Soils of Karst Sinkholes of the Polar Urals: Morphology, Genesis, Classification

A study of a series of slope conjugations of karst sinkhole soils in the Subarctic zone of the eastern macroslope of the Polar Urals (67°13' N) and their comparison with the background soil was conducted. Based on macro- and micromorphological diagnostics, analysis of chemical properties and the nature of the vegetation cover, the genesis and classification position of poorly studied soils of the altitudinal belt of mountain tundra (230 m above sea level) were clarified for the first time. The parent rocks are represented by loose boulder-free coarse-silty heavy loams overlying karst rocks (marbled limestones). In the inter-funnel surface and on the slopes of the funnels, illuvial-iron svetlozems (Skeletic Albie Podzol (Neocambic) are formed, which are replaced by soddy-cryometamorphic soils (Calcaric Skeletic Cambisol (Loamic) in the bottom of the funnels. The main differences in the surface horizons are associated with the composition of organic matter – different ratios of weakly decomposed, carbonized tissues and small, highly decomposed plant residues with traces of their biogenic processing and cryometamorphic fragmentation. For the middle and lower parts of the profile of all the soils under consideration, a common macro- and micromorphological feature is the presence of a specific structural organization in the form of fine-plated, lenticular-layered and angular-granular, angular-rounded and rounded microaggregates. It is shown that under conditions of long-term seasonal freezing, along with the aggregation of finely dispersed mass and fragmentation of plant residues, the destruction of iron-containing minerals occurs with the release of amorphous iron compounds with the formation of nodules and ferruginous plant residues.