Ação antrópica e resultantes sobre a estrutura e composição da Mata Atlântica na Ilha Grande, RJ

Abstract

The Atlantic Rain Forest at Ilha Grande is constituted by a mosaic of different aged forests. I examined a successional gradient of 5-yr, 25-yr and 50-yr-old slope forests, growing in areas once used for subsistence agriculture by the caiçara people in what is today the Praia do Sul State Biological Reserve on Ilha Grande, Rio de Janeiro state. These areas were compared to a near-climax forest tract located in Ilha Grande State Park. There were 26 species in the 5-yr-old forest and a total basal area of 5.6 m2/ha; the 25-yr and 50-yr-old forests and the climax forest had 70 species, 26.3 m2/ha; 63 species, 32.4 m2/ha; and 134 species, 57.9 m2/ha, respectively. Species percentage distribution in ecological groups showed three distinct scenarios: a) dominance of pioneers (5-yr forest); b) dominance of early and late secondary species (25-yr and 50-yr-old forests); and c) dominance of climax species (climax forest). Shannon's Diversity Index for the four areas was 2.51, 3.33, 3.10 and 4.28 nats/ind. The 10 top species according to Importance Value decreased in percentage of total density, frequency and dominance from the 5-yr to the climax forest. The 25-yr and 50-yr-old forests were classified as manmade climax forests because the patterns studied evolved slowly.