Soils with buried humus horizons, formed in different bioclimatic conditions, were studied. Research activity in Western Siberia was carried out in Tyumen region, Tobolsk area, on a flat top part of the 30 m radical river bank. The flood plain''s soil of the Sysert river was studied in the Middle Urals in Sverdlovsk region near its merge to the Iset. The object of the research in West Siberia is the soil under the birch wood, containing the buried humus horizon, in the Middle Urals - the soil of the central part of a flood plain with several buried humus horizons. Formation of soils in Tobolsk area occurs in more continental conditions and is under the influence of a smaller amount of precipitation than in Sverdlovsk region. Samples of soils were selected on each site from a cut and holes, 5-10 cm each, within visible horizons, for the buried humus horizons - in 2-3 replications and were prepared for the analysis by a standard technique. Values of a magnetic susceptibility were defined on Kappabrig KLY-2, рН in water and salt extract were measured by pH-meter «ANION 4100», the general carbon was determined by Tyurin, group and fractional structure of humus - by Ponomareva-Plotnikova''s method. Optical density of humic acids was measured by Spectrophotometer UV-1650. Studying the morphological structure of soil profiles revealed that the soil under the birch wood has a difficult structure: the bottom thickness represents the ancient partially plowed soil, the top part - the former arable soil which has grown with the wood. The river flood plain''s soil also has a poligenetic structure which is available of three buried humus horizons the most powerful of which is the horizon [Ag], reflecting the longest and intensive process of humus formation in the past and, presumably, created in holozen''s optimum with anoher combination offactors of the soil formation embodied in its thickness. Comparison of the average maintenance ofthe sum of humic acids in the arable and buried horizons of the soil of West Siberia revealed much lower values of this indicator in the first horizon (29.87±9,11%) in comparison with the second (56.85±12.42%) that can indicate a warmer, in comparison with modern conditions, climate of the period of the buried humus horizon active functioning. The sum offulvic acids has much higher values in the arable horizon (43.53±16.45%) in comparison with the buried horizon (23.42±5.47%) that can be a consequence of drier, in comparison with modern ones, conditions of the ancient humus horizon formation. Comparing average sum of humic acids in the modern humus horizons and the buried gley horizon in the Middle Ural''s soil revealed lower values of this indicator in modern humus thickness (33.62±6.50%) in comparison with buried one (38.76±5.11%). The received results can testify a warmer climate of the active functioning period of the most ancient buried humus horizon. The fulvic acid''s sum showed lower values in modern humus thickness (15.90±2.40%) in comparison with buried one (17.80±2.36) that reflects more damp conditions of the period of formation of the ancient buried humus horizon in comparison with the modern one. Humic acids of the compared buried humus horizons differ in their spectral characteristics from those formed in modern conditions, by smaller values of chromaticity factors which means that bioclimatic conditions in the past were more optimum for forming mature macromolecules with a developed aromatic part on the studied sites in West Siberia and the Middle Urals. Thus, the existence of the powerful buried humus horizon in both soils with other humus characteristics indicates their passing a rather long stage of a humification in the past, characteristic of grassy communities. Comparing humus indicators of buried soils of Tyumen and Sverdlovsk regions, significant for climatic paleoreconstructions, allows to reveal local environmentfeatures of these territories in the Atlantic period. In West Siberia this period was much warmer and was characterized by a greater moisture content than in the Middle Urals.
|Título traducido de la contribución||Buried horizon''s humus of soils forming in different conditions|
|Publicación||Вестник Томского государственного университета. Биология|
|Estado||Published - 2012|
- 34.00.00 BIOLOGY
Level of Research Output
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