Soils of the southwestern part of the Dzhulukul Depression in the Altai Republic

Abstract

Soils of the southwestern part of the Dzhulukul Depression in Ulagan district of the Altai Republic have been studied. They belong to two soil divisions: Al-Fe-humus soils (with various types of podburs) and iron-metamorphic soils (rzhavozems). The soils within the eluvial part of the studied catena—iron-illuvial soddy podburs—are developed from the residuum of magmatic and metamorphic rocks with high (up to 80 vol %) content of gravels and coarse rock fragments. Their high porosity favors downward migration and precipitation of humus-iron compounds on the surface of gravels and mineral grains in the illuvial horizon. The soils of the accumulative part of the catena—permafrost-affected raw-humus pod-burs and gleyic podburs)—are developed from moraine deposits of loamy-sandy texture with up to 30 vol % of gravels. In these soils, the features of the Al-Fe-humus migration are weakly pronounced; the soils are underlain by the waterproof frozen horizon (permafrost), have high humus content, and have thixotropic properties in the lower horizons. Their reaction is slightly acid to neutral, and their base saturation is up to 80%. These characteristics do not meet the criteria of podburs as defined in the new Russian soil classification system. Their origin may be related to the local mixing of weathering products of different bedrock materials, including magmatic, metamorphic, and sedimentary rocks during the deposition of moraine sediments. Iron-metamorphic soils (rzhavozems) are formed on convex parts of slopes from the residuum and colluvial derivatives of magmatic and metamorphic rocks (granite, metamorphic slates, red-colored sandstone, etc.). A distinctive feature of these soils is their ocherous-brown color and a considerable content of gravels in the entire profile. The chemical properties of rzhavozems resemble those of the Al-Fe-humus soils of automorphic positions: acid and slightly acid reaction, low base saturation, and a relatively high content of organic carbon in the organic and mineral horizons.