Russian Soil Classification Research Articles

Podzolic-brown soils of the Far East on the Soil map of Russian Federation, scale 1 : 2.5 M, and their correlation with soils in the Russian soil classification

Podzolic-brown forest soils on the Soil Map of Russian Federation, scale 1 : 2.5 M, are widespread on the plains and plateaus of the Far East, referred to the Eastern brown-forest-soil area in the scheme of soil-geographical zoning. There, in Primorye and Priamurye regions, they are confined to various parent rocks and to different climatic and biota conditions. In the Classification of Soils of Russia (2004, 2008), there are no direct analogues of podzolic-brown soils in the map legend. To name these soils in the Russian classification system, regional publications (N.A. Kreida, G.I. Ivanov, V.I. Roslikova et al., N.M. Kostenkov, E.A. Zharikova) were reviewed: morphological and physicochemical properties of podzolic-brown soils were assessed in terms of their compliance with the diagnostic criteria of their possible analogues in the Russian system. The comparison has shown that in Primorye, on stony-loamy-clayey derivates of hard rocks, podzolic-brown soils correspond to soddy-pale-eluvial-metamorphic soils with textural differentiation, on loamy-clayey lacustrine-alluvial and colluvial deposits – as dark-humus podbels. In the north, in Priamurye region, podzolic-brown gley soils have properties of both texture-differentiated soils with the BT diagnostic horizon and of soils with a specific cryogenic structure in the middle cryometamorphic horizon. In the ideology and nomenclature of the Russian classification system, the former are defined as mucky-podzolic gleyic soils, the latter soils, as depending on the intensity of surface gley and structure development, can be defined as cryometamorphic podzolized gleyzems, eluvial-metamorphic cryometamorphic gleyic soils, or gleyic svetlozems.

Sphagnum Litter as the Most Important Genetic Horizon in the Profile of Peat Soils of Boreal Bogs

Peat soils of the taiga zone of West Siberia have historically been relatively poorly studied. In the diagnostics of peat soils, the question of the belonging of the sphagnum litter horizon to the soil profile, as well as the identification of its lower boundary, remains unresolved. In the WRB and Russian Soil Classification, sphagnum litter is considered as a vegetation cover, while in the Soviet classification it is considered as an integral part of the soil profile. The last point of view is also shared by the majority of Russian researchers. Using the material obtained in the study of peat soils in the basin of the river Kazym (subzone of the northern taiga, West Siberia), a comparative characteristic of the sphagnum litter horizon (0–20 cm) and the underlying peat horizon (20–50 cm) was carried out using three parameters: the botanical composition of peat, the degree of peat decomposition, and the color of the soil. All soils are differentiated into the litter horizon and the peat horizon by at least one parameter (5% of the profiles), but in 71% of cases, by three at once. The degree of profile differentiation into two horizons tends to increase in a series of soils formed, respectively, in oligotrophic pine-shrub-sphagnum, oligotrophic complex ridge-hollow, and mesotrophic biogeocenoses. In the overwhelming majority of oligotrophic peat soils, the transition from the litter horizon to the peat horizon is gradual, which does not allow a reproducible assessment of the boundary position in the soil profile. It is proposed to establish a fixed border of the litter horizon at 20 cm from the surface of the bog, referring it to the surface horizon of peat soil.

Agrogenic Soils on the Updated Version of the Soil Map of Russia, 1 : 2.5 M Scale: Classification Diversity and Place in the Soil Cover

Usually, soils changed by farming (agrogenic soils) are not shown on small-scale maps, including the Soil Map of the Russian Federation, 1 : 2.5 M scale (1988). One of the issues of the map updating performed by the Dokuchaev Soil Science Institute is the inclusion of agrogenic soils into the map contents and representation of some of the former native soils as agrogenic soils on the updated map. Preliminarily, all native soils shown on the map have been reclassified into the new Russian soil classification system. Agrogenic soils in this system are separated as agrosoils in different orders and as a specific order of agrozems. Agrogenic soils have been identified in the soil polygons in agreement with the map showing the percentage of arable land in Russia linked to the polygons of the soil map. We have identified the classification position of the initial native soils involved in arable farming. Overall, 114 legend units representing agrosoils and agrozems have been identified. This number is dictated by the diversity of native soils subjected to the agrogenic impact and their agrogenic modifications. Agrogenic soils on the updated map are shown in 4813 polygons out of the total of 25711 map polygons. Chernozems are characterized by the greatest diversity of agrosoils and the largest number of polygons containing various agrochernozems. The order of texture-differentiated soils is also rich in agrogenic soils, both agrosoils and agrozems. Arable soils initially belonging to the order of Al–Fe-humus soils are present in a relatively small number of polygons and are only represented by Al–Fe-humus agrozems. The number of polygons with participation of agrogenic soils and their proportion in the soil cover illustrate geographical patterns of their distribution, in particular, homogenous or mosaic distribution patterns in the areas of different soil orders.

Humus profile specificity of chernozems of the Ob river left bank within the Priob Plateau

Purpose of the study: to identify the features of chernozem humus profiles of the river Ob left bank within the Priob plateau (south of West Siberia) and the reasons that determined their diversity. Place and time. The south of West Siberia (Topchikhinsky district of the Altai Territory), the north-eastern part of the Priobsky plateau, the steppe zone of the Pre-Altai province of the Kulundinsky-Aleysky district, the key site "Volodarka" on the eastern edge of the Porozikhinsky-Aleysky ridge (52°41-42' N and 83°38'E). Sampling was carried out annually in August. Methodology. The collection and interpretation of materials are based on the principles and rules of the systems approach and soil ecology. The objects of study were southern and ordinary chernozems confined to different parts of the Volodarka key site (according to the soil classification of 1977; these classification names of soils are used in the text; according to the new Classification of Russian Soils (2004), the soils belong to the subtype of migratory-mycelial and textural-carbonate; according to WRB-2015 they are in the reference soil group Chernozems with the qualifiers calcic and siltic). The characteristics of humus profiles were obtained using traditional methods. All methods of analytical and instrumental study of humus and its individual components were identical. Methodological features of the research include detailed sampling (every 5–10 cm or less within the visual boundaries of the horizons) in late summer and the absence of strict methods for purifying preparations from mineral impurities. In this work, the concepts of “humus” and “system of humus substances” in soils are used as synonyms. Main results. The humus profiles of the chernozems of the studied territory, currently functioning under the same conditions, have a significant variation in characteristics, representing a range of options typical for such soils (when, based on the combination of characteristics of elementary humus-forming processes - EHP - the upper part with the humification-transformation type of their structure and the lower one - with a transformation-migration type of combination of EHP), to varying degrees of structural complexity (when several parts are distinguished with different quantitative ratios of humus substances parameters with the predominance of their self-healing processes against the background of other EHP). The main characteristics of the studied buried paleosols lie within the limits peculiar to soils formed in temperature conditions optimal for humus formation, but different moisture conditions. Conclusion. A significant difference in the qualitative and quantitative characteristics of chernozem humus profiles of the Ob river left bank within the Priob Plateau is due to both the complex history of the territory development, and different levels of self-healing capabilities of the natural open self-regulating humus substance system, depending on environmental conditions during the period of its formation. During complex history of the territory development different horizons of Middle Pleistocene soils came to the surface in different places, and therefore are found within the thickness usual for mature full-profile modern soils. The advantage of using humus profiles when analyzing the state of soils and the natural environment that forms them is the possibility of conducting a more detailed analysis of the variability of properties, the use of sediments and soils of different preservation, and identifying variations in environmental parameters even in the case of very short episodes of change in one or more soil formation factors or their individual characteristics, which are shorter in duration than the characteristic time required for the formation of the trait morphological expression. The materials presented in the work and their interpretation show that the information obtained about the soil state and the environment based on the study of soil humus profiles (the characteristics of which can be the results of studying the composition and properties of humus) has not lost its significance and can be used in solving a wide range of soil science problems including monitoring soil conditions, as well as substantiating forecasts of their behavior when changing environmental operating conditions.

Lateral and radial differentiation of cryogenic soils geochemical composition in the Khanovei scientific and educational field site, Bolshezemel'skaya tundra

The subject of the study was the soil and geochemical features of southern tundra cryogenic landscapes on the Khanovei educational and scientific field site located nearby the eponymous settlement in the Vorkuta district, Komi Republic. Morphology of soil profiles were described according to the modern Russian soil classification system. Chemical analytical sample treatment was done to evaluate such physical and chemical parameters of soil horizons as the pH rate, water-soluble salts content, organic carbon content, soil texture, iron fractional composition. The main point among soil and geochemical features of the Khanovei field site was gross chemical composition of cryogenic soils. Gross concentrations of chemicals were measured with the X-ray fluorescence method by portable X-ray Fluorescence Analyzer and then geochemical ratios of radial (profile) and lateral (catenar) differentiation of chemical elements – R and L. Largest R ratio meanings in soil profiles were in gleyic horizons including above-permafrost. Peat horizons without traces of soil mineral fraction were depleted with the most of elements (R = 0,1–0,3) and mineral horizons of soils were differed by increased RFe, RMn etc. The lower part of the catena with soils of mostly sandy texture was depleted by the main part of elements (Ti, Zn, Zr etc.) and predominantly loamy-textured soils in the upper part accumulate these elements and form increased L ratio meanings.

Floodplain soils on the soil map of the Russian Federation, scale 1 : 2.5 M, 1988, in the Russian soil classification, 2004

The largest area of taiga gley-differentiated soils on the Soil map of Russian Federation, scale 1:2.5 M, is located in the north of West Siberia. Small areas are dispersed over the northwestern European Russia, Eastern Siberia and the North-East. Interpretation of taiga gley-differentiated soils in terms of Russian soil classification system (2004) is rather ambiguous owing to high diversity of ecological conditions where these soils occur, аs well as variability of soil morphological, chemical, and physicochemical properties in diverse mapping units. Comparing properties of taiga gley-differentiated soils described in the Program of the map (1972) and in regional publications with the diagnostic criteria for soil types in some orders of the Russian classification system made it possible to find adequate names and taxonomic position for these soils. Thus, taiga gley-differentiated soils in the middle and northern taiga of Western Siberia proved to be allocated to several orders: weakly differentiated and gleyed soils with a brown profile were referred to the order of organo-accumulative soils as shallow-peat gleyic soils; their more hydromorphic variants – taiga gley-differentiated shallow-peat soils were defined in the order of gleyzems, as peat gleyzems, soil with morphologically differentiated profile having a particular cryogenic structure were qualified for svetlozems and iron-illuvial gleyic svetlozems in the order of cryometamorpic soils, and for eluvial-metamorphic soils of the same order in case of cryogenic structure was absent. Taiga gley-differentiated soils in their northwestern area are confined to varved clays and correspond to (soddy-)eluvial-metamorphic gleyic soils.

Cryoaridic Soils as a Genetic Type in the Russian Soil Classification System: Geography, Morphology, Diagnostics

Cryoaridic Soils as a Genetic Type in the Russian Soil Classification System: Geography, Morphology, Diagnostics

ОСОБЕННОСТИ СОВРЕМЕННОГО СОСТОЯНИЯ ПОЧВЕННЫХ РЕСУРСОВ ЕВРЕЙСКОЙ АВТОНОМНОЙ ОБЛАСТИ И ИХ ЗНАЧЕНИЕ В АГРОЭКОЛОГИЧЕСКОМ РАЗВИТИИ РЕГИОНА

The paper deals with the description of soil resources of mountainous and low-lying (agricultural) areas in the Jewish Autonomous Region. The soil diversity is characterized according to the substantive-genetic (profile-genetic) principles of the new Russian soil classification system. The author considers actual problems of agrarian utilization of soils in the Jewish Autonomous Region in the new social-economic conditions.

Soil organic carbon stocks and stability of organic matter in permafrost-affected soils of Yamal region, Russian Arctic

Chemical composition of soil organic matter determines its decomposability and may affect soil microbial activity. This is very important for understanding variability in soil organic carbon pools in context of changes in plant cover or climate. This paper is aimed to characterize existing carbon pools and molecular organization of the humic acids, isolated from various permafrost-affected soils of Yamal region and to assess the potential vulnerability of soils organic matter in context of possible mineralization processes. Soils for most of studied sites were characterized predominantly by acidic to strong acidic pH. Profile distribution of carbon, nitrogen and C:N ratio showed non-gradual changing with the depth due to manifestation of cryopedogenesis in soil profiles which lead to cryogenic mass transfer. Mean soil organic carbon stocks for the study area were 7.9 ± 2.2 kg m−2 (for 0–10 cm layer), 15.0 ± 5.5 kg m−2 (for 0–30 cm), 24.0 ± 8.0 kg m−2 (for 0–100 cm). Analysis of soil organic carbon stocks among predominant soil types (Russian soil classification system) revealed relatively high variability of values in 0–10 cm (from 4.5 kg m−2 in Peaty Gleyzem underlain by permafrost to 9.6 kg m−2 in Peaty Podzol underlain by permafrost) and 0–30 cm layers (from 9.9 kg m-2 in Cryic Podbur underlain by permafrost to 24.1 kg m−2 in eutrophic peat soil underlain by permafrost). Results of solid-state 13C NMR spectrometry showed low amounts of aromatic fragments in studied soils. All studied soils are characterized by predominance of aliphatic structures, and also carbohydrates, polysaccharides, ethers and amino acids. High content of aliphatic fragments in studied humic acids shows their similarity fulvic acids. Low level of aromaticity reflects the accumulation in soil of poorly decomposed organic matter due to cold temperatures. Our results provide further evidence of high vulnerability and sensitivity of permafrost-affected soils organic matter to Arctic warming. Consequently, these soils may play a crucial role in global carbon balance under effects of climate warming.

Floodplain soils on the soil map of the Russian Federation, scale 1 : 2.5 M, 1988, in the Russian soil classification

The development of the digital model of the soil map of Russia derived of the map of the Soviet Russian Federation, 1988, compiled in Dokuchaev Soil Science Institute, comprises the transfer of soil names in the initial legend to those in the new classification system of Russian soils (2004). Floodplain soils (only native) are represented by seven legend units (out of 205) that were named in terms of soil classification of USSR, 1977, and part of their names indicated ‘landscapes’ rather than soils, which disagrees with the principles of the new classification system. Basing on numerous publications and following the rules of the new system, soils were renamed. Most of them were referred to alluvial soil types within the synlithogenic trunk (Fluvisols), and their new names indicate both their properties and their zonal attachment. In order to obtain more adequate patterns of soils in river valleys additional soils were introduced including stratified-alluvial soils in the trunk of primary pedogenesis (Regosols). Simultaneously, the composition of polygons in the database was revised in accordance with regional data; human-modified soils were introduced (agro-soils and urbo-soils).

Diagnostics of soils located in the gradient of urban-technogenic impact

The rapidly progressing urbanization results in decline of environmentally valuable forest territory. Intact ecosystems bordering urban communities suffer from heavy technogenic pressure and degrade irreversibly over time. This situation necessitates studies that analyze the ecological condition of major components of forest ecosystems exposed to various levels of such pressure. The survey was carried out in the city of Petrozavodsk in sites with degraded, slightly disturbed, and undisturbed forest ecosystems. For each site, the soil condition was assessed, the tree stand and the living ground cover were described. As a result, it was found that soils in the slightly disturbed forest ecosystem generally corresponded to the natural background (Ferric Illuvial Podzol). Changes in their morphological and chemical properties compared to soils in the undisturbed reference plot were identified. The thickness and ash content of the upper organic horizon in the slightly disturbed site changed. The forest ecosystem was in the transitional stage (from I–II to III) of recreational digression and required infrastructural improvements. The forest ecosystem in the built-up site was totally destroyed. Irreversible transformation of its natural environment resulted in the loss of woody and ground vegetation. The native zonal soils were ruined, and their diagnostic horizons cannot be identified. There was observed a large amount of rocks and anthropogenic inclusions throughout the profile. According to the Russian soil classification, these formations belong to the subgroup of organo-mineral strata of technogenic surface formations. The collected data can be used as the basis for ecological monitoring of urban soils. Based on the findings, recommendations were given on how to conserve and improve the sanitary and esthetic functions of forest areas adjoining urban built-up land.

Typical features of short-profile soils in the Middle Urals

Data on short-profile mountainous soils of the Middle Urals are discussed. In the new Russian soil classification system, these soils belong to the orders of lithozems (Leptosols), petrozems (Lithic Leptosols), organo-accumulative (Skeletic Umbrisols), Al–Fe-humus (Entic Podzols, Albic Podzols), and gley (Gleysols) soils. Information-logical analysis of factual data attests to a close relationship between the thickness of soil profiles and the genetic types of soils. Thus, the degree of development of the profile can be a diagnostic indicator of the type of soil formation. Short-profile soils develop in all high-altitude landscapes. Lithozems are widespread in all vertical zones. Other short-profile soils are more definitely related to certain altitudes. Thus, organo-accumulative soils mainly develop in the subalpine zone at 650–750 m a.s.l. under tall-herb meadows, podburs are found in the mountainous tundra zone at 800–940 m a.s.l. on slightly sloping surfaces. Podzols tend to occur under elfin forest zone (740–850 m) and in the transitional zone between elfin forest and tundra on steep slopes. Gley soils are formed under woodlands on flat or slightly sloping terraces at the ecotone between the zones of mountainous taiga and park woodland.

Morphological Features of Soils in the Yelshanka River Floodplain Under Conditions of Urbotechnopedogenesis

The river system on the territory of Volgograd is represented by eight small rivers. Currently, in the territory of Volgograd there is an active inclusion of valley and floodplain landscapes in the urban area. Under conditions of the anthropogenic impact, the normal regime of valley and floodplain landscapes is disturbed. As a result of changes in the hydrological regime of floodplains and valleys, various morphological transformations of soil cover occur, such as the formation of specific iron and carbonate new formations, etc. As a result of economic activities, modern alluvial soils and sediments are often buried under the thickness of the anthropogenic material. The relevance of the study is due to the high recreational value of valley and floodplain landscapes. The authors analyze 6 soil profiles set up in different parts of the Yelshanka river floodplain. The description of soil sections was performed with the use of the Field Qualifier of Soils of Russia. Soil profiles were named in accordance with the Russian Soil Classification and Diagnosis (2004) and the Field Qualifier of Soils of Russia (2008). In Volgograd, as in most cities in Russia and abroad, the study of soils of floodplain landscapes is not systematic, and in some cases is limited to a certain area of research. The purpose of the work was to monitor the morphological state of the floodplain soil cover of the Yelshanka River in order to determine the degree of soils transformation in the area as a result of urbotechnopedogenesis. The studies conducted at the site allow considering that the urban soils of recreational areas are a consequence of the combined effect of zonal natural and climatic and urbanogenic factors of soil formation. Studies of soils of floodplain landscapes in the urban environment make it possible to monitor the state of natural landscapes and their transformation in conditions of urbotechnopedogenesis, as well as the development of the ecological framework of the city.

Cryogenic soils in the Vilyuy River Valley (Yakutia)

The object of this research is the cryogenic soils of the territory located in Central Yakutia, in the middle reach of Vilyuy River nearby Makhatta Tukulan with middle-taiga larch woods landscapes. In July 2021, on the right and left banks of the Vilyuy River, twelve soil sections have been formed, which relate to turf-podzols and turf-sub-units of the illovial-ferruginous, sod and alluvial sod, psammozems and stratozems according to to classification and diagnostics of Russian soils (2004). On the slope of the river valley was also formed the soil catena that included elementary geochemical landscapes of river terraces tops and slopes surfaces, as well as middle and high floodplains on the slopes of thermofusional funnels. Soil sections were also formed in flooded beam bottom and well-drained ravine bottom, on sub-horizontal Makhatta Tukulan surface, bottoms and  slopes of thermo-suffosional funnels. The study involves 46 soil samples for measuring the acidity level (pH), electric conductivity (EC), and concentration of total disolved solids (TDS). The explored soils are characterized with pH ranging from 2.81 to 7.78, with most common fluctuations of 5.5–5.6. TDS rates were often within the limit of 10 mg L-1 and rarely exceeded that threshold, however, there were single valyes higher than 50 mg L-1. Thus, the highest EC values (over 100 μS/cm) were measured in surface and subsurface horizons with high organic matter content, whereas mostly mineral horizons had typical EС values within the limit of 20 μS/cm.

Mire peat soils of the taiga and sub-taiga zones of West Siberia on a digital model of the soil map of Russia at a scale of 1 : 2 500 000 in terms of the Russian soil classification

A digital version of the soil map of the Russian Federation, scale 1 : 2.5 M, is being prepared based on the analysis of the attributes of polygons with peat soils in the West-Siberian taiga and sub-taiga zones. The correction was perfomed in 795 polygons (with the total area of 179 483 km2) out of 1 711 polygons considered (with the total area of 262 204 km2). The currently formulated idea of the dominance of oligotrophic bogs in the West Siberian taiga region of mires served as the basis for suggestion to replace the mesotrophic peat soils by oligotrophic ones in 598 polygons of the total area of 87 250 km2. Similarly, the polygons of microcatenas comprising oligotrophic and mesotrophic peat soils (57 polygons, total area of 38 405 km2) were modified: only oligotrophic peat soils were considered to be the dominant ones there. At the same time, a number of polygons with prevailing oligotrophic soils, confined mainly to the sub-taiga zone were proposed to be replaced by polygons with mesotrophic peat soils. The thermokarst pools in ridge-hollow mire complexes that were shown on the soil map of Russia beyond the permafrost zone were eliminated from the map database; the mapping of destructive peat soils was rearranged in accordance with the new interpretation of this taxon in the Russian soil classification. This work should improve the quality of research in the field of assessing the resource potential of peat soils in West Siberia.

SOILS OF CHERNEVAYA TAIGA OF WESTERN SIBERIA — MORPHOLOGY, AGROCHEMICAL FEATURES, MICROBIOME

The soils of Chernevaya taiga are unique in terms of high fertility that was formed not as a result of agricultural practices, but due to the combination of a huge volume of biotic and abiotic resources. This area was able to preserve its “pre-agricultural” level of fertility overtime by avoiding the negative consequences of long-standing agricultural usage. Comprehensive analysis of all related properties within the framework of a metagenomic study and identification of microbial drivers of fertility can become the basis for innovative technologies aimed to increase the productivity of soils and crops. In this work, for the first time were obtained data on the taxonomic structure and features of the of the microbiota of soils in the Chernevaya taiga and identified taxa, the number of which significantly increases with the transition from the background zonal soil to the soil of Chernevaya taiga. Analysis of soil samples collected during expeditionary surveys in 2019 showed that the soils in the Western Siberia (Novosibirsk, Tomsk, Kemerovo, and Altai regions) portion of the Chernevaya taiga are texture-differentiated dark gray soils (clay loam and silt clay varieties confined to the deluvial cover of the Holocene and Late Pleistocene) that were formed as a result of a unique combination of geogenic and bioclimatic conditions. These soils are not affected by the permafrost in winter timers and are supplied with enough moisture to precipitate rapid mineralization of litter material and the fixation of mineral nutrients in the upper humus layer of the soil profile. The accumulation of nutrients is an essential property of the soils of the Chernevaya taiga associated with the phenomenon of gigantism and extremely high levels of plant productivity. The soils of Chernevaya taiga contain the maximum amount of carbon in organic compounds compared with soils of oligotrophic habitats (9.85% versus 2.74%). The levels of actual soil fertility in the soils of the Chernevaya taiga are several times higher than in the soils of adjacent biotopes (the maximum content of the exchange forms of phosphorus and potassium is 702 and 470 mg/kg), which, when compared to oligotrophic forests, are poor in terms of agrochemical fertility (the maximum content of the exchange forms of phosphorus and potassium is 113 and 18 mg/kg), do not have a pronounced humus profile and are either gray-humus (Umbrisol) or Podzol types according to substantive-profile classification of Russian soils. The diversity of microorganisms in the studied soils varies depending on the trophic regime of the ecosystem. The soils of the Chernevaya taiga are characterized by an increased diversity of the microbial community (estimated by the Shannon index), as well as by presence of phyla Nitrospirae and Thaumarchaeota, that, however, are not dominant. Phyla Proteobacteria, Verrucomicrobia, Actinobacteria, Acidobacteria, Planctomycetes, Firmicutes appeared to be common for all studied soils.

Paleocryogenesis as a Factor of Heterogeneity of Agro-Gray Soil

Delineation of the features of paleocryogenic microtopography by zero-curvature morphoisographs on a test plot in the south of Moscow oblast enabled us to reveal the polygonal-blocky microrelief (microelevations, microdepressions, slopes, and runoff strips), forming eluvial, trans-eluvial, and trans-accumulative agrolandscapes. The soil cover pattern of eluvial agrolandscape includes elementary soil areas of noneroded, slightly eroded, moderately eroded, and aggraded soils. The agrolandscape is dominated by noneroded soils. The soil cover pattern of trans-eluvial agrolandscapes with microdepressions includes elementary soil areas of slightly, moderately, and strongly eroded soils, as well as eroded–aggraded and aggraded soils, with the dominations of slightly eroded soils. The soil cover pattern of trans-accumulative agrolandscapes also includes elementary soil areas of slightly, moderately, and strongly eroded soils; eroded–aggraded soils; and aggraded soils with the domination of strongly eroded soils. The paleocryogenic microrelief became the initial factor of the formation of elementary soil areas with different erosion rates during the long-term (200 years) agricultural use of these lands. Elementary soil areas with different erosion rates of the upper horizons are characterized by outcropping of underlying horizons of different textures. We have identified silt loam, light clay, and clay loam exposed to the surface by erosion on the studied plot. As a result, a complex soil cover pattern with differentiation of soils at the level of varieties (in Russian soil classification system, a taxonomic category based on the topsoil texture) was formed.

Soils and the Soil Cover of Mountainous Tundra Landscapes on Calcareous Rocks in the Polar Urals: Diversity, Taxonomy, and Nitrogen and Carbon Patterns

Landscapes of the northern part of the Bolshoi Paipudynskii Ridge (the Polar Urals) served as a key site to study the taxonomic diversity of soils on calcareous rocks as related to both bioclimatic and geogenic (relief, thickness of eluvial and colluvial derivatives of calcareous rocks) factors. Soils of the postlithogenic trunk of the new Russian soil classification system are developed under different plant communities. They are classified within several soil orders: cryometamorphic soils (Mollic Calcaric Stagnosols), lithozems (Folic Mollic Calcaric Leptosols), organo-accumulative soils (Molic Leptic Calcaric Stagnosols), and gley soils (Folic Calcaric Gleysols). These soils compose either small individual areas, or occur in soil associations. The mass of carbon and nitrogen in the aboveground phytomass ranges within 40–49 and 0.9–2.3%, respectively. The storage of aboveground phytomass (fresh weight) varies from 20 to 1600 g/m2. In each soil profile, the surface horizons have a maximum content of organic carbon and nitrogen (up to 40 and 2.5%, respectively). The Corg and Norg patterns in soils depend on the productivity of plant communities, the composition of falloff, and the conditions for its decomposition. In all soil profiles, the inorganic carbon content (Cinorg) increases down the soil profile reaching 12%. The mineral nitrogen content does not exceed 1%. The contents of N- $${\text{NH}}_{4}^{ + }$$ and N- $${\text{NO}}_{3}^{ - }$$ have their maximums reaching 140 and 30 mg/kg, respectively, in the surface soil horizons.

“Black soils” in the Russian Soil Classification system, the US Soil Taxonomy and the WRB: Quantitative correlation and implications for pedodiversity assessment

“Black soils” recently proposed by the FAO Global Soil Partnership, include fertile soils, characterized by a thick, dark-colored soil horizon rich in organic matter. This study addressed the proposed concept of “black soils”, in terms of taxonomic relationship of their corresponding soil types of existing soil classifications. Similarity studies were based on the calculation of taxonomic distances between selected soil groups with organic matter–enriched horizons of the Russian Soil Classification System, the United States Soil Taxonomy and the World Reference Base for Soil Resources. In the process, we used the so called ”centroids”, which are the calculated mean values of several soil properties for each of the soil groups using legacy data derived from national and international databases. The results indicated that the Great Groups of the Mollisol Order in the US Soil Taxonomy had small taxonomic distances within the order, except some soils with shallow depth to the hardpan or permafrost. Dark-colored Vertisols and Andisols were found to differ from the Mollisols and similar soils found in similar environments mainly under grasslands. We recommend excluding Vertisols and Andisols from the “black soils” cluster due to the peculiarity in their properties, potential use and management. While the Vertisols and Mollisols of the Soil Taxonomy were completely dissimilar in properties, the WRB Vertisol Reference group and Russian dark-humus compact soils fitted well the Mollisols cluster, presumably due to the different concept of the Vertisols in the studied system. The soil types of the “black soils” of the Russian soil classification had a short distance to the corresponding Reference Groups of the World Reference Base. Also, the similarity was high with the Great Groups of the US Soil Taxonomy for all soil types except of Kastanozems, but the relationship in places was not well interpreted from a pedogeographic point of view. We ascribed the phenomenon to the geographical bias of the databases. Though “black soils” form a distinct cluster that roughly corresponds to the Mollisols Order of the US Soil Taxonomy, the taxonomic distance within the group may be significant, contributing to the pedodiversity of soilscapes of “black soils”.

Soil Cover Diversity and Its Spatial Organization at Different Map Scales

We summarized the results of studies of pedodiversity and contrast and variability of soil properties based on the analyses of soil maps of different scales for the republics of Karelia and Dagestan and the Moscow region. We used fragments of the Soil Map of the Russian Federation on a scale of 1 : 2 500 000 as a small-scale map and three different medium-scale maps (from 1 : 300 000 to 1 : 500 000). Large-scale maps (1 : 10 000) were compiled for representative plots within the studied territories specifically for the study of pedodiversity. All the maps were digitized, map legends were converted to the new Russian soil classification system and to the World Reference Base for Soil Resources (WRB), and Shannon–Wiener diversity indices were calculated. Comparison of indicators revealed the dependence of the values of the diversity indices on the map scale. The indicators for the large-scale map were relatively low and did not differ much when using Russian and international classification. We concluded that for the successful assessment of soil diversity at different scales, it is important to use several large-scale maps that reflect the heterogeneity of regional soilscapes. Natural boundaries between soilscapes and soil regions can be found using the pedodiversity index map. In almost all cases, maps with a WRB-based legend had lower indicators of pedodiversity than maps with a legend based on the Russian soil classification. This confirms the fact that the international classification is less detailed than the Russian national classification, which was originally intended for large-scale mapping of soils.