Geoscience Reference
In-Depth Information
Chestnut trees
Luvisol Rhodic
'
Terre de Groie
(Leptosol)
'
A
A
B
R
A
R
E
B
Truncated
Luvisol
R
Colluvia at the
footslope
Bajocian limestones
Fig. 9.11
Retrograde evolution through slow erosion of 'chestnut-growing soils' in the
Charente region (Callot 1972).
Figure 9.12 illustrates the penultimate stage of this retrograde
evolution, which could still continue up to the stripping of the entire
soil down to the parent material.
Fig. 9.12
Red soil of the A/R type with calcareous slabs on calcareous sandstone of the
Bonifacio plateau, Corsica;
photo
:
author.
On the contrary, weathering, which causes deepening of the soil, is
extremely slow. M. Bornand estimates this deepening to be about 50 m
of thickness for a million years in the soft materials he studied. This
only represents an annual decomposition of 0.5 m
3
of rock, giving at
best 100 kg of soil per ha per year after decarbonatation. On the human
scale, the soil is a non-renewable resource!
Rational use of the soil must have as first objective the limiting of
erosion (incorporation of organic matter, contour ploughing…). We do
not have space to go into these topics in detail.
