[en] The contacts between forest and savanna and between the Sudanian and Guinean savannas are influenced by climate as well as by the action of man. This incorporates the selection or destruction of and the longlasting human pressure on vegetation during the colonial history. The pyromorphic savannas of the Ivory Coast show the initial stages of deforestation and include savannas in the forest of Adjoukrou or the radical deforestation of the Baoulé savannas. Floristical associations and the savanna dynamics reflect the selection and different uses by man: ubiquitous savannas as well as those of the herders, the shifting cultivators, the blacksmiths, the gatherers or even for fuel. The Sahelian savannas are mostly the result of ancient and present agrarian systems, especially for the gum production in the North. The Saharan savannas and the desert vegetation were heavily degraded during the last drought periods, but still they remain within their boundaries. In the past they could normally regenerate when the human population left the regions. Probably the desert-savanna boundary is the only climatic boundary in these zones and it demonstrates its stability at least over the past centuries.The soil covers reflect the major pedoclimatic tendencies: sodic and lithic soils of the deserts and fersiallitic or ferrallitic soils of forests and savannas. Iron rich, allitic or bauxitic soils often represent only eroded weathering layers, truncated or cemented profiles. In detail, the soils reflect the mosaic of the utilization by man. Only the contact between the soils of the desert and the savanna has a climatic significance. Desert soils are characterized in micromorphology by a dissociation of plasma and skeleton, a mobilization of sodium and a fixation of calcium. The two belts of gravel iron crusts which are typical for the soil cover of tropical West-Africa represent the two pioneer frontiers of man, in the north by a stretching of the Sahelian savannas into the Sudanian savannas and in the south by the encroachment of the Guinean savannas into the forests. There is also a large variety of typical anthropogenic soils due to bush fire, wood cutting or overgrazing. Some isohumic horizons of grey and black soils are rich in phytholithes and melanised organic matter. Trampled zones of caravan tracks or pasture are specific of heavy packing, vertic or duriconcentrated soils. Other layers of burnt soils are compacted, concentrated, sealed and oversaturated with satuconcentration of iron oxic-rich silts. Removed horizons of cultivated anthropic soils are characterized by superficial pellicular organisation. Iron abruconcentration often reflect the complex history of cultivation systems such as hummocks or ridged and linear hillocks. In a situation where it is still difficult to define reliable climatic indicators, cartography is one of the rare instruments for the evaluation of the savannas and for the definition of transfer functions on a continental scale.

[fr] Les contacts des forêts et des savanes sont en relation avec des refuges climatiques mais surtout avec des actions anthropogènes. Les savanes pyromorphes de Côte d'Ivoire révèlent le mode initial de défrichement. Les associations floristiques comme la dynamique reflèteraient des sélections anthropiques et des modes utilitaires. Les savanes de la ceinture sahélienne résultent de systèmes agraires spécialement liés à la production de gomme arabique. Les savanes sahariennes comme la végétation du désert ont été intensément dégradées durant les deux dernières périodes de sécheresse. Auparavant, la végétation pouvait se régénérer du fait de l'émigration de la population. Les limites du désert et de la savane paraissent être la seule frontière végétale à signification climatique dans ces zones qui montrent une stabilité à l'échelle séculaire. Les couvertures pédologiques intègrent les grandes tendances du pédoclimat, mais dans le détail les sols indiquent une mosaïque d'utilisations anthropogènes. Les deux bandes de cuirassement gravillonnaire représentent deux fronts pionniers anthropogènes. On distingue des sols anthropisés influencés par les feux de brousse, les défrichements, les surpâturages et des sols cultivés qui ont enregistré l'histoire des systèmes culturaux. Bien qu'il soit difficile de définir des indicateurs climatiques fiables, la cartographie demeure un moyen d'évaluation des savanes et de définition des fonctions de transfert, à l'échelle du continent.