Study of Spatial and Temporal Processes of Soil Erosion on Sloping Land Using Rare Earth Elements As Tracers

Rare earth elements (REE) were used to study the temporal and spatial processes of soil erosion from different depths and sections of a slope. Two simulated rainfall events were applied to a prepared plot with a slope of 22°. The total runoff and sediment yield were collected every minute during the rainfall events. During the first twenty minutes of the first rainfall event, the average rate of rill erosion and the accumulated sediment yield due to rill erosion was 0.5 and 0.3 times higher than for sheet erosion. During this time, most of the erosion occurred on the lower one third of the plot. After 20 min, rill erosion became the dominant process on the slope. The average acceleration in the rate of rill erosion, the rate of rill erosion and the accumulated sediment yield due to rill erosion were 42, 6 and 4 times higher than that of sheet erosion, respectively. During the first 35 minutes of the second rainfall event, the average acceleration in the rate of rill erosion was 6～9 times higher than that of sheet erosion. Afterwards, the slope became nearly stable with little change in either rill or sheet erosion rates. Initially, most of the rill erosion occurred in the lower third of the slope but later the preexisting rillhead in the middle section of the slope became reactivated and erosion in this section of the slope increased rapidly. These results indicate that REE tracer technology is a valuable tool for quantifying spatial and temporal changes in erosion from a soil slope.

Soil and water loss in the Lancang River-Mekong River watershed (in Yunnan section, China) and its control measures

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Evaluating soil erosion by water in a small alpine catchment in Northern Italy: comparison of empirical models

To quantify water erosion rates and annual soil loss in mountainous areas,two different empirical models were used to estimate the effects of soil erosion in a small mountain basin,the Guerna Creek watershed,located in the Central Southern Alps(Northern Italy).These two models,Revised Universal Soil Loss Equation(RUSLE) and Erosion Potential Model(EPM),were implemented in a Geographical Information System,accounting for the geographical,geomorphological,and weather-climate parameters,which are fundamental to evaluating the intensity and variability of the erosive processes.Soil characterization was supported by laboratory analysis.The results(computed soil loss of 87 t/ha/year and 11.1 m^(3)/ha/year,using RUSLE equation and EPM method,respectively,and sediment yield of 7.5 m^(3)/ha/year using EPM method) were compared to other studies reported in the literature for different case studies with similar topographic and climatic features,as well as to those provided by the European Soil Data Centre(ESDAC).In both cases,the agreement was satisfactory,showing consistency of the adopted procedures to the parametrization of the physical processes.

Contribution of a Geographical Information System to the Study of Soil Loss Dynamics in the Lobo Catchment (Côte d’Ivoire)

The Lobo watershed is highly anthropogenic since it has become the main production area for cocoa and coffee in C?te d’Ivoire. It therefore seems important to quantify soil loss by water erosion in this region. The Wischmeier modeling was used to model the main factors involved in erosive phenomena. Crosscutting of thematic maps and the application of the USLE formulas made possible to evaluate the erosion rate at the watershed scale in 1986 and 2014. Although soil is susceptible to erosion and erosivity is increased, the results indicate a growth in soil loss estimated at 90.12%. Some agroforestry efforts are still possible to help reducing those soil losses.

Erosion-induced recovery CO_(2) sink offset the horizontal soil organic carbon removal at the basin scale

To improve soil carbon sequestration capacity,the full soil carbon cycle process needs to be understood and quantified.It is essential to evaluate whether water erosion acts as a net source or sink of atmospheric CO_(2)at the basin scale,which encompasses the entire hydrological process.This study introduced an approach that combined a spatially distributed sediment delivery model and biogeochemical model to estimate the lateral and vertical carbon fluxes by water erosion at the basin scale.Applying this coupling model to the Dongting Lake Basin,the results showed that the annual average amount of soil erosion during 1980-2020 was 1.33×10^(8)t,displaying a decreasing trend followed by a slight increase.Only 12% of the soil organic carbon displacement was ultimately lost in the riverine systems,and the rest was deposited downhill within the basin.The average lateral soil organic carbon loss induced by erosion was 8.86×10^(11)g C in 1980 and 1.50×10^(11)g C in 2020,with a decline rate of 83%.A net land sink for atmospheric CO_(2)of 5.54×1011g C a^(-1)occurred during erosion,primarily through sediment burial and dynamic replacement.However,ecological restoration projects and tillage practice policies are still significant in reducing erosion,which could improve the capacity of the carbon sink for recovery beyond the rate of horizontal carbon removal.Moreover,our model enables the spatial explicit simulation of erosion-induced carbon fluxes using costeffective and easily accessible input data across large spatial scales and long timeframes.Consequently,it offers a valuable tool for predicting the interactions between carbon dynamics,land use changes,and future climate.

Analyzing Forest Effects on Runoff and Sediment Production Using Leaf Area Index

Quantifying the effects of forests on water and soil conservation helps further understanding of ecological functions and improving vegetation reconstruction in water-eroded areas.Studies on the effects of vegetation on water and soil conservation have generally focused on vegetation types or vegetation horizontal distribution densities.However,only a few studies have used indicators that consider the vegetation vertical distribution.This study used the leaf area index(LAI) to investigate the relationship between forests and water and soil conservation in experimental plots.From 2007 to 2010,rainfall characteristics,LAI,and water and soil loss in 144 natural erosive rainfall events were measured from five pure tree plots(Pinus massoniana).These tree plots were located in Hetian Town,Changting County,Fujian Province,which is a typical water-eroded area in Southern China.Quadratic polynomial regression models for LAI and water/soil conservation effects(RE/SE) were established for each plot.The RE and SE corresponded to the ratios of the runoff depth(RD) and the soil loss(SL) of each pure tree plot to those of the control plot under each rainfall event.The transformation LAIs of the LAI–RE and LAI–SE curves,as well as the rainfall characteristics for the different water/soil conservation effects,were computed.The increasing LAI resulted in descending,descending–ascending,ascending–descending,and ascending trends in the LAI–RE and LAI–SE curves.The rainfall frequencies corresponding to each trend of LAI–RE and LAI–SE were different,and the rainfall distributions were not uniform per year.The effects of soil conservation in the plots were superior to those of water conservation.Most of the RE and SE values presented a positive effect on water and soil conservation.The main factor that caused different effects was rainfall intensity.During heavy rains(e.g.,rainfall erosivity R = 145 MJ mm/ha h and maximum 30 min intensity I30 = 13 mm/h),the main effects were positive,whereas light rains(e.g.,R = 70 MJ mm/ha h and I30 = 8 mm/h) generally led to negative effects.When the rainfall erosivity was lower than that of the positive or the negative effects to a threshold and the tree LAI reached a transformation value,the relationships between LAI and RE or SE notably transformed.Results showed that the plottransformation LAIs for water and soil conservation during rainfall events were both approximately 1.0 in our study.These results could be used to come up with a more efficient way to alleviate water and soil loss in water-eroded areas.

Dynamic analysis of mainstream area and vegetation coverage degree of Songhua River based on RS and GIS techniques

Based on remote sensing technique,using 1990's Landsat TM data and 2000's Landsat ETM data,the authors conducts the comparative study of mainstream area of Songhua River by means of human-computer inter-action method.The results show that the area of Songhua River mainstream was 738 102 km 2 in 1990,and was 810.451 km 2 in 2000.From 1990 to 2000,the increased area of river mainstream is up to 72.349 km2 due to soil erosion and water loss.Meanwhile,the dynamic changes of surrounding vegetation cover are also studied.It is estimated that the trend of surrounding soil erosion and water loss of Songhua River mainstream becomes worse in Jilin Province.

生物炭施加垄沟集雨种植对水土流失及紫花苜蓿草产量的影响

为缓解我国黄土高原区干旱胁迫和控制水土流失,本研究采用裂区设计,生物炭施加模式(生物炭施加和无生物炭施加)为主区,耕作模式(打结垄、开敞垄和平作)为副区,研究不同生物炭施加模式和耕作模式对土壤水分、径流、泥沙流失、养分流失、紫花苜蓿(Medicago sativa L.)干草产量和水分利用效率的影响。试验结果表明,在2019和2020年紫花苜蓿生育期,与平作处理相比,开敞垄和打结垄处理的径流量、泥沙、全氮、全磷、有机质流失量分别减少20.1%~37.7%和60.1%~64.7%,54%~75.5%和77.1%~87.6%,44.4%~65.5%和49.0%~81.8%,36.7%~75.3%和48.6%~87.3%,48.2%~72.9%和58.6%~85.4%,土壤贮水量、紫花苜蓿干草产量和水分利用效率分别增加39.5~52.1和31.2~60.5 mm,26.2%~31.7%和26.5%~35.2%,10.07~14.86和12.14~16.55 kg·hm^(-2)·mm^(-1)。与无生物炭施加处理相比,生物炭施加处理的径流量、泥沙、全氮、全磷和有机质流失量分别减少48%~69%,94%~125%,12%~24%,28%~46%和35%~48%,土壤贮水量、紫花苜蓿干草产量和水分利用效率分别增加42.93~26.09 mm,106%~111%和1.96~6.90 kg·hm^(-2)·mm^(-1)。本研究表明,生物炭施加打结垄沟集雨种植是该区域适宜耕作模式。

基于遥感技术的东北黑土区水土流失动态监测研究

东北黑土区是我国重要的商品粮基地,近年来面临水土流失严重、面积减小、土壤质量下降等问题,已成为目前土壤保护工作中亟待解决的重要问题。以东北黑土区2018年和2022年两期遥感影像与水土保持措施的实地调查数据作为数据源,利用目视识别法开展影像解译,并通过中国土壤流失方程CSLE进行土壤侵蚀模数的计算,对东北黑土区的水土流失变化情况及原因进行分析,结果表明:耕地、草地、建设用地、其他土地面积减少,园地、林地、交通运输用地、水域及水利设施用地面积增加,造林、种草、封育、地埂、水平阶/反坡梯田等面积共增加0.84万km^(2);对比2018—2022年东北黑土区的水土流失情况,整体呈向好趋势,土壤侵蚀面积共减少约1.01万km^(2);从侵蚀强度来看,除轻度侵蚀面积增加约0.45万km^(2)外,中度、强烈、极强烈、剧烈侵蚀面积分别减少约0.43万、0.24万、0.28万、0.51万km^(2);从不同省份侵蚀面积变化情况分析,内蒙古自治区东四盟的侵蚀面积减少最多,共减少约0.37万km^(2),辽宁省侵蚀面积变化最小,共减少约0.06万km^(2);耕地、建设用地等土地利用类型面积的减少,以及林地、交通运输用地等土地利用类型面积的增加,均可大幅减少土壤侵蚀面积,同时水土保持措施面积的增加也可有效阻止土壤侵蚀的发生。总体来看,东北黑土区水土流失治理效果显著,生态环境得到改善,持续进行东北黑土区水土流失治理对环境保护具有重要意义。

中国东北黑土区土壤复合侵蚀研究进展与展望

土壤复合侵蚀是在2种及以上侵蚀营力交互作用或耦合作用下发生的侵蚀现象。东北黑土区多营力复合侵蚀具有时空交替和叠加的特征。近年来,黑土区土壤复合侵蚀研究在发生机理及对土壤退化的作用等方面取得了一定的进展。基于前人研究成果,系统总结了冻融作用下的土壤水蚀或风蚀、耕作与水力复合侵蚀、风水复合侵蚀以及多营力复合侵蚀在发生机理和研究方法等方面的研究现状,归纳了研究中存在的主要问题,提出了今后在复合侵蚀机制与模拟试验方法等研究中需要解决的关键科学问题以及应关注的试验模拟技术、定量评估方法,以期为未来东北黑土区土壤复合侵蚀研究提供参考。

三峡库区不同种植制度的坡地水土流失特征

剖析农业种植制度对库区水土流失的季节性影响,有助于深刻认识库区农业区域水土流失发生规律。基于2018—2021年共4年期间中国科学院三峡库区水土保持与环境研究站自有粮油作物、蔬菜作物、柑橘果园、灌草撂荒4种种植制度小区的水土流失监测数据的整理分析,结果表明:库区4—8月降雨量占全年降雨量的60.4%~75.8%,年内中雨发生频率最高,占73.63%,大雨次之,占19.78%,暴雨频率最低,占6.59%。4种种植制度小区中,柑橘果园的平均径流深、土壤侵蚀强度都最大,表明柑橘果园是该区域重要的水土流失源地。蔬菜作物和粮油作物是库区坡耕地的主要农作物,地块耕作频繁,易于发生水土流失,但不同种植制度下的作物生长周期、田间管理措施存在明显差异,对植被覆盖度、土壤紧实度产生显著影响,进而影响地表径流发生和土壤侵蚀过程。因此,对于三峡库区侵蚀性降雨年内分布不均和不同种植制度田间耕作管理、植被覆盖的季节性差异,应有针对性地采取防治措施,以有效保护农业土壤资源。

Exploring the factors influencing the hydrological response of soil after low and high-severity fires with post-fire mulching in Mediterranean forests

Despite ample literature,the influence of the individual soil properties and covers on the hydrological response of burned soils of forests has not clearly identified.A clear understanding of the surface runoff and erosion rates altered by wildfires and prescribed fires is beneficial to identify the most suitable post-fire treatment This study has carried out a combined analysis of the hydrological response of soil and its driving factors in burned forests of Central-Eastern Spain.The pine stands of these forests were subjected to both prescribed fire and wildfire,and,in the latter case,to post-fire treatment with mulching.Moreover,simple multi-regression models are proposed to predict runoff and erosion in the experi-mental conditions.In the case of the prescribed burning,the fire had a limited impact on runoff and erosion compared to the unburned areas,due to the limited changes in soil parameters.In contrast,the wildfire increased many-fold the runoff and erosion rates,but the mulching reduced the hydrological response of the burned soils,particularly for the first two-three rainfalls after the fire.The increase in runoff and erosion after the wildfire was associated to the removal of the vegetation cover,soil water repellency,and ash left by fire;the changes in water infiltration played a minor role on runoff and erosion.The multi-regression models developed for the prescribed fire were accurate to predict the post-fire runoff coefficients.However,these models were less reliable for predictions of the mean erosion rates.The predictions of erosion after wildfire and mulching were excellent,while those of runoff were not satisfactory(except for the mean values).These results are useful to better understand the relations among the hydrological effects of fire on one side and the main soil properties and covers on the other side.Moreover,the proposed prediction models are useful to support the planning activities of forest managers and hydrologists towards a more effective conservation of forest soils.

大洋河水库除险加固工程水保措施及水土流失预测

以大洋河水库除险加固工程为例,介绍了工程施工期间水土流失防治措施,并进行水土流失防治效果预测。结果表明,通过采取水土流失防治措施,可以有效地控制水土流失,维护并增强区域水土保持功能,并有利于项目区域生态环境的恢复。

Using the USLE: Chances, challenges and limitations of soil erosion modelling

To give soils and soil degradation,which are among the most crucial threats to ecosystem stability,social and political visibility,small and large scale modelling and mapping of soil erosion is inevitable.The most widely used approaches during an 80year history of erosion modelling are Universal Soil Loss Equation (USLE)-type based algorithms which have been applied in 109 countries.Addressing soil erosion by water (excluding gully erosion and land sliding),we start this review with a statistical evaluation of nearly 2,000 publications).We discuss model developments which use USLE-type equations as basis or side modules,but we also address recent development of the single USLE parameters (R,K,LS,C,P).Importance,aim and limitations of model validation as well as a comparison of USLE-type models with other erosion assessment tools are discussed.Model comparisons demonstrate that the application of process-based physical models (e.g.,WEPP or PESERA) does not necessarily result in lower uncertainties compared to more simple structured empirical models such as USLE-type algorithms.We identified four key areas for future research:(i) overcoming the principally different nature of modelled (gross) versus measured (net) erosion rates,in coupling on-site erosion risk to runoff patterns,and depositional regime,(ii) using the recent increase in spatial resolution of remote sensing data to develop process based models for large scale applications,(iii) strengthen and extend measurement and monitoring programs to build up validation data sets,and (iv) rigorous uncertainty assessment and the application of objective evaluation criteria to soil erosion modelling.

The development of U.S.soil erosion prediction and modeling

Soil erosion prediction technology began over 70 years ago when Austin Zingg published a relationship between soil erosion(by water)and land slope and length,followed shortly by a relationship by Dwight Smith that expanded this equation to include conservation practices.But,it was nearly 20 years before this work's expansion resulted in the Universal Soil Loss Equation(USLE),perhaps the foremost achievement in soil erosion prediction in the last century.The USLE has increased in application and complexity,and its usefulness and limitations have led to the development of additional technologies and new science in soil erosion research and prediction.Main among these new technologies is the Water Erosion Prediction Project(WEPP)model,which has helped to overcome many of the shortcomings of the USLE,and increased the scale over which erosion by water can be predicted.Areas of application of erosion prediction include almost all land types:urban,rural,cropland,forests,rangeland,and construction sites.Specialty applications of WEPP include prediction of radioactive material movement with soils at a superfund cleanup site,and near real-time daily estimation of soil erosion for the entire state of Iowa.

A hillslope version of the revised Morgan,Morgan and Finney water erosion model

The revised Morgan,Morgan and Finney(rMMF)water erosion model calculates annual surface runoff and soil loss from field-sized areas.The original version of the rMMF is neither suited to calculate water erosion along irregular hillslopes,nor capable to allow infiltration of once generated surface runoff at places where the runoff speed slows down,and infiltration could occur under natural conditions.The aim of this article is to describe a new hillslope version of the rMMF model that allows infiltration of surface runoff,and to show examples of soil erosion modelling along real and hypothetical hillslopes.The new hillslope version(hMMF)splits the entire hillslope into a number of sections that have individual properties,such as slope angle,slope length,soil properties and vegetation characteristics.The surface runoff along the slope is calculated by summing the volume of surface runoff generated in a particular section with the surface runoff coming from the immediate upsiope section.The related sediment transport is calculated for each section using the calculated detachment for the section,the sediment coming from the upsiope section and the transport capacity.A new variable is introduced to account for infiltration of surface runoff and allows simulating the effects of soil and water conservation structures on water erosion.The model was tested using measured data from plots in Africa,Asia,the US and Europe,as well as for a surveyed hillslope in Tunisia(Barbara watershed).Overall,the performance of the hMMF was reasonable for surface runoff and poor for soil loss when recommended input variable values are used.Calibration of the model resulted in a good performance,which shows the capability of the hMMF model to reproduce measured surface runoff and erosion amounts.In addition,realistic water erosion patterns on hillslopes with soil and water conservation can be simulated.

基于近20年《中国水土保持公报》的水土流失治理分析

水土保持是生态文明建设的重要组成部分,也是反映经济社会发展与生态环境质量动态平衡的重要综合指标。基于近20 a的《中国水土保持公报》,分析了水土流失现状,总结了水土保持工作进展,深入探究了水土流失动态变化成因及水土保持阶段性成效,研究成果对评价水土保持工作成效具有重要理论意义。研究结果表明:①与20世纪80年代末相比,2020年全国水土流失面积下降了26.6%,相较于20世纪初下降了24.4%;②2011年以前水土流失以中度及以上强度为主,2018年以后轻度流失面积占比超过60%;③水土流失综合治理是水土流失面积降低的主要原因;近20 a来,11条主要江河年总输沙量下降了72.4%,年输沙量与累计水土流失治理面积呈显著的负相关关系(R 2=0.90)。现阶段我国水土流失治理由“面”向“点”纵深推进,水土保持工作迈入高质量发展。研究成果可为我国水土保持工作评价及水土保持高质量发展提供定量数据和理论基础。

十大孔兑流域水土流失分布特征及防治对策

[目的]通过分析十大孔兑水土流失面积、强度及水土流失动态变化,为流域综合治理提供参考依据。[方法]基于全国土壤侵蚀遥感调查结果和全国水土流失动态监测成果,对比分析流域水土流失及其分布、动态变化。[结果]十大孔兑流域植被面积占流域面积的63.97%,以中低覆盖和低覆盖为主,分别占植被覆盖面积的48.85%和36.54%。2021年水土流失面积为4374.98 km 2,占流域面积的40.63%;与2020年、1999年和1985年相比,2021年水土流失分别减少46.32,3664.50,4958.03 km 2,水土流失主要分布在草地、林地、耕地和其他土地4个地类上,占水土流失总面积的96.69%。[结论]十大孔兑依然是黄河流域水土流失治理的难点地区,高强度侵蚀减少与年度监测成果未考虑沟道侵蚀有关;该区应坚持以“以沙棘种植为主的植被建设,以淤地坝建设为重点的工程布局,以锁边固沙为前提的治沙方针,大力推进拦沙换水试点工程”的流域综合治理策略。

城市水土保持区划及水土流失防控策略——以深圳市为例

新型城镇化是我国新时期社会经济发展的重大战略,城镇化进程带来的资源与环境需求对新时期水土保持工作提出了高质量发展的要求。深圳市作为高度城镇化地区,长期引领城市水土保持工作,但并未形成适合自身高密度经济单元、高科技产业类型、高质量环境要求的水土保持区划。以深圳市为研究对象,通过数理统计方法构建了水土保持区划指标体系;基于层次聚类分析和地理信息系统(GIS)空间叠加分析等定量手段和定性修正,划定了以最低行政层级的街道为基本单元的水土保持区划方案,并针对各分区水土流失特征与经济社会发展定位,提出了区域化水土流失防控重点和策略。区划方案与城市空间扩张、内部功能调整形成的格局一致,充分体现了深圳市城市水土保持特色,可用于指导深圳市水土保持分区审批、分类管理、分级防控,进而为实现深圳新时代的历史使命提供支撑。

基于径流小区实测的干热河谷土壤侵蚀荟萃分析

为详细了解干热河谷地区的土壤侵蚀状况,通过对径流小区资料的广泛收集、整理和标准化分析,对干热河谷主要土地利用类型的土壤侵蚀模数和水土保持措施效益进行定量评价,并将当地主要土地利用类型平均坡度下的土壤侵蚀模数与容许土壤流失量进行对比分析。结果表明:(1)灌草地、农地、园地和裸地等主要土地利用类型标准坡长坡度条件下的土壤侵蚀模数分别为110.88,389.58,320.66,507.87 t/(km^(2)·a),呈现出裸地最大,农地和园地次之,灌草地最低的特点。(2)封禁、水平阶整地、梯田和植物篱等水土保持措施均能较好地发挥水土保持效益,平均可以减少72%的土壤侵蚀量。(3)各流域主要土地利用类型,特别是农地和园地在当地平均坡度下的土壤侵蚀模数明显高于容许土壤流失量,说明该地区土壤侵蚀状况仍相当严峻。研究结果将有助于进一步深化对干热河谷地区土壤侵蚀规律的认识,并为后续水土流失治理和水土保持措施优化配置提供技术支撑。