Soils of Lacustrine Depressions of Pulsing Chloride Lakes in Endorheic Areas of Central Asia: Morphology, Physicochemical, and Geochemical Features

Data on saline soils of endorheic lacustrine depressions in the areas of ultracontinental climate with 25–30-year-long cycles of lakes level fluctuations are obtained for the first time. Fluctuations correspond to alternating arid and humid climatic phases. Different soils are formed in landscapes adjacent to strongly mineralized chloride lakes of the southeastern Transbaikalia: gley solonchaks (Gleyic Solonchaks (Loamic, Chloride)) in superaqual–subaqual positions; humus-gley saline soils (Calcaric Mollic Gleysols (Arenic, Endosalic, Sodic)) in superaqual positions; and light-humus saline soils (Fluvic Kastanozems (Epiarenic, Amphiloamic, Sodic)) in eluvial-superaqual geochemical positions. Salinity rate of the studied soils varies. The cations are dominated by sodium, and among anions chlorides are most common in solonchaks and in humus-gley topsoils. Soda-chloride and chloride-soda anion composition prevails in other soils. Gley solonchaks are characterized by strongly alkaline pH, high content of carbonates, and predominance of Na + among exchangeable cations. Many chemical elements are concentrated in the solonchakous horizon (Sr, S, Li, Mg, and Ca), and a high content of As is a regional feature. The humus-gley saline soil is similar to the light-humus saline soil by physicochemical parameters and to solonchaks by the element composition and texture. Both features are related to periodical functioning of this soil in semihydromorphic or hydromorphic regimes during arid and humid phases, respectively. The high groundwater level contributes to the enrichment of soils with the elements typomorphic for lake water. The paleohydromorphic formation stage has been recorded in lower layers of light-humus saline soil as a high content of easily soluble salts and carbonates. The geochemical specificity of soil-forming rocks is the significant As accumulation and Li, Ba, and Pb elevated concentrations. It has also been revealed that the low Ca/Sr ratio is inherent to their geochemical composition. The cluster analysis of parameters of the studied soils shows that both dynamic and stable soil parameters are reflected in humus-gley soil, therefore, it is recommended for monitoring the dynamics of endorheic lacustrine ecosystems in Central Asia with cyclic climatic phases.