Riqueza e composição de espécies da floresta de igapó e várzea da Estação Científica Ferreira Penna: Subsídios para o plano de Manejo da Floresta Nacional de Caxiuanã

The floodplains of the Amazon can be differentiated depending on the type of flooding, water and soil qualities, geological origin, vegetation structure and species composition. In the Brazilian Amazon, the most representative types are those flooded periodically by white water rivers (locally called várzea) and by black water rivers (called igapó). In these environments, the fundamental factors for the maintenance of biodiversity are the physical and biological processes, mainly the hydrological and sedimentational cycles. The objective of the present study was to test the differences of richness, structure and composition of tree species in a forest of igapó and várzea in the Cientific Station Ferreira Penna, on the lower Amazon in the state of Pará. The cumulative curve of new species per area reached the asymptote in the várzea and only a tendency towards an asymptote in the igapó forest. At community level, tree diameter distribution of both, igapó and várzea, showed an inverse j-shaped curve which is typical for tropical forests. 42 species were identified in the floodplain forests, richness being significantly higher in the igapó forest than in várzea (30 and 19 species, respectively). The basal area was significantly lower in the igapó forest than in várzea. It was possible to group the sampled transects, and the results show a clear separation of the two types of floodplain forest indicating different species compositions