Ecogeographical conditions of soil formation in the basin of the transboundary Ulz-Gol river (on the territory of Mongolia) and characteristics of the main soil types of floodplain-valley ecosystems

The article presents the hydrography of the transboundary Ulz-Gol River (on the territory of Russia also known as the Uldza River). The specific ecogeographical conditions of soil formation on its catchment area are characterized. The formation of soils is primarily influenced by the close level of groundwater and the light granulometric composition of alluvial deposits which contribute to the diversity of soils in floodplain-valley landscapes. It has been established that in the studied area the structure of the soil cover is predominantly represented by various subtypes of alluvial dark humic soils. Typical alkaline soils also have a significant distribution in the area. The soils of adjacent zonal-valley landscapes, based on the system of genetic horizons, are light humic quasi-gley soils. The soils clearly exhibit dark and light humic horizons with sandy alluvium. The soils are characterized by being quasi-gley, saline, carbon enriched, humic-infiltrated, and weak stratified. The physical and physicochemical properties, degree, and chemistry of soil salinization are described.