ИСТИНА

Cryogenic and vertic processes are associated with soils formed in strongly different environment. Vertic process occur in hot or warm environment with alternating wet and dry seasons, and is mostly expressed in Vertisols of (sub)tropical to temperate climates. Cryogenic process takes place in cold environment of tundra and northern taiga in Cryosols (WRB) or Gelisols (ST) which have cryic horizon. Meanwhile Cryosols and Vertisols according to WRB occur in the same Reference soil Group named soils with limitations to root growth due to permafrost (Cryosols), and due to alternating wet-dry conditions and shrink-swell clays (Vertisols). Despite the antipodal climatic conditions, Cryosols and Vertisols have common macro and micro morphological features resulting from similarities in physical behavior such as volume changes throughout the year. As far as Vertisols and vertic soils ultra-continental cryogenic environment with permafrost (Kovda et al., 2013, 2017) it might be a challenge to differentiate the cryogenic or vertic genesis of similar features in these soils. It is also the question what is the result of their combination and interaction? The similar problem may arise in areas of paleocryogenic areas where cryogenic processes are or have been active (ex. periglacial steppe zone, high mountains), and may lead to the confusion, such as “patterned ground on the equator” in Soil Atlas of the Northern Circumpolar Region (EU, 2010). This is why the aim of this research is to summarize the common morphological features resulting from vertic and cryogenic processes. At the scale of soil cover freeze/thaw cycles in Cryosols and wet/dry cycles in Vertisols result in the formation of microrelief and complex soil cover. At a scale of soil profile freeze/thaw and wet/dry cycles result in heaving (swelling), turbations and involutions, fragmentation of soil horizons, sorting of coarse materials, weathering, structuring of fine earth, compaction of soil mass, cracking. Permafrost in Cryosols and compact subsoil horizon in Vertisols leads to the formation of reductaquic or reductigleYic properties. There are several common features at microscale formed as a result of actions on structure development, consolidation, deformation and particle translocation. Angular blocky frost-induced microstructure with inter-aggregate star-shaped vughs typical for clayey silty Cryosol is similar to angular blocky microstructure of typical Vertisol. Other examples of similar processes and microscopic features in Cryosols and Vertisols are: frost mulching and self-mulching resulting in the formation of fine angular blocky and granular peds; stress features and the formation of striated b-fabrics; shattering features formed by frost action or by swelling; desiccation and the formation of planar voids; banded distribution of coarse grains and nodules. Frost-induced microstructures are very resistant and if occur in paleosols and in soils from warmer regions are used for the reconstruction of past climatic conditions (Vliet-Lanoë, 2010). The same is true for vertic features. So it might be a challenge to differentiate cryogenic and vertic features in (paleo)soils subjected to both processes in succession or simultaneously. This study was supported by the Russian Science Foundation, project no. 14-27-00133.