The ecology of vascular epiphytes on a Ficus L. host (Moraceae) in a Peruvian cloud forest

A total of 190 holoepiphytic and 5 hemiepiphytic vascular plant species were collected from the canopy and the trunk of an emergent Ficus L. species host that is common to a Peruvian cloud forest. One hundred and fourteen of the vascular epiphyte species were orchids. A large majority of the vascular species were rare in occurrence. Vascular epiphyte diversity and density was highest in the outer canopy zone of the host crown. In the inner canopy zone there was a dearth of epiphytes, attributed to a high rate of epiphyte slumping on the smooth-barked branches. The trunk had a different suit of species to those found in the canopy. During the wet season, the thickening of epiphytic matter in the outer canopy zone appeared to contribute to a large amelioration of daytime and nocturnal temperatures through evaporation and heat retention respectively. Nocturnal temperatures were highest in the outer canopy zone, and were lowest on the forest floor. The latter was attributed to the downward flow of the product of radiative cooling as a result of the heterogeneous canopy on the steep slope. Epiphyte clumps appear to slump before competition causes the loss of early successional species. Some species showed a preference for more shaded epiphyte clumps and many were more frequent on smaller branch diameters. Most species showed a moderately high niche overlap with a large number of other species, which suggested a high degree of species coexistence. Epiphyte slumping is suggested to be the major driving mechanism for the maintenance of non-equilibrium in the community. Aspects of the phenologies of epiphytes, age-structure of the community and high environmental variation could be other mechanisms for the maintenance of a high degree of species coexistence.