Allometric models for estimation of aboveground biomass of Combretum molle R.Br. ex G.Don. and Terminalia schimperiana Hochst. in Tulu Lafto Forest, Horo Guduru Wollega zone, Ethiopia

Forests play a key role in the global carbon cycle. Hence, accurate forest biomass estimation is crucial in climate change mitigation efforts and for monitoring carbon stock dynamics. This study developed allometric models used to estimate AGB of two indigenous tree species, namely, Combretum molle and Terminalia schimperiana, using a semi-destructive method. Diameter at breast height (DBH) and total height were measured for 40 selected trees per species across 10 plots (each 0.1 ha). Selected branches with leaves were trimmed for fresh and dry weight analysis. Samples were taken to the laboratory for dry-to-fresh weight ratio determination and further analysis. Wood density was calculated for both species. The results showed that C. molle had a significantly higher mean wood density (0.573 g/cm³) than T. schimperiana (0.476 g/cm³, p = 0.000), a significantly lower mean biomass (34.57) compared to T. schimperiana (266.13, p = 0.000). Linear regression analysis revealed that DBH was the most reliable predictor for AGB for both species. The study recommends using Model 2 for C. molle (DBH- 5-43cm) and Model 5 for T. schimperiana (DBH-5-60cm) for AGB estimation. It also emphasizes conserving and incorporating C. molle and T. schimperiana in national afforestation programs for carbon sequestration projects.