SOILS OF THE STATE OF BAHRAIN

The State of Bahrain lies in the arid zone on the southern side of the Arabian Gulf. The factors influencing soil formation on the Islands are examined and an account given of the soils. These can be placed in four groups: Solonchaks, Regosols, Yermosols and Fluvisols. The Solonchaks of the northern plain contain unprecedented amounts of gypsum which, in the absence of leaching, give rise to a variety of morphological features. The distribution of Regosols, Yermosols and Fluvisols can be related closely to physiographical location throughout the country.     

Composition of phototrophs in different soil types of Astrakhan oblast

The composition of phototrophic organisms has been studied in light chestnut soils (Cambisols), alluvial meadow soils (Fluvisols), brown semidesert soils (Calcisols), sandy soils (Arenosols), and solonchaks (Solonchaks) of Astrakhan oblast. Representatives of the Cyanobacteria phylum constitute 71.3% of the total number of studied soil phototrophs. Overall, 64 species of cyanobacteria have been identified; they belong to 3 classes (Chroococceae, Chamaeciphoneae, and Hormogoneae), 4 orders (Chroococcales, Pleurocapsales, Nostocales, and Oscillatoriales), 9 families, and 19 genera. Most common species include Phormidium faveolarum, Phormidium tenue, Phormidium retzii, Phormidium ambigum, Phormidium inundatum, Phormidium bohneri, Oscillatoria woronchnii, Oscillatoria mucicola, Gloeocapsa magma, Gloeocapsa minuta, Anabaena variabilis, and Plectonema nostocorum. The assessment of similarity of the species composition of cyanobacteria and green algae in the studied soil types using the Jaccard and Sorensen similarity coefficients demonstrates that the maximum similarity coefficient reaches 0.37–0.54 for cyanobacteria and 0.67–0.80 for green algae. The high diversity of cyanobacteria and green algae denotes an important role of phototrophs in the processes of soil formation in the studied soils.     

Are There Arid Land Soilscapes in Southwestern Europe?

No studies have proven the existence of soil assemblages typical of arid lands in Europe. This study was carried out in a representative territory of the southeastern part of the Iberian Peninsula, Almería province, which is the driest part of Europe, to determine if soils characteristic of arid lands are present. In order to analyse the spatial distribution of soils, the authors made use of mathematical tools previously developed in biodiversity and pedodiversity analysis, such as richness, entropy indices, abundance distribution models, diversity‐area relationships and nested subset analysis. The study demonstrates that the soil types or pedotaxa are typical of mountainous arid lands. Shallow and weakly developed soils (e.g. Leptosols, Regosols and Arenosols), Calcisols, Gypsisols and Solonchaks, cover most of the study area, and pedodiversity analysis demonstrates that the pedotaxa spatial patterns follow the same regularities as in other areas, environments and scales. In view of the fact that the class of landscapes identified in this study is unique in Europe, the Tarbernas desert and other arid lands sites of the study area merit preservation as part of the European geological, geomorphological and pedological heritage. Copyright © 2015 John Wiley & Sons, Ltd.     

Soils of a dune coastal salt marsh system in relation to groundwater level,micro-topography and vegetation under a semiarid Mediterranean climate in SE Spain

Twenty-one soil profiles were described, analysed and classified in a salt marsh dune system in SE Spain. Sites for sampling were selected according to micro-topographical positions and vegetation types. The pedons showed an A–C type profile. Most of the profiles at summit positions had a microbiotical crust in the upper centimetres, formed by fungal mycelia that contribute to agglutination of sand particles. In two soils, a buried Ab horizon could be identified. Soils at inter-dune depressions showed redoximorphic features with diffuse boundaries, therefore indicating the actual activity of the oxidation–reduction processes. The presence of remains of Posidonia oceanica buried in many of the profiles indicates both a progressive regression of the shoreline and the accretion of the dune system. Sand grains were the most abundant size fraction (generally higher than 65%). Salinity strongly increased at the depressions, with Cl⁻, SO₄²⁻, Na⁺ and Mg²⁺ being the most abundant ions. The microtopographical position at the dune had more influence on the vegetation cover and the soil type than did the distance to the shoreline. Most of the profiles at summit sites were colonised by trees (Pinus halepensis and Juniperus phoenicea subsp. turbinata), shrubs (Pistacea lentiscus, Rhamnus lycioides), thyme-brushwoods (Crucianella maritima, Teucrium dunense) or grasses (Ammophila arenaria), and they were classified as Arenosols or Torripsammens. The slopes of the depressions were dominated by Schoenus nigricans, living on Gleysols or Halaquepts and Aquisalids, or Limonium cossonianum, living on Solonchaks or Aquisalids. Juncus maritimus occupied footslope or bottom positions of the depressions, growing on Solonchaks or Aquisalids and Gleysols or Halaquepts. The succulent halophytes Arthrocnemum macrostachyum and Sarcocornia fruticosa were typical species at bottom positions, living on Solonchaks and Fluvisols or Aquisalids. In two of the profiles at interdune depressions a petrocalcic horizon appeared.     

Long-term Monitoring and Prediction for Leachate Concentrations in Shanghai Refuse Landfill

The two soil profiles of Al-Ahmadi and Burgan oil fields are alkaline aridsoils with similar pH values and bicarbonate contents. Differences betweenthe carbonate (CaCO₃), exchangeable cation and sulphate contents of the twosoil profiles are attributed to the diversified sources of the soils. Carbonateincrements in topsoils of both profiles were probably derived from the newsand dunes formed after the Gulf War and migrated to the vicinity of thestudy area. Elevated concentrations of calcium, magnesium and potassiumcations in topsoils were most probably supplied from the cation-rich formationwater associated with the oil spilled in the two fields.The values of pH, electrical conductivity and sodium adsorption ratio forthe two soil profiles classify them as saline soils. The high and similarproportions of sodium and chloride ions adsorped in the topsoils and the highsalinity of both profiles indicate the accumulation of salts due to the floodingof soils by formation water and sea water used in controlling well fires. Thedownward oil/water movement and salt accumulation are restricted to theupper (25–95 cm) layer in the Burgan soil profile, whereas oil/water gangliaand associated salts spread over greater depths (150–270 cm) in Al-Ahmadiprofile due to variations in the sorting, structure and hydraulic conductivity ofthe two soils. The sharp decrease in salt concentration below the Gatch(caliche) layer suggests that this layer acts as a moisture barrier impeding anyfurther downward movement for oil/water and associated salts.Gypsum is the prime source of sulphate concentrations in the lower layersof the two soils. The flooding of oil fields by oil lakes containing sour crudeand the dry deposition of SO₂ gas emitted as soot from the burnt oil couldprovide source to the sulphate concentrations in the topsoils of both profiles.     

Soils of the Manas River Area in Northern Xinjiang,Peoples Republic of China

The Manas River Valley is situated in the centre of the continental landmass of Asia. The natural conditions in this region on the northern slope of the Tian Shan Mountains are characterized by an arid climate in an temperate geographical position (N 43°–46°, E 85°–87°), with extreme cold winters and high temperatures in summertime. The rivers, which are fed by glaciers, were formerly bordered by gallery forests (Tugais) along their main parts. There occurs an altitudinal sequence of soils but also a high variability within the same altitude due to changes of rocktype, relief, landuse and age of land surface. All the northern mountain slopes are mainly covered by loess deposits. The former forest-steppe Kastanozems and semidesert Xerosols are affected by severe erosion, which destroyed the former zonality there. In the transition zone to the desert, a quick change in the inclination, in the parent material (from loessial deposits to fine-textured alluvial quarternary deposits) and in the water supply (the groundwater rises up to the soil surface) take place. For this reason the Xerosol-Yermosol soil landscapes include soils like Gleysols, Solonchaks, Solonetz, Fluvisols and also Regosols. The great contrasts between winter and summer temperatures, the occurence of high temperatures when water supply is good and fine textured soils with high evaporation lead to the development of very fertile sites. They have a humusrich good structured topsoil, a favourable root penetrability and a high water capacity. On the other hand these soils are under natural and cultivated conditions affected by serious salinization in some parts of the area.     

Morphogenetic features of soils in the Cat Tien National Park,southern Vietnam

Morphogenetic features of soils on the selected plots in the Cat Tien National Park in southern Vietnam have been studied with the use of a set of morphological, analytical, and instrumental methods. The lithological factor and topographic position play the leading role in the development of the particular genetic soil features. The soils can be subdivided into four groups according to these factors. The soils developing from volcanic deposits with a predominance of tephra can be classified as thin clayey brown tropical soils (Dystric Skeletic Rhodic Cambisols (Clayic)), and the soils developed from less weathered colluvial derivatives of basalts with some admixture of tephra can be classified as dark-humus clayey tropical soils (Skeletic Greyzemic Umbrisols (Clayic)). Very poor soils developed from the eluvium of argillites are classified as thin weakly developed clayey tropical soils (Dystric Regosols (Clayic)). The soils forming from the alluvial sediments of different textures are classified as alluvial loamy sandy soils (Dystric Fluvisols (Arenic, Drainic)) and as alluvial clay loamy soils (Eutric Fluvisols (Episiltic, Endoclayic)).     

Quantitative assessment of pedodiversity and soil erosion within a karst sinkhole in the dry steppe subzone

A detailed study of the soil cover of a sinkhole (300 m²) in the dry steppe landscape of the Bogdinsk–Baskunchak Natural Reserve in Astrakhan oblast has been performed, and the factors of its differentiation have been analyzed. The indices of pedodiversity have been calculated and compared for karst sinkholes in the dry steppe and northern taiga landscapes. Quantitative parameters of the lateral migration of solid soil substances on the slopes of the sinkhole have been determined. The rate of soil erosion decreases from the slope of southern aspect to the slopes of western, northern, and eastern aspects. On the average, it is estimated at 0.4 mm/yr. The average rate of accumulation of solid substances on the lower parts of the slopes and in the bottom of the sinkhole reaches 0.74 mm/yr. A comparative analysis of the soil properties attests to their dependence on the particular position of a given soil within the sinkhole. Downward the slopes of the sinkhole, full-profile brown arid soils (Cambic Calcisols) are replaced by sierozem-like soils (Haplic Calcisols), light-humus poorly developed soils (Luvisols), lithozems (Leptosols), and stratified soils (stratozems, or Colluvic Regosols). The soils within the upper ring-shape soil microzone are more diverse and contrasting with respect to their morphological, physical, chemical, and physicochemical properties. The degree of soil contrasts decreases down the slopes of the sinkhole towards its bottom. The studied sinkhole is characterized by considerable pedodiversity. Quantitative parameters of pedodiversity for the sinkhole in the dry steppe zone are higher than those form the sinkholes in the northern taiga zone.     

Distribution patterns of soluble salts and gypsum in soils under large-scale irrigation agriculture in Central Asia

Abstract

Soil salinization is a serious problem in the arid and semi-arid regions of Central Asia. To address the problems, we analyzed the dynamics and distribution patterns of salts in both rice-based and cotton-based cropping fields in selected farms of southern Kazakhstan and Uzbekistan with special emphasis on the dynamics of gypsum, which had a lower solubility than Na salts, as an index of water-movement regimes in irrigated fields. Most of the rice-based plots and some of the cotton-based plots exhibited no surface accumulation of soluble salts or gypsum because of repeated washing by a huge amount of irrigation water in the former or comfortable drainage in the latter. These soils are probably free from the risk of secondary salinization under present conditions and management practices. In contrast, uncultivated plots near canals accumulate both soluble salts and gypsum in the surface soil layers, and these salts would not be leached out without a drastic change to a predominantly downward pattern of water movement. In the intermediate stages in terms of soil salinization, some soils accumulated substantial amounts of soluble salts in surface layers but relatively low amounts of gypsum. In this case, periodic irrigation could have washed out most of the gypsum and soluble salts in a downward direction and, consequently, it is possible to leach out the accumulated soluble salts by applying additional irrigation water if necessary. However, there were some cases in which soils accumulated large amounts of gypsum in surface layers as well as soluble salts, suggesting that irrigation/drainage is generally insufficient to remove gypsum with a lower solubility and that these profiles are dominated by an overall upward movement of water. For these soils, drainage facilities should be improved to ensure the efficient leaching of accumulated salts on cropping. Thus, the condition of irrigated plots in terms of the direction of water movement and resulting salt regimes can be well understood from the distribution patterns of both soluble salts (or cations) and gypsum.     

Soil carbonation processes as evidence of tillage-induced erosion

Tillage-induced soil erosion or redistribution increases spatial variation of several soil properties and often reduces the productive capacity of soil resources. Our objectives were to identify the extent of this type of erosion by observing the changes in soil morphological properties in the field and analysing its possible effects on soil productivity. The study was initiated in 2001 and conducted at two irrigated sites located approximately at Terena, Alandrol, 80 km east of Évora, Portugal. They were planted to corn (Zea mays L.) during this study, but have a long history of agricultural use with a trend toward increasing intensity in recent years. Soils in the field studies are classified mainly as Calcaric Regosols, Calcaric Cambisols, Luvisols and small areas of Fluvisols. The amount of erosion was estimated by simulation and verified by describing the lithology and measuring soil carbonates. The presence of carbonates in the superficial Ap horizons of soils that were previously devoid of this compound, provide evidence of soil redistribution: (1) in soils derived from calcareous parent material, this is the result of a re-carbonation process; (2) in soils derived from non-calcareous parent material the presence of carbonates in the superficial Ap horizons results from a carbonation process. On both sites, A and B, approximately 17% of the soils sampled were either carbonated or re-carbonated. Carbonation and re-carbonation of soil profiles confirmed that tillage had redistributed the soil-ploughing layer over time. Decreased corn yield was also observed as slope increase. If current agricultural practices are continued in this area, a decrease in soil quality and maximum yield on higher slopes can be expected.     

不同利用方式的苏打盐渍土剖面盐分组成及分布特征

通过野外调查、采样和室内分析,研究了松嫩平原不同利用方式的苏打盐渍土剖面形态特征及可溶盐含量与组成在土壤剖面中的变化。结果表明,土壤的利用方式不同,土壤剖面腐殖质层厚度、耕层和腐殖质层的有机质含量等有明显差异。在围栏草原、旱田、新水田及老水田4个剖面中,土壤可溶盐总量、pH与ESP均是在剖面中部最高,上部和下部较低;可溶盐组成均以K++Na+和HCO 3-、CO23-为主。表明草原围栏、旱田及水田利用均有抑制苏打盐分表聚的作用。放牧草原剖面的可溶盐含量自下向上逐渐增多,盐分表聚非常显著。开垦20余年的水田剖面中,表层土壤的可溶盐总量、pH和ESP值分别降至0.21%、7.56和9.1%,表明苏打盐碱地种稻较草原和旱田利用更有利于土壤脱盐脱碱。     

Salt-Water Dynamics in Soils: Ⅰ. Salt-Water Dynamics in Unsaturated Soils Under Stable Evaporation Condition

A long term simulation test on salt-water dynamics in unsaturated soils with different groundwater depths and soil texture profiles under stable evaporation condition was conducted.Salinity sensors and tensiometers were used to monitor salt and water variation in soils.The experiment revealed that in the process of fresh groundwater moving upwards by capillary rise in the column,the salts in subsoil were brought upwards and accumulated in the surface soil,and consequently the salinization of surface soil took place.The rate of salt accumulation is determined mainly by the volume of capillary water flow and the conditions of salts contained in the soil profile.Water flux in soils decreased obviously when groundwater depths fell below 1.5m.When there was an interbedded clay layer 30cm in thickness in the silty loam soil profile or a clay layer 100cm in thickness at the top layer,the water flux was 3-5 times less than in the soil profile of homogeneous silty loam soil.Therefore,the rate of salt accumulation was decreased and the effect of variation of groundwater depth on the water flux in soils was weakened comparatively.If there was precipitation or irrigation supplying water to the soil,the groundwater could rarely take a direct part in the process of salt accumulation in surface soil,especially,in soil profiles with an interbedded stratum or a clayey surface soil layer.     

Entwicklung,Eigenschaften und Klassifikation von Dünenböden der Ostfriesischen Inseln – am Beispiel Spiekeroogs

Pedogenesis, properties, and classification of dune soils of the East Frisian Islands (southern North Sea coast of Germany)—exemplified by the island Spiekeroog The aim of this study was a detailed pedological investigation and exact classification of dune soils of the East Frisian Islands. The following soil‐forming processes were identified on a laboratory‐data basis: humus accumulation and dislocation, carbonate loss, acidification, modification of exchangeable cations, and base‐saturation decrease. A slight iron oxide accumulation was visible in the field, but not confirmed by laboratory data. Applying the qualitatively and quantitatively defined horizons from the German classification, these soils cannot be classified as Regosols, Braunerden, and Podsols but they fit perfectly in the Arenosols as defined in the WRB.     

中国土壤系统分类中盐成土及其相关土壤诊断标准的修订建议

对土壤进行科学分类是土壤资源开发和利用的基础,也是土壤调查制图的基础,在农业生产、土地利用的决策和管理中发挥着重要作用,标志着土壤科学的发展水平.目前国际上土壤分类主要有《美国土壤系统分类》(以下简称《ST》)[1]和《世界土壤资源参比基础》(以下简称《WRB》)[2],我国从1984年开始的中国土壤系统分类研究,也已形成了具有中国特色的《中国土壤系统分类》(以下简称《CST》)[3]成果.这三个分类体系都是以定量化的诊断层和诊断特性为基础的多阶层土壤分类体系.     

Soil matric potential and salt transport in response to different irrigated lands and soil heterogeneity in the North China Plain

Purpose

In the lowland area of the North China Plain (NCP), increasing utilization of brackish water could promote the transformation of precipitation into available water resources, and alleviate the conflict between increase food production and freshwater scarcity. However, the processes of soil water movement and salt migration might be altered, because utilization of brackish water results in frequent changes in groundwater depth and thickness of vadose zone. Thus, it was necessary to understand soil water movement and salt migration when using brackish water for irrigation.

Materials and methods

In this study, soil matric potential (SMP) and total dissolved solids (TDS) at multiple depths were measured in situ to investigate the mechanisms of soil water movement and salt migration at one grassland (site 1) and at three typical irrigated croplands (sites 2, 3, and 4) with different soil textures and groundwater depths in a lowland area of the NCP.

Results and discussion

The study showed that deep soil water and groundwater were recharged generally following heavy precipitation during rainy season. SMP values increased quickly at site 4 due to relatively homogeneous soils, followed by site 3?>?site 2?>?site 1 with an obvious hysteresis response of SMP at multiple depths to precipitation. Soil water mainly moved downward in piston flow, and preferential flow also existed in the soil above 100 cm in the percolation process at four sites. Generally, SMP values followed the order of site 4?>?site 1?>?site 2?>?site 3 and exhibited an inverse trend for TDS, which was mainly due to soil heterogeneity and soil texture in vertical profiles. The differences in SMP among the four sites were mainly due to land use and groundwater depth. There were significantly differences in spatiotemporal distribution of water and salts between homogenous and heterogeneous soils. The processes of infiltration and water redistribution ended quickly in relatively homogeneous soils after heavy rains. However, there was obvious hysteresis in SMP with an increase in soil depth in heterogeneous soils.

Conclusions

Homogenous soils favored water infiltration, salt leaching, and groundwater recharge, and the flow of soil water flow was blocked and salt accumulated significantly in layered soils. The soil water movement and the transformation relationship between water and salt in the vadose zone provided a basis for utilization of brackish water irrigation in lowland region of the NCP.

     

The origin of sulfate salts in soils developed on Maikop clays in the North Caucasus region (According to data of the isotope composition of sulfur)

The ratio of ³²S/³⁴S stable isotopes was determined for soils developed on the Maikop clay sediments in the North Caucasus region in order to study the salt geochemistry in the soils. The soil sulfates were proved to be polygenetic. Three groups (generations) of sulfates of different geneses were distinguished according to their isotopic composition (³⁴S). In the underlying deposits and, partially, in the salt-bearing horizons of the soils, secondary sulfates originated from the oxidation of sulfides contained in the marine clay predominate. In the soil profiles, the sulfates inherited from the parent material (marine clay) are mixed with sulfates arriving with the atmospheric precipitation. The portion of the latter reaches about 30% of the total amount of sulfates in the soils. The salt (gypsum)-bearing horizons were formed in the course of the eluvial-illuvial redistribution of salts to the depth of seasonal wetting. The mobilization of sulfate salts from the underlying deposits and their transport to the upper parts of the soil profile with ascending water flows in the course of evaporation from the soil surface did not play a significant role in the accumulation of sulfates in the studied soils.     

数值模拟盐渍土盐分的季节变化

本文用数值模拟方法对土壤的盐分动态进行了周年的模拟计算.计算中考虑了盐分的沉淀与溶解,地下水位随时间变化等情况.计算结果表明:(1)数值模拟方法能反映季风区土壤盐分的季节变化;(2)雨季的集中降雨更有利于土壤脱盐;(3)地下水位的变化与气象因素的变化相配合影响着土壤水盐运动.