Assessement of biomass contentsand carbon stock of plantation-grown neem specie (<i>Azadirachta indica</i>) in Yola, Nigeria

Abstract

The biomass contents and carbon stock of 22 years old plantation-grown neem (Azadirachta indica) species was assessed in Modibbo Adama University of Technology, Yola, Nigeria. Two-stage nested design was employed for data collection. Two plots of 100 x 100 m was randomly laid in  the plantation, 4 sub-plot of 20 x 20 m were nested in each corner of the super plots. The total numbers of trees in each of .the sub-plot were enumerated and recorded, while, the diameter at breast height (≥ 10 cm) and the total height of the trees were measured. For biomass estimation, two trees were harvested at stump height in each of the sub-plots, and were separated into components: bole, branch and the foliage. The tree bole
was sectioned into 2 m long billets, and a sample of 2-cm thick disk was extracted from top, middle and bottom of the 2 m sectioned bole. Green and oven-dry mass of the stem, branches and leaves were weighed to determine their moisture content (in percentage). Biomass contents were obtained as a product of tree volume, wood density and biomass expansion factor, while, the carbon stock was obtained by multiplying the biomass by constant (0.45). Results showed that the tree boles had the highest average biomass content of 22.30 kg, while the tree branch and the foliage had an average biomass of 2.53 and 0.008 kg respectively. There was no significant relationship (p > 0.05) between the estimated biomass and carbon stored by Azadirachta indica among the components assessed. The study has shown that the biomass content in the bole of A. indica is higher than those in the branch and leaf, while the stored carbon content is higher in the branch than the bole and the leaf components.

Keywords: Forest ecosystems, destructive, nested, Biomass, carbon stock.