Spodic Horizon - Soil Geography of the USA: A Diagnostic-Horizon Approach - page 256

Antarctica, Beyer and B¨ lter ( 2000 ) reported soils with spodic-like horizons in
abandoned penguin rookeries. In northern MI the spodic horizon is more strongly
developed on N- and NE-facing slopes than on other aspects (Hunckler and
Schaetzl 1997 ). In FL the Bh horizon forms where there is a fluctuating water
table (Kristiansen et al. 2010 ; Harris and Rischar 2012 ).
Although soils with a spodic horizon are commonly envisaged as being predom-
inant in sandy soil materials, the present study suggests that nearly half of the soils
with a spodic horizon form on loamy materials. High amounts of gravel apparently
disfavor spodic horizon formation (Schaetzl 1991 ). The spodic horizon requires
150 to over 6,000 yr to form (Table 22.3 ).
22.6 Genesis of the Spodic Horizon
Podzolization is a complex collection of processes that includes eluviation of base
cations, weathering transformation of Fe and Al compounds, mobilization of Fe and
Al in surface horizons, and transport of these compounds to the spodic (Bs) horizon
as Fe and Al complexes with fulvic acids and other complex polyaromatic com-
pounds (Ugolini and Dahlgren 1991 ; Ugolini et al. 1988 ; Gustafsson et al. 1995 ).
Weaker degrees of podzolization occur in spodic subgroups of Entisols and
Andisols. Podzolization is distinguished from ferrallitization in that Fe and Al
complexed with organic acids are transported in the solum, whereas with ferralli-
tization, the Fe and Al are residual and are accompanied by strong desilication.
22.7 Summary
The spodic horizon/materials are acidic and contain abundant illuvial SOC, Al, and
Fe and for this reason have strong colors. In ST, soils in the Spodosol order or in
spodic subgroups of other orders represent five orders, ten suborders, 24 great
groups, 85 subgroups, and 696 soil series. Soils with a spodic horizon generally
occur in environments with abundant precipitation and cool temperatures as in the
Pacific Northwest, the upper Great Lakes region, and northern New England and
NY. More than 75 % of soils with a spodic horizon have a cryic or frigid soil-
temperature regime. Although soils with a spodic horizon are commonly envisaged
as being predominant in sandy soil materials, the present study suggest that nearly
half of the soils with a spodic horizon form on loamy materials. The dominant
process in soils with a spodic horizon is podzolization, which is a complex
collection of processes that includes eluviation of base cations, weathering trans-
formation of Fe and Al compounds, mobilization of Fe and Al in surface horizons,
and transport of these compounds to the spodic (Bs) horizon as Fe and Al com-
plexes with fulvic acids and other complex polyaromatic compounds.