A quantification of the effects of erosion on the productivity of purple soils

Research on the effects of soil erosion on soil productivity has attracted increasing attention.Purple soil is one of the main soil types in China and plays an important role in the national economy.However,the relationship between erosion and the productivity of purple soils has not been well studied.The purpose of this research was to determine if soil depth,which is dependent on the rate of erosion,has an influence on crop yield and growth.Plot and pot experiments at different soil depths were performed.Results indicate that soils from different parental materials had different growth features and crop yields due to the differential fertility of the derived soils.The yield reduction rate increases exponentially with the depth of eroded soil(level of erosion).The yield reduction rate per unit eroded soil horizon(10 cm) is approximately 10.5% for maize and wheat.     

土壤有机质含量估测及其影响因素的光谱分析

 土壤颗粒大小差异使土壤反射光谱产生相应变化,影响土壤有机质含量等属性的光谱预测精度。本研究准备了颗粒粒径分别为2、0.25和0.15mm的土样,测定土壤有机质(Soil Organic Matter,SOM)含量,并于室内模拟条件下测定其反射光谱。通过分析不同粒径土样的原始(Raw)、多次散射校正(Multiple scattering correction, Msc)、一阶微分(First derivative, Fd)、连续统去除(Continuum removal, Cr)光谱与SOM含量之间的关系,筛选出与SOM含量相关性最强的Fd光谱单波段(2250nm, r=0.82, P<0.01),并建立线性回归模型;利用全波段光谱反射率,以偏最小二乘回归(Partial least square regression, PLSR)方法,确立2mm土样Msc处理光谱的PLSR模型为最优模型(RPD=3.56、R²=0.90、RMSEP=1.96g/kg)。土壤颗粒粒径对土壤光谱反射率变化有明显影响,但二者之间并非简单的线性关系,可能存在一个转折点;单变量(单波段光谱反射率)线性回归模型的预测能力,明显低于全波段反射光谱(Msc处理)-PLSR模型;土样样本容量对SOM含量预测精度有显著影响。因此,根据样本容量大小,选择合适的土壤颗粒粒径与光谱预处理方法组合可以提高预测精度。     

Combining Environmental Factors and Lab VNIR Spectral Data to Predict SOM by Geospatial Techniques

Soil organic matter(SOM) is an important parameter related to soil nutrient and miscellaneous ecosystem services. This paper attempts to improve the performance of traditional partial least square regression(PLSR) model by considering the spatial autocorrelation and soil forming factors. Surface soil samples(n = 180) were collected from Honghu City located in the middle of Jianghan Plain, China. The visible and near infrared(VNIR) spectra and six environmental factors(elevation, land use types, roughness, relief amplitude, enhanced vegetation index, and land surface water index) were used as the auxiliary variables to construct the multiple linear regression(MLR), PLSR and geographically weighted regression(GWR) models. Results showed that: 1) the VNIR spectra can increase about 39.62% prediction accuracy than the environmental factors in predicting SOM; 2) the comprehensive variables of VNIR spectra and the environmental factors can improve about 5.78% and 44.90% relative to soil spectral models and soil environmental models, respectively; 3) the spatial model(GWR) can improve about 3.28% accuracy than MLR and PLSR. Our results suggest that the combination of spectral reflectance and the environmental variables can be used as the suitable auxiliary variables in predicting SOM, and GWR is a promising model for predicting soil properties.     

Effects of gully erosion and gully filling on soil degradation in the black soil region of Northeast China

Gully erosion has caused soil degradation and even reduced soil productivity.However,only few studies on the effects of gully erosion and artificial controlling measures on soil degradation in the Black Soil Region of Northeast China are available.Thus,this study explores the relationships between gully erosion,gully filling and soil parameters.Two sets of soil samples were collected in the field at:(1) 72 sample points in the gully erosion study area,60 sample points in the ephemeral and classical gully erosion area(3,518 m2),12 sample points in the deposition zone(443 m2),(2)10 reference points along a slope unaffected by gully erosion representing the original situation before the gully was formed.All soil samples were analyzed for gravel content(GC),soil organic matter(SOM),total nitrogen(TN),available nitrogen(AN),available phosphorus(AP),and available potassium(AK).The soil property values on unaffected slope were fitted by the polynomial curves as the reference values in no gully erosion area.The interpolated soil property values in gully eroded study area were compared with these polynomial curves,respectively,and then,changes of soil property values were analyzed.Gully erosion caused an increase in GC and a decrease in SOM,TN,AN,AP and AK.The change of GC,SOM,TN,AN,AP,AK was 8.8%,-9.04 g kg-1,-0.92 g kg-1,-62.28 mg kg-1,-29.61 mg kg-1,-79.68 mg kg-1.The soil property values in the study area were below optimal values.Thus,we concluded that gully erosion and gully filling caused both on-site and off-site soil degradation.Soil degradation area was 0.65 % of the cultivated land.In addition,it was proved that gully filling were an improper soil and water conservation measure,which seems to exacerbate the problem.Thus,it is suggested that soil where soil is deep is moved to fill the gully,and then the area around the filled gullies should be covered by grass for preventing the formation and development of the gully.     

Enzyme-Induced Carbonate Precipitation for the Protection of Earthen Dikes and Embankments Under Surface Runoff: Laboratory Investigations

Earthen structures such as shore protection dikes and river embankments easily suffer from erosion under surface water runoff.This study made experimental efforts to explore the enzyme-induced carbonate precipitation(EICP)method for slope erosion control under surface runoff for earthen structures.The sandy soils were treated by the EICP method for various rounds.Surface characteristics were evaluated by the surface penetration resistance,calcium carbonate content,and surface hard crust thickness of EICP-treated soils.Slope runoff erosion experiments were carried out to evaluate the erosion control performances of the EICP treatment.The surface penetration resistance,calcium carbonate content,and surface hard crust thickness were found to significantly increase with the treatment rounds.In the erosion experiments,it was observed that the level of damages decreased and the water flow volume required to trigger the damage increased with more treatments.The increase in the soil slope angle led to more serious surface damages.The amount and rate that the soil particles were eroded from the slope surfaces declined with more EICP treatments,which was consistent with those of visual observations.The preliminary investigations presented in this study have shown the potential of the EICP method for slope erosion control under surface runoff for earthen structures.     

基于光谱吸收特征分析的彩绘文物颜料识别研究

高光谱成像技术作为一种无损高效的检测方法,对于彩绘文物颜料的鉴别具有重要意义。由于全波段参与光谱相似度计算会造成数据的冗余,没有充分利用光谱的细微特征。为此,本文首先对文物颜料光谱吸收特征进行参量化分析,并通过改进的光谱吸收特征拟合算法与标准光谱进行匹配识别,从而得到识别结果。实验以获取的一幅波长为400~1000nm的古代壁画高光谱影像为例,通过光谱吸收特征分析识别出壁画的颜料主要成分有朱砂、赭粉、石绿和石青,4种颜料的光谱吸收特征拟合度分别是:0.95、0.77、0.92、0.81。实验结果表明:对光谱吸收特征分析可以帮助识别彩绘文物的颜料信息,该方法可为以后文物修复提供参考。     

Wind tunnel study of multiple factors affecting wind erosion from cropland in agro-pastoral area of Inner Mongolia, China

In this paper,the process of wind erosion on two kinds of soil from the agro-pastoral area of Inner Mongolia are studied using wind tunnel experiments,considering the wind speed,blown angle of wind and soil moisture content.The results showed that the modulus of soil wind erosion increases with an increase of wind speed.When the wind speed exceeds a critical value,the soil wind erosion suddenly increases.The critical speed for both kinds of soil is within the range of 7-8m·s-1.For a constant wind speed,the rate of soil wind erosion changes from increasing to falling at a critical soil slope.The critical slope of loam soil and sandy loam soil is 20° and 10°,respectively.Soil moisture content has a significant effect on wind erosion.Soil wind erosion of both soils decreases with an increase of the soil water content in two treatments,however,for treatment two,the increasing trends of wind erosion for two soils with the falling of soil water content are no significant,especially for the loam soil,and in the same soil water content,the wind erosion of two soils in treatment one is significantly higher than treatment two,this indicates reducing the disturbance of soil surface can evidently control the soil wind erosion.     

兴国县土壤侵蚀变化的遥感监测与分析

兴国县是南方红壤丘陵区水土流失最严重的地区之一,近20年的综合治理成效显著。为分析该时期县域内水土流失的变化趋势,并掌握其目前的水土流失状况,本文选用1987、1994和2000年的TM影像,采用基于NDVI 的动态监测和影像分类相结合的方法.对江西兴国县近20年水土流失的情况进行分析,定性与定量地反映兴国县水土流失的时空变化趋势,并结合地形因素进行交叉分析,获取水土流失的空间分布规律。兴国县水土流失变化分析结果表明:在水土流失面积方面,这3年中均呈减少趋势;在空间分布上,中南部和东部部分地区流失强度下降幅度较大,强度明显加剧的区域较少,除西南部的部分地区外,仅在县境边缘有零星分布。目前,水土流失主要分布在海拔500m以下和坡度20°以下的地区。     

Carbonates and organic matter in soils characterized by reflected energy from 350-25000 nm wavelength

The soil carbon pool which is the sum of soil organic carbon(SOC) and soil inorganic carbon(SIC) is the second largest active store of carbon after the oceans and it is an important component of the global carbon cycle. Hence, accurate estimation of SOC and SIC as important carbon reservoirs in terrestrial ecosystems using fast, inexpensive and non-destructive methods is crucial for planning different climate change policies. The aim of the current research was to examine the effectiveness of Vis-NIR(visible and near-infrared spectroscopy: 350-2500 nm) and MIR(mid-infrared spectroscopy: 4000-400 cm~(-1)) to characterize and estimate soil organic matter(SOM) and carbonates as main components of soil carbon stocks in Juneqan, Charmahal va Bakhtiari, Iran. To do so, a total of 548 soil samples from this area were collected(October 2015) and analyzed in laboratory(August 2017). In order to develop models capable of predicting SOM and carbonates content, seven spectral preprocessing methods comprising Absorbance(Abs), De-trending(Det), Continuum removal(CR), Savitzky-Golay derivatives(SGD), standard normal variate transformation(SNV), multiplicative scatter correction(MSC) and Normalization by range(NBR) were conducted along with five multivariate methods including Random Forest(RF), Partial Least-Squares Regression(PLSR), Artificial Neural Network(ANN), Support Vector Machine(SVM) and Gaussian Process Regression(GPR). The content of carbonates caused spectral reflectance intensity to augment on several ranges of spectrum and strong absorption feature at 2338 nm in the Vis-NIR and 714, 850, 870, 1796, 2150 and 2510 cm~(-1) in the MIR spectra range. SOM absorbed energy in several ranges, but also showed specific peaks in MIR. Both facts are associated with the structure of carbonates and SOM and its interaction with energy. The best combination of preprocessing and calibration models for carbonates quantification in Vis-NIR spectra was Det/PLSR(R~2= 0.74, RPD= 2.19, RMSE= 6.45). For SOM, it was Det/PLSR(R~2= 0.82, RPD= 2.41, RMSE= 0.75). The Det/RF(R~2= 0.87, RPD= 2.44, RMSE= 0.66) for the quantification of SOM and MSC/RF(R~2= 0.84, RPD= 2.84, RMSE= 5.50) for carbonates in MIR spectra range showed the greatest results. The stronger occurrence of spectral bands in MIR as well as the specificity of the absorption features indicated that this range produced better predictions. The obtained results highlighted the significant role of soil spectroscopy technique in predicting SOC and soil carbonates as key components of soil carbon stocks in the study area. Therefore, this technique can be used as a more cost-effective, time saving and nondestructive alternative to traditional methods of soil analysis.     

Effects of environmental factors on classification of loessderived soils and clay minerals variations,northern Iran

Land-use type under different topographic conditions and human activities affects soil development. We investigated the effects of land-use, topography and human activity on soil classification changes in the Toshan watershed in northern Iran. Seven representative pedons derived from loess parent materials were studied on different land-uses and topographic positions. The studied pedons in forest (FO) on backslopes and footslope were classified as Calcic Haploxeralfs and Typic Haploxeralfs, respectively. The soils in abandoned lands (AB) and orchards (OR), where formerly under natural forests, located on the shoulder and backslopes positions were classified as Calcic Haploxeralfs and Vertic Haploxeralfs, respectively. Well-developed argillic horizons as indicators for higher degrees of soil evolution were observed in more-stable areas under the natural forest or less disturbed areas. Clay lessivage through these soil profiles have led to formation of Typic or Calcic Haploxeralfs, while under croplands (CP) were classified as Typic Calcixerepts. Conversion of sloping deforested areas to CP along with inappropriate management have accelerated soil erosion, resulting in unstable conditions in which decalcification and formation of developed soils cannot occur. Paddy cultivation in flat areas has caused to reduced conditions and formation of Typic Haplaquepts. Because of unfavorable conditions for chemical weathering (e.g. lower water retention compared to more-stable areas) no vermiculite was detected in the CP. The results showed that evolution and classification of the studied soils were strongly affected by land-use type, topography and management.     

草地退化杂类草入侵遥感监测方法研究进展

近年来,受全球气候变暖及日趋频繁的人类活动的共同影响,我国草地生态系统出现了不同程度的退化,成为草地生态学界的研究热点。本文较系统总结了草地退化、杂类草入侵遥感监测方法的应用进展,指出了常规草地退化遥感监测方法的不足,并展望了今后的发展方向。研究发现草地退化在群落尺度上往往表现为优质牧草种类减少,杂类草种类增加。在草地退化过程中,杂类草侵入,往往导致植被覆盖度增加,因而传统的基于植被覆盖度、生产力和产草量下降的草地退化遥感监测方法,无法反映草地退化在植被种群方面的变化特征,尤其是杂类草入侵的草地退化过程。而目前基于高光谱数据的草地退化杂类草入侵监测方法,结合地面光谱测定和对退化草地物种特征微弱光谱差异的定量分析,能有效识别群落中杂类草种类,并反演出占群落的面积比例、高度和盖度等,可为草地退化监测及其治理提供群落演替过程及其态势的重要指标,为草地退化监测提供新的遥感技术方法。     

南方红壤侵蚀区长汀县不同生态恢复年限下芒萁叶绿素含量的高光谱估算模型

芒萁是南方红壤侵蚀区生态恢复重要的地带性草本植物,对生态系统修复具有重要作用,监测其叶绿素含量能有效诊断生长健康状况。本文以福建省长汀县朱溪流域6个不同生态恢复年限下的芒萁叶片高光谱反射数据以及实测叶绿素含量为数据源,借助高光谱遥感技术分析不同恢复年限芒萁叶片原始光谱特征,筛选出光谱敏感波段并构建光谱指数,基于相关性分析,建立芒萁叶绿素单变量以及多元逐步回归模型,并确定最佳估算模型。结果表明：高光谱指数建立的单变量估算模型中,改进红边归一化植被指数（mNDVI₇₀₅）、叶面叶绿素指数（LCI）、红边指数（Vog）、比值光谱指数（RVI_603/407）、NDVI[603,407]高光谱指数建立的二次模型精度高,建模决定系数R²均超过了0.8,其中以高光谱指数为自变量建立的多元回归模型拟合R²值（0.886）最高。综合建模精度和模型验证精度,LCI指数构建的单变量模型以及基于高光谱指数的多元回归模型是估算芒萁叶片叶绿素含量最佳模型。本研究建立的叶绿素高光谱估算模型对快速、无损地监测水保植物芒萁生长具有重要意义。     

Soil and Vegetation Spectral Coupling Difference (SVSCD) for Minerals Extraction from Hyperion Data in Vegetation Covered Area

Remote sensing data have been widely applied to extract minerals in geologic exploration, however, in areas covered by vegetation, extracted mineral information has mostly been small targets bearing little information. In this paper, we present a new method for mineral extraction aimed at solving the difficulty of mineral identification in vegetation covered areas. The method selected six sets of spectral difference coupling between soil and plant (SVSCD). These sets have the same vegetation spectra reflectance and a maximum different reflectance of soil and mineral spectra from Hyperion image based on spectral reflectance characteristics of measured spectra. The central wavelengths of the six, selected band pairs were 2314 and 701 nm, 1699 and 721 nm, 1336 and 742 nm, 2203 and 681 nm, 2183 and 671 nm, and 2072 and 548 nm. Each data set’s reflectance was used to calculate the difference value. After band difference calculation, vegetation information was suppressed and mineral abnormal information was enhanced compared to the scatter plot of original band. Six spectral difference couplings, after vegetation inhibition, were arranged in a new data set that requires two components that have the largest eigenvalue difference from principal component analysis (PCA). The spatial geometric structure features of PC1 and PC2 was used to identify altered minerals by spectral feature fitting (SFF). The collecting rocks from the 10 points that were selected in the concentration of mineral extraction were analyzed under a high-resolution microscope to identify metal minerals and nonmetallic minerals. Results indicated that the extracted minerals were well matched with the verified samples, especially with the sample 2, 4, 5 and 8. It demonstrated that the method can effectively detect altered minerals in vegetation covered area in Hyperion image.     

Effects of plant types on physico-chemical properties of reclaimed mining soil in Inner Mongolia,China

A field experiment was conducted in Jungar Banner, Inner Mongolia, China to study the effects of plant types on the physical structure and chemical properties of open-cast mining soils reclaimed for 15 years, and to analyze the triggering factors of the soil formation. Results indicate that plant types affect soil-forming process especially in the upper layer (0–20 cm), and the spatial structure of reclaimed plant is the main reason for variability of the soil-forming process. In the upper soil layer at the site reclaimed with mixed plants, the concentrations of soil organic matter (SOM) and soil organic carbon (SOC) are the highest, and they were significantly higher at the sites reclaimed with Leymus chinensis, Caragana sinica, which is mainly due to a large amount of litter fall and root exudation in herbages and shrubs. However, the concentrations of SOM and SOC in the soils at the reclaimed sites are quite low comparing with those in local primary soil, which indicates the importance of using organic amendments during the ecological restoration in the study area.     

Large-area Analysis of Soil Erosion and Landslides Induced by Rainfall: A Case of Unsaturated Shallow Deposits

Unsaturated shallow soil deposits may be affected by either superficial soil erosion or shallow landslides in adjacent or overlapping source areas and in different seasons when a different soil suction exists.The triggering analysis of both these processes is a relevant issue for the hazard analysis while the literature mostly provides specific approaches for erosion or for landslides.The paper proposes a largearea analysis for a case study of Southern Italy,consisting of unsaturated shallow deposits of loose pyroclastic(air-fall) volcanic soils that have been repeatedly affected by erosion and landslides in special seasons.For a past catastrophic event, the simulated source areas of shallow landslides are smaller than those observed in the field while the simulated eroded areas with thickness greater than 5cm are comparable with the in-situ evidences, if the analysis takes into account high rainfall intensity and a spatially variable soil cover use.More in general, the results of the paper are consistent with the previous literature and also provide a methodological contribution about the application of distinct tools over large area.The added value is that the paper shows how the combination of distinct large-area analyses may help with understanding the dominant slope instability mechanisms.Only once this goal is fully achieved, can specific physically-based analyses be confidently performed at detailed scales and for smaller specific areas.     

A soil quality index for evaluation of degradation under land use and soil erosion categories in a small mountainous catchment,Iran

Soil erosion and land use type have long been viewed as being particularly important drivers of soil degradation. The objectives of this study,therefore, were to select a new soil quality index(SQI)which varies significantly with land use/soil erosion,and to evaluate the new SQI using expert opinion. In total, 18 soil physical, chemical, and biochemical properties(indicators) were measured on 56 soil samples collected from four land use/soil erosion categories(rangeland/surface erosion, rangeland/subsurface erosion, cultivated land/surface erosion and dry-farming land/surface erosion). Principal component and classification analysis(PCCA)identified five PCs that explained 77.7% of the variation in soil properties with the biochemical PC varying significantly with land use/soil erosion.General discriminant analysis(GDA) selected urease and clay as the most sensitive properties distinguishing the land use/soil erosion categories.The GDA canonical scores for the new SQI were significantly correlated with expert opinion soil surface summed scores(for soil movement, surface litter, pedestalling, rills and flow pattern) derivedusing the U.S. Department of the Interior Bureau of Land Management(BLM) method. A forward stepwise general regression model revealed that the new SQI values were explained by soil movement,surface litter, and the summed values of the soil surface factors. Overall, this study confirmed that soil quality in the study area in Iran is controlled by land use and corresponding soil erosion.     

土壤粒径的光谱响应特性研究

以实验室制备的5个不同粒径水平的土壤样本和室内高光谱数据为基础,通过对光谱数据进行重采样、数学变换等预处理并进行单因素方差分析、相关性分析和回归分析,探讨土壤粒径的高光谱特性,建立了光谱数据预测土壤粒径的校正模型。结果表明,土壤粒径对反射光谱有显著的影响,波长越长影响越大;在全波段范围内土壤粒径和光谱数据都呈负相关关系,对原始光谱数据进行微分变换能增加其与土壤粒径的相关性;以反射率一阶微分建立的回归模型为反演土壤粒径的最佳模型,其建模决定系数■、预测决定系数■、预测相对偏差RPD分别为0.666,0.653,2.043,预测均方根误差RMSE为0.175。     

Indexing the engineering properties of residual soils in the southern slopes of Mashhad,NE Iran

Residual soils are weathering products of rocks that are commonly found under unsaturated conditions. The properties of residual soils are a function of the degree of weathering. A series of index properties, engineering properties and geophysics survey examinations were performed on residual soils from two major geological formations in Iran. In the present research, the index properties of residual soils in the south of Mashhad city in Iran are investigated.Natural and artificial trenches were analyzed for evaluating the weathering profiles and collecting soil samples. Disturbed and undisturbed samples were obtained from each of the soil profile horizons resulting from weathering of different parent rocks.Subsequently, physical properties and mechanical properties of the soil samples were determined in accordance with ASTM standards. Also, the mineralogical composition, chemistry, and texture of the soil were evaluated in 51 profiles. The field observations showed the difference in the weathering profile of residual soils deposited on various rocks(igneous, sedimentary, and metamorphic). These profiles mainly consisted of two horizons includingresidual soil on top and saprolite at the bottom. The results of laboratory tests and geotechnical data showed that the properties of residual soil samples change by depth. Moreover, depending on the type of origin rock, the properties are different in various types of residual soils. In most of the samples, the moisture content of soil horizons was also increased by depth. Based on the unified soil classification(USCS), the soils of the upper horizons appeared to be classified as ML(Lean silt) and CL(Lean clay) while the soils of the lower horizons(saprolite zone) fall in SC(clayey sand), SM(silty sand), and SW(wellgraded sand) classes. Moreover, the results demonstrated that the particle size of the soil was increased by depth. Comparison of results of the geotechnical tests showed that properties of residual soils are changed by variations of depth, weathering level, and type of parent rock. Considering the concentration of the number of lines and the concentration of the points of intersection, the length and dimension fractal of lineaments in the southeastern part of the study area, it is evident that this zone possesses weathering severity and soil thickness. Fieldwork data from this zone have also verified the severity of weathering conditions. The analysis of lineaments trends in different parts of the study area indicated that the lineaments with the NW-SE trend have a strong effect on weathering development. The weathering depth depends on the orientation of bedding joints with respect to the slope in the study area. Slope inclination and soil thickness are controlled by weathering and erosion processes.     

SOIL EROSION AND ITS IMPACTS ON ENVIRONMENT IN YIXING TEA PLANTATION OF JIANGSU PROVINCE

Soil erosion on sloping field has led to a lot of environmental problems. In order to reveal the seriousnessof the damage of soil erosion on sloping fields 137^Cs tracer method was used to estimate soil erosion rate. 137^Cs referenceinventory of 2200Bq/m^2 in Yixing, southern Jiangsu Province, was estimated and a model for estimating erosion of cultivat-od soil was established in order to avoid overestimating soil erosion rates. Then based on the soil erosion rates and mea-sured soil physical and chemical properties, direct and indirect impacts of soil erosion on environment were further dis-cussed. Direct impacts of erosion on environment included on-site and off-site impacts. The on-site impacts were thatsoil layer became thin, soil structure was deteriorated and soil nutrients decreased. The off-site impacts were that waterbodies were polluted. The indirect impacts of soil erosion on environment were the increase of fertilizer application andenergy consumption, and change of adaptability of land uses. Although erosion intensity was not serious in the studyarea, its environmental impacts should not be ignored because of great soil nutrient loss and coazseness of soil particles.     

Organic carbon losses by eroded sediments from sloping vegetable fields in South China

Soil Organic Carbon(SOC) is the most important component of soil. Though small, it determines soil fertility and prevents soil losses. In this study, we examined relationships between the Particle–Size Distribution(PSD) of the eroded sediment and SOC loss, and evaluated the effects of plant coverage ratios(0%, 15%, 30%, 45%, 60% and 90%), slope lengths(2 m, 4 m), fertilizer treatments(unfertilized control(CK), compound N–P–K fertilizer(CF), and organic fertilizer(OF)) on SOC loss and the SOC enrichment ratio(ERSOC) in the eroded sediments. The experimental results showed that longer slope length and lower surface cover ratios produced larger surface runoff and the eroded sediments, resulting in larger SOC losses. The average SOC loss was greatest in the OF treatment and SOC loss was mainly associated with the eroded sediment. Surface runoff, which causes soil erosion, is a selective transportation process, hence there were more claysized particles(2 μm) and silt-sized particles(2-50 μm) in the eroded sediments than in the original soils. SOC was enriched in the eroded sediments relative to in the original soil when ERSOC 1. ERSOC was positively correlated with ER_(clay)(2 μm)(R~2 = 0.68) and ERfine silt(2–20 μm)(R~2 = 0.63), and from all thesize particle categories of the original soil or the eroded sediments, more than 95% of SOC was concentrated in small-sized particles(50 μm). The distribution of SOC in different-sized particles of the original soil and the eroded sediment is primarily associated with clay-sized particles and fine silt-sized particles, thus we conclude that as the eroded sediment particles became finer, more SOC was absorbed, resulting in more severe SOC loss.