加速土壤侵蚀对养分流失的影响

Soil erosion and nutrient losses on newly-deforested lands in the Ziwuling Region on the Loess Plateau of China were monitored to quantitatively evaluate the effects of accelerated soil erosion, caused by deforestation, on organic matter, nitrogen and phosphorus losses. Eight natural runoff plots were established on the loessial hill slopes representing different erosion patterns of dominant erosion processes including sheet, rill and shallow gully （similar to ephemeral gully）. Sediment samples were collected after each erosive rainfall event. Results showed that soil nutrients losses increased with an increase of erosion intensity. Linear relations between the losses of organic matter, total N, NH4-N, and available P and erosion intensity were found. Nutrient content per unit amount of eroded sediment decreased from the sheet to the shallow gully erosion zones, whereas total nutrient loss increased. Compared with topsoil, nutrients in eroded sediment were enriched, especially available P and NH4-N. The intensity of soil nutrient losses was also closely related to soil erosion intensity and pattern with the most severe soil erosion and nutrient loss occurring in the shallow gully channels on loessial hill slopes. These research findings will help to improve the understanding of the relation between accelerated erosion process after deforestation and soil quality degradation and to design better eco-environmental rehabilitation schemes for the Loess Plateau.     

黄土高原土壤养分的损失

The soil nutrient losses due to excessive soil loss on Loess Plateau were studied by means of runoff plots and systematical determination of soil nutrients both in sediments and runoff.The results show that the amounts of nutrient losses depended on the amounts of ersoion sediments.Along with sediment,11-197kg nitrogen/hectare and 9-174kg phosphorus/hectare were lost,accounting for 92.46-99.47 percent of the total amount of nitrogen loss and 99.85-99.99 percent of the total amount of phosphorus loss respectively.The nutrient losses,very small in runoff,were mainly attributed to erosion of a few rainstorms during a year.The nutrient level in sediment was mostly higher than that in the original soil.Planting grass evidently redued the losses of soil nutrients.The N level was lower in runoff than in rainfall so that the N loss from runoff could be made up by rainfall.Fertilizer application to crops raised the nutrient level in runoff.     

中国黄土高原丘陵沟壑区天然降雨下不同土地利用方式的水土流失效应（英文）

The Loess Plateau,which is located in the arid and semi-arid areas of China,experiences significant soil erosion due to intense human activities and soil erodibility.It is necessary to explore and identify the land-use types or land-use patterns that can control soil erosion and achieve certain agricultural production capabilities.This study established runoff plots with two slope gradients(5°and 15°) in north of Yan'an,one area of the Loess Plateau,with 3 single land-use types(cultivated land,CL;switchgrass,SG;and abandoned land,AL) and 2 composite land-use types(CL-SG and CL-AL).Prom 2006 to 2012,we continuously monitored the rainfall characteristics,runoff depth,soil loss,vegetation coverage,and soil physical properties.The results indicated a general trend in the number of runoff and soil loss events for the 5 land-use types:CL = CL-SG CL-AL SG AL.The general trend for runoff depth,soil loss,their magnitudes of variation,and the slopes of rainfall-runoff regression equation was CL CL-SG CL-AL SG AL,whereas the rainfall threshold for runoff generation exhibited the opposite trend.Results of nonparametric test regarding runoff depth/EI_(30) and soil loss/EI_(30),where EI_(30) is the product of rainfall kinetic energy and the maximum rainfall intensity over 30 min,and the runoff depth-soil loss relationship regression indicated that the effect of CL-AL was similar to that of SG;SG was similar to AL;and CL-AL,SG,and AL were superior to CL with regard to soil and water conservation.Runoff depth and soil loss significantly increased as the slope gradient increased.Runoff depth and soil loss were significantly correlated with the soil particle size composition and bulk density,respectively.The strongest significant correlations were found between runoff depth and vegetation coverage as well as between soil loss and vegetation coverage,which showed that vegetation coverage was the primary factor controlling soil erosion.Therefore,the composite land-use type CL-AL and the artificial grassland(SG) are appropriate options because both soil conservation and a certain degree of agricultural production are necessary in the study area.     

中国滇池流域土地利用方式对土壤侵蚀和养分状况的影响

Soil erosion and loss of soil nutrients have been a crucial environment threat in Southwest China. The land use and its impact on soil qualities continue to be highlighted. The present study was conducted to compare soil erosion under four land use types(i.e.,forestland, abandoned farmland, tillage, and grassland) and their effects on soil organic carbon(SOC), total nitrogen(TN) and total phosphorus(TP) in the Shuanglong catchment of the Dianchi Lake watershed, China. There were large variations in the erosion rate and the nutrient distributions across the four land use types. The erosion rates estimated by137 Cs averaged 2 133 t km-2year-1under tillage and abandoned farmland over the erosion rate of non-cultivated sites, and the grasslands showed a net deposition. For all sites, the nutrient contents basically decreased with the soil depth. Compared with tillage and abandoned farmland, grassland had the highest SOC and TN contents within 0–40 cm soil layer, followed by forestland. The significant correlations between137 Cs, SOC and TN were observed. The nutrient loss caused by erosion in tillage was the highest. These results suggested that grassland and forestland would be beneficial for SOC and TN sequestration over a long-term period because of their ability to reduce the loss of nutrients by soil erosion. Our study demonstrated that reduction of nutrient loss in the red soil area could be made through well-managed vegetation restoration measures.     

中国黄土高原丘陵沟壑区天然降雨下不同土地利用方式的水土流失效应

The Loess Plateau, which is located in the arid and semi-arid areas of China, experiences significant soil erosion due to intense human activities and soil erodibility. It is necessary to explore and identify the land-use types or land-use patterns that can control soil erosion and achieve certain agricultural production capabilities. This study established runoff plots with two slope gradients (5^O and 15^O) in north of Yan’an, one area of the Loess Plateau, with 3 single land-use types (cultivated land, CL; switchgrass, SG; and abandoned land, AL) and 2 composite land-use types (CL-SG and CL-AL). From 2006 to 2012, we continuously monitored the rainfall characteristics, runoff depth, soil loss, vegetation coverage, and soil physical properties. The results indicated a general trend in the number of runoff and soil loss events for the 5 land-use types: CL = CL-SG > CL-AL > SG> AL. The general trend for runoff depth, soil loss, their magnitudes of variation, and the slopes of rainfall-runoff regression equation was CL > CL-SG > CL-AL > SG > AL, whereas the rainfall threshold for runoff generation exhibited the opposite trend. Results of nonparametric test regarding runoff depth/EI₃₀ and soil loss/EI₃₀, where EI30 is the product of rainfall kinetic energy and the maximum rainfall intensity over 30 min, and the runoff depth-soil loss relationship regression indicated that the effect of CL-AL was similar to that of SG; SG was similar to AL; and CL-AL, SG, and AL were superior to CL with regard to soil and water conservation. Runoff depth and soil loss significantly increased as the slope gradient increased. Runoff depth and soil loss were significantly correlated with the soil particle size composition and bulk density, respectively. The strongest significant correlations were found between runoff depth and vegetation coverage as well as between soil loss and vegetation coverage, which showed that vegetation coverage was the primary factor controlling soil erosion. Therefore, the composite land-use type CL-AL and the artificial grassland (SG) are appropriate options because both soil conservation and a certain degree of agricultural production are necessary in the study area.     

树的年轮和土壤中元素含量的长期分布情况

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.     

Aggregate Stability and Its Relationship with Some ChemicalProperties of Red Soils in Subtropical China

The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and A1 oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving and the Le Bissonnais methods. The results indicated that the aggregates of the severely eroded soils were more stable than those of the slightly eroded soils. Different aggregate breakdown mechanisms resulted in different particle size distribution. The slaking from entrapped air in aggregates severely destroyed the soil aggregates,especially in the slightly eroded soils. Meanwhile, mechanical breakdown and microcracking had little effect on the aggregates compared to slaking. The fragments resulting from slaking were mainly microaggregates that increased in size with increasing clay content. The main fragment size of the slightly eroded soils was 1.0-0.2 mm, while for the severely eroded soils it was 5.0-2.0 mm and 1.0-0.5 mm. Overall, more than 20% of the fragments were smaller than 0.2 mm.In addition, aggregate stability was positively and often significantly correlated with Fed, Ald, Feo and clay content, but significantly and negatively correlated to SOC.     

中国亚热带红壤团聚体稳定性与土壤化学性质的关系

The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and Al oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving and the Le Bissonnais methods. The results indicated that the aggregates of the severely eroded soils were more stable than those of the slightly eroded soils. Different aggregate breakdown mechanisms resulted in different particle size distribution. The slaking from entrapped air in aggregates severely destroyed the soil aggregates, especially in the slightly eroded soils. Meanwhile, mechanical breakdown and microcracking had little effect on the aggregates compared to slaking. The fragments resulting from slaking were mainly microaggregates that increased in size with increasing clay content. The main fragment size of the slightly eroded soils was 1.0-0.2 mm, while for the severely eroded soils it was 5.0-2.0 mm and 1.0-0.5 mm. Overall, more than 20% of the fragments were smaller than 0.2 mm. In addition, aggregate stability was positively and often significantly correlated with Fe_d, Al_d, Fe_o and clay content, but significantly and negatively correlated to SOC.     

侵蚀引起的苏南坡地土壤退化

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.     

湿润速率和粘粒含量对红壤沟间侵蚀的影响

An aggregate stability test and a simulated rainfall test were conducted on four representative Ultisols from southeastern China. The soils selected, with clay contents ranging between 117 and 580 g kg-1 , were derived from shale and Quaternary red clay. The stability of aggregates (2–5 mm in diameter) obtained from the soil samples were determined by the Le Bissonnais method. For determination of infiltration, runoff, and erosion, the soil samples were packed in 30 cm × 60 cm trays, wetted at rates of 2, 10, and 60 mm h-1 , and then exposed to simulated rainfall at 60 mm h-1 for 1 h. The results indicated that both aggregate stability and slaking caused by fast wetting increased with increasing clay content. The effect of wetting rate (WR) on infiltration and seal formation varied with clay contents. In the soil with low clay content (sandy loam), the infiltration rate was affected slightly by WR due to low aggregate stability and slaking. In the soils with medium clay content (silt clay loam and clay), WR affected infiltration significantly due to the high aggregate slaking force. In the soil with high clay content, the effect of WR on infiltration was significant, but not as evident as in the soils with medium clay content, which may be related to high aggregate stability by wetting partially compensating for slaking force. The effect of WR on soil loss was similar to that of runoff, but more pronounced. The findings from this study indicated that the relationship between wetting rate and clay content should be considered when predicting interrill erosion in Ultisols.     

Residue cover and rainfall intensity effects on runoff soil organic carbon losses

Soil cover and rainfall intensity (RI) are recognized to have severe impacts on soil erosion and an interaction exists between them. This study investigates the effect of rainfall intensity (RI) and soil surface cover on losses of sediment and the selective enrichment of soil organic carbon (SOC) in the sediment by surface runoff. A field rainfall simulator was used in the laboratory to produce 90 min rainfall events of three rainfall intensities (65, 85 and 105 mm h^− 1) and four cover percentages (0%, 25%, 50% and 75%) on soil material at 9% slope. A strong negative exponential relation was observed between cover percentage and RI on sediment loss under 85 and 105 mm h^− 1 of rain, while under RI of 65 mm h^− 1, the highest sediment loss was observed under 25% cover. Overall, higher RI and lower cover produced higher sediment and consequently higher nutrient loss, but resulted in a lower SOC enrichment ratio (ER_SOC) in the sediment. The amount of runoff sediment rather than the ER_SOC in the sediment was the determinant factor for the amount of nutrients lost. The values of ER_SOC were high and positively correlated with the ER values of particles smaller than 20 µm (p < 0.01). Although the sediment contained substantially more fine fractions (fine silt and clay, < 20 µm), the original soil and runoff sediment were still of the same texture class, i.e. silt clay loam.     

湖北低山丘陵区侵蚀泥沙颗粒特征及其与地形因子的关系

坡面地形变化是影响侵蚀泥沙颗粒特征的重要因素,深入理解地形因子与侵蚀泥沙颗粒粒径组成及分选特征的关系是研究坡面土壤侵蚀动力学的基础。采用野外降雨试验和粒径分析试验,结合ArcGIS系统识别和提取得到地形因子数据,研究低山丘陵地区侵蚀泥沙颗粒特征及其与地形因子的关系。结果表明:(1)在试验条件下,侵蚀泥沙中黏粒和粉粒总含量远高于砂粒,粗颗粒含量与坡度因子呈显著正相关关系(p0.01),粗颗粒与洼地蓄积量呈显著负相关关系(p0.05)。(2)试验样地平均质量直径MWD变化范围为0.031～0.164 mm,分形维数D的变化范围为2.021～2.778,MWD和D的决定因素是粗颗粒含量多少。从整体来看,雨强对泥沙颗粒分选特征参数影响显著,MWD随雨强的增大而增大,D随雨强的增大而减小,二者与坡度因子呈显著相关关系(p0.05)。(3)回归分析表明,MWD、D与坡度因子、洼地蓄积量呈显著幂函数关系(R~20.5),结合相关性研究结果,将坡度因子作为侵蚀泥沙粒径模型研究的优先选择。研究结果旨在揭示地形因子对坡面侵蚀泥沙颗粒的作用机理,为土壤侵蚀模型的构建提供科学参考。     

黄土丘陵区两种典型灌木群落坡面侵蚀泥沙颗粒组成及养分流失的比较

在野外模拟降雨条件下,比较研究了黄土丘陵区柠条(Cnragana korshinkii)和狼牙刺(Sophoraviciifolia)径流小区产流产沙、侵蚀泥沙颗粒组成、比表面积(SSA)及养分流失特征.结果表明,两种灌木群落均能显著减小坡面径流泥沙的流失.产流后流失泥沙黏粒、SSA与养分含量随降雨时间总体呈现降低趋势,其中有机质变化显著,全磷变化不显著.受植被盖度影响,泥沙中黏粒与养分含量均表现为柠条群落>狼牙刺群落>对照裸地.侵蚀泥沙具有富集黏粒和富集养分的特征,富集率随群落盖度增大而增大(柠条>狼牙刺>裸地).不同形态养分富集率不同,其中有机质均在2.5以上,全氮平均富集率为2.13,全磷为1.23.富集率随产流时间呈线性递减.流失泥沙养分含量与黏粒(粒径<0.002 mm)含量及SSA达到极显著的正相关.坡面土壤养分主要以黏粒为载体流失.SSA的变化不仅能体现土壤颗粒组成的变化,而且能够反映土壤养分的变化.     

Effects of intra-storm variations in rainfall intensity on interrill runoff and erosion

Five simulated rainstorms, each with a different rainfall intensity pattern but all delivering the same total kinetic energy to the soil surface, were applied to three different soils in a laboratory flume. The storm patterns were: constant rainfall intensity, increasing intensity, decreasing intensity, increasing then decreasing intensity and decreasing then increasing intensity. The three soils were: a clay loam, a sandy loam and a sandy soil. No differences in total runoff were observed that were consistent across the three soil types. However, consistent differences were observed in the amount and size distribution of the eroded sediment. In particular, the constant-intensity storm yielded an average soil loss of 75% of the varying-intensity storms, and the eroded sediment from the constant-intensity storms had a lower clay content than that from the varying-intensity storms. In contrast to the differences in amount and size distribution of eroded sediment, splashed sediment exhibited much smaller differences. Interrill erosion rates are widely assumed to vary with rainfall intensity to the power 2, but this relationship has been obtained from experiments over a range of rainfall intensities, but in which rainfall intensity has been constant in each experiment. The experiments reported here, undertaken using variable rainfall intensity within each experiment, indicates an exponent of 2.55. The experiments demonstrate that the assumption that a given rainfall intensity falling on a given soil for a given amount of time will result in a given amount of runoff and erosion is unsound. They point to the need for a greater understanding of the processes of interrill sediment detachment and transport in order to model successfully erosion under temporally varying rainfall.     

模拟降雨下覆沙坡面侵蚀颗粒特征研究

风水交错侵蚀是风蚀水蚀交错区土壤侵蚀的主要形式,研究风水交错侵蚀对土壤颗粒的影响对于进一步研究风水交错侵蚀耦合机制及其对环境的影响有重要意义。采用人工模拟降雨试验,研究不同雨强和覆沙厚度及长度)条件下覆沙坡面侵蚀泥沙颗粒的变化特征。结果表明:不同降雨条件下侵蚀泥沙颗粒中粉粒和砂粒的含量较高,分别达到了48.86%、42.77%;坡面覆沙后,侵蚀泥沙中以粗颗粒居多,以黄土作为供试土壤,表层覆盖沙物质以后,仅有黏粒的富集率大于1;侵蚀泥沙的分形维数随着覆沙厚度和长度的增大而减小,d50则随着覆沙厚度和长度的增大而增大;覆沙厚度和长度对分形维数和d50的影响大于雨强。     

雨强和土地利用方式对豫西南山区有机质流失的影响

[目的]研究丹江口水库水源区不同降雨强度和土地利用方式对土壤中有机质流失的影响,为该区域的面源污染和水土流失防治提供依据。[方法]通过人工模拟降雨试验,以豫西南山区5种常见土地类型的表层土壤为研究对象,应用双因素方差分析,研究雨强和土地利用方式对土壤中有机质的影响。[结果]雨强对径流中有机质的流失影响显著,雨强越大流失量也越大,而土地类型对其影响不大;泥沙中的有机质流失量受雨强和土地类型的影响均显著,随雨强增加而增大;农用地(梯田和坡耕地)中随泥沙流失的有机质含量较高,林草地则低;分别对径流和流失泥沙中的有机质含量与雨强作回归分析,均显示出多项式拟合效果最好(除灌草地的泥沙拟合外)。[结论]梯田作为一种水保措施,能够保持养分和水土流失,因此其土壤中富集的养分也最多;林草地土壤结构较好,能够减缓土壤侵蚀,因而流失的养分也较少。     

天然降雨下紫色土和第四纪红黏土坡面侵蚀过程研究

选取南方红壤区紫色土和第四纪红黏土两种典型土壤类型,通过天然降雨试验,在同等试验条件下对紫色土和第四纪红黏土两种土壤的坡面侵蚀过程中径流量变化、产沙量变化、土壤团聚体以及粒径分析来阐述我国南方红壤区的土壤坡面侵蚀过程。结果表明:（1）降雨是造成土壤坡面产生径流的主要原因,随着降雨的不断增大,土壤坡面径流量不断的增加,紫色土的总径流量较第四纪红黏土大。（2）雨强是造成土壤坡面产沙量的主要原因,特别是在中雨强降雨和大雨强降雨时,土壤侵蚀泥沙量的产生比较明显,紫色土与第四纪红黏土的土壤侵蚀泥沙量比例关系为:1.14∶1.0。（3）紫色土和第四纪红黏土均以 < 0.25 mm的微团聚体占优势,均占65%以上,而紫色土达到90%之多,紫色土微团聚体流失较第四纪红黏土严重。（4）通过两种土壤的降雨前后土壤颗粒对比分析,紫色土减少的土壤颗粒主要是黏粒和粉粒,砂粒相对增加,变化量大,而第四纪红黏土相对较少。     

Size characteristics of sediments eroded from three soils in China under natural rainfall

Purpose

The particle-size distribution of runoff sediment is important in understanding, characterizing and modeling the transport behavior of sediment and sediment-associated chemicals. The objective of this study was to investigate the particle-size distribution of sediments eroded from three soils in China under natural rainfall.

Materials and methods

Each of the three soils was packed to a depth of 30 cm in a 20?×?2.1 m runoff plot. Sediments yielded in nine natural rainfall events were analyzed for their particle-size distribution prior to and following dispersion.

Results and discussion

The sediment size measured in the undispersed condition was always larger than the one determined after chemical dispersion, indicating that part of the sediment was eroded in aggregated form. The degree of sediment aggregation depended on the clay content and the organic matter content of the sources. The mean sediment size quantified by mean weight diameter linearly increased with sediment yield for the two soils with relatively high clay content. The rate of increase was greater in the undispersed condition than that in the dispersed condition for these two soils. Comparing sediments to the corresponding source soil, the results of mean weight diameter and enrichment ratio both revealed that aggregate-size distribution was more sensitive to soil erosion than the primary particle-size distribution. Small aggregates, rather than the primary particles, were selectively eroded in the rainfall events.

Conclusions

These findings support the use of both dispersed and undispersed sediment-size distributions for the characterization of sediment transport and the associated sediment-bound nutrients and contaminants.

     

雨型和坡长对侵蚀泥沙粒径特征的影响

为揭示降雨和坡长对侵蚀泥沙粒径特征的影响,以不同坡长野外观测试验小区为对象,结合82场降雨资料,以降雨量(P,mm)、最大30 min雨强(I₃₀,mm/h)和降雨侵蚀力[R,MJ·mm/(hm²·h)]为降雨特征指标,利用系统聚类法进行雨型划分(A雨型：大雨量、高雨强、高侵蚀力;B雨型：中雨量、小雨强、中等侵蚀力;C雨型：低雨量、中雨强、中低等侵蚀力),分析了11场降雨事件中侵蚀泥沙的粒径分布特征。结果表明：(1)研究区侵蚀泥沙粒径特征受不同雨型影响,有效黏粒和最终黏粒含量在C雨型下最高,有效砂粒和最终砂粒含量在B雨型下最高,而有效粉粒和最终粉粒含量分别在A和C雨型下最高。(2)坡长对侵蚀泥沙粒径特征的影响存在临界坡长效应(14 m),小于临界坡长时,黏粒级和粉粒级颗粒含量随坡长增加而降低;超过临界坡长后,黏粒级和粉粒级颗粒含量随坡长增加而增加,该效应在最终粒径下更为显著。(3)有效砂粒输移形式受雨型和坡长影响较大,在B雨型下主要以团粒形式输移,在A,C雨型下达临界坡长时以单粒形式输移。侵蚀泥沙的有效粒径颗粒比原坡面土壤细,而最终粒径颗粒则...