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Little-studied soils of larch woodlands, mountainous tundras, and cold alpine barrens of the Polar Urals under different geomorphic conditions have been described, and their classification position has been determined using the profile-genetic approach. Morphological, physicochemical, and chemical characteristics of the soil profiles formed on mafic and ultramafic rocks are analyzed. It is shown that dominant soils developing from these rocks under larch stands in the Polar Urals are represented by podzolized and humus-illuvial podburs. Both soils are classified as Entic Podzols (Skeletic) according to the WRB-2015 system. In the mountainous tundra, mucky oxidized-gley gleyzems (Reductaquic Gleysols (Thixotropic)) and gray-humus soils (Skeletic Phaeozems) are formed. In the extreme conditions of cold alpine barrens (900–1033 m a.s.l.), different subtypes of gleyzems (Reductaquic Gleysols and Turbic Gleysols (Abruptic)) are locally developed. Deposition of predominantly aboveground plant litter and its slow mineralization on the mineral surface in these soils lead to the development of raw-humus and peaty horizons with a wide C/N molecular ratio. [ABSTRACT FROM AUTHOR]

The basic three-component classification system of soils of the world was published by V.M. Fridland in 1982, and its profile-genetic component was taken as a basis for the classification of soils of Russia (1997– 2004–2008). Unlike the former systems, in that of Fridland the priority is given to soil properties, and this conceptual background is transferred into the new Russian system. The substantive-genetic principles of both systems are implemented in diagnostic horizons and genetic properties; both systems have similar hierarchy of taxa, nomenclature, keys. Changes introduced in the classification of soils of Russia derive either of proposals forwarded in the course of its application, or of information accumulated. They concern the improvement of definitions and introduction of new diagnostic elements; however, the main principles are preserved in the existing and forthcoming versions.

Results of 24 soil monoliths studying in the collection of Dokuchaev Central Soil Museum were analyzed in terms of diagnostic criteria in Russian soil classification system; these were chestnut, brown aridic, pale and cryoaridic soils. The topsoils of chestnut and brown aridic soils meet the criteria for the light-humus horizon (AJ), but their values in Munsell readings proved to be lower. In pale soils, the upper horizons were identified as gray-humus instead of light-humus ones as prescribed in the system. The cryohumus AK horizon, diagnostic for cryoaridic soils, is peculiar by the abundance of reddish frost-fragmented plant residues (detritus). We failed to differentiate metamorphic BM and xerometamorphic BMK horizon, they had more features of the latter. Both horizons are similar to the pale-metamorphic BPL horizon in color, although the BPL has a definitely weaker structure displaying some cryogenic features. These are less prominent in cryoaridic soils than in pale soils, hence, the diagnostic BPL horizon in cryoaridic soils may be removed to the category of diagnostic property. A similar re-evaluation may be proposed for the carbonate-textural CAT horizon: to consider it as a diagnostic property in the carbonate-accumulative horizon (ВСАt). The ВСА horizon in all soils studied differed by carbonate pedofeatures, namely, segregations in brown and chestnut soils, impregnations in pale soils, impregnations and coatings in cryoaridic soils.

For the first time, a detailed diagnostics and classification of soils of the Suntar-Khayata Range have been performed. This study is a continuation of long-term soil research in the Verkhoyansk mountainous soil province. The morphogenetic properties of soils in different altitudinal zones of the Suntar-Khayata Range are described, and the position of these soils in the new Russian soil classification system is determined. The Suntar-Khayata Range (63° N; 139° E) is found near the Pole of Cold of the northern hemisphere and is characterized by the distinct altitudinal zonation. In the study area, parent materials are represented by sandstone and, less often, by siltstone. In the warm season, the upper boundary of permafrost can be clearly traced only in the profiles of low-stony soils on the floodplains. The vertical zonality in the studied area includes the following zones: the valley zone (<900 m a.s.l.) with alluvial soils (Skeletic Fluvisols), the mountainous taiga zone (900–1300 m a.s.l.) with a predominance of podburs (Skeletic Spodic Cryosols), and the subalpine shrub (1300–1500 m a.s.l.) and mountainous tundra (>1500 m a.s.l.) with a predominance of lithozems (Leptosols). All the soils are relatively shallow, stony, and coarse-textured; their organic horizons are thin, and raw-humus (AO) horizons tend to predominate. Gley features are absent in the soil profiles. The soils have an acid or a slightly acid reaction, low base saturation (except for alluvial soils), and signs of organic matter illuviation. The results of this study can be used to expand the database on soils of poorly studied cold continental mountain regions of Eurasia. [ABSTRACT FROM AUTHOR]

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.

It is shown that the profile principle of arable soils classification, implemented in the new classification of Russian soils is not correct. The separation of 2-3 new soil types in a single tilled soils was conducted only according to the presence of the arable layer. The profile of the arable soil was not analyzed. This led to serious errors, overloading of the classification by excessive, non-existent types of soils that do not carry useful information and, therefore, distorting the reality. The analysis of properties and processes in arable soils considered in the article has shown that just plowing, crops cultivation and economic activities do not change significantly the processes that formed the soil before plowing. They lead to changes of some properties in the arable soil and, however, do not reach the new natural-agrogenic horizon. Therefore, it will be correct to separate the arable soil on the level of the subtype of the soil, which was tilled. Some changes, which occurred in the properties of tilled soils are in fact new specificities superimposed on natural horizons which were created in virgin soils. Precisely this was done in the Classification and Diagnostics of Soils of the USSR (1977) during the analysis of profiles for cultivated, reclaimed and cultivated soddy-podzolic soils. However, these soils were related to the new type - the type of cultivated soddy-podzolic soils. As it is seen in the name of the soil, the genetical connection with the virgin soils was preserved. If this soil is also eroded, it will be proposed to determine the soil water erosion degree and to separate it already at the level of a type within a subtype of arable land. This could be done by the analysis of profile remains, and by using the comparative-geographic method. A new process in arable soil, which is able to form a different soil horizon, and which is not manifested only in the form of various specificities, might occur only with great efforts in soil cultivation or radical reclamation: irrigation, drainage. Only when a new horizon appears in the arable soil, according to the principles indicated in the soil classification, a new type of arable soil is separated. A significant change in the humus horizon in arable soddy-podzolic soil: its thickness, color, humus content, structure, and other properties may serve as the basis for separation of a new type - the cultivated soil type. The proposed approach will make it possible to compose a highly informative substantive-genetic classification of soils not only for natural, but also for various arable soils.

The whole complex of soil properties formed during a long process of evolution is used in soil diagnostics. Following the genetic approach, which proposes the designation of a specific diagnostic horizon that represents stages of specific urban synlitogenic soil formation on thick human-made deposits, we face the problem of separating truly soil horizons from layers of man-made deposits, as both contain significant amounts of artefacts. In addition, they have similar chemical and physical-chemical properties corresponding to general geochemical characteristics of the urban environment. A comparative analysis of morphological and physical characteristics was conducted for several soils of loamy texture within the city of Moscow, Russia. Their morphological descriptions were accompanied by determinations of bulk density, saturated hydraulic conductivity and penetration resistance. For the analysis of morphological and physical properties, soil diagnostic horizons were arranged in four groups (synlithogenic urbic humus horizons, postlithogenic humus horizons, technogenic layers and horizons inherited from natural texturally-differentiated soils). Most of the studied soil profiles had significant contents of solid inclusions (domestic waste and building rubble) that allowed us to define them as Urbic Technosols, according to the WRB soil classification system. It was confirmed that, in addition to specific chemical and morphological properties, man-made urban soils had specific physical characteristics. The abundance of inclusions of building rubble and domestic waste had a strong influence on physical properties such as bulk density and saturated hydraulic conductivity. Heterogeneous distribution of such properties within urban soil profiles could be considered as their characteristic feature. As a result, this study confirmed the identification of certain diagnostic horizons by establishing statistically significant differences in their bulk densities and saturated hydraulic conductivity. Penetration resistance was shown to be a less informative parameter in this study. We believe that more data on physical properties of different types of horizons should be accumulated for making it possible to establish typical values of physical characteristics of such horizons. [ABSTRACT FROM AUTHOR]

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- and N- have their maximums reaching 140 and 30 mg/kg, respectively, in the surface soil horizons. [ABSTRACT FROM AUTHOR]

On the basis of the profile-genetic approach, diagnostic features of poorly studied mountainous soils under larch forests and woodlands in different geomorphic positions of the Subpolar Urals were identified, and their classification position was determined. The morphological, physicochemical, and chemical characteristics of the studied soil profiles were described. It was found that the soil cover under blueberry–moss larch stands is mainly composed of iron-illuvial svetlozems and iron-illuvial podzols. Both soils were identified as Albic Podzols (Skeletic) in the WRB-2015 system. On the outcrops of calcareous rocks on slopes of river valleys, gray-humus soils (Calcaric Leptosols (Skeletic)) and iron-illuvial podzols were described. They occupy small areas and can be referred to as rare soils in the studied region. Near the upper treeline, lithozems (Lithic Leptosols (Skeletic)) and podburs (Entic Podzols (Skeletic)) are developed; these soils are common in the mountainous tundra landscapes. The accumulation of plant litter on the soil surface and its slow mineralization predetermine the raw-humus and peaty nature of the upper horizons with a broad C : N molecular ratio. [ABSTRACT FROM AUTHOR]

The paper presents the establishment of the Bulgarian soil classification and the outcomes of large scale mapping services for arable land in the country at scale 1:10 000 and to outline the correlation and harmonization issues with the international soil classification systems. The latest WRB edition (IUSS Working Group WRB, 2015) aiming at the guidance of the newest issue with the diagnostic assessment in broader aspect covers not only Europe. In this paper, we present the drafting of the soil classification issues including objectives towards the national implementation of the international soil classification systems, outlining the correlation and harmonization including WRB (2006), WRB (2015), Soil Taxonomy (Soil Survey Staff, 2014) and FAO-UNESCO (Revised Legend of the World Soils, 1990) as well as basic steps to be taken, to achieve decision making on the basis of soil quality maintenance and enhancement. It will also serve as a call for action to encourage more EC assessments at the national level, but also as a primer for the inclusion of new suggestions. [ABSTRACT FROM AUTHOR]

Two classification systems under comparison differ in objects, terminology, hierarchical levels, and approaches to identify soils. However, they have some common features: both systems are oriented to soil properties and apply the pedogenetic concepts, on one hand; on the other hand, the results, namely, some of the soil taxonomic units are similar. The second-level units of WRB, representing the classification rather than the reference base, display a certain correlation with the subtype level in the Russian soil classification system. This level in two systems may be qualified as a really active, and it contains the most complete genetic characteristic of a soil; moreover, there is a similarity in criteria for qualifiers in WRB and genetic features (producing subtypes) in the Russian system. The difference between two classification systems is manifested in the number and essence of diagnostic horizons because they perform different functions. In the International system, they mainly serve for recognition of soils (in the key), while they directly identify genetic soil types in the Russian system.

Previous work has been put into the creation of a comprehensive soil classification system (CSCS) using a harmonised dataset of 23 soil properties at 18 depth intervals. The classification consists of selected soil taxa from the US Soil Taxonomy, World Reference Base for Soil Resources, the Australian Soil Classification, and the New Zealand Soil Classification. In this paper, the CSCS was tested for allocation using data for from 44 soil profiles collected in Iran. A distance-based algorithm was used to allocate and name the soil profiles according to the CSCS. It was found that 36 Iranian soil profiles are close to the existing taxa of the CSCS in the taxonomic space. Three Iranian profiles with distances between 25 and 30 taxonomic units to the closest CSCS taxa were added to the CSCS and assigned with new systematic names. Allocating the remaining 5 Iranian taxa would require regenerating the nomenclature system. The CSCS has shown advantages for allocating soil profiles from other regions of the world other than the USA, Australia and New Zealand. It also enables cross-referencing with existing soil classification systems. In the future, the CSCS can be further improved by adding taxa from other global or regional soil classification systems. [ABSTRACT FROM AUTHOR]

The soils in the area of the northern pole of cold located on the interfluve between the Yana and Adycha rivers within the spurs of Kisilyakh Ridge included in the mountain system of Cherskii Ridge have been studied for the first time. The profile-genetic approach has been applied to describe the soils and determine their classification position. It is found that the major soil types in this region are the soils of the postlithogenic trunk belonging to the orders of lithozems (Cryic Leptosols), gley soils (Gleyic Skeletic Cryosols), and Al-Fe-humus soils (Spodic Skeletic Cryosols). The ecological ranges of altitudinal zones- the taiga zone with various types of lithozems below 630-700 m a.s.l. and the tundra zone with combinations of gley and nongley cryogenic soils above these heights-have been established. The development of gley or nongley soils is specified by the local orogenic and lithological conditions and slope aspect, which, in turn, control the degree of drainage and the presence and character of permafrost. In the profile of mountainous gley soils (gleyzems) with shallow ice-rich permafrost, cryogenic processes and features typical of the analogues of these soils on plains-cryogenic cracking, cryoturbation, solifluction, thixotropy, oxiaquic features above permafrost, saturation of the soil profile with mobile humus, etc.-are typical. [ABSTRACT FROM AUTHOR]

As substâncias húmicas que compõem a matéria orgânica do solo participam de forma ativa dos processos pedogenéticos do solo, em especial dos horizontes diagnósticos O e H hístico, A chernozêmico, A húmico e B espódico. Este trabalho teve como objetivo determinar o teor de C orgânico das substâncias húmicas e avaliar sua influência na separação de horizontes diagnósticos. Foram utilizados 56 horizontes diagnósticos de diferentes regiões do Brasil, 52 superficiais (H hístico, A chernozêmico, A proeminente, A húmico e A moderado) e quatro subsuperficiais (B espódico). Nesses solos, foram feitas a caracterização química e física, e também de C orgânico, da fração ácidos fúlvicos (C-FAF), fração ácidos húmicos (C-FAH) e humina (C-HUM), as relações C-FAH/C-FAF e C-EA/C-HUM (C-EA = C-FAF + C-FAH) e a percentagem das frações em relação ao C orgânico total (COT), sendo as variáveis submetidas à avaliação por análises multivariadas. Nos horizontes orgânicos, o H hístico apresentou maiores valores e equilíbrio entre o C-HUM e o C-FAH. Na maioria dos horizontes minerais, observou-se predomínio do C-HUM, seguido pelo C-FAH nos horizontes A chernozêmico e A húmico e pelo C-FAF nos horizontes A proeminente e A moderado. Nos horizontes B espódico, foi observado predomínio variável de C-FAF e C-FAH. Com a análise de variáveis canônicas, identificaram-se as variáveis que poderiam ser utilizadas para a separação dos tipos de horizontes diagnósticos. Usando a análise de agrupamento, separaram-se os tipos de horizontes com menor influência da matéria orgânica. Pela análise discriminante, obtiveram-se resultados satisfatórios na classificação dos horizontes diagnósticos com base nas variáveis das substâncias húmicas, quando comparados à classificação original. Os resultados das análises multivariadas indicam que a distribuição do C das substâncias húmicas pode ser utilizada para separar os tipos de horizontes diagnósticos ricos em C orgânico.The humic substances that compose the soil organic matter participate actively in the pedogenetic soil processes, particularly in the Histic (Histic), Mollic (Chernozemic), Umbric (Humic) and Spodic (Spodic) diagnostic horizons. This study aimed to determine organic C amounts in the soil humic substances and evaluate their applicability for diagnostic horizons recognition. Fifty-six diagnostic soil horizons from different Brazilian regions were used, 52 from surface horizons or epipedons (H histic, A mollic, A proeminent, A humic and A moderate) and four subsurface (B spodic). Soil chemical and physical properties and the organic C amounts in the fulvic acid fraction (C-FAF), humic acid fraction (C-HAF) and humin (C-HUM) were determined by well-established methods. The C-HAF/C-FAF ratio and C-AE/C-HUM ratio (C-AE = C-FAF + C-HAF) and the percentage of each fraction in the total organic C (TOC) were calculated and all data were submitted to multivariate analysis. In the organic horizon, the amounts of H histic were highest and C-HUM and C-HAF amounts similar. C-HUM was predominant in the major mineral horizons, followed by C-HAF in the A mollic and A humic horizons, and by C-FAF in the A proeminent and A moderate horizons. A greater proportion of either C-FAF or C-HAF were observed in B spodic horizons. Based on canonical analysis, we identified the variables that could be used to separate diagnostic horizon types. The horizons with low influence of organic matter were distinguished from those with greater influence by cluster analysis. With the discriminatory analysis, satisfactory results were obtained for the classification of diagnostic horizons based on humic substance variables, compared to the standard classification. Multivariate analysis indicates that the distribution of C in the humic substances can be used to separate C-rich diagnostic horizon types of tropical soils in Brazil.

The objective of this research was to investigate the morphology, genesis and classification of soils formed on the Sygera Mountain in Tibet. Five typical soil profiles were collected in genetic soil regions, such as alpine frozen desert soil, alpine meadow soil, brown soil, etc., and their soil-forming environments were investigated, and then soil samples were taken from various soil layers of the soil profiles for analysis of physical and chemical properties. According to the current diagnostic criteria of the Chinese soil taxonomy (CST) and world reference base for soil resources (WRB) classification systems, the five soil profiles were identified and classified. Results showed that (1) the main diagnostic horizons and diagnostic characteristics are mollic epipedon, umbric epipedon, cambic horizon, lithic contact, aridic soil moisture regime, udic soil moisture regime, gaelic soil temperature regime, cryic soil temperature regime, and base saturation. (2) Based on the ' Key to the Chinese Soil Taxonomy (Third edition)', the five soil profiles could be sorted into two orders, two suborders, three groups, and three subgroups (lithic calic-cryic aridisols, typic molli-cryic cambosols, and typic umbri-cryic cambosols). However, based on WRB, the five soil profiles are classified into two orders, four suborders, four groups, and four subgroups (yermic calcisols, humic cambisols, dystric cambisols, and haplic cambisols). (3) The differentiations of the classification of the five profiles between the two classification systems varied significantly with classification level, and the relationships between the various classification levels of CST and WRB are complicated ones rather than the simple one-to-one type. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil pH play a crucial role regulating microbial communities along with diagnostic horizons. • C horizons had greater variations in microbial communities compared to Ah horizons. • Soil microbiomes can be served as quantitative index for soil classification. Soil depth greatly affects soil microorganisms due to the intensive changes in soil physical and chemical properties along soil profile. However, little is known about microbial communities in diagnostic horizons of soil profiles among different soil types, which is the key to understanding the biogeochemical cycling in deep soils. Herein, we collected soil samples from eight agricultural fields across Heilongjiang Province of China, which belong to two suborders of Isohumosols (Ustic and Udic), based on the diagnostic horizons. The microbial community abundances, diversities and structures were comparatively investigated using qPCR and high-throughput sequencing methods. Results showed that the abundances of bacteria, archaea, and fungi consistently decreased more than by 90% in C horizon (parent material horizons) compared with those in Ah horizons (humus horizons). In items of alpha diversity, the fungal diversity decreased by>50%, while archaeal diversity increased by more than two folds. The bacterial diversity varied along soil depths at different sites. In addition, all soil microbial community structures were obviously divided into Ustic and Udic groups, and a distinct succession of microbial communities was detected from Ah horizons to C horizons at individual sites. Moreover, compared to Ah horizons, the difference of microbial community structure between Ustic and Udic Isohumosols was greater in C horizons. Canonical correspondence analysis (CCA) and random forest (RF) analysis revealed that pH was the most important soil factor regulating the microbial communities among all tested edaphic variables. More importantly, using machine-learning methods, we found that soil microbial communities can be used to accurately predict two suborders of Isohumosols and diagnostic horizons. Overall, the findings of this study highlight that the microbial data of diagnostic horizons can be served as quantitative indices for the soil classification, and this conclusion needs to be verified in the future research using more soil types. [ABSTRACT FROM AUTHOR]

Abstract: Aggregate porosity is the result of structural development, in turn controlled by pedogenic processes, which allow a soil to acquire specific characteristics and to lose those more related to the parent material. Porosity in sediments can be evaluated through simple packing models that provide an ideal porosity (Φideal), which is based on soil particle size distribution only. As such they are not suitable for complex systems such as soil and aggregates. We evaluated therefore if the disagreement between ideal porosity and experimental data (ΦHgT) is related to chemical properties and to the presence of specific diagnostic horizons, hence to soil development. The porosity underestimate, evaluated as ΦHgT/Φideal ratio, was the highest (up to 5-times) in Inceptisols and in their cambic horizons or in mollic epipedons. Thus, where pedogenesis is expressed enough to influence soil properties to such an extend to define diagnostic horizons, the ideal porosity model failed the most in describing the complexity of the void arrangement in the aggregates. Organic matter (OM) is a key factor in determining structural complexity, not only through its accumulation in surface horizons, as evidenced by the correlation between ΦHgT/Φideal and organic carbon (r=0.58), but also in deeper horizons. At the soil surface, independently from soil orders, OM contributed to structure development also through the poorly decomposed fractions. However, as also suggested by the weak linear dependence of the organic carbon-to-total nitrogen ratio on the porosity underestimate (r2 =0.51), it was evident that neither the quantitative, nor the qualitative data could fully explain the effects OM had on structure. Some specific spatial arrangement of particles, such as the typical hierarchical aggregation of mollic epipedons, must be taken into account to better understand the OM effects. In the subsoils, where the weathering process has led to a more complex structure, the effect of OM is enhanced by the concomitant presence of charged mineral surfaces. In Inceptisols, calcium is a co-dominant factor in structural development (r=0.84), as expected when the formation of clay polyvalent cation-organic matter complexes occurs. In the least developed soils, pedogenic processes had a minimal effect on soil properties, and the aggregate porous system still retains some of the characteristics of the parent material, leading to a less pronounced underestimate by the ideal porosity model. [Copyright &y& Elsevier]

Abstract: To investigate man''s role in the creation and evolution of soils in areas of large scale farming, and to investigate the main morpho-descriptive aspects of the related soils, a survey was carried out in south eastern Sicily, Italy, where, as common to other regions of the Mediterranean basin, there are wide areas with anthropogenic soils due to large scale farming activity. The complex genesis pattern of these anthropogenic soils, which shows a double sequence of man-made horizons, sideways oriented to the soil surface, does not allow their classification as Technosols, because their composition is not dominated or strongly influenced by artefacts or human-made materials as is the case for Technosols. According to the principles of the WRB (World Reference Base for Soil Resources), these soils should be regarded as being within the Anthrosols reference soil group (RSG). For their classification, the “geomiscic” horizon, not listed among the diagnostic horizons of the WRB, is proposed as a new diagnostic horizon for the Anthrosols RSG. The geomiscic horizon can be succinctly defined as “a horizon that develops when a layer, at least 30 cm thick of different kinds of earthy materials, is added to the soil using earthmoving equipment. For farming purposes this layer is subsequently deeply mixed into the underlying soil using heavy machinery. Its colour is related to the source materials and generally the layer is not parallel to the surface of the soil”. [Copyright &y& Elsevier]

Abstract: The essence of pedogenesis, as a synergetic process, consists in generation, selection, accumulation and differentiation of the solids produced in the course of bio-abiotic processes functioning within a soil body. Soil formation in the broad sense is the result of synergetic processes of self-organization of an in situ soil system during its functioning in time and space. Soil formation, sensu stricto, is the transformation of the solid-phase lithomatrix (parent material) of the soil system into the pedomatrix (soil body, soil mantle). Pedogenesis is perceived as an integration of specific pedogenic processes (SPP); each of them characterized by a definite set of solid-phase pedogenic features. Each soil body is formed by a combination of some SPP. The whole set of SPP may be grouped in accordance with their essence, characteristic times (rates) and reversibility-irreversibility. In terms of characteristic times (rates) they may be arranged in three main groups: rapid (101–2 years), medium-rate (103–4 years), and slow (105–6 years). Soil system functioning and soil formation are intimately linked but fundamentally different processes: the former is infinite in time, if not interrupted by external factors; the latter, as any self-organization process, is finite in time and tends to reach a steady state. The theoretical grouping of the pedogenic processes according to their essence and self-termination or quasi-equilibrium is proposed. All the diagnostic soil horizons (as defined in WRB) are perceived as more or less stable and “mature” degrees of soil self-development. They may be separated into favorable and unfavorable with respect to their suitability for biota. Favorable conditions are generally common in 12 out of 39 diagnostic horizons and properties (32%). They are mainly influenced by biotic fluxes and cycles, which are comparable to, or exceed, abiotic fluxes and cycles in their strength and capacity. In this case, biota transforms and improves the environment rather than adapts to it. Unfavorable conditions are more common in 27 out of 39 diagnostic horizons and properties (68%). They are influenced by the mutual action both of biotic and abiotic fluxes and cycles. In this case, biota adapts to the environment rather than improves it. [Copyright &y& Elsevier]

Gypsic and petrogypsic horizons occur in large areas of arid and semiarid regions of the world. The occurrence of gypsum in soils is considered a key feature by most soil classification and mapping systems that have coined specific names for these soils and horizons. However, the current methodology for description and definition of gypsic and petrogypsic horizons in the two most popular soil taxonomic systems “Soil Taxonomy” and “World Reference Base for Soil Resources” (WRB) does not address sufficiently the advances in knowledge of the constitution, genesis, and behaviour of gypseous horizons. Some of their basic statements, like the presence of secondary gypsum or the degree of cementation, are often ambiguous in the field. Further, the definitions of gypsic and petrogypsic horizons should not be interlocked, each definition should be based on field characteristics linked with microscopic and hydric properties that control the durability and the life-supporting capability of gypseous soils. The avoiding of confusion between gypsum-rich and calcium carbonate-rich horizons when grouping soil taxa or diagnostic horizons by means of soil-forming processes is stressed. [Copyright &y& Elsevier]

Several attempts were made in the past to identify high-level soil microfabrics, following the ideas of Kubie¨na. They resulted in proposals to identify specific fabric types, soil materials, somas, formations, or morphotypes, based on the combinations of micromorphological characteristics of the studied horizons of soils. These units present complex (integrated, typical, and central) micromorphological images of soil horizons or materials. Using the available information on Russian soils, the author defined the “micromorphotypes” of soil horizons by illustrating this approach by two examples of simple and complicated genetic horizons. Emphasis was put on genetic and diagnostic aspects of micromorphological interpretations, which is traditional for Russian micromorphological studies. Moreover, the definition of “micromorphotypes” was derived from the ideas of diagnostic horizons, which serve as a base for the new Russian soil classification system. Examples of “micromorphotypes” are discussed for a Chernozem and major mineral horizons of loamy soils with textural profile (correlated with Albeluvisols in the WRB system). They illustrate the morphogenetic principles applied, and also bring to light some problems concerning the choice and hierarchy of criteria used for a number of soils.This “micromorphotypes” approach may contribute to the diagnostics of horizons for soil classification, for detection of human impacts, and for the identification of paleosols and their diagenetic changes. To facilitate contacts with nonprofessionals in micromorphology, a simple terminology and a priority of pedogenic principles seem to be preferable. [Copyright &y& Elsevier]