Journal of Tropical Ecology (2006) 22:705–717. Copyright © 2006 Cambridge University Press doi:10.1017/S0266467406003580 Printed in the United Kingdom Recovery and succession of epiphytes in upper Amazonian fallows Ana-Maria Benavides, Jan H. D. Wolf and Joost F. Duivenvoorden 1 Institute for Biodiversity and Ecosystem Dynamics (IBED), Universiteit van Amsterdam, Kruislaan 318, 1098 SM Amsterdam, The Netherlands (Accepted 21 July 2006) Abstract: The species richness, number of plants, biomass, and species composition of holo- and hemi-epiphytes were recorded in fifty-six 0.04-ha plots, distributed over forest fallows of 2–30 y old and mature forests in lowland Amazonia (Amacayacu National Park, Colombia). A total of 9190 epiphytic plants representing 162 species were recorded on 4277 phorophytes. Seventy species were classified as holo-epiphyte and 85 as hemi-epiphyte. Aroids were most diverse (58 species) and represented 76% of the total recorded biomass. Anemochory was more dominant among holo-epiphytes and zoochory among hemi-epiphytes. The species richness, density and biomass of both holo- and hemi-epiphytes increased significantly from young fallows to old fallows and mature forests. Hemi-epiphytes had greater density and biomass than holo-epiphytes. In canonical ordination, forest age did not relate to the species composition of holo-epiphytes. However, for hemi-epiphytes, the age effect was significant, suggesting that species turnover takes place in the ageing fallows. Key Words: Araceae, canopy, Colombia, dispersal, diversity, hemi-epiphytes, holo-epiphytes, tropical rain forest, secondary forest INTRODUCTION Epiphytic plants are a conspicuous component of mature tropical rain forest (Gentry & Dodson 1987). In Amazonia, epiphytes seem to contribute more to the total plant diversity than previously thought (Benavides et al. 2005). Little is known, however, about epiphyte proliferation in disturbed forests. During forest succession, epiphyte species may respond to changes in the environmental conditions, associated with the changing structure of the forest (Barthlott et al. 2001, Cascante-Mar´ ın 2006, Merwin et al. 2003, Wolf 2005). For example, it has been shown that during forest succession drought-tolerant epiphyte species are replaced by species that appear to be better adapted to a more humid microclimate (Barthlott et al. 2001, Wolf & Flamenco-S. 2006). Slow invasions of epiphytes may also influence the successional development of epiphyte communities. In tree plantations fewer epiphytes were found compared with the surrounding forest (Catling et al. 1986, Madison 1979, Merwin et al. 2003). Old cyclically clear-cut oak coppices in southern Mexico supported fewer epiphytes compared with oak forests of similar structure 1 Corresponding author. Email: duivenvoorden@science.uva.nl that were never clear-cut, providing evidence for dispersal limitation (Wolf 2005). Within forests, the clumped growth of seedlings around mother plants and field experi- ments also point at dispersal limitation, at least for wind- dispersed epiphytes (Ackerman et al. 1996, Cascante- Mar´ ın 2006, van Dunn´ e 2001). Wind-dispersed orchids, bromeliads and ferns may find establishment problematic under frequent downpours in the perhumid Amazonian forest (Wolf & Flamenco-S. 2003). Several studies in upper Amazonia report a preponderance of hemi- epiphytic aroids (Benavides et al. 2005, Leimbeck & Balslev 2001), which are dispersed by animals. This study aimed to explore successional patterns for holo- and hemi-epiphytes in fallows of 2–30 y old and mature forests, in a wet Amazonian area. Holo-epiphytes by definition (Benzing 1987) do not root in the soil, and their settlement in the fallows is largely dependent on dispersal. We assume that the increasing branch area in the expanding canopies in developing fallows yields a growing supply of fresh substrate allowing a more or less continuous arrival of new holo-epiphyte species. We hypothesize that because of this condition the patterns in holo-epiphyte composition are largely independent of the degree of fallow development. In contrast, most hemi-epiphytes depend both on the soil for rooting and trunks for settlement and anchoring. For these epiphytes, therefore, we hypothesize that the availability of substrate