Effect of forest on the composition and properties of organic matter in steppe chernozem soils of neighboring biogeocenoses

Results are presented that have been obtained in studies on the effect of forests growing in the steppe zone on the conditions of formation and qualitative and quantitative composition of organic matter and on the properties of humus in chernozem soils of neighboring biogeocenoses.     

Soil as a factor of vegetation regeneration in natural pastures

Data are presented that show the significance of the humus state of chernozem soils, their amphiphilic (hydrophobic-hydrophilic) components, and related physical properties (density, structural condition, and water permeability) for regeneration of natural vegetation and restoration of its species com-position in pasture ecosystems.     

Ecophysiological indicators of microbial biomass status in chernozem soils of the Central Caucasus (in the territory of Kabardino-Balkaria with the Terek variant of altitudinal zonation)

A comparative assessment of the biological properties of chernozem soils in agro- and biogeocenoses has been made by determining the rates of basal and substrate-induced soil respiration and using these data to calculate ecophysiological indices characterizing the potential and stability of soil microbial biomass. The results show that the rate of CO₂ emission and the contents of microbial biomass carbon in agriculturally exploited chernozem soils have decreased by factors of 3 and 2.6, respectively. The values of microbial metabolic quotients are indicative of medium-to-strong disturbance to the stability of microbial communities in chernozem soils of agrocenoses.     

Ecotoxicity assessment of heavy metals and crude oil based on biological characteristics of chernozem

Soil pollution with Cr, Cu, Ni, and Pb oxides or crude oil has an adverse effect on biological properties of ordinary chernozem. The degrees of their deterioration in laboratory and field experiments do not differ statistically, indicating that the results of laboratory modeling may be correctly extrapolated to the field scale. Pollution of ordinary chernozem with oil affects biological properties of both topsoil and subsoil horizons, while Pb is harmful only for the upper soil horizon. Concentrations in excess of 25 mg/kg for Pb and 0.25% for oil in ordinary chernozem are not ecologically safe (not allowable).     

Effects of heavy metal pollution on the ecological and biological characteristics of common chernozem

A detailed comprehensive study on the effects of heavy metals on the biological activity and other characteristics of common chernozem of the southern European facies was performed. This involved the analysis of various microbiological and biochemical indices characterizing soil biological activity, their dynamics, a set of several metals and their different chemical forms, and a wide range of metal concentrations in the soil. New important aspects of the effects of heavy metals on biological processes in the soil were revealed. An integral method was proposed for assessing changes in the total biological activity of the soil on the basis of informative indices used in the monitoring, diagnosis, and indication of soils polluted with heavy metals. Geographic trends in changes of soil resistance to heavy metal pollution were analyzed within the common chernozem subtype and by comparing chernozem with other soils.     

Effect of phytoremediation in technogenic landscapes of mining areas on the functioning of actinomycete communities

It has been shown that conditions formed in technozems of tailing dumps covered with a layer of chernozem are optimal for the development of soil microflora, including actinomycetes, as follows from their high abundance. The use of Leymus sabulosus (Bieb.) Tzvel in biological remediation of technozems formed in tailing dumps ensures an increase not only in the abundance of microorganisms in edaphotopes but also in their ecological diversity, compared to technozems planted with Rhus hirta (L.) Sudw, as confirmed by 1.2- and 1.9-fold increase in the Margalef and Berger–Parker diversity indices. Therefore, applying a layer of chernozem on technozems of tailing dumps provides for more efficient remediation of technogenic soils.     

The Effect of Soil Cultivation on the Humus State of Gray Forest Soil in the Middle Urals

The results of studies on the humus state of soils in agrosystems of the Middle Urals (1984–1997) are described. It is shown that the change of agricultural technologies (crop rotation, doses of organic fertilizers, etc.) transforms environmental conditions and the direction of humus formation processes. Parameters such as the concentrations of humus and water-soluble carbon and soil potential for humus accumulation reliably characterize the humus state of arable soil and allow the mobility and migration rate of humic substances to be monitored.     

Sensitivity of some groups of ordinary chernozem soil microorganisms to γ irradiation

The effect of γ irradiation at doses of 1, 5, 10, and 20 kGy on the microflora of ordinary chernozem soil has been studied. The time course of the restoration of the microorganism numbers over 180 days after γ irradiation has been studied in model experiments. The microorganism radioresistance decreases in the following order: amylolytic bacteria > Azotobacter > spore-forming bacteria > ammonifiers > micromycetes. A dose of 20 kGy has a 96% suppressing effect on all microorganisms. Model experiments on the restoration of the irradiated soil microflora have revealed different rates of increase in the numbers of microorganism groups depending on the dose and incubation time.     

Paleosols of the Solonchanka IX site and climate of the Transural steppe zone in the fourth century AD

Studies on paleosols under an archaeological landmark of a rare type (a complex of kurgans with “whiskers”) dating from the Early Iron Age (the fourth century AD) have been performed in the steppe zone of the Transural Plateau. The size and shape of third-order soil polygons under stony ridges (“whiskers”) between the kurgans have been described in detail. The results have shown that the paleosol under the kurgans erected at the turn of the Late Sarmatian and Hun times (1600 years ago) is characterized by a higher humus content and deeper location of the carbonate horizon, compared to the recent soil. This indicates that an increase in atmospheric humidity took place in the fourth century AD.     

Ecological Features of Green Strawberry Cenopopulations in the Steppe Transvolga Region

The results of field studies at the Krasnosamarskii Station of Samara State University (the Samara River valley, the subzone of herb–sheep's fescue–feather grass steppes on ordinary chernozem) have shown that the age structure, ecological density, age index, and regeneration capacity of green strawberry cenopopulations depend on the trophic level and moisture content of soil and on the shading and mulching action of litter.     

Environment-forming role of black saxaul, <Emphasis Type="Italic">Haloxylon aphyllum</Emphasis> (Minkw.) Iljin in the Karnabchul Desert

The environment-forming role of desert tree plants has been studied in the light of A.A. Uranov’s concept of phytogenic field using the example of black saxaul, Haloxylon aphyllum (Minkw.) Iljin, in the Karnabchul Desert. It has been shown that the environment-forming influence of this species leads to considerable changes in the light regime, air and soil moisture and temperature regimes, and soil humus and salt contents within its phytogenic field. Consequently, pertinent changes take place in the dynamics of abundance and distribution pattern of the main plant species and wormwood–ephemeral vegetation.     

Spatial Distribution of Heavy Metals and <Superscript>137</Superscript>Cs in Spruce Forest Soil under Conditions of Regional Pollution

The influence of horizontal structure of spruce forest on the spatial distribution of acid-soluble Zn, Cd, Pb compounds and ¹³⁷Cs in the litter and the humus horizon of soddy podzolic soil has been studied in the territory with the regional background level of industrial fallout. It has been found that the distribution pattern of Zn in the forest litter is a result of biogeochemical processes. The litter in fern–wood sorrel microplots contains increased amounts of Zn and Cd, while the contents of Pb and ¹³⁷Cs are decreased. The distribution patterns of Pb and ¹³⁷Cs in the litter are positively correlated with each other, since both elements are deposited from the atmosphere, and similar mechanisms account for their redistribution in the spruce forest ecosystem.     

Soil-to-plant halogens transfer studies 2. Root uptake of radiochlorine by plants

Long-term field experiments have been carried out in the Chernobyl exclusion zone in order to determine the parameters governing radiochlorine (36Cl) transfer to plants from four types of soil, namely, podzoluvisol, greyzem, and typical and meadow chernozem. Radiochlorine concentration ratios (CR) in radish roots (15+/-10), lettuce leaves (30+/-15), bean pods (15+/-11) and wheat seed (23+/-11) and straw (210+/-110) for fresh weight of plants were obtained. These values correlate well with stable chlorine values for the same plants. One year after injection, 36Cl reached a quasi-equilibrium with stable chlorine in the agricultural soils and its behavior in the soil-plant system mimicked the behavior of stable chlorine (this behavior was determined by soil moisture transport in the investigated soils). In the absence of intensive vertical migration, more than half of 36Cl activity in arable layer of soil passes into the radish, lettuce and the aboveground parts of wheat during a single vegetation period.     

Soil-to-plant halogens transfer studies 1. Root uptake of radioiodine by plants

Long-term controlled experiments under natural conditions in the field have been carried out in the Chernobyl Exclusion zone in order to determine the parameters governing radioiodine transfer to plants from four types of soils (podzoluvisol, greyzem and typical and meadow chernozem) homogeneously contaminated in the 20-cm upper layer with an addition of (125)I. An absence of (125)I depletion in arable soil layers due to volatilization was noted up to one year after contamination. During one year, depletion due to the vertical migration of radioiodine from the arable layer of each of the soils did not exceed 4% of the total (125)I content. Radioiodine concentration ratios (CR) were obtained in radish roots, lettuce leaves, bean pods, and wheat grain and straw. The highest CR values were observed in podzoluvisol: 0.01-0.03 for radish roots and lettuce leaves, 0.003-0.004 for bean pods and 0.001 for wheat grains. In the other three soils, these values were one order of magnitude lower. The parameters relating to changes in radioiodine bioavailability were determined, based on the contamination dynamics of plants in field conditions.     

Soil organic horizons as a major source for radiocesium biorecycling in forest ecosystems

Here we review some of the main processes and key parameters affecting the mobility of radiocesium in soils of semi-natural areas. We further illustrate them in a collection of soil surface horizons which largely differ in their organic matter contents. In soils, specific retention of radiocesium occurs in a very small number of sorbing sites, which are the frayed edge sites (FES) born out of weathered micaceous minerals. The FES abundance directly governs the mobility of trace Cs in the rhizosphere and thus its transfer from soil to plant. Here, we show that the accumulation of organic matter in topsoils can exert a dilution of FES-bearing minerals in the thick humus of some forest soils. Consequently, such accumulation significantly contributes to increasing 137Cs soil-to-plant transfer. Potassium depletion and extensive exploration of the organic horizons by plant roots can further enhance the contamination hazard. As humus thickness depends on both ecological conditions and forest management. our observations support the following ideas: (1) forest ecosystems can be classified according to their sensitivity to radiocesium bio-recycling, (2) specific forest management could be searched to decrease such bio-recycling.     

Levels and transfer of Po and Pb in Nordic terrestrial ecosystems

Recent developments regarding environmental impact assessment methodologies for radioactivity have precipitated the need for information on levels of naturally occurring radionuclides within and transfer to wild flora and fauna. The objectives of this study were therefore to determine activity concentrations of the main dose forming radionuclides ²¹⁰Po and ²¹⁰Pb in biota from terrestrial ecosystems thus providing insight into the behaviour of these radioisotopes. Samples of soil, plants and animals were collected at Dovrefjell, Central Norway and Olkiluoto, Finland. Soil profiles from Dovrefjell exhibited an approximately exponential fall in ²¹⁰Pb activity concentrations from elevated levels in humus/surface soils to “supported” levels at depth. Activity concentrations of ²¹⁰Po in fauna (invertebrates, mammals, birds) ranged between 2 and 123 Bq kg⁻¹ d.w. and in plants and lichens between 20 and 138 Bq kg⁻¹ d.w. The results showed that soil humus is an important reservoir for ²¹⁰Po and ²¹⁰Pb and that fauna in close contact with this media may also exhibit elevated levels of ²¹⁰Po. Concentration ratios appear to have limited applicability with regards to prediction of activity concentrations of ²¹⁰Po in invertebrates and vertebrates. Biokinetic models may provide a tool to explore in a more mechanistic way the behaviour of ²¹⁰Po in this system.     

Leaching of nickel and copper from soil contaminated by metallurgical dust

The paper presents the results of the laboratory percolation experiment simulated soil contamination by emissions from a Ni-Cu smelter. Humus (Ao horizon) columns were transferred to lysimeters from an illuvial, humic, ferriferous forest podzol site. Fine metallurgical dust containing Ni and Cu was layered on the columns and irrigated with sulphuric acid solutions at pH 3, 4, 5, and 6. Irrigation for 19 months indicated that the leaching of metals down the humus column was greatest at pH 6. Calculations indicated that it would take 160-270 years for complete leaching of Ni from the Ao layer, and 100-200 years for Cu, depending on the dust composition. Natural decontamination of affected soils will take centuries.     

Transformation of ecological conditions of soil and humus substance formation in the urban environment

Ecological conditions of soil formation and specific features of humus substance formation are considered with regard to urban soils of different types formed in the following functional zones: the park zone, residential area, and sanitary protective zone of the Middle Ural Copper-Smelting Plant. The specificity of soil formation in Revda, a typical industrial city of the Middle Urals, is determined by the combined effect of urban and technogenic factors (urbogenesis and technogenesis), with the former being of primary importance. At a constant period of biological activity, the depth of humification is primarily a function of granulometric and chemical composition of urban soils.Translated from Ekologiya, No. 1, 2005, pp. 11–19.Original Russian Text Copyright © 2005 by Meshcheryakov, Prokopovich, Korkina.     

三峡库区不同林型土壤的入渗能力研究

利用环刀入渗法,观测了三峡库区山地不同海拔地段森林土壤的入渗过程,对比分析了典型林型下土壤各发生层的入渗率和常用入渗模型的适宜性。结果表明：不同林型下土壤入渗能力的差异在各发生层内表现不一致;腐殖质层和淋溶淀积层的入渗率差异相似,温性落叶阔叶林山地棕壤<常绿落叶阔叶混交林山地黄棕壤<暖性针叶林山地黄壤,入渗主要受土壤质地的影响,质地较重的粉壤土入渗能力比质地较轻的砂质黄壤差;母质层则相反,山地棕壤>山地黄棕壤>山地黄壤,黄壤母质风化度低,土壤密度大,渗透性能较差;同一林型土壤的不同发生层相比较,山地棕壤和山地黄棕壤的入渗能力随土层深度增加而增大,腐殖质层<淋溶淀积层<母质层,而山地黄壤则呈相反趋势。温性落叶阔叶林山地棕壤和常绿落叶阔叶混交林山地黄棕壤的入渗率随时间下降明显,而暖性针叶林山地黄壤降低幅度较小,趋于稳定入渗的时间较短。入渗曲线拟合显示,Horton方程对3种森林土壤入渗过程的模拟效果较好,是描述三峡库区森林土壤入渗过程的适宜模型