Диагностика процессов почвообразования в аллювиальных луговых почвах речных долин таёжно-лесной и степной зон

Abstract

Long-term data obtained from studying a wide range of alluvial soils formed on floodplain terraces of rivers in the taiga-forest and steppe zones of the European and West Siberian Plains are summarized. The microstructure of alluvial soils in the central part of the floodplain terraces of a number of large rivers such as the Ob, Pechora, Northern Dvina, Ugra, Oka, Desna, Klyazma and Tikhaya Sosna Rivers was studied using the methods of micromorphology and scanning electron microscopy. We identified the features and diagnostic signs of flood-alluvial and elementary soil-forming processes that determine the formation of the profile of alluvial meadow soils. All bioclimatic zones are characterized by high aggregation and porosity of humus-accumulative horizons. However, humus of the mull and moder type is formed in the taiga-forest zone, while in the steppe – only mull. Diagnostic signs of zonality in alluvial meadow soils are the shape and size of Fe-Mn formations, clay deposits and cutans, gypsum and carbonates. In the taiga-forest zone the ecological conditions of the high floodplain are marked by the presence of Fe-Mn new formations in the form of nodules and the presence of clay deposits in the lower part of the profile. At the same time, the low floodplain is marked by Fe-Mn new formations in the form of flakes and spots, clay cutans (films) in the pores and around the units at the bottom of the profile. Alluvial meadow soils of the steppe zone are characterized by the presence of new formations of gypsum and carbonates in the lower part of the profile, and the absence of illuvial cutans. Intensive agrogenic use of alluvial meadow soils promotes the disaggregation of the humus-accumulative horizon, the leaching of amorphous forms of humus from it, and the reorientation of clay minerals into a horizontal arrangement in the horizons located below the plow base.