Zonal,provincial, lithological,and geomorphic features of soil salinization in the Southern federal okrug of Russia

The relationships between soil salinization and the zonal and provincial bioclimatic conditions, the lithological composition of the sediments, and the geomorphic features of the territory have been analyzed for the Southern federal okrug of Russia. It is shown that the lithological and geomorphic conditions (relief, salinity of parent materials, degree of drainage, and the depth of saline groundwater) play an important role in the distribution of salt-affected soils against the background of the more general regularities specified by the climate. The participation of salt-affected soils in the soil cover of the Southern federal okrug increases in the eastward direction from the forest-steppe zone to the semidesert zone in agreement with an increase in the aridity and continentality of the climate. The chemical composition of soil salts also changes: the sulfate and soda-sulfate types predominate in the forest-steppe zone; the sulfate type or the sulfate type with the participation of soda, in the steppe zone; the sulfate-chloride type, in the dry steppe zone; and the chloride type, in the semidesert zone. The lithological and geomorphic conditions within the particular zones and provinces affect the distribution pattern of the salt-affected soils and the degree and chemistry of the soil salinization. The areas of salt-affected soils were calculated with the use of a digital version of the Map of Salt-Affected Soils of Russia (1: 2.5 M scale) with due account for the participation of these soils in the soil cover of the particular delineations and the data on the depth of the upper boundary of the salt-bearing horizons, the degree and chemistry of the soil salinization, and the area of solonetzes and solonetzic soils.