Ten temporary plots were laid within Triplochiton scleroxylon woodland in Gambari Forest Reserve, one of the major rainforests in Nigeria (Latitude 7025IN and 7055I and Longitude 3053Iand 309IE) of attempts to assess tree species and their effects on surrounding soil in Triplochiton scleroxylon woodland. The tree species diversity was assessed using the sample plots laid in systematic line transects. In each sample plot, all trees with a diameter at breath height (DBH) above 10cm were identified by species and measured. The species diversity within 5 meter range of T. scleroxylon was shown to be high using Simpson diversity Index, 0.93 with low Dominance of 0.07 and Evenness of 0.85 indicating relative moderate range. The results showed that high diversity of tree species was enumerated in the study area with Triplochiton scleroxylon 36.00% followed by Funtumia elastica with 8.00%. Considering T. scleroxylon species, Plot 10 recorded the highest values for Basal Area and Volume, 3.386m2 and 468.961m3 respectively followed by Plot 2 with BA (2.759m2) and Volume (293.006m3) with lowest BA of 0.656m2 for Plot 8, and least Volume of 24.22m3 recorded against Plot 7. Plots 6 and 9 had no presence of T. scleroxylon with Plot 6 having 2.71% Organic Carbon greater than Plot 3 with highest frequency of T. scleroxylon of 2.52%. Sample 2 has the pH of 7.40 which is alkaline in nature as it can lead to the factor of high volume of Triplochiton scleroxylon, soil particles in the study area revealed that sand, silt and clay were in moderate for the growth of Triplochiton scleroxylon. The Nitrogen (%), Phosphorus (mg/kg) and Potassium (mg/kg) (NPK) were well utilized in interaction form by the high presence of T. scleroxylon (Plot 3), 0.21, 3.60 and 0.51 respectively while despite the presence of other tree species beside T. scleroxylon in Plot 2, NPK were not interactively utilized as in Plot 3 with the values of 0.3%, 4.94mg/kg and 0.65mg/kg respectively.
Keywords: : basal area, DBH, autecology, height, simpson rule, volume
