ASSESSMENT OF PLOT SIZE EFFECT ON STEM BIOMASS AND CARBON STOCK AT THE AKURE STRICT NATURE RESERVE, ONDO STATE, NIGERIA

Accurate estimation of forest biomass and carbon stock depends largely on appropriate sampling strategies, including plot size selection. This study evaluated the influence of sampling plot size on biomass and carbon stock estimates within the Strict Nature Reserve of the Akure Forest Reserve, Ondo State, Nigeria. Eight 50 m x 50 m plots were established, each containing three nested subplots of 20 m x 20 m, 25 m x 25 m, and 35 m x 35 m. Tree diameters at breast height, base, middle, and top were measured and used to compute basal area and volume. Biomass was estimated by multiplying tree volume by species specific wood density from published sources, and carbon stock was derived using a conversion factor of 0.5. Analysis of Variance (ANOVA) was conducted to test for differences in biomass and carbon estimates among the plot sizes. Results showed no significant effect of plot size on biomass and carbon stock estimation (P> 0.05). The 25 m x 25 m subplot recorded the highest biomass (900,289.05 kg/ha) and carbon stock (450.14 t/ha), followed by the 35 m x 35 m, 20 m x 20 m, and 50 m x 50 m plots. Despite these differences in magnitude, estimates were statistically similar across all plot sizes. Findings suggest that any of the four plot sizes can provide reliable biomass and carbon assessments. Considering the labour-intensive nature of field measurements, the 20 m x 20 m plot is recommended as the most efficient option without compromising accuracy