Efeitos de borda sobre a comunidade de pteridófitas na Mata Atlântica da região de Una, sul da Bahia, Brasil

Abstract

-(Edge effects on pteridophyte community in Atlantic rain forest of the Una region, South of Bahia State, Brazil). Edge effects are one of the most important consequences of forest fragmentation. This paper concerns how richness and abundance of pteridophytes vary when forest interiors and edges are compared on the fragmented Una landscape, state of Bahia. All ferns found up to 1 m above the ground were collected on 36 parcels of 120 × 10 m. Six sampling units were established on continuous forest areas (> 900 ha) and six more on forest fragments (≤ 100 ha). These units were allocated within three sampling blocks of 5 × 5 km over Una landscape. Each area had its parcels positioned at 20 m, 40 m, and further than 100 m from the border line, which was drawn by the cattle pastures areas passing through forest patches on the landscape. There was no significant variation of abundance among studied units, although richness decreases in all blocks, when parcels are closer to the matrix. Species richness is reestablished 20-30 m far from the border, where it has no significant difference to that of forest interior. In addition interior and border of forests are totally different environments, regarding pteridophytes community. Forest interior communities are almost not affected by edge effects. Therefore, border effects have a short penetration on pteridophytes communities, although a large scale raise on the amount of borders might result on the extinction of some local forest species.Key words -Bahia, edge effect, ferns, forest fragmentation RESUMO -(Efeitos de borda sobre a comunidade de pteridófitas na Mata Atlântica da região de Una, sul da Bahia, Brasil). Uma das conseqüências da fragmentação de hábitats florestais melhor estudadas até o momento são os chamados efeitos de borda. Neste estudo, foi verificado como variam a riqueza e a abundância das pteridófitas quando são comparados interiores e bordas de áreas florestais, em Una, BA. Foram inventariadas todas as pteridófitas a até 1 m do solo, em 36 parcelas de 120 × 10 m (0,12 ha), estabelecidas em áreas de mata contínua (> 900 ha) e fragmentos de mata (≤ 100 ha), distribuídas na região entre três blocos amostrais de 5 × 5 km. Em cada uma das áreas, locaram-se as parcelas a 20, 40 e a mais de 100 m da divisa da mata com relação às áreas adjacentes. Os resultados mostram que não há variação na abundância entre as unidades consideradas. No entanto, a riqueza de samambaias é diferente entre blocos amostrais, indicando que as florestas de Una podem ser heterogêneas quanto aos aspectos ambientais. Além disso, a riqueza decai nas parcelas de borda mais próximas à matriz, em todos os blocos; a partir de uma distância aproximada de 20-30 m a riqueza é restabelecida, tornando-se similar à do interior da floresta. Também fica claro que os interiores de floresta constituem ambientes totalmente distintos daqueles de borda, no que se refere à comunidade de pteridófitas, de modo que, praticamente, não são afetados pelos efeitos de borda. Pôde-se concluir que os efeito...

The effects of fragmentation on Araucaria forest: analysis of the fern and lycophyte communities at sites subject to different edge conditions

“…Nevertheless, it was observed that the edge effect was stronger in Cravina, where the species richness reduced to half, compared with Macaco Branco, suggesting that an agricultural matrix enhances the edge effect. The current study therefore provides further evidence supporting the findings of Paciencia & Prado (2004), Silva et al (2011), andSilva et al (2014), indicating that ferns and lycophytes are potentially vulnerable to edge effects.…”

“…This fact is also related to a higher total species of ferns and lycophytes recorded in the Macaco Branco edge compared with Cravina, indicating that the isolation edges influence the species richness and climatic variables in different ways. However, Paciencia & Prado (2004) observed that the amount of proximal edges and relatively open areas does not appear to influence the richness of ferns and lycophytes in Atlantic forest fragments in northeastern Brazil.…”

“…There are also few studies describing how other taxonomic groups, including ferns and lycophytes (Paciencia & Prado 2004;Barros et al 2006;Silva et al 2011;Pereira et al 2014) and fruticose lichens (Esseen & Renhorn 1998) or bryophytes (Baldwin & Bradfield 2007), respond to these effects.…”

“…Different species respond differently to edge effects and the effects themselves do not manifest in exactly the same way at all edges (Paciencia & Prado 2004). At the time of formation of edges and elimination of sensitive species, increased numbers of pioneer species and species tolerant to the climatic conditions of the changed environment are also observed (Laurance et al 1998).…”

“…Certain species in these groups that inhabit the interiors of forests have very narrow ecological amplitude, being practically excluded by the conditions of some microhabitats, and it has been shown that they are highly sensitive to environmental changes (Senna & Kazmirczak 1997) caused by fragmentation. In Brazil, Paciencia & Prado (2004; and Silva et al (2011; conducted comparative analyzes of edges and interiors of rainforests in northeastern Brazil and found that the species richness of ferns and lycophytes was reduced in edges when compared with sites in the forest interior. The edge effect can result in substitution of more sensitive species by those that are more tolerant to the impacts caused by fragmentation, resulting in impoverishment and decharacterization of the local native flora .…”