Features of temperature regime in svetlozems of northern taiga landscapes (European Northeast of Russia)

Parameters of winter, summer and annual temperature regime have been characterized in svetlozems of northern taiga landscapes within the ecotone "forest- tundra - northernmost taiga - northern taiga". In terms of zonal aspect, the relation between the manifestation of cryometamorphic horizon and soil winter temperature regime has been revealed.The genesis of cryometamorphic (CRM) horizon is associated with long-term period of near-zero temperatures at the depth of the formation of CRM is oberved. In svetlozems of the studied ecotone belt "forest-tundra - northern taiga" from north to south the reduction in morphological manifestation of cryometamorphic horizon is accompanied with an increase in winter temperatures. Svetlozems in forest-tundra zone are characterized by rapid seasonal freezing and colder winter temperature regime as compared to analogous upland soils of northern taiga. Soils of the forest-tundra and taiga have a similar mean annual temperature regime in the surface horizons, but the differences in the sums of Degree Days Thaw (DDT) increase down the profile. Mean annual soil temperatures of svetlozems in forest tundra are 1.5 times lower than those in northern taiga.