1. Background
Pouteria adolfi-friederici is a tall tree of high forest, up to50 m tall, with the long, straight, more or less fluted trunk, and with buttresses at the base. It is an emergent or upper canopy species in montane moist forest and grows between 1350-2450m altitudinal ranges. The Phytogeographic distribution of the species includes Ethiopia, Sudan, Uganda, Kenya, the Democratic Republic of Congo, Zambia, Malawi, and Zimbabwe (Hedberg et al., 2003). This species is a high-value timber tree used for all types of woodwork. Although classified as ’not threatened’ on a global basis, the species and the high forest associated with it is rapidly being cut down and very little is being done to either conserve representative forests or replant the species in Ethiopia (Tesemma, 1993; Hedberg et al., 2003).
Allometric equations relate simply recorded variable (e.g. tree diameter, height) to other structural and useful features (Niklas, 1994), which is the most common and reliable method for estimating biomass, net primary production, and biogeochemical budgets in forest ecosystems (Gower et al., 1999). They have been developed to satisfy various purposes in forest ecology and management. Diameter at breast height (DBH) is commonly used as the only independent variable and most allometry develops an allometric relationship between DBH and component biomass (Gower et al., 1999). Some investigations proposed to incorporate tree height (H) as the second predictor and produce the DBH–H combined equation to increase the accuracy of biomass estimates (Ketterings et al., 2001). The allometric technique estimates the entire or partial (by compartments) mass of a tree from measurable tree dimensions, including trunk diameter and height, using allometric equations (Kangas and Maltamo, 2006). Thus, dendrometric parameters of all the trees are measured and using the allometric equation the biomass of the stand is estimated by summing the biomass of individual trees.
Generalized models have immense potential for large-scale carbon budgets computed from inventory data, (Pastor et al., 1984). When estimating the above-ground biomass of a forest, the uses of species-specific equations are preferred because trees of different species may differ greatly in tree architecture and wood density. However, due to the great number of different tree species in humid tropical rainforests and enormous efforts needed to develop these equations. Species-specific allometric equations for the humid tropics are almost absent while relatively few mixed-species equations have been developed (Ketterings, et al., 2001). This study was aimed to develop a species-specific allometric equation for Pouteriaadolfi-friederici , which can help the precise estimation of forest carbon stock in south western Ethiopia.