Geoscience Reference
In-Depth Information
11
Podzolic Soils
We shall now examine a family of soils the most mature of which is
called 'Podzol', referring to two Russian words meaning 'below' (
pod
)
and 'ash' (
zola
) (Lundström
et al
. 2000a). Indeed the Podzol presents, just
below the surface, a bleached and depleted horizon that resembles ash.
Because of its contrasting horizons and bright colours it is one of the most
spectacular soils in Nature. But this strange beauty is not synonymous
with fertility! Its genesis has only been understood recently, and explains
the formation of other less evolved members of the same family.
Relevant reviews have been published (Souchier 1984; Pédro 1986;
Lundström
et al
. 2000b).
11.1 MORPHOLOGY AND PROPERTIES OF PODZOLIC
SOILS
11.1.1 Characteristic Climatosequences
Let us consider an example observed in France in the Pilat massif
(Loire department), on acid igneous and crystallophyllitic rocks on the
northern slope, under forest (Legros 1975). There, a climatosequence
comprises four very typical sections (Fig. 11.1):
Between 700-m and 900-m altitude
, Cambisols Dystric (WRB) dom-
inate. They do not have differentiated horizons below the surface
humus layer. A closer look tells us that the profile is uniformly
yellowish brown. The plant cover consists of a mixture of oak
species (
Quercus sessiliflora
and
Q. pubescens
) and other broad-
leaved trees.
Between 800 and 950 m
, slightly more acid yellow soils appear
under beech (
Fagus sylvatica
). The WRB has not created a special
term to name them.
