Mixed-Species Allometric Equations to Quantify Stem Volume and Tree Biomass in Dry Afromontane Forest of Ethiopia

Abstract

Volume and biomass equations are essential tools to determine forest productivity and enable forest managers to make informed decisions. However, volume and biomass estimation equations are scarce for Afromontane forests in Africa in general and Ethiopia in particular. This limits our knowledge of the standing volume of wood, biomass, and carbon stock of the forests therein. In this study, we developed a new mixed-species volume and biomass equations for Afromontane forests and compared them with generic pantropical and local models. A total of 193 sampled trees from seven dominant tree species were used to develop the equations. Various volume and biomass equations were fitted using robust linear and nonlinear regression. Model comparison indicated that the best model to estimate stem volume was How to cite this paper:

Volume and aboveground biomass models for a dry evergreen montane forest in Tanzania

“…Furthermore, Mwakalukwa et al (2014) argued that due to the variation in species composition from site to site and the impact of site conditions on the shape of trees, the use of mixed-species regression models calibrated using data from sites with similar conditions and species composition is a logical choice. However, using biomass-generalized allometric equations available for tropical forests (Brown et al 1989;Chave et al 2005;Djomo et al 2016) gave lower results and tended to give higher errors (Teshome et al 2022). For instance, Brown et al (1989) biomass model gave an error of 5.5%, while that of Chave et al (2005) had a much higher error of 15.1%, implying that site-specific mixed species biomass models developed in this study are more accurate by having a much lower error of 1.93% in the prediction.…”

“…A total of 30 sample trees and shrubs (Table 1) with a diameter range of 5-58.5 cm were selected based on species composition and diameter classes of species available in the forest (Mwaluseke 2015, unpublished data). The selection ratio was five trees to 1 shrub (Chaturvedi and Raghubanshi 2012;Mwakalukwa et al 2014;Asrat et al 2020;Teshome et al 2022). Few shrubs were selected because they possessed lower diameter size classes and are the least contributor to total volume and biomass than the large-sized trees (Asrat et al 2020;Teshome et al 2022).…”

“…The selection ratio was five trees to 1 shrub (Chaturvedi and Raghubanshi 2012;Mwakalukwa et al 2014;Asrat et al 2020;Teshome et al 2022). Few shrubs were selected because they possessed lower diameter size classes and are the least contributor to total volume and biomass than the large-sized trees (Asrat et al 2020;Teshome et al 2022). The selected trees and shrubs species were first identified before they were felled (Table 2) (Mwakalukwa et al 2014;Malimbwi et al 2016).…”

“…The selected trees and shrubs species were first identified before they were felled (Table 2) (Mwakalukwa et al 2014;Malimbwi et al 2016). After identification, the trees were measured for diameter at breast height (DBH at 1.3 m) using diameter tape/caliper to the nearest 0.1 cm (Teshome et al 2022). The trees were also measured for their height using a Suunto hypsometer.…”

“…The additivity concept was attained by summing the biomass and volume components (stem wood, branches, and leaves). Thus, ensuring that the total biomass and volume obtained equaled the total biomass and volume predicted by allometric equations (Asrat et al 2020;Teshome et al 2022). Next, for each tree, the volume of individual stems and branch billets was calculated using Huber's formula (V=π Ld 2 m/4; where dm= Billet's mid-diameter, L=Billet length, π = Pai, V= billet volume).…”