Spatial Distribution and Diametric Structure of Tree Species in a Dense Ombrophilous Forest in Rio Grande do Norte, Brazil

Abstract

The Atlantic Forest is considered to be one of the world's most biodiverse wetlands. However, the misuse of natural resources exposes it to physical and biogeographical changes caused by both natural and anthropic disturbances. Consequently, changes in the composition and structure of the remnants forests are expected. Although many studies are performed in this biome, few address the population structure and spatial distribution. The objective of this study was to analyse the spatial distribution pattern and the diametric structure of most representative tree species in a patch of Dense Ombrophilous Forest in the State of Rio Grande do Norte, Brazil. Floristic and parametric vegetation surveys were performed based on quadrants sampling, with 175 sampling points distributed systematically over five transects. At each point, four quadrants were defined, and the living arboreal individual closer to the center of the point, presenting diameter at breast height (DBH) ≥ 3.18 cm, was measured and identified. The Payandeh index was employed to detect the spatial pattern of the species. The diametric structure was analysed by the frequency distribution variation for each species and was estimated by Sturges method. Excluding Coccoloba alnifolia, the other species with high importance value index (IVI) in the forest patch showed an aggregate spatial distribution pattern or a tendency to group. It was observed that the diametric distribution pattern exhibted an inverted-J pattern, with some peculiarities. The study showed an unbalanced distribution for the studied species, but with a tendency to remain in the structural arrangement of the forest, once the human intervention is curbed. Except for C. alnifolia, the other species of higher IVI presented a pattern of aggregate distribution or tendency to aggregate. It was thus possible to understand the behaviour of these plant species of the environment, subsidising actions that aim at the conservation of the studied forest patch.