Capões naturais de florestas nebulares: efeito de borda e diversidade funcional

Abstract

Forest patches with natural edges (e.g.: capões de mata) are areas formed naturally in the middle of the grassland matrix, having different sizes and shapes and with an abrupt transition to the open vegetation. Despite being found in several tropical mountainous regions, little is known about the structure of these ecosystems. However, they can produce important study models for understanding various ecological issues, especially how the edge effect shapes plant communities, regardless of habitat loss. Thus, in two articles of the present thesis, we sought to explore the main structural and functional patterns of these areas. The interpretation of articles is based on a data set of 5495 trees from ten cloud forest patches surrounded by highland grasslands in southeastern Brazil. In each patch, we established five plots right on the edge and five randomly distributed over the forest interior. In the first article we explored how forest edges and interiors differ in soil characteristics, structure and diversity metrics and the extent to which these differences are related to forest size and shape. In this sense, we show that the edge and interior are contrasting habitats for most of the evaluated community attributes. And many of those differences were similar or even harsher than the ones found for recently created anthropogenic forest fragment. In addition, we found that the shape and size patches are important drivers of tree structure and diversity and that patches with smaller sizes and irregular shapes have a greater edge effect. In the second article, we evaluated how forest edges and interiors differ in traits and functional diversity and how the inclusion of intraspecific variation of functional traits can influence the assessment of ecological patterns existing in those habitats. Therefore, we showed that the edge and interior have individuals with distinct functional traits, however, that alleviate the inherent stress of each habitat. The edge was also proved to be a more selective habitat in terms of range of functional traits, which reflected in less functional diversity. Finally, we show that the statistically significant differences between habitats, in relation to traits and functional diversity, were better observed with the inclusion of intraspecific variation, therefore, neglecting this variation in functional diversity studies can result in misinterpretations about ecological patterns.