rate is shown to be suitable as a soil erodibility indicator, while runoff-associated AN losses are mainly controlled by runoff rate, and are weakly affected by soil erodibility (p > 0.05). However, soil erodibility significantly influenced sediment-associated AP losses (p < 0.01), best described by a positive logarithmic relationship. Since the sediment-associated AP losses dominated the total AP losses for the two treatments, soil erodibility also exhibited a significant influence on total AP losses (p < 0.01). The freeze-thaw effect increased the total AN loss when the SWC was 15%, 20%, and 30%, and increased the total AP loss when it was 10% and 15%. The results of this study provide a better understanding of soil and available nutrient loss mechanisms under freeze-thaw conditions. [ABSTRACT FROM AUTHOR]

Soil erosion caused by water has been monitored for 17 years on 465 ha cropland in Lower Saxony (Northern Germany). The 86 monitored fields are representative for three different typical agricultural landscapes with an intermediate to high water erosion risk in Northern Germany. The monitoring scheme included regularly conducted erosion damage mapping and cultivation surveys. The collected data encompasses 1275 field years and 1355 mapped erosion systems, giving evidence on the extent, frequency and rate of soil erosion by water. Mean mapped soil loss for all fields was relatively small at 0.85 t ha −1  a −1 . The highest rate for a single field amounted to 7.02 t ha −1  a −1 . Variability of soil loss in time and space was high: annual losses (mean of all fields) ranged between 0.04 and 2.81 t ha −1  a −1 . The highest annual loss on a single field was 53.07 t ha −1 . Every year, at least 24% of the monitored fields were not affected by erosion, only 1.3% of the monitored area eroded at least once a year. Spatial analysis of mapped erosion features shows that the highest soil loss is located in topographically-defined flow paths and in wheel tracks oriented in line of the steepest slope. Cultivated crops and tillage management have a high influence on loss rates ranging from 0.07 for catch crop to 2.78 t ha −1  a −1 for potato. Additionally, the results prove that farmers in the investigation areas were able to significantly reduce soil loss rates of the five most important crops from 0.6 to 0.37 t ha −1  a −1 by using conservation tillage measures. The annual variability in the collected data emphasises the importance of appropriate long-term monitoring programmes to create sound data on the extent, frequency and rate of soil erosion by water at a field to landscape scale. [ABSTRACT FROM AUTHOR]

Intensive cropland soil erosion can be caused by disturbance activities. However, conservation measures have been reported to increase soil resistance and decrease erosion. Hydraulic flume experiments were conducted to measure the detachment rate of disturbed soil samples from a peanut field with five tillage practices. Hydraulic variables were adopted to estimate the soil detachment rate and to quantify the rill erodibility parameter. The disturbed soil detachment rates are substantially greater than those for comparable undisturbed soil experiments. The average disturbed soil detachment rates for the 5 different tillage treatments, from lowest to highest, are as follows: straw mulch (PC) < manure (PM) < peanut and orange intercropping (PO) < peanut and radish crop rotation (PR) < conventional downslope furrows (PF). The conservation measures (PC, PM and PO) have a limited effect on increasing the disturbed soil resistance under low flow energy conditions. Thus, the average rill erodibility is lower, and the critical shear stress is higher for the PC, PM and PO treatments than those of the PR and PF treatments. With a slope gradient steeper than 17.6%, there is no significant difference among the detachment rates of all treatments. A linear function of both flow rate and slope gradient can be used to estimate the disturbed soil detachment rate. Both stream power and flow shear stress are more effective than the unit stream power in predicting soil detachment rates. The stream power is the most effective predictor among the three hydraulic parameters studied. Instead of the power functions, the linear functions of the hydraulic parameters are suggested to quantify the disturbed soil detachment rates. [ABSTRACT FROM AUTHOR]

Multi-scale geospatial and absolute variation of surface and near-surface soil physical and chemical properties can be mapped and quantified by coupling digital soil mapping techniques with high resolution remote sensing products. The goal of this research was to advance data-driven digital soil mapping techniques by developing an approach that can integrate multi-scale digital surface topography and reflectance-derived remote sensing products, and characterize multi-scale soil-landscape relations of Quaternary alluvial and eolian deposits. The study area spanned the arid landscape encompassed by the Barry M. Goldwater Range West (BMGRW), which is administered by the Marine Corps Air Station Yuma, in southwestern Arizona, USA. An iterative principal component analysis (iPCA) was implemented for LiDAR elevation- and Landsat ETM + -derived soil predictors, termed environmental covariates. Principal components that characterize >95% of covariate space variability were then integrated and classified using an ISODATA (Iterative Self-Organizing Data) unsupervised technique. The classified map was further segmented into polygons based on a region growing algorithm, yielding multi-scale maps of soil-landscape relations that were compared with maps of soil landforms identified from aerial photographs, satellite images and field observation. The approach identified and mapped the spatial variability of soil-landscape relationships in alluvial and eolian deposits and illustrated the applicability of coupling covariate selection and integration by iPCA, ISODATA classification of integrated data layers, and image segmentation for effective spatial prediction of soil–landscape characteristics. The approach developed here is data-driven, applicable for multi-scale mapping, allows incorporation of a wide variety of covariates, and maps spatially homogenous soil-landscape units that are necessary for hydrologic models, land and ecosystem management decisions, and hazard assessment. [ABSTRACT FROM AUTHOR]

In simulation studies of soil erosion, analyzing runoff and sediment curves is important for accurately characterizing soil erosion on hillslopes. The objectives of this study were to measure the effects of surface runoff and sediment collection time intervals (CTIs) on runoff and sediment curves and to determine how CTIs affect soil erosion analyses. Experiments were conducted in runoff plots that were 4 m long and 1 m wide. The slope gradient was 15°, and the soil surface was smooth. Rainfall was applied at intensities of 60, 90 and 120 mm/h, and one short CTI (i.e., 2 min) and four longer CTIs (i.e., 4, 6, 8 and 10 min) were used. The results showed that longer surface runoff and sediment CTIs obviously influenced the runoff and sediment curves and the soil erosion analysis results, especially during the early period of runoff. The amount of accumulated runoff decreased at longer CTIs, and the amount of accumulated sediment increased at longer CTIs. Therefore, it is important to choose an appropriate CTI in simulated rainfall experiments to improve the reliability of soil erosion analyses. The use of an inappropriate CTI will adversely affect the results of such analyses. Based on these results, we suggest using a short CTI to collect surface runoff and sediment measurements during the rising period of the runoff rate; longer CTIs should be used only after the runoff rate has reached a steady state because the temporal variations in runoff and sediment yield are lower during this period. [ABSTRACT FROM AUTHOR]

Soil erosion and sediment transport measurement is a time-consuming and difficult step yet important part of hydrological studies. Hence, use of models has become commonplace in estimating soil erosion and sediment transport. In this study, we used an artificial neural network (ANN) to simulate soil erosion rates. A geographic information system (GIS) was used as a pre-processor and post-processor tool to present the spatial variation of the soil erosion rate. The ANN was trained, optimized and verified using data from the Kasilian watershed located in the northern part of Iran. Field plots were used to estimate soil erosion values on the hillslopes. A Multi Layer Perceptron (MLP) network was adopted, where the soil erosion rate was the output variable and the rainfall intensity and amount, air and soil temperature, soil moisture, vegetation cover and slope were the inputs. After the training process, the network was tested. According to the test results, the ANN can estimate soil erosion with an acceptable level (coefficient of determination = 0.94, mean squared error = 0.04). The verified network and its inputs were used to estimate soil erosion rates on the hillslopes. Finally, a soil erosion rate map was generated based on the results of the verified network and GIS capabilities. The results confirm the high potential when coupling an ANN and a GIS in soil erosion estimation and mapping on the hillslopes. [ABSTRACT FROM AUTHOR]

Soil detachment is one of the most important processes of soil erosion, as it is of great significance for the prevention and treatment of soil erosion in areas subject to seasonal freeze-thaw. However, little research on soil detachment capacity (SDC) during the thawing period has been carried out and this process remains unclear. In order to elucidate the effects of slope, flow discharge and freeze-thaw factors on SDC, the indoor artificial freezing-thawing method was applied in combination with scour to simulate the soil detachment process. Signal-to-noise (S/N) ratio analysis was also used to evaluate the experimental results by applying the Taguchi method. The results showed that SDC increased with the increased of slope and flow discharge. As the number of freeze-thaw cycles and moisture increased, SDC initially decreased and then increased. A maximum soil detachment value was achieved at 12° slope and when moisture was 12%, flow discharge was 1.2 L/min, and there were ten freeze-thaw cycles. Statistical analysis with the help of Taguchi method showed that the percentage contribution of the different factors to SDC occurred in order, slope (76.02% at p = 0.002) > flow discharge (13.39% at p = 0.019) > soil moisture (6.92% at p = 0.047) > the number of freeze-thaw cycles (3.67% at p = 0.106), while factors related to hydrodynamic conditions exert a greater influence than those related to freeze-thaw. Finally, the Taguchi and orthogonal analysis methods showed the similar predictive results R 2 = 0.98 and R 2 = 0.97 respectively. However, the Taguchi method was more accurate than the orthogonal analysis methods due to less relative error 8.98% and 15.11% respectively. These results provided a scientific reference for the study of the mechanisms of soil erosion as well as for the applicability of the Taguchi method. [ABSTRACT FROM AUTHOR]

Soil roughness is a key parameter to our understanding of soil properties and soil-water interaction, most of which occur at millimeter scales. Soil irregularities, such as aggregates, clods and interrill depressions, influence water infiltration and overland flow. The objective of this study is to observe and quantify clod evolution under cumulated precipitation. We prepared two soil trays with loose silt soil and pre-sieved clods put on top, at low and high concentrations. These trays were then subjected to a set of five successive artificial rainfalls. The digital elevation models (DEM) were recorded for each tray, at millimetric resolution, at the initial stage and after each subsequent rainfall. The clods were automatically segmented on the DEM and the diameter, surface area and volume of these clods were measured by computer. The isolated clods showed comparable behavior on both trays. The small clods were almost always decreasing in volume until they disappeared. The other clods swelled during the first rain or the first two rains, and then decreased in area and volume. The decrease was faster for volume than for area. This probably reflected a soil detachment phenomenon, which mostly affected the heights of the clods. On the high concentration tray, the close inter-proximity of the clods induced merging and the formation of blocks. The rate of decrease of clod volume as a function of cumulative precipitation could be modeled using exponential and linear equations. Small and intermediate-sized clods showed an exponential decrease that was smoother as the clod size increased. Large clod volume decrease was almost linear. We were further able to model the trend of the slope parameter of the exponential decrease, as a function of clod size. Our study has shown how the DEM recording and image analysis can be used to quantify the evolution of clods under rainfall, improve our understanding of clod dynamics under rainfall and roughness parameterization. The size dependency of clod volume decrease is important for soil conservation decisions. This will obviously affect crust formation, surface armoring, soil erosion and surface permeability to water and gas. [ABSTRACT FROM AUTHOR]

The effect of antecedent soil moisture content on runoff and soil erosion was investigated in many previous studies. These studies revealed contradictory findings. The present study investigated the combined effect of raindrop temperatures and antecedent soil moisture on interrill flow generation and erosion of a loamy soil (Loess), using a rotating disk rain simulator. The experiments were applied to soil with two pre-prepared moisture conditions: hygroscopic and field capacity. For each condition, three rainfall temperatures were applied: 2 (cold), 20 (mid-temperature), and 35 °C (hot). The effect of antecedent soil moisture on soil erosion found to be depended on rainfall temperature. For the cold rainfall, the sediment yield of the dry soil was 5.2 times greater than that of the pre-wetted soil, whereas for the mid-temperature and for the hot rainfall it was 1.5 and 1.2, respectively. For the pre-wetted soil, the sediment yield in the mid-temperature rainfall was 3 times greater than in the cold one. In the light of the predicted changes in global climate characteristics, an increase in rainfall temperature might lead to enhanced soil loss in Loess. [ABSTRACT FROM AUTHOR]

• Land use and land cover classes homogenize within-class differences in vegetation density, type and other characteristics that influence surface erosion. • When these classes are used to estimate current and projected future RUSLE C-factor for native vegetation, this introduces significant error. • Remote sensing methods can be used to assess intra-class variation in C-factor, improving the soil loss estimate. • A strong, predictive relationship exists between remotely-sensed C-factor values and climate. • Current and projected changes in climate can be used to directly estimate C-factor, improving the estimate of current and future soil loss rates. This new method provides a low-cost, efficient and reliable estimate of future C. Understanding how reservoir sedimentation rates may evolve due to climate change is essential for projecting future changes in reservoir water storage capacity. The Revised Universal Soil Loss Equation (RUSLE) is commonly used to assess regional soil loss rates because of its suitability for working with the coarse temporal and spatial scale of climate model outputs. Application of the RUSLE for projecting future erosion rates is constrained by the relatively limited number of classes used in projected changes of native vegetation: this typically reduces a wide range of variation in RUSLE cover (C) factors to a single value per class, and these classes may be insensitive to changes in species composition and canopy density with time and space. This paper develops a low-cost, efficient, and objective approach to projecting future C values directly based on widely available Landsat data, downscaled climate model data, and a limited number of terrain variables. Observed C is estimated from Landsat-derived Normalized Difference Vegetation Index (NDVI) and Modified Soil-Adjusted Vegetation Index (MSAVI) values using standard methods. A linear relationship is established between the observed C values and average annual antecedent temperature, average annual antecedent precipitation, latitude, and percent sand (adjusted R2 = 0.75604, 0.7543, and RMSE = 0.09448, 0.07043, respectively). A proof of principal study demonstrates that, unlike when land cover classes are used to estimates C, a RUSLE model driven by the regression-based C provides a correct order-of-magnitude estimate of observed long-term erosion and sediment yield rates (e.g., an estimate of 2.9–3.2 t ha−1 y-1 is obtained where observed rates range from 1.2 to 3.9 t ha−1 y-1 for the same time period, and up to 8 t ha−1 y-1 historically, while standard formulations of RUSLE yield 16.1 and 0.3 t ha−1 y-1). Using climate model data to estimate both precipitation intensity (R factor) and C in the RUSLE model results in basin wide projected end 21st century soil erosion rates for relative concentration pathway 8.5 of 5.5–7.5 t ha−1 y-1, consistent with expectations for accelerated soil loss in the study area as climate change reduces soil moisture while increasing precipitation intensity. The same model driven by land cover class estimates of C produces soil loss rates an order of magnitude smaller (0.3–0.4 t ha−1 y-1), consistent with a much more heavily vegetated landscape than could be supported under the increasingly arid projected climate. [ABSTRACT FROM AUTHOR]

• Enzymic latch and iron gate were compared to reveal regulators of C in Zoige soils. • Phenol oxidase and Fe2+ were not crucial regulators of C in soils of Zoige Plateau. • The effect of moisture on SOC was remarkably higher than phenol oxidase and Fe2+. • Moisture indirectly affected SOC via adjusting enzymes, phenolics, and Fe oxides. • Fe oxides significantly affected SOC in non-waterlogged but not in waterlogged soils. Due to the enormous amount of carbon (C) stored in peatlands, understanding the regulator of soil organic carbon (SOC) in peatlands is critical for global C cycling. Currently, "enzymic latch" and "iron gate" are the frequently debated mechanisms that propose phenol oxidase (PHO) and Fe2+ as important regulators driving SOC cycling in peatland. Therefore, this study compared "enzymic latch" and "iron gate" in the same peatland (Zoige Plateau, the largest peatland in China) to figure out the crucial regulator of SOC content via investigating the interrelationships among soil properties, C-related enzymes, phenolics, and iron (Fe) oxides. Moreover, waterlogged and non-waterlogged soils were chosen to take samples in both dry and wet season to understand the potential role of moisture in regulating SOC content. It was found that the contents of dissolved organic C, phenolics, SOC, Fe oxides, and β-glucosidase (BG) activities in waterlogged soils were higher than those in non-waterlogged soils. Compared to the dry season, soils in the wet season had higher phenolics, SOC, and Fe oxides contents. Also, this study observed an insignificant relationship between PHO and SOC (p > 0.05) and the small amounts of Fe2+ to total Fe (<2‰) in soils. Meanwhile, the highest effect of moisture (0.89) and negligible effect of PHO (0.04) and Fe2+ (-0.08) on SOC based on pathway analysis suggested that moisture might be the crucial regulator of SOC. Furthermore, pathway analysis implied that moisture could indirectly affect SOC by adjusting BG (p < 0.05) and soluble phenolics (p < 0.05). This study provided valuable information for understanding the importance of moisture in driving C cycling and helping against soil C loss by moisture management in Zoige Plateau. [ABSTRACT FROM AUTHOR]

• The response of soil water content (θg) to vegetation restoration mode varied highly. • θg increased with soil depth and the distance from the ephemeral gully (EG) head. • θg was less on EG top with artificial plant than on EG top with natural plant. • Natural succession is recommended to control soil erosion and maintain soil water. Vegetation restoration in an ephemeral gully (EG) can alter the traits of soil, vegetation, and microtopography, and therefore likely influences soil water. Nevertheless, few results have been reported regarding the response of soil water regime to vegetation restoration modes in EGs in semiarid region. This research was designed to clarify the spatial variation in soil water in an EG with different restoration modes on the Loess Plateau of China. For the selected EG, the two banks of ephemeral gully were well restored by natural succession and artificial planting. Soil water content (θg) was quantified on the ephemeral gully floor (F), natural successional restored ephemeral gully top (NT), and artificial planted restored ephemeral gully top (AT) in both the vertical and longitudinal directions. A sloping farmland was selected as the control. The results revealed that θg increased significantly with soil depth (i.e., 0–1 m) and the distance from the ephemeral gully head (i.e., 0–60 m). In the vertical direction, the mean θg of the six test points of the ephemeral gully floor was 1.1 to 1.2 times greater than that of the control in each soil layer, while the mean θg of the six test points of NT and AT decreased by 12.3 % to 15.6 % and 29.2 % to 29.9 % compared to the control in each soil layer. Along the longitudinal direction, the θg (i.e., 0–1 m soil layer) abided by the pattern of F > NT > AT. The difference in θg between the three ephemeral gully units and their variations in the vertical and longitudinal directions were mainly driven by the variations in soil clay content, bulk density, organic matter content, plant root density, plant litter density, and the distance from the ephemeral gully head. The findings are useful to clarify the spatial variation in soil water and to select a reasonable vegetation restoration mode on hillslopes in semiarid regions. [ABSTRACT FROM AUTHOR]

Soil aggregate stability is a key factor in soil resistance to water erosion, which is a threat to soils in a large part of northern Tunisia. The analysis of the spatial variability of soil aggregate stability provides both agronomic and environmentally useful information. However, extensive measurements of soil aggregate stability remain tedious and expensive. This study explores two different approaches as alternative to measurements of soil aggregate stability. One approach estimated aggregate stability via laboratory measurements of soil elementary properties using multiple linear regressions known as pedotransfer functions. The second approach, which is methodologically innovating, was based on the geological pattern as a proxy for aggregate stability using regression-kriging analysis. A set of 113 soil samples from an 800 km 2 agricultural region that included the Lebna watershed (Cap Bon, Tunisia) were collected from the soil surface layer (0–10 cm depth). Samples were analyzed for elementary properties (i.e., soil texture, total carbon and nitrogen, iron, CaCO 3 , salinity, CEC and pH) and for soil aggregate stability according to the normalized method (ISO/DIS 10930, 2012), which considers three indexes (MWD) calculated for three contrasted wetting conditions and disruptive energies. Most soils in the study area were non-salted with an alkaline pH and relatively low organic carbon content. Of the soils, 35% were clay soils, and 55% had a balanced soil texture. The average of the three soil aggregate stability indexes (MWD mean ) ranged from 0.38 to 2.80 mm, and this property showed large variability from instable soils to very stable ones. Analysis of pedotransfer functions determined that the best predictor variables for soil aggregate stability were silt, organic matter and iron. Geostatistical analyses at the regional scale showed spatially structured soil aggregate stability (variograms with sills reaching a 5 km distance). Using geological information as ancillary data, the prediction of soil aggregate stability with regression-kriging was similar to that of pedotransfer functions. A regression-kriged map of soil aggregate stability associated with a map of prediction uncertainties was developed. The resulting maps and methods of this study can be useful in the development of management options that minimize water erosion risks in the studied area. [ABSTRACT FROM AUTHOR]

The proportionality between raindrop-driven soil erosion delivery and area of soil exposed to raindrops under a uniform precipitation rate was investigated in terms of individual size classes using laboratory flume experiments. In particular, we examined the dependence of soil erosion on the area exposed to raindrop detachment. Twelve experiments were performed on the same laboratory flume, filled with the same soil. The experiments entailed different (constant) precipitation rates (28 and 74 mm h − 1 , 2–5 h duration) and various fractions of exposed surface (20, 30, and 40%, created using rock fragment cover). In addition, different initial soil conditions (dry hand-cultivated, wet sealed-compacted and dry compacted) were considered. The discharge rates and the sediment concentrations of seven individual size classes (< 2, 2–20, 20–50, 50–100, 100–315, 315–1000 and > 1000 μm) were measured at the flume exit. Results showed that the proportionality of soil erosion to the area exposed appears to always hold at steady state independently of the initial conditions and rainfall intensity. Across all experiments the data indicate that this proportionality holds approximately during entire erosive events and for all individual size classes. However, the proportionality for short times is less clear for the larger size classes as the data show that for these classes the erosion was sensitive to the soil's antecedent conditions and further influenced by additional factors such as surface cohesion, surface compaction and soil moisture content. [ABSTRACT FROM AUTHOR]

• Decadal changes in soil water-holding capacity were assessed using field surveys. • Soil erosion and climate change decreased soil water-holding capacity. • The decline in soil water-holding capacity could exacerbate vegetation degradation. Environmental changes on the Tibetan Plateau could affect not only the livelihoods of local people but also the food and environmental security of downstream people. Soil water-holding capacity (WHC) governs soil functioning in ecosystems, could be significantly altered by the accelerated climate change and vegetation degradation experienced by the Tibetan Plateau's alpine ecosystem. However, it remains unclear regarding the direction and magnitude of this feedback. Here, we assessed the responses of WHC to the combined impacts of climate change and vegetation degradation across the Tibetan Plateau over the past decades based on a regional resampling campaign, including 148 well-matched sampling sites, conducted in the 1980s and 2020. We observed an overall decrease in the WHC in the study area in response to a warmer climate and increased soil erosion. The decrease in the topsoil (notably 0–20 cm) was more significant than that in the subsoil (notably 20–50 cm). Average soil available water content (AWC) decreased from 0.13 to 0.10 cm3 cm−3 (p < 0.0001) for topsoil, and from 0.10 to 0.09 cm3 cm−3 (p < 0.01) for subsoil. The changes in AWC were primarily explained by soil erosion (11.3 %) and climate change (9.2 %). Furthermore, the decline in AWC results in a significant decrease in soil productivity, which may exacerbate vegetation degradation and increase the susceptibility of alpine ecosystems to disturbances. These findings suggest that soil erosion control is still an urgent task for environmental protection on the Tibetan Plateau and that increasing WHC is an important goal of adaptation measures. [ABSTRACT FROM AUTHOR]

• The soil sensitivity to erosion differed depending on the erosive force applied. • Different soil properties affected the soil sensitivity for water and wind erosion. • The sensitivity of the soils to erosion was higher for wind than for water erosion. Erosion by water and wind can seriously deteriorate soil quality. Traditionally, these two types of erosion have been studied and modelled separately. The main goal of this study was to explore the sensitivity of two Mediterranean soils to both water and wind erosion, in terms of their properties and aggregation. Targeted laboratory experiments were performed using wind and rainfall simulators. Different soil properties and aggregation indices were analyzed for each soil sample. Comparing the rates of soil loss to water and wind erosion revealed an opposite trend in soil sensitivity to these erosional forces; the soil that was most sensitive to erosion by one force was least sensitive to erosion by the other force. This indicates that soil erosion is strongly dependent on the erosive force (water or wind). Therefore, soil erodibility cannot be an unequivocal definition for a certain type of soil, but rather depends on the erosional force applied. Our results also demonstrate that different soil properties affect the size and stability of soil aggregates, controlling the rate of soil loss to water erosion or wind erosion. Under rainfall simulations, the sodium adsorption ratio (SAR) was the main factor controlling soil sensitivity to water erosion (r 2 = 0.76), while loose erodible material (LEM) was the only factor controlling soil sensitivity to wind erosion (r 2 = 0.69). Since dynamic soil properties (e.g., LEM) tend to change over shorter periods of time than intrinsic soil properties (e.g., SAR), the potential for a general increase in the sensitivity of Mediterranean soils to wind erosion processes is expected to be greater than the potential for a general increase in the sensitivity of these soils to water erosion. The calculation of a sensitivity-normalized value for each soil sample revealed that the examined soils were more sensitive to wind erosion than to water erosion. [ABSTRACT FROM AUTHOR]

Plant litter can be incorporated into topsoil under natural circumstances by soil splash, sediment deposition, and soil-dwelling animal activities. The incorporated litter can change the mechanical properties of soil and the decomposition of the incorporated litter can improve soil structural stability. Those changes likely influence soil detachment process by overland flow. This study was undertaken to quantify the effects of incorporated plant litters into topsoil on the temporal variation in soil resistance to detachment by overland flow using natural soil samples collected from four different plots (one control and three litter incorporation treatments) and then scoured under six different flow shear stresses in a hydraulic flume. The experiment started from April 19 to October 5, 2015 for 10 times at approximately 20 days sampling intervals. Soil properties and environmental parameters were also measured at each sampling time to explain the temporal variations in rill erodibility and critical shear stress. The results showed that the incorporated plant litter was effective to enhance soil resistance to flowing water erosion. Compared to bare soil, rill erodibilities of litter incorporated soils of black locust, sea buckthorn, and green bristle grass decreased by 24.3%, 33.5%, and 34.8%. The temporal variations in rill erodibility of bare and litter incorporated soils were similar. Rill erodibility decreased significantly over time as an exponential function for both bare and litter incorporated soils. The relative rill erodibility of three litter incorporated soils increased over time as a power function. The fitted critical shear stress increased exponentially over time. The temporal variations in rill erodibility could be explained by the temporal variations in soil consolidation, water stable aggregate, and litter decomposition. Rill erodibility could be well estimated by soil bulk density, water stable aggregate, and litter mass density ( r 2 = 0.92). [ABSTRACT FROM AUTHOR]

Water erosion is the main cause of soil degradation on cultivated lands under Mediterranean climate. In these conditions, ephemeral gully erosion (EGE) is a major contributor to loss of soil productivity due to the big amounts of soil removed from the most productive top-layer. However, only a few studies on the effects of EGE and artificial controlling measures on soil degradation are available. The objective of this study was to assess the impact of EGE combined with soil infilling by tillage on several physicochemical soil properties related to soil fertility and productivity through the calculation of a soil quality index (SQI) by means of a statistical approach. It was hypothesized that the sites affected by this process of erosion and infilling of ephemeral gullies (EGs) exhibit considerable changes in the soil properties compared with locations that do not undergo this process. The study site consisted of 5 fields with contrasting soil properties which have been continuously cultivated with winter wheat. The site, located in the internal area of Sicily (Italy), represented a typical Mediterranean arable land and was severely affected by EGE. A set of soil samples were collected to investigate the spatial variation of the SQI across each location: 12 sample points in the EGE area; 4 samples in the deposition zone; 4 reference points in the area unaffected by EGE. The SQI was estimated by closely monitoring a set of main chemical and physical soil variables which influence soil fertility status: particle size (sand, silt and clay content), bulk density, gravimetric moisture, pH, electrical conductivity, carbon content (inorganic, organic and total), nitrogen content (ammonium, nitrate and total) and available phosphorus. The results showed that channelized erosion posed a threat to soil quality status even at a single cultivated field's level; therefore, the soil's ability to sustain crop production is expected to be compromised in the long run. Reductions of the SQI were observed at the EGs system area and at the deposition area in every EGs. Besides that, the lowest values of SQI were obtained inside the EGs channel and in the nearby soil areas, which were generally used to fill those channels. Soil degradation occurred in the areas which were subjected to EGE and infilling process, with key soil properties being clay (CC), sand (SaC), silt (SiC), and total organic carbon (TOC) contents. This approach helps to understand the impacts of EGE and its controlling measures on soil degradation in Mediterranean agricultural fields. [ABSTRACT FROM AUTHOR]

• Soil erosion was measured by detecting changes in air–soil interface of TDR probe. • Feasibility of TDR-based soil erosion measurement was evaluated by experiments. • Soil erosion can be effectively measured within a wide soil moisture range. • Simultaneous measurement of soil moisture content can ensure reliability. Scientific research and control technology of soil erosion both rely on accurate and efficient soil erosion measurements. Based on the principles of locating interfaces in layered media and measuring dielectric properties by time domain reflectometry (TDR), we developed TDR-based measurement of changes in the air–soil interface along the TDR probe for soil erosion measurement, and simultaneously measuring volumetric soil moisture content (θ v). Part of a three-rod TDR probe was inserted in the soil and the rest exposed to air, so changes in the air–soil interface could be denoted by changes in the length of exposed probe (L air). TDR waveforms were analyzed using a combination of tangent line method and second-order bounded mean oscillation methods to identify time points at positions of impedance discontinuity in electromagnetic propagation, then converting these data to L air and θ v by calibrated equations. According to the laboratory experiment using sandy loam and silt loam, L air could be effectively measured within a wide soil moisture range by the calibrated equation and the thickness of the eroded soil layer could thus be determined. The RMSE of θ v measurement ranged between 0.003 and 0.025 cm3 cm−3, which enabled the identification of the appropriate soil moisture range for measuring L air , and achieve reliable simultaneous measurement of soil erosion and soil moisture content. The simulated rainfall experiment using sandy loam and silt loam and field scouring experiment conducted in loam also indicated that the proposed method could achieve high measurement accuracy in erosion environments, for which L air with the RMSE from 1.8 to 2.1 mm and θ v with the RMSE from 0.007 to 0.024 cm3 cm−3. The proposed method has various advantages, including versatility, minimal disturbance, easy automation of measurement at multiple positions, etc., could serve as a new technical option for soil erosion measurement, and extend the utilization of TDR. [ABSTRACT FROM AUTHOR]

Decreases in the water retention function of various artificial disturbed landform units (DLUs) caused by urbanization activities, compared to original landform units (OLUs), are the main factor that causes urban water and soil loss and the aggravation of urban floods under certain rainfall conditions and specially designed drainage network capabilities. Field investigations, laboratorial analyses of soil physical properties and analytic hierarchy process (AHP) composite methods were performed to comprehensively analyse the effects of various DLUs on the water retention function of OLUs. The results indicated as the following: (і) The > 5 mm particle content (> 54%) for various DLUs was higher than that for OLUs (lower than 3%); the natural repose angles of soil-rock mixtures (32–37°) and soil bulk density (1.41–1.74 g/cm 3 ) in the DLUs were all higher than those in the OLUs (30–31°, 1.18–1.14 g/cm 3 ); and the uniformity coefficients and curvature coefficients were 10.00–80.00 and 3.24–5.70 in the DLUs and 6.00–75.00 and 0.17–2.50 in the OLUs, respectively. (ii) The soil steady state infiltration rate in the DLUs decreased from disturbed soil accumulation with 2 months (DSA 2m , 15.00 mm/min) to disturbed soil accumulation with 2 years (DSA 2a , 5.63 mm/min), disturbed soil accumulation with 4 years (DSA 4a , 3.82 mm/min), the slope greening belt (SGB, 1.24 mm/min), and construction roads (CR, 0.51 mm/min). The conversion from forests to DSA 2m had the greatest impact on the soil infiltration capacity and soil storage capacity, while the conversion to CR had the lowest impact. (iii) The total reservoir storage in the DLUs' soil was ordered as follows: DSA 4a > SGB > DSA 2a > DSA 2m > CR. The conversion process from grass to CR exerted the greatest impact on storing water and regulating the overland flow. (iv) The water retention functions in the DLUs were all weaker than those in the OLUs: DSA 2m was the weakest (0.287), while paddy fields were the strongest (0.668). Thus, the occupied areas of urban water surfaces (e.g., lakes, rivers and ponds), forests and grassland and their spatial distribution during urbanization must be carefully considered. These results could help to understand the ecological service functions of urban soil and water conservation, provide relevant knowledge to landscape rehabilitation, alleviate urban floods during urban development and recover the functions of soil and water conservation ecological services in project areas during the urbanization construction process. [ABSTRACT FROM AUTHOR]

Soil water erosion on cultivated lands represents a severe threat to soil resources in the world, and especially in Mediterranean areas, due to their topographic, edaphic and climatic conditions. Among the cultivated lands, vineyards deserve a particular attention because, aside representing one of the most important crops in terms of income and employment, they also have proven to be the form of agricultural use that causes one of the highest soil losses. Although the topic of soil water erosion on vineyards has been studied, it still raises uncertainties, due to the high variability of procedures for data acquisition, which consists into different scales of analysis and measurement methods. There is still a great gap in knowledge about the effect of triggering factors on soil water erosion and, so far, an effort to quantify this effect on the Mediterranean viticulture has not been made yet. Therefore, this paper review aims to (i) develop a documented database on splash, sheet and rill erosion rates in Mediterranean vineyards, (ii) identify and, if possible, quantify the effect of triggering factors such as topography, soil properties, rainfall characteristics and soil conservation techniques on soil water erosion, and (iii) provide suggestions for a more sustainable viticulture. Although the large variability of data, some general trends between erosion rates and triggering factors could be found, as long as data were categorized according to the same measurement method. However, no general rule upon which to consider one triggering factor always predominant over the others came out. This paper review supports the importance of monitoring soil water erosion by field measurements to better understand the relationship between the factors. However, protocols should be established for standardizing the procedure of collecting data and reporting results to enable data comparison among different study areas. [ABSTRACT FROM AUTHOR]

Aims Antecedent soil water content (ASWC) is an important factor affecting soil water infiltration, runoff and soil erosion on slopes but it is difficult to measure or forecast accurately and is not often reported in soil erosion databases. Methods Runoff plots (12 m × 5 m) were used to collect runoff and sediment during the rainy seasons between April 2010 and October 2013 on the Loess Plateau, China. The HYDRUS-1D model was calibrated and tested using the data collected from the plots. The relationships of ASWC with runoff and sediment yield were investigated using the model output values for ASWC. Results The model performance was satisfactory, with a mean Nash–Sutcliffe model efficiency coefficient of 0.411 and a root mean square error of 0.031 during the four study years. Runoff was directly affected by rainfall amount and rain intensity. Furthermore, runoff typically increased with ASWC. Conclusions HYDRUS-1D can provide temporal ASWC data that could be used for runoff prediction. [ABSTRACT FROM AUTHOR]

Plants in many sand dune systems experience arid-like conditions due to low water capacity and high hydraulic conductivity of sand grain medium. Here, water availability was studied in coastal sand dunes in a Mediterranean climate on which the dominant species is a desert dwarf shrub, Artemisia monosperma . Special emphasis was put on landscape heterogeneity and contrasts between dune stabilisation states and microhabitats, conditions after rain events and in the dry season and catenary profiles. During the approximately 150 day-long dry season, as well as during multiple dry spells in the rainy season, soil water content at 50 cm depth was below permanent wilting point in both mobile and stabilised dunes. The open matrix between the A. monosperma dwarf shrubs was characterised by higher hydraulic conductivity and soil water content compared with soil under A. monosperma dwarf shrubs, and played an important role in supporting the dwarf shrubs. In the mobile dunes, in which there is greater open matrix area, this has resulted in higher soil water content in the dunes that increases into the adjacent interdunce, while the opposite was found in the stabilised dunes. The dominance of A. monosperma is thus related to its ability to utilise water from the open matrix, and its distribution is driven by source–sink relations between the open matrix and A. monosperma dwarf shrubs, respectively. In stabilised dunes, A. monosperma dwarf shrubs increase in size and total percentage cover, reducing water-contributing open matrix area and probably increasing competition over water. As a result, the spatial distribution pattern of A. monosperma dwarf shrubs is regular, maintaining a certain degree of open matrix to support the living dwarf shrubs, which theoretically cannot achieve a full coverage of the dune surface in this Mediterranean system. [ABSTRACT FROM AUTHOR]

• Soil detachment capacity and rill erodibility decreased during growing season. • Rill erodibility (K r) decreased as an exponential function of root density. • Soil detachment capacity was simulated by shear stress, soil cohesion, bulk density, and root length density. Near soil-surface characteristics change significantly with crop growth in sloping farmlands and thereby induce the temporal variations in soil detachment by rill flow. In this study, variations in soil detachment capacity by rill flow (Dc) and soil erosion resistance to rill flow as reflected by rill erodibility (K r) and critical shear stress (τ c) during crop growth stages were quantified in sloping farmlands of the Loess Plateau, China. The soil samples were collected from four different plots (one control and three crop plots—soybean, corn, and millet) and subjected to flume experiments under different shear stress (τ) levels (5.16–15.61 Pa). The near soil-surface characteristics including soil moisture content (SMC), soil bulk density (BD), soil cohesion (Coh), mean weight diameter (MWD), soil organic matter content (SOM), root length density (RLD), root surface area density (RSAD), and root mass density (RMD), were measured to explain the variations in soil detachment during crop growth stages. The results showed that SMC fluctuated greatly, whereas BD, Coh, MWD, SOM, RLD, RSAD, and RMD increased gradually with crop growth. Measured Dc and fitted K r significantly decreased with crop growth during one growing season. The mean values of Dc for soybean, corn, and millet decreased by 61.19–67.23%, K r decreased by 55.53–61.36%, and τ c increased by 16.0–18.31% compared to those for the bare soil control. The decrease in Dc and K r were significantly affected by BD, Coh, SOM, MWD and RLD, RSAD, and RMD (p < 0.01). Seasonal variations in Dc were well simulated by τ , BD, Coh, and RLD (R 2 = 0.96, NSE = 0.96). The findings demonstrate that it is essential to consider the seasonal variations in soil detachment for optimizing soil and water conservation measures in sloping farmlands. [ABSTRACT FROM AUTHOR]

• Soil moisture had different impacts on critical shear stress and rill erodibility. • Rill erodibility and critical shear stress were measured using hydraulic flume. • Rill erodibility and critical shear stress were not constant for all soil types. Antecedent soil moisture is known to exert a complex, perhaps controversial, effect on rill erodibility and critical shear stress. To understand their dynamic nature as a function of antecedent soil moisture, the rill erodibility and critical shear stress for sandy loam and silty loam soil, representing coarse-grained and fine-grained soil, respectively, were measured using a hydraulic flume under six antecedent soil moisture contents, i.e., 3, 6, 9, 12, 15, and 18%. The results show that antecedent soil moisture had a different effect on critical shear stress and rill erodibility for the two different soil textures. As antecedent soil moisture increased, rill erodibility for the fine-grained soil first increased and then decreased, whereas for coarse-grained soil, rill erodibility exhibited a decreasing pattern. Conversely, as the antecedent soil moisture increased, the critical shear stress decreased first and then increased for the fine-grained soil, but for coarse-grained soil, the critical shear stress decreased after a slight increase. These different patterns can be interpreted by aggregate slaking, capillary force, soil cementation, and water separation. However, when the patterns of critical shear stress and rill erodibility were neglected, the differences in critical shear stress and rill erodibility between the coarse- and fine-grained soils were not statistically significant (P < 0.05). Therefore, indiscriminate treatments of critical shear stress and rill erodibility for different textural soils under changing antecedent soil moisture regimes may cause errors in soil erosion modeling. The relationship between rill erodibility and critical shear stress for coarse- and fine-grained soils could be fitted by a power and a polynomial function, with R 2 value of 0.94 and 0.78, respectively. Future work should include additional soil textures to study the influence of soil physical characteristics in combination with antecedent soil moisture on soil erosion. [ABSTRACT FROM AUTHOR]

• Rock fragment cover effectively curbed soil erosion only when fragment size < 12 cm. • Runoff and soil loss were primarily enhanced when fragment size ≥ 12 cm. • Soil loss of large rock fragments rose with coverage up to 45% and then declined. The presence of rock fragments can change land cover and thus profoundly perturb soil erosion process. This study aimed to identify the effects of rock coverage on soil erosion, and how such effects were influenced by rock fragment sizes. A series of simulated rainfall experiments were applied to erosion plots with two initial soil moisture contents (dry run and wet run), under rock fragment coverage (15%, 30%, 45%, 60%) composed of eight different fragment sizes (0.7, 1.1, 3.0, 5.5, 12.0, 18.8, 26.4, 36.0 cm) from May to September in 2021. The results show that total runoff and sediment concentration increased with rock fragment size. When rock fragments with the sizes were less than 12.0 cm, the total runoff and sediment concentration were respectively 0.81–16.02% and 16.45–50.88% lower than the bare soil. Consequently, the soil loss decreased exponentially with rock fragment coverage. When rock fragment with the sizes were large than 12.0 cm, they decreased sediment concentration by 7.91–33.32% in the dry run, but increased the total runoff by 0.26–10.28% and sediment concentration by 9.33–82.91% in the wet run. As a result, the soil loss ratio firstly enhanced as rock fragment coverage up to 45% and then declined at the rock fragment coverage of 60%. Our findings demonstrate that the effects of rock fragment coverage on soil erosion are rock fragment size dependent. This can help to better parameterize the effects of rock fragment coverage in current soil erosion models, in turn providing guiding information for soil erosion control in stony regions. [ABSTRACT FROM AUTHOR]

Background Ephemeral gully erosion is an important form of hillslope erosion all over the world. It is of high significance to understand its erosion mechanism. Objective A new volume replacement method is proposed to determine ephemeral gully erosion process. Styrofoam particles of hard granules were used to refill the eroded ephemeral gully sections lined with gauze sheet to the original elevation, before their volumes were measured for estimating sediment concentration distribution along the ephemeral gully. The measurement and the computational methodologies are illustrated in details. Method A series of flume experiments were conducted with a silt loam (loess) soil to study ephemeral gully erosion process under four slope gradients and three flow rates. The ephemeral gully was pre-formed before each experimental run. The volumes of the eroded ephemeral gully sections were measured and the distribution of sediment concentration along the gully was computed at 1 m intervals. For comparison purpose, the sediment concentration distribution along the eroded gully was also measured by manual sampling of the sediment-laden water flow with cups. Results The results showed that both the sediment processes estimated by the volume replacement and measured by the sampling method were very similar. The estimated and measured sediment concentrations increased with ephemeral gully length under a given flow rate. The increase rate decreased gradually as the sediment concentration gradually approached its limit. Conclusions Under different flow rates and slope gradients, the sediment concentrations at different distances, as estimated by the volume replacement method were about the same as those measured with the sampling method. The new method provides a useful and efficient way in determining the ephemeral gully erosion, and helps to understand ephemeral gully erosion process. [ABSTRACT FROM AUTHOR]

Many slope failures have been observed in the mountainous environments of the world due to rainfall events. However, studies related to the correlation of rainfall intensity, sliding initiation time and the position of slip surface head are still lacking. Studies on the mechanisms of retrogressive slope failure that may occur in a series and the down-slope displacement of failure mass are also rare. In this study, slope failure experiments were performed using medium-grained silica sand S6 to prepare the model slope in a 5 m long, 30 cm wide and 50 cm deep rectangular flume. The experiments consisted of detailed observations of failure process consisting series of failures successively, with particular emphasis on the time of failure; shape, size and position of the slip surface; and final shape of the model slope after down-slope displacement of the failure masses. Moisture profiles at different points within the model slope soil domain and the profile of surface-water forefront were also reported. The observations showed that the slope failure initiating once at the region near the toe results in successive sliding failures in a series, thereby propagating an unstable zone toward the up-slope. When the slope failure initiates at the region toward the head reach, the successive failures may propagate toward the down-slope first, and then again toward the up-slope. This study also noticed a strong correlation between rainfall intensity, sliding initiation time and the position of its slip surface head. The relationship might depend on the shape and size of the model slope and the type of material used in the formation of the model slope. However, the results indicate the possibility of finding a relationship among rainfall intensity, sliding initiation time, and the position of its slip surface head in a natural slope failure prone zone. A landslide model test and application in real field, based on the similarity theory, may reveal the relationship more realistic. Then it would have a significant impact on policy making to mitigate the probable catastrophe during extreme rainfall-induced landslide disaster. [ABSTRACT FROM AUTHOR]

• ERT correlates well with FDR and helps reveal spatial subsurface heterogeneities. • Soil freezing depth in an undulating terrain varies with slope aspects. • Local terrain heterogeneities affect soil erosion initiating processes. The occurrence of freeze–thaw cycles modifies water infiltration processes and surface runoff generation. Related processes are complex and are not yet fully investigated at field scale. While local weather conditions and soil management practices are the most important factors in both runoff generation and surface erosion processes, local terrain heterogeneities may significantly influence soil erosion processes in catchments with undulating terrain. This paper presents a field-based investigation of spatial and temporal heterogeneities in subsurface soil moisture and soil temperature associated with freezing, thawing, and snowmelt infiltration. The field setup consists of a combination of traditional point measurements performed with frequency domain reflectometry (FDR) and electrical resistivity tomography (ERT). The transect was approximately 70 m long and spanned an entire depression with a north-facing slope (average slope of 11.5%) and a south-facing slope (average slope of 9.7%). The whole depression was entirely covered with stubble. Observed resistivity patterns correspond well to the measured soil moisture patterns. During the observation period, the north facing slope froze earlier and deeper compared with the south facing slope. Freeze–thaw cycles were less pronounced in the north-facing slope than in the south-facing slope. There were also differences in soil temperature and soil moisture patterns between lower and upper parts of the monitored depression. These indicate that initiation and development of runoff related processes, and consequently soil erosion, in regions with freeze–thaw cycles may differ significantly depending on local terrain characteristics. Consequently, it indicates that spatial terrain heterogeneities, especially slope aspects, may be important when studying soil erosion processes, water flow and nutrient leaching in lowlands where patchy snowpacks and dynamic freeze–thaw cycles are predominating. [ABSTRACT FROM AUTHOR]

[Display omitted] • Net water soil erosion in the large, trans-landform river basin, was evaluated. • The dominant factors were identified using the RUSLE-TLSD model and geodetector. • The interaction between slope and NDVI can explain 46% of soil erosion distribution. • NDVI change dominated the temporal dynamic of net soil erosion during 1982–2019. Soil erosion leads to land fertility reduction and land degradation, which threaten food and ecological security. Therefore, it is fundamental for soil erosion risk control to accurately assess the dynamics of water soil erosion and reveal its driving mechanism. This paper aims to integrate and calibrate the transport limited sediment delivery (TLSD) function with the revised universal soil loss equation (RUSLE) model, and then to simulate the long-term soil erosion by water in the upper reaches of the Yellow River Basin (UYRB) and estimate the influence of each factor on soil loss using the GeoDetector method. The results reveal that the water erosion dynamics in the UYRB were reliably simulated by the RUSLE-TLSD model (with the Nash-Sutcliffe efficiency coefficient surpassing 0.809). From 1982 to 2019, the net soil loss rates ranged from 1.63 to 5.41 t⋅ha−1⋅a−1 in the UYRB, with the most intense erosion occurring from June to August. Steep hillside grasslands, especially in the canyon zone with fragmented topography, suffered from intense erosion, while river valleys and the feet of steep slopes experienced sediment deposition. Major factors that impact the distribution of water erosion in the UYRB include the slope followed by vegetation (soil erosion risk should be monitored on steep grasslands with slopes greater than 15°), and the combination of the two represents the core interaction factor, which explained at least 46% of the water erosion distribution. The annual net water erosion in the UYRB showed a slight increasing trend from 1982 to 2000, which was mainly affected by natural factors, but significantly decreased after 2000, which was mainly caused by vegetation restoration. In the UYRB, the implementation of the "Grain to Green Program" has had significant benefits in terms of water and soil conservation, and forests have a greater ability to control erosion than grasslands. [ABSTRACT FROM AUTHOR]

[Display omitted] • Laboratory testing and quantification of soil erosion. • Effects of topography on runoff, sediment yield and water and soil loss regulations. • For sediment yield and water and soil loss, topography has the greatest influence. • Anti-S-shaped slopes exhibit favorable erosion resistance. Due to frequent severe mining activities and globally destructive extreme storms, soil and water loss in open-pit coal mine dumps is extremely serious. To investigate the effect of topography on soil erosion, rainfall with a constant intensity of 1.50 mm·min−1 was conducted on topography models for 60 min. We investigated the effects of 4 topographies (straight slope, concave slope, S-shaped slope and anti-S-shaped slope) and 4 slope gradients (20°, 25°, 30° and 35°) on runoff, sediment yield, and soil and water loss. The results show that the 25° slope gradient was not conducive to infiltration, but the S-shaped slope was favorable. The runoff and sediment yield increased rapidly, then fluctuated upward in a certain range and eventually stabilized with increasing rainfall duration. With increasing slope gradient, the total runoff decreased exponentially, the total sediment yield decreased linearly, and the total amount of water and soil loss declined continuously. The initial runoff time results exhibited the order of anti-S-shaped slope > straight slope > concave slope > S-shaped slope, but the stable runoff size satisfied the S-shaped slope > straight slope > concave slope > anti-S-shaped slope. The results of the significant degree of influence of topography on sediment yield and water and soil loss exhibited the order of anti-S-shaped slope > S-shaped slope > straight slope > concave slope and S-shaped slope > straight slope > concave slope and anti-S-shaped slope. The effect of slope gradient on soil humidity and runoff was more significant than that on topography and their interaction (p < 0.001). Nevertheless, for sediment yield and water and soil loss, topography had the greatest influence (p < 0.001). Notably, the total amount of water and soil loss on the anti-S-shaped slope was relatively minimal. [ABSTRACT FROM AUTHOR]

Abstract: Highly weathered soils in humid Asia are characterized by low soil fertility and high soil erosion potential. This study evaluates the influences of biochar made from the waste wood of white lead trees (Leucaena leucocephala (Lam.) de Wit) on the physicochemical and biological properties of long-term cultivated, acidic Ultisol. This study used three application rates (0%, 2.5%, and 5% (wt/wt)) of the biochar with an incubation time of 105d for all cases. Soils were collected at 21d, 42d, 63d, 84d and 105d during the incubation period to evaluate changes in soil properties over time. A simulated rainfall event (80mmh−1) was performed to estimate soil loss for all treatments at the end of the incubation time. Experimental results indicate that applying biochar improved the physicochemical and biological properties of the highly weathered soils, including significant increases in soil pH from 3.9 to 5.1, cation exchange capacity from 7.41 to 10.8cmol (+) kg−1, base cation percentage from 6.40 to 26.0%, and microbial biomass carbon (MBC) from 835 to 1262mgkg−1. Compared with the control (i.e., no biochar), biochar application decreased bulk density from 1.4 to 1.1Mgm−3, increased Ksat by 1.8 times and increased the mean weight diameter (MWD) of soil aggregates from 2.6cm to 4.0cm. Incorporating biochar into the soil significantly reduced soil loss by 50% and 64% at 2.5% and 5% application rates, respectively, compared with the control. The formation of macroaggregates in the biochar-amended soils is the critical factor to improve soil erosion potential. Based on these results, a 5% application rate of biochar is considered as suitable for highly weathered soil because this application rate efficiently improves soil physiochemical properties and reduces soil loss. [Copyright &y& Elsevier]

Abstract: This study addressed the impacts of contrasting pre-fire ground preparation operations on post-fire runoff and inter-rill erosion in six eucalypt plantations in north-central Portugal, with a special emphasis on the role of soil water repellency in the seasonal patterns of overland flow generation. To this end, a down slope ploughed, a contour ploughed and a terraced site were compared with three unploughed sites. Runoff and erosion data were collected in the field by carrying out rainfall simulation experiments (RSEs) with two intensities (45–50 and 80–85mmh−1) at six occasions during the first one to two years following wildfires in 2005 and 2006. Overall runoff coefficients varied markedly amongst the six study sites and between the two intensities (7 to 55%). While runoff figures were comparable to those of prior RSE studies in recently burnt areas, overall sediment losses were comparatively low (7–155gm−2) but contained a substantial organic matter fraction (29–74%). Apparently, the inter-rill erosion rates were essentially sediment-limited, fitting in with the long history of intensive land use that is typical in the Mediterranean Basin. The hydrological and erosion impacts of the three pre-fire ground preparation operations were minor, probably because these operations took place several years before the latest wildfire. Overall, the two rainfall intensities produced the expected differences but this effect was only statistically significant for simultaneous RSEs. Furthermore, the effect of rainfall intensity varied markedly between the study sites and, occasionally, between the two plot pairs at the same site. This impeded an erosion risk ranking of the six study sites that was consistent for both rainfall intensities. Runoff and erosion rates did not decrease in a simple or pronounced manner with time-since-fire. These temporal patterns could in part be attributed to changes in soil water repellency but other factors were involved as well. Removal of the protective soil cover by litter in particular appeared to play a key role in the increase in sediment losses following logging and wood extraction. [Copyright &y& Elsevier]

Abstract: The study of soil water repellency has received increasing attention by the scientific community in recent years since it has been found to be a much more widespread property than previously thought and significant impacts on soil hydrological processes and erosion have been identified. In addition to these, soil water repellency has many other important consequences for soil functioning, fertility and ecological processes. As a result, researchers focusing on soil water repellency include not only soil scientists, but also those from other disciplines, such as ecologists, physicists, geomorphologists and engineers. Because of its importance and the relative ease of its detection, its study is becoming increasingly recommended to be included as part of standard soil analyses and for soil conservation and restoration works. One of the major research topics in the study of water repellency is the prediction of its occurrence through its relationship with key soil properties such as texture, organic matter content and chemical characteristics, acidity, mineralogy of the clay fraction and microbiology. Relationships between soil water repellency, soil management, water content and temperature have also been a major focus. In this introduction to this special issue, we aim to summarize, evaluate and set in context some of the latest advances, new ideas and trends that are presented by the papers in this special issue and identify the remaining key gaps in the current research on soil water repellency. [Copyright &y& Elsevier]

Abstract: Soil and carbon redistribution on arable land and the associated impacts on carbon sequestration and mineralisation may play an important role in the global carbon cycle. While our insight in the process-chain of erosion, transport and deposition has significantly grown over recent years, there are still major gaps in understanding making it difficult to make an overall assessment of erosion processes on carbon exchange between the soil and the atmosphere. One issue is the potential effect soil degradation and erosion processes may have on CO2 effluxes at eroding sites. The major goal of this study was therefore to analyse and understand the effects of interrill erosion, soil crusting and soil aggregate breakdown on in situ CO2 effluxes. Therefore a set of rainfall simulations were carried out on bare loess-burden soil with different antecedent soil moisture content. All treatments were compared with controls protected from rain drop impact using a fine-meshed geotextile. As expected, runoff and sediment delivery was significantly larger on bare compared to covered soils, while surface runoff and sediment delivery increased (in most cases) with rising antecedent soil moisture as well as rainfall duration. Crust thickness increased with antecedent soil moisture and rainfall intensity and was in general smaller for the controls. However, variations in crust thickness did not result in significant differences in in situ measured CO2 effluxes. Also the destruction of the soil crust after six to seven days of measurements did not have a significant effect. This leads to the conclusion that crusting and interrill erosion has no or only a minor effect on in situ CO2 effluxes. Nevertheless, it should be recognised that topsoil carbon is preferentially removed due to interrill erosion which may result in additional CO2 release at depositional sites or in stream and/or standing water bodies. [Copyright &y& Elsevier]

Abstract: The development of a physically based model to simulate the transport of soil solutes in runoff has provided a better understanding of the mechanisms of transport and has assisted in the development of effective methods to control nutrient loss from soils and the pollution of waterways. A refined model has been applied to experimental data in which the presumed exchange layer was replaced by a mixing zone. Assuming that the exchange rate is controlled by raindrop splash, the effects of diffusion can be neglected and the exchange rate, k m , can be replaced by the variable e r , the raindrop-induced water transfer rate, removing the need to calibrate k m . To calibrate our model, laboratory experiments were conducted on disturbed loessial soil with three initial soil-moisture contents (5%, 15%, and 20%, measured gravimetrically) under three rainfall intensities (60, 96, and 129mmh−1) and three slope gradients (5, 15, and 25°). The model''s simulated data agreed well with the experimental data, demonstrating that the refined model captured the temporal behaviour of solute transport in the runoff. This study provides a new approach to the modelling of chemical transport by investigating the effects of raindrops on sediments from soil in surface runoff. [Copyright &y& Elsevier]

Abstract: Although rock check dams have been used for centuries to control erosion and support subsistence agriculture on western US rangelands, there is a lack of measured data to quantify their impact on soil moisture distribution. This study was conducted to measure and document soil moisture response to loose rock structures and wire bound rock structures in comparison with untreated control sites during the first rainfall season following construction. A field experiment was conducted on a degraded alluvial fan in southeastern Arizona where erosion control structures were built on three small ephemeral channels. Soil moisture was measured three times per week at depths ranging from 15 to 46cm at six points on the upstream side of 5 loose rock structures, 5 wire bound structures, and at 5 untreated control sites throughout the 2006 summer monsoon season. Rainfall and runoff during 2006 were above average, and soil moisture was significantly higher through the channel bank soil profiles in proximity to loose rock and wire bound check dams than soil moisture measured at control sites. Erosion control structures are expected to increase local soil moisture in response to water impoundment. These results quantify this response and will be useful in designing rangeland restoration strategies that rely on soil moisture to improve vegetative cover. [Copyright &y& Elsevier]

Abstract: Globally, soils contain an estimated 1500GT of carbon, over twice that present in the atmosphere (IPCC, 2001). However the role of soils in the global carbon cycle remains highly contentious. Soil erosion redistributes organic matter (OM) within landscapes, and takes place at a range of scales from mass movement to interrill erosion. It is known that interrill erosion occurring on clay-rich stable soils causes sediment to become enriched in OM by up to a factor of 6.2 (Mora et al., 2007). However, maintenance of mass dictates that such enrichment can only be temporary unless erosion ceases due to armouring. The lack of studies showing a decline in OM erosion is attributed to the well-aggregated, slow-crusting soils used in such research. Thus, this investigation aimed to investigate the erosion of OM from rapid-crusting, sandy soils. Soils from both organically and conventionally farmed land from Shropshire, UK, were exposed to simulated rainfalls differing in both intensity and kinetic energy. The texture and OM content of soil crusts and eroded sediment were analysed. OM was enriched by more than 10% in one test only, but reduced significantly during two soil and rainfall combinations. Analysis of crust and sediment texture showed that the interaction between crust development and rainfall erosivity was responsible for the varying OM enrichment. The results also confirmed that, for practical erosion applications, the maintenance of the mass of OM has to be considered. Accordingly, a key requirement for the correct assessment of OM erosion is the proper assessment of the interaction between surface and rainfall over time in each erosion system. [Copyright &y& Elsevier]

Abstract: Gully erosion and woody plant encroachment are frequently observed in grasslands worldwide. Gully erosion driven by water processes is usually affected by topography, land-use change and vegetation cover. We hypothesised that trees, through their potential link with overland and subsurface flow, may have an impact on gully extension. However, very few studies have simultaneously considered tree encroachment and gullies. We used aerial photographs to study Acacia sieberiana encroachment and gully erosion in a South African grassland (KwaZulu-Natal Province) for a period lasting 64years. At the catchment scale, results showed that acacias started invading after 1976 and transformed the grassland into a savanna with 9.45% of tree cover in 2009. Gully area increased by 3.9% in the last 64years and represented 12.76% of catchment area in 2009. Mean estimated sediment loss was 200Mgha−1 of gully y−1, indicating a high erosion rate mainly due to the collapse of gully banks after swelling and shrinking. Volumetric retreat rate (V) of 15 gully heads was correlated with drainage area (Drain.A) by a power function explaining 64% of the variance: V =0.02*Drain.A 0.83. A positive correlation between gully retreat rate and Acacia canopy area was measured between 2001 and 2009 when established tree encroachment was observed. These results, associated with the susceptibility of this soil to subsurface flow and the observation of pipe erosion systems in the field, showed that both surface and subsurface processes occur in this sub-humid grassland and that trees can be indirectly associated with increased gully erosion. [Copyright &y& Elsevier]

Abstract: Andisols are soils with high structural development and aggregate stability, characteristics that play a major role in their high infiltration rate. They are, however, vulnerable to environmental changes, particularly those associated with land use modifications. The present work aims to ascertain the influence of modifications to land use as well as vegetation cover on the steady-state infiltration rate and associated properties of Andisols on the volcanic island of Tenerife (Canary Islands, Spain). Thirty two sites were selected in three categories of land use/vegetation cover (green forest, pine forest and cropped areas). The infiltration rate was studied using a double ring infiltrometer. Other soil properties which influence infiltration – organic matter content, texture, structure, bulk density, water retention capacity and water repellency – were also studied. Infiltration is extremely rapid under green forest (796 mmh−1) but falls considerably under pine forest (188mmh−1) and in formerly cropped soils (67mmh−1). The statistical analysis shows that the main soil properties affected by a change in land use/vegetation and which determine infiltration are soil aggregation, structural stability and, to a lesser extent, organic matter and bulk density. Compared to the green forest sites, a notable reduction in soil aggregation, structural stability and organic matter, and an increase in bulk density, are observed in the formerly cropped soils. Although less pronounced, the same tendency is seen also in the pine forest sites when compared to their green forest counterparts. The results confirm the vulnerability of Andisols'' soil properties and infiltration to land use modification, while also highlighting the influence of the type of forest cover present. [Copyright &y& Elsevier]

Abstract: A rainfall simulator is an ideal tool for infiltration, soil erosion, and other related research areas for replicating the process and characteristics of natural rainfall. In this study, a laboratory-scale rainfall simulator is developed. Rainfall characteristics including the rainfall intensity and its spatial uniformity, raindrop size, raindrop velocity, and kinetic energy confirm that natural rainfall conditions are simulated with sufficient accuracy. Pressure nozzles are used to spray water corresponding to rainfall intensities ranging from 45 to 105mmh−1. The simulator produces rainfall with uniformity coefficient changing between 82 and 89%. The raindrops falling with an initial velocity from a height of 2.43m have median diameters of 2.2–3.1mm. The impact velocities of the median size raindrops deviate from their terminal velocities with a relative error between 6 and 15%. The accompanying erosion flume can be given slope up to 20% in lateral and longitudinal directions. During the experiments, flow measurement is taken from two outlets at the end of the flume to distinguish the contribution of interrill areas into rills. Experiments result in typical rainfall-induced hydrographs and sedigraphs observed under natural conditions. This shows the ability of the rainfall simulator for use in sediment transport processes over hillslopes. [Copyright &y& Elsevier]

Abstract: In terrestrial ecosystems, soil respiration is a key pathway of carbon to the atmosphere. It is highly variable in time and space. Its temporal variability at a single point can be reasonably described by changes in soil temperature and moisture. However, it is much more difficult to determine the drivers of its spatial variability. The aim of this study was to elucidate the interrelationship between the spatial variability of soil respiration and the spatial variability of soil redistribution as well as other soil and crop properties. The study was carried out in a small agricultural watershed (4.2ha) subjected to water and tillage erosion processes. During three crop cycles (one of sugar beet, two of winter wheat) soil respiration, soil temperature, and soil moisture were measured in situ at least bi-weekly at 20–22 locations. The first stage was to analyse the interrelation of soil temperature as an important control of soil respiration and soil redistribution. In the second stage, measured CO2 effluxes were standardised to 15°C and mean fluxes at each location were calculated for the sugar beet year, as well as two growing phases under winter wheat. The mean CO2 effluxes for the five resulting phases at each measuring location were correlated to soil and crop properties and modelled soil redistribution. Moreover, the intercorrelation of all explanatory variables was analysed using principal component analyses, and these principal components were correlated to standardised CO2 effluxes. Except for the second phase in 2009 with combined autotrophic and heterotrophic respiration, which was dominated by root respiration, in all phases there was a tendency that CO2 effluxes at erosional sites were smaller than at depositional sites. The combined analysis of CO2 effluxes, erosion, and other explanatory variables indicates that for heterotrophic respiration (between rows in the case of sugar beet and before significant plant growth in the case of winter wheat) the spatial variability of median grain size and bulk density had the most consistent effect on the spatial variability of soil respiration. In contrast, soil moisture was less important and topsoil SOC had more or less no effect on CO2 effluxes. Only in two measuring phases (Phase 2 2008 and Phase 1 2009) did the combined analysis show that total erosion was one of the dominant variables for the spatial variability in CO2 effluxes. In general, the relatively inconsistent effect of soil erosion status on spatial variability of CO2 effluxes is somewhat surprising, as there are a number of different reasons which support the assumption that CO2 effluxes at erosional sites should be smaller than at depositional sites. A major reason for the observed behaviour might be the compensating effect of tillage and water erosion and the counteracting effects of both processes on soil respiration. This underlines the importance of field-scale studies to gain further insight into the interrelation of soil redistribution and CO2 effluxes. [Copyright &y& Elsevier]