Forest canopies play a crucial role in structuring communities of vascular epiphytes by providing substrate for colonization, by locally varying microclimate, and by causing epiphyte mortality due to branch or tree fall. However, as field studies in the three-dimensional habitat of epiphytes are generally challenging, our understanding of how forest structure and dynamics influence the structure and dynamics of epiphyte communities is scarce. Mechanistic models can improve our understanding of epiphyte community dynamics. We present such a model that couples dispersal, growth, and mortality of individual epiphytes with substrate dynamics, obtained from a three-dimensional functional-structural forest model, allowing the study of forest-epiphyte interactions. After validating the epiphyte model with independent field data, we performed several theoretical simulation experiments to assess how (1) differences in natural forest dynamics, (2) selective logging, and (3) forest fragmentation could influence the long-term dynamics of epiphyte communities. The proportion of arboreal substrate occupied by epiphytes (i.e. saturation level) was tightly linked with forest dynamics and increased with decreasing forest turnover rates. While species richness was, in general, negatively correlated with forest turnover rates, low species numbers in forests with very low turnover rates were due to competitive exclusion when epiphyte communities became saturated. Logging had a negative impact on epiphyte communities, potentially leading to a near-complete extirpation of epiphytes when the simulated target diameters fell below a threshold. Fragment size had no effect on epiphyte abundance and saturation level but correlated positively with species numbers. Synthesis: The presented model is a first step towards studying the dynamic forest-epiphyte interactions in an agent-based modelling framework. Our study suggests forest dynamics as key factor in controlling epiphyte communities. Thus, both natural and human-induced changes in forest dynamics, e.g. increased mortality rates or the loss of large trees, pose challenges for epiphyte conservation.

These epiphyte data were collected in Panama and Ecuador. In Panama, an area of ca. 0.9 ha was sampled using a gondola attached to a construction crane. In Ecuador, an area of 25x40 m was sampled using single rope climbing techniques. For each individual epiphyte in these areas, the x, y, and z position (i.e., the height above ground) was identified. If possible, individuals were identified to the species level. In Ecuador, the total plant height was measured. In Panama, the leaf size (for Orchids: the stem length) was measured.

Panama

Field site - San Lorenzo, Panama

Reference - Zotz, G., Schultz, S., 2008. The vascular epiphytes of a lowland forest in Panama - species composition and spatial structure. Plant Ecol. 195, 131-141.

Data use - Data are released into the public domain under a Creative Commons Zero license waiver. When you use the data in your publication, you should cite the reference given above. If the data set is a major part of the data analyzed in your study, you may consider inviting the data holder as collaborator.

Description of columns

individualID: A unique identifier for each individual epiphyte

speciesCode: A unique six-digit code for each epiphyte species. For all individuals that could only be identified to the family level, the family name is provided (e.g. Orchidaceae, Ferns, Araceae). The few individuals that could not be identified to the family level are marked as “None”.

X: X-position in cm (relative to a reference point)

Y: Y-position in cm (relative to a reference point)

Z: Z-position in cm (height above ground)

size: Length of the longest leaf. For orchids, the maximum stem length was measured. Unit: cm.

lifeForm: Holoepiphyte, Hemiepiphyte, or nomadic vine

Ecuador

Field site – Tiputini Biodiversity Station, Ecuador

Reference – Kreft, H., N. Koster, W. Kuper, J. Nieder, Barthlott, W., 2004. Diversity and biogeography of vascular epiphytes in Western Amazonia, Yasuni, Ecuador. Journal of Biogeography 31,1463-1476.

Data use - Data are released into the public domain under a Creative Commons Zero license waiver. When you use the data in your publication, you should cite the reference given above. If the data set is a major part of the data analyzed in your study, you may consider inviting the data holder as collaborator.

Description of columns

individualID: A unique identifier for each individual epiphyte

speciesID: A unique identifier for each epiphyte species. All individuals that could not be identified to the species level are marked as “NA”.

X: X-position in cm (relative to a reference point)

Y: Y-position in cm (relative to a reference point)

Z: Z-position in cm (height above ground)

plantHeight: Height of the individual in cm