Asian Journal of Research in Botany

A phytosociological study of the vegetation in the bed of the Nyong was carried out at Akonolinga in order to understand not only the dynamics and floristic diversity, but also the physiognomy of the different plant groups. A system of 16 plots of varying size was set up in the various ecological habitats using the Braun-Blanquet (1932) phytosociological method. The size of each plot was 50 x 100 m², where the trees were inventoried. Within these plots, sub-plots measuring 25 x 25 m2 were set up to collect information on shrubs and herbaceous plants. The plots were 1000 m apart, for a total sampling area of 9 ha. The botanical inventories carried out yielded 342 species in 232 genus and 82 families. The most representative families are Leguminosae, Euphorbiaceae, Apocynaceae, Marantaceae, Commelinaceae and Rubiaceae. From a phytogeographical point of view, the results show a floristic background dominated by species from the Guinean-Congolese center of endemism, followed by Guinean and Afro-tropical species. Analysis of the phytosociological spectra on the spread of diaspores shows that sarcochore, ballochore and sclerochore are the most widespread species in this ecosystem. Mesophanerophytes, Microphanerophytes and Megaphanerophytes are the biological types that are most represented, ecologically heliophilic biological type which show a quasi-presence of light in the canopy and on the ground. Plant groups characterised by the Mitragynetea class of periodically flooded forests and the Phragmitetea class of riverbank vegetation are the main facies in this section. The calculated diversity indices, Shannon (6.74) high value in the periodically flooded forests and (4.39) low value on the river bank, Pielou Equitability (0.57) high value obtained on the river bank and (0.21) low value in the periodically flooded forests show a progressive floristic dynamic of regeneration of the plant cover. However, the area remains ecologically fragile and requires long-term protection.