Estrutura e dinâmica da vegetação em um remanescente de Floresta Atlântica/Nordeste, Brasil

Abstract

RESUMO O efeito de borda causa uma série de alterações na estrutura da vegetação, microclima, dinâmica e composição de espécies, tornando esse ambiente bastante distinto do interior. Neste trabalho, foi analisada a influência da distância do limite florestal na estrutura e dinâmica (2006 e 2009) do dossel e do sub-bosque de um fragmento com 14 ha localizado na Floresta Atlântica em Igarassu, PE. A borda externa, formada há cerca de 35 anos, foi definida do limite florestal até 50 m, o ambiente intermediário de 50 e 100 m e o interior a 150 m. Para amostragem do dossel (indivíduos com diâmetro do caule a 1,30 m do solo > 4,77 cm) foram alocadas 10 parcelas de 10 × 10 m por ambiente e do sub-bosque (indivíduos com diâmetro do caule ao nível do solo entre 0,96 cm de diâmetro do caule ao nível do solo e diâmetro do caule a 1,30 m do solo < 4,77 cm) em sub-parcelas de 5 × 5 m instaladas no vértice superior e lado esquerdo das parcelas do dossel. Os valores de densidade e área basal do dossel foram semelhantes ao longo do gradiente borda -interior, enquanto no sub-bosque foram maiores no interior. A borda do dossel teve o maior incremento médio em diâmetro e foi o único ambiente a apresentar um recrutamento (número absoluto) maior que a mortalidade. No sub-bosque houve maior recrutamento que mortalidade em todos ambientes. A distância do limite florestal não influenciou a estrutura nem a dinâmica.Palavras-chave: dossel, efeito de borda, sub-bosque, vegetação ABSTRACT Edge effect produces a series of modifications on vegetation structure, microclimate, dynamics and species composition, making this environment very distinct from forest interior. In this study, the influence of distance from the forest border on the structure and dynamics (2006 and 2009) of canopy and understory assemblages was analyzed in a 14 ha fragment of Atlantic Rainforest in Igarassu, PE, Brazil. The edge, formed about 35 years ago, was defined as area between the forest margins up to 50 m inwards; the intermediate environment was considered from 50 m to 100 m; and the interior environment beyond 150 m from the edge line. In order to sample the canopy (individuals with stem diameter > 4.77 cm at 1.30 m from the ground) ten 10 × 10 m plots were allocated in each environment; for sampling the understory (individuals with stem diameter at ground level > 0.96 cm up to stem diameter at 1.30 m < 4.77 cm) sub-plots of 5 × 5 m were located at the apex and the left side of the canopy plots. Density and basal area of canopy were similar along the edge -interior gradient, whereas the understory had greater values in the interior. For the canopy, the edge showed the highest average increment in diameter and was the only environment to provide recruitment (absolute) higher than mortality. For the understory, in all environments, recruitment was greater than mortality. Distance from forest margins did not influence forest structure and dynamics.

Floristic Composition and Edge-Induced Homogenization in Tree Communities in the Fragmented Atlantic Rainforest of Rio De Janeiro, Brazil

“…In addition, due to the similarity of the edge habitats, it is likely that only the best performing subset of pioneers will dominate the edge habitats throughout the landscape. Although some studies have found a higher diversity in edges than in the corresponding interior [82,83] we believe, in view of the large number of recent studies and reviews [15,28,[84][85][86] that support our findings, that the opposite might be the usual pattern in forest fragments, at least in tropical southeast Brazil. A higher diversity of edge habitats may exist shortly after edge creation, when some elements of the original tree flora are still present, although not reproducing, and pioneer species are beginning to proliferate [77,87].…”

Temporal Behavior of Tree Communities in Different Soil Classes

“…On this scale, the reduced area favors lower heterogeneity due to the more similar physical conditions (light, water, soil, etc.) (Costa et al, 2012). On the other hand, on larger area size entails greater environmental heterogeneity (Cavender-Bares et al, 2009).…”

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

“…Little data has been gathered from the extremely fragmented Brazilian Atlantic coastal forest in the northeastern region of that country (Oliveira et al, 2004;Santos et al, 2008). Laurance et al (1998a) reported greater tree mortality along the forest border than in the interior of 10 and 100 ha fragments in the Amazon region, while mortality and recruitment in both the canopy and understory were found to be similar along the border and in the interior of 14 (Costa et al, 2012) -which could have resulted from the homogenization of the vegetation in those highly fragmented sites .…”