Diversidade, composição florística e distribuição diamétrica do povoamento com DAP > 5 cm em região de estuário no Amapá.

Abstract

The structure and floristic composition of two forested areas (Lontra of pedreira and Mazagão) in the Amazon River Estuary of Amapá state were determined. Lontra of Pedreira is located in the coordinates of 00º 03º N and 50º 37* W, covering 75 ha and Mazagão, in the coordinates of 00º 30' S and 51º 13 W E, 90 ha. Ateach study area, five 1ha plots were selected to measure all trees with DBH = 5 cm and to characterize the vegetation on the basis of floristic composition, diameter distribution, Importance Value (IVI), Shannon-Weaver's diversity index, indices of similarity, and mixture quotient. 5884 individuals were found distributed across 32 families, 54 genera, and 67 species at Lontra of Pedereira. The most abundant species included Astrocaryum murtumuru, Euterpe oleracea, Crysoplivilum excelsum, Calypiranihes speciosa and Trichilia surinamensis. The most abundant families were Arecaceae, Sapotaceae, Myrtaceae, Meliaceae and Mimosaceae. At Mazagão, 5166 individuals were found distributed in 33 families, 78 genera, and 88 species. The most abundant species were Parinari excelsa, Astrocaryum murumuru, Pariana campestris, Prerocarpus amazonicus and Euterpe oleracea. Both studied areas showed diameter distribution in the typical inverted-] pattern, which is characteristic of tropical forests. At Lontra da Pedreira, the most important species by Importance Value (IVI) included Enterpe oleracea, Astrocaryum imurumuru, Licania heteromorpha, Callycoplyllum spruceanum and Crysophyltum excelsum, and the most important families were Arecaceae, Chrysobalanaceae, Rubiaceae, Moraceae and Sapotaceae. At Mazagão, the species with the highest IVI were Euterpe oleracea, Callycophyllum spruceanum, Pentaclethra macroloba, Licania heteromorpha and Astrocaryum murumuru and families with highest IVI were Arecaceae, Rubiaceae, Mimosaceae, Caesalpiniaceae and Meliaceae. The Shannon-Weaver diversity index was 1.93 at Lontra da Pedreira and 2.72 at Mazagão. Sorensen's similarity index between the two study areas was 53% and Czekanowski's similarity index was 37%. These results indicated a low level of species diversity in the two areas and dominance of Euterpe oleracea and Astrocaryum murumuru.