Abstract: Plantation forests are being increasingly viewed as crucial for climate change mitigation due to their higher productivity and carbon storage compared to natural forests. The study assessed the Tree Growth Characteristics (TGS), Above and Below Ground Biomass (AGB; BGB), Carbon Stock (Cs) and Carbon dioxide (CO₂) emission potential of the J3 zone of the Omo forest reserve, Ogun state, Nigeria with the aim of assessing how the plantation contribute to climate change mitigation in the area. A 1000m baseline was established 20 m from the edge of the forest. Five transect lines were laid out at 200m intervals, with ten 20m x 20m plots systematically set up along these transects, and all trees with Dbh ≥ 10cm were measured for Dbh, height, basal area, and volume. TGS of Diameter at breast height (Dbh) and total height (Ht), were measured. Basal Area (BA), Volume (Vol), AGB, Cs and CO₂ equivalent emission potential were estimated using appropriate formulae. The mean Dbh, Ht, BA and Vol were 72.83 cm±1.64; 18.09 m±0.42; 0.4 m²±0.02; 9.85 m³±0.53.There was variability in the TGC with plot 8 and 9 having the highest TGC values and plot 2 having the lowest. The AGB, BGB, AGC, BGC and CO₂ equivalent emission were 3268.81 Kg/ha; 653.76 Kg/ha; 1634.41 Kg/ha; 254.996 Kg/ha and 6933.98. The study concludes that the area stores considerate amount of Carbon that can contribute to cleaning the atmosphere of CO₂. The study recommends enhancing plantation forests in Nigeria through expansion, improved practices, monitoring, and increased support to maximize their climate and economic benefits.
Key words: Aboveground biomass, Belowground biomass, Carbon stock, Gmelina arborea plantation, Tree growth characteristics