Tree Functional Group Richness and Landscape Structure in a Brazilian Tropical Fragmented Landscape

Abstract

This study explores the relation between landscape structure and tree species richness in a tropical area suffering deforestation since the second half of the 19th century. Three different null hypotheses were tested: (1) there is no relationship between landscape structure and tree species diversity present in fragments because the process of fragmentation in these landscapes is too recent to result in tree species extinction; (2) species characteristics do not influence the relationship between tree richness and landscape structure; (3) scale of analysis does not influence the relationship between tree richness and landscape structure. I studied 11 fragments of mesophytic semideciduous forest occurring along the Jacaré-Pepira river (southeast Brazil). From a classified Thematic Mapper image, the landscape structure was quantified using parameters of fragment structure, forest arrangement, landscape complexity, and landscape composition. To investigate the influence of scale over tree species richness, forest and landscape parameters were evaluated around the studied fragments for three different landscape extents. Each forest fragment community was divided into functional groups according to species dispersal capability and shade tolerance, to distinguish possible differences in landscape perception. The relationships between landscape and community parameters were evaluated with regression and discriminant analyses. Results showed significant relations between landscape parameters and species diversity. The nature of these relations changed according to the group and to the landscape extent considered, supporting the view that species perceive the landscape structure differently. The influence of landscape appears to be stronger for shade-tolerant, zoochorous, and barochorous species. Shade-tolerant species were particularly influenced by the fragment structure (connectivity). Zoochorous species were particularly sensitive to landscape parameters at broad scales, whereas barochorous species responded mainly to landscape structure at fine scales. These results attest to an influence of the present landscape structure on the tree community, although the time lag of extinction occurring for longlived trees may be longer than one century. Furthermore, results showed that boundary complexity and fragment connectivity were the most important parameters of landscape linked to the functional group richness and to total diversity, attesting to the importance of the matrix structure in the relationships between landscape and fragmented communities.

Isolated trees with high crown coverage and densities increase pasture seed rain

“…Additionally, plants growing in pastures will increase animal and seed movements and therefore improve the structural and functional connectivity of those fragmented habitats (Bennett et al 1994;Forman 1995;Wunderle 1997;Metzger 2000;Godefroid & Koedam 2003), accelerating plant succession (Peña-Domene et al 2014).…”

Uso De Geotecnologias Para O Estabelecimento De Áreas Para Corredores De Biodiversidade

“…Assim, os valores de IC próximos de 1 indicam fragmentos com tendência circular e, à medida que esse valor se torna menor, o fragmento apresenta-se com tendência mais alongada, ou seja, fragmentos vulneráveis ao efeito de borda tendem a ter baixo valor de IC, estando Figura 2 -Carta de declividade com classes de acordo com Lepsch et al (1991), identificando os limites para mecanização dos solos e, assim, a exploração agrícola competitiva no Município de São Gabriel do Oeste, Mato Grosso do Sul. Lepsch et al (1991) (METZGER, 2000).…”

Aspectos comparativos das comunidades de aranhas (Araneae) em dois remanescentes de Mata Atlântica do Estado da Bahia, Brasil

“…O número de espécies que um fragmento pode suportar, e suas respectivas taxas de extinção, dependem do seu tamanho, estrutura do habitat e povoamento (MacArthur & Whitmore 1979), além do grau de isolamento, tipo de vizinhança, histórico de perturbações (Viana & Pinheiro 1998) e conectividade (Metzger 2000). Estes remanescentes são ainda pouco conhecidas, pois os inventários, mesmo que rápidos, são quase inexistentes para várias regiões (Vieira 2003), exigindo o desenvolvimento de estratégias para conservação, bem como a recuperação de áreas degradadas (Conroy & Noon 1996).…”

“…Os efeitos da fragmentação vêm sendo usualmente analisados a partir de estudos de ecologia de comunidades em remanescentes com diferentes características espaciais (Kelt 2000, Metzger 2000, Collinge & Palmer 2002, SteffanDewenter 2003, podendo ser avaliados em nível biótico -por meio de mudanças na estrutura e dinâmica das comunidades vegetais, na diversidade e abundância da fauna e nas interações entre ambas (Murcia 1995) -e abiótico, que são efeitos mais facilmente perceptíveis e quantificáveis, como o aumento da temperatura, redução da umidade relativa do ar e retenção da precipitação (Kapos 1989). Contudo, esses estudos ocorrem em diferentes áreas ou têm curta duração.…”