Cryoaridic Soils as a Genetic Type in the Russian Soil Classification System: Geography, Morphology, Diagnostics

Cryoaridic soils were proposed to be identified as an individual genetic soil type by Vladimir Volkovintser in the 1970s. Volkovintser argued that the specific properties of these soils are in good agreement with the soil-forming factors: ultracontinental climate, cryoxerophytic steppe or tundra-steppe vegetation, dry permafrost, and skeletal parent material. In cryoaridic soils, the properties of chestnut and pale soils are combined, but their individual features are due to the specific cryohumus AK horizon and secondary carbonates dominated by pendants. Cryoaridic soils were not included in the soviet soil classification system of 1977; in the Russian soil classification system, the type of cryoaridic soils with the AK–BPL–BCA–Cca horizons is included in the order of pale-metamorphic soils with the pale-metamorphic BPL horizon as diagnostic for all soil types of this order. However, our field research, analysis of publications, and the study of soil in the Central Soil Museum give us grounds to verify diagnostic criteria, to change the profile type formula of cryoaridic soils, and to review their taxonomic position in the classification system. We argue that the BPL diagnostic horizon should be replaced by the diagnostic property (pl), which means that cryoaridic soils should be transferred into another order, presumably, the order of humus carbonate-accumulative soils. Some additional subtypes are proposed. On highly skeletal shallow parent materials, cryohumus soils belonging to the order of organo-accumulative soils are developed.