Successional forests stages influence the composition and diversity of vascular epiphytes communities from Andean Montane Forests

Vascular epiphytes layer is an important component of the forests; to understand their contribution to the ecosystem, it is imperative to assess the factors which affect their distribution, composition, and diversity. We studied the ecology of vascular epiphytes in Andean Mountain Forests of different successional stages, in a scenario that allowed us to determine some relationships between the composition of the epiphyte community and the tree communities, along with environmental and historic land use gradients. The research design included the sampling of 22 plots with a total of 3248 trees, including tree ferns with DBH ≥10 cm. Each tree was measured and identified to species level and was divided into three vertical strata, recording the diversity and frequency of vascular epiphytes present in each stratum. In these forests, we evaluated the variation of the composition, richness, and density of vascular epiphytes using the ADONIS analysis, evaluating the influence of two factors: the successional stage of the forest community and the tree vertical strata. We then explored which predictor variables, such as climate, spatial correlation, and host tree characteristics, explained the variation in epiphytes, using linear and variance partitioning models. In addition, we determined the preference of epiphytes for host tree species, using indicator tree species of successional stages. For each host tree species, we identified associated vascular epiphytes and their indicator species level was analyzed to determine epiphyte-host species with traits of specialist species. We found that epiphyte species richness and density were significantly higher in older forest communities. Epiphyte density was higher in the upper canopy of the hosts. The climate affected the composition of the epiphytes, while precipitation, elevation, crown height, and basal area significantly explained epiphyte richness and density. Preferential and indifferent epiphytes on indicator host species of intermediate and late succession suggest the existence of complex associations. The age of the forest succession, climatic factors, and certain characteristics of the host species have a major impact on the ecology of vascular epiphytes.