Agriculture Reference
In-Depth Information
¤A catena of ÑlossÒ: exportation of matter from the whole soil sequence (erosion processes)
¤A catena of ÑgainÒ: importation of matter for all the soils of the sequence (eolian deposits)
The
age of the differentiation
must also be taken into account. The sequences can be named
as
if they are characteristic of an active
pedogenesis. There are many chronosequences that integrate both these temporal aspects. In reality,
soil formation results from a series of pedogeneses, each of which creates conditions favorable to
the appearance of the following one. This leads to the concept of
paleo,
if inherited from an ancient process, or
current
sequential evolution
, associated
with that of
. This concept of pedogenetic chronosequence, well represented
in the evolution of soils on the loessic formations of Western Europe (Jamagne, 1978), has been
supported by other works reconstructing the historical alteration and progressive pedological dif-
ferentiation of soils on other types of materials. Its importance has been emphasized as much in
the Ýeld of pedology as in the Ýeld of pedo-geomorphology (Bornand, 1978; Vreeken, 1984; Boulet
et al., 1995).
pedogenetic phyllum
SOIL-SYSTEMS
has led us to give initial priority to the more evident
soil sequences from a spatial viewpoint. These are the toposequences where the differentiation is
linked with a functioning process. This type of Soilscape we consider
Our concern for a typology of
Soilscapes
Soil-systems.
Numerous lateral transfers affect the majority of the formations covering the slopes. In many
landscapes, the landform dictates the distribution of precipitation, by surface run-off and inÝltration.
Flow transfer varies according to the permeability of the surface layers, and leads to a differentiation
by transport of matter in solution or of particles in suspension. This differentiation which is as
much vertical as lateral, is particularly explicative of the functioning of the landscape units, and
their detailed analysis has often aided the comprehension of soil distribution on slopes and in
watersheds. The reference relief unit is therefore made up of the catchment or watershed area. The
analysis of the lateral transfers: on the surface, hypodermic, in depth, must be considered to
understand the functioning of the landscape units. This understanding and analysis is accomplished
through on-site monitoring.
The concept of ÑSoil Functioning UnitÒ (part of a slope or catchment that we can use to estimate
the transformation kinetics), with all the signiÝcance of the mechanisms and processes acting at
the interfaces of the arranged groups, particularly those of the Ñtransformation interfacesÒ between
horizons, is the basis (Boulet et al., 1994).
Numerous studies that focused on the analysis of Soil-systems showed factors of soil differen-
tiation, as well as the results of this differentiation in morphological, geochemical, and mineralogical
terms. The most recent and signiÝcant studies include the analysis of a hydromorphic plano-
sols/hydromorphic soil-system (Lamotte et al., 1992); the soil types and altitude relationships on
volcanic material, taking into account the amplitude of the toposequences under study (Alexander
et al., 1993); the mechanical and geochemical transfers within catenas (Sommer and Stahr, 1996);
upstream-downstream mineralogical evolution on a basaltic toposequence (Righi et al., 1999);
geochemical evolution in a typical Luvisols/Cambisols toposequence (Brahy et al., 2000); the
advantage of working on Ñmicro-catchment areasÒ and catenas rather than on proÝles, in the context
of the biodiversity of forest regions (Thwaites, 2000); and bringing to the fore the signiÝcance of
the length of the slope on different attributes of the soils in question (Applegarth and Dahms, 2001).
Soil-systems and Soilscapes in France
Elaboration of a typology involves possibilities of generalization, and we have to think about
ways of deÝning a structure of the approach in the whole French territory. The Ýrst global infor-
mation on the soils of the national territory comes from the pedological map of France at 1/1 M,
