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1.
Despite the fact that soil erosion by water causes considerable on-site and off-site problems, farmers in Europe are reluctant to adopt prevention and control measures when such measures require additional labour and material inputs. This paper documents the impact of multiple sowing of small grains on concentrated flow erosion rates and grain production for a winter triticale field (X Triticosecale Wittmack ex. A. Camus) in the Belgian loess belt. Multiple sowing refers to drilling more than once in zones of concentrated flow erosion in order to increase the total root mass in this zone. Multiple sowing strongly altered the morphology of erosion channels and reduced soil loss significantly. Statistical analysis confirmed that differences in channel dimensions could be explained by the seedling density. Doubling the root mass in the topsoil by multiple sowing, resulted on average in a reduction of soil loss by 42% for the whole growing season. For the winter period, soil loss reduction, mainly attributed to the triticale roots, amounted even to 53%, showing the tremendous impact of seedling roots on soil erosion by concentrated overland flow in the early stages of vegetation growth. Furthermore, total grain yield in the multiple drilled zones was not significantly smaller compared to the conventionally drilled parts of the field. Grain size of cereals was slightly smaller. The results of this case study indicate that double sowing in concentrated overland flow zones may be a viable soil erosion control technique.  相似文献   

2.
Farmers in Europe want to control soil erosion in ways that are easily incorporated in their normal practices. We have investigated the possibility of reducing soil erosion by concentrated flow (i.e. rill and gully erosion) through increasing the root density of cereal crops. In situ root density measurements on cereal fields were combined with laboratory flume experiments on samples, taken in single‐ and double‐drilled fields, of which the above‐ground biomass was clipped. During the laboratory experiments no significant effect of root densities on critical shear stress or channel erodibility was observed because of interactions with other changing parameters (e.g. ageing effects). Therefore, the expected relative detachment rates as a function of plant root density were calculated using an empirical equation. During the first 75 days of the crop growth season relative soil detachment rates for single‐drilled field parcels can be reduced up to 50% compared with a rootless field, whereas relative soil detachment rates in double‐drilled field parcels can be reduced up to 60% in this period. Thereafter, plant roots in double‐drilled field parcels reduce relative soil detachment rates on average by 9% compared with single‐drilled field parcels (up to an absolute maximum of 90% compared with rootless soils). During the growing season, not only root density increases but also the vegetation cover changes, which enhances soil protection from erosion. Therefore, cereal roots will help to conserve the soil when seed is drilled at double rates, especially during the early growth stages and in fields with medium risk of concentrated flow.  相似文献   

3.
Concentrated flow experiments using a small hydraulic flume and a constant flow discharge and bed slope have been conducted in order to investigate the effects of rock fragment cover (Rc) on sediment yield for an initially wet and an initially air-dry loamy topsoil. The experimental results indicate that Rc reduces concentrated flow erosion rates (E) in an exponential way (i.e., E=e−bRc), which is similar to previously reported relations for other water erosion processes such as interrill erosion and sheet-rill erosion measured on runoff plots. The decay rate (b) of this exponential relationship increased throughout the experiments because of scour-hole development and bed armouring. The concentrated flow erosion rates and b-values also depend on the initial moisture content of the topsoil. Depending on Rc, mean concentrated flow erosion rates were 20% to 65% less on initially wet compared to initially air-dry topsoils. The mean value for b was 0.032 for the initially wet, but only 0.017 for the initially air-dry topsoil, indicating that a rock fragment cover is less efficient in reducing concentrated flow erosion rates when the topsoil is initially air-dry than when it is initially wet. The results help explain the data scatter in reported relationships between Rc and interrill–rill erosion rates. They also indicate that a given surface rock fragment cover will offer more protection to wet topsoils than to dry topsoils, which are very common in Mediterranean environments. Event-based water erosion models should incorporate effects of antecedent soil moisture content as well as those of Rc on concentrated flow erosion rates.  相似文献   

4.
Land shortages are forcing more smallholder farmers to cultivate tropical steeplands. Resulting accelerated soil erosion is being countered by the promotion of soil conservation (SC) technologies, such as cross‐slope barriers, which aim to reduce soil loss and preserve land productivity. However, farmer adoption rates tend to be low. This is often attributed to the farmers' conservatism or lack of education. Research in Honduras's steeplands demonstrates that farmers value SC, provided that it promotes agricultural production. Field research from 1995–98, involving farmed test plots on slopes greater than 35 per cent (19 degrees), demonstrates that at least one typical SC technology—live barriers of Vetiveria zizanioides (vetiver grass)—has little or no impact on maize yield. This means that farmers see little benefit from their investment in the SC method. They find that erratic rainfall, pests and diseases and a lack of economic resources are far greater threats to their livelihoods than soil erosion. Consequently, SC has a low priority. Keeping soil in place avoids major off‐farm disbenefits. However, the SC technique tested here made no discernible difference to slope foot sediment yields during the life of this study. In sum, a new approach is needed. Promoting ‘Better Land Husbandry’ strategies, which seek to combine farmers' concerns about productivity with conservationists' concerns about reducing soil erosion—often via cover‐management—seem to be the best way forward. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

5.
Reservoir sedimentation is the most serious threat for water harvesting schemes and hydroelectric power dams in Ethiopia. Designing watershed conservation strategies and management is crucial to reduce the rate of sedimentation. Because different landscape types have varying potentials for enhancing erosion processes, site‐ and process‐specific conservation measures are needed to target an appropriate intervention to the most needed locations. In this study, a GIS‐based distributed soil erosion/deposition model was used to simulate the potential of land‐use and cover (LUC) changes and conservation measures for reducing water induced soil erosion and potential sediment yield for two catchments in northern Ethiopia. LUC change and conservation measures targeted gully and stream buffers, protection of steep slopes and protection of areas with soil loss greater than a given threshold. The results show that land management measures targeted at hot‐spot areas of erosion and gully formation could reduce potential annual sediment yield from catchments by approximately 60% compared with the current losses. The study demonstrates the potential of a GIS‐based LUC‐redesign approach as a tool for optimizing land‐use and management strategies to reduce run‐off and erosion rates in the highlands of northern Ethiopia.  相似文献   

6.
As an extreme manifestation of environmental degradation, karst rock desertification is caused by soil loss and rock exposure. In some areas with serious rocky desertification, there is no soil to be eroded or leaked. The soil loss in these areas superimposes soil erosion and unique subsurface loss by soil leakage through fissures, pipelines, sinkholes, etc., which directly reduce soil resources and accelerate rocky desertification. However, the factors driving soil erosion and subsurface loss by soil leakage are still unclear. Rainfall experiments were conducted on simulated slopes with surface-exposed bedrock and subsurface fissures based on field investigations in a karst rocky desertification area of Guizhou Province, China. Four factors, including rainfall intensity, slope gradient, bedrock exposure rate and subsurface fissure degree, were considered in the experiment. We found that the amount of soil surface erosion and subsurface leakage loss is driven not only by the runoff volume but also by other influential factors. Rainfall intensity is the driving factor determining the amount of surface erosion and subsurface leakage loss of soil and water and the relationship between them. The slope gradient plays a leading role only in subsurface fissure flow leakage loss. The bedrock exposure rate drives the surface soil erosion rate, shows a critical value (30%), and dominates the fissure flow leakage loss rate. Subsurface fissure density plays an important role in the surface loss of soil and water; however, an increase in the subsurface fissure density does not obviously accelerate the subsurface leakage loss of soil and water. Although this result, obtained from laboratory simulations, may differ at the field scale or larger, it could provide a foundation for systematic studies on soil erosion/leakage and insights into the relations between rocky desertification and soil erosion/leakage and their driving factors in karst rocky desertification.  相似文献   

7.
T.W. Lei  Q.W. Zhang  L.J. Yan  J. Zhao  Y.H. Pan 《Geoderma》2008,144(3-4):628-633
Soil erodibility and critical shear stress are two of the most important parameters for physically-based soil erosion modeling. To aid in future soil erosion modeling, a rational method for determining the soil erodibility and critical shear stress of rill erosion under concentrated flow is advanced in this paper. The method suggests that a well-defined rill be used for shear stress estimation while infinite short rill lengths be used for determination of detachment capacity. The derivative of the functional relationship between sediment yield and rill length at the inlet of rill flow, as opposed to average detachment rate of a long rill, was used for the determination of detachment capacity. Soil erodibility and critical shear stress were then regressively estimated with detachment capacity data under different flow regimes. Laboratory data of rill erosion under well defined rill channels from a loess soil was used to estimate the soil erodibility and critical shear stress. The results showed that no significant change in soil erodibility (Kr) was observed for different slope gradients ranging from 5 to 25 while critical shear stress increased slightly with the slope gradient. Soil erodibility of the loess soil was 0.3211 ± 0.001 s m− 1. The soil erodibility and critical shear stress calculations were then compared with data from other resources to verify the feasibility of the method. Data comparison showed that the method advanced is a physically logical and feasible method to calculate the soil erodibility and critical shear stress for physically-based soil erosion models.  相似文献   

8.
Soil conservation is a major concern for catchments affected by forest fires. The lack of vegetation cover and the development of soil water repellency increase the risk of topsoil erosion. This paper evaluates two soil conditioners (a wetting agent and a polyvinyl acetate) for limiting overland flow and erosion in inter‐rill areas. Unburned and burned soil samples were treated with one or both soil conditioners. The effects of these treatments on run‐off, water retention, erosion and plant growth were assessed using laboratory rainfall simulations. Polyvinyl acetate had little impact on water retention but was effective in reducing soil loss. The surfactant had little impact on water run‐off or soil loss but substantially improved water retention and plant biomass production. Application of soil conditioners on post‐fire areas could be a valuable technique in a soil conservation strategy. To maximize their benefits, soil conditioners could be applied with seeding using hydroseeding techniques and be limited to particular areas, such as paths and roadsides. Laboratory results indicate that field testing should also be carried out.  相似文献   

9.
坡沟系统侵蚀产沙特征模拟试验研究   总被引：7，自引：7，他引：7  
坡沟系统介于坡面尺度和流域尺度之间，揭示其侵蚀产沙特征对于认识流域侵蚀产沙及建立流域土壤侵蚀预报模型有重要意义。采用放水冲刷法，通过2.125、3.205、5.250、7.185 L/min 4个不同的放水流量，在4 m长坡面(坡度为20°)和3 m长沟坡(坡度为50°)组成的坡沟系统上，对坡沟系统的侵蚀产沙特征进行了模拟试验研究。结果表明：对试验条件下的每一个放水流量来说，坡沟系统内的侵蚀产沙垂直分布都呈双峰曲线，侵蚀量的变化均呈现出沿坡沟系统从上到下先减小后增大再减小的趋势。沟坡部分的侵蚀量占全坡侵蚀量的百分比由放水流量2.125 L/min时的38.13％，增加到放水流量7.185 L/min时的56.01％。对于黄土高原水土流失治理，单纯治坡或治沟均不能明显减少土壤流失量，采取坡、沟兼治才是有效减少土壤流失的有效措施。  相似文献   

10.
Early drilling of autumn‐planted cereals is strongly advised in UK government publications targeted at farmers, in part as a measure to combat soil erosion by water. However, in years when rainfall is heavy in early autumn, this strategy is ineffective. Late drilling of autumn‐planted cereals also increases the risk of erosion, but for a different reason: crop cover develops more slowly in cooler weather, resulting in a longer exposure of nearly bare ground. The crucial factor affecting both strategies is the timing of autumn and early winter rainfall. We discuss a conceptual model based on the notion of a ‘window of opportunity’ for erosion, comprising the relationship between drilling date, date of attainment of a sufficiently protective crop cover and the timing of rainfall; variations are presented for different weather conditions and management choices. Of these three factors, only the date of drilling can be chosen by the farmer. The date of attaining a sufficiently protective crop cover can only be predicted approximately. The timing of rainfall cannot be predicted. Thus, erosion control advice to farmers, which is based on choice of date of drilling to minimize erosion during the ‘window of opportunity’, is both difficult to formulate and likely to be ineffective. Sites at risk of erosion need to have better thought‐out mitigation measures in place, rather than relying on a fortuitous temporal pattern of autumn and winter rainfall to minimize the risk of erosion.  相似文献   

11.
Abstract

Direct fertilization of peanuts (Arachis hypogaeaL.) with P and K has generally shown few yield responses, resulting in only limited information concerning critical soil‐test levels of P and K. The purpose of the experiments in this report was to determine the critical soil‐test levels of P and K for runner peanuts using the double‐acid extraction procedure. Fertilizer experiments were conducted on farmers’ fields from 1973 to 1986. Site selection was based on soil test data that indicated “medium”; or “low”; levels of available P or K but “high”; in Ca and Mg. Phosphorus and potassium were applied together at all sites at rates of 20 and 74 kg/ha, respectively, as concentrated superphosphate and potassium chloride.

There were yield increases to fertilizer in 6 of the 39 experiments. Soil‐test P for these six ranged between 4 and 53 kg/ha; soil‐test K ranged between 10 and 31 kg/ha. Delineating the yield effect into their P and K components with the aid of multiple regressions of yield on soil test values showed that yield increases were due to the K component of the fertilizer. The critical soil‐test K value was calculated to be 37 kg/ha. Sound mature kernels (SMK) were generally unaffected by fertilizer.  相似文献   

12.
The effectiveness of a surface cover material (e.g. geotextiles, rock fragments, mulches, vegetation) in reducing runoff and soil erosion rates is often only assessed by the fraction of the soil surface covered. However, there are indications that soil structure has important effects on the runoff and erosion-reducing effectiveness of the cover materials. This study investigates the impact of soil pre-treatment (i.e. fine tilth versus sealed soil surface) on the effectiveness of biological geotextiles in increasing infiltration rates and in reducing runoff and interrill erosion rates on a medium and steep slope gradient. Rainfall was simulated during 60 min with an intensity of 67 mm h−1 on an interrill erosion plot having two slope gradients (i.e. 15 and 45%) and filled with an erodible sandy loam. Five biological and three simulated geotextiles with different cover percentage were tested on two simulated initial soil conditions (i.e. fine tilth and sealed soil surface). Final infiltration rates on a sealed soil surface (7.5–18.5 mm h−1) are observed after ca. 10 min of rainfall compared to ca. 50 min of rainfall on an initial seedbed (16.4–56.7 mm h−1). On the two tested slope gradients, significantly (α = 0.05) smaller runoff coefficients (RC) are observed on an initial seedbed (8.2% < RC < 59.8%) compared to a sealed soil surface (75.7% < RC < 87.0%). On an initial seedbed, decreasing RC are observed with an increasing simulated geotextile cover. However, on an initial sealed soil surface no significant effect of simulated geotextile cover on RC is observed. On a 15% slope gradient, calculated b-values from the mulch factor equation equalled 0.054 for an initial fine tilth and 0.022 for a sealed soil surface, indicating a higher effectiveness of geotextiles in reducing interrill erosion on a fine tilth compared to a sealed soil surface. Therefore, this study demonstrates the importance of applying geotextiles on the soil surface before the surface tilth is sealed due to rainfall. The effect of soil structure on the effectiveness of a surface cover in reducing runoff and interrill erosion rates, as indicated by the results of this study, needs to be incorporated in soil erosion prediction models.  相似文献   

13.
Anionic polyacrylamide (PAM) has the potential to reduce soil erosion through soil conditioning. However, a comprehensive study about its effectiveness especially when applied combined with other amendments have rarely been conducted in the tropical highland climatic conditions, such as in Ethiopia. The study assessed the effectiveness of PAM (P = 40 kg ha?1) alone or integrated with other soil amendments such as gypsum (G = 5 t ha?1), lime (L = 4 t ha?1) and biochar (B = 8 t ha?1) on runoff and soil loss at Aba Gerima watershed in the Upper Blue Nile basin, northwest of Ethiopia, where there is high erosion-caused soil degradation. A total of 79 daily runoff and sediment data were collected from eight runoff plots (1.3m × 4m) with three replications planted with teff (Eragrostis tef) crop for two years (2018 & 2019) rainy seasons. Associated changes in soil physicochemical properties and crop growth parameters were investigated. Treatments reduced seasonal runoff by 12–39% and soil loss by 13–53%. The highest reduction in runoff was observed from P + B and PAM treatments while the highest reduction in soil loss was observed from that of P + L and PAM treatments. Integrating PAM with other amendments improved soil structural stability, moisture content, soil pH (P + L) and organic matter (P + B), leading to favorable environment for crop growth (biomass yield) and reduced runoff and soil erosion. Unlike PAM, biochar and lime amendments may need more time after application to be more effective. Hence continuing the field experiment and studying physico-chemical mechanisms for extended period will better elucidate their single or combined effectiveness over time.  相似文献   

14.
The caesium-137 technique for investigating rates and patterns of soil loss has now been successfully applied in a wide range of environments. However, some uncertainty still surrounds the ability of the technique to provide quantitative estimates of rates of erosion. The wide range of calibration relationships that have been employed by individual workers to derive erosion rates from estimates of the amount of 137Cs (caesium-137) lost from the soil profile, emphasize the uncertainty involved. Existing calibration procedures, involving both empirical relationships and theoretical models and accounting procedures are reviewed and their limitations and inconsistencies are identified. Further research is required in this important area, if the clear potential of the caesium-137 technique is to be fully realized.  相似文献   

15.
为探讨不同雨型下的植物措施对棕壤坡面土壤侵蚀特征的影响,利用k-均值聚类方法将2018—2019年山东省泰安市下港坡面径流场16次侵蚀性降雨进行分类,结合径流场产流、产沙等监测数据,分析了不同雨型对4种植被措施下坡面土壤侵蚀的影响。结果表明：(1)以降雨历时、降雨量和平均雨强为特征指标,侵蚀性降雨可分为A类(长历时、大雨量、大雨强)、B类(中历时、中雨量、中雨强)和C类(短历时、小雨量、小雨强)3种雨型。(2)与种植玉米相比,A、B雨型下,减流量均呈现板栗花生间作>苹果树>李子树的趋势。在土壤流失量方面：A雨型下,与李子树相比,减沙量呈现板栗花生间作>苹果树>玉米的趋势;B雨型下,与玉米相比,板栗花生间作的减沙率为84.2%,李子树的减沙率为31.2%,苹果树的减沙率为85.1%;C雨型下,减沙量呈现苹果树>李子树>板栗花生间作的趋势。(3)种植玉米的坡耕地土壤侵蚀情况最为严重,平均每年的土壤流失量为18.04 t/hm2;与之相比,板栗花生间作可降低79.57%的土壤侵蚀率,苹果树和李子树可分别降低73.36%,18.55%的...  相似文献   

16.
间歇降雨对铁尾砂重构坡面侵蚀水动力学特性的影响   总被引：1，自引：1，他引：0  
黄土高原夏季降雨集中且多暴雨,铁尾矿砂自身结构松散,堆存坡度大,雨季通常遭受多次暴雨侵蚀,严重限制植被恢复。为有效减少铁尾矿的水土流失,促进生态恢复,在干排铁尾矿砂中添加不同比例土壤和菌糠,形成6种重构坡面:松散铁尾矿砂(LT),结壳铁尾矿砂(CT),铁尾矿砂与菌糠混合物(TM),铁尾矿砂、菌糠和土壤混合物(TSM),铁尾矿砂和土壤混合物(TS),纯土(S)。采用室内人工模拟降雨技术,研究重构坡面在间歇性降雨下的侵蚀特征和水动力因素。结果表明:1)随降雨场次增加,6种坡面的产流率均持续增大,而产沙率表现出明显的分异:LT、CT和TS产沙率持续增大,表现为高产沙型,TS、TSM和S产沙率整体上是先增加后减少,表现为低产沙型;2)随降雨场次增加,6种坡面侵蚀形态也出现分异,可分为2类:LT和CT和TS坡面侵蚀形态严重,细沟发展快,演化为宽深比较小的细沟;TM和TSM和S坡面侵蚀形态轻微,细沟发展缓慢,S坡面演化为宽深比较大的细沟,TM和TSM坡面细沟很少,多为均匀分布的菌糠小坑穴。据此表征坡面侵蚀微地形变化的沟壑面积和地形起伏度,随降雨场次增加持续增大;沟壑密度则随降雨场次先急剧增加,随后由于沟壑形态差异,部分坡面减少;3)6种坡面的坡面流流型均为层流,流态大多为急流;随降雨场次增加,流速、水流功率整体表现为增大的趋势,径流剪切力无明显趋势,阻力系数、曼宁粗糙系数表现出减小的趋势;除径流剪切力,不同降雨场次间水动力学特征差异显著(P0.05)。6种坡面侵蚀产流产沙可用对数、线性或幂函数较好地模拟。纯尾矿砂坡面侵蚀最为严重,坡面覆土具有明显的减流效果,但添加菌糠的减沙效果最好,因此对于土源缺乏的铁尾矿砂复垦区,同时添加菌糠和土壤可以有效减少侵蚀,易于植被修复。  相似文献   

17.
Meadow degradation provides a major indication of increased soil erosion in alpine regions. Serious soil erosion is observed during the spring in particular because soil thawing coincides with the period of snowmelt and the meadow coverage is very low at this time. Studies relating to soil erosion caused by spring meltwater are, however, limited and controversial. Therefore, a field experimental study was conducted in a typical meadow in the Binggou watershed on the northern edge of the Tibetan Plateau to assess the impact of multiple factors on spring meltwater erosion on an alpine meadow slope. The multiple factors included three flow rates (1, 2, and 3 L/min), four slope gradients (10°, 15°, 20°, and 25°), and three underlying surface conditions (meadow, disturbed meadow, and alluvial soil). An equal volume of concentrated meltwater flow was used in all experiments. The results showed that rapid melting at a high flow rate could accelerate soil erosion; as the flow rate increased from 1 to 3 L/min, the total surface runoff increased by a factor of 0.7 and the total sediment yield increased by more than 6-fold. The influence of the slope gradient on the amount of runoff was positively linear and the influence was relatively low; when the slope increased from 10° to 25°, the total runoff only increased by 16%. However, the slope gradient had a strong impact on soil erosion. The total sediment yield doubled when the slope increased from 10° to 20° and then slightly decreased at 25°. The meadow could effectively reduce soil erosion, although when the meadow was disturbed, the total runoff increased by 60% and the sediment yield by a factor of 1.5. The total runoff from the alluvial soil doubled in comparison to the meadow, while the sediment yield increased nearly 7-fold. The findings of this study could be helpful to understand the characteristics and impact of multiple controlling factors of spring meltwater erosion. It also aims to provide a scientific basis for an improved management of alpine meadows as well as water and soil conservation activities in high-altitude cold regions.  相似文献   

18.
The revised universal soil loss equation (RUSLE), the sediment delivery distributed (SEDD) model, and ArcView GIS were used to estimate the impacts of no-till practice on soil erosion and sediment yield in Pataha Creek Watershed, a typical dryland agricultural watershed in southeastern Washington. The results showed that the average cell soil loss decreased from 11.09 to 3.10 t/ha yr for the whole watershed and from 17.67 to 3.89 t/ha yr for the croplands under the no-till scenario. Likewise, the average cell sediment yield decreased from 4.71 to 1.49 t/ha yr for the entire watershed and from 7.11 to 1.55 t/ha yr for the croplands under no-till practices. The major reason why no-till practice can significantly reduce the soil erosion and sediment yield is that it prevents rill generation which through rill erosion ultimately contributes up to 90% of the soil erosion in the Inland Pacific Northwest region.  相似文献   

19.
Crops are the most important ground cover on slope farmland and have a significant impact on the soil erosion. But soil erosion on slope farmland is also affected by many other factors, such as topography and rainfall. In order to explore the effect of crop growth on soil erosion on different slope gradient of slope farmland, and analyze the interaction of crop growth and slope gradient on soil erosion, this study used artificial simulated rainfall to observe the runoff rates and soil loss amounts under different slope gradients for maize, soybeans, and winter wheat in different growth stages. Results showed that crops and slope gradient both significantly affected production and development of slope runoff. Compared with bare land, mean runoff rate on slopes was reduced by 24%, 32%, and 94% respectively, and sediment yield was decreased by 44%, 55%, and 99% respectively on maize, soybean, and winter wheat fields. Inhibitory effects of crops on slope runoff rate and sediment yield were enhanced with crop growth and decreased with increasing slope gradient. Crop growth and coverage could offset the impact of increasing slope gradient on runoff and sediment to some extent and reduced water and soil loss on slopes. Sediment yield was produced largely when the slope gradient was greater than 10 degrees on maize and soybean fields, but soil erosion was effectively inhibited when the slope gradient was less than 15 degrees on winter wheat fields. Crop planting can effectively reduce the impact of slope gradient on soil erosion, especially during the flourishing period of crop growth.  相似文献   

20.
Carbon distribution and losses: erosion and deposition effects   总被引：21，自引：0，他引：21  
Because of concerns about the eventual impact of atmospheric CO2 accumulations, there is growing interest in reducing net CO2 emissions from soil and increasing C storage in soil. This review presents a framework to assess soil erosion and deposition processes on the distribution and loss of C in soils. The physical processes of erosion and deposition affect soil C distribution in two main ways and should be considered when evaluating the impact of agriculture on C storage. First, these processes redistribute considerable amounts of soil C, within a toposequence or a field, or to a distant site. Accurate estimates of soil redistribution in the landscape or field are needed to quantify the relative magnitude of soil lost by erosion and accumulated by deposition. Secondly, erosion and deposition drastically alter the biological process of C mineralization in soil landscapes. Whereas erosion and deposition only redistribute soil and organic C, mineralization results in a net loss of C from the soil system to the atmosphere. Little is known about the magnitude of organic C losses by mineralization and those due to erosion, but the limited data available suggest that mineralization predominates in the first years after the initial cultivation of the soil, and that erosion becomes a major factor in later years. Soils in depositional sites usually contain a larger proportion of the total organic C in labile fractions of soil C because this material can be easily transported. If the accumulation of soil in depositional areas is extensive, the net result of the burial (and subsequent reduction in decomposition) of this active soil organic matter would be increased C storage. Soil erosion is the most widespread form of soil degradation. At regional or global levels its greatest impact on C storage may be in affecting soil productivity. Erosion usually results in decreased primary productivity, which in turn adversely affects C storage in soil because of the reduced quantity of organic C returned to the soil as plant residues. Thus the use of management practices that prevent or reduce soil erosion may be the best strategy to maintain, or possibly increase, the worlds soil C storage.  相似文献   

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