ИСТИНА

Since Dokuchaev Russian plain is known as a classic model of bioclimatic zonal soil sequence. But soil geographic pattern correlates also to glacial history where earlier glaciations were more extensive than most recent one. Three conspicuous belts follow the pattern of glacial and periglacial sediments and corresponding paleocryogenic and relic soil features. The area south of Late Saalian limits is characterized by extensive loess mantles. Polygenetic features in Faeozomes and Chernozems are determined by loess stratification, marked by paleocryogenesis,paleohydromorphism and relic soil features (i.e. buried humus horizons). An area within Late Saalian limits is characterized by a diverse set of sediments (separate bodies of loess, glacial till, fluvioglacial sand, etc.) as a result of complex glacio-dynamic structure of cover glacier and high dissection of relief. The key to understanding relic soil features is the fact that day surfaces on different types of relief are heterochronous. The E/Bt horizonation of Glossisols and Luvisols on loess and glacial till is largely inherited from stratified sediments. Within Weichselian limits high flooding prevented extensive loess accumulation. Soils inherited specific layering of sediments (laminated clays, fluvioglacial sands and glacial till with veneer of fluvial sand; on higher ground till with thin veneer of cover sand, sometimes of loess; etc.). Relic features in relation to glacial history need to be further investigated. On glacial and periglacial plains they allow re-evaluating not only soil genetic models but zonal soil pattern, with bioclimatic gradient being superimposed on zonal sequence of sediments and paleocryogenic features.