Phytosociology in agroforestry systems of different ages in the town of Medicilândia, Pará, Brazil = Fitossociologia em sistemas agroflorestais com diferentes idades de implantação no município de Medicilândia, PA

Agroforestry systems are emerging as an alternative to the degradation of natural resources, since they allow for harmony between agriculture and forest species, guaranteeing environmental sustainability. The aim of this work was to evaluate floristic composition and compare the structure of three agroforestry systems of 20, 30 and 40 years of age, in the town of Medicilândia, in the State of Pará. For the floristic and structural analysis, a forest census was carried out of the three agroforestry systems, recording all tree individuals with a diameter at breast height >10 cm. In analysing the horizontal structure, the absolute and relative phytosociological parameters of density and dominance were considered. The absolute and relative parameters of sociological position and natural regeneration were calculated when analysing the vertical structural of the systems. For the analysis of the Expanded Importance Value Index (IVIA), all the relative vertical and horizontal parameters were added together. The agroforestry systems displayed an inverted-J diametric distribution. As they are key species when planting forests, Swietenia macrophylla and Tabebuia impetignosa were the most important in each agroforestry system. Natural regeneration favoured the establishment of species with commercial value that were not part of the initial arrangement of the AFSs, such as Bagassa Guianenses, Tabebuia serratifolia, Schizolobium amazonicum and Dipteryx odorata, demonstrating the economic and ecological sustainability of these systems. = Os sistemas agroflorestais surgem como alternativa à degradação dos recursos naturais, pois possibilitam a harmonia entre agricultura e espécies florestais, garantindo a sustentabilidade ambiental. Objetivou-se com o presente trabalho avaliar a composição florística e comparar a estrutura de três sistemas agroflorestais com idades de 20, 30 e 40 anos no Município de Medicilândia, PA. Para análise florística e estrutural, realizou-se o censo florestal nos três sistemas agroflorestais, inventariando todos os indivíduos arbóreos com diâmetro a altura do peito > 10 cm. Para a análise da estrutura horizontal, foram considerados os parâmetros fitossociológicos absolutos e relativos de densidade e dominância. Os parâmetros absolutos e relativos da posição sociológica e regeneração natural foram calculados para a análise estrutural vertical dos sistemas. Para análise do Índice de Valor de Importância Ampliado (IVIA), foram somados todos os parâm