Abstract:Energy characteristics of 6-year-old trees of Eucalyptus grandis, E. saligna, E. cloeziana, E. pellita and E. torelliana in Zhangmutou Forest Farm in southern Guangdong Province were studied. The results showed that there were significant differences in ash content and caloric value of various above and below ground components (P<0.01). Ash contents ranged from 0.16% to 8.37%, with the components in E. grandis, E. saligna, E. pellita and E. torelliana had order as leaves> bark>branches> roots>stem-wood, and that in E. cloeziana as bark>leaves>branches>roots>stem-wood. Gross caloric values (GCV) of various components ranged from 15.12 to 18.85 kJ g-1 with leaves having the highest GCVs and bark the lowest. For E. grandis and E. pellita, the order of components was leaves>branches> stem-wood>roots>bark, for E. saligna and E. torelliana was leaves>stem-wood>branches>roots>bark and for E. cloeziana leaves>branches>roots>stem-wood>bark. Ash free caloric values (AFCV) of components ranged from 16.37 to 19.87 kJ g-1 and the order of components by AFCVs were the same as those for GVCs for E. grandis, E. saligna, E. cloeziana and E. torelliana, and that for E. pellita as leaves>branches>bark> stem-wood >roots. For whole tree, E. grandis and E. pellita had the highest mean GCV and AFCV values respectively, while E. torelliana had the lowest.