Efeitos de área e de borda sobre a estrutura florestal em fragmentos de floresta de terra-firme após 13-17 anos de isolamento

Abstract

Density and biomass of live trees >10 cm DBH and saplings 1-9.9 cm DBH, coarse woody debris (LCG diameter > 10 cm), fine woody debris (LCF diameter 2.5-9.9 cm), and standing dead trees (> 10 cm DBH) were quantified in 56 permanent, 1-ha sample plots. These plots are located in four 1- (4 plots), three 10- (12 plots) and two 100- (14 plots) forest fragments in size and nearby continuous forests (19 plots) as well as in two classes of distance from the edges - < 300 m (29 plots) and > 300 m (21 plots). Density and biomass of primary species did not differ significantly among the four size categories and the two edge distance classes. However, forest fragments and distance < 300 m from the edges had more biomass and density of pioneer trees and saplings than did continuous forest and distance > 300 m from the edge, respectively. There were no significant differences among the size categories for standing dead trees. Forest fragments, however, had more quantity of LCG and LCF than did continuous forests. Moreover, distances < 300 m from the edges had higher quantity of LCG and LCF and total necromass than did distances > 300 m. We performed an ANCOVA to assess whether differences in LCG and LCF in fragments were due to proximity of forest borders. An ANCOVA showed that there was no significant effect of fragment size on necromass, but a significant effect of edge distance on both LCG and LCF. The quantity of LCG and LCF was correlated negatively with edge distance sites close to the edge presented over 40-60% more LCG than sites far from the edges in both forest fragments and continuous forests.