Tree Species Diversity and Structure of Eda Forest Reserve, Ekiti State, Nigeria

Abstract

Tropical rainforest is continuously threatened by timber exploitation and conversion to other land uses. In this study, tree species diversity and forest structure of Eda Forest Reserve in Ekiti State, Nigeria, were assessed using systematic line transect and purposive sampling techniques for plot demarcation and data collection. Two transects (2000m long) were laid in secondary forest and encroached farmland in the reserve, while the primary forest fragments were sampled purposively. Twenty sample plots (20m×20m) were laid out on each of the vegetation types. All trees >10cm diameter at breast height (dbh) were identified to species level and enumerated for total height and dbh. Data were analyzed using descriptive statistics such as tables, charts, frequency, percentages and diversity index analysis using paleontological statistics software (PAST 2.14). There were 60 species from 22 families, with Sterculiaceae, Caesalpiniaceae and Moraceae being the most abundant families. Individual tree populations were 380 trees/ha, 280 trees/ha and 137 trees/ha in the primary forest, secondary forest and encroached farmland, respectively. Species composition comprised 39, 38 and 19 species in primary forest, secondary forest and encroached farmland, respectively. Khaya ivorensis had the highest relative density in the three vegetation types (19.74%, 24.53% and 27.74%) respectively, while Ceiba pentandra had the highest height (53.87m). The mean basal area ranged from 0.36m2/ha (encroach farmland) to 3.18m2/ha (primary forest). Shannon-Wiener Indices were 3.22, 3.14 and 2.51 for the primary forest, secondary forest and encroached farmland, respectively. Eda forest reserve is a heterogeneous ecosystem that had variations in tree population due to anthropogenic activities. The secondary forest and encroached farmland have great potential for recovery if conservation efforts are put in place.