Ecosystem Health and Sustainability (Jan 2018)
Allometric equations for aboveground biomass estimation of Olea europaea L. subsp. cuspidata in Mana Angetu Forest
Abstract
Introduction: African wild olive, Olea europaea L. subsp. cuspidata (Wall. ex G. Don) Cif., L ‘Olivicoltore is widely distributed in dry forest and forest margins, often with Juniperus procera, in east Africa and Ethiopia. It reaches southern Africa, also India and China, ranging from tall trees to stunted shrubs. Does best in good forest soil, but hardy and drought resistant once established, even in poor soils. It is used for firewood, charcoal, poles, posts, timber (furniture, carving, floors, and paneling), medicine (stem, bark, and leaves), bee forage, milk flavoring (smoking wood), toothbrushes (twigs), and walking sticks. Although the species has many economic and ecological functions, its environmental uses like carbon storage and climate change mitigation are less assessed. Therefore, the objective of the study was to develop species-specific allometric equations for O. europaea L. subsp. cuspidata using semi-destructive method and evaluate allometric models for estimating the aboveground biomass (AGB). Results and Discussions: After all the necessary biomass calculations were done, seven AGB equations were developed. These regression equations relate AGB with diameter at breast height (DBH), height (H), and density (ρ) individually and in combination. Out of seven, four allometric equations were chosen based on goodness-of-fit statistics and three were rejected. The selected models were tested for accuracy based on observed data. The best models selected have higher R2-adj and lower residual standard error and Akaike information criterion than rejected equations. The relations for all selected models are significant (p < 0.000), which showed strong correlation of AGB with selected dendrometric variables. Accordingly, the AGB was strongly correlated with DBH and was not significantly correlated with wood density and height individually in O. europaea L. subsp. cuspidata allometric equation development. In combination, AGB was strongly correlated with DBH and height; DBH and wood density; and the combination of DBH, height, and wood density. Species-specific equations are used for better carbon assessment than general equations.
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