Facies Features of the Structural Composition of Humic Acids in Carbonate-Free Chernozem Soils of Transbaikalia

This paper examines the facies features of non-carbonate chernozems in Transbaikalia formed on chlorite schists and characterized by different land use types (arable land, virgin land). The study aims to identify the influence of plant residue quality and soil properties on the structural parameters of humic acids. 13C-NMR spectroscopy was used to characterize the molecular composition, allowing us to determine the contribution of aromatic and aliphatic fragments to the structure of humic acids. It is shown that differences in the phytomass composition of steppe associations are reflected in the nature of the incoming organic matter. It is noted that humic acid transformations during plowing are accompanied by changes in the distribution of structural groups, indicating a restructuring of organic matter under anthropogenic load. The results clarify the understanding of the facial specificity of humus in the region’s chernozems and expand our understanding of the factors controlling organic matter stability.