Data from: Local and regional determinants of vascular epiphyte mortality in the Andean mountains of Colombia

1. We present the first large-scale assessment of vascular epiphyte
mortality in the neotropics. Our goals were to explore the primary types
of vascular epiphyte death and to identify local and regional determinants
of epiphyte mortality in natural forests located 60 to 2900 m a.s.l. in
the Colombian Andes. 2. Based on two consecutive annual surveys, we
followed the fate of 4247 epiphytes to estimate the epiphyte mortality
rate on 116 host trees at nine sites. A logistic regression analysis for
proportional data with a binomial distribution of the error was applied to
determine the probability of epiphyte death in relation to local and
regional explanatory variables. 3. The overall epiphyte mortality rate was
7.5 ± 1.1% yr−1 (mean ± standard error). Non-mechanical factors, such as
desiccation, accounted for a mortality rate of 1.9 ± 0.3% yr−1. Mechanical
factors, such as falling branches, accounted for a mortality rate of 5.6 ±
1.1% yr−1. According to generalized linear modelling analyses, both local
and regional factors played key roles in determining epiphyte mortality.
The actual evapotranspiration (regional factor) and the mean epiphyte
attachment height (local factor) were both consistently positively
associated with the probability of epiphyte death. Additional variables
identified as possible determinants of the epiphyte mortality were the
temperature seasonality, annual temperature range, the height and number
of branches of the tree, and the abundance of large trees (DBH ≥ 10 cm).
4. Synthesis. The recorded high mortality rate indicates that natural
epiphyte assemblages must be highly dynamic to avoid local extinction of
species. Our study identifies actual evapotranspiration as an important
driver of epiphyte mortality, and we highlight its importance in
determining the fate tropical epiphyte communities may experience if
evapotranspiration increases due to climate change. We hope our study
addresses the paucity of research on non-tree growth forms, typically
ignored in vegetation dynamics, and encourages their inclusion in future
studies that investigate the function of tropical ecosystems.