The objective of the study was to determine the diversity and aerial biomass in the middle terrace forests of Puerto Almendra, Loreto, Peru. All trees with DBH ? 10 cm, existing in two plots of 1.2 ha in the CIEFOR “El Huayo” arboretum, distributed in each plot of the forest, were evaluated with the non-destructive method. He index of the specific wealth of Margalef indicate,that in plot VII it has an index of 16.69 and in plot VIII it reports an index of 15.35, indicating high specific richness of the species; both plots the Simpson dominance index is 0.97, which indicates a high diversity and dominance of the species; the Shannon-Wiener equity index, plot VII shows a high index of 4.05 and VIII shows a low index of 3.96, which indicates that both plots have a high diversity of tree species; Fisher's Alpha index of plot VII shows 37.64 and plot VIII with 33.41 indicates a high diver...