Vegetation Diversity And Carbon Stock Of Natural Regeneration Woodlands Of Kishapu District, Tanzania

ABSTRACT

Natural regeneration woodlands have the potential for enhanced carbon sequestration and climate change mitigation although little is known on vegetation species diversity and the associated carbon dynamics. A study was carried out among three selected natural regeneration woodlands (Nyasamba, Bubinza and Ndoleleleji) of Kishapu district aimed (1) to determine plant species diversity, (2) to quantify herbaceous biomass productivity, (3) to determine tree stocking capacity, and (4) to quantify soil organic carbon (SOC). A nested model design comprised of four radii (r = 2, 5, 10 and 15 m) concentric plots were established at 300 m between plots. Inter-transect distance was maintained at 550 m. A sampling intensity of 0.3% which is equivalent to 74 sample plots was adopted. Data on vegetation species diversity, biomass productivity, forest stocking parameters and SOC were computed into means using analysis of variance (ANOVA). Dominant grass species were Aristida spp., Cyperus spp., Cynodon spp. and Cenchrus spp. Forb species were Monechma spp., Leucas spp., Commelina spp., Sida spp. and Cucumis spp. The woodlands were dominated by Acacia spp. (A. drepanolobium, A. nilotica, A. polyacantha, A. senegal, A. seyal, and A. tortilis), Dichrostachys cinerea and Balanite aegyptica. Herbaceous biomass productivity was low (1.15-1.23 t DM/ha), (P˂0.05). The woodlands were characterised by low plant species diversity ranging from 0.11 to 0.48 for Simpson‟s index of diversity (C). Tree stocking parameters depict high tree stocking density of 1021±198 to 2003±295 stems/ha, moderate basal area of 6.11±2.1 to 7.64±3.1 m2 /ha, and high tree standing volume ranging from 41.02±13.1 to 50.08±19.5 m3 /ha. Above-ground carbon stock (AGCS), was variable across sites (11.9±3.8-14.5±5.7 t/ha), (P˂0.05). Below-ground carbon stock (BGCS), ranged from 2.97±1.00 to 3.63±1.4 t/ha. Concentration of soil organic carbon (SOC) was variable across soil horizons, with high concentration on the 0 to 30 cm depth (0.12±0.05-0.7±0.07 kg/m2 ). It could be concluded that natural regeneration woodlands of Kishapu district has a promising herbaceous biomass productivity as well as good tree carbon stocking potential which influences species diversity.