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1.
Determining how soil erosion affects enzyme activity may enhance our understanding of soil degradation on eroded agricultural landscapes. This study assessed the changes in enzyme activity with slope position and erosion type by selecting water and tillage erosion-dominated slopes and performing analyses using the 137Cs technique. The 137Cs data revealed that soil loss occurred in the upper section of the two eroded slope types, while soil accumulation occurred in the lower section. The invertase activity increased downslope and exhibited a pattern similar to the 137Cs data. The spatial patterns of urease and alkaline phosphatase activities were similar to the 137Cs inventories on the water and tillage erosion-dominated slopes, respectively. On both the eroded slope types, the invertase activity and soil organic carbon content were correlated, but no correlation was observed between the alkaline phosphatase activity and total phosphorus content. Nevertheless, the urease activity was correlated with the total nitrogen content only on the water erosion-dominated slopes. The enzyme activity-to-microbial biomass carbon ratios indicated high activities of invertase and urease but low activity of phosphatase on the water erosion-dominated slopes compared with the tillage erosion-dominated slopes. Both the invertase activity and the invertase activity-to-microbial biomass carbon ratio varied with the slope position. Changes in the urease activity-to-microbial biomass carbon ratio were significantly affected by the erosion type. These suggested that the dynamics of the invertase activity were linked to soil redistribution on the two eroded slope types, whereas the dynamics of the urease and alkaline phosphatase activities were associated with soil redistribution only on the water or tillage erosion-dominated slopes, respectively. The erosion type had an obvious effect on the activities of invertase, urease and alkaline phosphatase. Soil redistribution might influence the involvement of urease in the N cycle and alkaline phosphatase in the P cycle. Thus, enzyme activity-to-microbial biomass ratios may be used to better evaluate microbiological activity in eroded soils. 相似文献
2.
Paulina Schuller Achim Ellies Alejandra Castillo Itilier Salazar 《Soil & Tillage Research》2003,69(1-2):69-83
The purpose of this research was to evaluate the applicability of conventional 137Cs sampling and a simplified approach, for estimating medium-term tillage- and water-induced soil erosion and sedimentation rates on agricultural land in Chile. For this purpose, four study sites under contrasting land use and management were selected in central-south Chile. First, a conventional 137Cs approach, based on grid sampling was applied, adapting a mass balance conversion model incorporating soil movement by tillage to the site specific conditions of the study region. Secondly, using the same conversion model, the feasibility of estimating soil redistribution rates from measurements of 137Cs inventories based on composite soil samples taken along contour lines was also tested at all four sites. The redistribution rates associated with tillage and water and the total rates estimated using both methods correlated strongly at all four sites. The conventional method provides more detailed information concerning the redistribution processes operating over the landscape. The simplified method is suitable for assessing soil loss and sediment accumulation in areas exhibiting simple topography and almost similar slopes along the contour lines. Under these conditions, this method permits faster estimation of soil redistribution rates, providing the possibility of estimating soil redistribution rates over larger areas in a shorter time. In order to optimise the costs and benefits of the methods, the sampling and inventory quantification strategy must be selected according to the resolution of the required information, and the scale and complexity of the landscape relief. Higher tillage- and water-induced erosion rates were observed in the annually ploughed cropland sites than in the semi-permanent grassland sites. Subsistence managed crop and grassland sites also show greater erosion effects than the commercially managed sites. The 137Cs methods used permit discrimination between redistribution rates observed on agricultural land under different land use and management. The 137Cs technique must be seen as an efficient method for estimating medium-term soil redistribution rates, and for planning soil conservation and sustainable agricultural production under the climatic conditions and the soil type of the region of Chile investigated. 相似文献
3.
Cesium and soil carbon in a small agricultural watershed 总被引：8，自引：1，他引：8
Scientific, political, and social interests have developed recently in the concept of using agricultural soils to sequester carbon. Studies supporting this concept indicate that soil erosion and subsequent redeposition of eroded soils in the same field may establish an ecosystem disequilibrium that promotes the buildup of carbon on agricultural landscapes. The problem is to determine the patterns of soil erosion and redeposition on the landscape and to relate these to soil carbon patterns. Radioactive 137cesium (137Cs) can be used to estimate soil erosion patterns and, more importantly, redeposition patterns at the field level. The purpose of this study was to determine the relationship between 137Cs, soil erosion, and soil carbon patterns on a small agricultural watershed. Profiles of soils from an upland area and soils in an adjacent riparian system were collected in 5 cm increments and the concentrations of 137Cs and carbon were determined. 137Cs and carbon were uniformly mixed in the upper 15–20 cm of upland soils. 137Cs (Bq g−1) and carbon (%) in the upland soils were significantly correlated (r2=0.66). Carbon content of the 0–20 cm layer was higher (1.4±0.3%) in areas of soil deposition than carbon content (1.1±0.3%) in areas of soil erosion as determined by the 137Cs technique. These data suggest that measurements of 137Cs in the soils can be useful for understanding carbon distribution patterns in surface soil. Carbon content of the upland soils ranged from 0.5 to 1.9% with an average of 1.2±0.4% in the 0–20 cm layer while carbon below this upper tilled layer (20–30 cm) ranged from 0.2 to 1.5% with an average of 0.5±0.3%. Total carbon was 2.66 and 3.20 kg m−2 in the upper 20 cm and upper 30 cm of the upland soils, respectively. Carbon content of the 0–20 cm layer in the riparian system ranged from 1.1 to 67.0% with an average 11.7±17.1%. Carbon content below 20 cm ranged from 1.8 to 79.3% with an average of 18.3±17.5%. Soil carbon in the upper 20 cm of the riparian profile was 10.1 and 15.0 kg m−2 in the upper 30 cm of the riparian profiles. This is an increase of organic carbon by a factor of 3.8 and 4.7 for the upper 20 cm and upper 30 cm of the riparian profiles, respectively, when compared to the upland soil profiles. 相似文献
4.
《CATENA》2004,57(1):15-34
Concentrations in the soil of anthropogenic and natural radionuclides have been investigated in order to assess the applicability of the 137Cs technique in an area of typical Mediterranean steep slopes. This technique can be used to estimate net soil redistribution rates but its potential in areas with shallow and stony soils on hard rock lithology have not been evaluated so far. In this research, the validity of using this technique in stony shallow soils at very steep slopes is discussed together with the relations between radionuclide concentrations and other soil properties, lithology, slope morphology and land use in a Mediterranean environment. Both natural Potassium-40 (40K), Uranium-238 (238U), Thorium-232 (232Th) and anthropogenic Caesium-137 (137Cs) radionuclides have been determined in samples taken along slope transects on uncultivated serpentinite soils and cultivated gneiss soils. In addition to the radionuclide concentrations, parameters such as slope position, slope angle, aspect, soil depth, surface stone cover, moss, litter, vegetation cover, soil crust, stone content and bulk density have been quantified.All the natural radionuclides 40K, 238U, 232Th show significantly higher concentrations in the gneiss than in the serpentinite soils, opposed to the 137Cs concentration, which is found significantly higher in the serpentinite soils probably because of the difference in clay mineralogy. The exponential decreasing depth distribution of 137Cs and its homogeneous spatial distribution emphasise the applicability of the 137Cs technique in this ecosystem.Lithology determines the concentration of natural and anthropogenic radionuclides. Land use determines the relations between 137Cs concentration/inventory and some soil characteristics. Higher 137Cs concentration and inventory are associated with higher percentages of vegetation cover, higher percentage of stones in the soil and higher values of soil bulk density in cultivated gneiss soils. Slope morphology and land use influence the soil redistribution at slope scale. The gneiss slopes show a zonation of four to five areas of differential erosion/accumulation processes corresponding with more regular slopes and soil redistribution due to water erosion and to tillage translocation and erosion. The serpentinites, as an example of a more unstable slope type, show more erosion areas with less accumulation downslope and soil redistribution due to water erosion. 相似文献
5.
侵蚀引起的苏南坡地土壤退化 总被引：5，自引：0，他引：5
Soil erosion accelerates soil degradation. Some natural soils and cultivated soils on sloping land in southern Jiangsu Province, China were chosen to study soil degradation associated with erosion. Soil erosion intensity was investigated using the 137Cs tracer method. Soil particle-size distribution, soil organic matter (OM), total nitrogen (TN) and total phosphorus (TP) were measured, and the effects of erosion on soil physical and chemical properties were analyzed statistically using SYSTAT8.0. Results indicated that erosion intensity of cultivated soils was greater than that of the natural soils, suggesting that cultivation increased soil loss. Erosion also led to an increase of coarser soil particle proportion, especially in natural soils. In addition, silt was the primary soil particle lost due to erosion. However, in cultivated fields, coarser soil particles over time were attributed not only to soil erosion but also to mechanical eluviation as a result of farming activities. Moreover, erosion caused a decrease in soil OM, TN and TP as well as thinning of the soil layer. 相似文献
6.
[目的]探讨用~(137)Cs示踪技术估算土壤侵蚀量方法(以下简称"~(137)Cs示踪方法")所存在的几个关键问题,促进该方法的标准化和系统化。[方法]对大量已发表的相关文献进行分析,根据作者的研究经验,归纳出~(137)Cs示踪方法在实践应用中所存在的核心问题。[结果]~(137)Cs示踪方法中关于~(137)Cs在空间是均匀分布的假设存在不合理性,不能直接用于定量估算单钻点取样的土壤侵蚀量。~(137)Cs活度的空间变化存在随机性的成分。敏感度和不确定性分析结果证明~(137)Cs活度的空间随机变化量是~(137)Cs示踪方法不确性的最大来源。[结论]可以用多钻点样本平均值来减少~(137)Cs随机变化量所引起的侵蚀估算误差。以统计学为基础的试验设计和采取独立样本的办法可以消除该误差。虽然~(137)Cs模型已被广泛应用,但由于缺乏长期观测资料诸多模型还处在理论研究阶段,没有得到严格的验证和评判。因为不同模型估算的侵蚀量差别甚大,模型验证和筛选对该方法的成功运用至关重要。 相似文献
7.
Vast areas of Europe were contaminated by the Chernobyl-derived 137Cs in April–May 1986. This paper reports a detailed study of the post-fallout 137Cs redistribution within a 1 ha field located in the Chasovenkov Verh catchment in the northern part of the Middle-Russian upland. Particular attention was paid to the study of reference inventories. It is shown that the random spatial variability of 137Cs is similar within undisturbed and cultivated parts of a flat interfluve. Systematic spatial variability is not essential for a relatively short (200 m) topographical unit with simple relief. The analysis of a soil redistribution pattern within the study field using the Chernobyl 137Cs technique demonstrates that it is possible to identify areas of soil loss/gain. This pattern does not reflect soil redistribution for the whole field, because these have been only 12 years since the Chernobyl accident. Net erosion rates based on 137Cs method were comparable to soil losses directly measured at the study field. 相似文献
8.
This study was carried out to obtain a representative set of data on long-term erosion rates from a pilot area located close to the Jaslovske Bohunice village, in western Slovakia using the 137Cs-method. The study area chosen was representative of the hilly loess cultivated areas of Slovakia. The sampling strategy was based on a multiple transect approach. Analyses of the samples for 137Cs activity were made at the Nuclear Power Plant Research Institute, Jaslovske Bohunice. The 137Cs-method was used to obtain long-term estimates of soil erosion in the Jaslovske Bohunice site, a representative hilly loess cultivated area of Slovakia. The estimated reference 137Cs inventory was 2910 Bq m−2, with a coefficient of variation of 4.3%.Examination of the 137Cs redistribution in relation to the topography of the study area revealed that, within individual transects the 137Cs inventories were closely related to major landforms. The 137Cs inventories were considerably lower on the slopes than on the plateau and they were highest in the valley. However, when plotted against a selection of individual quantitative slope parameters, i.e. the S and the LS factors of the USLE or slope inclination, the correlations obtained were weak.Three conversion models, i.e. the proportional model (PM), the simplified mass balance model (MBM1) and the standard mass balance model (MBM2), from the set of models developed at Exeter University, Great Britain were selected to interpret the resulting 137Cs measurements into soil erosion/deposition rates. The mean erosion rates estimated with the PM were 22.4, 35.6 with MBM1 and 17.3 t ha−1 per year with MBM2. There was a good agreement between the average of these mean erosion rates (25.1 t ha−1 per year) for the Jaslovske Bohunice site and the estimated mean soil erosion rate obtained for small erosion plots (15 t ha−1 per year) for conditions similar to the study site. Nevertheless, further research on the application of the 137Cs-method, in particular the independent validation of the results obtained, is needed. Several issues requiring further study have been highlighted. 相似文献
9.
赣南红壤丘陵区137Cs示踪土壤侵蚀对土壤养分元素的影响 总被引：1，自引：1，他引：0
赣南红壤丘陵区是我国土壤侵蚀与土地退化比较严重的地区,以南丰县为例,应用137 Cs示踪技术探讨不同土地利用方式下土壤侵蚀与养分元素的关系。结果表明:(1)湿地松林、桔园、水田3种土地利用方式作用下土壤中137 Cs与养分元素分布差异显著,在垂直剖面上,湿地松林137 Cs含量呈指数递减分布,水田与桔园137 Cs含量因人为干扰在耕层内均匀分布;有机质与137 Cs有相似的分布特征;全氮、碱解氮、速效磷、速效钾含量均呈现一定表聚性。(2)位于坡地的2种土地利用方式中,湿地松林137 Cs、全氮、碱解氮、速效磷、速效钾、有机质含量均表现为下坡>上坡>中坡;桔园137 Cs活度表现为中坡>下坡>上坡,全氮、碱解氮、速效磷表现为下坡>中坡>上坡,而速效钾、有机质最大值均出现在上坡。(3)相关性分析表明,土壤137 Cs与有机质、全氮、碱解氮显著正相关,表明小流域有机质、氮元素可能与137 Cs有相同的物理运移方式,pH与137 Cs显著负相关,速效磷、速效钾则与137 Cs不相关。(4)3种土地利用方式中位于小流域谷地的水田137 Cs、有机质、全氮、碱解氮含量最高,坡地上桔园坡面137 Cs与土壤养分元素含量均高于湿地松林地,表明一定程度的坡改梯桔园种植模式能有效缓解土壤侵蚀与养分流失,改善区域生态环境。 相似文献
10.
The impact of soil erosion on the nutrient dynamics in alpine grassland soils is still an essential problem. Selecting a grass-covered hillslope in eastern Tibet Plateau, the cesium-137 (137Cs) technique was used to determine the impacts of soil erosion on soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), and total potassium (TK). The 137Cs data revealed that there were distinct soil redistribution patterns in different hillslope positions because of the influences of slope runoff, plant coverage and grazing activity. For the upper slope, soil erosion first decreased downward, followed by soil deposition in its lower part. In contrast, for middle and toe slopes, there was an increasing soil erosion along a downslope transect. Across the lower slope, soil erosion showed an irregular variation. Influenced by the selective transport of water erosion, SOC, TN and TP storage decreased with increasing soil erosion in upper, middle and toe slopes. In contrast, SOC, TN and TP storage varied little with soil erosion in the lower slope. On the whole hillslope, TK storage also varied little with soil erosion due to the large amount of potassium elements derived from soil parent materials. Particularly noteworthy was the greatest storage of SOC, TN and TP in the lower slope where most obvious net soil erosion occurred, which is closely related to the humus accumulation combined with gravel separation as well as weathering and pedogenesis of parent rocks induced by soil freeze-thaw. 相似文献
11.
Water erosion in the hilly areas of west China is the main process contributing to the overall sediment of the Yellow River and the Yangtze River. The impact of gully erosion in total sediment output has been mostly neglected. Our objective was to assess the sediment production and sediment sources at both the hillslope and catchment scales in the Yangjuangou reservoir catchment of the Chinese Loess Plateau, northwest China. Distribution patterns in sediment production caused by water erosion on hills and gully slopes under different land use types were assessed using the fallout 137Cs technique. The total sediment production from the catchment was estimated by using the sediment record in a reservoir. Sediment sources and dominant water erosion processes were determined by comparing 137Cs activities and 210Pb/137Cs ratios in surface soils and sub-surface soils with those of sediment deposits from the reservoir at the outlet of the catchment. Results indicated that landscape location had the most significant impact on sediment production for cultivated hillslopes, followed by the terraced hillslope, and the least for the vegetated hillslope. Sediment production increased in the following order: top>upper>lower>middle for the cultivated hillslope, and top>lower>upper>middle for the terraced hillslope. The mean value of sediment production declined by 49% for the terraced hillslope and by 80% for the vegetated hillslope compared with the cultivated hillslope. Vegetated gully slope reduced the sediment production by 38% compared with the cultivated gully slope. These data demonstrate the effectiveness of terracing and perennial vegetation cover in controlling sediment delivery at a hillslope scale. Averaged 137Cs activities and 210Pb/137Cs ratios in the 0–5 cm surface soil (2.22–4.70 Bq kg−1 and 20.70–22.07, respectively) and in the 5–30 cm subsoil (2.60 Bq kg−1 and 28.57, respectively) on the cultivated hills and gully slopes were close to those of the deposited sediment in the reservoir (3.37 Bq kg−1 and 29.08, respectively). These results suggest that the main sediment sources in the catchment were from the surface soil and subsoil on the cultivated slopes, and that gully erosion is the dominant water erosion process contributing sediment in the study area. Changes in land use types can greatly affect sediment production from gully erosion. An increase in grassland and forestland by 42%, and a corresponding decrease in farmland by 46%, reduced sediment production by 31% in the catchment. 相似文献
12.
利用137Cs示踪技术评价东北黑土侵蚀和沉积过程 总被引：6，自引：1，他引：6
Soil and water losses through erosion have been serious in the black soil region of Northeast China. Therefore, a sloping cultivated land in Songnen Plain was selected as a case study to： 1） determine the ^137Cs reference inventory in the study area; 2） calculate erosion and deposition rates of black soil on different slope locations; 3） conduct a sensitivity analysis of some model parameters; and 4） compare overall outputs using four different models. Three transects were set in the field with five slope locations for each transect, including summit, shoulder-slope, back-slope, foot-slope, and toe-slope. Field measurements and model simulation were used to estimate a bomb-derived ^137Cs reference inventory in the study area. Soil erosion and deposition rates were estimated using four ^137Cs models and percentage of ^137Cs loss/gain. The ^137Cs reference value in the study area was 2 232.8 Bq m^-2 with ^137Cs showing a clear topographic pattern, decreasing from the summit to shoulder-slope, then increasing again at the foot-slope and reaching a maximum at the toe-slope, Predicted soil redistribution rates for different slope locations varied. Among models, the Yang Model （YANG-M） overestimated erosion loss but underestimated deposition. However, the standard mass balance model （MBM1） gave predictions similar to a mass balance model incorporating soil movement by tillage （MBM2）. Sensitivity analysis of the proportion factor and distribution pattern of ^137Cs in the surface layer demonstrated the impact of ^137Cs enrichment on calculation of the soil erosion rate. Factors influencing the redistribution of fallout ^137Cs in landscape should be fully considered as calculating soil redistribution rate using ^137Cs technique. 相似文献
13.
14.
Distributed erosion and sediment yield models are being increasingly used for predicting soil erosion and sediment yields in agricultural catchments. In most applications, validation of such models has commonly been restricted to comparison of the predicted and measured sediment output from a catchment, because spatially distributed information on rates and patterns of soil redistribution within the catchment has been lacking. However, such spatially distributed data are needed for rigorous model testing, in order to validate the internal functioning of a model and its applicability at different spatial scales. The study reported in this paper uses two approaches to test the performance of the agricultural non-point source pollution (AGNPS) and areal non-point source watershed environmental response simulation (ANSWERS) erosion and sediment yield models in two small catchments in Devon, UK. These involve, firstly, comparison of observed and predicted runoff and sediment output data for individual storm events monitored at the basin outlets and, secondly, information on the spatial pattern of soil redistribution within the catchments derived from 137Cs measurements. The results obtained indicate that catchment outputs simulated by both models are reasonably consistent with the recorded values, although the AGNPS model appears to provide closer agreement between observed and predicted values. However, the spatial patterns of soil redistribution and the sediment delivery ratios predicted for the two catchments by the AGNPS and ANSWERS models differ significantly. Comparison of the catchment sediment delivery ratios and the pattern of soil redistribution in individual fields predicted by the models with equivalent information derived from 137Cs measurements indicates that the AGNPS model provides more meaningful predictions of erosion and sediment yield under UK conditions than the ANSWERS model and emphasises the importance of using information on both catchment output and sediment redistribution within the catchment for model validation. 相似文献
15.
The use of environmental radionuclides as tracers in soil erosion and sedimentation investigations: recent advances and future developments 总被引：9，自引：0，他引：9
Although much of the recent attention on the environmental problems has focused on climatic change, there is also increasing concern that accelerated soil erosion and associated land degradation represent a major problem for sustainable development and environmental protection. There is an urgent need to obtain reliable quantitative data on the extent and rates of soil erosion worldwide to provide a more comprehensive assessment of the magnitude of the problems and to underpin the selection of effective soil conservation measures. The use of environmental radionuclides, in particular 137Cs, affords an effective and valuable means for studying erosion and deposition within the landscape. The key advantage of this approach is that it can provide retrospective information on medium-term (30–40 years) erosion/deposition rates and spatial patterns of soil redistribution, without the need for long-term monitoring programmes. Advantages and limitations of the technique are highlighted. The launching of two closely linked International Atomic Energy Agency (IAEA) research networked projects in 1996 involving some 25 research groups worldwide has made a major contribution to co-ordinating efforts to refine and to standardise the 137Cs technique. The efficacy and value of the approach has been demonstrated by investigations in a number of environments. Significant developments that have been made to exploit its application in a wide range of studies are reported in this review paper. Other environmental radionuclides, such as unsupported 210Pb and 7Be offer considerable potential for use in soil erosion investigations, both individually and complementary to 137Cs. The IAEA through research networks and other mechanisms is promoting further development and applications of these radionuclides in soil erosion and sedimentation studies for a sustainable resource use and environmental protection. 相似文献
16.
Enrichment ratios (ER) are widely used to predict loss of sorbed nutrients or pesticides with runoff sediment, while ER is frequently neglected in studies which quantify past erosion from global fallout 137Cs losses. The ER of 137Cs (ER- 137Cs) in the soil loss and the subsequent depletion of 137Cs at the soil surface were determined for eight small watersheds (1.6–16.8 ha) with different soils and land use. Due to preferential loss of the clay fraction, the upper 5 mm of the soil surface was significantly depleted of 137Cs after a heavy storm. A total of 31 watershed-events were investigated with soil losses ranging between 1.2 and 480 kg-ha?1 and sediment concentrations between 1.98 and 54.1 g?L?1 The correspondent ER-137Cs (mean: 1.72, range: 0.40–4.95) was positively correlated to the ER of clay, organic carbon, total nitrogen and calcium-acetate-lactate-extractable phosphorus (PCAL). A close correlation between ER-137Cs and ER-PCAL was also found for sediment samples of detention ponds, where most of the ER values were less than 1.0 due to depletion. Therefore, ER-PCAL seems to be a suitable estimate of ER-137Cs for both, erosion and deposition processes. Our findings strongly support the need for considering ER-137Cs, when ,37Cs data are used to assess rates and pattern of soil redistribution. Otherwise, soil loss will be overestimated in a range of about factor 2 in many cases. 相似文献
17.
In order to assess its potential for estimating soil redistribution rates, the naturally occurring fallout radionuclide 210Pbex has been used in parallel with 137Cs, derived from the atmospheric testing of nuclear weapon testing in the 1950s to 1970s, to estimate rates of soil redistribution on a sloping field with traditional erosion control measures located near Jiajia Village, Jianyang County, in the Sichuan Hilly Basin of China. The local 210Pbex reference inventory of 12,860 Bq m− 2 is higher than those reported for many other areas of the world and may reflect the influence of cloudy weather in preventing 210Pb released to the atmosphere across the local region moving up into the upper troposphere, where is would be more widely dispersed. The mean 210Pbex and 137Cs inventories measured in cores collected from the upper part of the field with an average slope of 10° were 8028 Bq m− 2 and 993 Bq m− 2, respectively, and the equivalent values for the lower part of the field, where the slopes are steeper (20°) were 11,388 Bq m− 2 and 1299 Bq m− 2. The pattern of post-fallout 210Pbex and 137Cs redistribution on the sloping field reflects not only the effects of water erosion and redistribution by tillage, but also the local traditional practice of “Tiaoshamiantu”, whereby sediment trapped in the ditches is returned to the fields by the farmer. The estimates of annual rates of soil loss provided by the 210Pbex measurement are closely comparable with those derived from the 137Cs measurements and are consistent with existing knowledge for the study area. The results obtained from this study confirm the potential for using 210Pbex measurement to estimate soil erosion rates over medium-term timescale of 50–100 years. By combining the estimates of erosion rates provided by the 210Pbex and 137Cs measurements, the weighted mean net soil loss was estimated to be 48.7 t ha− 1 year− 1 from the upper subfield and 16.9 t ha− 1 year− 1 from the lower subfield. These rates are considerably lower than the erosion rates obtained from runoff plot measurements in the local area. It is suggested that the traditional erosion control practices and the practice of “Tiaoshamiantu” have a significant effect in reducing soil loss and conserving valuable cultivated soil on sloping fields in the Sichuan Hilly Basin. 相似文献
18.
The fallout radionuclide cesium-137(137 Cs) has been widely employed as a tracer for assessment of soil loss from thick uniform soils;however,few studies have been conducted on thin stony soils on slopes underlain by carbonate rocks which are widely distributed in karst areas.Information derived from 137 Cs measurement of soil samples collected along a carbonate rock slope with thin stony soil where neither soil erosion nor deposition occurred was used to investigate the characteristics of 137 Cs redistribution in a karst area of Southwest China.The results indicated that the 137 Cs inventories of the surface soil on the slope studied were much lower than that of the local 137 Cs reference inventory and the 137 Cs activities were much higher than those on slopes with thick uniform soils.The spatial distribution of 137 Cs inventories was characterized by considerable variation.The high 137 Cs depletion in the stony soil of the slope studied was mainly because a considerable proportion of the fallout input of 137 Cs could be lost with runoff and the dissolution of carbonate particles in the soil promoted the loss of 137 Cs.These demonstrated that the rates of soil loss could not be estimated from the degree of depletion of the 137 Cs inventory relative to the local reference inventory for the thin stony soil of the rocky slope underlain by carbonate rocks in the study area in the way that has been widely used in areas with thick uniform soils. 相似文献
19.
Distribution of soil organic carbon and phosphorus on an eroded hillslope of the rangeland in the northern Tibet Plateau, China 总被引：2，自引：0，他引：2
Some studies on the relationship between soil erosion and subsequent redeposition of eroded soils in the same field and soil quality have been conducted in croplands, yet few studies have revealed this relationship in rangelands. We selected a toposequence with a slope of 30% and a horizontal length of 342 m from the rangeland in the northern Tibet Autonomous Region, China (31°16′N, 92°09′E) to determine the relationship between soil erosion, soil organic carbon (SOC) content and available P patterns within a hillslope landscape. Soil samples for the determination of 137Cs as well as SOC, available P and particle‐size fractions were collected at 20 m intervals along a transect of this hillslope. Soil redistribution was caused primarily by wind erosion at toe‐slope positions, but primarily by water erosion at the hillslope positions above the toe‐slope. In upper‐ and mid‐slope portions (0 m to 244 m horizontal length), SOC content is closely correlated to 137Cs concentration (r = 0.74, P < 0.01, n= 15), suggesting that SOC distribution along the slope was similar to 137Cs distribution, which itself was dependent on topographic changes. However, SOC contents in toe‐slope portions are less than those above the toe‐slope (i.e. upper‐ and mid‐slope portions), and the correlation between 137Cs and SOC in the toe‐slope portion is weaker than that above the toe‐slope. A highly significant correlation (r = 0.72, P < 0.001, n= 20) between 137Cs concentration and available P was found within the whole hillslope landscape, implying the distribution pattern of available P was somewhat different from that of SOC. We suggest that the distribution of SOC within the hillslope landscape is also affected by factors such as assimilation rates due to difference in grassland productivity at different points and different biological oxidation rates of carbon related to patterns of moisture distribution. 相似文献
20.
Using caesium-137 measurements to investigate soil erosion rates in western Istanbul (NW Turkey) 总被引：3，自引：0，他引：3
Sevilay Haciyakupoglu T. Ahmet Ertek Des E. Walling Z. Fatih Ozturk Gursel Karahan A. Evren Erginal Nilgun Celebi 《CATENA》2005,64(2-3):222
Buyukcekmece Reservoir, located in the western outskirts of Istanbul, is one of the major water resources of Istanbul, and supplies drinking water to about 4 million people. Erosion in the catchment of the reservoir is an important problem in terms of its longer-term sustainability for water supply. There is an urgent need to obtain reliable quantitative data regarding erosion and deposition rates within the catchment to assess the magnitude of the problem and to plan catchment management strategies. In the absence of existing data, attention has focussed on the potential for using 137Cs measurements to provide retrospective estimates of medium-term soil erosion rates within the catchment over the past ca. 40 years. To date, the 137Cs approach has not been used to document soil redistribution rates in Turkey and this contribution reports an attempt to confirm the viability of the approach and the results of a preliminary investigation of rates of soil loss from uncultivated areas within the catchment. The soil redistribution rates estimated using the profile distribution conversion model varied from − 16.11 (erosion) to 4.59 (deposition) t/ha/year. 相似文献