Abstract:In order to development and utilization of Eucalyptus urophylla × E. grandis plantation, biomass and calorific values of 1- to 4-year-old E. urophylla × E. grandis were determined to reveal biomass and energy characteristics of Eucalyptus at different ages. The results showed that the biomass of leaves, branches, stem, roots, bark and total biomass increased with increasing age. The ratio of leaf, branch and bark biomass to total biomass decreased with age, while the ratio of stem biomass to total biomass increased. Biomass of 1- to 4-yearold individual and stands ranged from 4.32 to 66.29 kg, and 10.68 to 153.33 t hm-2, respectively. Biomass structure characteristics revealed that Eucalyptus plantation began to closure at the 4th year, and stem growth was dominant. Gross calorific values had significant difference (P<0.01) among five components, such as leaf, branch, root, stem and bark, with ranged from 17.23 kJ g-1 for bark to 20.56 kJ g-1 for leaf, those of the same component had no significant differences among different ages (P>0.05). The retained energy of 1- to 4-year-old individual and stands ranged from 81.61 to 1255.22 MJ and 201.83 to 2903.32 GJ hm-2, respectively, the change trend and orders of components were the same as biomass. Therefore, it suggested that E. urophylla × E. grandis energy plantation could manage with short rotation for 4 years.