Edge effects on the structure and dynamics of an Atlantic Forest fragment in northeastern Brazil

Abstract

Edge effects on the structure and dynamics of the canopy and understory of a forest fragment were examined in Igarassu, PE, Brazil. Two 10 × 100 m transects perpendicular to the forest edge (and divided into 10 × 10 m plots) were separated into outer (0-50 m) and inner edges (50-100 m) and their vegetations compared to those of 10 plots in a 20 × 50 m transect in the forest interior (280 m from the edge). The plots were the sampling units. All woody plants with stem perimeters at breast height (PBH) > 15 cm (canopy) were identified and measured within each plot. Plants with PBH < 15 cm and perimeter at soil level > 3 cm (understory) were also identified and measured in the 5 × 5 m subplots. Measurements were made in 2005 and repeated in 2008. Higher numbers of canopy species (39 in both edge) and plant densities (2020 and 2280, for inner and outer edge, respectively, in 2005. Similar results were observed in 2008) were encountered along the forest border, while higher understory species numbers (50), plant densities (9960 in 2005 and 13800 in 2008), and basal areas (2.8 in 2005 and 5.2 in 2008) were encountered in the forest interior. The number of recruited understory plants was lower along the forest border (55 individuals) and their mortality rate was higher (6.65 %yr^-1). The results indicated that canopy and undergrowth at the edge of the forest fragment studied were not totally recovered in structural terms, for most of the parameters analyzed.