Características de clareiras e seus efeitos sobre riqueza de espécies em floresta monodominante de Vochysia divergens

Abstract

In tropical regions there is a considerable number of publications on canopy gaps, none of them performed in monodominant forests, forest formations with predominance of over 50 individuals of a single tree species. This study aimed at characterizing the origin and area of canopy gaps in a monodominant forest of Vochysia divergens (Cambarazal), and evaluating the relationship between the gap area and species richness. The following hypotheses were tested: (1) V. divergens is the principal gap-maker; (2) The larger the gap area is the greater the number of individuals and species richness are. The Cambarazal area studied is located in the municipality of Barão de Melgaço, PELD Site 12, Northern Pantanal-MT. The line intercept method was used here in five transects of 500m to sample all woody individuals with height >1m and DBH ≥1,6cm. The species were identified and the gap area was measured according with the concept of "expanded gaps". The probable agent of death and/or fall and the type of damage caused to the individual were identified. Analysis of variance (ANOVA) and linear regressions were used in order to examine the relationship between gap characteristics and the vegetation structure and composition. Nine species were identified as agent of death, summing 276 individuals, with Vochysia divergens being the principalagent of death. The predominant gap-maker was "treefall" (40.2%, 111/276). Most gaps (91.1%, 31/34) were created for more than one agent of death. A total of 34 gaps were sampled, with an area ranging from 450 m2 to 6,842m2. The number of individuals ranged from 23 to 572 individuals, summing 4,020. The species richness varied from seven (7) to 31 species. The gaps were represented by 46 species, distributed in 40 genera and 24 families. The relationship between the number of individuals and the gap area was significant and positive, but there was no significant relationship between species richness and gap area.