Central image of Vertisols: evolution of concepts of their morphology and genesis

This paper discuss the changes in understanding of the central image of Vertisols and leading processes of their formation. The early concept described Vertisols as black or dark clayey soils with homogenous undifferentiated profile resulted basically of pedoturbation. The further studies discovered vertical differentiation of Vertisol attributes. The application of trench method discovered spatial heterogeneity of Vertisols with alternation of bowl and diapiric structures. Such spatial complex subsurface pattern seems to be rather common and can be found even in the absence of gilgai microrelief. A new central image of a mature Vertisol is a combination of two structural types, one being homogenous and monotonous, generally corresponding to the initial central image, and the other - heterogeneous profile with fragmented horizons. A leading process forming the new central image of Vertisols was defined as lateral shearing or plastic deformations, i.e., plastic movements and gradual upward pushing of moist material (analogy of defluction process). Pedoturbation or more exactly the vertical falling of surface material into the cracks results in the vertical mixing rather than in deformations. Micromorphological features typical of Vertisols and associated with shrink-swell phenomena, cracking, mixing and lateral shearing that are reflected in the central image of Vertisols are summarized in the paper and illustrated by microphotographs

Current trends in soil micromorphology: bibliometric approach

The analysis of publications has shown that the period of intensive development of several spheres in micromorphology in the second half of the XX century was followed by a period when micromorphology became more required in applied research. Addressing micromorphology for solving pedogenetic and taxonomic questions became reduced both in Russia and in the world. Further progress of traditional micromorphology in Russia is expected owing to application of sophisticated equipment, participation in hierarchical morphogenetic studies, as well as to the possibility for students and professionals to work with a “database” - collection of thin sections representing a broad array of soils. This work is initiated at V.V. Dokuchaev Soil Science Institute, where many thin sections are already accumulated, and most specialists worked and are now working there

Modern and relict features in clayey cryogenic soils:: Morphological and micromorphological identification.

The research was performed in the south-eastern part of Russia. Soils were formed on clayey parent materials under an extreme continental climate favorable for the deep freezing and maintenance of permafrost. Based on morphological, micromorphological, physical and chemical attributes, the soils represent a soil complex that includes Vertic Luvic Phaeozems (Clayic and Turbic) and Luvic Phaeozems (Clayic and Turbic). Decomposition, aggregation, eluviation, illuviation, pedoturbation, mineralization and hardening result from accumulation and transformation of organic matter, freeze-thaw, shrink-swell, and translocation processes, and cryoturbation. The soil complex is interpreted as polygenetic. Interpretations were made in order to differentiate modern soil processes from relict ones. The most ancient features correspond to the cold Pleistocene glacial period and include cryogenic wedges, permafrost involutions, disrupted soil horizons, cryogenic sorting of coarse material, and accumulation of the organic matter above the permafrost. A subsequent stage of pedogenesis under a warmer and wetter environment is reflected by black humus crack infillings, black humus aggregates deep in the subsoil, vertical translocation of mobile organic matter, and the formation of clay coatings. Finally, the current climate is a warmer but more arid pedoenvironment. It is recorded in the soil complex by brownish fulvic humus and the formation of vertic features. Even in this last relatively warm climatic stage, vertic features formed by shrinking and swelling processes co-exist with annual deep freezing of the soils and subsoil permafrost at a depth of about ~300 cm.Esta investigação foi realizada na parte sudeste da Rússia, e os solos em causa formaram-se sobre materiais parentais argilosos em condições de clima continental extremo favorável à congelação dos níveis profundos do solo e à manutenção do permafrost. De acordo com as suas características morfológicas, micromorfológicas, físicas e químicas, os solos representam um complexo que inclui Phaeozems Vérticos Lúvicos (Argílicos e Túrbicos) e Phaeozems Lúvicos (Argílicos e Túrbicos). Os processos de decomposição, agregação, eluviação, iluviação, pedoturbação, mineralização e endurecimento resultaram da acumulação e transformação de material orgânico, congelação-descongelação, contracção-expansão, translocação e crioturbação. Interpretou-se o complexo do solo como sendo poligenético. As interpretações foram feitas para diferenciar os processos de pedogénese modernos dos antigos. As características mais antigas remontam ao período glaciar frio do Pleistocénico e incluem cunhas criogénicas, involuções do permafrost, horizontes edáficos desorganizados, distribuição criogénica do material grosseiro e acumulação de matéria orgânica sobre o permafrost. Uma pedogénese posterior associada a um ambiente mais quente e húmido reflecte-se no aparecimento de fendas preenchidas com húmus negro, presença de agregados de húmus negro em profundidade, translocação vertical de matéria orgânica e formação de películas de argila. Finalmente, o clima actual é mais quente e mais árido e esse facto reflecte-se no aparecimento de húmus fúlvico pardacento e características vérticas. Mesmo neste último período mais quente as características vérticas formadas por processos de contracção e expansão coexistem com a congelação anual dos solos em profundidade e com o desenvolvimento de permafrost a uma profundidade de ~300 cm.Este estudio se llevó a cabo en el sureste de Rusia. Los suelos están formados sobre materiales arcillosos bajo un clima continental extremo que favorece la congelación de los niveles profundos y mantiene el permafrost. De acuerdo con sus características morfológicas, micromorfológicas, físicas y químicas, los suelos representan un complejo edáfico que incluye Phaeozems Vérticos Lúvicos (Argílicos y Túrbicos) y Phaeozems Lúvicos (Argílicos y Túrbicos). Los procesos de descomposición, agregación, eluviación, iluviación, edafoturbación, mineralización y endurecimiento resultan de la acumulación y transformación de la material orgánica, hielo-deshielo, contracción-expansión, translocación y crioturbación. El complejo edáfico se interpreta como poligenético. Las interpretaciones se han realizado para diferenciar los procesos de edafogénesis modernos de los relictos. Los rasgos más antiguos están datados del periodo glaciar frío del Pleistoceno e incluyen cuñas criogénicas, involuciones del permafrost, horizontes edáficos desorganizados, distribución criogénica del material grueso y acumulación de materia orgánica sobre el permafrost. Una posterior edafogénesis asociada a un ambiente más cálido y húmedo se refleja en rellenos de grietas con humus negro, presencia de agregados de humus negro en profundidad, translocación vertical de materia orgánica y formación de revestimientos de arcilla. Finalmente, el clima actual es más cálido pero más árido y esto se refleja a través de humus fúlvico pardo y la formación de rasgos vérticos. Incluso en este último periodo cálido los rasgos vérticos formados por procesos de contracción y expansion coexisten con la congelación anual en profundidad de los suelos y el desarrollo de permafrost a una profundidad de ~300 cm

SoilSci13_10KovdaLO.fm

Abstract-Soil organic matter (SOM) was studied in relation to vertic processes (i.e., shrinking/swelling, cracking, vertical turbation, lateral shearing, gilgai formation) in Vertisols and vertic soils of the North Cau casus in Russia, and Texas and Louisiana in the USA. Their impact on SOM properties and distribution was analyzed according to various levels of soil organization, such as soil cover, profile, horizon, and aggregate structure using chemical methods, micromorphology, isotopic analyses, and physical fractionation. The greatest variations both in the distribution and properties of SOM were found in mature Vertisols at the level of soil cover including C tot , organic carbon stocks, stable carbon isotopic composition, and SOM 14 C age, chemical composition. The distribution of SOM at the profile and horizon levels was related to the function ing of Vertisols during wet dry cycles. The isotopic and chemical study of densi granulometric fractions at the aggregate level reflected the minor role of vertic processes