The objective of this study was to evaluate the composition, diversity, and structure of tidal “Várzea” and “Igapó” forests in eastern Amazonia, Amapá, Brazil. All live tree individuals with diameter at breast height (dbh) ≥10 cm were registered. A total of 130 plots measuring 10 × 100 m were inventoried, distributed among 13 ha in each of the two forest typologies. A total of 10,575 trees were reported, belonging to 343 species, 172 genera, and 49 families. For all 26 ha sampled, mean tree density was 406 ± 61.27 trees ha−1 and mean basal area was 27.2 ± 11.13 m2 ha−1. Fabaceae, Arecaceae, Malvaceae, Meliaceae, and Rubiaceae were the most important families in tidal “Várzea”, together accounting for 74.76 % of the family importance value index (FIVI %). In “Igapó”, the most important families were Lecythidaceae, Euphorbiaceae, Malvaceae, and Arecaceae, which together accounted for 57.05 % of the family important value index (FIVI %). Smaller diameter trees measuring between 10 and 30 cm dbh dominated the landscape, accounting for 75.52 % of all individuals sampled. In general, 80 % (8285) individuals were under 24 m in height, while only 1.32 % of trees (140) reached heights above 34 m. There was evidence for statistically significant mean differences among tidal “Várzea” and “Igapó” with regard to the number of individuals, species, diversity, and tree height. However, no mean differences were detected for equitability, dbh, dominance, and basal area. Compositional patterns showed low similarity between the evaluated areas, indicating the existence of phytogeographic pattern based on species distribution.
Dominance Phytosociology Similarity Species distribution
We thank the Institute of Scientific and Technological Research of Amapá (IEPA) for logistical support and the Fundação de Amparo à Pesquisa do Estado do Amapá for financial support. We thank Embrapa Amapá for macronutrient analyses, the National Research Institute of the Amazon (INPA), and the Botany post-graduate course at INPA for providing facilities and the opportunity to conduct the research. MJVC was supported by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).
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