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.

The soil cover of cities and towns within their administrative boundaries is composed of soils, more or less modified by the urban environment along with native, agricultural soils and non-soils. For preserving this diversity when introducing these new objects to the unified digital model of the soil cover of Russia, soil maps of 10 “test” cities have been compiled. The cities are located in several natural zones, and are intermediate in terms of their population. Mapping was performed by means of detailed purposeful deciphering, data on mapping units on the original soil map, and recent systematics of urban soils and their dependence on the urban environment. The approaches applied were supported by the experience in soil mapping of St-Petersburg, Moscow, Volgograd and few other cities. Soils were qualified in the system of Russian soil classification, and their areas, along with those of non-soils, were regarded as units in the theory of soil cover patterns. In all cities investigated, soil associations comprised urban soils per se, transitional soils including agro-soils and conventionally native ones; their ratios in the soil cover depend on both historical-socio-economical reasons and the natural enviroment.

Usually, soils changed by farming (agrogenic soils) are not shown on small-scale maps, the Soil Map of the Russian Federation, 1 : 2.5 M scale (1988), in particular. One of the issues of the map updating performed in the Dokuchaev Soil Science Institute is the introduction 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 agro-soils in different orders and form 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 as determined by I.Yu. Savin with coauthors (2020) and 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 agro-soils and agrozems have been identified. This number is dictated by the diversity of native soils subjected to the agricultural impact producing their agrogenic modifications. Agrogenic soils on the updated map are shown in 4813 polygons out of the total of 25 711 polygons. Chernozems are characterized by the greatest diversity of agro-soils and the largest number of polygons containing diverse agro-chernozems. The order of texture-differentiated soils is also rich in agrogenic soils, both agro-soils 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 represented only by Al–Fe-humus agrozems. The number of polygons with participation of agrogenic soils and their proportion in the soil cover illustrates the geographical pattern of their distribution, in particular, homogenous or mosaic patterns in the areas of different soil orders.

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.

The dark-humus soil type was included in the updated legend of the Soil Map of the Russian Federation at scale 1 : 2.5 M, converted to the system of Soil Classification of Russia. The soil profile starts with the dark-humus horizon gradually merging to the parent rock; any mid-profile diagnostic horizons are absent. Large areas of dark-humus soils are found in the forest-steppe, steppe and taiga zones of the European Russia, Western and Central Siberia, in the Trans-Baikal region, the Altai-Sayany Mountains, and the Caucasus. The type of dark-humus soils comprises both mesomorphic soils (of normal moisture conditions) and soils with additional surface or ground-water moisture. The main prerequisites for the formation of dark-humus soils are, on the one hand, the climatic conditions favorable for the dark-humus horizon formation, and, on the other hand, parent material - mostly derivates of hard rocks, restricting the development of mid-profile diagnostic horizons. In the updated map, the following initial legend units are partially or completely converted to dark-humus soils: several units of chernozems, dark-gray forest and gray forest non-podzolized soils, soddy-taiga base-saturated and slightly unsaturated soils, several mountain soils, a significant part of soddy-calcareous soils, as well as some mountainous forest-meadow soils. The diversity of dark-humus soils subtypes is determined by secondary carbonate features, weak signs of clay accumulation and podzolization, alteration of the mineral mass, gley and cryogenic phenomena.

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).

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).

Cambisols – soils in the WRB system with a broad range of properties and occurring in diverse environments – have been chosen as an example for interpretation of soil units on the updated version of the Soil Map of the Russian Federation (1988), which is essential for communicating soil knowledge. We have compared three soil maps with legends in the FAO or WRB system with the updated soil map of Russia to identify areas corresponding to Cambisols; we analyzed definitions and diagnostics of Cambisols in the FAO/WRB system in its historical development and compared them with diagnostics of soil units on the updated soil map of Russia. Soils of three metamorphic orders in the new Russian classification generally correspond to the definition of Cambisols with the best coincidence for burozems (Dystric or Eutric Cambisols) and less complete coincidence for rzhavozems and cryometamorphic soils; identification of Yakutian pale soils in the WRB system is rather ambiguous. The scale of the Russian map (1 : 2.5 M) and rather detailed soil names in the legend require more complete WRB soil names; for this purpose, several principal and supplementary qualifiers may be used, or even new ones may be borrowed from other reference groups.

The Soil Map of the Russian Federation, 1 : 2.5 M scale (1988) requires updating to include soil data that have been accumulated in the past decades, reflect real changes in the soil cover, including anthropogenic transformation, and ensure precise localization of soil objects and correspondence of the map to satellite data with the use of digital soil mapping technologies. The substantive-genetic classification system of Russian soils (2004, 2008) provides the conceptual basis for this updating. The conversion of soil information from the initial map of 1988 into the new classification system is being performed for each polygon of the digitized map. It is based on the analysis of a vast body of diverse information and includes both the search for analogues of the names of mapping units in the new classification system (renaming of the soils) and the correction of the composition of soils in the polygons: new natural soils, cultivated soils (agrosoils), and urban soils are added to the attribute database. The largest number of new natural soils has appeared in legend sections “Soils of tundra” and “Soils of taiga and broadleaved forests”. Anthropogenic soils (119 legend units) that are shown on the map for the first time, have their maximum representation (36 units) in the section “Soils of steppes”; it is close to the number of natural soils (37 units) in this zone. A considerable percent of anthropogenic soils (> 50% of the natural soils) is also typical of legend sections “Soils of broadleaved forests and forest-steppes,” “Soils of dry steppes and semideserts,” “Salt-affected and solonetzic soils”. The total number of natural and anthropogenic soil units (425) in the new legend is more than twice as large as the initial number of natural soil units in the base map (205). The results of the renaming and updating of soils for each soil polygon are fixed in a separate section of the attribute database to the map and will be used for generating the new map by the methods of digital soil mapping.

V.V. Dokuchaev Soil Science Institute has initiated a project on compilation of a new Digital Soil Map of Russia on the basis of the Soil Map of the Russian Federation (SMRF) 1 : 2.5 M scale (1988) revised and interpreted in ideology and nomenclature of the new substantive-genetic Classification System of Russian Soils (CSRS). The first stage implies the conversion of soil mapping units on the original map into the CSRS with a corresponding renaming of soils in the attribute database to the digitized version of the map for each soil polygon. During the second stage, a new digital model of the soil cover is developed with the use of digital soil mapping technologies, basic soil map, and new materials, including satellite images and digital elevation models. The legend section “Tundra Soils” contains 16 soil units forming their own areas or found in various combinations (soil complexes). As a result of the reclassification and careful analysis of each soil polygon, the soils of Arctic and Subarctic tundra have obtained a more detailed and differential representation on the new map, and their diagnostics based on the morphology of the profiles and major soil properties have been specified. The most significant changes in the initial content of the map concern the soils referred to as gley soils on the SMRF. A separate group of cryozemic soils has been specified. Weakly developed soils (petrozems, psammozems, and pelozems) and lithozems have been introduced on the map for the first time. Differential decisions are suggested for the soils of “spotty tundra” with sorted and nonsorted circles and for the soils of cryogenic fissures and cracks. The results of the study have made it possible to refine the diagnostics and nomenclature of soils in the CSRS.

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.

In the course of updating the soil map of the Russian Federation, 1 : 2.5 M scale (1988), Moscow oblast was chosen as a model object for testing the approaches to revise the map legend, which should be converted into the new Russian soil classification system, where much attention is paid to soils changed by human activities. This choice was made because of its rather simple natural soil cover (Albic Retisols predominate) along with high diversity and frequent occurrence of human-modified soils that should be shown on the map. Updating of the map database concerning natural Albic Retisols—soddy-podzolic soils was insignificant: few changes were introduced at the level of diagnostic properties, hence, subtypes. Arable soddy-podzolic soils were qualified for agro-soddy-podzolic soils if they occupy even surfaces, and they were named textural-differentiated agrozems if they are confined to slopes; the initial subtype diagnostics was mostly preserved. Soils of other land use categories—orchards, old estates, villages, dachas, urban-type settlements, were qualified for prograded or turbated agrozems, and intensely cultivated soils—for dark-humus stratozems; urban soils were referred to urbostratozems, ekranozems and diverse intergrades between these and natural soils. Deciphering of the space image of a model polygon located in a rather urbanized part of Moscow oblast permitted to identify soil associations for most common land-use types. However, introduction of all soils—ingredients of such associations—into the legend is limited by the small scale of the map, whereas introduction of the types of associations could contribute to a more adequate image of the soil cover in urbanized territories.

Updating of the Soil Map of the Russian Federation (1 : 2.5 M scale, 1988) is planned on the basis of the new classification system of Russian soils. At the first stage, soil information for each polygon on the map is transformed into this system with due account for new factual data. In this paper, we consider problems in reclassification of legend unit “soddy-calcareous soils, including leached and podzolized soils.” In dependence on the geographical position of particular polygons with these soils and the composition and properties of calcareous rocks, the soils of this legend unit are reclassified into different orders, types, and subtypes of the new classification system. The new soil names are introduced into the updated database to the vectorized version of the map. Thus, according to the thickness of the unconsolidated part of the profile, the former soddy-calcareous soils are specified into the orders of lithozems (<30 cm) and organo-accumulative soils (>30 cm). Within the latter order, the character of organic and humus horizons is taken into account in identification of the types of dark-humus, gray-humus, mucky–humus, raw-humus, and (probably) light-humus soil types with residual carbonates recorded at the subtype level. The types of raw-humus and light-humus carbolithozems are added to the classification system. An increased content of semidecomposed phytodetritus in the soils is reflected at the subtype level (the subtype of raw-humus soils). This level is also used to reflect the development of eluviation (eluviated soils), illuviation (clay-illuvial soils), and pedogenic transformation of middle-profile horizons (metamorphized, cryometamorphized, ferruginated, and gleyic subtypes) and the inheritance of some specific features of the parent material (red-profile soils). At the species level, the degree of leaching of carbonates from the upper part of the profile is indicated. Plowed soddy-calcareous soils are specified as agrohumus and agro-dark-humus soils. Geographical patterns of manifestation of these soil features and their “soil-ecological” logic are also discussed in the paper.

Specific soils of mountainous regions having no analogues on plains occupy less than 3% of Russia. On the soil maps of Russian Federation (1 : 2.5 M scale, 1988), they are represented by 10 mapping units, the names of which, along with the term “mountainous” reflecting characteristic properties of these soils (general youth, thin profiles, high content of gravels, underlying by hard bedrock) contain information about the particular landscape conditions of soil formation. For updating of the map, the soils shown on it are renamed in agreement with the new Russian substantive-genetic soil classification system. The profile-genetic approach lying in the basis of this system excludes the use of landscape terms in soil names. The reclassification of mapping units is performed with due account for individual features of each particular polygon shown on the map. In essence, it consists of the search of information about the soil properties for identification of the diagnostic horizons and genetic properties of the soils to give formulae of their horizonation (in symbols of diagnostic horizons and properties). This search is based on the program and explanatory text to the map and various regional publications presenting information about the soils and the agents of soil formation. The formulae of the profiles are used to determine classification position of the soils in the substantive-genetic classification system. Most of the soils from this section of the legend belong to the order of organo-accumulative soils. The differences between them are related to differences in the types of humus and surface organic horizons. In the case of the low thickness of the profiles, the soils belong to the orders of lithozems and/or poorly developed stony soils (petrozems). As a rule, the same unit in the legend to the map corresponds to two or more soils in the new classification system. The mapping unit “mountainous forest-meadow soils” has been subdivided into five different soils with due account for the regional specificity of soil properties and landscape features. In the course of this study, several suggestions to improve the classification system of Russian soils have been made.

Specific soils of mountainous regions having no analogues on plains occupy less than 3% of Russia. On the soil maps of Russian Federation (1 : 2.5 M scale, 1988), they are represented by 10 mapping units, the names of which, along with the term “mountainous” reflecting characteristic properties of these soils (general youth, thin profiles, high content of gravels, underlying by hard bedrock) contain information about the particular landscape conditions of soil formation. For updating of the map, the soils shown on it are renamed in agreement with the new Russian substantive-genetic soil classification system. The profile-genetic approach lying in the basis of this system excludes the use of landscape terms in soil names. The reclassification of mapping units is performed with due account for individual features of each particular polygon shown on the map. In essence, it consists of the search of information about the soil properties for identification of the diagnostic horizons and genetic properties of the soils to give formulae of their horizonation (in symbols of diagnostic horizons and properties). This search is based on the program and explanatory text to the map and various regional publications presenting information about the soils and the agents of soil formation. The formulae of the profiles are used to determine classification position of the soils in the substantive-genetic classification system. Most of the soils from this section of the legend belong to the order of organo-accumulative soils. The differences between them are related to differences in the types of humus and surface organic horizons. In the case of the low thickness of the profiles, the soils belong to the orders of lithozems and/or poorly developed stony soils (petrozems). As a rule, the same unit in the legend to the map corresponds to two or more soils in the new classification system. The mapping unit “mountainous forest-meadow soils” has been subdivided into five different soils with due account for the regional specificity of soil properties and landscape features. In the course of this study, several suggestions to improve the classification system of Russian soils have been made.

The analysis of the Soil Map of the Russian Federation (1 : 2.5 M scale, 1988) with identification of soils shown in each polygon in categories of the classification system of Russian soils (2004, 2008) is the first stage of work on creating the new digital soil map of Russia. It demonstrated the need to introduce a number of amendments to the classification system. They concern the definitions and names of diagnostic horizons and diagnostic features of soils. Thus, it is suggested that the mucky–dark humus horizon AH should be renamed as the mucky–humus horizon (as its properties do not fit the definition of the dark humus horizon in the system). Several new diagnostic features are introduced; for permafrost-affected soils, supra-permafrost accumulation of organic matter is designated by symbol cro. It is also suggested that the lists of soils at the subtype level, which reflects the development of certain diagnostic features, should be more flexible without their "rigid" linking to the given types. The aim of these changes is to reflect the accumulated information on the diversity of soils in Russia as displayed on the Soil Map of the Russian Federation (1988) and in the State Register of Soil Resources more adequately in the new classification system of Russian soils.

The position of palevye soils with differentiated profiles and with podzolized horizons developing from carbonate-free rocks under conditions of the cold extremely continental semihumid climate in the permafrost zone of Central Siberia in the New Russian Classification system is analyzed. The profile of these soils consists of the raw-humus horizon, bleached podzolic or eluvial horizon, and iron-illuvial or clay-illuvial horizon with some features typical of the metamorphic pale soils. According to the character of their middle-profile horizons, they can be attributed to the orders of Al-Fe-humus soils (sandy and loamy sandy varieties) and texture-differentiated soils (loamy sandy and clay loamy varieties). According to the character of their organic profiles, they can be separated as raw-humus subtypes among podzols and podzolic soils, respectively. Their specific regional characteristics - a tendency for the formation of a cryohumus horizon, clay illuviation, iron illuviation, and specific pale metamorphism of the mineral mass (pale metamorphized) (clay-illuvial subtype) - are also reflected at the subtype level. These characteristics can be present in different combinations reflected in the corresponding names of complex subtypes. In the geographical space, these soils form a transition from typical pale soils of the cold ultracontinental semiarid climate to the soils of cold moderately continental humid climate.