Epífitas vasculares em ecossistemas de areia branca da Amazônia (Campinaranas): padrões de estrutura, composição e de distribuição

Abstract

The white sand ecosystems of the Amazon, also known as campinaranas, are distributed over extensive areas of land covering approximately 5% of the Amazon territory. The oligotrophic conditions of the soils, combined with the low water retention capacity, generate a strong filtering effect and selective pressure, resulting in a flora that is structurally and floristically different from that of other Amazonian ecosystems. In recent years, considerable advances in scientific knowledge about these environments have been achieved, however, studies focusing on the epiphytic component are still scarce, which makes it difficult to include this group of plants in conservation strategies and also obscures the understanding of the dynamics itself, structure and functioning of Campinaranas ecosystems. Vascular epiphytes constitute a diverse group of plants, distributed mainly in tropical regions. Environmental variables, such as temperature and precipitation, as well as the structural and compositional conditions of the vegetation, influence the distribution of vascular epiphyte species. Understanding the factors that determine the dynamics and structure of epiphyte communities and the interactions established between epiphytes and phorophytes is one of the crucial points in ecological studies. Thus, the general objective of this thesis was to investigate the structure, composition and distribution of vascular epiphyte communities in five campinarnas areas of the central Amazon and relate the observed patterns with the environmental and structural characteristics of the vegetation. A total of 17,808 epiphytic individuals belonging to 18 families, 60 genera and 118 species were recorded colonizing 486 phorophytic individuals. The results of this study indicate that the intrinsic characteristics of each area and attributes related to the size and identity of the phorophytes are fundamental to defining the distribution and composition of epiphyte species among the areas studied. Networks of interactions between epiphytes and phorophytes indicate that vascular epiphyte communities have a highly nested structure, with low connectance, low modularity and low specialization in the horizontal and vertical gradient, but it is possible to identify a significant pattern of stratification and modularity in vertical distribution of the species. Finally, we identified that epiphyte-phorophyte networks are sensitive to environmental disturbances and that the removal of a single species of generalist phorophyte can result in a considerable loss of interactions, reduce the local diversity of vascular epiphytes and lead the ecosystem to imbalance. Using different approaches, this thesis contributes to expanding knowledge about the flora of vascular plants present in Campinarnas and provides an important tool to support conservation and management strategies for these Amazonian ecosystems.