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• The stable macroaggregate structure makes the erodibility of forest soil at a low level. • Mean weight diameter and rill erodibility has a negative power function. • Acidobacteria and Basidiomycota are the key groups in resisting soil rill erosion. • SOC has strong regulatory effects on the soil key group of microorganisms. How microbial communities respond to soil aggregation and rill erosion resistance has rarely been addressed. Such a knowledge gap hinders the practice of guiding sustainable soil management. Herein, the community composition of bacteria and fungi was evaluated by 16S rRNA gene sequencing. We measured critical shear stress (τc) and rill erodibility (k d) by self-made jet device. The effects of microorganism on soil aggregation and rill erosion resistance were quantitatively analyzed under different land uses. The results indicated that the forest soil supported the colonization and enrichment of Acidobacteria and Basidiomycota on account of the unique vegetation and higher soil organic carbon (SOC). The forest and shrubland contained higher macroaggregate and mean weight diameter (MWD) than those of cropland and bare land, while rill erodibility (k d) was the opposite. MWD and k d had a negative power function (y = 105.64x−0.69). The biotic factors explained 73.50% of the variation in rill erosion resistance and soil aggregation, indicating microorganism are more important in acting on rill erosion resistance. This study suggests that SOC had strong regulatory effects on the soil key groups of bacteria and fungi assemblages; furthermore, their interaction facilitated the formation of stable macroaggregates. The stable macroaggregate structure and vegetation cover make the erodibility of forest soil at a relatively low level. However, cropland are not conducive to stability of aggregates, which easily causes soil erosion. Improving soil SOC and maintaining the relative abundance of key groups of microorganism would be conducive to soil sustainable developing. [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]

Erosion, flood, and overflow events are frequently experienced due to changes in the land use in watersheds where human impacts are intensive. It is important to understand the effects of land use types on erosion at a watershed scale. This knowledge can then be used to manage soil and water resources in watersheds better. The aim of this study is to determine the effects of different land uses/covers on the surface runoff and soil loss by using a rainfall simulator in natural land conditions in the Niğde Akkaya Dam watershed with semi-arid conditions. For this purpose, 5 cultivated lands with different product patterns with similar conditions (apple orchard (A), potato cultivation area (P), bean cultivation area (B), clover cultivated land (CL), abandoned cultivated land (AB), plantation areas (cedar (C) and almond (AL)), and pasturelands covered with Thymus sp. (T), Agropyron sp. (AG) and Stipa sp. (S) were selected for the applications. The applications were carried out in two repetitions on circular test parcels of 0.28 m 2 established in these lands. During the land applications, the characteristics of surface runoff (ponding time, surface runoff start time, average surface runoff rate, runoff coefficient) and the average sediment concentration in the surface runoff water were determined. The data obtained were evaluated by using the ANOVA, Duncan's test, and Pearson correlation analysis test and SPSS statistical program. The results of the study revealed that the surface runoff occurred in the abandoned cultivation area, bean cultivation area, potato cultivation area, and thyme-covered pastureland in a short time. The runoff coefficient values by the land cover are sorted from high to low as B > T > P > A > AB > AL > C > CL > S > AG. The sediment concentration in the runoff water is sorted from high to low as T > P > B > AB > AL > A > C > S. When the situation was evaluated in terms of the soil loss (erosion), it was concluded that the sorting is as P > T > A > AB > B > AL > C > S > CL. [ABSTRACT FROM AUTHOR]

The aim of this paper is to assess the impacts of projected climate change on a Mediterranean catchment, and to analyze the effects of a suite of representative land use practices as an adaptation tool to reduce climate change-driven erosion and hydrologic extremes. Relevant climatic variables from the ERA-Interim global atmospheric reanalysis of the European Centre for Medium-Range Weather Forecasts (ECMWF) were downscaled for the study area, and perturbed with the anomalies of 23 global circulation models for three emission scenarios (B1, A1B and A2). Both a projected daily rainfall time series for the period 2010–2100, and a single precipitation event with a one-hundred year return period were used to assess the impact of climate change. The downscaled data were fed into a distributed hydro-sedimentary model (TETIS) with five land use configurations representative of future demographic tendencies, geographical characteristics and land management policies (e.g. European Union CAP). The projected changes showed a general decrease in runoff and sediment production by the end of the century regardless of land use configuration. Sediment production showed a positive relationship with an increase in agricultural land and a decrease in natural land under present day agricultural management. According to our simulations, some conservation practices in agriculture can effectively reduce net erosion while maintaining agricultural production. As such, they can play a critical role as an adaptation tool to reduce climate change impacts in the 21st century. [ABSTRACT FROM AUTHOR]

• A field investigation of gully erosion was conducted in a 393 km2 area. • Larger ridge orientation angle and sunny slope were conducive to gully development. • Gully volume can be well predicted by a power function of gully area. • Soil loss caused by gully erosion occupied by 65% in northeast China. Gully erosion, one of the most damaging forms of land degradation, destroys farmlands and threatens grain and ecological stability. Approximately 295,000 gullies have formed in the Mollisols region of northeast China (NEC), while the actual severity of gully erosion remains unclear. This study aims to clarify gully morphology, factors influencing gully morphology, and contribution of gully erosion to soil loss through a 393 km2 field investigation in a typical and representative Mollisols region of NEC. There were 1048 gullies observed, with an average length, top width, depth and width-depth ratio of 522.32 m, 15.05 m, 2.77 m and 7.16, respectively. Over 70% of gullies had a length, top width and depth of 100–500 m, 3–20 m and 0.5–3 m, respectively. The three types of gullies, classified based on where the gully head developed (GF, farmland; GR, unpaved road; GW, woodland), had significantly distinct morphologies, with GW being broader and deeper and GF being longer. Notably, 56.2% of gullies are GF, accounted for 74.84% of the total gully area and 67.04% of the total gully volume (V). V of GF, GR and GW could be well explained by a power function of gully area (A). Gully density (gully length per unit area, GD, km km−2) and ground lacerative degree (gully area per unit area, GLD, km km−2) increased with slope gradient, and first increased and then decreased with slope length. Gully development was more favorable of sunny slope and a larger angle between gully and ridge orientation. The annual eroded soil from the gully was 1.86 times of that from the hillslope across the region during 2013–2018, contributing 65% of region eroded soil. This clearly identifies the severity of gully erosion and substantiates gully erosion risks to valuable mollisols and therefore food security. An urgent need exists to implement gully erosion control practices in this area. [ABSTRACT FROM AUTHOR]

• C-factor is estimated through a spatiotemporally exhaustive approach. • The monthly application accounts for the coefficient's intra-annual variability. • A novel LULC map of unprecedented detail was used to describe land distribution. • All monthly C-factor values are almost double than the mean annual stationary one. • The new C-factor displays high upscaling and reproducibility potential at EU scale. The cover management factor (C-factor) calculation requires the assessment of the intra‐annual spatiotemporal variability of biomass cover, owed to the natural growth cycle of vegetation and the impact of agriculture on land cover. However, this is frequently omitted, and the vegetation conditions are approximated by assigning constant values to static classified Land Use/Land Cover (LULC) maps, such as the Coordination of Information on the Environment (CORINE) Land Cover (CLC). Using as test site the Sperchios River catchment, Central Greece, this study introduces a new approach to estimate C-factor in a spatiotemporally exhaustive manner. The goal is to increase estimation accuracy in erosion modelling applications. The C-factor computations are performed on monthly scale, based on LULC maps that portray the basin's agricultural areas in unprecedented detail. The methodology involves the use of a biophysical index, namely Fraction of Vegetation Cover (F cover) and empirical literature data on crop types. F cover was developed from Sentinel-2 (S2) imagery in 10-m analysis. Such analysis (compared to the 300-m one provided by the EU) is a major improvement towards a more precise estimation of C-factor. The study identified the monthly C-factor fluctuation at basin scale, and the most susceptible months seasons at localities in terms of land cover/soil loss potential. The higher C-factor values were acquired in October and the lower in May. Mean annual (numerical) C-factor complies with the value of July. All monthly values are significantly higher – almost double – than the mean annual stationary one. The revealed patterns would not have been detected in a lower temporal (e.g., annual) resolution without the incorporation of vegetation density seasonality. The study shows high reproducibility and upscaling potential, as the utilized datasets are available in all European Union (EU) Member States, having similar structure, thus they can be harmonized towards a unified continental approach. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil C, N and P stoichiometric ratios were influenced by land use types under different erosion conditions. • Soil C, N and P stoichiometry changed more significant under SE condition. • Higher P stocks and lower C:N:P stoichiometric ratios were detected in PD and UL than in WL. • Land-use type affected C, N and P stoichiometry mainly by changing soil porosity and texture. Irrational land-use can accelerate soil erosion by deteriorating soil structure and depleting soil nutrients, especially profoundly alter soil organic carbon (C), total nitrogen (N), total phosphorus (P) contents and stocks. However, it remains unknown how soil C, N, P stoichiometry patterns are affected by land-use type and soil erosion. This study was carried out to examine the soil C:N:P stoichiometry patterns in woodland (WL), upland (UL), and paddy (PD) at soil depths of 0–10, 10–20, and 20–30 cm under collapsed gully erosion (CGE) and sheet erosion (SE) conditions in lateritic red soil region. Compared to WL, C content and stock decreased by 19.1–31.9 g kg−1 and 12.8–31.7 Mg ha−1, but P content and stock increased by 4.9–7.4 g kg−1 and 6.7–9.9 Mg ha−1 in UL soil at 0–30 cm, resulting in a decrease in C:N, C:P and N:P ratios by 8.6–14.8, 23.0–28.6 and 0.7–1.0, respectively. In addition, N, P contents and stocks increased by −0.04–1.8 g kg−1, 4.1–10.5 g kg−1 and 1.8–1.1 Mg ha−1, 7.0–8.2 Mg ha−1 in PD soil at 0–30 cm, resulting in a decrease in the ratio of C:N, C:P and N:P by 8.1–10.6, 20.7–26.0 and 0.6–0.8, respectively. Furthermore, C, N, P contents, stocks and C:N ratio in UL and PD soils were more significant under SE than CGE condition with, while it was opposite trend in WL at 0–30 cm depth. Soil C, N, P contents and stocks significantly decreased with soil depth, while no significant changes were detected on their stoichiometric ratio. Soil porosity and texture had significant contribution to C, N and P stoichiometry by PCA and RDA analysis. Our results demonstrate that the intensive agricultural practices changing soil porosity and texture under SE condition led to more pronounced differences of soil C, N, P and their stoichiometric ratios in lateritic red soil region. [ABSTRACT FROM AUTHOR]

Abstract: The novel catchment scale erosion and sediment delivery model INCA-Sed was applied to four small study catchments in Finland. Three of these, the Mustajoki, Haarajoki and Luhdanjoki, are headwater catchments located in central Finland. The associated rivers have differing morphological characteristics varying from a ditch to a small river. Soil textures in the area are derived from moraine deposits and are largely sand and gravel. The Mustajoki and Haarajoki catchments are forested and only 10% of the area is under cultivation. In the Luhdanjoki catchment agricultural fields cover 40% of the area. The fourth study site, the Savijoki catchment, represents an intensively cultivated area in south-western Finland. Cultivated fields cover 40% of the catchment area, and they are located on clay soils along the river. The INCA-Sed model was able to capture both the correct magnitude and seasonal behaviour of suspended sediment concentrations in the rivers, as well as the correct magnitude of the sediment load derived from different land use classes. Small differences in river morphology and soil textures between the catchments have a significant influence on suspended sediment concentration in the rivers. Correct timing of suspended sediment concentration peaks is not, however, captured by the INCA-Sed model, which may be due to the stochastic nature of erosion and delivery processes at the catchment scale which are not taken into account in the parameter values used in the modelling. Parameter values were estimated from previous researches based on average process loads. The INCA-Sed model was, however, generally found to be a suitable tool for evaluating effects of land use change on erosion and sediment delivery in Finland as it correctly reproduces spatial and seasonal variations in sediment delivery, in addition to annual averages with spatial and temporal variations. [ABSTRACT FROM AUTHOR]

Abstract: Tropical deforestation and land use change is often perceived as the major cause of soil loss by water erosion and of sediment load in rivers that has a negative impact on the functioning of hydropower storage reservoirs. The Sumberjaya area in Sumatra, Indonesia is representative for conflicts and evictions arising from this perception. The purpose of this study as part of a Negotiation Support System approach was to assess sediment yield both at plot and catchment scale and to relate it to a variety of possible clarifying factors i.e. land use, geology, soil and topography. Sediment yield at catchment scale per unit area, was found to be 3–10 times higher than soil loss measured in erosion plots. A stepwise regression showed that the dominant factors explaining sediment yield differences at catchment scale in this volcanic landscape were a particular lithology (Old Andesites) and slope angle followed by the silt fraction of the top soil. In lithologically sensitive areas soil loss at the plot scale under monoculture coffee gardens decreases over time from on average 7–11Mgha−1 yr−1 to 4–6Mgha−1 yr−1, mainly because of the development of surface litter layers as filters and top soil compaction in the areas without litter, but remains higher than under shade coffee systems or forest. The runoff coefficient under monoculture coffee remains on average significantly higher (10–15%) than under forest (4%) or under shade coffee systems (4–7%). In lithologically stable areas soil loss remained below 1.8Mgha−1 yr−1 and the runoff coefficient below 2.5% under all land use types, even bare soil plots or monoculture coffee gardens. Less than 20% of the catchment area produces almost 60% of the sediment yield. The reduction of negative off-site effects on e.g. the life time of a storage reservoir would benefit greatly from an improved assessment of the lithologies in volcanic landscapes and the consideration of potential sediment source and sink areas. In lithologically sensitive areas, a shift from sun to shade coffee systems may result in reducing surface runoff and soil loss, although water erosion at the plot scale is not the main contributor to sediment yield at the catchment scale. The quantification of land use effects on dominant erosive processes such as river bank and river bed erosion, landslides and the concentrated flow erosion on footpaths and roads can contribute to more targeted efforts and relevant incentives to reduce (or live with) sediment load of the rivers. [Copyright &y& Elsevier]

Abstract: The Holocene landscape history and historical soil erosion were reconstructed at Albersdorf (Schleswig-Holstein, Germany) from soils and colluvial layers. In contrast to many landscapes in central Europe, agricultural land use and soil erosion were more frequent during pre-historical times, whereas it has almost ceased after the advent of history. Pre-historical soil erosion rates from about 0.1 to 6.9 t ha−1 a−1 were reconstructed with no significant differences between the prehistoric cultural phases. The study of buried soils within the soil/soil-sediment-sequences provided evidence for an acceleration of soil formation processes probably as a consequence of excessive prehistoric woodland pasture on poor sandy soils. [Copyright &y& Elsevier]

• Productivity index based soil loss tolerance limits were estimated. • PI in different phases of erosion varies between 0.748 and 0.551. • Soil loss tolerance limit based on PI ranged from 6.67 to 12.92 Mg ha−1 year−1. • Severely eroded soils have lower microbial biomass carbon, and poor soil quality. Land area is dwindling due to degradation, both natural and anthropogenic, therefore, it is reasonable to save this important resource and put focus on achieving land degradation neutrality (LDN). An Investigation was taken to know the impact of erosion on soil physico-chemical and biological properties both in fertilized and unfertilized conditions in four phases of erosion viz., slightly eroded (0.5% slope), moderately eroded (2.5% slope), severely eroded (4.5% slope) and very severely eroded (9.5% slope). Productivity index (PI), vulnerability curve, soil loss tolerance limits (STL), soil quality index (SQI) and relative soil quality index (RSQI) were estimated for all phases of erosion. As the severity of erosion increases the soil quality and productivity index (PI) decreases. Very severely eroded soils have lower PI, SQI and RSQI as compared to slightly eroded soils. However, land use under fertilized condition have better soil quality with SQI value of 143.00 and 118.00 in slightly eroded and very severely eroded soils, respectively, compared to 126.00 and 106.00 in non-fertilized condition. Similarly, the productivity index ranged 0.748 in slightly eroded phase to 0.651 in severely eroded phase under fertilized condition. Compared to slightly eroded soil, severely and very severely eroded soils have lower microbial biomass carbon (MBC), CO 2 evolution and dehydrogenase activities. Assessment of soil loss tolerance limit based on PI revealed that it ranged from 6.67 to 12.92 Mg ha−1 year−1 which implies that land degradation took place in the more eroded soils which needs higher priority in order to bringing these eroded land to degradation neutrality (LDN), and also requires suitable soil conservation interventions in different phases of erosion. [ABSTRACT FROM AUTHOR]

Abstract: Abandonment of agricultural land is one of the main changes in Mediterranean land use. To mitigate runoff and erosion from abandoned land, it is necessary to identify locations that are vulnerable to erosion as a result of land abandonment. The objective of our study was to identify vulnerable areas for gully erosion using different scenarios of land abandonment in Southeast Spain. The study area was the Carcavo basin, a semi-arid catchment in the province of Murcia (Southeast Spain). A preliminary field survey confirmed the assumption that abandoned fields have more gully erosion compared to cultivated fields. This can be explained by the quicker concentration of runoff on abandoned land due to crust formation and reduced surface storage capacity. Next we simulated the spatial dynamics of land abandonment with a spatially explicit land use change model for the period 2004 to 2015 for four different land use change scenarios. The results of the simulation were used to identify vulnerable areas for gully erosion by a simple GIS-model based on the controlling factors of gully erosion. The potentially vulnerable areas for gully erosion increased for the different scenarios ranging from 18 ha to 176 ha. Most of the vulnerable areas are located around channel heads or along channel walls. The combination of more gully erosion on abandoned fields and an expected increase of land abandonment are potentially a big problem in relation to land degradation and reservoir sedimentation. The identification of vulnerable areas enables soil conservationists and engineers to mitigate gully erosion by applying preventive conservation practices. [Copyright &y& Elsevier]

Abstract: The present work deals with a large area of the Marche–Abruzzi monoclinal relief which is made up of a clayey sediment succession with sandy–conglomeratic levels alternating at varying stratigraphic heights. The east-verging monocline was generated by an intense Quaternary tectonic uplifting. It differs approximately in the west-east and in the southern directions forming three wide morphostructures. The deep fluvial down-cutting disjointed the monoclinal relief into a succession of high hills which give the area a typical cuesta morphology, with fronts facing the western quadrants. The present study aims at contributing to the knowledge of recent slope morphodynamics by analyzing the spatial distribution and state of activity of fast hydro-erosion processes and superficial mass movements. Correlations are made between these phenomena and the morphotectonic and lithological features of the various sectors in the area, with particular reference to agricultural land use. The present research underlines how the badlands represent the most spectacular form of fast erosion, whereas the landslide phenomena, which affect the prevalently loamy–clayey eluvial–colluvial covers, are the most widespread processes. Despite the distribution, density and recent, or current, evolutionary trends, are generally associated with different morphostructural features of the various sectors of the area, they prove to be strictly controlled by agricultural exploitation and by the connected techniques and types of cultivation. [Copyright &y& Elsevier]

Abstract: The introduction of agriculture in the late 1800s and early 1900s brought about many changes in the natural prairie landscape of western Canada. The objective of this research project is to evaluate landscape response to land use change by relating observed changes in the sedimentary record of a lake drainage basin to documented land use change that has occurred since the onset of settlement. A 52 cm lake sediment core was sectioned into 1 cm layers. The sediment was separated into allogenic and authigenic fractions using a wet chemical extraction technique. Close interval 210Pb dating enabled the calculation of sediment and elemental influx rates. Prior to European settlement, erosion rates were low (<0.1 Mg ha−1 year−1). In the 1910s, when the first settlers arrived in the area, erosion rates increased, and in the 1920s and 1930s, when the area of improved land rapidly increased and conditions were dry, erosion rates reached peaks of 1.5 and 2.2 Mg ha−1 year−1. Erosion rates in the latter part of the 20th Century range from 0.6 to 0.7 Mg ha−1 year−1. The composition of the allogenic fraction in the most recent, black sediment at the top of the core shows high concentrations of Ti and Zr, indicating a large contribution of topsoil to the allogenic fraction. In addition, elevated concentrations of Zn, Ni, Mo and U are likely explained by the application of phosphate fertilizers. Because of sediment deposition within the basin, e.g., on concave footslopes and on the valley floor, the erosion rates derived from the Thunstrom Lake core should be interpreted as net rates that likely mask values that are much higher locally within the basin. As a result, this study provides information on the erosional response of the prairie landscape to recent changes in land use at the scale of the Thunstrom Lake basin, but not necessarily on the sustainability of the soil as a resource, which would require information at the much smaller scale of the individual field. [Copyright &y& Elsevier]

Abstract: The spatial and temporal dynamics of stream net density (SND) within the Central and Southern parts of the Russian Plain during the last two centuries are studied by comparison of historical cartographic sources. A significant decrease of SND is observed in the forest–steppe and steppe zones. The maximum SND decrease is detected at the northern edge of the steppe zone, where SND values in the middle of the 20th century were only 50–60% of those at the beginning of the 19th century. Two stages of permanent stream disappearance were found within the study area: (1) The end of the 18th century to the first half of the 19th century, where the SND decrease was associated with a high frequency of droughts, that coincided with an expansion of the area of arable land, and (2) the last quarter of the 19th century, where the SND decrease can be explained by the extreme erosion rates resulting from the expansion of cultivation over steep slopes during the expansion of arable cultivation after the 1861 land reform. The roles of regional climate dynamics and land use change are confirmed by hydrological and meteorological data coupled with data on anthropogenic gully formation. Detailed studies of SND dynamics in a number of key basins provide a basis for understanding the mechanisms of SND reduction. [Copyright &y& Elsevier]

Abstract: Forest clearance between the 1890s and the early 1920s, subsequent scrub growth, and commencement of an afforestation program in 1979, modified the pattern and rate of sediment delivery to valley floors via shallow landslides and gully complexes in a steep headwater catchment (4.8 km2) in New Zealand. Analysis of the historical record, air photograph interpretation, and field survey indicates that both erosion types occurred across the catchment in the 1938 storm, aggrading channel beds and widening the active channel zone. In contrast, a 1 in 100 year event in 1988 (Cyclone Bola) induced numerous shallow landslides, but erosion of gully complexes was largely restricted to subcatchments that retained pasture, and the geomorphic impact of this event on channels was small. The changing volume and calibre of materials delivered to the valley floor, and the distribution of gully complexes, altered patterns and rates of channel adjustment after the events, and the resulting sediment flux. Development of gully complexes maintained coupling processes with channels for periods up to 102 years, forming wide channels in downstream reaches. Upstream–downstream connectivity along the trunk stream was altered by the formation of a large debris fan at the confluence with a tributary subjected to gully complex erosion. In contrast, slopes subjected to shallow landslides became decoupled from channels within 10 years, accelerating channel degradation and narrowing. Effective conveyance of a large volume of fine-grained materials promoted immediate aggradation of gentle-gradient channels downstream. As gully complex areas stabilized following an increase in forest and scrub cover, channel courses became significant sediment sources. Although shallow landslide activity will continue to induce intermittent aggradation in the future, it is inferred that average sediment yield will continue to diminish to levels approaching those experienced prior to clearcutting, and the pattern of sediment flux will recover by 2030. [Copyright &y& Elsevier]

Abstract: Linear erosion (LE) induced either by piping or overland flow is one of the most active factors in the evolution of soils. During single storm events LE may remove enormous amounts of soil material from the uplands to the bottomlands and has thus become a broad challenge for food supply, food security, and human health. Recent and rapid changes in land-use and climate patterns in the sloping lands of tropical areas may dramatically increase LE. Our main objective was to investigate to what extent one could use direct flow velocity estimations from dynamic models for predicting LE initiation and development at the event level. The second objective was to estimate the impact of expected land-use and climate changes on LE. The study was conducted in the 0.62 km2 watershed of northern Laos presented in. Field observations of the formation and the development of LE features throughout 2001 were compared to flow velocity estimations from an existing surface water routing algorithm developed at Utrecht University ([De Roo, A.P.J., Wesseling, C.G. and Ritsema, C.J. 1996. LISEM: a single event physically based hydrologic and soil erosion model for drainage basins. I: theory, input and output. hydrological processes 10 (8): 1107–1117.]). In 2001, two main rainfall events were responsible for the formation or development of 14 linear features with a total length of 972 m and an erosion rate of 3.5 Mg ha−1. The water routing algorithm was calibrated using the water and the sediment hydrographs observed at the watershed outlet during the first rainfall event. Assuming realistic estimations of flow velocity in hillslopes, a threshold of 0.062 m s−1 for linear erosion estimated over 10-m cells was defined. This threshold, validated using the remaining rainfall event, accurately predicted the length (mean error of estimate of less than 15%) and location of LE features. Using this simulation tool, an increase of the percentage of land under cultivation from 9% to 100% resulted in 600% increase in linear erosion. The tested scenarios of climate changes had less impact on linear erosion. [Copyright &y& Elsevier]

Abstract: The isolated Easter Island (Rapa Nui) is an outstanding example of land degradation caused by land use in a sensitive ecosystem. The focus of the investigation was placed on Poike peninsula, the most eastern part of Rapa Nui. While Poike peninsula was once supplied with fertile soils, in large areas desertification takes place today. Detailed analysis of soil profiles allowed the reconstruction of the history and of causes and effects of soil erosion and gullying in the context of land use history and cultural evolution. The results of the stratigraphic analysis prove that from the beginning of human settlement around AD 300/600 until AD 1280 the agriculture on Poike peninsula was characterised by sustainable land use and a traditional type of agro-forestry. Soil erosion was not significant. At around AD 1280 the woodland on Poike, dominated by the endemic palm Jubaea sp., was cleared by slashing and burning. Intensive farming on the upper slopes of the volcanic peninsula resulted in sheet erosion lasting until the 20th century. Settlements and ceremonial places which were built around AD 1300 on downslope areas were buried soon by sediments. Agriculture ceased around AD 1400 on downslope areas as the fertile soils were completely eroded. From AD 1400 until the late 19th century sheet erosion and the accumulation of fine-layered sediments migrated upslope. On average 8.6 Mg of soil per hectare and per year were reworked by erosion (eroded and accumulated within the catchment). Gullying began on Rapa Nui with the sudden increase in the number of sheep during the early 20th century. Gullies are still developing on the island and their ongoing enlargement created extended badlands on Poike which pose a significant problem for ecological and archaeological conservation strategies. Gullying rates exceed 190 Mg ha−1 y−1. [Copyright &y& Elsevier]

Abstract: Analysis of contemporary and past gully erosion and infilling processes allowed to reconstruct the long-term evolution of a permanent gully system under cropland. An active and a buried gully under cropland were investigated. The recent sediment deposits within the active gully, adjacent to the buried gully, showed that the recent gully was filling in at a mean rate of 6.4 cm a−1. In the buried gully, several erosion and deposition phases could be identified and the type of deposited sediments revealed a complex infilling history. Charcoal, pottery and brick fragments of different sizes were found at all depths of the gully infilling. Their age indicates that the first gully incised after the midst of the 17th century, most probably in the second half of the 18th century or the early 19th century. Gully morphology and analogy with the processes in the recent gully indicate that the buried gully filled in rapidly. Overall, five cycles of cut and fill occurred in 350 years or less and four cycles even within little less than a few decades, indicating that gully development and infilling under cropland can be very rapid processes. [Copyright &y& Elsevier]

Abstract: Measuring soil loss is costly, must cover a range of field situations, is not standardized, and is season dependent. In addition, use of sparse soil loss data (from other studies) compromises the integrity of many erosion models. Easily assessable soil erosion indicators to monitor the cumulative effect of erosion between tillage/weeding and harvesting called eroding clods, flow surfaces, pre-rills, and rills were surveyed directly after the 1995 rainy season in the Taita Taveta district of Kenya, to assessed the utility of each indicator. Their incidences were modeled using CPA. In the area, 70 maize plots in 11 map units, having considerable variation in altitude, land cover, rainfall, and geomorphology, were surveyed. Soil loss was considered variable between plots due to differences in surface soil, land cover, infrastructure (trash lines, grass strips, and Fanya-juu), crop management, slope, and map unit. The eroding clods indicator proved of little significance because the initial clods cover was unknown; the indicator probably relates better to soil erodibility then to soil loss. Flow surfaces, formed during erosive showers, were less present on fields with a higher ground and canopy cover, if the area of eroding clods was high, and if the topsoil had no loam which reduces chances of sealing; no impact of infrastructure, tillage, and weeding were detected. Fewer pre-rills were present where the fraction of groundcover was high, where Pigeon Peas were not grown (they cause micro-relief and concentrated flows), where weeding ended late (time effect), where more flow surfaces occurred, where Fanya-juu was constructed (less steep slopes), where the top-soil contained little sand (less sediment entrainment), and where maize was intercropped with vegetables (positive canopy cover effects). The model was not map unit specific and had an Adjusted R2 of 67%. The log-linear relationship indicates that combined positive conditions exponentially reduce the occurrence of pre-rills. The “pre-rill” indicator related best to management-affected site conditions and seems to reflect best the cumulative effects of soil loss over time. Rills were found at 18 sites located in drier areas on sandy–clay soils. The model suggested more rills if the topsoil contains no silt; this makes the soil susceptible to compaction, peptisation when wet, and rill formation. [Copyright &y& Elsevier]

The clayey Ultisols in low hilly area in southeastern China were called for agricultural reclamation to meet the increasing food demand. However, little attention was given to soil erosion during land use planning due to lack of information on the amount of soil erosion and how to restore the severely eroded bare soils. The objectives were to estimate the long-term influences of reforestation on soil and water erosion and nutrient losses on a severely eroded bare land derived from Quaternary red clay. The results indicated that reforestation using integrative measures decreased surface runoff and soil erosion on the severely eroded land. On the severely eroded bare land, annual runoff varied from 303 to 1056 mm and annual total soil loss from 53 to 256 tons ha−1. After reforestation, soil erosion dramatically reduced to 2–43 tons ha−1 year−1 from 1988 to 1990 and became negligible since then. The high level of soil erosion was attributed to high rainfall erosivity, readily transportable particles due to the presence of pseudo sand on the bared soil surface formed in the dry season and due to clay dispersion occurring in the long rainy season, and the gully landform. Depositional soil loss accounted for the high proportion of soil loss, while enrichment ratios (ER) of soil nutrients in the suspensional sediment were greater than 1. The results suggest that soil erosion has to be taken into account when planning to convert the clayey soils in the low hilly area for agricultural use, and integrative measures to reforest are key to prevent soil erosion on the severely eroded bared land. [Copyright &y& Elsevier]

Over the past years the Caesium-137 (137Cs) technique has been successfully applied in numerous environments all over the world. This technique is using the worldwide distribution of the anthropogenic 137Cs radionuclide and its redistribution associated with soil particles as an effective estimation of net soil-loss rates. In contrast to numerous studies on deep, often cultivated, clay soils with gentle to intermediate slopes, typical Mediterranean shallow stony soils on steep slopes have received less attention. In this paper, the landscape evolution over the past 37 years has been evaluated using the 137Cs technique for two lithological different areas under contrasting land use in the A´lora case study area (Ma´laga, Spain). In soils on gneiss and serpentinite bedrock several transects have been selected on steep slopes up to 35° with mean soil depths from 37 cm for gneiss to 24 cm for serpentinite. Estimating net soil redistribution rates from radionuclide distributions depends on the calculation of the local area reference inventory and the used calibration technique. Several methods have been tested and final results were found to differ considerably. After careful parameter selection, the resulting net soil redistribution estimates for the different transects have been compared with simulations of a simple landscape evolution model, resulting in different possible scenarios of erosional response. Total net soil-loss for the study area range from 2.3±0.25 to 69.1±7.8 t ha−1 year−1 for serpentinite and gneiss slopes, respectively. Differences in total slope sediment budgets as well as differences along the transects reveal influences of landscape representation and land use. In this case the impact of soil translocation by tillage and resulting erosion rates are far more important than possible parent material induced differences. However, comparing the two sampled areas not only net rates but spatial patterns as well reveal important differences in distribution over the landscape of net erosion and net sedimentation zones. [Copyright &y& Elsevier]

The islands of Azores are of very recent volcanic origin and their soils have special physical and chemical characteristics because of the specific circumstances of their formation from the volcanic materials, their young age and the presence of allophane. To assess and understand the hydrologic behavior of these soils under agricultural practices, the deterministic model OPUS was tested and calibrated using field data collected from 1996 to 1998 in two small basins of Terceira Island. The model uses a solution of the Richards'' equation to simulate water movement in the soil profile, which requires modified Brooks and Corey equations to describe the soil hydraulic characteristics. For runoff, the model uses either a mechanistic simulation with the Parlange and Smith infiltration equation or the Soil Conservation Service (SCS) Curve Number (CN) approach. In the first, a mechanistic detachment and transport model is used to simulate erosion, and for the second the modified universal soil loss equation (MUSLE) is utilized. Results of the model simulations for runoff and erosion match the observed data well. Runoff significantly increased from 1% to 17% of rainfall from pasture to bare soil or partially covered soil during establishment of a new pasture. Sediment yields sharply increased from <5 kg ha−1 year−1 under pasture to nearly 15 ton ha−1 during the 8-month period when the soil was unprotected. [Copyright &y& Elsevier]

Several land use scenarios were developed for the 3.5 km2 Danangou catchment on the Chinese Loess Plateau. These scenarios consist of four groups of three scenarios each: one group is based on the present land use distribution, the other three (alternative land uses) on a redistribution of land use according to slope gradient, soil type, slope aspect and land form. For example, cropland areas are restricted to slope gradients smaller than 25%, 20% and 15%. All groups consist of one scenario that only uses present or alternative land use and two scenarios that apply simple forms of biological conservation practices (mulching, improved fallow) and mechanical conservation practices (contour ridges). The LISEM soil erosion model was used to simulate the effects of these different scenarios on erosion. To do this, a calibrated LISEM-data set for a real storm was used. The results show that the predicted erosion rates for woodland/shrubland are much lower than those for other land uses. According to the simulations, runoff and erosion decrease by about 10% if conservation measures are applied to the present land use, while the predicted decrease for the alternative land uses is much larger at between 40% and 60%. This large decrease can be explained by the fact that one of the main differences in the alternative land uses is that they have much more woodland/shrubland. Differences in predicted erosion rates between the different alternative land uses are caused by conversion of cropland to orchard/cash tree. The present study is one of the first attempts to use soil erosion modelling as a tool for optimising land use and management strategies to reduce runoff and erosion rates on the Chinese Loess Plateau. More research will be needed to validate obtained simulation results with actual field measurements. [Copyright &y& Elsevier]

The Wolfsgraben is one of many ravines that cut into the silty–sandy material of the Triassic benchlands of northern Bavaria, Germany. Within the research area, a gully—several meters in depth—has carved in to a bluff 500 m west of the upper Main valley. An analysis of 17 exposures and 30 drillings was conducted within the gully and its colluvial fan in order to reconstruct the soil formation, extreme rainfall events and land use changes throughout history.Detailed field studies, chemical soil analysis, dating methods of charcoal and pottery, as well as written documents were combined to produce a high-resolution stratigraphy.Nine main phases of landscape evolution, caused by extreme rainfall, runoff and soil erosion in agriculturally used areas, have been identified since the medieval period. The highest amount of soil loss occurred during 14th, 18th and 19th centuries, a result of intensive land use. Climate changes affected the intensity of rainfall and the magnitude of soil loss during these periods. [Copyright &y& Elsevier]

• Multiple tracers were employed to identify the sources of eroded OM in sediments. • Gully banks were the main contributing sources to eroded bulk OM at multiple scales. • Sediment bulk OM mainly sourced from the region with light erosion intensity. • Biological production of OM impacted on the dynamics of water-extractable OM. Erosion is a fundamental phenomenon that governs the biogeochemical cycle of carbon (C) in the Earth system. Understanding the fate of eroded C at the watershed scale thus provides essential guidance for balancing the C budget and evaluating soil management strategies. In this study, we collected a total of 229 topsoils of source materials [land use types (forests, grassland, cropland, orchard, and fallow) and gully bank] and a total of 56 surface sediment samples [main river channel (18) and three tributaries (38) with different erosion intensity]. Multiple tracers (C and nitrogen (N) isotopes, molecular n-alkane biomarker, and spectroscopic indices) applied widely were then analyzed to determine relative source contributions to eroded organic matter (OM) (including bulk OM and water-extractable OM) in sediments at a broader watershed on the Loess Plateau of China. The results from an isotopic mixing model analysis showed that gully bank was the primary contributor of bulk OM in sediments, accounting for mean probability estimate (MPE) 55.3%, followed by "grassland" (MPE 21.0%), "cropland" (MPE 14.4%), and "forests" (MPE 9.3%). The contributions of grassland and cropland showed an increasing trend from upstream to downstream sections of the studied watershed. The contribution of forests was found higher in upstream than those of midstream and downstream. Along with previous evidences, our results show that erosion intensity mainly affects the proportion of C source, where gully bank was found as the highest contributor in three associated catchments, especially in region with light erosion intensity. We further demonstrated that the sediment bulk OM deposited was mainly derived from the region with light erosion intensity at the broader watershed scale. Moreover, results of n-alkane ratios and spectroscopic indices also implied that biological production of OM other than terrestrial sources (i.e., soil OM) might play a critical role in source contribution of water-extractable OM in sediments of main river channel. [ABSTRACT FROM AUTHOR]

Fallout radionuclides, such as Caesium-137, were proven to be a valuable means for studying medium-term (c.a. 50 years) soil erosion processes. In order to gain knowledge on the spatial distribution of 137Cs in volcanic soils of Andean Patagonia, 137Cs reference inventories were established along a precipitation gradient. At the subhumid sector, patterns of 137Cs gain/loss associated with land use were also determined considering native forests under grazing, a degraded rangeland and a pine plantation. Along the rising rainfall gradient (750–1400 mm), pedogenesis of volcanic ash soils, non-crystalline mineral formation, organic matter content and soil porosity varied, increasing in moister areas. Radionuclide inventories varied along the edaphoclimatic gradient, reaching mean values of 192, 267 and 576 Bq m−2, at study areas with 750, 950 and 1400 mm of annual precipitation, respectively. The 137Cs inventory followed an exponential relationship with precipitation, which could be related to the presence of allophane as the colloidal material in the soils from the rainiest area. The penetration depth reached by 137Cs varied between 15 and 25 cm, according to rain amount and soil texture. Most of the 137Cs fallout was retained in the uppermost 10 cm of the profiles and an exponential decline of 137Cs with depth, highly related to organic matter contents, was found. At the subhumid study area, both 137Cs mass activity and inventory, significantly decreased under the different land uses, with respect to reference soils. Although the pattern of 137Cs gain/loss varied according to topography, soil properties (organic matter and porosity) and vegetation cover, showing eroding and aggrading profiles, most samples had 137Cs values lower than the reference value, suggesting loss of soil as a consequence of erosion processes. Furthermore, as much as 45%, 58% and 70% of sample points from native forests, plantation and rangeland, respectively, had 137Cs values below the limit of detection. In the study transects, the loss of the upper 15 cm of soil in the subhumid sector during the last 50 years, highly exceeding tolerable erosion rates, highlights the urgent need for applying effective soil conservation measures. Reference inventories, which vary according to the edaphoclimatic gradient, and the loss of the radionuclide in sites with anthropic intervention, show the potential for using 137Cs measurements for assessing erosion processes in the Patagonian Andean Region. • 137Cs inventory in Patagonia depends on precipitation and non-crystalline clays • 137Cs is mainly retained in the uppermost 10 cm of the soil profiles. • 137Cs along soil profiles is controlled by organic matter. • High 137Cs loss and erosion rates under different land uses in forest/steppe ecotone • 137Cs allows to assess erosion rates in Patagonian Andean Region. [ABSTRACT FROM AUTHOR]