A management tool for estimating bioenergy production and carbon sequestration in Eucalyptus globulus and Eucalyptus nitens grown as short rotation woody crops in north-west Spain

This study proposes stand level models for estimating biomass yield, total energy and carbon sequestration in Eucalyptus globulus and Eucalyptus nitens plantations, on the basis of measurements made in 131 plots established at the usual range of initial forest densities for southwestern Europe. The timber volume, total aboveground biomass, logging residue biomass, crown biomass, carbon in aboveground biomass and soil organic layer, energy in aboveground biomass, energy in logging residue biomass and usable cellulose yield were represented in the form of isolines (taking mortality into account) and plotted against dominant height. These variables were calculated and compared with previously published data on two silvicultural options for short rotation forestry, one destined for bioenergy production and the other consisting of the standard silviculture regime applied to both species in southern Europe, considering the average site index for each species. Yield levels were higher in E. nitens than in E. globulus for all variables because of faster diameter increment at similar densities. The total yield in terms of biomass was 13.9-14.6 Mg ha⁻¹ y⁻¹ for E. globulus and 20.4-21.5 Mg ha⁻¹ y⁻¹ for E. nitens. Energy in aboveground biomass ranged between 233 and 245 GJ ha⁻¹ y⁻¹ for E. globulus and 345 and 364 GJ ha⁻¹ y⁻¹ for E. nitens, carbon accumulation rate in aboveground biomass and soil organic layer was 6.9-7.2 Mg ha⁻¹ y⁻¹ for E. globulus and 12.7-13.5 Mg ha⁻¹ y⁻¹ for E. nitens, and usable cellulose was 5.7-5.9 Mg ha⁻¹ y⁻¹ for E. globulus and 9.0-10.1 Mg ha⁻¹ y⁻¹ for E. nitens. It was found that 50% increments in the initial density result in only marginal increments in biomass and usable cellulose yields.