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The Universal Soil Loss Equation (USLE) and the Revised Universal Soil Loss Equation (RUSLE) have been widely used for predicting average soil loss. Slope length is an important topographical parameter of the L factor in USLE/RUSLE. Among the widely studied GIS procedures for extracting slope length, the distributed watershed erosion slope length (DWESL) based on the unit contributing area estimation method, which considers two-dimensional runoff process and cutoff factors, is a relatively complete model for calculating slope length. Slope length in the DWESL model is primarily calculated using conventional flow direction algorithms such as D8, Dinf, MS and MFD-md. However, DWESL outputs require further improvement due to the errors in the usual estimates of the uphill contributing area and the effective contour length of discrete elements. Combined with a theoretical differential equation of specific catchment area on hillsides, the calculation of the DWESL model was optimized without estimating the uphill contributing area or the effective contour length for each cell. The proposed integration method based on the topographical features slope line, contour curvature and cutoff factors (ITF method) was used to extract slope length from the raster digital elevation. Slope length extracted using the ITF method had the smallest error in verification of mathematical surfaces (average RRMSE = 0.0573), and its spatial distribution was more consistent with the structure of the terrain surface for all test data, relative to the conventional flow direction algorithms in the original DWESL model. The proposed ITF method could provide a reference for predicting soil erosion using the USLE/RUSLE model.

Aboveground plant parts can trap moving sediment on slopes during concentrated water runoff, resulting in the formation of sediment mounds around plants. Plant morphological and functional traits may influence these sediment trapping patterns. Characterizing the sediment trapping abilities of common plants is of great interest when selecting appropriate plant species for erosion control. Predicting plant sediment trapping abilities using fractal dimensions of sediment particle size distribution could enhance the management and restoration of degraded lands with declining vegetation coverage in dry-hot valleys. Using flume experiments, we studied sediment retention abilities in six common plant species: the tree species Leucaena leucocephala and Melia azedarach; the shrub species Dodonaea viscose and Coriaria sinica; and the graminoids Heteropogon contortus and Eulaliopsis binate. Sediment trapping mass was measured at two ages (three-month-old and one-year-old seedlings). The particle size distribution of trapped sediment was determined using a laser particle size analyzer. The fractal characterizations (singular- and multi-fractal dimensions) of sediment particle size distribution were calculated using the fractal scale theory. Statistical analyses were performed to compare sediment trapping mass and the fractal characterizations in the six species at the two ages. C. sinica had the highest relative trapped sediment at both ages. Trapped sediment mass of one-year-old seedlings were significantly related to the singular fractal dimension (D), capacity dimension (D0), entropy dimension (D1), and correlation dimension (D2) of trapped sediment particle size distribution. However, trapped sediment mass of three-month-old seedlings was only related to D, while that combining the data in both ages had significant correlations with D and D0. Our results suggest that fractal dimension of sediment particle size distribution can predict sediment mass trapped by plants. Such knowledge may help maximize sediment trapping through appropriate species selection and provide useful information for slope erosion control.

Suspended sediment concentration (SSC) time series are highly nonlinear and nonstationary due to numerous influencing factors that can be characterized by specific time scales, thereby increasing the difficulty of performing SSC simulations. Analyzing the spectral and temporal information of the SSC and its contributing factors can improve the resulting simulation efforts. In this study, the Hilbert-Huang transform (HHT) was used to identify the time scales and change trends of the daily SSC, rainfall, runoff and normalized difference vegetation index (NDVI) of the Kuye River in the Loess Plateau of China. Artificial neural network (ANN), multiple linear regression (MLR), hybrid ensemble empirical mode decomposition (EEMD)-ANN and EEMD-MLR models were chosen to simulate the SSC time series. The periods of the rainfall intrinsic mode functions (IMFs, except IMF9 and 10) were generally consistent with those of the IMFs corresponding to the SSC and runoff. In comparison, the periods of the IMFs corresponding to the NDVI were longer. The minimal period was 3 days for the SSC, rainfall and runoff and 10 days for the NDVI. The minimal period displays the greatest variance contribution and plays the most important role in the SSC, rainfall and runoff changes. The annual cycle has the largest contribution to the NDVI variability. Residual components indicated that the SSC of the Kuye River decreased from 2006 to 2010, while the regional rainfall, runoff and NDVI increased. The R2 values of the ANN and MLR models were 0.34 and 0.39, respectively. Compared with the MLR and ANN models, the R2 values of the EEMD-ANN and EEMD-MLR models increased by 52.9% and 41.0%, respectively, indicating that the ANN model was more robust than the MLR model when simulating nonlinear SSC time series. Compared with EMD, EEMD can alleviate the mode mixing problem and significantly increase the simulation accuracy with the ANN and MLR models. Significance tests were employed to determine the strength of the physical meaning in each IMF component. Taking IMFs with significant (p

This study investigates the relations between climate change and both runoff and sediment yield in watersheds and provides a scientific basis for water resources planning and design as well as watershed-scale soil and water conservation. The impact of climate change on runoff and sediment yield in a watershed does not occur in isolation, but is a synergistic process in which climate and vegetation jointly influence runoff and sediment yield. Previous studies have seldom addressed this synergistic effect. For this study, a regression model between climate factors (temperature and precipitation) and the Normalized Difference Vegetation Index (NDVI) was established using data from the Zhenjiangguan Watershed in China. By combining data on climate-driven changes in vegetation cover, the Soil and Water Assessment Tool (SWAT) model was built to simulate runoff and sediment yield in the watershed under two scenarios: changes in climate, and synergistic changes in climate and vegetation cover. The simulation results show that precipitation is the most sensitive factor affecting runoff and sediment yield; 10% change in annual precipitation can cause 10%–14% change in annual runoff and 17%–24% change in annual sediment yield. Temperature is also an important factor affecting runoff and sediment yield in the watershed. Each temperature increase of 0.7 °C can result in a decrease of 1.4%–2% in annual runoff and 2%–3.7% in annual sediment yield. This research reveals that accounting for synergetic change in vegetation has an impact on runoff and sediment yield results, and that the magnitude and nature of this influence vary among different combinations of temperature and precipitation changes. When temperature was kept constant, the effect of vegetation cover change caused by precipitation change on runoff and sediment yield was relatively small (only 0.9%–1.5% of the total change), and vegetation cover change inhibited the effects of precipitation change on runoff and sediment yield. When precipitation was kept constant, the effects of vegetation cover change caused by temperature change on runoff and sediment yield were relatively large (20%–30% of the total change), and vegetation cover change enhanced the effects of temperature change on runoff and sediment yield. This investigation considers the synergistic effects of climate and vegetation cover change, and thus further clarifies the extent to which climate change impacts water and ecological resources.

In order to study the characteristics of soil total carbon (TC) transport with slope runoff and interflow during rainstorms in the Zhejiang-Fujian hilly region, China. Slope gradients (5, 8, 15, 25°) and rainfall intensities (60, 90, 150 mm·h−1) were selected as the variable factors for artificially simulated rainfall experiments. Runoff samples were collected every 3 min to measure the volume and TC mass concentration, then we calculated the TC loss rates and loss gross amount. The results showed that the overall trend of TC mass concentration in slope runoff presented a high initial value that gradually decreased with the increase of rainfall duration and finally tended to be stable, and it mean mass concentration was relatively highest at all the 15° conditions. The TC loss rates presented a stability at a certain value after gradually increasing over time at gentle slopes while it led to an increasing trend when the slope was steeper, yet these trends weren't obvious at 150 mm·h−1 condition. The initial TC mass concentration was low at beginning in interflow which rose rapidly to the peak and finally continued to drop to a stable level. The shape of TC loss rate curves was similar to mass concentration curves. For both slope runoff and interflow, the slope gradient had little effect on TC mass concentration. The TC loss gross amount in the runoff (slope runoff + interflow) increased with the increase of slope gradients or rainfall intensities, which reached the maximum value at the 25°, 150 mm·h−1 condition, namely, 12.56 g, though the increase rates of TC transport decreased. The TC loss gross amount with slope runoff showed a trend of increasing first and then decreasing with increasing slope gradients, which all reached the maximum at 8° conditions, however it showed a continued rising trend as slope gradients increased in interflow. TC at 15° and 25° conditions mainly lost with the interflow, though at other slope gradients it mainly transported with the slope runoff. Similarly, the more gentle the slope gradients, the greater the proportion of the slope runoff volume in total runoff. The regression analysis showed at identical conditions, the influence of rainfall intensity on TC loss was larger than slope gradient in slope runoff while the slope gradient had a greater influence on TC loss in interflow. Correlation analysis showed that there was a significant correlation between the runoff volume and the TC loss gross amount in slope runoff and interflow (P

The soil hydrological process plays an important role in transporting and distributing water in soils. However, the correlation between water flow behaviors, soil physical properties, infiltration patterns of soil exhibiting different soil layers, and the variation patterns in water flow behavior in rubber-based agroforestry systems remain poorly understood. Here, we mainly used dye-tracer infiltration to classify water flow behavior and HYDRUS-3D to interpret variation patterns of water flow behaviors in a rubber-based agroforestry system in southwest China. The results showed that (1) the soil of forestry patches under Hevea brasiliensis (HB) and Citrus reticulata (CR) exhibited better soil physical properties than those with no vegetation (NV). Compared with these in the NV, the saturated soil water content and field capacity increased by 15% and 21% in CR, and by 2% and 12% in HB, respectively; while the saturated hydraulic conductivity enhanced by 584% (p HB > NV. Finally, (3) the infiltration flow in soil under HB and CR exhibited a faster downward wetting front and an obvious lateral flow. These infiltration patterns compensated for the insufficiency of soil water in NV and finally caused water redistribution to be more homogenized across the whole soil profile. Therefore, our findings indicated that the rubber-based agroforestry system is a successful approach for conserving water and reducing runoff in tropical regions.

The future trend of water and sediment variation is closely related to the governance of the Yellow River. The increasingly frequent occurrence of extreme rainfall events has rendered the future water and sediment situation of the Yellow River uncertain. Understanding the characteristics of flood and sediment yield of the river basin under extreme rainfall conditions at different times is a prerequisite and foundation for accurate prediction of water and sediment situation in the Yellow River in the future period. We here used the July 26 extraordinary rainstorm event in 2017 in the Wuding River as a starting point for revealing the law of flood and sediment yields changes under extreme rainfall conditions around the year 2000. The results indicated that, during the period from 1960 to 2016, the average proportion of extreme rainfall depth in the middle Yellow River region over the total precipitation depth increased by 5.1%. Areas where extreme rainfall events frequently occur showed a trend of developing from localized regions in the Toudaoguai–Longmen reach to the majority of the middle reaches. There were obvious changes in the rainfall-flood and rainfall-sediment relations under extreme rainfall conditions. Compared with historical extreme rainfall events, the decline in flood and sediment yield in the river basin after 2000 under similar rainfall and intensity conditions was obvious. Among these results, flood decreased by 30.4–78.2%, sediment yield was decreased by 53.0–88.2% and sediment content in flood was decreased by >47.2% on average when compared with the same rainfall conditions in the previous century. Comparative watershed studies showed that, during extreme rainfall events, areas under soil and water loss management programs suffer 57.2% and 75.7% less flood runoff modulus and sediment transport modulus, respectively, than non-managed areas. This indicates that soil and water loss management is the major driving factor for changes in rainfall-flood and rainfall-sediment relations under extreme rainfall conditions. This study highlights the importance of soil and water loss management in the flood control and sediment reduction. We concluded that, with the implementation of soil and water conservation measures, the probability of large flood and sediment events will greatly decrease and the amount of sediment entering the Yellow River under extreme rainfall will further decrease in the next 30 years.

Furrow diking is a type of conservation tillage practice that is widely used throughout the world and has been proved to be effective for preventing runoff and soil loss. However, it is not easy to maintain a stable conservation effect of furrow diking in various environments. Few studies have focused on the effects of rainfall and slope on the integrity and conservation efficiency of furrow diking. Therefore, simulated rainfall experiments were conducted with four rainfall intensities (30 mm/h, 60 mm/h, 90 mm/h and 120 mm/h) and three slopes (2, 4 and 8°) to study the effects of rainfall intensity and slope on soil and runoff production of furrow diking as well as its conservation efficiency. The conservation efficiencies were obtained by comparing furrow diking with up-down slope ridges. The result indicated that as rainfall intensity and slope increased, furrow diking dams may suffer from runoff overtopping resulting in damage and ultimate collapse. During this process, runoff and soil loss increased rapidly, severe rill erosion developed on dams resulting in the loss of the ability of furrow diking to store rainwater and sediment and obvious declines of water and soil conservation efficiencies. This paper established empirical equations to estimate the conservation efficiency of furrow diking under undamaged and damaged conditions. An empirical equation was also presented to estimate the critical rainfall and slope conditions that may cause overtopping, damage or collapse of dams in order to guide the implementation of furrow diking and predict its conservation efficiency.

Gully headcut retreat (GHR) is an important processes in gully development, and previous studies have tried to predict GHR rates based on flow hydraulic parameters during runoff scouring, but other dynamics such as gravity also affect GHR processes in addition to flow hydraulics. The aim of this study is to examine the influences of mass failures due to gravity on the erosion and hydraulics processes of gully headcuts during runoff scouring. A flow scouring experiment including 11 tests with two discharges (i.e., 7 tests with 83.3 l min−1 and 4 tests with 166.7 l min−1) was conducted on 5 in situ gully head plots with similar initial topographies. Totally 36 mass failure events were observed of all the 5 gully heads during the experiment, and 63.9% of the events were occurred during the first 10 min of the tests after drying-rewetting cycles. The tests were classified into two series according to whether the mass failure occurred during the scouring. The tests with mass failures (Series I) contributed 81.7% of the total soil loss of GHR, and the average GHR rates by mass (GHRm) was about 5 times higher than that of the tests without mass failures (Series II). The mass failure clearly influenced the flow resistances on gully beds by increasing the surfaces roughness and the sediment load to gully beds, and the average Darcy–Weisbach friction factor (f) and Manning coefficient (n) of Series I were clearly higher than those of Series II. Compared to the previous studies without significant soil collapse from gully heads, the logarithmic growth relationship between GHRm and the energy consumption (ΔEt) was quite weak in this study, but the R2 between GHRm and ΔEt increased for longer time scales. The results indicated that for individual runoff events, GHR rates could not be predicted by flow hydraulics alone because mass failures due to gravity made great contribution, but on longer time scales, the influence of soil collapse is reduced, and flow hydraulics become the key factor impacting GHR processes.

Climate change and human activities are considered to be the main drivers of runoff changes. Assessing their contributions is important for maintaining the integrity of the water cycle process and promoting the healthy management of water resources. But the contributions of these two factors in the Beichuan River Basin remain unclear. In this study, hydrological and meteorological data from six sub-basins (Niuchang, Xiamen, Heilin, Qiaotou, Dongxia, and Chaoyang) during 1961–2013 were studied to elucidate upon the effects of these processes. Mann-Kendall tests showed that runoff in the Beichuan River Basin showed a downward trend over the study period and revealed that abrupt changes occurred in 1972 and 1989. Therefore, the study period was divided into two periods: a base period and a change period (periods I and II). A climate elasticity model and hydrological sensitivity analysis were used to estimate the contributions of climate change and human activities. We found that the dominant factors in changing runoff were human activities. Due with the conversion of cropland to forest and grassland and increases of construction land, during the change period water supply increases evidently. Among the basin regions, the Chaoyang sub-basin showed the greatest runoff decline and an abrupt change in 1989, and human activities had the greatest contribution to runoff change in this sub-basin. In addition, the conversion of cropland to forest and grassland was most evident in the Chaoyang and Qiaotou sub-basins, and the area of construction land in these two regions increased greatly during the change period.

Dissolved carbon plays a pivotal role in carbon cycles and potentially affects ecological processes of water body. While stalk mulch can regulate soil and water losses, its effects on the export of dissolved carbon from soils are poorly understood. The main objective of this study was to determine the effects of rainfall intensity and downslope cornstalk mulch (the lengths of cornstalks along the slope, DCM) on runoff, sediment yield and dissolved carbon losses, including dissolved inorganic carbon (DIC), dissolved organic carbon (DOC) and dissolved total carbon (DTC). A series of field rainfall simulations were conducted on the steep fallow land (20 °) locating in a representative hillslope of southwestern China that experiences severe soil erosion, and data for runoff, sediment and dissolved carbon loss rates were obtained from triplet parallel plots (1.5 m long and 1 m wide for each one) using 60 min rainfall simulations at 30 and 90 mm h−1 intensities on bare soils and 90 mm h−1 intensity on soils with DCM (air-dried whole plants, 60% coverage and weight 1.65 kg), respectively. Rainfall intensity showed positive effects on runoff generation, sediment yield and loss rates of DIC, DOC and DTC. The plots with immediate DCM had no difference in runoff generation, but were 71.1% lower in sediment yield and 53.9% higher in DOC loss rate relative to the bare plots. The contribution of DIC to DTC increased from 35.9% to 59.6% with the increasing rainfall intensity. Cornstalk mulching appeared efficient in reducing sediment yield, but its adoption is likely to dramatically enhance DOC exports from soils with concerns for the quality of inland waters. Further research studies are required to discriminate between soil and cornstalk mulch contribution to DOC exports by overland flow.

The benefits of conservation tillage on water erosion control have been extensively tested in China, while few studies have involved their regional differences. We synthesized 81 recent publications about the water erosion control by conservation tillage in China, to explore the regional difference of conservation tillage and identify the optimal tillage methods of each region. The benefits of conservation tillage for runoff retention and sediment reduction are different in different regions due to the special environmental condition of each region. Conservation tillage demonstrated the lowest efficiency in the Northwest China Loess Plateau region and highest in the North China mountainous region, while no significant differences were found among other 4 regions. In the Northeast China black soil region, micro-basins tillage (MBT) is the optimal tillage method due to its greatest benefits in reducing runoff and sediment. In the North China mountainous region, the values of regional efficiency evaluation index (REEI) of runoff and sediment were both larger than 1 only by contour tillage with hedgerow (CTH), thus CTH will be the optimal tillage method in this region. In the Northwest China Loess Plateau region, some engineering measures should be the priority due to the limited benefits of conservation tillage. In the South China red soil region, no tillage with mulch (NTM) presented the greatest benefits on water erosion control and largest values of runoff and sediment REEI, thus CTH is the priority in this region. In the Southwest China purple soil region, though the values of runoff and sediment REEI by collecting soil to form ridges with no tillage (CSNT) are less than those by MBT, CSNT is the most suitable tillage method in this region. The small sample size leads to the unreliable results in the Southwest China karst region, thus more researches are needed in this region.

Phosphorus (P) is usually enriched in urban soils but the environmental consequences of this P enrichment are not well understood. The objective of this study was to investigate P sorption characteristics as a measure of potential P loss from urban soils due to P enrichment via runoff and leaching. We collected soil samples at 0–5 and 5–15 cm soil depths from urban park areas in Nanchang, China, a rapidly expanding city with low P contents in its natural soils. Soil P sorption indices were characterized by a multiple-point isotherm batch experiment. The 0–5 cm layer had lower Langmuir P sorption maximum (Smax) than the 5–15 cm layer, probably because of its lower amorphous Al oxide (Alox) content and higher soil organic carbon (SOC) content. Stepwise multiple regression showed that the combination of Alox and SOC were the two most important soil properties related to Smax of the studied soils. A two-piece segmented linear regression was fitted to the relationships between labile P fractions (i.e., water extractable-P and anion exchange resin-extractable P) and binding energies (k) and the change point values were identified for k below which labile P decreased linearly. Soils below the change point had greater contents of SOC and exchangeable Ca and Mg and higher pH than those above the change point. These results suggest that parent materials played a major role in regulating P sorption capacities of the urban soils, particularly for the soils in urban green spaces. However, the enrichment of Ca and Mg derived from dissolution of calcareous materials in urban areas could significantly influence P bonding strength and saturation ratio of urban soils.

Overburdened stockpiles during construction projects are typically loose mixtures with different proportions of fines and gravel. They are common sources of anthropogenic accelerated erosion that threatens environmental quality and the quality of life for people in many parts of the world. Overburdened stockpiles have unique three-dimensional shapes. However, studies with these materials are usually performed in traditional planar soil bins. Therefore, in this study, a specially designed mobile experimental device was used to accurately evaluate the runoff erosion process on overburdened stockpiles in a three-dimensional conical shape. A series of indoor rainfall simulation experiments at 60 mm/h rainfall intensity was conducted using material with different gravel contents (0%, 10%, 20%, 30%, and 40%). The results showed that the runoff rate and flow velocity exhibited the same trend, i.e., a rapid increase, followed by a slow increase and then stabilization. The runoff regime in all experiments manifested as laminar and subcritical flow during the runoff process. Re and Fr values were much smaller than those on two-dimensional plane simulation of overburdened stockpiles. The presence of gravel caused the runoff to be slow and stable. Runoff rate, flow velocity, Re and Fr values all decreased with increasing gravel content. The sediment yield decreased logarithmically in response to the increasing gravel content. The study findings are not only helpful for understanding the hydraulic characteristics and erosion features that characterize overburdened stockpiles, but also have implications for prediction models of soil and water loss from this material during production and use in construction projects.

The interactions between precipitation, runoff and sedimentation could reveal information about the processes of runoff and sediment production and the environmental evolution mechanisms of basins. Based on the hydrometeorological data collected over a long-term time series (1955–2012) which has been divided into five periods (P1 (1956–1969), P2 (1970–1979), P3 (1980–1989), P4 (1990–1999) and P5 (2000−2012)), changes and implications of the relationships between precipitation, runoff and sediment load (precipitation-runoff-sediment relationships) were studied in the Wuding River basin, China. Conclusions are as follows. (1) There is no obvious change occurs on the distribution of annual precipitation during 1955 to 2012. However, the annual runoff and sediment load are significantly decreased by 51.9% and 86.4%, respectively, from P1 to P5. (2) Under the same precipitation conditions, the runoff and sediment present overall decreasing trends. Decrease in the runoff was greater than that in the sediment load. The incoming sediment coefficient (ISC) reduced by 69.2%, indicating that the sediment transport ability per unit runoff was weakened. The significant reduction of ISC along with the decrease of the runoff amount caused the sediment brought into the Yellow River (STWY) decreased from P1 to P5. (3) Soil conservation measures played a critical role for the changes in precipitation-runoff-sediment relationships. Due to the rapid increases in the available storage of check dams in P2 and P5 and the areas of forest and grassland in P2, relationships among the precipitation, runoff and sediment has drastically changed. Decrease of the effects on sediment interception in check dams caused the sediment increased from P3 to P4. (4) Decreases of runoff and sediment load, and changes in their relationships would continue with the sustainable management of slopes and gullies. The potentially detrimental changes in the storage of check dams and those in runoff and sediment influenced by extreme weather conditions should be monitored and managed.

Serious soil erosion and an extremely low rate of soil formation leads to a thin layer of surface soil that makes tree growth difficult in areas of karst. Meanwhile, surface soil, driven by runoff, enters shallow karst fissures (SKFs); these SKFs filled with soil have become the major habitat type in the area. Here, we explore the morphological characteristics of shallow karst fissures as well as the soil physical and chemical properties of the SKFs and comprehensively analyse the factors that influence the soil properties. Three key results are presented. First, a high heterogeneity of morphological characteristics exists for shallow karst fissures. According to the different characteristics of the vertical section, the SKFs can be divided into 5 types. These types are Rectangle-type, Pyramid-type, Funnel-type, Net-type and Diamond-type. In addition, the SKF dip angles were mainly between 60° and 90° (76.39%), the width of the top aperture was mainly between 20 and 40 cm (51.39%), and the trace lengths were mainly between 80 and 160 cm (76.39%). Second, compared with their characteristics of surface soil, the bulk density and fractal dimension of soil particles of the SKFs were both large, and the main composition of the SKF soil was clay. Third, the soil nutrients of the SKFs (the organic matter, total nitrogen and total phosphorus) were lower than the surface soil nutrients but not significantly so. The total potassium (TK) of the SKFs was greater than that observed for the surface and increased as the depth of the SKF increased. The soil nutrients of the SKFs were significantly affected by the fissure morphology. The poorly connected fissures had better soil fertility. When the morphological characteristics and soil properties of the SKFs were comprehensively considered, the vegetation types that were determined to be the best for use in the ecological restoration of areas of karst rocky desertification were deep-rooted plants with especially strong root penetration. The result of this study can supply some reference for future studies of karst rocky desertification control and vegetation restoration in the karst area of Southwest China; in the South Claw Silicon Island in Yogyakarta Province, Indonesia; and in other karst regions with the same ecological background.

Karst rocky desertification, a kind of intense soil degradation, has become an urgent environmental issue in the karst region of southwest China. It was found that limestone soil, a typical soil of the karst region, is more vulnerable to karst rocky desertification than adjacent other soils although limestone soil has relatively high TOC (total organic carbon) content, but underlying mechanisms remain unclear. To investigate roles of soil properties in karst rocky desertification, three major soils, limestone soil, yellow soil and yellow brown soil, of the karst region of southwest China were sampled and their total extractable humic acid (THA) were fractionated into three sub-fractions, namely, free HA (HAf), encapsulated HA (HAe) and interacted HA (HAi), with a sequential extraction method. These soils and fractionated HA samples were systematically characterized with various analysis methods and discussed. The results showed that limestone soil had higher contents of total organic content (TOC) and THA content, but its THAC/TOC (carbon in THA to TOC) ratio (23.39%) was lower than those of yellow soil (31.44%) and yellow-brown soil (30.74%); C/N ratios and total acid contents of HAe and HAi fractions, which were physically protected by soil minerals/aggregates, were much higher than those of HAf fractions, indicating that HAe and HAi could be more active and degraded easier than HAf once exposed to microbes or/and runoff erosions. Therefore, lower HAf content and significantly lower HAfC/TOC (carbon in HAf to TOC) ratio of limestone soil may underlie the observation that limestone soil showed weak resistance to karst rocky desertification compared to other adjacent soils when the site had been artificial disturbed. We believe that roles of different HA fractions to overall quality and stability of soil deserve more attention.

San Juan Coal Company reclaimed 743 ha at its La Plata Mine using the GeoFluv™ fluvial geomorphic reclamation design method from 1999 through 2008 to achieve long-term stability against erosion (no major slope blowouts and rill and gully formation), reduced maintenance, and increased biodiversity as compared to traditional reclamation methods (e.g. terrace, berm, and downdrain designs). Qualitative inspections of the completed reclamation confirmed the fluvial geomorphic reclamation method benefits. In the fall of 2011, the company began implementing a research study to quantify the sediment production rate from these geomorphic landforms and surrounding undisturbed native lands. Data were acquired from subwatersheds differentiated as native (undisturbed by mining), fluvial geomorphic design with topdressing and poorly established vegetation, and fluvial geomorphic design with topdressing and significant vegetation establishment. The three subwatersheds were selected to ensure similar size, aspect, and slope and were located close together to minimize storm variation effects. Temporary check-dam-type sediment control structures designed to impound runoff from a 2-yr, 1-h storm were installed at each subwatershed outlet. Erosion pins in the impounded area facilitated sediment deposition measurement. Precipitation was recorded by the La Plata Mine Meteorological Station and supplemental site-specific precipitation gauges. Precipitation sufficient to cause sediment transport provided data for the end of the 2012, all of the 2013, and the beginning of the 2014 water years. The site data provided direct relationships between sediment production and precipitation. The sediment yield from the undisturbed native site was 9.53 t ha−1 yr−1, while the fluvial geomorphic design with topdressing and poorly established vegetation site averaged 13% lower than the native site, and the fluvial geomorphic design with topdressing and significant vegetation establishment averaging 41% lower sediment yield than the native site. Land-disturbing activities that can accelerate erosion and sediment yield will accompany global population growth. The results of this study indicate that use of this land reclamation method can mitigate erosion and sediment yield increases associated with that growth.

Sediment yield is one of the primary variables of the global denudation system and is often adopted as a measure of terrestrial erosion rates in watersheds. In general watersheds, sediment supply and transport are two of the major mechanisms that may alternate sediment yield. The ordinary approach to conduct sediment prediction is to assume that erosion rates and average annual sediment yields are affected by mean annual precipitation. However, this assumption cannot fully reflect the behavior of sediment yield in regions with relatively high temporal variability. In this study, the TsengWen River Watershed (TWRW) was investigated to characterize the landslide distribution and the associated sediment yield. The results show that lithology can influence the frequency-area distribution of landslides and hence can control the volumetric sediment on hillslopes that contributes to fluvial systems. Short-term sediment yield in downstream reaches of channels correlated with the rainfall erosivity and the water discharge during rainstorms. The amount of supplied sediment and storm runoff on hillslopes as well as the transport capacity of river channels could create limitations in watershed systems. The large amount of sediment transported by rivers is attributed to the additional supply of sediment materials from upland sources such as hillslopes. Subsequent storm events could change the relationships of the sediment supply with respect to water discharge. Hence, large rainfall events are crucial for controlling sediment production, storm runoff on hillslopes, and the transport capacity of river channels in medium watersheds. In addition, anthropogenic forces may also create corresponding impact on the relationships of sediment yield, supply, and transport processes.

[EN] In many Mediterranean areas, citrus orchards exhibit high soil loss rates because of the expansion of drip irrigation that allows cultivation on sloping terrain and the widespread use of glyphosate. To mitigate these non-sustainable soil losses, straw mulch could be applied as an efficient solution but this has been poorly studied. Therefore, the main goal of this paper was to assess the use of straw mulch as a tool to reduce soil losses in clementine plantations, which can be considered representative of a typical Mediterranean citrus orchard. A total of 40 rainfall simulation experiments were carried out on 20 pairs of neighbouring bare and mulched plots. Each experiment involved applying 38.8 mm of rain at a constant rate over 1 h to a circular plot of 0.28 m(2) circular plots. The results showed that a cover of 50% of straw (60 g m(-2)) was able to delay the time to ponding from 32 to 52 s and the time to runoff initiation from 57 to 129 s. Also, the mulching reduced the runoff coefficient from 65.6 to 50.5%. The effect on sediment transport was even more pronounced, as the straw mulch reduced the sediment concentration from 16.7 g l(-1) to 3.6 g l(-1) and the soil erosion rates from 439 g to 73 g. Our results indicated that mulching can be used as a useful management practice to control soil erosion rates due to the immediate effect on high soil detachment rate and runoff initiation reduction in conventional clementine orchards on sloping land, by slowing down runoff initiation and by reducing runoff generation and, especially, sediment losses. We indirectly concluded that straw mulch is also a sustainable solution in glyphosate-treated citrus plantations., This paper is part of the results of research projects GL2008-02879/BTE, LEDDRA 243857 and RECARE-FP7 (ENV.2013.6.2-4).

Various conservation practices have been used to control soil erosion in cropland which makes assessing the effects of soil conservation more important. Northeastern China is an important crop-producing regions, with severe soil erosion. In the study, 110 runoff plot-year observations from seven experimental stations distributed over the region were used to assess the effects of local conservation practices on soil erosion, using a simplified USLE. Under the assumption that there were no significant differences in rainfall erosivity and soil erodibility in the study area under the “no practice scenario”, we described a simplified linear model based slope steepness and soil loss rate. The Jixing watershed was selected as a case study to test the model. The results indicate that the derived model can be used in the NE region of China for conservation assessment. The P factor values, related to main soil conservation practices, were derived from the observed plot-year data. The average values of P factor were around 0.01 to 0.35, which were low enough to justify their conservation effects of implementation through the assessment. Comparing to the conventional slope ridging tillage, the conservation rates of terraces, strip ridging, orchards and agro-forestry in the Jixing Watershed were 0.57, 0.6, 1.07, and 0.62 mm/ha, respectively, obtained by the assessment method in the study case. The paper neglected the seasonal variation which should be grouped to the C factor for the annual data and discussed the limitations of the assessment model for application.

Tubers and root crops are a typical element of the crop rotation system widely practiced in the Swiss Plateau and especially prone to soil erosion by water, resulting in recurrent soil loss and considerable off-site damage. Improved cultivation practices are therefore needed to counteract and mitigate the erosion risk. This research evaluates the effectiveness of a device called the “Dyker”, which was trialled during two cropping seasons. The Dyker consists of a set of parallel wheels with three inclined shovels each. It is attached to the rear end of a potato planting machine and digs holes into the bottom of the furrows between the potato ridges. The holes are intended to improve water infiltration, and minimize surface runoff and soil erosion. A dye tracer experiment showed that in treated furrows, water infiltrates the compacted subsoil below the plough horizon, while in untreated furrows, hardly any water infiltrates deeper than 20 cm below the surface. Drone photographs showed that the Dyker effectively reduces the amount of stagnant water in depressions: while in treated furrows, rainwater was evenly retained in small holes and infiltrated the soil locally, in untreated furrows it drained to the lowest point of the plot. Due to saturation, excess water remained in the untreated furrows for several days and created anaerobic conditions in the adjacent potato ridges and ultimately led to crop failure. In addition, measurements of temporal and spatial changes of the cross-sectional geometry of furrows showed more erosion and deposition processes in untreated furrows. The positive changes in surface structure diminish in time, as the small holes between the micro-dams gradually fill up, depending on rainfall amounts and intensities.

Shrub patch fragmentation makes a substantial contribution to soil erosion in sandy regions. This study aimed to analyze the effects of mosaic-pattern shrub patch size on runoff and sedimentation in a wind-water erosion crisscross region. The influence of shrub patch size on runoff and sedimentation, and on several soil physical and vegetation factors was evaluated in a sandy Chinese landscape. Based upon the canopy diameter of Artemisia ordosica, a xerophytic shrub, three different patch sizes were set as the treatments, such as small (O 160 cm) shrub patches. Bare land served as control conditions. Three runoff plots were established for each shrub size, and runoff (Q) and sediment (SY) yields were monitored under natural rainfall conditions. The results indicated that rainfall distribution was uneven in the study area. Low-intensity (0–5 mm/h) and short-duration (0–5 h) rainfall events accounted for 82.6% and 71.7% of all events, respectively, during the 6-month test period, from May to October 2016. Linear regression indicated that Q and SY increased with increasing rainfall depth at the slope scale. The impact of rainfall erosion on bare land was the greatest. Compared with control plots, Q and SY reduction owing to the small, medium, and large shrub patches was 19.7% and 49.3%, 31.4% and 62.4%, and 35.9% and 94.9%, respectively. These results confirmed the different effects of shrub patches of different sizes on soil quality, runoff and sediment reduction. Besides, this study suggested that shrub patches could modify soil microhabitats on sandy soils, reducing the soil erosion rates and as well as favoring vegetation regeneration.

While studies over retreat (reduction in glacier mass and snow cover area) of the Gangotri Glacier have received worldwide attention; no research has so far been conducted to quantify the contributions of snowmelt and glacier melt to the total flow of the Bhagirathi (upper Ganga) River emanating from the Gangotri Glacier. In the present study, the fractional contributions of snowmelt, glacier melt and direct runoff to the Bhagirathi River were estimated on ten daily and monthly time intervals for the ablation period (May to September) of 2005 using environmental isotope (δ2H, δ18O and 3H) techniques. Hydrograph separation was carried out using a two-component and three-component isotope mixing models. The estimated average seasonal (ablation period) contributions of snowmelt, glacier melt and direct runoff to the Bhagirathi River were 59.6%, 36.8% and 3.6%, respectively. Also, the significant temporal variations in their contributions were observed. The monthly proportions of snowmelt in the river flow varied from 42.9% (July) to 91.9% (May), while the monthly ratios of glacier melt ranged between 8.1% (May) and 47.4% (July). The observed temporal variability in the estimated contributions of the snowmelt could be linked to the Snow Cover Area (SCA) of the catchment. The results of the hydrograph separation indicate that the snowmelt dominates the river flow during the ablation period. Environmental tritium (3H) data also supports this finding. The presence of 3H in the river (average value: 8.8TU) endorse that it is mainly derived from the melting of relatively modern snow (average value: 12.4TU). These results suggest that the stable isotopes of oxygen and hydrogen in combination with radioactive 3H can be effectively used for the identification of the sources of water that sustains the river flow in the glaciated catchment of the Gangotri Glacier, and may contribute to a more robust assessment of the hydrological budget in the glaciated catchments of the Himalayan Region.

Steep gully slopes are widespread and have been recognized as the main sediment source on the Loess Plateau. Different vegetation growth may lead to the differences in soil properties and plant roots, and thus likely affects soil resistance to flowing water erosion, reflected by rill erodibility and critical shear stress. However, few studies have been conducted to evaluate this effect on steep gully slopes on the Loess Plateau of China. This study was performed to investigate the effects of vegetation growth on soil resistance to flowing water erosion on steep gully slopes, and quantify the main potential influencing factors on the Loess Plateau. Three typical shrub communities and four typical grass communities that distributed on different gully slopes were selected. 240 undisturbed soil samples were collected from these seven gully slope lands and one slope farmland (control), and were subjected to detachment by overland flow under six different shear stresses (6.64 to 17.85 Pa). The results showed that the mean detachment capacity of slope farmland was 6.9 to 47.8 times greater than those of steep gully slopes covered with different plant communities. The rill erodibilities of steep gully slopes covered with different plant communities reduced greatly by 77.0% to 95.1% compared to the control slope. The critical shear stress of slope farmland (2.72 Pa) was only 57.2% and 39.6% of that of shrubland (4.76 Pa) and grassland (6.88 Pa). Both shrub and grass communities were effective in reducing soil detachment capacity and rill erodibility, and increasing critical shear stress on steep gully slopes. But the effects were more obvious for the grass communities. The differences in rill erodibility between slope farmland and gully slope lands were mainly explained by the changes in root mass density (82.4%). Plant roots had strong direct effects on increasing soil cohesion (0.78), organic matter content (0.56), and water stable aggregation (0.92). Rill erodibility was negatively related to root mass density as an exponential function (p

Adding biochar to soil is an efficient method to improve soil physicochemical properties. Understanding the effect of this method on soil and water loss is also important. However, there is insufficient data available to assess this effect. Thus, a simulated rainfall (intensity 90 mm h−1) study was conducted to explore the effect of biochar particle sizes (2–1, 1–0.25, and 2 mm water-stable soil aggregate content, and soil saturated hydraulic conductivity (Ksat) from a perforated box (1 m long and 0.4 m wide) with a 27% slope gradient that contained soil, with a constant application rate of biochar at 1% (wt/wt). Soil without biochar was used as the control. The results indicated that biochar-treated soil delayed the time to runoff compared to the control by 12.67% to 32.58%, with the smallest particle size ( 2 mm water-stable soil aggregate content and Ksat relative to the control. We speculated that the positive effects of biochar on soil and water loss were possibly due to an improvement in soil physical properties, such as an increase in the >2 mm water-stable soil aggregate and Ksat.

Water erosion is a time-varying processes controlled by both rainfall and overland flow. A better understanding of dynamic changes in the sediment load and size distribution with various erosive forces can help to develop and verify erosion models. Here, a total of 11 laboratory simulation experiments were conducted in a 1 m by 3 m flume with 3 storm rainfall intensities (60, 90, 120 mm h−1) and 2 inflow rates (5, 7.5 L min−1) on a silty clay red soil. Time-series measurements of the quantity and size distribution of eroded materials were made during 50 min rainfall/inflow time. The mean weight diameter of the effective sediment, sediment enrichment ratio, average stream power and rainfall power were measured and calculated. Fine sediment particles were associated with the short-lived initial stage, which was combined with sheet flow erosion and splash erosion, whereas coarse particles were associated with the rill development and rill stable stages, which were dominated by rill erosion and interrill erosion, respectively. The

Geohazards often cause a lot of damage to human life and property. Among the geohazard mitigation measures, ecological restoration engineering is an ecomonic and widely-used one, but the effectiveness varies with the alternatives' settings and the local stand conditions, and there is a lack of effective means to assess it. The objective of this paper is to evaluate the effectiveness of vegetation restoration alternatives on mitigating geohazards in Bailong River Basin (BRB), where the soil erosion and debris flow are very severe. Given the significance of surface hydrological process in the formation of geohazards, the surface runoff depth (SRD) simulated by the Soil and Water Assessment Tool (SWAT) was chosen to evaluate the effectiveness of the mitigation alternatives. We designed four groups of ecological restoration scenarios, among which the first three groups returned the cropland with slope above 0, 15 and 25°, respectively, to one type of vegetation from evergreen forest, deciduous forest, mingled forest, shrub and grassland. The fourth group returned two slope levels of cropland to combination of two from the above five vegetation types. At the basin level, it was shown that all the alternatives could reduce the SRD. The evergreen forest alternative performs better than other vegetation types, and converting cropland above 15° is more efficient than converting cropland above 0 and 25°. The combination of evergreen and shrub in group 4 reduces SRD the most. At the subbasin level, the spatial heterogeneity of restoration alternatives effectiveness was shown. The reduction rate of SRD at the subbasin level reveals that the restoration measures would perform well in the northeastern basin and the eastern area of midstream. The reduction of SRD per unit returned cropland area reveals that the efficiency of reducing more SRD with less returned cropland is higher in the northeastern basin. Further, a map of most efficient group 4 scenarios at the subbasin level is obtained. Our work is expected to provide information regarding the establishment or improvement of ecological restoration policy in mitigating geohazards.

In the Sahel region, farmers have adopted various farming practices to improve agricultural yields in order to offset an increasingly variable climate regime and the extension of degraded land. This study analyses the functional behaviour of such three selected water-harvesting techniques (stone rows, zai and half-moon) as compared to the traditional tillage method through a comprehensive experimental setup monitored during three consecutive growing seasons (2015–2017). The results indicate that these farming practices allow a runoff reduction by 25 to 100%. We propose a continuous model simulating the hydrological dynamics of the farming techniques at plot scale. This model is able to reproduce accurately the observed runoff (R2 = 0.73 − 0.95), and gives an insight of the variability of the water storage for each type of techniques in response to the rainfall regime. It appears in particular that zai and half-moons are able to mitigate the effect of dry spells by sustaining available water for crops over extended periods up to three weeks, whereas the direct seeding and stone row techniques rapidly leads to plant water deficit after five days. Even though water infiltration is essentially fostered by surface water retention during rainfall events, our observations suggest that the changes induced to the hydrological dynamics by farming practices also affect soil physical, chemical and biological properties. These effects help completing the explanation of crop yield improvements, but raise some questions of soil evolution and farming practice performances in the long run.

Investigating the suspended sediment dynamic is useful for gaining a more comprehensive understanding of runoff and sediment yield process. The study analyzes the sediment flow behavior in relation to the flood patterns in the Xichuan River catchment on the Loess Plateau. Based on 23-year hydrological data collected from Zaoyuan hydrological station and K-medoids clustering method, one hundred and twelve flood events data were classified into four flood patterns. The hydrologic features of different flood patterns exhibit significant differences. The values of the mean runoff depth, the mean flood duration, and the mean flood peak discharge decreased as the following order: Pattern A > Pattern C > Pattern D > Pattern B. Each flood pattern results in differing levels of the event sediment yield (SY), the SY of Pattern A (10,275.33 t·km−2) and Pattern C (1196.39 t·km−2) were larger than those from Pattern B (218.84 t·km−2) and Pattern D (693.84 t·km−2). These results indicated that greater attention should be paid to Pattern A and Pattern C because of the largest sediment delivery effect. Multiple stepwise regressions analysis suggested that the contribution of main runoff-related factors to event sediment yield varied with different flood patterns. In addition, hysteretic analysis between suspended sediment concentration and runoff suggested that counter-clockwise and figure-eight loops were the dominant loops. The results provided a useful information to flood pattern classifications and suspended sediment dynamics research, and enriched the sediment control theory at the watershed scale.

To investigate the evolution characteristics of the Yichang–Chenglingji Reach (YCR) of the Middle Yangtze River and develop simulation methods, the temporal and spatial morphodynamic adjustments of the YCR were analysed comprehensively on the basis of runoff, sediment load, and cross-sectional profiles data at 220 cross sections from 2002 to 2016. Results showed that significant channel degradation has occurred in the YCR, especially in the low-flow channels, due to a drastic reduction in sediment yield since the operation of the Three Gorges Project (TGP). The variations of upstream flow and sediment regimes would drive equilibrium channels to become increasingly narrow and deep, and the current bankfull width and depth were less than their equilibrium counterparts in the recent period. However, the recent channel evolution was mainly characterized by the prominent channel deepening via a one-way deformation due to the large-scale bank revetments within the YCR, where the reach-scale bankfull depth increased by 1.6 m in the span of 15 years. A semi-empirical method for determining the equilibrium values of channel degradation and aggradation volume at the YCR was proposed on the basis of a comprehensive analysis of the effects of flow, sediment concentration, sediment gradation, and water depth. Moreover, the equilibrium values of the channel width and depth were estimated with the Least Action Principle method. The calculation methods for the equilibrium width, depth, width/depth ratio, and aggradation/degradation volume were combined with the Delayed Response Model (DRM). Then, the methods for calculating the variations in channel geometry and aggradation/degradation volume were derived. Results showed that the proposed methods effectively simulated the channel geometry and cumulative erosion volume in the YCR from 2002 to 2016. In addition, the response of the channel evolution in the YCR was closely related to the previous four-year hydrological conditions, implying that channel evolution may lag behind the variations of flow and sediment discharges.

In Japan, moso-bamboo (Phyllostachys edulis (Carriere) J. Houz.), an invasive species, has spread into and replaced surrounding broadleaved and coniferous forests because of the inactive management of moso-bamboo forests. Some local governments in Japan have speculated about an increase in soil erosion caused by the replacement with moso-bamboo forests. To evaluate the impact of such replacement on soil erosion, the soil erosion rate in a moso-bamboo forest was compared with those in an evergreen broadleaved forest and a coniferous forest. We established three plots (width 1 m, length ca. 2 m) in each forest and measured overland flow and soil erosion in two continuous periods (Period I: July 26, 2012–April 26, 2013; Period II: April 26, 2013–July 17, 2014). In Period I, the soil erosion rate in the moso-bamboo forest (0.08–0.10 g m−2 mm−1) was not significantly higher than that in the broadleaved forest (0.27–0.55 g m−2 mm−1) and the coniferous forest (0.16–0.27 g m−2 mm−1). In Period II, we removed understory vegetation and litter from two of the three plots in each forest. In Period II, the plots with such removal had higher soil erosion rates than the control plots. The soil erosion rate for the removal plots of the moso-bamboo forest was less than half of those of the broadleaved and coniferous forests. Although rock fragment cover on the soil surface and shear strength of the topsoil did not differ significantly among the three forests, root density in the moso-bamboo forest was much greater than those in the broadleaved and coniferous forests. These results suggest that a large amount of roots in moso-bamboo forests could reduce soil erosion there. The findings of this study show that moso-bamboo forests have strong resistance against soil erosion, so the replacement of broadleaved and coniferous forests by moso-bamboo forests would not seem to imply an increase in soil erosion.

Spoil heaps are the main sources of soil erosion on disturbed land surfaces as an artificial accelerated erosion form, and rock fragments are an important component of spoil heaps. This study examined different fragment contents (0, 20, 40, 60 mass percentage) and sizes (1–4, 4–7, 7–10 cm) on hydrological processes, sediment yielding processes and rock fragment cover evolution through three sequential simulated rainfalls with a constant intensity of 1.5 mm min−1. The rock fragments in spoil heaps were found to reduce the soil loss amount by 35.23–76.84% through effects on runoff production and rock fragment cover. Runoff rates decreased with increasing rock fragment content, and size class 4–7 cm had the strongest reduction effect, but for a definite treatment runoff rates have little change in three rainfall events. The expanding rock fragment cover with cumulative rainfall in the multiple rainfall events, which increased fastest during the first rainfall period led to a significant decreasing soil detachment rate. Multiple regression analysis shows that the average detachment rate under each rainfall event could be estimated using a power function of average runoff rate and median rock fragment cover. These findings indicated that the presence of rock fragments in spoil heaps has an obvious mitigating effect on soil erosion, with the rock fragment content making a larger percentage contribution than rock fragment size.

The paper focuses on the generation of floods as a principal soil threat and on soil erosion as an additional soil threat on arable lands of hillslope areas. As the most important component of floods causing the degradation of soils on arable lands, surface runoff is analysed in this study. The protective effect of crop management on the generation of surface runoff and sediment transport on arable lands is estimated on a plot and slope scale. The site of the case study, which is located in the Myjava river basin in western Slovakia, is a hilly agricultural field with an area of 29 ha; it is characterised by arable soil, extreme erosion processes, and muddy floods. Field rainfall simulation experiments were combined with physically-based modelling for studying the formation of surface runoff under various soil covers. The field experiments consisted of simulating runoff generation from artificial rainfalls using the Eijkelkamp rainfall simulator on experimental plots with a focus on estimating the volume of surface runoff, the mass of sediments transported by the surface runoff, and the time to runoff. The volumes of the surface runoff and the values of the time to runoff have been applied in the parameterisation of the SMODERP physically-based hydrological model. The hydrological modelling of the surface runoff on the selected slope profile quantified the protective effect of various soil covers on reducing surface runoff. The outcome of the modelling was the maximum allowed lengths of the slope that represent the crucial values for flood and erosion control. When exceeding these critical values, protective measures, e.g., vegetation strips, should be proposed.

Rock outcrops are frequently visible in terrestrial landscapes, typically in karst. However, there has been insufficient research conducted on their effects on the formation of soil water and nutrients heterogeneity in nearby soil patches. In: 1) a rock desertification ecosystem, 2) an anthropogenic forest ecosystem, and 3) a secondary forest ecosystem in Shilin, Southwest China, rock occupancy ratio was measured, water received by and subsequently funneled off by rock outcrops was quantified, and their concentrations of the total organic carbon, nitrogen, phosphorus, and potassium were determined. Receiving rate Rr of those elements of the remaining soil patches in various 2 m × 2 m soil + rock outcrop samples were calculated, and r200 at which Rr of the remaining soil patch was twice that without rock emergence was calculated to evaluate the heterogeneity difference among different elements in different ecosystems. There were 1.43–5.44 folds differences between Rr under the highest rock ratio (79.4%) sample and the rate of non-rock emergence sample for water, organic carbon, nitrogen, phosphorus, and potassium in the three ecosystems respectively, indicating a large supply heterogeneity for those elements within an ecosystem and between ecosystems. The r200 were between 47% (water, at rock desertification ecosystem) to 90% (potassium at rock desertification ecosystem, depending on the receiving rate and funneling rate of the rock for different element in different ecosystem. In conclusion, large supply heterogeneity has derived from high variation of rock runoff determined by rock emergency ratio, the rate of receiving and the rate of funneling off by the rock. Our study provided new evidence to trace soil and water heterogeneity of microhabitats in rocky ecosystems. Additionally, rock outcrop is also an important factor in evaluating hydrological and related nutrient characteristics in rocky ecosystems.

Cutslopes are the most important source of sediment among other parts of forest roads network. A significant amount of runoff and sediment is observed in Hyrcanian forests because of the fine-textured soil. This study investigated the effectiveness of three treatments of jute cover (JC), mulch cover (MC) and bare cutslope as control plots (CP) under the natural rainfall condition. Two months investigation on two new and old roads with silty-clay cutslopes was done. Correlation between some of soil properties, soil loss and runoff showed that the sediment concentration was increased with increasing in soil bulk density. Runoff volume showed a significant negative correlation with the percentage of organic matter and a positive correlation with the plastic limit. With runoff volume increasing, sediment concentration and soil loss were significantly increased. Analysis of the results showed that in both new and old roads, the treatment of JC is superior. This treatment has reduced soil loss by 9.68 times compared to CP treatment. The treatment of JC compared to the MC on a new cutslope and an old one has reduced soil loss by 2.77 and 2.54 times. Also, JC have reduced soil loss by 2.67 times compared to the MC. The total cost per square meter of JC is US $ 0.21 and this amount is equivalent to $ 0.26 for the MC. According to the results, it is suggested that soil protection and bioengineering designs should be focused on the use of JC.

The aim of this work was to assess the accuracy of direct runoff depth calculated according to an original Soil Conservation Service – Curve Number (SCS-CN) method and a modified Sahu-Mishra-Eldho (SME) method based on different sources of information on land cover. Main novelty of this work is using Database of topographic objects (BDOT10k) instead of Corine Land Cover (CLC) for the assessment of land cover in a catchment. The research was performed in the Kamienica river, a right tributary of the Dunajec, Poland. The effect of land cover data on runoff depth was assessed with the original SCS-CN method, and modified SME method. The value of CN parameter was estimated using two databases on land use, CLC and BDOT10k. BDOT10k was proven to be a considerably more precise land cover database that enabled more accurate interpretation. The study demonstrated the highest accuracy of direct runoff calculation with SME-CN method, irrespective of the approach used for determination of the catchment land use. The use of SME-CN instead of the original SCS-CN method provides much more accurate prediction of direct runoff in a catchment.

Two variants of the Instantaneous Unit Hydrograph model based on a Geomorphological association of linear Reservoirs (IUHGR), incorporating the Spatial Variability of Rainfall (SVR), have been developed. The proposed models are based on the Geomorphological Reservoirs (GR) scheme consisting of a cascade of linear reservoirs aggregating sub-watersheds. The model, in its first version, was formulated so that it incorporated a spatial variability pattern of rainfall associated with a certain frequency and oriented towards its application in the field of hydrological design. This model was considered to be stationary in the time (GRSVR(s)) for being linked to some design conditions. The second version of the model is applicable to the simulation of real events, where there is a dynamic (GRSVR(m)) spatial distribution of rainfall that varies in time, as in the case of the movement of rainstorms. Both models permit the input of relevant information on the spatial variability of the rainfall, taken from different rain gauge records, without losing the simplicity of the GR model with a single parameter, which represents the hydrological time response of the watershed. The models have been calibrated and validated with the data from one gauged watershed in northern Spain. The analysis conducted in both cases showed that the models which contemplated the spatial variability of the rainfall, GRSVR(s) and GRSVR(m), were capable of simulating rainfall variability effects in the surface runoff hydrograph better than the GR model, which averages the precipitation values recorded in the different rain gauges.

The role of weeds in soil conservation in agroforestry systems has been largely ignored. We used the Land Use Change Impact Assessment (LUCIA) model to simulate the effects of weed management on erosion in rubber plantations (Hevea brasiliensis Muell. Arg). In order to quantify the impact of a dynamic, spatially explicit multi-layer plantation structure on erosion processes in agroforestry systems, we updated LUCIA's erosion module. Its new version simulates soil detachment due to rainfall and runoff, considering the separate effects of the tree canopy and surface cover on soil erosion. The updated LUCIA model was calibrated and validated based on an established rubber plantation experiment in Xishuangbanna, Southwest China, to evaluate the impact of different weeding strategies on soil loss. The model successfully represented the impact of the dynamic multi-layer structure on erosion and was able to predict well the effects of weed management on soil loss and runoff at the test site over 1 year, with a modelling efficiency (EF) of 0.5–0.96 and R2 of 0.64–0.92. Subsequently, we validated the ability of the model to simulate surface cover changes under rubber plantations of different age (up to 40 years). Simulation outputs for 4-, 12- and 18-year-old rubber plantations revealed satisfying to good results. However, the predicted change in surface cover for old rubber plantations (25- and 36-year) failed to meet the field trends. The model predicted the greatest erosion in the year when the rubber canopy started to close. During this period, weed growth was limited by light, while litter input from rubber was insufficient to provide good soil cover. Four weeding strategies (“clean-weeding”, “twice-weeding”, “once-weeding” and “no-weeding”) were designed for scenario simulations. Based on the results of 20-year runs, we concluded that “once-weeding” and “no-weeding” both efficiently minimized soil loss during one rotation length. A high degree of surface and weed cover (over 95% and 60%) under “no-weeding” makes this management strategy with dense undergrowth hardly acceptable by local farmers due to reduced tree accessibility for tapping and increased potential danger through poisonous caterpillars. “Once-weeding”, on the other hand, controlled overgrowth of understory vegetation by keeping weed cover below 50%. We therefore suggest “once-weeding” as an improved herbicide management strategy in rubber plantations, to meet ecological system service maintenance and to facilitate adoption in practice.

Land Use Land Cover (LULC) change significantly affects hydrological processes. Several studies attempted to understand the effect of LULC change on biophysical processes; however, limited studies accounted dynamic nature of land use change. In this study, Soil and Water Assessment Tool (SWAT 2012) hydrological model and statistical analysis were applied to assess the impacts of land use change on hydrological responses such as surface runoff, evapotranspiration, and peak flow in Gummara watershed, Ethiopia. Moreover, the effects of static and dynamic land use data application on the SWAT model performance were evaluated. Two model setups, Static Land Use (SLU) and Dynamic Land Use (DLU), were studied to investigate the effects of accounting dynamic land use on hydrological responses. Both SLU and DLU model setups used the same meteorological, soil, and DEM data, but different land use. The SLU setup used the 1985 land use layer, whereas the DLU setup used 1985, 1995, 2005, and 2015 land use data. The calibration (validation) results showed that the model satisfactorily predicts temporal variation and peak streamflow with Nash Sutcliffe Efficiency (NSE) of 0.75 (0.71) and 0.73 (0.71) in the DLU and SLU setups, respectively. However, the DLU model setup simulated the detailed biophysical processes better during the calibration period. Both model setups equally predicted daily streamflow during the validation period. Better performance was obtained while applying the DLU model setup because of improved representation of the dynamic watershed characteristics such as curve number (CN2), overland Manning's (OV_N), and canopy storage (CANMX). Expansion of agricultural land use by 11.1% and the reduction of forest cover by 2.3% during the period from 1985 to 2015 increased the average annual surface runoff and peak flow by 11.6 mm and 2.4 m3/s, respectively and decreased the evapotranspiration by 5.3 mm. On the other hand, expansion of shrubland by 1% decreased the surface runoff by 1.2 mm and increased the evapotranspiration by 1.1 mm. The results showed that accounting DLU into the SWAT model simulation leads to a more realistic representation of temporal land use changes, thereby improving the accuracy of temporal and spatial hydrological processes estimation.