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Relationships between the delta(13)C values in modern wood of Acacia albida and the climatic parameters were investigated under semi-arid and arid sites in Senegal, between the southern tropical forest and the desert edge in the north (12 degrees 30-16 degrees 30 n). The C-13 values in the cellulose nitrate of Acacia albida show a strong south-north isotopic enrichment and reflect the gradient of aridity which characterizes the Sahelan fringe. Significant correlations were established between the delta(13)C and the basic climatic parameters, precipitation and air humidity. Elsewhere, an exceptional delta(13)C enrichment found in the innermost rings of Azadiracta indica seems to be a faithful record of the drought of the seventies. (C) Academie des sciences/Elsevier, Paris.