Lipid Components of Soils in Dry-Steppe Landscapes of the Selenga Mountains

Abstract

Lipid components are an important element of organic residues entering the soil. They are often used as biomarkers to investigate the origin and evolution of organic matter in soil. The compositions of the main lipid components (fatty acids, fatty alcohols, hydroxy acids, etc.) in the soils of dry-steppe landscapes of the Selenga Mountains have been determined for the first time using the gas chromatography–mass spectrometry. The quantitative contents of lipid markers have been used to determine the total microbial count of prokaryotes. The upper humus horizons of the soils are characterized by the highest contents of lipid components (351.6–842.5 µg/g) and total microbial count (7.1–35.6 × 10⁶ cell/g) relative to lower horizons. The contents of lipid components and the number of prokaryotes are directly correlated with the organic carbon in the soil and inversely correlated with the depth. The data obtained on the distribution of markers of terrestrial and bacterial sources of organic matter are indicative of a major contribution of the underground and microbial biomass to the total microbial count, especially in the upper horizons. In addition, the relatively high carbon preference indices suggest a slow decomposition velocity of organic residues in these soils.