ABSTRACT
Dry Afromontane forests form the largest part of the existing natural vegetation in Ethiopia. Nevertheless, models for quantifying aboveground biomass (AGB) and the volume of this forest are rare. The development of tree allometric models is crucial for accurate forest tree volume, biomass, and carbon assessment in the forest ecosystem. The objective of this study was to develop species-specific models for predicting AGB and tree volume of the Olea europaea L.sub spp. Cuspidata in the Harego forest. A total of 15 sample trees were harvested and their biometric variables and biomass were measured. A set of models relating tree component volume and biomass to measured variables and wood density were developed using linear regression analysis.
The form factor of the species was determined, the predicted values using form factor and fitted stem equation were comparable and provided accurate results. Log transformed data revealed that combined diameter at breast height (dbh) and merchantable height explained more than 95.6 % variability in the stem and total volume. Branch biomass was determined by dbh alone, explaining 87.7% of the variation in the branch volume. The average value of wood density decreased with increasing stem height and decreasing branch diameter sizes. wood density of the stem was higher than the branch. A large part of the variation in tree component biomass was explained by both dbh and ht, whereas dbh alone explained 75.9% variability in the leaf biomass with high bias. The direct biomass measurement was 18.6% greater than the indirect measurement. The comparison with previously developed species-specific and general models revealed that these models produced large prediction errors and they cannot probably be applied outside their ranges. Thus, our new models are accurate and potentially to be applied for species-based tree component biomass predictions and will be helpful in planning sustainable forest management in the dry Afromontane forest.
Keywords: Destructive sampling, Form factor, Models, Wood density.
