【作者】 陈晓燕；

【导师】 魏朝富； 谢德体；

【作者基本信息】 西南大学 ， 农业资源利用， 2009， 博士

【摘要】 在全球范围内,70%的国家和地区都受到水土流失的危害,每年有250亿吨的肥沃表土流失。作为世界上水土流失最严重的国家之一,我国目前关于水土流失的研究远不能满足国家生态建设和经济迅速发展的需求。由于水土流失是具有明显尺度效应的过程,不同尺度下的水土流失既相互联系又相互区别。目前,在室内土槽、径流小区、坡面等单一尺度上对不同地区和不同土壤类型的水土流失进行了深入的研究,但针对径流小区、自然坡面、小流域三个不同尺度缺乏对比研究。同时,水土流失效应随研究区域面积的增加呈现非线性关系,区域甚至全球范围内水土流失机理的揭示必须首先解决不同尺度上影响水土流失因子对其效应的贡献率随研究区域增大的主次顺序易位问题,这些问题的解决最终需要回到小尺度上来解决。因此,阐明典型区域径流小区、自然坡面、小流域三个不同尺度下的水土流失效应和内在机理具有重要的理论和实践意义。紫色土是长江及其主要支流泥沙的主要来源。作为我国特有的一种土壤类型,紫色土质地松软,结构松散,易风化,抗蚀性较差,保水保土能力弱,是一种侵蚀型的高生产力岩性土。我国紫色土的侵蚀面积及强度仅次于北方的黄土。在三峡库区,人为活动加剧了土壤侵蚀过程,水土流失日趋严重,已影响到库区的生态安全和三峡水库的可持续利用。因此,本文以紫色土为研究对象,分别选择了重庆市万州区生态环境监测重点站内径流小区、紫色土自然坡面及戴家沟小流域为研究尺度单元,通过对土壤/泥沙颗粒和养分流失的分析研究,探讨径流小区、自然坡面、小流域三个不同尺度下水土流失效应及内在机理,以期揭示水土流失机理以及尺度效应,从而为紫色土水土流失的防治提供理论基础,也为下一步区域水土流失机理研究及预测预报模型构建、应用奠定了基础。1、径流小区尺度下紫色土水土流失效应。以万州典型区生态环境监测重点站内径流小区为研究单元,通过人工模拟降雨试验,对一定坡度不同坡位、不同雨强下紫色土径流小区中土壤颗粒变化和养分流失特征及其土壤颗粒—径流—养分耦合关系进行了分析研究。在降雨雨滴击溅和坡面径流的搬运、迁移以及冲刷作用下,径流小区上坡粘粒、粉粒含量降低,砂粒含量增多;中坡粘粒和砂粒含量增多,粉粒含量减少;下坡粘粒含量增多,砂粒和粉粒含量减少。随着雨强的增大,养分流失率在各坡面位置大体呈现增大的趋势。土壤颗粒在降雨前后的差异与土壤养分的流失存在不同程度的正相关关系。对比分析降雨前后坡面土壤团聚体含量变化,＜0.25 mm和＞2 mm团聚体含量在降雨后显著增加,其它粒径团聚体含量则有所下降。降雨前后土壤团粒分形维数差异越大,养分的流失率也越大。不同雨强下,侵蚀泥沙量都出现从升高到降低的一个过程,侵蚀泥沙峰值量随着雨强的增大而增大且出现时间也不断提前,其侵蚀泥沙养分峰值也有大致相同的趋势。但是由于不同养分对以泥沙为流失载体的吸附性不同,并非所有侵蚀泥沙养分含量都随着降雨强度的增大而增大。随着雨强的增大、产流时间的增加,径流养分累积量也相应增大。在相对较大雨强条件下径流流速与产流历时为幂函数关系,而在小雨强条件下流速与产流历时为二次曲线关系。径流养分与径流量之间的关系表现为,径流强度和径流流速与径流养分中总氮浓度和径流总磷浓度相关关系不明显,但是与相应的总氮、总磷流失量呈现明显的相关关系。因此,在径流小区尺度上,降雨对土壤颗粒组成的影响表现为上坡细颗粒的减少,粗颗粒的增多;下坡细颗粒的增多,粗颗粒的减少;对团聚体的影响表现为＜0.25 mm和＞2 mm团聚体含量增加;土壤养分流失率与土壤颗粒变化、团聚体稳定性变化存在相关关系:侵蚀泥沙量、侵蚀养分均随着雨强的增大、产流时间的增加而增加,但不同养分元素间存在着差异。2、自然坡面尺度下紫色土水土流失效应。以紫色土自然坡面为研究单元,利用¹³⁷Cs示踪技术测定自然坡面不同地貌部位、典型土地利用类型地块的土壤侵蚀模数,分析坡面侵蚀泥沙来源,探讨坡面不同地貌部位、不同土地利用类型的土壤侵蚀强度差异;以坡面径流出口测流堰自然降雨观测资料为基础,研究了坡面土壤颗粒、侵蚀泥沙颗粒变化特征,土壤养分、径流养分、侵蚀泥沙养分变化特征,土壤颗粒变化与侵蚀之间的关系,探讨土地利用类型、坡位等对坡面土壤侵蚀模数、土壤颗粒变化特征及养分流失特征的影响。坡面位置和土地利用对自然坡面土壤颗粒组成的空间分布具有重要影响。不同土地利用类型间土壤粘粒含量从大到小为荒草地＞林地（疏林地,桔林地,桃林地）＞农耕地;同一土地利用类型不同坡面位置土壤粘粒含量从小到大依次为上坡＜中坡＜下坡。侵蚀泥沙的变化过程表现为随着降雨产流历时的进行,其侵蚀泥沙中砂粒的变化特征分别呈现出先增大后减小的趋势,而粘粒含量则呈现出先减小后增大的变化特征,并且两种颗粒的变化趋势与产流历时都呈现出回归效果较好的二次曲线关系。自然坡面各土地利用类型下各养分元素在不同坡位上的平均含量都呈现出上坡位＜中坡位＜下坡位的特征。降雨侵蚀泥沙中的有机质、全氮、有效磷在产流历时中都呈现出先减小后增大的趋势,与产流历时呈较好的二次曲线关系;侵蚀泥沙中全磷和碱解氮随产流历时则呈现出持续减低的趋势,与产流历时都为较好的幂函数关系。土壤侵蚀模数与有机质、全氮以及全磷存在极显著负相关关系;侵蚀泥沙中有机质和有效磷则与泥沙颗粒组成中的粘粒和砂粒分别存在极显著正相关和负相关关系:侵蚀泥沙中全氮含量则和颗粒组成中各组分都存在极显著相关关系,且上述养分与各自对应的颗粒呈现良好的线性回归关系。因此,在自然坡面尺度上,土壤粘粒含量在不同土地利用类型间以荒草地最高、农耕地最低,在不同坡面位置间以下坡为高、上坡为低;侵蚀泥沙中砂粒随降雨产流历时的进程先增后减、粘粒则与之相反;侵蚀泥沙中养分与产流历时成二次曲线或幂函数关系,同时也与侵蚀泥沙颗粒组成各组分成不同程度的线性关系。3、小流域尺度下紫色土水土流失效应。以重庆市万州区戴家沟小流域为研究单元,以¹³⁷Cs示踪法为技术手段,结合自然降雨监测数据,研究探讨了土地利用类型、流域空间变异等对土壤侵蚀模数、土壤颗粒变化特征及养分流失特征的影响。不同地貌部位的侵蚀特征筹异显著,小流域上游、中游、下游的土壤侵蚀模数分别为4205.74 t·km²·a¹、2466.26 t·km²·a¹、1552.91 t·km²·a¹;上游马尾松林的土壤侵蚀模数为2839.92 t·km²·a¹,是中游、下游的1.35倍、10.59倍;上游农耕地土壤侵蚀模数为5343.74 t·km²·a¹,分别是中游、下游的1.96倍、2.92倍;上游柑桔林土壤侵蚀模数为3837.1 t·km²·a¹,分别是中游、下游的1.63倍、2.97倍。在降雨雨滴击溅,坡面径流搬运、迁移以及冲刷作用下,从上坡至中坡、下坡,表层土粘粒含量整体上呈增加趋势,粉粒含量随坡位降低而增加,砂粒含量上坡大于中坡及下坡。相同坡位,土壤颗粒随土层深度的变化规律为:从表层到中层、下层粕粒及粉粒含量先增加后减少,整体上呈增加趋势;砂粒含量先减少后增加,整体上呈减少趋势。流域位置对各土地利用类型土壤颗粒组成有显著影响。对荒草地和柑桔林而言,粘粒含量的变化趋势为上游＜中游＜下游,砂粒含量则呈相反规律;对农耕地而言,粘粒含量的变化规律为下游＜上游＜中游,砂粒含量为上游＞下游＞中游。流域下游土壤颗粒的比表面积高于中游和上游。在降雨、土地利用类型等众多因素的作用下,小流域侵蚀泥沙颗粒组成砂粒多沉积于流域局部,细颗粒、粉粒等随径流迁移到达流域出口,因此,呈现出流域侵蚀泥沙＜0.05 mm颗粒的比重、粗颗粒的含量低规律,其中＜0.05mm的比重高达80%,是砂粒比重的4倍。侵蚀泥沙中有机质、全氮含量与粘粒含量呈极显著正相关（R分别为0.921、0.860）,碱解氮含量与粘粒含量呈显著正相关;氮素与砂粒含量呈极显著负相关;有效磷及全磷含量仅与粉粒呈极显著正相关,相关系数分别为0.925、0.968。因此,在小流域尺度上,土壤侵蚀模数均在上游有最大值,下游有最小值;下游土壤颗粒的比表面积要高于中、上游的;侵蚀泥沙中以＜0.05 mm细颗粒为主,达80%;侵蚀泥沙中各养分与其颗粒组成也存在不同的相关性。4、不同尺度下紫色土水土流失效应对比分析。通过对不同尺度研究单元的土壤/泥沙颗粒组成、养分变化以及颗粒—养分耦合特征的比较分析,探讨了不同尺度间水土流失机理的差异以及尺度效应转化的可能性。从土壤颗粒组成来看,在径流小区尺度上,不同坡位间差异不大;在自然坡面尺度上,不同坡位出现了较大的差异;在小流域尺度上,不同坡位和不同流域位置间出现了明显的差异。土壤颗粒组成差异性的增加,可能是水土流失效应的影响因子多元化和复杂化以及各因子协同耦合关系复杂化的原因。在外界降雨条件相似的情况下,侵蚀泥沙中粘粒含量与产流历时的关系从径流小区尺度的不明显关系转变为自然坡面和小流域尺度下的二次曲线关系;砂粒含量与产流历时在径流小区、自然坡面和小流域尺度上的关系分别为幂函数、二次曲线和二次曲线关系;粉粒含量与产流历时在径流小区、自然坡面和小流域尺度上的关系分别为幂函数、无明显和二次曲线关系。从中可以发现,随着尺度的增大,侵蚀泥沙中各颗粒组分与产流历时的关系都有趋于呈现出二次曲线关系特征。从养分变化和产流历时的关系来看,从径流小区尺度到小流域尺度,有机质、全氮和碱解氮与产流历时的关系从幂函数关系转变为二次函数关系,全磷、有效磷与产流历时的关系从幂函数转变为一次函数的关系。从土壤颗粒和侵蚀泥沙的耦合关系来看,在径流小区尺度上,相似雨强下全钾含量与侵蚀泥沙粘粒和砂粒存在显著相关;在自然和小流域尺度上,有机质、全氮、全磷、碱解氮以及有效磷与侵蚀泥沙颗粒组成存在着一定程度的一次曲线关系;通过对比分析发现,随着尺度的增大,与侵蚀泥沙颗粒组成产生耦合关系的侵蚀养分更多,且耦合关系也产生了变化。从侵蚀模数与侵蚀泥沙量的关系来看,在径流小区尺度上,仅侵蚀泥沙中有机质含量与侵蚀泥沙量存在显著相关关系;在自然坡面和小流域尺度上,侵蚀泥沙中有机质、全氮以及碱解氮含量与侵蚀模数之间存在显著关系;土壤养分随着土壤侵蚀模数的增加而增加,且随着尺度的增加,具有这种关系的养分种类有增加趋势。在径流小区、自然坡面和小流域尺度上,土壤/泥沙颗粒变化、养分流失情况以及两者间的耦合关系都存在不同程度的差异性。这是由于在不同尺度上影响水土流失效应的因素不同以及主次顺序不同所致。在径流小区尺度上,水土流失效应主要受降雨特性和土壤特性的影响;而在自然坡面尺度上,地形和植被也是影响水土流失效应的主要因素;在小流域尺度上,则还需考虑这些因素的空间变异性。综上所述,本文从径流小区、自然坡面和小流域尺度对紫色土区水土流失效应机理以及尺度间的相互转化进行了探讨,获得了各尺度下土壤/泥沙颗粒变化、养分流失情况以及两者间的耦合关系,同时也得出影响因素是造成尺度效应的主要原因,在一定程度上揭示了紫色土区域水土流失机理以及尺度效应。但是,水土流失尺度效应还缺乏深入的理论研究,今后应在水土流失尺度效应理论方面开展更深入的研究,为建立不同空间尺度下水土流失效应定量评价模型和实现水土流失空间尺度效应定量评价与尺度转换提供依据。更多还原

【Abstract】 Globally,more than 70 percent of the areas are suffering the soil erosion,and the loss amount of surface soil arrives at 25 billion ton per year.As one of the countries which is suffering the most serious erosion,the preexisting study about the soil loss is still inadequate to meet the national development and ecological construction in China.Due to the scale effect,the characteristics of soil loss in the different scales are combined with each other and also different from each other.The previous studies were mostly focused on the soil erosion developing in the single scale（e.g.soil slot, runoff plot,slope etc.）,however,the comparisons among these scales are relative lacking.At the same time,the effects of soil loss appear the nonlinear influences along with enlarging study area.In the regional or even worldwide scale,the change of different influence factor’s weight is the critical content in order to reveal the mechanism of soil loss in different scale.Most of all,the soil erosion in the small scale is the base.So,it has important theory and practice significances to illustrate the effects of soil erosion in three scales（runoff plot,toposequence and catchment） and the internal mechanism.The sediment in the Yangtze River mostly originates from the purple soil in the drainage area. As a special soil type of China,the purple soil is characterized by soft texture and high erodibility. Despite high productivity,the purple soil is very vulnerable to weathering and soil loss.Among all China soil types,the erosion area and erosion intensity of purple soil ranked second behind the Loess. In the Three Gorge region,the human activities also accelerate the soil erosion process.The soil loss problem is getting worse year by year and has become a threat to the ecology safety and sustainable development in this region.So,the study focused on the purple soil area,and aimed at revealing the effects of soil erosion in different scales,establishing the foundation for controlling soil erosion and constructing regional soil loss predicted model.Three scales in the Daijiagou catchment,including catchment,toposequence and runoff plot,were applied in our research.With the aids of monitoring equipment,the sediment and runoff were observed,the nutrient contents were tested.1.Within the runoff plot scale,the method of simulated rainfall was applied.Consequently,the changes of soil particle and nutrient loss on the different slope positions and different rainfall intensities were investigated.Moreover,the relationships among the soil particle,runoff and nutrient were analyzed.It is found,under the effects of splashing by the raindrop,detaching/dispersing, transporting and scouring by the flow,the contents of clay and silt decline with the increasing content of the sand in the upper-slope.Different from the upper-slope,the contents of clay in the mid- and lower-slope increase,and the content of sand decreases in the lower-slope.Generally,the losing rates on the different slope positions present the increasing trend with the rainfall intensity enhancing.The difference of soil particle between pre- and post-rainfall is positive correlated with the nutrient’s loss in various degrees.When comparing with the changes,the soil aggregate with＜0.25mm and＞2mm increase significantly after rainfall,and the soil aggregate with else sizes increase.The correlation between fractal dimensions of soil aggregate（D） and nutrient losing demonstrates that,the greater difference in D（pre- and after-rainfall） follows with the more much nutrient’s losing rate.All sediment loads under the different rainfall intensities exhibit the processes from rising to declining.The time appearing the maximum concentration of sediment is shorter with more enhancive rainfall intensity,and the similar trend still occurs in the maximum nutrient concentration of the sediment.However,not all the nutrient content of sediment increases along with the rainfall intensity enhancing,due to the different adsorbability of nutrient on soil particle.The cumulative quantity of runoff’s nutrient increases correspondingly along with the more enhancing rainfall intensity and longer duration of runoff generation.The velocity of runoff and the duration of runoff generation are related with a power function under the relative larger rainfall intensity,and the relation is transfer into the quadratic curve under the weak rainfall intensity.The relations between the runoff intensity/runoff velocity and the concentration of total nitrogen（TN）/total phosphorus（TP） are unremarkable,however,significant correlations exists when comparing with the corresponding capacity of losing TN and TP.In general,fine soil particle decreases and coarse soil particle increases in the upper-slope during the erosive process,and opposite phenomena appears in the lower-slope.The changes of soil aggregates with＜0.25mm and＞2mm increase after rainfall,and losing nutrient is related with soil texture,stability of soil aggregate;The sediment load,losing nutrient is increasing along with the enhancing rainfall intensity and prolonging duration of runoff generation,but the characteristics are distinguishing for different nutrient elements.2.Within the toposequence scale,with the help of ¹³⁷Cs tracer technique,the soil erosion modulus in different topography positions and different land use were detected.The source of sediment was analyzed,and discussed the difference of the soil erosion modulus in different conditions（topography and land use）.At the same time,the changes of particle size and nutrient content in the slope surface,sediment and runoff were analyzed;the relationships among them were investigated,based on the observed data from the outlet of toposequence.It was found,the position and the land use significantly influences the spatial distribution of soil particle.The sequence of soil clay content in the different land is waste-grassland＞forest land（open forest land,orange forest land,peach forest land）＞cropland.The order of soil clay content in the different position with same land use is upper-slope＞mid-slope＞lower-slope.The sand content of sediment particle increases firstly and reduces afterward along with the erosion process,and the content of clay presents the reverse phenomena.Both of above mentioned textures show the quadratic curve relation with the runoff duration.In the toposequence,the average content of every nutrient element in different land use present the same characteristics:upper-slope＜mid-slope＜lower-slope.The organic matter, total nitrogen and available phosphorus in the sediment appear the same trends,which is increasing firstly and reducing afterward along with runoff duration.In addition,their contents exhibit the quadratic curve function with the runoff duration.The total phosphor and the available nitrogen in the sediment present the declining trend along with the runoff duration,and their contents exhibit the power function with the runoff duration.There is a significant negative correlation between the soil erosion modulus and the contents of organic matter,total nitrogen,total phosphorus.The content of organic matter and available phosphor presents significant positive correlation with the content of clay,but the opposite relationship occurs when facing the content of sand.There is a significant correlation between the content of total nitrogen and soil particle.Moreover,the nutrients what aforementioned correlate with the corresponding soil particle by linear function.Collectively,in the toposequence scale,the clay content is highest in the waste grassland,and lowest in the cropland.Lower-slope appears the high concentration of clay and the upper-slope appears the low concentration.The sand content of sediment increases firstly and reduces afterward along with the erosion process,and the content of clay presents the reverse phenomena.The nutrient content in the sediment correlated with the runoff duration by the quadratic curve or power functions, and is linear with the soil particle in varying degrees.3.Within the catchment scale,with the aids of ¹³⁷Cs tracer technique and combining the monitoring data of precipitation,the influences of the land use types and the spatial variability effecting on the soil erosion modulus,soil particle and the nutrient loss were discussed.It was found, the average soil erosion modulus are 4205.74 t·km^-2·a^-1,2466.26 t·km^-2.a^-1 and 1552.91t·km^-2·a^-1 respectively in the upper,middle and lower reaches of Daijiagou catchment.In the upper reaches, the soil erosion modulus in the masson pine land,cropland and orange forest land are 2839.92t·km^-2·a^-1,5343.74 t·km^-2·a^-1 and 3837.1 t·km^-2·a^-1 respectively.For the masson pine land,the average soil erosion modulus are 2839.92 t·km^-2·a^-1,2103.64 t·km^-2·a^-1 and 268.17 t·km^-2·a^-1 respectively in the upper,middle and lower reaches.For the cropland,the average soil erosion modulus are 5343.74 t·km^-2·a^-1,2726.40 t·km^-2·a^-1 and 1830.05 t·km^-2·a^-1 respectively in the upper, middle and lower reaches;In the orange forest land,the average soil erosion modulus are 3837.10 t·km^-2·a^-1,2354.05 t·km^-2·a^-1 and 1291.95 t·km^-2·a^-1.Due to the effects of splashing by the raindrop, detaching/dispersing,transporting and scouring by the flow,the clay and silt contents on the slope surface increase from the upper- to lower-slope,and the sand content in upper-slope is higher than that in mid- and lower-slope.With the same position（upper-,mid- or lower-slope） of the whole slope,the clay and silt contents increase firstly and decrease afterward from the surface soil to deep soil.The different positions and land use types in the catchment have deeply influenced the soil mechanical composition.In the waste-grassland and the orange forest land,the clay content decreases from the upstream to downstream of catchment;but the reverse trend is presented by the sand content;In the cropland,the clay content is the most in mid-reaches of the catchment,and the clay content is lest in the lower reaches.The soil specific area（SSA） in the lower reaches is larger than that in middle and upper reaches.In the different rainfall conditions and land use types,the coarse sediment be settled down in some areas of catchment and the fine sediment can be transferred into the outlet of catchment following with the runoff.So in the outlet of catchment,the specific gravity of the sediment with＜0.05 mm is 80%,equals to 4 times the specific gravity of the sand. According to the correlation analysis,the organic matter and total nitrogen in the sediment have significantly correlated with the clay content（correlation coefficient R is 0.921 and 0.860 respectively）.And the available nitrogen in the sediment had positive correlation with the clay content.The nitrogen in the sediment had significant negative correlation with the sand content,and the available phosphorus and total phosphorus in the sediment had highly significant correlation with the silt content,the correlation coefficient is 0.925 and 0.968 respectively.Therefore,in the catchment scale,the highest and lowest soil erosion modulus appears in the upper and lower reaches respectively.The soil specific area（SSA） in the lower reaches is larger than that in the middle and upper reaches.The sediment particle is mostly composed by the fine particle with＜0.05mm,and there are some different correlations between the sediment nutrients and soil mechanical compositions.4.Comparison and analysis of the soil erosion’s characteristics in the different scales. According to the changes of soil/sediment particle size and the nutrient loss,the relationship between them in different research scales,the mechanism of soil loss and the scale effect transferring were discussed.It was found,in the runoff plot scale,the variations of soil particle in the different slope positions are unobvious,but remarkable variation appears in the scale of toposequence and catchment.Because of the complex factors that influence the soil erosion and the complicated relationships among different influencing factors,the variability of soil particle becomes more and more obviously along with the scales enlarging.Under the same rainfall condition,in the runoff plot area,the relationship between clay content and runoff generation time is not obvious,but in the scales of toposequence and catchment,the relationship between the clay content in sediment and runoff generation time is regressed by the quadratic curve.In the scales of runoff plot,natural slop and catchment,the relationships between the sand content in sediment and the runoff generation time demonstrate the functions of power,quadratic and quadratic respectively.And the relationships between silt content and runoff generation time in the runoff plot is power function,the relationship is changed into the quadratic function in the catchment.The relationships between all kinds of sediment particles and the runoff generation time tend to appear the quadratic function when the scale is enlarged from the runoff plot to catchment,and the relationship between soil organic matter and runoff generation time is transferred from power function into quadratic function,same variety is appeared in the relationship between total nitrogen,available nitrogen and the runoff generation time.In addition,the relationship between total phosphor and runoff generation time is varied from the power function into linear function,the same changes is occurred between the avail phosphor and the runoff generation time.According to the relationship between soil particles and the sediment, under parallel rainfall conditions,the correlation between the total potassium and clay content,and content in sediment is significant,in the runoff plot.In the scales of toposequence and catchment, the linear relationship between the sediment particle size and the nutrient content（soil organic matter, total nitrogen,total phosphor,available nitrogen,and available phosphor） do exist.According to the comparison and analysis,the number of nutrient element which is related with the soil particle size is enlarged.In the scale of runoff plot,there is a significant correlation between soil organic matter and sediment load,and the soil organic matter,total nitrogen and available nitrogen in the sediment significantly correlates with the soil erosion modulus when facing the scales of natural and catchment.The soil nutrient loss become more seriously along with more serious soil erosion modulus.It has degrees of difference between soil/sediment particles composition and nutrient loss,as well as their relationship in the scales of runoff plots,toposequence and small catchment.That is because of differing the impact of soil erosion at different scales,as well as primary and secondary effects of the different factors that result in a different order.In the scale of runoff plot,soil erosion is mainly impacted by the characteristics of rainfall and soil.However,topography and vegetation are the main factors affecting soil erosion in a toposequence scale.Then it needs to consider these factors of spatial variability in the small catchment scale.To sum up the above arguments,we studied the soil erosion effect in different scales,and discussed their transformation.Through the monitoring outside and experiment inside,the changes of soil/sediment particle size,nutrient loss and their relationship in different scales were detected, which also is the critical reason causing the scale effects of soil erosion.The research partly revealed the soil loss mechanism and scale effect in the purple soil area.However,it still needs more theory study about the scale effect.We should e develop the research about the scale effect of soil erosion further,which will provide the basis for establishing quantitative soil erosion predicted model,and realizing the quantitative evaluation of soil erosion effects for spatial scale and scale transformation.更多还原