Estimation of above ground biomass of eucalyptus trees in Central Uganda

Abstract

Eucalyptus plantations are considered to be a short term and cost-efficient alternative for carbon sequestration given the rising atmospheric CO2 concentrations and global climate. The trees act as major CO2 sink which captures carbon from the atmosphere and acts as sink, stores the same in the form of fixed biomass during the growth process. Despite this known potential of eucalyptus plantations to store carbon in the biomass, there are relatively few studies including precise estimates of the amount of carbon in these plantations. Understanding the essential contribution of eucalyptus plantation for industry development and climate change mitigation requires the accurate quantification of aboveground biomass at the individual tree species level. However, the direct measurement of aboveground biomass by destructive method is high cost and time consuming. Therefore, developing allometric equations is necessary to facilitate this effort. Therefore, this study w as carried out with the purpose of estimating the aboveground biomass of eucalyptus trees in central Uganda. Forty eucalyptus tree samples were collected and taken to the laboratory for analysis. The Eucalyptus trees sampled in this study ranged in above a ground biomass from 3.3 to 70.7 kg DM plant-1. However, the trees averaged about 18.4 kg tree-1 on dry matter basis. The amount of dry matter reduced in the order Stem > Branches > Leaves > Twigs > Bark. This was the same trend in the proportion of total above ground biomass in each biomass part. The minimum and maximum dry matter biomasses in stem, branch leaf and bark were 1.72-46.36 kg Dmtree-1, 0.12-10.50 kg Dmtree-1, 0.11-9.0 KgDmtree-1 and 0.06-0.86 KgDmtree-1 respectively. The wood density of Eucalyptus trees in Uganda is 0.5754 g cm-3. This falls in the critical range 0.425-0.668 g m-3 reported for the wood basic density of E. globulus trees at harvest age for pulping. Model 5 was the most reliable arithmetic equation in the estimation of above ground biomass for Eucalyptus in central Uganda based on easy to measure predictor variables using the diameter at breast height and height.