Agriculture Reference
In-Depth Information
These difÝculties have been mentioned in several contexts: the challenge of scale transfer from
pedon to landforms and up to the ÑpedosphereÒ (Arnold and Wilding, 1991), structuring of the
ecological and pedological diversity at different levels (Ibanez et al., 1995), and the necessity of
utilizing reference areas (Lagacherie and Voltz, 2000), difÝcult generalizations due to the number
of factors involved, particularly historical and polygenetic (Philips, 2001).
An attempt to validate the representativeness of the three Soil-systems presented here has been
carried out. The basis has Ýrst been a delimitation of the watershed areas of less than 100,000 ha
obtained from the DEM available for the whole French territory at 250 m intervals, associated with
the hydrologic network that constitutes the main collector of these watershed areas (IRD-ORSTOM,
1995). Next, catchment areas comprising different materials and their associated soils were selected
from the Soil Geographical Database of France (Jamagne et al., 1995), corresponding to a pre-
eminence of the Soil-systems thus described, which allowed a zonage of the areas of extension
represented in Figure 13.5.
¤Watersheds of less than 100,000 ha delimitated from France DEM at 250 meters grid size
¤
Modelling Hydrographic Network
¤
Soil-system 1: on eolian loam covering cretaceous formations (secondary chalk)
¤
Soil-system 2: on detrital formations and old sedimentary deposits
¤
Soil-system 3: on crystalline rocks and migmatite
Generally, the main axes of these systems are respected, although adaptations will be necessary
according to the particularities of the physiographic environments under consideration.
The examples presented are thus typical of three major Soilscapes of the French territory: North-
West for System 1 on loessic formations, Central depression zones for System 2 on detritic materials,
medium altitude mountain ranges of the Vosges, and the Massif Central for System 3 on granitic
alteration products. The geographical databases from which the cartographic outline presented here
is taken should enable a Ýrst generalization of the results obtained by means of the chosen approach.
CONCLUSION
This approach is based mainly on the analysis of spatial soil organizations, and thus comple-
ments the taxonomic references systematically attributed to the different soils that make up the
landscape groups concerned. This method would allow for a better understanding and clariÝcation
of the soil distribution in the landscape than would the sole allocation of a denomination to a soil
based on a classiÝcation or a referential system. We hope that it will contribute to the research of
the principal processes of soil genesis and differentiation, and that it will permit a structuring of
our knowledge in this Ýeld with the possibility of large transmission of that knowledge.
The test that we present here remains to be completed and validated. A similar typological test
based on the principal Soilscapes belonging to the most important natural regions of the French
territory is currently under way. In the future, we intend to apply this approach in zones that are
particularly representative of the wide open European spaces, territories for which the information
required for this structuring exists and is available.
ACKNOWLEDGMENTS
We would like to express our thanks to all our colleagues at the soil science research unit,
whose ideas have been synthesized in these pages, and in particular, Odile Duval, Nicolas Saby,
Sacha Desbourdes, and Alain Couturier for their help with the more technical aspects.
We also express our thanks to the scientiÝc reviewers who have greatly helped us to improve
this work.
