Abstract
Approximately 7.2% of the Atlantic rainforest remains in Brazil, with only 16% of this forest remaining in the State of Rio de Janeiro, all of it distributed in fragments. This forest fragmentation can produce biotic and abiotic differences between edges and the fragment interior. In this study, we compared the structure and richness of tree communities in three habitats - an anthropogenic edge (AE), a natural edge (NE) and the fragment interior (FI) - of a fragment of Atlantic forest in the State of Rio de Janeiro, Brazil (22°50'S and 42°28'W). One thousand and seventy-six trees with a diameter at breast height > 4.8 cm, belonging to 132 morphospecies and 39 families, were sampled in a total study area of 0.75 ha. NE had the greatest basal area and the trees in this habitat had the greatest diameter:height allometric coefficient, whereas AE had a lower richness and greater variation in the height of the first tree branch. Tree density, diameter, height and the proportion of standing dead trees did not differ among the habitats. There was marked heterogeneity among replicates within each habitat. These results indicate that the forest interior and the fragment edges (natural or anthropogenic) do not differ markedly considering the studied parameters. Other factors, such as the age from the edge, type of matrix and proximity of gaps, may play a more important role in plant community structure than the proximity from edges.
Highlights
The Atlantic forest is the natural biome of almost the entire eastern region of Brazil and covers close to 1,300,000 km2 in sixteen Brazilian states (MORELLATO and HADDAD, 2000)
Only 7.2% of the Brazilian Atlantic forest remains, all of which is distributed in fragments and, in the State of Rio de Janeiro, where this vegetation once covered almost the entire territory, barely 16% remains (MORELLATO and HADDAD, 2000)
When a tree had more than one trunk at breast height, the diameter was obtained from the sum of the basal areas (Ba, in cm2) of each trunk, using the formulas Ba = P2(4π)-1 and D = 2(ΣΒaπ-1)0.5
Summary
The Atlantic forest is the natural biome of almost the entire eastern region of Brazil and covers close to 1,300,000 km in sixteen Brazilian states (MORELLATO and HADDAD, 2000). Compared to the interior of the forest fragment, a forest edge can experience changes in microclimatic conditions such as increase in temperature, light exposure and wind intensity, and decrease in air and soil moisture (MURCIA, 1995; TABARELLI et al, 1999; NELSON and HALPERN, 2005). These microclimatic changes may cause differences in the tree density and structure of these forest remnants (METZGER et al, 1997; OLIVEIRA-FILHO et al, 1997). Microclimatic modifications can produce biotic differences in plant composition and diversity because of tree mortality and recruitment (LAURENCE et al, 1998; OLIVEIRA et al, 2004)
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