Energy demand, especially in developing countries, is partly supplied by firewood and charcoal from natural forests. However, there are not always previous studies of energy quality, with implications for forest management. This study aimed to characterize the energy potential of the wood of six shrub-tree species from the Caatinga and the influence of the circumference class on their chemical properties and energy potential to subsidize forest management. Thus, Anadenanthera colubrina var. cebil (Angico), Cenostigma bracteosum (Catingueira), Cnidoscolus quercifolius (Faveleira), Mimosa ophthalmocentra (Jurema branca), Mimosa tenuiflora (Jurema preta) and Aspidosperma pyrifolium (Pereiro) from an area of Dry Forest (Caatinga) in Floresta, Pernambuco state, Brazil, were analyzed. Each species had three individuals sampled in five circumference classes (I a V) at 1.30 m from the ground. Carbon, hydrogen, nitrogen, insoluble lignin, and ash contents, as well as higher and lower calorific values, apparent and energetic densities and energy production were evaluated. Then, a completely randomized design in a factorial arrangement (species x circumference classes) with three replications, and comparison of means (Tukey's test, p < 0.05) were considered in the statistical analysis. A Cluster analysis was also performed aiming at joint analysis of variables. The results showed that the biomass of M. ophthalmocentra and M. tenuiflora have the highest energy density and amount of energy per unit of mass. C. quercifolius and A. pyrifolium were lower when compared to the other species. In addition, M. ophthalmocentra, M. tenuiflora, A. colubrina and C. bracteosum stood out for energy generation. Classes IV and V can be indicated as biomass for combustion, while class I has disadvantages due to higher nitrogen content and lower upper and lower calorific values.
