Soils of floodplain landscapes of the Selenga river basin (Mongolia, Russia): formation factors, regularities of spatial differentiation, properties, fertility, biological productivity of phytocenoses

We have identified the factors of formation and patterns of soil spatial differentiation within the alluvial landscapes of the River Selenga and its tributaries (on the territory of Mongolia and Russia) depending on zonal location. It has been established that this factor affects significantly the genesis, structure, morphology and properties of soils within river floodplains. Soil diversity is represented by different types of alluvial series of synlithogenic trunk and underdeveloped soils section of the primary soil development trunk. In the steppe and dry-steppe zones the soils of the postlithogenic trunk of the halomorphic division acquire landscape significance. Alluvial dark humus soils have the properties and regimes that are closest to optimal. The formation of alluvial humus-gley soils occurs with excessive flood-ground moisture, and under the influence of the frozen-thermal factor and weak activity of the soil microbiota. We have proposed an introduction to the classification of “alluvial light-humus soils”, which are quite widespread in the floodplain landscapes of the region. These soils develop under conditions of sufficient heat supply, but severe moisture. The article provides a comprehensive agrochemical assessment of the level of fertility of alluvial soils and hydromorphic solonchaks and assesses the biological productivity of natural meadow communities.