Allometric Equation for Biomass Estimation of Pouteria adolfi-friederici (Engl.) Baehni in Gerba Dima Forest, South western Ethiopia

Abstract

This study was conducted in Gerba Dima Forest, South Western Ethiopia to formulate allometric equations for Pouteria adolfi-friederici. Prior to collecting data for tree allometry, the study forest was stratified into 3 forest strata based on altitudinal variation. By employing semi-destructive technique, 30 individuals were systematically selected and sampled for measuring biomass along the three forest strata. Based on the data collected, several equations were developed. Before establishing the allometric equation, scatter plots were used to see whether the relationship between independent and dependent variables was linear. Furthermore, several allometric relationships between independent and dependent variables were tested. The best-fit model developed was validated by testing the regression assumptions. AGB was regressed against the various forms of predictors (i.e., DBH, H and WD) and three allometric models showed significant performance (p < 0.05) on their F-test. Among the three allometric equations which showed significant performance, the selection of the best-fit model was conducted based on their P-value, adjusted r2, AIC, RMSE. The two models are nested to the third model and hence the complete model, lnAGB=1.806+1.419×lnDBH+0.628×lnWD, is selected as the best-fit model against the other two nested models since the p-values of coefficients of the complete model are significant (p < 0.05).