Quais são os determinantes da comunidade de hemiepífitas em uma floresta do extremo nordeste da amazônia? Efeitos do tamanho do hospedeiro, solo e estrutura da floresta

Abstract

Hemiepiphytes are a group of plants with a wide distribution in the Neotropics, where many ecological aspects are still unknown. The main objective of this study was to analyze the determinants of the hemiepiphytic community in a forest in the extreme northeast of Amazonia, Brazil. Individuals of hemiepiphytes were recorded in all host trees (phorophytes) with DBH ≥1 cm found in 110 circular subplots (6m of radius) distributed in 11 1-ha plots of terra firme forest. Gradients of soil (texture and fertility) and forest structure (tree size and tree size-density distribution) were used as predictors for hemiepiphytic diversity and composition. We found 4878 individuals hemiepiphytes representing 50 species, 11 genera and 7 families distributed in 3385 phorophyte trees (38.9% of the trees total survey). The family Araceae represented 84% of the species and 88.5% of all individuals of hemiepiphytes. Linear mixed-effect models showed that richness and diversity of hemiepiphytes was greater in larger phorophytes, with no soil influence detected. Composition of hemiepiphytes changed significantly along the gradient of host size and the soil texture. Beta diversity, as well as the contribution of species turnover and community heterogeneity, decreased along the gradient of host size and forest structure (represented by tree size-density distributions), evidencing a convergence to higher similarity and homogeneity of hemiepiphytic communities in larger phorophytes and forest stands with a higher proportion of larger trees.Tree host size and forest structure were significant predictors of hemiepiphytic community properties. Soil texture was an important predictor of hemiepiphytes composition, indicating that soil type may act a filter, mainly for nomadic vines which are still connected to the soil in early stages of their life-cycle. Higher alpha diversity was found on larger phorophytes probably due to more availability of substrate and time for hemiepiphytes colonization. However, lower beta diversity, species turnover and heterogeneity suggests that hemiepiphytic communities reach a climax with higher species similarity on larger trees and in mature forest stands