Impact of Thermal Denudation on the Formation of Synlithogenic Soils and Development of Ecosystems in the Permafrost Zone

Abstract A significant part of the soil cover in the permafrost zone develops under the influence of cryogenic slope processes. Thermal denudation and thermal erosion leading to irreversible destruction of background soil profiles and the underlying frozen layers of soil–cryogenic complex and the development of specific synlithogenic soils (stratozems) are the processes that most crucially influence the soil morphology on relatively steep slopes and in the areas of thermocirques and thermoterraces in permafrost ecosystems. Structures, properties, and formation of these soils, as well as the areas occupied by them, are poorly studied. The soil-forming rock here is the mixed organomineral substrate recently processed by soil formation and currently entering the floor of thermocirques or thermoterraces via slumping and further lateral redistribution. The basic scheme of the formation and development of thermodenudation–accumulative stratozems is suggested on the basis of the field data in northeastern Yakutia and central Yamal Peninsula and comprises four main stages. Characteristic of each stage is a certain combination of the properties of soil-forming substrate and the composition of plant communities. The stages can either sequentially follow one another or cyclically repeat with the reactivation of thermodenudation processes. The specific features in the formation, accumulation, and transformation of soil-forming material suggest a new subtype of thermodenudation–accumulative stratozem to be distinguished in the further version of the Russian soil classification. The studied ecosystems of thermocirques and thermoterraces are of considerable interest for further research as biodiversity foci, areas of potential new formation of permafrost, paleoarchives, and possible carbon sequesters.