Soils with the Second Humus Horizon, Paleochernozems, and the History of Pedogenesis at the Border between Forest and Steppe Areas

The genesis of soils with the second humus horizon (SHH)—the most striking relict feature in profiles soddy-podzolic (Retisols) and gray (forest) (Luvisols)—is discussed. Middle Holocene radiocarbon age SHH, its dark color, discrepancy properties modern horizons forest have specified main issues study SHH: character climate changes shifts boundaries natural zones reflection these evolution soil profiles. We consider history studies, systematization, geographic distribution, SHH. On basis analysis paleosols, we try to characterize prototype estimate age, trace stages development Holocene. also tried find analogous SHH outside Russia. According accepted hypothesis, SHHs are residual paleoclimatogenic formations. Other hypotheses them as buried horizons, a result paleohydromorphism, etc. Dark humic substances were formed first half characterized by extremely high stability. This allows survive aggressive environment eluvial Retisols Luvisols. Under influence biochemical mechanical (tree uprooting) factors, strongly transformed, which complicates their study. At same time, well-preserved Chernozems dark-colored Phaeozems under kurgans other earthy structures sediments make it possible establish degradation late Within East European Plain, thickness vary agreement hypothesis this horizon. validity nature hydrogenic origin is present, interest Russia has somewhat weakened. In Central Europe North America, not been studied, but research into problem chernozems being actively pursued. our opinion, combination two types objects and, accordingly, directions can lead more definite conclusions about