The present study was conducted in monospecific stand of Cork oak (Quercus suber L.) in the Oulmes Central Plateau (Case of Zitchouene Forest), with the following objectives: the determination of the organic carbon stock in the different compartments of the forest ecosystem, namely: the soil, the above-ground and below-ground biomass. To achieve these objectives, we studied the biomass of the cork oak tree in the study area, using direct dry weight measurements on 30 sample trees". Furthermore, the volume of standing trees was estimated using a volume tariff based on direct measurements of circumference at 1.30 and total tree height, all of which allowed us to estimate the biomass expansion and conversion factor (BECF) specific to the Oulmes Central Plateau cork oak. As a result, the volume and above-ground biomass were estimated at 55.74 m3/ha and 20.13 t/ha of dry matter respectively. Soil organic carbon stock and biomass (above and below ground) were estimated at 43.02 t/ha and 16.60 t/ha, respectively. The BECF, determined by the ratio between volume and biomass, was 0.59, which approaches the minimum value recorded under the same productivity conditions estimated by the IPCC (0.6-1.4).