Geoscience Reference
In-Depth Information
CONCLUSION
Thanks to the studies of M. Bornand, and by underscoring the evolution
of the coarse fractions, the Luvisols Rhodic of the Rhône valley have
enabled us to develop our concepts of pedogenesis still better.
In these soils, in the B horizons, the carbonates dissolve in place.
Igneous rocks are weathered
in situ
to form clays that rubefy. Siliceous
fragments resist weathering. On the surface of the soil, more precisely
in the A and E horizons, degradation is manifested at the same time
by acidification, disappearance of red colour, transformation of smectite
to kaolinite (desilication) and finally by loss of iron accompanied by
partial solubilization of the clay minerals. This results in a high contrast
between A and B.
Besides the evolution of iron, there is thus a great similarity to what
happens in Luvisols and Planosols discussed earlier.
The Mediterranean red soils have permitted the Roman civilization
to develop around the
Mare nostrum
, this with relative food security.
But poor land management has led to disappearance of the forests and
planing down of the soils. Of course, soil productivity is not the first
worry of developed civilizations in our times. But up to what level of
world population?
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