Aigbe, H.I.1, Nchor, A.A. and Obasogie, F.O.

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In this study, the variability of structure and floristic composition of Ehor Forest Reserve (which consist of areas BC (Benin Council) 12/1, 15/1 and 16/1) was investigated. Systemic line transect was employed for laying of sample plots for data collection. The 20m x 20m (0.04 ha) sample plots were laid in alternate directions along two transects at 250m interval and thus summing up to 4 sample plots per transect and a total of 8 sample plots per BC area. A total of 541 trees were measured in 24 sample plots from the three BC areas. Tree identification and detailed growing stock measurements of diameter at breast height (Dbh) and total height were made on all trees with Dbh ≥ 5 cm within the sample plots. Individual tree basal area was computed and extrapolated to per-hectare basis. The biodiversity indices computed were species relative density, species relative dominance, Importance Value Index (IVI) and Family Importance Index (FIV). The results show that an average number of trees per hectare were 206 (30 species), 809 (49 species) and 675 (44 species) encountered in areas BC 12/1, 15/1 and 16/1 respectively. The mean basal area/ha estimated was highest in the BC 16/1 (28.24 m2) followed by BC 15/1 (26.66 m2) and lowest in BC 12/1 (1.82m2). In BC 12/1, Ceiba pentandra had the highest IVI of 12.62 %. Brachystegia kennedyi had the highest IVI of 7.83 % in BC 15/1 while Trichilia welwitschii had the highest species share of area BC 16/1 with an IVI of 8.904 %. The forest had two vertical structure layers in 12/1, three vertical structure layers in 15/1 and two vertical structure layers in 16/1. The findings of this study revealed that the three BC areas of Ehor Forest Reserve had more trees in the lower Dbh class than in upper Dbh class, however, only area BC 15/1 and 16/1 is well-stocked. Key words: Forest structure, tropical forest, floristic composition, Ehor forest reserve, importance value index