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1.
Laboratory and field measurements as well as deterministic simulation models were used to determine the water components of loess derived soils with different expositions and slopes in the hilly region South of Hannover, Germany. Studies were investigated from 1987-1990 on three positions of a loess slope with 8 % inclination, 200 m length and northern exposition. Crop rotation was sugar beet, winter wheat, sugar beet. Results show that the soil water budget is strongly related to slope position, relief and plant available water in the rootzone. It was found that drainage at the bottom of a slope is often higher than on top of the slope. On slopes with northern exposition groundwater recharge increases with inclination whereas actual evapotranspiration decreases. For slopes with southern exposition the opposite reaction can be expected. The thickness of loess deposits and the root depth determine the plant available water; a sensitivity study demonstrates how groundwater recharge decreases with the amount of plant available water. This reaction is independent of the exposition of the slope. Field and simulation studies show that runoff occurs under sugar beet whenever soil is bare or sparsely covered, rainfall intensity is high and topsoil is sealed. Moreover, in loess derived soils interflow may occur on sites with stagnic horizons. Sensitivity analyses show that this process probably takes place whenever saturated hydraulic conductivity of this horizon is less than 10cm/d. 相似文献
2.
Loess proportions in slope deposits have rarely been quantified, due to the lack of quantification methods. In this study, we used laser granulometry to analyze grain‐size distributions in slope deposits of a Buntsandstein landscape in central Germany. The consistent loess contents obtained from two independent models corroborate the validity of the calculated loess proportions and the applicability of the new R package EMMAgeo. Yet, some limitations in transferability need to be considered. 相似文献
3.
Surface sealing and runoff generation on soils derived from loess and pleistocene deposits An attempt is undertaken to bring together existing knowledge on the occurence of surface sealing, on subprocesses and factors controlling surface sealing, and on hydraulic properties of seals, with special reference to the soil conditions prevailing in Germany. A conceptional model is proposed that relates different subprocesses such as aggregate breakdown, aggregate deformation, particle rearrangement and different factors such as soil cover, microrelief, stone cover, and macropores to surface sealing and runoff generation. We conclude that loess soils and soils formed on pleistocene deposits are particularly prone to surface sealing, and seals formed on these soils can induce runoff at rainfall intensities of 5 mm h?1. 相似文献
4.
Two complex profiles in slope deposits in Galicia, Spain, were examined both in the field and in the laboratory. One profile consists of humous colluvium on solifluction material overlying gabbro, the other shows various layers of humous collovium on granite. 相似文献
5.
Nitrate and chloride transport in loess monolithes under quasistationary conditions The transport of nitrate and chloride has been investigated in an experiment with loess-monolithes under non-steady conditions and by a simple mathematical simulation technique approximating non-stationary flow by quasi-stationary conditions. Six precipitation cycles were followed by analysing soil solution drawn off by means of porous cups from the soil columns at different depths and times. At all times, the simulated “pure” transport profiles compare reasonably well with the experimental profiles. In the columns, however, nitrogen mineralisation took place during and before the experiment. 相似文献
6.
Release of aluminium in Northwest-German Acid Brown soils on loess-sandstone solifluction deposits In soil and clay from root zones (50 resp. 80cm) of acid brown soils, the Si and Al released during weathering was determined by fractionated extraction with 0.5 N NaOH in order to arrive at a quantitative approximation of the possible clay and silicate destruction. Extracted Al was 4-10 times higher than Si, and showed a steep gradient between Ah- and B-horizon. The Al(clay)/Al(soil) ratio varied between 0.5 to 1 depending on the admixture of sandstone material to the loess. Assuming that the clay-extracted Al was derived from the destruction of clay, we arrived at a minimum value for affected clay of 1-4,5% of the soil mass or 10 to 40% of the present clay substance. Clay destruction is discussed as Al-release leaving behind a non-crystalline Si-O-OH lattice. 相似文献
7.
陕北黄土坡面微地形土壤物理性质研究 总被引：8，自引：4，他引：4
陕北黄土坡面由于侵蚀等原因使坡面不平整,形成了各种微地形,造成了土壤物理性质的差异。对黄土高原丘陵沟壑区的微地形土壤物理性质进行了调查分析。结果表明,研究区内5种微地形与原状坡相比较,塌陷、切沟、浅沟、缓台的土壤物理性状均有所提高,而陡坎的各项性能比原状坡有所降低,主要表现在0—20cm土壤。土壤容重在0—20cm由大到小的顺序为：原状坡〉陡坎〉缓台〉浅沟〉切沟〉塌陷。土壤含水量、最大持水量、田间持水量和毛管持水量表现出比较一致的变化趋势,塌陷、缓台、切沟和浅沟这4种微地形孔隙和水分状况均高于原状坡和陡坎。土壤的总孔隙度、毛管孔隙度和非毛管孔隙度的变化趋势和土壤持水性能的变化趋势一致。通过对5种微地形物理性质进行灰色关联度分析发现,其灰色关联度由大到小的顺序为：塌陷〉切沟〉浅沟〉缓台〉陡坎〉原状坡。 相似文献
8.
黄土丘陵区典型峁坡土壤侵蚀空间分异特征 总被引：1，自引：0，他引：1
选择黄土高原丘陵沟壑区典型峁坡,采用137 Cs示踪技术,通过对不同坡向和坡位土样137 Cs含量的测定,分析了峁坡137 Cs空间分布特征及土壤侵蚀的空间分异。结果表明,不同坡向峁坡侵蚀差异明显,各坡向平均侵蚀速率大小依次为:北坡西南坡东北坡西坡西北坡南坡东南坡东坡,各坡向侵蚀强度均表现为强度侵蚀;峁坡各坡向不同坡位的侵蚀差异也非常明显,坡下部侵蚀量最大,坡面中上部次之。侵蚀速率顺坡呈波动变化趋势,且侵蚀强度表现为中度、强度以及极强度侵蚀,以强度侵蚀为主。 相似文献
9.
Facies and microfacies of slope deposits 总被引：2，自引：0，他引：2
This paper reviews the facies and microfacies of the main types of slope deposits. Lamination and sorting, when preserved, are good evidence for overland flow. Features due to deformation (folds, boudins, coatings and tails due to the rotation of clasts) are associated with the early stages of deformation in earth slides. Other mass-movements such as debris flows, rock avalanches, earth flows, and to a certain extent, dry grain flows may be characterised by similar microscopic facies, typically a poorly sorted, porphyric material. Porosity gives evidence for both liquefaction (debris flows) and frost-induced mass-movement (solifluction). However, this criterion is thought to be irrelevant for fossil deposits owing to the rapidity and scale of post-depositional changes (wetting and drying, freezing and thawing, bioturbation). At present, only a detailed analysis of both the macro- and micromorphological characteristics of the deposits allows an accurate identification of past slope dynamics. 相似文献
10.
Spatial variability of Phosphorus contents in topsoils of two small catchments under agricultural use The spatial variability of total phosphorus (Pt) contents was investigated in two small agriculturally used catchments in Saxony/Germany. The mean Pt concentration was 982 mg kg–1, with 80 % of values between 560 and 1530 mg kg–1. The largest Pt contents were found at the tops and foots of slope, and the smallest at the middle slope positions. At the scale of slopes (microscale) the spatial variability was caused by the relief and soil properties, whereas at the scale of catchments, agricultural management had the largest influence. These differences must be considered for the modeling of diffuse P inputs to surface waters. 相似文献
11.
A soil association characterized by smectitic tephra-saprolite in the Pleiser Hügelland near Bonn The study area is based by tephra-saprolite rich in smectite. If the loess cover diminishes, the tephra-saprolite comes into the zone of soil formation, and determines an independent association of soils characterized by swelling-shrinking activity, water stagnation, slope-movement, and high CEC. The soil association is differentiated by the degree of plasmatization of the saprolite, and by the depths of the upper periglacial layers. This is demonstrated by means of field and laboratory data of four selected soil profiles. The high CEC of the firm saprolite is distributed over all grain sizes, and is more and more restricted to the clay fraction during plasmatization. 相似文献
12.
以苜蓿、红豆草两种植物篱为研究对象,对黄土丘陵沟壑区坡耕地布设植物篱后不同坡位土壤颗粒含量的变化、土壤分形维数进行研究,分析了植物篱对土壤颗粒组成的影响。结果表明:（1）同坡面相比,中坡及下坡土壤极细沙粒与粗粉粒含量增加,细粉粒与黏粒含量减少,出现相对于上坡的土壤机械组成粗化现象,且下坡粗化程度大于中坡;（2）相对于对照坡面,植物篱坡面各坡位粗化现象均得到缓解,红豆草对土壤颗粒的影响在上坡表现明显,苜蓿的影响在下坡表现明显;（3）坡面土壤分形维数呈现上部 > 中部 > 下部,苜蓿 > 红豆草 > 对照样地;（4）土壤颗粒与土壤分形维数的相关性分析显示,土壤分形维数与极细沙粒、粗粉粒呈极显著（P < 0.01）负相关,与黏粒呈显著（P < 0.05）正相关。 相似文献
13.
This paper deals with the effects of soil erosion on the horizontal and vertical distribution of nutrients in loess soil topo-sequences in southern Lower Saxony and Frankonia (W. Germany). Each topo-sequence consists of three parts: an upper plateau (or edge of a piedmont plain) with little soil erosion up to now, a slope which as a whole has been eroded very much, and a slope foot which is covered with colluvial sediments. Compared to the pure loess the soils contain more K, Na, and P, and less Ca. The distribution of the nutrients within the investigated topo-sequences is caracterized by high contents of potassium on the slopes, provided that the A1-horizon is eroded, so that the B1-horizon has come to the surface. Finally it is considered whether the erosion-made differentiation of nutrients has negative or positive consequences on the productiveness of the arable soils. 相似文献
14.
J. M. van Mourik 《CATENA》1999,35(2-4)
Humic horizons of soil profiles often contain pollen and spores. Comparison of the sequence of pollen associations of soil profiles with pollen zones of reference diagrams offers palyno-ecological information, relevant for reconstruction of landscape ecological development. In palynological studies of semiterrestrial and aquatic deposits, pollen is considered to be part of the sediment and anaerobic conditions in water-saturated deposits promote its conservation. This is not true for pollen in soils. Aerobic conditions in drained soils result in bio-oxidation of unprotected pollen grains. Interpretation of soil pollen associations requires knowledge of the processes of infiltration and conservation of pollen grains in the soil material. Micromorphology is an important technique to investigate these processes. This is demonstrated in a case study of polycyclic slope deposits in Galicia (Spain). The buried cambisols, in pleistocene solifluction deposits, contain post-sedimentary infiltrated pollen. The pollen associations reflect successive phases in soil ecological development. The holocene colluvial deposits contain syn-sedimentary incorporated pollen. The pollen associations reflect environmental conditions during the deposition of colluvial layers. 相似文献
15.
为研究黄土坡面细沟侵蚀规律,探究水流剥蚀能力的室内测算方法,以黄绵土为研究对象,设置2,4,6,8 L/min 4个流量,5°,10°,15°,20°4个坡度,土槽长度为12 m,进行室内径流冲刷试验,得到黄绵土坡面细沟侵蚀的临界沟长和输沙能力,基于二者之间的函数关系,推导出剥蚀能力的计算公式,以此研究不同试验条件下临界沟长、输沙能力和剥蚀能力的变化规律,并验证方法的准确性。结果表明：在设计水力工况条件下,黄绵土坡面细沟侵蚀的临界沟长的变化范围在5.33～11.12 m,且临界沟长随流量和坡度的增加而缩短;输沙能力随流量和坡度的增大而增大;剥蚀能力与流量之间存在明显的线性关系,与坡度之间存在较好的对数关系。试验方法与其他方法相比,操作便捷、结果吻合度高,能较好地确定黄土区细沟侵蚀的剥蚀能力。研究结果可进一步完善黄土坡面细沟侵蚀理论。 相似文献
16.
黄土区城市工程建设产生了大量黄土堆填边坡,因其结构松散,缺乏必要防护,水土流失严重。该研究基于野外调查,设计室内堆填边坡降雨冲刷模型试验,分析其侵蚀破坏过程中含水率和基质吸力的响应变化规律,结合水土动力学原理,分析了降雨切沟侵蚀阶段沟坡坍塌破坏机理,并揭示了坡度对侵蚀产沙量的影响。结果表明：1）随坡度增大,坡顶含水率饱和速率加快,边坡基质吸力响应速率先增后减,且在40°范围内响应速率最快,在此坡度附近需更加注重坡面防护和坡脚排水。2）切沟侵蚀阶段,沟坡坍塌破坏为水力-重力复合侵蚀过程,且坡度越大,越容易达到临界破裂角,沟坡重力侵蚀现象越普遍。3）黄土堆填边坡在极端降雨条件下,其临界坡度在41°附近。该研究成果可为黄土区工程堆积体的地质灾害防治及水土流失综合治理提供理论支持。 相似文献
17.
Seven Quaternary profiles from the Mediterranean region of northern Tunisia are described and their geomorphological significance assessed. Fifteen radiocarbon datings permit the field observations to be arranged in a chronosequence.The results indicate that the Late Pleistocene period witnessed the production and displacement of coarse debris, a process extending down to low altitudes. Until now, however, the only evidence for this has been found in the vicinity of steep slopes or rock walls. The coarse sediments partly overlie slope deposits derived from reddish soils; to some extent they contain fine reddish pedogenic material, and in part they are covered by it.In the Holocene, the displacement of fine alluvial sediments alternated several times with the formation of humic horizons. Anthropogenic influences on landscape evolution must be admitted as a possibility as from at least three thousand years ago.The aeolian sands of the Late Pleistocene and Middle Holocene are correlated with regressions of high sea levels. 相似文献
18.
半干旱黄土丘陵区不同坡位退耕还林还草地土壤养分的变异规律 总被引：3，自引：1，他引：3
在宁南山区黄土丘陵区开展了退耕还林还草工程效益监测研究,测定了不同坡位退耕还林还草地的土壤养分。对土壤养分单因子分析结果表明:在同一坡面上,随着坡位的降低,退耕还林还草地0—100 cm土层土壤有机质、全氮、全磷、速效氮、速效磷平均含量增加;从不同坡位退耕还林还草地各层土壤养分含量来看,随着土层深度的增加,土壤有机质、全氮、全磷、速效氮、速效磷、速效钾含量在降低。说明半干旱黄土丘陵区林带间种植的苜蓿经营粗放,加剧了土壤养分的失调。 相似文献
19.
在野外模拟降雨条件下,研究了黄土粒度分布和微结构在降雨前后的变化及其对泥流启动的影响.结果表明,采自径流沉积物的降雨后土样中的细黏粒、粗黏粒体积含量分别相对增加了22％和18％,而粗粉粒、微砂体积含量分别相对减少了7.6％和3.3％.坡面残余土的粒度“粗化”,降雨后土骨架连接松散,这些由降雨引起的黄土的粒度和微结构变化说明降雨后黄土的抗剪强度和抗压能力将降低,导致泥流启动的可能性增加.随着降雨入渗,当沿坡面的黄土重力分力与抗剪强度间的平衡被打破,黄土开始滑移并发展成泥流.有效防止坡面土粒度“粗化”是遏制水土流失的关键. 相似文献
20.
为给森林对流域减流减沙效益的预测和评价提供科学依据,采用“环刀法”,在流域的横断面上设点,对黄土丘陵区森林小流域和荒坡草灌小流域土壤水分入渗特征进行了研究。结果表明:森林小流域林地土壤入渗速率显著高于荒坡草灌小流域。在2种小流域类型中,阴坡的土壤入渗速率一般高于阳坡,其中森林小流域阴、阳坡的差异较小,仅在坡上部表现明显,稳定入渗速率分别为7.8mm/min和7.0mm/min;荒坡草灌小流域阴坡的土壤入渗速率高于阳坡,这与阴坡植被发育较好有关。在坡位上,表现出从坡上部到坡下部,土壤入渗速率随坡位下移呈逐渐降低的趋势,即其空间特征为坡上部>坡中部>坡下部。据分析,这是上部产生的径流挟沙而下,在下部沉积,堵塞土壤孔隙,并在表层形成一个致密层的结果。根据黄土丘陵区的土壤特性,其土壤入渗过程以方正三方程拟合精度最高,如将其与A.Kostiakov方程结合使用 ,则可更好地说明土壤的初始入渗速率和稳定入渗速率。 相似文献