Comparative assessment of floristic composition and diversity following anthropogenic disturbance in Nigerian lowland rainforest

Nigerian lowland rainforest, a biodiverse ecoregion with widespread vegetation, has experienced selective anthropogenic disturbances. Understanding the current species composition and forest recovery following a decrease in disturbances is critical for forest biodiversity and conservation. This study assessed the species composition and diversity of a once disturbed forest site in comparison with two (2) neighboring undisturbed forest sites within Nigerian lowland rainforest along Warri River. We used sixty quadrats measuring 20 m * 20 m (400 m 2 ) for trees and shrubs and 2 m * 2 m (4 m 2 ) for forbs, grasses, and sedges. We used Hill numbers and rarefaction to assess species richness and evenness, and cluster analysis to assess dissimilarity between sites. Results showed 144 species belonging to 123 genera and 50 families spread across diverse growth forms (trees, shrubs, forbs, grasses, sedges, lianas, and ferns). Across the forest sites, the most diverse families were Fabaceae (17), Poaceae (14), Asteraceae (11), Euphorbiaceae (10), and Cyperaceae (9), while the least diverse families, with one species each, were Vitaceae, Urticaceae, Clusiaceae, Apocynaceae, Musaceae, and Caricaceae. Hill number diversity metrics showed high species richness (abundance of forbs and grasses) for the disturbed forest site and high species evenness for the undisturbed forest sites. The undisturbed forest sites had fewer forbs and grasses, more trees and shrubs, and were more similar in species composition than the disturbed forest site. Our findings suggest that anthropogenic disturbance may have changed the species composition of the disturbed forest site: more forbs and grasses and fewer trees. This further suggests that the disturbed forest is gradually recovering and underscores the imperative conservation of the Nigerian rainforests.