Genesis and classification position of automorphic soils developed from mantle loams in the northern taiga of European Russia

Automorphic loamy soils of the northern taiga and forest-tundra zones in the northeastern part of European Russia are characterized. These soils are diagnosed by the presence of a paragenetic system of the podzolic (often, with gley features) and iron-illuvial horizons combined with a specific cryometamorphic CRM horizon. The podzolic horizon is considerably impoverished in the total and oxalate-extractable iron and slightly impoverished in aluminum and clay in comparison with the iron-illuvial horizon. A distinctive feature of the cryometamorphic horizon is its fine angular blocky, ooidal, or granulated structure in the dry state and curdled cryogenic structure in the wet state. The soil profile is relatively weakly differentiated with respect to the contents of clay and sesquioxides. The genesis of these soils is related to a combination of the gley-Al-Fe-humus mobilization, migration, and illuvial accumulation of substances and the cryogenic structuring. According to the new Classification and Diagnostic System of Russian Soils, these soils fit the criteria of iron-illuvial svetlozems in the order of cryometamorphic soils. In the studied area, these soils are found together with texture-differentiated gley-podzolic soils having the Bt horizon and belonging to the order of texture-differentiated soils.     

Cryometamorphic gleyzems in the taiga of Western Siberia: Chemical and mineralogical properties,ecology, and genesis

Earlier studies showed considerable differences in the properties of automorphic loamy soils developing under middle-taiga vegetation in Western Siberia and on the Russian Plain. It was found that the soils without clear features of textural differentiation are common in Western Siberia. In particular, they are represented by cryometamorphic gleyzems. In this study, we analyze the properties of a cryometamorphic gleyzem in the Vakh area (the Khanty-Mansi Autonomous Okrug). The distribution pattern of clay minerals in the soil profile is analyzed in relation to the specific features of the soil hydrothermic regime. In the upper mineral horizons, the clay fraction is enriched in minerals of the group of soil chlorites and somewhat depleted of labile phyllosilicates. In the cryometamorphic horizon and in the underlying permafrost, the degree of crystallization of the clay minerals somewhat decreases. An even distribution pattern of aluminum oxide in the soil profile is explained by the increased content of Al in the clay fraction from the upper horizons combined with the loss of Al from the coarse fractions (as judged from data on the bulk elemental composition of clay-free samples). These features can be explained by the specificity of the hydrothermic regime of the cryometamorphic gleyzems with late thawing of the soil profile and frequent phase transitions of soil water in the upper humus and middle-profile cryometamorphic horizons.     

Specific features of soil formation in the taiga zone of Western Siberia

Specific features of soil formation in the taiga zone of Western Siberia are considered. The polygenetic nature of podzolic and gley-podzolic soils in the middle taiga zone, soddy-podzolic and soddy gley soils in the southern taiga zone, and meadow soils in the subtaiga zone is related to the pre-Holocene transformation of the lithogenic matrix upon activation of denudation and accumulation processes and the complicated Holocene evolution of these soils. A soil profile can be subdivided into separate layers according to the geomorphic features of the cryogenesis, the indices of interruption of soil formation, and the differences in the composition of the organic matter in the relict and modern humus horizons.     

Automorphic soils of the central and southern Timan Ridge

Automorphic loamy soils developing from different parent materials in the central and southern parts of the Timan Ridge are described. Pale-podzolic soil and iron-illuvial texture-differentiated svetlozems are developed from silty covering loams underlain by moraine deposits. Podzolic, iron-illuvial, cryometamorphic, and clay-illuvial horizons are distinguished in the svetlozems; soils with such a complex morphology have been described in the taiga zone of European Russia for the first time. Humus-iron-illuvial podzols are developed from acidic slates. Raw-humus rzhavozems (iron-metamorphic soils) are developed from substrates with the high content of pebbles of mafic rocks. Such soils are typical of the middle taiga zone of Central Siberia and the south of Far East. In the northwestern part of European Russia, these soils occupy small areas.     

Polycyclic aromatic hydrocarbons in background podzolic and gleyic peat-podzolic soils

The qualitative and quantitative composition of polycyclic aromatic hydrocarbons (PAHs) has been determined in the background podzolic and gleyic peat-podzolic soils of the middle and northern taiga zones of northeastern Europe using the methods of highly efficient liquid chromatography and chromato-mass spectrometry. The distribution of polyarenes in the soil profiles follows the eluvial-illuvial pattern. Organic and illuvial horizons are the biogeochemical barriers for PAHs migrating in the soils. The revealed regularities of the accumulation and redistribution of PAHs in the soil profiles are in agreement with the character of the soil-forming processes in the northern and middle taiga zones.     

The role of soils in the regional carbon budget of pine forests in Karelia

The carbon pool and its fluxes were studied in Karelian pine forests of automorphic sites for the characterization of the regional carbon cycle. On the permanent sample plots arranged in pine stands (dominant forest types) of the middle and northern taiga, the structure and dynamics of the phytomass, as well as the composition of the soil organic matter, were investigated. The contribution of different components of the forest ecosystems to the regional carbon budget was studied. The carbon pools in the soils of the middle and northern taiga subzones were 330–440 × 10² and 440–550 × 10² kg/ha, respectively. The share of soil carbon in the total carbon pool of the forest biogeocenoses studied amounted to 46–35 and 33–24%, respectively. The period of considerable carbon fixation in the pine ecosystem (nearly 20 × 10² kg/ha/yr) turned out to be limited to the middle-aged stands. In the mature and overmature pine forests, only 4 × 10² kg of C/ha/yr were fixed. The main part of carbon in the soil (65–75%) was contained in the illuvial horizons, although its content there was less that 1% as compared to 30–50% in the forest litters. On industrial harvesting of wood, the main reserves of soil carbon are not spent; only the fund of mobile carbon in organic horizons of poor soils is exhausted or carbon accumulates intensely due to the development of continuous plant cover on fertile soils.     

Genetic specificity and geography of taiga soils in the central part of the Baikal region

A specific feature of the development of automorphic taiga soils in the Baikal region is the lack of correspondence between the weak intensity of the soil chemical weathering and the high intensity of the removal of alkaline-earth elements from the soil profile in the form of suspensions. The loss of the clay fraction affects the water-physical properties of these soils and their temperature regime. The areas of different soil types in the northern and middle taiga zones have been calculated on the basis of soil maps of different scales. It is shown that podburs and acid soddy taiga soils predominate in these zones; the area of podzols, which were previously considered to be the dominant soil type in the middle and southern taiga zones, is smaller.     

Modeling of the thermal influence of fires on the physicochemical properties and microbial activity of litter in cryogenic soils

Periodic surface fires in the cryolithozone (the northern taiga subzone) are the main factor determining the qualitative and quantitative characteristics of the soil organic matter. The specific features of the changes in the physicochemical parameters and microbial activity of the organic horizons in the cryogenic soils under larch forests of the northern taiga after the impact of high temperatures were revealed. The temperatures of fires of different intensity were simulated in laboratory conditions. The thermal impact on the litter organic matter during the surface fires may increase the CO₂ emission from the surface of the soil in the postfire communities due to the destruction of organic compounds only for a short time. After fires of high intensity with strong mineralization of the litters, during a period of more than 1 month, the pyrogenic effect on the organic horizons of the soils under the larch forests of the cryolithozone determined the reduction of the CO₂ emissions in the freshly burned areas as compared to the intact stands.     

Specific features of the development of soils of hydromorphic ecosystems in the northern taiga of Western Siberia under conditions of cryogenesis

Differently directed and heterochronous cryogenic processes have contributed to the contrasting soil cover patterns and spatial heterogeneity of the properties of soils in hydromorphic ecosystems of the discontinuous permafrost zone of the northern taiga in Western Siberia. Frost heave and permafrost thawing within ecosystems of highmoor bogs have led to the development of specific cryogenic landforms, such as flat-topped and large peat mounds. A set of cryogenic soils is developed in these ecosystems; it includes different variants of cryozems, gleyzems (Cryosols), and peat soils (Histosols). The distribution of these soil types is controlled by the local topography and thawing depth, other factors being insignificant. Alternation of peat horizons of different types and ages, whirl-like patterns of horizon boundaries, considerable variations in the thickness of soil horizons, and inversions of soil horizons under the impact of frost cracking, frost heave, and cryoturbation are typical of the considered soils. Thawing depth is the most significant factor affecting the thickness of organic horizons, the soil pH, and the degree of decomposition of peat. As a result of the upward movement of bog ecosystems under the impact of frost heave, peat soils are subjected to considerable transformation: peat horizons undergo mineralization, and the thickness of organic horizons decreases; in some cases, eluvial–illuvial differentiation of the mineral horizons takes place, and peat podzols are developed. However, the opposite process of the return of the soils to the bog stage of pedogenesis with peat accumulation may take place in any time in the case of activation of thermokarst processes.     

Rheological features of the coagulative structure of northern taiga peaty podzolic semi-gley soils of the European Northeast

The results of rheological studies using a MCR 302 modular research rheometer of soil pastes of northern taiga peaty podzolic semi-gley soils are presented. It was found that their coagulative structure has weak structural links. They are little resistant to mechanical stress and their stability decreases in the direction from the northern to the extreme northern taiga by about two times. The strongest coagulative links between soil particles characterize the horizons with increased organic contents and the horizons that are transient in terms of granulometric composition, which lie at the border where light deposits shift heavier ones.     

Water-soluble low-molecular-weight organic acids in automorphic loamy soils of the tundra and taiga zones

The formation features of water-soluble low-molecular-weight organic acids (LMWOAs) in a zonal series of automorphic soils on loose silicate rocks from the middle taiga to the southern tundra (typical podzolic, gley-podzolic, and surface-gley tundra soils) were first revealed by gas chromatography mass spectrometry and gas-liquid chromatography. The content of LMWOAs varies within the range of 1–14 mg/dm³, which corresponds to 1–5% of the total carbon of the water-soluble soil organic matter. It has been shown that a subzonal feature of gley-podzolic soils in the northern taiga is the high content of LMWOAs, including primarily the strongest aliphatic hydroxyl acids. Possible mechanisms of their formation and accumulation in soils have been considered.     

Soils on hard rocks in the northwest of Russia: Chemical and mineralogical properties,genesis, and classification problems

Soil formation on hard rocks—nepheline syenite, amphibolite, metamorphized gabbro diabase, and their derivatives—was studied in the mountainous tundra and in the northern and middle taiga zones of the Kola Peninsula and Karelia (in the Kivach Reserve). It was found that the soils developing from these rocks could be classified into three groups: (1) petrozems with the O-M profile (the most common variant), (2) podzols and podzolized podburs on the substrates with an admixture of morainic derivatives of acid rocks, and (3) shallow (<5–10 cm) pebbly soils on the substrates without an admixture of allochthonous material (the rarest variant). In soils of the third group, the pedogenic alteration of the mineral matrix does not result in the appearance of phyllosilicates in the fine fractions if these phyllosilicates are initially absent in the rock. In these soils, the protion of the organic matter, and binding of iron released from the weathered silicate minerals into iron-organic complexes) are virtually undifferentiated by the separate soil horizons because of the very low thickness of the soil profiles. These soils have the Oao-BHFao-M profile; it is suggested that they can be classified as leptic podburs. An admixture of morainic material containing phyllosilicate minerals favors a more pronounced differentiation of the modern pedogenic processes by separate soil horizons even in the case of shallow soil profiles; the intense transformation of phyllosilicates takes place in the soils.     

Soil formation in the quarries for limestone and clay production in the Ukhta region

The soils forming on the overgrowing technogenic dumps of quarries for limestone and clay production were investigated in the northern taiga (the Ukhta region). The soils are formed under sparse herbaceous plant communities. In the soils on calcareous technogenic eluvium and clay dumps, the processes of humus formation and accumulation predominate. In the soils of the clay dumps, the leaching of carbonates is expressed to a greater extent than in the soils of the limestone quarries. The nitrogen content of organic matter is low in the soils on the technogenic lime substrates and very low on the clay ones. Fulvic acids predominate in the humus composition. At the stages of the soil restoration studied, the zonal trend of pedogenesis is manifested only in the humus accumulation. The calcareous technogenic eluvium is found to be more favorable for the development of microbial communities as compared to the clay substrates with their small microbial biomass. However, there are no features pointing to the development of zonal soil profiles. This fact attests that, in the first 20–30 years, the soil-forming potential in the northern taiga is insufficient for the initiation of the zonal processes.     

Hydrocarbons in the background soils of the southern- and middle-taiga subzones of the Komi Republic

The background content of hydrocarbons in soils of the southern and middle taiga has been assessed with consideration for the landscape and geochemical features of the area. Studies of hydrocarbons in soils of the taiga zone have showed that the position in the relief, particle-size distribution, and organic matter content are the main factors determining their content. The geochemical background of hydrocarbons is 50–100 mg/kg in the organic horizons of the soils on cover loams and 17–70 mg/kg in the soils on sandy deposits.     

Soil catenas on denudation plains in the forest-tundra and northern taiga zones of the Kola Peninsula

Morphogenetic features of soils of two catenas developed on sandy to loamy sandy moraine deposits in the forest-tundra and northern taiga zones on denudation plains of the Kola Peninsula are discussed. It is shown that these catenas are similar with respect to the major directions of soil formation, regularities of soil distribution by the elements of mesotopography, and the factors of the soil cover differentiation. The differences between the catenas are of quantitative character and are related to the intensities of manifestation of the particular processes and features. Both catenas are characterized by the pronounced differentiation of soils with respect to their moistening with hydromorphic peat bog soils in the subordinate positions and Al–Fe-humus podzols in the automorphic positions.     

Soil cover patterns in the Dzhida Depression and their representation on the soil map of 1: 500000 scale

A map of the soil cover patterns in the Dzhida Depression (Baikal region) has been compiled on a scale of 1: 500 000. The grouping of the soil cover patterns into larger categories makes it possible to retain the information contained on large-scale soil maps upon their generalization to the small-scale soil map. The latter displays the regularities of soil distribution at the levels of soil types and subtypes. The areas of the major soil groups have been calculated. It is shown that podburs predominate in the northern taiga ecosystems (72%), whereas acid soddy taiga soils (71%) and podburs (22%) predominate in the middle taiga zone. Minor areas in these zones are occupied by podzolic soils (9%) and permafrost-affected taiga gley soils (14%).     

Soils with complex organic profiles on the Vasyugan Plain

Soils with intricate patterns of their humus profiles developing in the neutral-calcium landscapes of the southern taiga of Western Siberia under highly dynamic paleogeographic, climatic, and weather conditions are characterized. The specific features of these soils comprise the diverse modern humus horizons along with the relic ones of different preservation rates, shallow leaching of carbonates, and a weak development of the middle-profile soil horizons. Specifying these organo-accumulative soils is substantiated by their high humus content against the geochemical background of the clayey calcareous parent rocks. The conjugated series of soils reflect different stages of the soil evolution (the humus profile degradation, the development of eluvial process, and the increase of contrasts in the acid-base conditions) and the hydromorphic transformation accompanied by the formation of organic horizons making the humus profile more complicated. In accordance with the diagnostic horizons, the position of the soils studied was determined in the Classification and Diagnostics of Soils of Russia. The relic enrichment of the humus horizon is proposed to be used as a specific feature of these soils.     

Diagnostics of hydromorphism in soils of autonomous positions on the Severo-Sos’vinsk Upland (Western Siberia)

The complex studies of hydromorphism features in taiga weakly differentiated soils using morphological (color), chemical (iron content in different extracts, indicators of reducing conditions (IRIS)), and geobotanic (using the Ramenskii scale) methods have led to ambiguous conclusions. In all the soils, surface gleying was manifested. According to the results obtained by different methods, the maximum reduction processes were related to either the sublitter or the next deeper horizon. The Schwertmann coefficient, the criterion of Bodegom, and the Ramenskii scale indicated an increase of hydromorphism in the soils studied in the following sequence: the lower part of the ridge slopes drained by the small gullies < the middle part of the slopes < the flat tops of the ridges < the depression between the ridges. The morphological diagnostics of gleying proved to be a less sensitive method, which can recognize only the most contrasting hydromorphic soils. The lower horizons in some taiga soils have a bluish gray color probably not related to the recent soil hydromorphism.     

Genesis of soils developed from red-brown clays and loesslike loams in the southwest of the Central Russian plain (the Belogor’e reserve)

Soils developed from the red-brown Neogene clay and the Quaternary loesslike loams have been studied in the south of the forest-steppe zone on the Central Russian Upland. A polygenetic nature of the soil profile on the loesslike loams is shown. The modern pedogenetic processes in this soil ensure its eluvial-illuvial differentiation with the development of multilayered coatings in the illuvial horizon. The soil developed from the Neogene clay has a lower degree of differentiation despite the more acid reaction. The micromorphological study of the coatings and the mineralogical analysis of the clay fraction separated from the coatings and from the intraped mass disclose differences in the geneses of B horizons of the two soils. In the soil developed from the loesslike loam, hydromica predominates among clay minerals of the coatings; in the soil developed from the red-brown clay, smectitic minerals predominate in the clay fraction. Differences in the properties of these two parent materials predetermined differences in the major directions of soil formation: the metamorphic pedogenesis predominates on the red-brown clay, whereas the textural differentiation develops in the soil on the loesslike loam. The middle horizons in the studied soil profiles are referred to as the structural-metamorphic and textural (clay-illuvial) horizons, respectively.     

Fungal communities in the soils of early medieval settlements in the taiga zone

The difference between the mycobiota in anthropogenically transformed soils of the settlements of the 9th–14th centuries and in the background zonal Podzols and umbric Albeluvisols of the middle and southern taiga subzones in the European part of Russia is demonstrated. The mycological specificity of anthropogenically transformed soils with a cultural layer (CL) in comparison with the background soils is similar for all the studied objects. Its characteristic features are as follows: (1) the redistribution of the fungal biomass in the profile of anthropogenically transformed soils in comparison with zonal soils, (2) the lower amount of fungal mycelium in the CL with the accumulation of fungal spores in this layer, (3) the increased species diversity of fungal communities in the CL manifested by the greater morphological diversity of the spore pool and by the greater diversity of the fungi grown on nutrient media, (4) the change in the composition and species structure of fungal communities in the CL, (5) the replacement of dominant species typical of the zonal soils by eurytopic species, and (6) the significant difference between the fungal communities in the CL and in the above-and lower-lying horizons and buried soils of the same age. Most of the mycological properties of the soils of ancient settlements are also typical of modern urban soils. Thus, the mycological properties of soils can be considered informative carriers of soil memory about ancient anthropogenic impacts.