Orchidaceae em ecossistemas de campinaranas: relações entre os padrões de distribuição e composição de espécies epífitas com características de Aldina heterophylla

Abstract

Vascular epiphytes, especially the representatives of Orchidaceae, are referred as abundant and diversified in the Amazonian white-sand ecosystems (campinaranas). However, little is known about the influence of phrorophytes structural characteristics and the mechanisms that structure species composition for this environment. This work aimed to inventory the Orchidaceae flora present in campinaranas of the Uatumã Sustainable Development Reserve, and evaluate how patterns of richness, abundance and composition of epiphytic species can be influenced by host trees characteristics. To assess these questions, the host tree Aldina heterophylla (Leguminosae) was used as a model. Sixty individuals of this host tree were selected and all orchids occurring were collected and identified. Tree age was calculated using a mathematical non-linear regression model developed for A. heterophylla. Measurements of height, crown volume and photosynthetic active radiation (PAR) were taken. From a total of 60 species and 30 genera of Orchidaceae found in the studied campinaranas, 36 epiphytic species and 3.401 individuals occurred on A. heterophylla. Positive correlations were found between the age of host trees and patterns of richness and abundance of epiphytic orchids. In addition, it has been found that structural characteristics are altered as host trees get older and the canopy surface is the main variable influenced by the age of the trees. The composition of epiphytic orchids is structured by the nested pattern of species, where older A. heterophylla individuals contain more complex communities of epiphytic orchids, and young individuals of A. heterophylla comprise subgroups of the epiphytic communities of older trees.