Horizons in Podzolic Soils
(Lithic Haplorthods and Haplohumods)
R. J. Schaetzl
This paper (1) introduces the concept of the Beta spodic horizon, as a second (lower) horizon of sesquioxide and organic carbon accumulation (i.e., having podzolic or spodic characteristics), below an upper (Alpha) spodic horizon, and (2) examines the characteristics and possible pathways of genesis of the Beta horizon where found, in northern Michigan, USA. Here, the Beta horizon occurs in lithic extragrades of Spodosols, suggesting that its genesis is in someway linked to the physical (bedrock) barrier. Fe and Al data from the Beta point to chelation as one possible mechanism of pedogenesis in this pedon, although an additional mechanism may involve translocation of Fe to the Beta horizon as Fe ++ during wet periods and concomitant accumulation of carbon within via root decay. Under the former scenario, high amounts of free, and relatively low amounts of organically-bound Fe and Al in the Beta suggest that many of the chelate complexes have subsequently degraded into their constituent ionic and organic components. Radiocarbon dating suggests that turnover of carbon is slower in the Beta than in the Alpha, and that younger organics are preferentially accumulating in the lower parts of the horizon.