Effects of stand characteristics, topography, and management regime on biomass and volume of Eucalyptus globulus plantations in Ethiopia's Northeast Highlands

Abstract

Despite the rapid expansion of E. globulus due to its biomass and other commercial benefits in the Ethiopian highlands, the factors influencing its biomass productivity remain insufficiently studied, which is critical for its sustainable biomass and bioenergy production and utilization. This study evaluates the productivity of E. globulus plantations with managerial, topographic, and socioeconomic factors in the northeastern Ethiopian highlands. The data on stand age, plantation scale, stand originality, slope, and aspect from 76 plots, alongside a questionnaire survey on 225 respondents. The study utilized MANOVA, multiple regression model, and X² test for analysis. A significant interaction effect (p < 0.001) was observed in plantation productivity among stand characteristics, age, topographic, and socioeconomic contexts. Large-scale coppice plantations at age six, foot slope, and northeast aspect exhibited the highest mean annual increment of 5.8 m³ha⁻¹year⁻¹, total biomass of 28.6 Mg ha⁻¹, and volume of 29.7 m³ ha⁻¹. The stand age with foot slope, and northeast aspect have a great influence (p < 0.001, Adj. R² = 75 %, and RMSE = 1.57) on productivity of E. globulus plantation. The 98.2 % of respondents indicated that E. globulus plantations are established on marginal lands, characterized by low management intensity, quality, and productivity. Large-scale coppice plantations exhibit greater volume and biomass relatively, whereas its productivity was lower than central highlands of Ethiopia, Australia, and Brazil. The decline in biomass productivity is attributed to insufficient management and a low in extension services, highlighting the urgent need for skill development and policy reforms within the biomass plantation sector.