Responses of Vascular Epiphytes To Branch-fall Gap Formation in Clusia Trees in a Montane Rain Forest

Abstract

The vascular epiphyte community in Clusia trees in the elfin forest of the Monteverde Cloud Forest Reserve, Costa Rica, was monitored for one year to evaluate responses to branch-fall gap formation. Plots (10 X 30 cm) were established on inner crown branches of Clusia host trees, and artificial branch falls were created over a subset by removing branches 3-5 cm diam. The vascular epiphyte community changed little in response to gap formation, despite a high turnover of individual plants. Branch-fall gap formation did not affect epiphyte density, percent cover, species richness, the Shannon-Weiner diversity index, or Simpson's equitability index for the epiphyte community. Only weakly significant (P = 0.15) effects of branch-fall gap formation on the population dynamics of a few species were detected, with gap formation possibly favoring Blakea chlorantha and negatively affecting Burmeistera spp., Clusia sp., and Grammitis zurquina. The 12 most common species in the plots did not demonstrate other effects of branchfall gap formation. Although more extreme changes in exposure, such as those caused by loss of neighboring trees, may affect composition and dynamics of a vascular epiphyte community, we conclude that canopy gaps caused by loss of smaller branches in Clusia crowns have little impact.