Structural Analysis and Distribution Patterns in Lowland Tropical Forest, Eastern Amazon

Floristic surveys allow us to make a momentary assessment of the structure and degree of conservation of the vegetation, supporting future actions for the sustainable use of forest resources. The aim of this work was to study the floristic and structural composition of fragments of floodplain forest in the Cajari River Extractive Reserve, Amapá state, Brazil. Systematic sampling was applied with the allocation of 27 plots of dimensions 10 m x 100 m each, with inclusion level of individuals greater than or equal to 10 cm in diameter at chest height. The floristic diversity of species was determined by the Shannon Diversity Indexes and Pielou Equability. The characterization of the horizontal structure was determined by the parameters: density, frequency and relative and absolute dominance, values of ecological importance and the diametrical distribution. The families Fabaceae and Euphorbiaceae were the ones that obtained the highest richness of species and number of individuals. The species Virola surinamensis Warb., Hevea brasiliensis (HBK) Muell. Arg., Pentaclethra macroloba (Willd.) Kuntze and Mora paraensis (Ducke) Ducke, were the most abundant. The várzea forest fragments presented high diversity and high ecological dominance of species. The J-inverted diametric distribution, characteristic of natural forests, indicates that it is a mature forest component with an expressive group of dominating (hyperdominant) species, such as the species V. surinamensis and M. paraensis. Most species presented aggregate distribution. It is hoped that these results may serve the environmental control and control bodies as strategies for the use of forest resources and in the design of the management plan of Resex.