The main objective of this research work was to study the Efficiency Index of Macronutrients in tree biomass in a Mixed Araucaria Forest through 20 primary sample plots of 12 m x 12 m. The efficiency indexes of macronutrients (EIMacronutrients) varied between the tree species, and between the biomass up ground components (stem = wood stem + bark; leaves and total = stem + branch + leaves). The species that show...