In the tropical montane regions of Monteverde, Costa Rica, epiphytes are important components of the structural, compositional, and functional complexity of these forests. Epiphytes and their accompanying canopy soils likely function as keystone elements in wet forests, as they intercept, retain, and circulate water and nutrients from atmospheric sources. Epiphytic communities have been considered to function as keystone organisms in wet forests, as they intercept, retain, and circulate water and nutrients from atmospheric sources that might otherwise be unavailable to forest communities. Epiphytes reach their highest abundance and diversity in the tropical montane cloud forest (TMCF), where cloud immersion and relative humidity are high. We investigated whether epiphytic biomass, taxon richness, and community composition differed across two gradients at two spatial scales—1) an elevational gradient, spanning premontane rain forests to montane cloud forests, and 2) a within-tree gradient, from the inner to outer canopy. From three canopy trees at each of our six sites, we sampled epiphyte mats and separated them to species and morphospecies.
Epiphytic abundance of taxa differed significantly with respect to elevation and their position on the branch. There was a significant increase in epiphyte taxon richness with respect to elevation and site. Community composition also significantly differed among sites along the elevation gradient. Similar to previous studies, we found that the greatest taxon richness and abundance from canopy branches was at our highest elevation montane sites, and we found greatest abundance of taxon richness and mass from the inner to outer locations on canopy branches. This combination of spatial scales allowed us to see patterns in taxa among branch positions in addition to across elevation, however, no previous studies have combined this larger scale assessment with finer spatial scales to find out how these communities differ within sites and within trees. These results identify a need to conserve epiphyte communities across multiple spatial gradients and scales both throughout the landscape—at multiple elevations, and at a smaller scale within and among trees.