The impact of land conversion on plant biodiversity in the forest zone of Cameroon

Floristic surveys were carried out in different land use systems (primary and secondary forest, fallows of different ages, cocoa plantations, crop fields) within the forest zone of Cameroon, to assess the impact of land conversion on above-ground plant biodiversity. Beside various diversity studies, plant density was measured and diameter at breast height was estimated. The results showed that the forest areas, which represent the historic biodiversity of the region, preserve the greatest number of species (160 species in primary forest and 171 in secondary forest). Our results indicate the relatively great importance of secondary forests as refuge areas for primary forest plant species that may function as a starting point for possible regeneration of original biodiversity. Species richness is reduced progressively from the original forest (160 spp.) and secondary forests (171 spp.), to Chromolaena odorata (Asteraceae) fallow fields (149 spp.), to an old fallow field (139 spp.), to a cocoa plantation (116 spp.) and to the farmland (64 spp.), where only weeds and crops contribute essentially to plant biodiversity. Also the number of species that are used for non-timber products (construction, food and medicines) decreased with increased land conversion.