Age and Some Genetic Characteristics of Vertisols in China

The ages of organic matter of some dark-colored horizons and calcareous concretions in some Vertisols from tropical,subtropical and warm-temperate zones of China were studied using radiocarbon dating method.The relationship between soil age and genesis of Vertisols was also expounded based on the study of their genetic characteristics and micromorphological features.The results show that although Vertisols have developed for a relatively long time,their weathering and soil forming process are weak and young with little horizonation.This is closely related to their special grochemical soil forming environment.Low-lying terrain,heavy texture,clay minerals dominated by montmorillonites and alternative drying-wetting climate give rise to the vertic features expressed in intense swelling-shrinking and cracking-closing in soils.As a result,the soil development and soil leaching process are resisted,and the climatic effect on the horizonation is impeded.Moreover,pedoturbation eliminates the horizonation in the upper part of soil profile,and postpones their evolution into zonal soils.So vertisols show certain pedogenic inertia and stay at relatively young developmental stage.Therefore,Vertisols are intrazonal soils dominated by local soil forming factors such as the relief and parent materials.     

Morphogenesis of Vertisols：A Model Study

Studies on Vertisols of Southwes China show that the distribution of organic matter,mechanical compositon,carbonates and spore-pollen in their profiles exhibits a definite differentiation and the radiocarbon age has a functional variation with soil depth,which sugests that pedoturbation model is a kind of incomplete model for genetic study and that the distubance and inversion of solums of Vertisol are not as rapid and absolute as expected.In further consideration of the characters of swelling pressure and shear strength of Vertisol,vertic soil and other zonal soils.it is speculated that soil mechanics model is more adaptable for interpreting the morphogenesis of vertisols without any contradiction with soil properties.     

中国土壤分类法中铁铝土的分类

The development of the classification of ferrallitic soils in China is reviewed and the classification of Ferralisols and Ferrisols in Chinese Soil Taxonomy is introduced in order to discuss the correlation between the ferrallitic soil classification in the Chinese Soil Taxonomy and those of the other soil classification systems. In the former soil classification systems of China, the ferrallitic soils were classified into the soil groups of Latosols, Latosolic red soils, Red soils, Yellow soils and Dry red soils, according to the combination of soil-forming conditions, soil-forming processes, soil features and soil properties. In the Chinese Soil Taxonomy, most of ferrallitic soils are classified into the soil orders of Ferralisols and Ferrisols based on the diagnostic horizons and/or diagnostic characteristics with quantitatively defined properties. Ferralisols are the soils that have ferralic horizon, and they are merely subdivided into one suborder and two soil groups. Ferrisols are the soils that have LAC-ferric horizon but do not have ferralic horizon, and they are subdivided into three suborders and eleven soil groups. Ferralisols may correspond to part of Latosols and Latosolic red soils. Ferrisols may either correspond to part of Red soils, Yellow soils and Dry red soils, or correspond to part of Latosols and Latosolic red soils.     

Classification of Ferrallitc Soils in Chinese Soil Taxonomy

The development of the classification of ferrallitic soils in China is reviewed and the classification of Ferralisols and Ferrisols in Chinese Soil Taxonomy is introduced in order to discuss the correlation between the ferrallitic soil classification in the Chinese Soil Taxonomy and those of the other soil classification systems.In the former soil classification systems of China,the ferrallitic soils were classified into the soil groups of Latosols,Latosoilc red soils,Red soils,Yellow soils and Dry red soils,according to the combination of soilforming conditions,soil-forming processes,Soil features and soil properties.In the Chinese Soil Taxonomy,most of ferrallitic soils are classified into the soil orders of Ferralisols and Ferrisols based on the diagnostic horizons and /or diagnostic characteristics with quantitatively defined properties.Ferralisols are the soils that have ferralic horizon,and they are merely subdivided into one suborder and two soil groups.Ferrisols are the soils that have LAC-ferric horizon but do not have ferralic horizon.and they are subdivided into three suborders and eleven soil groups.Ferralisols may correspond to part of Latosols and Latosolic red soils.Ferrisols may either correspond to part of Red soils,Yellow soils and Dry red soils,or correspond to part of Latosols and Latosolic red soils.     

福建省变性土的性质、形成和肥力

The zonal soils in the south subtropical zone of Fujian are lateritic red soils.A type of dark clayey soils.which was historically defined as lateritic red soils,derived from weathering products of the basalts was indicated by the investigation results to be markedly different from lateritic red soils and could be classified as Typical Hapluderts.They are distributed as complex zones with the lateritic red soils.The vertisols in this region were considered as a type of lithogenic soils and the vertic characteristics delay and inhibit the soils from allitic processes and then formed an independent soil type.The vertisols have higher fertility and better agricultural production characters than the lateritic red soils.The different ways in utilizing and managing these soils according to their properties and fertility are also suggested.     

菱镁矿区土壤质量退化研究

Fourteen soil properties in 17 sampling sites were analyzed to study the soil degradation in a magnesite mining area in Haicheng City,Northeast China.Such areas have hitherto received little attention.The current practices of magnesite mining in this area resulted in degradation of soil quality and specifically led to an increase in soil pH,the ratio of magnesium to calcium,bulk density,clay dispersibility,total magnesium and equivalent calcium carbonate and a decrease in surface soil porosity and available phosphorous.The soil quality in the areas affected by intensive mining activity was obviously worse than that of areas far away from the mine.Four factors were identified and "magnesium factor","pH factor" and "fertility factor",involving 13 soil properties,explained 82% of the total variance in the entire data set.Discriminant analysis showed that the total magnesium,water-soluble calcium and available phosphorous were the most sensitive indicators for soil quality.     

Alberta油砂地区在两种水文流域森林土壤酸化敏感性研究

Input of large amounts of N and S compounds into forest ecosystems through atmospheric deposition is a significant risk for soil acidification in the oil sands region of Alberta. We evaluated the sensitivity of forest soils to acidification in two watersheds （Lake 287 and Lake 185） with contrasting hydrological regimes as a part of a larger project assessing the role of N and S cycling in soil acidification in forest ecosystems. Fifty six forest soil samples were collected from the two watersheds by horizon from 10 monitoring plots dominated by either jack pine （Pinus banksiana） or aspen （Populus tremuloides）. Soils in the two watersheds were extremely to moderately acidic with pH （CaCl2） ranging from 2.83 to 4.91. Soil acid-base chemistry variables such as pH, base saturation, Al saturation, and acid-buffering capacity measured using the acetic acid equilibrium procedure indicated that soils in Lake 287 were more acidified than those in Lake 185. Acid-buffering capacity decreased in the order of forest floor 〉 subsurface mineral soil 〉 surface mineral soil. The most dramatic differences in percent Ca and Al saturations between the two watersheds were found in the surface mineral soil horizon. Percent Ca and Al saturation in the surface mineral soil in Lake 287 were 15% and 70%, respectively; the percent Ca saturation value fell within a critical range proposed in the literature that indicates soil acidification. Our results suggest that the soils in the two watersheds have low acid buffering capacity and would be sensitive to increased acidic deposition in the region.     

生物表面活性剂及Tween-80在一株菲降解菌降解过程中的作用研究

Numerous studies have been devoted to the physical-chemical weathering processes leading to the creation of unique soil formations having their own history that induce soil-biotic diversity. However, the extent to which unique geomorphic formations influence soil biotic seasonal variation is not clear. Our aim was to define seasonal variations of soil biota in soils of different-aged terraces of the Makhtesh Ramon anticline erosional cirque in southern Israel. The strong effect of Makhtesh Ramon (Ramon Crater) erosional fluvial terrace age initiated by climatic changes during the Late Pleistocene–Early Holocene period on seasonal variations in both soil properties and the abundance and composition of soil biota were demonstrated. However, age dependence was not constant and values for observed soil properties and microbial activity were negligible between younger and older terraces for certain seasons, while free-living nematodes along with bacteria-feeding group were strongly dependent on the geomorphic features of the ages throughout the study period.     

地貌演替序列特征对土壤生物群动态的季节效应

Numerous studies have been devoted to the physical-chemical weathering processes leading to the creation of unique soil formations having their own history that induce soil-biotic diversity. However, the extent to which unique geomorphic formations influence soil biotic seasonal variation is not clear. Our aim was to define seasonal variations of soil biota in soils of different-aged terraces of the Makhtesh Ramon anticline erosional cirque in southern Israel. The strong effect of Makhtesh Ramon (Ramon Crater) erosional fluvial terrace age initiated by climatic changes during the Late Pleistocene–Early Holocene period on seasonal variations in both soil properties and the abundance and composition of soil biota were demonstrated. However, age dependence was not constant and values for observed soil properties and microbial activity were negligible between younger and older terraces for certain seasons, while free-living nematodes along with bacteria-feeding group were strongly dependent on the geomorphic features of the ages throughout the study period.     

中国西南薄层砾石土喀斯特坡地土壤的137Cs分布特点

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.     

黄淮海平原晚第四纪古土壤

本文运用孢子花粉,古生物化石和放射性碳断代等手段,从土壤剖面层段的特征,土壤年龄和环境变化方面证明,分布于黄淮海平原的变性土不是现代土壤,而是古土壤,该古土壤自晚新世晚期以来经历了三次沉积－成土作用旋回,其土壤发育程度较弱,且是由钙质结核土层,暗色土层,表土层和（或）淤土层组成的一个叠置型古土壤。     

我国土壤放射性碳年龄

我国地域辽阔 ,土壤类型众多。土壤中不仅含有有机质和腐殖质 ,而且许多土壤中还含有丰富的钙质结核、分散碳酸盐以及贝壳、珊瑚等可供放射性碳断代的良好对象。土壤有机和无机1 4 C年龄研究表明 ,我国大多数土壤是全新世时期的产物。其中又以全新世中期和晚期的土壤占绝对优势。人为土纲中的土壤年龄与六千余年来我国悠久的农业耕种历史密切相关。相比之下 ,只有少数土壤形成于晚更新世晚期。而另一些土壤有数个形成、发育阶段 ,它们的年龄自然亦就跨越不同的地质时期 ,具有多元化的特点。     

Chrono-toposequences of soils on the river terraces in Transylvania (Romania)

A sequence of surface soil profiles and buried soils described on the 4th, 3rd, 2nd and 1st terraces of different rivers in Transylvania is presented as part of an attempt to perform a paleopedologic interpretation of the dominant soil types of this area. Excepting the first terrace, the described soils were formed from Pleistocene slopewash deposits of Würm, or possibly of Riss age, which overlay alluvial terrace deposits. On the basis of fossil animal remains, periglacial cryostructures, prehistoric artifacts (Coţofeni culture of the transition period from the Neolithic to the Bronze Age) and Scythian graves an approximate age of different soil horizons, as well as the polycyclic nature of soils was established. There is no essential difference between a Würmian buried soil horizon and the argic Bt horizon of the surface soils; moreover, in some cases, the buried paleosols become the Bt horizon itself of the surface soils, through the thinning of the overlying deposits. Even if the possibility of formation of the argic Bt horizons during the postglacial until the end of Neolithic, cannot be excluded, from the presented situations it seems that these horizons in the Transylvanian Basin are Würmian relics, formed in the periglacial interstadials. In most of the cases Bt horizon has nothing in common genetically with the topsoil.     

Transformation of carbonate pedofeatures in paleosols buried under kurgans in the North Caucasus region

Carbonate concentrations in a chronosequence of paleosols buried under kurgans in the North Caucasus region at the end of the 4th century and the first half of the 5th century AD have been studied with the use of a set of morphological and isotopic methods. It is demonstrated that morphologically different phases of calcite—the collomorphic phase and the crystalline phase—in carbonate pedofeatures (calcareous pseudomycelium) and in the calcareous horizon have different elemental compositions and different isotopic compositions of carbon. Hence, these forms of calcite should have different origins. An addition of colloidal carbonates migrating in colloidal solutions from the lower soil horizons to the surface horizons during the periods of climatic aridization to the acicular calcite may be responsible for a sharp and irregular increase in the radiocarbon age of the newly formed carbonate pseudomycelium.     

Holocene geomorphological processes and soil development as indicator for environmental change around Karakorum,Upper Orkhon Valley (Central Mongolia)

Mantles of silt- and sand-size particles, paleosols and fluvial deposits preserve valuable information on Holocene environmental change. These archives were used to reconstruct the landscape history in the upper Orkhon Valley close to the former capitals of the Uighurs (Kharbalgasin Tuur) and the Mongolian Empire (Karakorum) near the recent town of Kharkhorin, Central Mongolia. A holistic approach involving the use of high spatial resolution geomorphological mapping, sedimentological and geochemical analysis, palynology, and geochronology shows several phases of landscape activity and stability in the region. This includes phases of fluvial erosion, aeolian sedimentation, and soil formation. By using luminescence and radiocarbon dating, phases of landscape change, indicated by soil formation, occurred mainly at around 6.5–6 ka. Pollen data and a weakly humic horizon at around 1.0 ka probably indicate enhanced moisture supply in the region and a reduction of human activity between the time of the reigns of the Uighurs (8th–9th century AD) and the Mongols (1220–1388 AD). Since 3 ka, especially within the last two millennia of Historical Time (300 B.C.–present), a more intensified human occupation in the Upper Orkhon Valley occurred in this region. This included a more densely grazing of cattle to supply the growing population demands of the Uighurs and Mongols. This overgrazing caused an increase in erosion and the formation and deepening of fluvial gullies, together with soil deflation and subsequent deposition of aeolian sediments. Human activity, in addition to climate, has been dominant in driving landscape evolution of this region since the late Holocene.     

The 14C age and residence time of organic matter and its lipid constituents in a stagnohumic gley soil

A combination of radiocarbon (¹⁴C) dating and biomarker analyses of the aliphatic hydrocarbons in soil lipids is proposed as a novel and improved method for studying the environmental history of peaty soils. The radiocarbon concentration of unfractionated bulk organic matter, hydrolysed soil residues and two lipid fractions (the aliphatic hydrocarbons and carboxylic acids) recovered from a stagnohumic gley soil, were compared using AMS (accelerator mass spectrometry) and radiometric ¹⁴C dating techniques. The radiocarbon ages recorded by the aliphatic hydrocarbon fractions were consistently older than those measured from the unfractionated soil, and were in most cases older than the residues remaining after acid hydrolysis. This pattern was observed at three different depths in the soil profile. The apparent age difference between the hydrocarbon fraction and its unfractionated substrate increased with depth. An abundance of long–chain n–alkanes, similar to those found in higher plant waxes, characterized the aliphatic hydrocarbon fraction from the deepest soil (at 21.5–24.5–cm depth). The radiocarbon age of this basal organic component (13470± 170 years bp ) indicated that it derived from the initial re–establishment of vegetation on the local deglaciated landscape with the onset of the Windermere Interstadial (c. 14000–13000 ¹⁴C years bp ). Bulk organic detritus within the basal horizon dated at some 3000 years younger, and presumably as a result of the downward penetration and retention of some mobile organic residues produced later in the development of the soil profile. The survival and apparent stratigraphical stability of these recoverable aliphatic hydrocarbons provides the opportunity, via the development of AMS dating, to measure an unambiguous radiocarbon age for the origin of organic residues retained in soils and sediments.     

Polygenetic development of the Mormon Mesa,NV petrocalcic horizons: Geomorphic and paleoenvironmental interpretations

Mormon Mesa, Nevada, USA is of one of Earth's rare and unique landforms. Regionally, Mormon Mesa is important because of its relationship to the lower Colorado River and its connection to stream incision. Petrocalcic horizons at Mormon Mesa developed from multiple exposure, erosion, and sedimentation events driven by variations in paleoclimate since the early Pliocene. This study utilizes pedogenic features at Mormon Mesa to construct a sequence of development for the soil profile. We sampled and described seven profiles at Mormon Mesa to determine the soil and geomorphic processes that have influenced the development of this geomorphically important soil. The Mormon Mesa soil profile generally consists of four petrocalcic soil horizons from the base upward (transitional, laminar, massive, and brecciated) and an additional set of horizons that formed in unconsolidated surficial eolian sediments. The transitional horizon formed after cessation of Muddy Creek Fm. deposition (~ 5 to 4 Ma) and accumulated calcium carbonate to a stage II–III morphology (maybe IV in some locations). After a period of landform stability, the upper portion of the transitional horizon was exposed and eroded (~ 2.8 Ma). Petrocalcic fragments and stage II pendants that formed in the transitional horizon were exposed on the surface and later mixed with aggrading eolian sediments. After the surface re-stabilized, calcium carbonate accumulated along the underlying discontinuity with the transitional horizon and formed a laminar horizon. Shallower accumulations of calcium carbonate formed pendants on the undersides of the rotated petrocalcic fragments and pendants that had previously been eroded from the transitional horizon. Continued rooting and bioturbation caused rotation and multiple directions of pendant formation. Today, in plan view, these pendants appear concentric and are the pisoliths described by Bachman and Machette [Bachman, G.O., Machette, M.N., 1977. Calcic Soils and Calcretes in the Southwestern United States., USGS: Open-File Report 77–797]. Continued calcium carbonate precipitation eventually plugged the horizon (massive horizon). After the massive horizon became indurated, the upper portion was exposed, fractured, eroded, and mixed with aggrading eolian sediments. These brecciated fragments experienced erosion/brecciation and soil stabilization/cementation with pedogenic calcite multiple times, probably as a result of the Pleistocene glacial/interglacial climate cycles. All of the features described in this study are interpreted to have formed in response to climatic changes that caused either soil erosion with concurrent eolian deposition, or soil development and pedogenic carbonate accumulation.     

珠江三角洲平原不同种植年限土壤铁氧化物特征研究

珠江三角洲平原具有上千年的围垦历史,其土壤发生演变过程深受人为作用影响,开展此区域不同种植年限土壤中铁氧化物形态特征和分布规律的研究,能够揭示人为耕种下土壤发生演变过程。以珠江三角洲平原不同种植年限的土壤剖面为对象,研究了滨海沉积物、河流冲积物和三角洲沉积物发育的土壤及黏粒中全铁、游离铁含量变化及其影响因素。结果表明:随着种植年限的增加,河流冲积物、三角洲沉积物发育土壤中游离铁(Fe_d)向土体下部淀积深度逐渐增加,黏粒中游离铁(Fe_(d(clay)))含量在水耕氧化还原层中呈减小趋势,而滨海沉积物发育的土壤Fe_d含量及淀积深度均有所减小。随着种植年限的增加,滨海沉积物发育的土壤全铁(Fe_t)和游离铁(Fe_d)在黏粒中的富集程度呈增大趋势,而河流冲积物、三角洲沉积物发育的土壤Fe_t和Fe_d富集程度逐渐减小。土壤Fe_d与Fe_t、黏粒游离铁(Fe_(d(clay)))与黏粒全铁(Fe_(t(clay)))均呈极显著正相关;全铁富集率(Fe_(t(clay))/Fe_t)、游离铁富集率(Fe_(d(clay))/Fe_d)均与Fe_(t(clay))、Fe_(d(clay))、黏粒铁游离度(Fe_(d(clay))/Fe_(t(clay)))呈极显著正相关,与Fe_t、Fe_d、土壤铁游离度(Fe_d/Fe_t)、黏粒含量呈极显著负相关,且Fe_(t(clay))/Fe_t与Fe_(d(clay))/Fe_d呈极显著正相关,表明土壤铁氧化物在黏粒中的富集以Fe_d为主,且铁氧化物的富集程度受土壤黏粒含量的影响。