Lowland bamboo (Oxytenanthera abyssinica) forest resources are most promising in Northwestern Ethiopia. The area's surrounding bamboo forest is significant both environmentally, economically, and socially. Nonetheless, no particular research has been done to ascertain the differences in biomass for the various sections of bamboo in both plantations and natural bamboo stands. Therefore, the purpose of this study was to determine the culm density and biomass variation across forest type and age gradients of Oxytenanthera abyssinica stand in Pawe, northwestern Ethiopia. Β One hundred eight (108) bamboo culms (54 from the plantations and 54 from the natural bamboo stands) were sampled destructively. After that, each of the specimens was divided into three sections (leaf, branch, and culm). The fresh weight of the sample and the total fresh weight of each portion were ascertained instantly. Then, samples were brought to the testing center for dry weight analysis, bundled in a paper bag. The data was subjected to descriptive statistical analysis employing R software. As the result showed, the mean height and diameter for the plantation stand ranged between 9, 13.2 m, 3.4 cm, and 6.4 cm, respectively, and the natural bamboo forest has mean height and diameter ranging between 6.35 and 12 m and 2.0 and 4.4 cm, respectively. The mean density of 0.51 g/cm3 for plantations and 0.41 g/cm3 for natural bamboo forests was recorded. Compared to natural forests, managed bamboo forests (stands) exhibit an increase of 17% in overall biomass production. While density rose with age, the medium-aged bamboo group in both forest types accumulated more above-ground biomass than the younger and older age groups