Estudo comparativo de diversidade florística em florestas de terra firme da Amazônia oriental

Abstract

Patterns of diversity and abundance of tree species in the Amazon are poorly known, revealing the absence of consistent studies on the biological, physical, and geomorphological factors that control these patterns. This paper compares the diversity and structure of tree communities in 5.7 ha at the Mocambo Forest Reserve in Belém (PA), 6 ha at the Ferreira Penna Scientific Station in Caxiuanã (PA), and 5 areas, in which 1 ha each was inventoried: Altamira (PA), Capitão-Poço (PA), Carajás (PA) Km 15 (RO), Kaapor (MA). The areas consist of primary terra firme forests growing on Argilo-Sandy Oxisols of Tertiary origin. The sampling unit was the hectare. Trees, stipes, and woody vines with stem diameter 3 10 in, measured at 1.30 m from the ground, were inventoried at the sites. The results showed that compared to the two largest inventory areas, Caxiuanã has a higher floristic richness of species (40%), but the number of families and density are equivalent to Mocambo. Leguminosae (sensu lato), Lecythidaceae and Sapotaceae were the richest and most abundant families in both sites. The abundance reveals that in both communities there is a high number of locally rare species (1 plant/ha) compared to common species (15 plants/ha). In the 1 ha inventories, the highest species mixing coefficient was in Altamira and Km 15 (RO) with 74% and 69% respectively, while Kaapor (MA), Carajás (PA) and Capitão-Poço showed 41 %,37% and 35%. The Leguminosae family showed the highest abundance in two environments (Altamira and Carajás) and the Sterculiaceae family was the second most abundant in three environments (Capitão-Poço, Kaapor and Km 15). Most rare species are mutually exclusive and the similarity between areas is positively correlated with abundance.