Potentiel floristique du sous-bois des agrosystèmes à Elaeis guineensis Jacq. en zone équatoriale (Ngwei, Cameroun)

Abstract

Floristic diversity in tropical rainforests plays a major role in assessing an ecosystem's health. In Ngwei (Cameroon), the forests are currently degraded by elaeiculture while the floristic composition in the different strata remains largely unknown. This study assesses the floristic potential of the Elaeis guineensis’s understory agrosystems. This floristic inventory is based on the 50 m x 50 m quadrats method, randomly placed in 23 palm groves aged from 0 to 40 years and 5 forests used as references. Forest ecosystems' conversion into elaeicultural agrosystems shows that the specific richness of palm groves is very variable and that a high number of species can be reached already in young plantations, thus competing with older plantations. The superiority of Simpson's diversity index (0.99) and of αFicher's indicator (79.86) in palm groves compared to forests (0.96 and 23.64 respectively) shows that the palm grove's understory is highly diversified. The forests sampled contained 1744 individuals belonging to 102 species. However, 2898 individuals belonging to 289 species were inventoried in the palm groves. The juvenile palm groves are richer in therophytes, geophytes and shamphytes, while the forests are rich in erect phanerophytes. Old palm groves are colonised by phanerophytes and several woody species threatened by extinction at different levels according to the International Union for Conservation of Nature’s (IUCN) red list. The Ngwei palm groves thus have floristic resources in their undergrowth allowing us to foresee a potential for post-cultural restoration.

Keywords

• forest
• floristic diversity
• chrono-sequence
• elaeicultural agrosystems
• biological type
• post-cultural management