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1.
Rates of sheet and rill erosion in Germany — A meta-analysis   总被引：2，自引：0，他引：2  
K. Auerswald  P. Fiener  R. Dikau   《Geomorphology》2009,111(3-4):182-193
Knowledge of erosion rates under real conditions is of great concern regarding sustainability of landuse and off-site effects on water bodies and settlements. Experimentally derived rates of sheet and rill erosion are often biased by experimental settings, which deviate considerably from typical landuse, by short measuring periods and by small spatial extensions, which do not account for the pronounced spatio-temporal variability of erosion events. We compiled data from 27 studies covering 1076 plot years to account for this variability. Modelling was used to correct for deficiencies in the experimental settings, which overrepresented arable land and used steeper and shorter slopes as well as higher erosivity than typically found in reality. For example, the average slope gradient was 5.9° for all arable plot experiments while it is only 2.6° on total arable land in Germany. The expected soil loss by sheet and rill erosion in Germany after taking real slopes, landuse and erosivity into account averaged 2.7 t ha− 1 yr− 1. Annual crops contributed the largest proportion (90%) but hops despite its negligible contribution to landuse (0.06%) still contribute 1.0% due to its extraordinary rapid erosion, which was even faster than the measured bare fallow soil loss standardized to otherwise identical conditions. Bare fallow soil loss, which is often used as baseline, was 80 t ha− 1 yr− 1 when standardized to 5.1° slope gradient, 200 m flow path length, and average German erosivity.  相似文献   

2.
This study was conducted to quantify agricultural land degradation in the Ruba Gered watershed, Ethiopia. The watershed was divided into 12 land mapping units (LMU) after superimposing maps of soil, slope, land use/cover, and elevation. Subsequently, cultivated land was delineated to assess degradation types and severity based on standard approaches. Sheet erosion was estimated using the revised universal soil loss equation. Composite soil samples were collected from each LMU to quantify key soil nutrients (OM, total nitrogen, available phosphorus, and available potassium) lost by sheet erosion. The annual average soil loss due to sheet erosion was estimated to be 17.4 t ha?1 yr?1, with average annual nutrient losses estimated as 246.5 kg ha?1 organic matter, 12.4 kg ha?1 total nitrogen, 0.1 kg ha?1 available phosphorus, and 1.6 kg ha?1 available potassium. The study revealed that substantial quantities of soil and nutrients are lost every year in the study area due to severe sheet erosion. This amount of nutrient loss severely degrades soil and reduces soil fertility.  相似文献   

3.
This paper reports soil losses from 15 erosion plots in the Middle Hills, Nepal, for the 1992 and 1993 monsoon and pre-monsoon seasons. In total, 912 rainfall events were monitored. Land cover varied from grassland and relatively undisturbed mixed broadleaf forest, to degraded Sal forest and bare ground. Soil losses ranged from less than 0.1 t ha-1 yr-1 for grassland and undisturbed forest plots, to 3–10 t ha-1 yr-1 for Sal forest in various states of degradation, and over 15 t ha-1 yr-1 for the bare sites. These results are broadly consistent with those reported in other parts of the Himalayan Middle Hills. Soil loss values could be explained by variations in runoff amounts and rainfall intensity, as well as by the nature of the land cover. Ground and low shrub cover was more important than canopy cover in protecting the forest soils. Human activity has unquestionably led to accelerated rates of soil loss but the degree of acceleration depends on the nature of the human activity and especially the care with which the land is managed. [Key words: soil loss, land use, Nepal, land degradation.]  相似文献   

4.
A comprehensive methodology that integrates the Universal Soil Loss Equation (USLE) and Geographic Information System (GIS) was adopted in this study to determine the soil erosion and sediment yield of the Irga watershed in Jharkhand, India. Based on the availability and applicability of data in a GIS-environment, the original equations for the model input parameters were, however, modified by researchers. In the present study, a power-law equation was generated to estimate the rainfall erosivity (R) factor, and the Nash-Sutcliffe model efficiency coefficient used to determine the accuracy of the modified R factor. Average annual soil erosion in the Irga watershed is estimated to be 4.3 t ha?1 yr?1. On the other hand, average annual sediment yield of the watershed, estimated using the sediment delivery ratio, was found to be 1.2 t ha?1 yr?1. Low sediment yield indicates that most of the eroded soil was deposited within the watershed.  相似文献   

5.
The landscape evolution in Neogene intramontane basins is a result of the interaction of climatic, lithologic, and tectonic factors. When sedimentation ceases and a basin enters an erosional stage, estimating erosion rates across the entire basin can offer a good view of landscape evolution. In this work, the erosion rates in the Guadix–Baza basin have been calculated based on a volumetric estimate of sediment loss by river erosion since the Late Pleistocene. To do so, the distribution of a glacis surface at ca. 43 kyr, characterised by a calcrete layer that caps the basin infilling, has been reconstructed. To support this age, new radiometric data of the glacis are presented. The volume of sediment loss by water erosion has been calculated for the entire basin by comparing the reconstructed geomorphic surface and the present-day topography. The resulting erosion rates vary between 4.28 and 6.57 m3 ha− 1 yr− 1, and are the consequence of the interaction of climatic, lithologic, topographic, and tectonic factors. Individual erosion rates for the Guadix and Baza sub-basins (11.80 m3 ha− 1 yr− 1 and 1.77 m3 ha− 1 yr− 1 respectively) suggest different stages of drainage pattern evolution in the two sub-basins. We attribute the lower values obtained in the Baza sub-basin to the down-throw of this sub-basin caused by very recent activity along the Baza fault.  相似文献   

6.
In this article we evaluate the potential use of Cladonia foliacea tissue N content, C:N ratio, and phosphomonoesterase (PME) activity as biomarkers of N deposition by means of a field experiment. In order to do this, we continuously added NH4NO3 to a semi-arid shrubland at four rates: 0, 10, 20 and 50 kg N ha−1 yr−1 starting in October 2007. Tissue N content and C:N ratios, considered as N stress indicators, significantly increased and decreased, respectively, after 1.5 years. The response found suggests N saturation above 20 kg N ha−1 yr−1. After 2.5 years, extracellular PME activity increased with 20 kg N ha−1 yr−1 and this was attributed to an induced nutritional (N to P) imbalance. Above this threshold, PME significantly decreased as a consequence of the physiological stress caused by extra N. Effects on PME were dependent on the soil properties (pH and Ca and Mg availability) experienced by C. foliacea. PME response suggests a critical load of ∼26.4 kg N ha−1 yr−1 (20 kg N ha−1 yr−1 + background) for this lichen. Further tissue chemistry and PME evaluations in C. foliacea and soil surveys conducted along wide N deposition gradients will confirm the potential use of this species as a biomonitor of N pollution and the importance of soil properties on its ability to respond to atmospheric reactive N.  相似文献   

7.
The northern coastal part of Korinthia prefecture can be characterized as an agrotourism center that has grown and urbanized rapidly. The area is formed of recent unconsolidated material consisting of sands, pebbles, breccias and fine clay to silty sand deposits. These deposits host the main aquifer system of the area, which depends on groundwater as a water resource. Groundwater is the main source for irrigation in the area. A total water volume of 29.2×106–34.3×106 m3 yr−1 was estimated to recharge the aquifer system from direct infiltration of rainfall, streambed infiltration, irrigation return, artificial recharge via flood irrigation and lateral subsurface inflows. The present annual abstraction ranges between 39.2×106 and 44.6×106 m3 yr−1. Groundwater abstraction in dry years exceeds renewable freshwater resources by more than 38%. Approximately 79% of the total abstraction is consumed for agriculture supply. Water balance in the coastal aquifer system is in disequilibrium; a deficit, which ranges from 4.9×106 to 15.4×106 m3 yr−1 exists. The safe yield of the coastal aquifer system has been estimated at 37.1×106 m3 yr−1 for normal hydrological year and 32×106 m3 yr−1 for severely dry hydrological year. The total abstraction is greater than the recharge and the safe yield of the aquifer. The aquifer system has shown signs of depletion, seawater intrusion and quality contamination. The integrated water resources management, securing water in the future, should include measures that augment groundwater budget in the coastal aquifer of the study area.  相似文献   

8.
A new and simple method is developed to efficiently quantify erosion and deposition rates based on stock unearthing measurements. This is applicable to spatial scales ranging from plot to hillslopes, and to time scales ranging from single hydrologic events to centennial scales. The method is applied to a plot area on vineyard hillslopes in Burgundy (Monthélie, France), with measurement of 4328 vine plants. A sediment budget established at the plot scale shows a mean soil lowering of 3.44 ± 1 cm over 20 years, involving a minimal erosion rate of 1.7 ± 0.5 mm yr− 1. Locally, erosion rates can reach up to 8.2 ± 0.5 mm yr− 1.This approach allows the sediment redistribution to be mapped and analyzed at 1-m resolution. It provides novel insights into the characterization of erosion patterns on pluri-decennial scales and into the analysis of spatial distribution of erosion processes on cultivated hillslopes.  相似文献   

9.
Although in the last decades gully erosion has been a thriving research field, few studies have specifically addressed the contribution and location of sidewall erosion processes in gullies. In this paper, sidewall erosion in some large gullies in a Mediterranean area (Anoia-Penedès, NE Spain) is mapped and assessed for two time intervals (1975–1995 and 1995–2002), using detailed digital elevation models derived from aerial photographs at a scale of 1:5000 to 1:7000. Logistic regression analysis is applied to compute the probability of occurrence of gully sidewall erosion from terrain variables. The results confirm the complex nature of sidewall processes, whose intensity is most probably related to rainfall characteristics. Prolonged wet soil conditions in the period 1995–2002, together with the large and high-intensity rainfall of an extreme event occurred on 10th June 2000, help to explain the different sediment production rates: 16±0.4 Mg ha−1 year−1 in 1975–1995 and 83±6.3 Mg ha−1 year−1 in 1995–2002. The logistic regression analysis revealed that gully-wall slope angle was the main factor controlling gully sidewall failure. In gully walls with high slope angles, tension crack development is the main process promoting wall collapse. The application of the logistic regression model showed a high overall accuracy (87%) but over 50% of commission and omission errors for the class of interest (sidewall erosion), in agreement with the variance explained by the model.  相似文献   

10.
Using the USPED (Unit Stream Power Erosion Deposition) model, three land use scenarios were analysed for an Italian small catchment (15 km2) of high landscape value. The upper Orme stream catchment, located in the Chianti area, 30 km south of Florence, has a long historical agriculture record. Information on land use and soil conservation practices date back to 1821, hence offering an opportunity to model impacts of land use change on erosion and deposition. For this study, a procedure that takes into account soil conservation practices and potential sediment storage is proposed. The approach was to calculate and model the flow accumulation considering rural and logging roads, location of urban areas, drainage ditches, streams, gullies and permanent sediment sinks. This calculation attempts to assess the spatial variability, especially the impact of support practices (P factor). Weather data from 1980–2003 were taken into account to calculate the R factor. However, to consider the intense pluviometric conditions in terms of the erosivity factor, the 0.75th quantile was used, while the lowest erosivity was modelled using the 0.25th quantile. Results of the USPED model simulation show that in 1821 the mean annual net erosion for the watershed was 2.8 Mg ha− 1 y− 1; in 1954 it was 4.2 Mg ha− 1 y− 1; and in 2004 it was 5.3 Mg ha− 1 y− 1. Conservation practices can reduce erosion processes by ≥ 20 Mg ha− 1 y− 1 when the 1821 practices are introduced in the present management. On the other hand, if the support practices are not considered in the model, soil erosion risk is overestimated. Field observation for the present-day simulation confirmed that erosion and associated sediment deposition predicted by the model depend, as expected, on geomorphology and land use. The model shows limitations that are mainly due to the input data. A high resolution DEM is essential for the delineation of reliable topographic potential to predict erosion and deposition especially in vineyards.  相似文献   

11.
Gully erosion is an important environmental hazard in the black soil region of northeastern China. It is a primary sediment source in the region which needs appropriate soil conservation practices. Gully incision in rolling hills typical of this region was monitored using real-time kinematic GPS to assess the rates of gully development and the resultant sediment production. From 2002 to 2005, gully heads in the study area retreated between 15.4 and 33.5 m, giving an average retreat rate of 8.4 m yr− 1. Field measurements showed that total sediment production due to gully erosion during the three years ranged between 257 and 1854 m3 yr− 1, which is equivalent to 326 to 2355 t yr− 1, with gully-head retreat accounting for 0 to 21.7% (4.4% in average). The sediment delivery ratio was especially high during the summer rainy season (56% in average). Sediment production by ephemeral gullies and permanent gullies was 1.5 times greater than that from surface erosion. Gully heads retreated faster in the spring freeze–thaw period than in the summer. The stage of gully development could be identified based on short-term changes in the gully erosion rate.  相似文献   

12.
耕作方式对紫色水稻土活性有机碳的影响   总被引：1，自引：0，他引：1  
吴艳  郝庆菊  江长胜 《地理科学》2011,31(4):485-489
以位于西南大学试验农场的紫色土长期免耕试验田为研究对象,探讨不同耕作方式-冬水田平作(DP)、水旱轮作(SH)、垄作免耕(LM)、厢作免耕(XM)和垄作翻耕(LF)对紫色水稻土总有机碳、活性有机碳及稳态碳的影响。结果表明,在0~60 cm的土壤深度内,不同耕作方式下总有机碳的平均含量为LM(22.74 g/kg)>DP(14.57 g/kg)>XM(13.73 g/kg)>LF(13.10 g/kg)>SH(11.92 g/kg);活性有机碳的平均含量为DP(3.67 g/kg)>LF(3.49 g/kg)>LM(3.28 g/kg)>XM(3.17 g/kg)>SH(2.69 g/kg);稳态碳占土壤总有机碳的百分比为LM (85%)>SH (78%)>XM (77%)>LF (75%)>DP (74%)。长期垄作免耕具有明显的碳截存效应和良好的固碳能力。  相似文献   

13.
Preserving soils is a major challenge in ensuring sustainable agriculture for the future. Soil erosion by water is a critical issue in the Mediterranean regions and usually occurs when high-erosive precipitation is in temporal association with poor vegetation cover and density. Modelling soil erosion risks over large spatial scales suffers from the scarcity of accurate information on land cover, rainfall erosivity and their intra-annual dynamics. We estimated the soil erosion risk on arable land in a Mediterranean area (Grosseto Province, southern Tuscany, Italy) and investigated its potential reduction as a response to the change in intra-annual distribution of land cover due to the increase of perennial forage crops. A GIS-based (R)USLE model was employed and a scenario analysis was performed by setting criteria for raising the performance of perennial forage crops. Statistical data on agricultural crops provided an insight into current intra-annual land cover dynamics. Rainfall erosivity was computed on the basis of 22-year hourly precipitation data. The model was used to: i) quantify the potential soil losses of arable land in the study area, ii) identify those areas highly affected by erosion risks iii) explore the potential for soil conservation of perennial crops, thereby enabling appropriate preventive measures to be identified. The erosion rates, averaged over an area of about 140’000 ha, are estimated to 33.42 Mg ha−1 y−1. More than 59% of the study area was subjected to soil losses higher than 11 Mg ha−1 y−1 (from moderate to severe erosion) and the highest rates are estimated for steep inland areas. Arable land with severe soil erosion rates (higher than 33 Mg ha−1 y−1) represent about 35% of the whole study area. The risk of soil loss by water erosion in the study area is estimated to be reduced on average by 36% if perennial crops are increased in terms of 35% of the total arable land. The soil erosion data produced compared well with the published local and regional data. This study thus provides useful preliminary information for landscape planning authorities and can be used as a decision support tool in quantifying the implications of management policies.  相似文献   

14.
小麦玉米田耕作模式的防风蚀效果   总被引：2，自引：0，他引：2  
通过风洞实验，在5个风速下对6种耕作方式下农田土壤风蚀速率、0~20 cm风沙流结构进行了模拟研究。结果表明：保护性耕作土壤风蚀速率较传统耕作平均降低20%~40%；保护性耕作和传统耕作条件下土壤风蚀速率均随风速的增大呈幂函数递增，但在传统耕作条件下递增较快；风速14 m·s-1是荒漠绿洲农田土壤风蚀加剧转折点，当风速>14 m·s-1时保护性耕作下风蚀速率较传统耕作明显降低；0~20 cm内，传统耕作和保护性耕作下输沙率与高度分别呈线性和指数关系，保护性耕作下0~4 cm输沙量和输沙量百分比（Q0~4/Q0~20）均低于传统耕作。  相似文献   

15.
Low‐energy gamma ray spectroscopy has been employed to estimate floodplain sedimentation rates using measurements of 210Pb in floodplain alluvium. The utility of the technique is assessed through the analysis of excess (unsupported) 210Pb profiles in three sediment cores taken from the floodplain of the Labasa River on Vanua Levu in northern Fiji. A low‐energy germanium spectrometer (LEGe) was used for the nondestructive determination of excess 210Pb in a region cultivated intensively with sugarcane. Measured average historical (c. 25 years) vertical accretion rates are between 2.2 and 4.4 cm yr?1. The findings are broadly comparable with published sedimentation rates from analyses of radionuclide profiles elsewhere in the tropical South Pacific Islands, but the rates are higher than those measured previously at the same Labasa River sites using 137Cs profiles. Accelerated soil erosion owing to cane burning and land tillage seems to be largely responsible for sediment production, although flood‐related effects such as channel accretion by coarse bedload and the emplacement of large organic debris also influence floodplain sedimentation. However, application of the 210Pb technique in Fiji (and perhaps neighbouring island countries) is found to have serious drawbacks compared to the more robust 137Cs method, owing principally to the low 210Pb concentrations in the sandy alluvial sediment tested.  相似文献   

16.
Soil respiration is essential for the understanding of carbon sequestration of forest plantations. Soil respiration of poplar plantations at three developmental stages was investigated in 2007 and 2008. The results showed that mean soil respiration rate was 5.74, 5.10 and 4.71 μmol CO2 m−2 s−1 for stands of 2-, 7- and 12-year-old, respectively, during the growing season. Soil temperature decreased with increasing plantation age and canopy cover. As plantation matured, fine root biomass also declined. Multiple regression analysis suggested that soil temperature in the upper layer could explain 73-77% of the variation in soil respiration and fine root biomass in the upper layer could explain further 5-8%. The seasonal dynamics of soil respiration was mainly controlled by soil temperature rhythm and fine root growth since soil water availability remained adequate due to monthly irrigation. Spatial variability of soil respiration varied considerably among three age classes, with the coefficient of variation of 28.8%, 22.4% and 19.6% for stands of 2-, 7- and 12-year-old, respectively. The results highlight the importance of the development stage in soil carbon budget over a rotation, since both temporal and spatial variation in soil respiration displayed significant differences at different developmental stages.  相似文献   

17.
The pattern of carbon (C) allocation among the different pools is an important ecosystem structural feature, which can be modified as a result of changes in environmental conditions that can occur gradually (e.g., climatic change) or abruptly (e.g., management practices). This study quantified the C pools of plant biomass, litter and soil in an arid shrubland in Chile, comparing the natural condition (moderately disturbed by grazing) vs. the afforested condition (two-year-old plantation with Acacia saligna (Labill.) H.L. Wendl.), each represented by a 60 ha plot. To estimate plant biomass, allometric functions were constructed for the four dominant woody species, based on the volume according to their shape, which showed high correlation (R2 > 0.73). The soil was the largest C pool in both natural and afforested conditions (89% and 94%, respectively) and was significantly lower in the afforested than natural condition at all five soil depths. The natural condition had in total 36.5 ton (t) C ha−1 compared to 21.1 t C ha−1 in the afforested condition, mainly due to C loss during soil preparation, prior to plantation of A. saligna. These measurements serve as an important baseline to assess long-term effects of afforestation on ecosystem C pools.  相似文献   

18.
黑土侵蚀速率及其对土壤质量的影响   总被引：35，自引：3，他引：32  
阎百兴  汤洁 《地理研究》2005,24(4):499-506
利用137Cs示踪法,研究了东北黑土耕作土壤的流失厚度和速率,探讨了水土流失对土壤机械组成、有机质、土壤水分、容重及其N、P含量的影响。结果表明:研究区侵蚀坡面137Cs的分布深度在0～25cm,137Cs的活度在1246.05±85.90～1499.45±101.73Bq/m2,侵蚀厚度可达0.316～0.433mm/a,侵蚀强度3033.6～3940.3t/km2·a,已属于中度侵蚀水平。水土流失造成土壤质地粗化,从坡顶向坡底,耕层土壤有机质增加、容重变化不大,含水量增加,土壤养分的“贫化”现象明显。  相似文献   

19.
Paleolimnological techniques for assessing recent drainage basin disturbance are evaluated in three Moroccan lakes with catchments contrasted in terms of land-use and vegetation. Rates of sediment accumulation in the two lakes with agricultural catchments were relatively high (>1.6 cm yr-1) in the most recent past. Dilution effects prevented core dating by the 210Pb method alone and post-1953 chronologies were constructed by combining 210Pb and 137Cs data. The recent sediment accumulation rate at the currently least disturbed site, where natural Cedrus forest is still abundant, was relatively low (<0.4 cm yr-1) but has increased since the mid-19th century.Magnetic, geochemical, pollen, and diatom studies of all three lake sediment cores linked with modern field survey data show that soil erosion in the most vegetationally disturbed catchment (Dayat-er-Roumi) has been high throughout the recent past and that intensity peaks are probably associated with wetland drainage operations beginning in the 1940's. At the partially forested site (Dayat Affougah), pre-1950's woodland clearance and other land-use changes are the likely cause of past major soil erosion episodes. The site currently dominated by natural Cedrus forest (Lac Azigza) shows only minor disturbance during the past c. 150 years although a major soil erosion episode occrred in the 17th century.Paleolimnological analysis has clearly demonstrated that major landscape change has occurred at all three sites. However, only at the two sites with catchment cultivation do previously accelerated soil erosion and lake sediment accumulation rates persist to the present. Information essential for formulation of appropriate management plans is presented and the importance of paleolimnology in assessing man-induced lake-catchment disturbance is stressed.  相似文献   

20.
Abstract

Erosion rates in residual limestone soils in a humid climate were measured for 10 years at one site, and for 4 years at another site, using erosion pins. Erosion pins were placed in gully floors and on convex divides between adjacent gullies, on abandoned land where vegetation had been removed. We measured an average erosion rate of 20 mm yr?1 over 10 years at one site and only 5 mm yr?1 over 4 years at another site where chert gravel was common on the surface. The 10-year average erosion rate of divides (26 mm yr?1) was significantly greater than the average erosion rate of gullies (14 mm yr?1), suggesting control by different processes, some of which may be seasonal. In winter, it was observed that frost action produced a thin layer of loose soil on the surface of divides. In summer, a hardpan developed on divides, as the soil loosened by winter frosts was transported to gullies, likely by rainsplash or dry ravel. The diffusive processes of frost action, rainsplash, and dry ravel appear to shape the convex divides in this study. Down-cutting of gullies requires channelized flow produced by intense rainfall, which is more common in summer for this location.  相似文献   

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