Regeneração natural de uma floresta na Amazônia Oriental: três décadas de dinâmica pós-exploração.

Abstract

Seeking to answer how the structure and the floristic diversity are influenced by silvicultural interventions in different phases of forest development, the present study evaluated the arrangement and dynamics of the forest natural regeneration in permanent plots for 31 years after logging in the Tapajós National Forest in Belterra – PA, Brazil. A total of 36 permanent plots of 50 x 50 m were installed and measured in 1981, 1983, 1985, 1987, 1992, 1997, 2007 and 2012. All individuals with total height (h) greater than 30 cm and DBH < 10 cm were monitored in three regeneration strata (seedlings, saplings and small trees/poles) and three forest classes (gap, under construction forest and old-growth forest). Density, floristic similarity by the Sorensen Index (So) and floristic diversity by the Hill Series were analyzed. The density of individuals was analyzed by ANOVA for counting data that showed differences over time after logging for all regeneration forest classes and strata. Likewise, the diversity profiles generated by the Hill Series for each year monitored in the same forest classes and regeneration strata, were statistically different from each other. The floristic similarity varied among the regeneration strata over time. For under construction and old-growth forests classes high floristic similarity were found between 50 and 98 %. The gaps presented the lowest values of similarity, reaching 98 % dissimilarity (So = 0,02). However, it was observed a reduction in similarity over time in both forest classes. The results indicate that the forest exploitation and the disturbances caused by natural events promote significant changes in the structure and floristic diversity in the different layers of natural regeneration and forest classes over time.