Geoscience Reference
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The model that we propose has various limitations:
Weaknesses of the model
￿ Authors who measured the 14 C in Podzols found age of the
organic matter increasing from the top to the bottom (Schwartz
et al . 1985; Eusterhues et al . 2005; Rumpel 2006). In particular, the
Bs is, on the whole, older than the Bh that appears to us to be
the degradation product of the former. This fact does not agree
with the sense of our demonstration! But Figure 11.10 shows that
part of the carbon extracted from the Bh by degradation of the
complexes is recycled in the formation of the Bs…
￿ The model does not know how to predict if the accumulations in
the B are relative or absolute. As regards silicon and aluminium,
the isotitanium, isozirconium and isovolumetric arguments show
that their concentration in the B is only relative (Legros 1982;
Dalla-Piazza 1996; Egli et al . 2003b). On the other hand, iron
exhibits a more capricious behaviour. At the footslope we some-
times observe absolute accumulations in the form of spectacular
ironstones.
￿ The mechanism explained does not solve all the questions
because the case of Podzols in water-saturated environment
remains. In them, the iron, almost absent, does not play any
role in insolubilization, while preservation of carbon compounds
is ensured by lack of oxygen (Schwartz 1988b).
11.4
TYPOLOGY AND CLASSIFICATION
11.4.1 Alpine Nanopodzols
In the alpine belt (at the upper limit of forests), Podzols exist under the
conditions defined earlier (humid climate, highly acid parent material,
moor or ericaceous undergrowth). Their horizons are very distinct,
although the E is more grey than white, because of the abundance of
organic matter. They are very shallow (Fig. 11.11). The C sometimes
appears at less than 30 cm, so that the horizons are reduced to narrow,
brightly coloured bands. These are dwarf Podzols, the Nanopodzols of
Swiss authors. The Americans make them Entic Haplocryods: typical
(Hapl) Spodosol but with poorly developed B (Entic) and of cold climate
(Cryic). For the WRB they are Leptic Podzols (shallow Podzols). The
qualifier Entic also exists in the latter system but indicates absence of
the E horizon.
Morphology
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