Tuesday, 11 July 2006
42-9

Position in the Soil Classification and Genesis of Automorphic Soils in Silty Loams in Forest-Tundra of Eastern Europe.

Alexander V. Pastukhov1, Valentine D. Tonkonogov2, and Iya Zaboyeva1. (1) Institute of Biology Komi Science Centre UrD RAS, h. 28, Kommunisticheskaya, Syktyvkar, 167982, Russia, (2) Dokutchaev Soil Institute, Russian Agricultural Academy, h. 7, Pyzhevskiy pereulok, Moscow, Russia

In the Eastern-European Plain area in the extremely northern taiga and forest tundra Gley-Podzolic soils are classified as automorphic loamy soils. The authors have characterized the automorphic loamy soils of the region. The soils are represented by the system of the related podzolic (with gleyzation features) and iron-illuvial horizons, combined with the specific cryometamorphic horizon. The podzolic horizon is poor in total and oxalate-extractable iron, can less in aluminum and silt as compared with iron-illuvial horizon. The most important feature of cryometamorphic horizon is a specific angular-grumous or friable granular, curdled at moist condition, cryogenic structure. Soil profile is weakly differentiated by silt and sesquioxides. The soil formation is the result of the processes of Gley-Al-Fe-Humus mobilization, migration, accumulation and cryogenic structural metamorphism. By morphological structure (the presence of podzolic, iron-illuvial and cryometamorphic horizons), intra-profile distribution of size particles, total iron and aluminum oxides, and oxalate-extractable iron, the studied automorphic soils of the European extreme northern taiga and forest tundra are most similar to the soils described under the different names (eluvial-gley, podzolic eluvial-gley, differentiated gleyzems, svetlozems) in the Western-Siberian Plain in the northern and middle taiga. In the area, they are widely distributed in the well-drained landscape positions in silty, mainly coarse, loamy deposits over 1 m thick. In accordance to the new Soil Classification of Russia the described soils correspond to the Type of Iron-Illuvial Svetlozems in the Order of Cryometamorphic soils. Along with the above, Gley-Podzolic Soils occur in the investigated area. They have a textural horizon and correspond to the Order of Texturally-Differentiated soils. Thus, automorphic loamy soils in the extreme northern taiga and forest tundra of Eastern Europe are traditionally classified as Gley-Podzolic soils. According to the new substantive-genetic classification principles, they are divided into two groups of high taxonomic level. They are Gley-Podzolic soils corresponding to the Order of Texture-Differentiated soils and Iron-Illuvial Clay-Illuvial Svetlozems corresponding to the Order of Cryometamorphic soils. In this connection even slight distinctions of particle size distribution of the deposits (coarse and fine loams) play an important role because they form middle horizons, responsible for the Orders of the soils. Moreover, the investigated soils are genetically closely related. They differ by the middle horizon features which are very important for the soil taxonomy. Their similarity lies in the structure and genesis of the upper part of profile, most sensitive reacting to environment changes. In addition, European Svetlozems are an internuncial link in the genetic soil taxonomy: Texture-Differentiated Gley-Podzolic soils Clay-Illuvial Svetlozems Svetlozems (Western-Siberian).

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