Composition of humus in cryosolic chernozems on the territory of the southern border of Transbaikal cryolithozone

The soils of cryolithozone of Transbaikalia are characterized by sharp daily and seasonal temperature fluctuations, which affect the composition of soil organic matter. We have studied the organic content of cryosolic chernozems of Eravna forest-steppe basin in the south of Vitim Plateau, which are formed under extreme climatic conditions that determine the specifics of the quantitative and qualitative composition of humus. The characteristic feature of humus of cryosolic chernozems is an increased carbon content in the humus horizon and its sharp decrease with depth. The composition of humus is fulvate-humate in organic horizons, the proportion of fulvic acids increases down the profile, and humus acquires humate-fulvate character. Short period of biological activity and a weakened intensity of biochemical processes result in reducing the rates of mineralization and humification, so humin accumulates in large quantities in these soils.