Soil Formation in the Taiga–Steppe Ecotone of the Selenga Mountains, Western Transbaikal Region

Resumo

A new view on the genesis and properties of soils in landscapes of the taiga–steppe ecotone in the Selenga Mountains of western Transbaikalia is suggested with due account for the modern approaches toward soil classification in Russia. The specific environmental conditions—dry and sharply continental climate, mountainous topography with pronounced intermontane depressions, and predominantly coarse-textured parent materials—affect the pedogenesis. Soddy-podzolic soils (Albic Retisols) are formed on the interfluves, and raw-humus burozems (brown taiga soils), including residual-calcareous burozems (Eutric Cambisols) are developed on the upper parts of slopes. Eutric Cambisols are characterized by the high base saturation, a sharp drop in the humus content down the profile, and a pronounced pedogenic structural organization of the mineral mass. Albic Retisols display textural differentiation. Gray-humus and dark-humus soils are characterized by the immediate transition from the humus-accumulative part to the parent material as evidenced by the physicochemical properties. Fine sand and coarse silt fractions predominate in these soils, and second (Ca-bound) fractions of humic and fulvic acids predominate in the composition of their humus. These are base-saturated loamy sandy or light loamy soils with a neutral of slightly alkaline reaction. The middle-profile horizons are poorly pronounced. These soils compose a genetic series in the landscape-geochemical catena of the northern macroslope of the Tsagan-Daban Range.