Floristic composition, structure and diversity distribution in Omo Biosphere Reserve, Ogun State, Nigeria

Abstract

Tree species composition and diversity were assessed in Omo Biosphere Reserve, Ogun State, Nigeria. Systematic sampling design was used to lay two straight line transects, each of 1000 m long and separated by 500m, in the reserve. Four Temporary Sample Plots (TSP) of size 50×50 m were laid along each transect at 250 m interval. Eight plots were enumerated for identification and frequency of occurrence (FO) of all woody plants with diameter at breast height (DBH) ≥10 cm. Identified tree species were categorised into different diameter classes. Data collected on DBH were used to compute Stem Volume (SV), Basal Area (BA) and Number of Trees per hectare (NT). Shannon Weiner and Simpson's indices were used to assess species diversity. Identified flora species in the reserve were from 30 families, 59 genera and 66 species. Family Ebenaceae had highest FO of 90±16.25/ha in the study area. The DBH of 146±0.72 cm³; SV of 0.47±0.86 m² /ha; BA, 86.45±0.34 m /ha; and NT, 405±1.95 were recorded. Shannon Weiner and Simpson's indices obtained were 4.01 and 0.09 respectively indicating a moderately diverse area. This study provides a baseline for the management of the forest reserve in southwestern Nigeria.

Keywords: Omo Biosphere Reserve, Species diversity, Species conservation, Tree density, Floristic composition