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To summarize, we have, in sequence, 0, 1, 2 and, lastly, 3 characteristic
horizons (Fig. 11.2).
Increasing differentiation
E
Bh
Bh
Bs
Bs
Bs
Cambisol Dystric
Yellowish soil
Entic Podzol
Podzol
Fig. 11.2 Characteristic horizons of different soils of the Pilat massif. Bs: yellowish-brown
horizon obviously enriched with iron; Bh: dark horizon enriched with organic matter; E:
bleached and depleted horizon.
If sufficiently long time is given or if the climate at the base of
the slope becomes more humid, there could take place in this area
the evolution shown by the arrow in Fig. 11.2. In other words, this
climatosequence enables us to postulate the existence of an evolution
over time, which can lead to the same pedological types. This is primary
podzolization , meaning the direct, though gradual, evolution from a poorly
differentiated soil to a Podzol. Sometimes, after introduction of coniferous
trees, in a few decades, we see formation of an E horizon one-cm thick
under the humus of the initially uniform profiles ( micro-podzolization ).
But podzolization can be secondary and take place at the surface of
a soil already depleted by pedogenesis. This is the case of Podzols of
Amazonia, which develop on the surface of Ferralsols (Chap. 5). In the
middle latitudes, the upper part of Luvisols can also transform to a
Podzol (Chap. 8).
11.1.2
Physical and Chemical Features of Podzols
Typical Podzols have in common:
General features
￿ overall sandy texture, at least in the case of primary podzolization;
on the other hand, the IIB horizons are often clayey in secondary
podzolization (e.g. in Amazonia);
￿ a humus of mor type, thick, acid, with high C/N ratio in the
humid mountains and coniferous forests, but less typical humus
(mull) in tropical forests and savannas;
￿ low biological activity, especially absence of earthworms and
burrowing animals; otherwise the numerous horizons of Podzols
would disappear through mixing;
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