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abstract 552

STRATEGY OF MORPHOPEDOLOGIC UNITIES USE FACE TO CLIMATIC CHANGE ON SOUDAN SAHELIAN ZONE.

Author(s): S. Valet, Ph. Le Coustumer, M. Motélica -Heino, P.S. Sarr
1Consultant. PASSERELLES, 9, rue du Bât d’Argent, 69001, Lyon France ; valet.serge2@wanadoo.fr ; 2 Université de BordeauxI, av. France.; 3 Unité : UMR6113 Institut des Sciences de la Terre d'Orléans (ISTO), France ; stefan.motelica-heino@univ- orleans.fr.;

Keyword(s): run-on, simulated hydrological budget, simulated yield, millet, morphopedologic units, Sudano- Sahelian zone.

Article:

Poster:

Session: OS5e Multiple and multisector uses

AbstractIn Sudan-Sahelian zone, the yield and quality of cultures are essential to the human well-being

and the stability of societies. Climatic change, rain losses and the accentuation of its spatio-temporal variability

generate an increase of the hydrological stress on traditional food crops. At the hillslope and the field scale, the

accumulation of water by the crops is modified by the run-off. A part of this run-off, even during a year of high

hydrological deficit, forms the runon of the same importance on the field than on the hillslope. This runon is defined as

“a natural, complementary and simultaneous irrigation to the rainfall that has generated it in according to natural

(topographical, morphological, permeability) anthropogenic (soil work) conditions”. It can explain the yield variability

that does not correspond to the potential fertility of the different morphopedological units.
Cultivated areas are

only partially represented in global models. Now the elaboration of new patrimonial management modes of the

Soudano-Sahelian zone must rely on the analysis of the spatio-temporal dimension of the climatic factors. They

regulate the land and environmental dynamics and this suggest that their co-evolution must be integrated in an

evolutionary and flexible scheme of such as the cultivators use empirically.
The study investigated the hydrological

balance of the mil for 90 days duration, cultivated traditionally, including the impact of climatic change (three

contrasted rain years, one normal, one year showing a deficit and one very rainy) and the variability of the

morphopedological units on the slope. The runon was taken as a complementary irrigation. On the slope, the actual

evaporo-transpiration (AET) expected varies from 126 to 289 mm during a year showing a rain deficit, from 275 to

314 mm during a normal year and from 296 to 351 mm during a very rainy year. To these commotions in real water

simulated correspond to extreme yields of 0 to 1083 kg.ha-1, of 1128 to 1599 kg.ha-1 and from 1382 to 2047

kg.ha-1 for the three years respectively.
Results demonstrate that face to the climatic change, the integration of the

multi-scale variability of the productivity of the media and of the spatial distribution of hydrological resources to

adapt to environmental fluctuations allows to foreseen this change and attenuate its violence. The mastery and control

of the hydrological fluxes on the slope and on the field to eradicate the erosion could be realised through bocage

planning.

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STRATEGY OF MORPHOPEDOLOGIC UNITIES USE FACE TO CLIMATIC CHANGE ON SOUDAN SAHELIAN ZONE.