A. A. Dymov

Properties of soils and soil-like bodies in the Vorkuta area

The specific features of the formation of soils and soil-like bodies on technogenic substrates in Vorkuta—a polar city specializing in coal mining—are characterized. According to the new Russian soil classification system, these soils are classified as urbanozems (urban soils) and constructozems (soil-like bodies constructed by humans); the latter are subdivided into recreazems (soil-like bodies of recreation zones) and replantozems (soil-like bodies of reclaimed urban areas with planted vegetation). They are characterized by the increased content of heavy metals and by some alkalization of the upper soil horizons in comparison with the natural background soils. The benz(a)pyrene content in most of the soil samples exceeds the maximum permissible concentration (MPC). The maximum levels of the soil contamination with benz(a)pyrene reach 80 MPCs. According to the total contamination index calculated relative to the background concentrations of the major contaminants, the upper horizons of the investigated soils and soil-like bodies are qualified as ecologically hazardous and extremely hazardous bodies.

Pyrogenic changes in iron-illuvial podzols in the middle taiga of the Komi Republic

The changes in the morphological, physicochemical, and chemical properties of iron-illuvial podzols under middle-taiga dwarf shrub-green moss pine forests in the first months after fires are examined. It is shown that forest fires are accompanied by changes in the morphology of the litter horizons, their compaction, and by changes in the chemical properties of the soils. The data on the polycyclic aromatic hydrocarbons (PAHs) indicate a significant increase in the contents of chrysene, fluorene, naphthalene, pyrene, and anthracene in the Opyr(L) horizon in comparison with the litters in the background pine forest. The total PAH content in the O(F)pyr horizon increases mainly at the expense of di- and tri-nuclear PAHs (naphthalene and fluorene). The mineral soil horizons in the burnt area become enriched in the most mobile amphiphilic fractions of the organic matter, which is seen from the increase in the absolute and relative contents of the hydrophilic fractions, which might be represented by the products of combustion of fresh plant remains and litter.

Soils of the northern part of the Subpolar Urals: Morphology, physicochemical properties, and carbon and nitrogen pools

The morphology and physicochemical properties of mountain-tundra and mountain-forest soils of the Subpolar Urals are analyzed. Gleyic humus-illuvial podburs, in combination with humus-illuvial podburs and raw-humus gleyzems, predominate in the mountain-tundra zone; permafrost-affected gleyzems and peat gleyzems with a shallow (30–50 cm) permafrost table are developed on colluvial fans at the foots-lopes. Iron-illuvial podzols, iron-illuvial svetlozems, eluviated burozems, texture-differentiated podzolic soils with a microprofile of a podzol, and gleyed peat-podzolic soils occur in the mountain-forest zone. The organic carbon and nitrogen pools in the soils considerably vary depending on the soil type and local landscape conditions. The organic carbon pool stored in the upper 50 cm of the soil profile varies from 7.7 to 39.3 kg/m2 in the mountain-tundra soils and from 6.5 to 11.8 kg/m2 in the mountain-forest soils. The corresponding values for the nitrogen pool are 0.4–2.4 and 0.4–0.8 kg/m2, respectively.

Changes in the Organic Matter of Taiga Soils during the Natural Reafforestation after Cutting in the Middle Taiga of the Komi Republic

It has been shown that the distribution features of the hydrophilic and hydrophobic fractions of humic substances (HSs) in the upper genetic horizons of undisturbed podzolic soils and litho-barrier podzols are similar. The concentrations of the separate HS fractions in the mineral horizons are largely determined by the soil mineralogy. In forest litters of secondary phytocenoses developed after the cutting of spruce forests, an increase in the content of hydrophilic compounds has been observed on loamy deposits at a decrease in the portion of lignin-like organic compounds. An increase in the portion of Al-Fe-humus compounds has been revealed in the mineral soil horizons of secondary phytocenoses. It has been proposed to use the degree of hydrophilicity (DH) for characterizing the features of the organic matter in taiga soils. An increase in the content of the fractions of occluded organic matter and that bound to minerals (density of 1.6–2.2 g/cm3) has been observed in the eluvial horizons of a young cutover area.

Soils of postpyrogenic larch stands in Central Siberia: Morphology, physicochemical properties, and specificity of soil organic matter

Morphological features, physicochemical properties, and specific characteristics of the organic matter of cryozems (Cryosols) under postpyrogenic larch forests affected by fires 2, 6, 22, 55, and 116 years ago are considered. The morphological changes in the soils affected by fires are manifested by the burning of the upper organic horizons with preservation of pyrogenic features in the soils for more than a century after the fire. In the first years (2 and 6 years) after the fire, the acidity of the organic horizons and their base saturation become lower. The postpyrogenic soils are characterized by the smaller contribution of the organic horizons to the total pools of soil organic carbon. In the studied cryozems, the organic carbon content is correlated with the contents of oxalate-extractable iron and aluminum. A decrease in the content of water-soluble organic compounds in the soils is observed after the fires; gradually, their content increases upon restoration of the ground cover.

Changes in the temperature regime of podzolic soils in the course of natural forest restoration after clearcutting

The results of temperature monitoring in podzolic soils under the middle-taiga bilberry spruce forest and secondary mixed forest of the Komi Republic performed in 2008–2014 are presented. The changes in characteristics of soil temperature in the litter horizon and in the mineral horizons at the depths of 20 and 50 cm are outlined. It is shown that soil temperature regimes differ under the native spruce forest, young growth, and middle-aged secondary mixed forest. The soils of secondary phytocenoses are warmed up to a greater depth and are characterized by the higher heat supply. The differences are seen in a number of temperature parameters, such as the accumulated temperatures above 5°C and above 10°C at the depths of 20 and 50 cm. The most significant differences between the studied plots manifest themselves in the values of temperature amplitudes during the warm season. Maximum values of daily temperature amplitudes were obtained on the plot under young growth, whereas the soil under the middle-aged mixed forest was characterized by minimum values of daily temperature amplitudes.

Composition and hydrophobic properties of organic matter in the densimetric fractions of soils from the Subpolar Urals

Organic matter features in the upper mineral horizons have been studied for four soils in the Subpolar Urals: humus-illuvial podbur (Entic Podzol), gleyic humus-illuvial podbur (Stagnic Entic Podzol), iron-illuvial podzol (Albic Podzol), and eluviated burozem (Leptic Cambisol). Organic matter pools have been separated by densimetric fractionation. The concentrations of carbon and nitrogen and the relative contributions of separate densimetric fractions to the total content of elements in the upper soil horizons reflect the genetic features of formation of the studied soils. The saturation of organic matter with nitrogen increases with increasing density of the fractions. The proportion of heavy fraction HF1 characterized by a high content of fine silt particles increases in the upper horizons of podburs (Entic Podzol, Stagnic Entic Podzol) and burozem (Leptic Cambisol). The contact wetting angles, which characterize the hydrophobic properties of soils, have been determined for the densimetric fractions and horizons of gleyic humus-illuvial podbur (Stagnic Entic Podzol) and iron-illuvial podzol (Albic Podzol). These values vary from 60 to 88° among the soil horizons and from 22 to 137° among the densimetric fractions. It has been found that the hydrophobic properties of the studied soil horizons are largely determined by the contents of free and occluded organic matter fractions.

Nonspecific organic compounds in peat soils of the Subpolar Urals

Specific features of organic matter, molecular composition and distribution of oxygen-containing nonspecific organic compounds (fatty acids, long-chain aliphatic alcohols, and ketones) were revealed in two peat soils on slopes of the Subpolar Urals: the eutrophic peat soil of the spring mire (Hemic Histosols) and the peat soil of a slope mire (Fibric Histosols). Compounds that can serve as molecular markers for some evolutionary stages of peats were determined for this area. Based on the data obtained, the most probable causes of differences in the composition of organic compounds in the peats studied were found to be the following: environmental conditions, water and mineral regime of bog, and differences in the composition of peat-forming plants.

The impact of clearcutting in boreal forests of Russia on soils: A review

Data on the impact of tree logging in boreal forests of Russia on soils are systematized. Patterns of soil disturbances and transformation of microclimatic parameters within clearcutting areas are discussed. Changes in the conditions of pedogenesis in secondary forests are analyzed. It is suggested that the changes in forest soils upon reforestation of clearcutting areas might be considered as specific post-logging soil successions. Data characterizing changes in the thickness of litter horizons and in the intensity of elementary pedogenic processes, acidity, and the content of exchangeable bases in soils of clearcutting areas in the course of their natural reforestation are considered. The examples of human-disturbed (turbated) soil horizons and newly formed anthropogenic soils on clearcutting areas are described. It is suggested that the soils on mechanically disturbed parts of clearcutting areas can be separated as a specific group of detritus turbozems.