Biophilic Elements, Mineral Composition, and Microbiological Peculiarities of Soils of Halomorphic Oases of the Intracontinental Endorheic Uldza-Torey Lake Basin

The content of biophilic elements in soils and minerals of shore depressions of highly mineralized chloride lakes in the Uldza-Torey endorheic basin (Dauria, Russia) and the microbiota involved in the cycles of these elements have been comprehensively studied for the first time. The data on the gross content and mobile forms of biophilic macro- (N, P, K, Na, Ca, Mg, Fe, and S) and microelements (Mn, Zn, Cu, Cr, Ni, and Co) in soils of the local biota concentration of the Uldza-Torey basin reflect differences in the geosphere–biosphere interactions of biotic and abiotic components in quasi-gley solonchaks and saline humus–gley and saline light-humus soils. The great significance of halomorphic soils for preserving the biodiversity of steppe territories (Dauria, Transbaikalia) has been established. Maximal concentrations of the total content of biophilic elements and mobile forms of nitrogen, sulfur, calcium, sodium, manganese, and magnesium have been revealed within the Sg,ca horizon of the quasi-gley solonchak. This layer is characterized by the highest index of microbial diversity; a significant proportion of taxa participating in the cycles of biophilic elements; and the formation of new minerals with wide variations of the silicon, aluminum, and sodium content. The underlying horizons of solonchak (CQs) are enriched with sodium, magnesium, and sulfur under the impact of sulfate–chloride–sodium groundwater. Calcite, calcium amphiboles, and monocyte predominate in mineralogical composition. The enrichment of solonchaks with mobile forms of biophilic elements and the presence of various minerals containing Na, Ca, Mg, Fe, and rare-earth elements (Ce, La, Nd, Sm, and Th), confirm both the sodium and the rare-earth hypotheses of lithophagia of animals. A significant deficit of most gross and mobile forms of biophilic elements, a decrease in microbial diversity, and the predomination of minerals typical for acid rocks and rarely of basites have been revealed in the upper horizons of humus–gley saline and light-humus saline soils. The lower layers formed by paleohydromorphic lake sediments contain oxides with a low proportion of chlorine, sulfur, and sodium (8–15%) and are enriched with easily soluble salts and mobile forms of sodium and sulfur. The content of other biophilic elements is estimated as low and very low.