Floristic composition, structure and diversity of riparian forests in southwestern Nigeria: Conservation is inevitable

The Nigerian riparian forest ecosystems had declined in extent and
distribution and this had been attributed mainly to land use change. This
study intended to provide an understanding of the links between plant
diversity, composition, structures, and disturbances both anthropogenic
and natural processes inducing the vegetation dynamics. Nine study sites
were used for this study, within each site, five (5) plots (0.25 ha in
size) were marked out and placed systematically at an interval of 10 m
along the transect. A complete enumeration of plant species was carried
out and identified at the species level. Diversity indices and structural
parameters were determined and anthropogenic activities were ranked. A
total number of 233 plant species were identified, belonging to 80
families; out of which, Euphorbiaceae and Apocynaceae were dominant
families The density and basal area ranged from 2,200-6,000 ha-1 and
2.59-17.58 m2 ha-1 respectively across the study sites. Pterocarpus
santalinoides, Alchornea cordiflora, Chassalia kolly, Tetracera spp,
Fimbristylis, Bambusa vulgaris and Cyrtosperma senegalense were the
dominant species. The Shannon diversity index ranged from (1.38-3.49),
Simpson (0.66-0.97), and Evenness diversity (0.43-0.84). Fisher alpha
(10.03-30.21) and Whittaker beta diversity (0.36-0.89) values were highest
in Ipetumodu (site VIII) and lowest in Ilesha (site II). Seventy-three
(73%) of the species in this study had a low important value index (IVI).
The dominance of some lianas and herbaceous species in the riparian forest
sites showed disturbances, stages of ecological succession, and
regeneration of the vegetation. Conservation is inevitable towards
maintaining and protecting species diversity, ecosystem roles, and
services of these forests in Nigeria.