Diversity of densd dry forests in Togo (West africa)

This work is a first overview on the dry forests of Togo. It is based on the analysis of 90 floristic plots achieved in forest fragments in three protected areas of Togo. In all, 265 species were recorded, belonging to 62 families. The best represented families were the Leguminosae (24 genera, 36 species), Rubiaceae (16 genera, 23 species) and Moraceae (4 genera, 13 species). Most species present forest affinity despite that these forests are enclosed within the soudano-guinean savannas: 51% of humid forest species, 40% of sub-guinean species, 7% of typical savanna species, 2% of introduced species and 1% of endemic species of the Dahomey Gap. A factorial correspondence analysis (AFC) permitted to individualize these forest fragments, showing that they are not floristically homogeneous. Of the 265 species, 47 (17,7%) belong solely to Abdoulaye forest, 23 (8,7%) to Dantcho forest, 26 (9,8%) to Tchorogo forest and 169 (63,8%) are in common to the three forests. Characteristic, i.e. site-addicted, species are responsible of the discrimination demonstrated by the AFC while shared species, more numerous, constitute the basic elements which permit to gather the studied forest islands into the same physionomic type. alpha-diversity indices were calculated on the samples in each protected area; it appeared that Shannon and equitability indices are identical and that shared species are better distributed than characteristic ones which are relatively rare. A beta square diversity analysis showed that in these dry forests specific richness, Shannon and equitability indices are distinctly lower than in semi-deciduous forests of neighbouring areas. Analysis of species co-occurrences within the dry forest permitted to identify a major Anogeissus leiocarpus dominated plant community, very well represented in the three protected areas. These features permit to bring together the dry forests of Togo and those of other West African countries (Benin, Ivory Coast and Ghana).