Suprapermafrost organic-accumulative horizons in the tundra cryozems of northern Yakutia

Abstract

Organic-accumulative horizons above the permafrost table have been described in the profiles of cryozems developing on interfluve surfaces in the tundra zone of northern Yakutia. The organic matter content in these suprapermafrost horizons is comparable with or even exceeds the organic matter content in the surface horizons. The dynamics of seasonal thawing specify the annual involvement of the material of these horizons into the zone of active pedogenesis or its exclusion from it in the case of their frozen state. The analysis of the morphology of cryozems of the Kolyma Lowland along a 1000-km-long sublatitudinal transect shows that the accumulation and migration of raw organic materials (predominantly, differently decomposed peat) above the permafrost table take place upon the particular combinations of local factors (the soil moistening, ice content, freezing-thawing conditions, nanotopography of the permafrost table, etc.) at the lower boundary of the active layer. The well-pronounced accumulation of the raw organic material in the suprapermafrost horizons can be reflected in the substantive characteristics of these horizons and should be taken into account in classification decisions.