In this paper we are setting the bases for the elaboration of energy maps of forest biomass. It shows the results obtained from the calculation of the calorific values and of the flammabilities of each of the forest species studied in Galicia (NW, Spain) along the year. With these data, it is possible to classify the species in terms of their energy content and of their resistance to forest fire. This classification is useful to draw realistic energy maps. With them, it will be possible to prevent and fight forest fires more effectively. These studies are complemented with chemical analyses of each forest species and bioclimatic diagrams of the areas to be studied. The main equipments used to carry out this research were an isoperibol calorimeter with agitated liquid in a static bomb, an epiradiator, an atomic absorption spectrophotometer and tools for elementary analyses.