Background/Question/Methods The canopy of temperate rainforests of southern South America is densely covered by epiphytes. However, the importance of large trees as epiphyte substrates and reservoirs for forest biodiversity is still poorly known. We analyzed what proportion of the pool of forest epiphytes used large trees for support, and compared epiphyte diversity of filmy ferns (Hymenophyllaceae) between primary and secondary forest stands. We conducted two types of surveys in Valdivian temperate rain forest of Chiloé Island (41º 50’S), Chile. First, we accessed the canopy using tree-climbing techniques and documented the biomass of epiphytes and species composition of ferns and angiosperms growing on two canopy emergent tree species (>25 m tall), the endemics Eucryphia cordifolia (Cunoniaceae) and Aextoxicon punctatum (Aextoxicaceae). Secondly, we compared species richness and abundance of filmy ferns present in the ground and at the base of trees between old-growth and secondary stands.
Results/Conclusions Each emergent tree supported c.140 kg dry-mass of epiphyte material (60-80% moisture). Roots and dead organic matter composed 70% of epiphyte material, while leaves and fronds represented the remaining 30%. Epiphyte diversity included Hymenophyllum ferns (13 spp.), the hemiepiphyte Raukaua laetevirens (Araliaceae), Fascicularia bicolor (Bromeliaceae), and four other vascular plants. Epiphytic biomass was comparable to epiphyte-rich tropical cloud forests, and represents one of the largest estimates of epiphyte biomass per tree. Epiphyte diversity of emergent trees represents 33% of all vascular epiphytes known for the whole Valdivian ecoregion, and 50% of all filmy ferns described for Chile. In tree bases of old-growth stands, 20% of the area was covered by six species of filmy ferns, generally associated to fallen limbs, while in secondary stands only the 0.2% of the forest soil was covered by four species of filmy ferns. Large trees supported about 50% of the pool of vascular epiphytes, and also trough frequent limb and branch fall, they increase the ground diversity of plant species. Old emergent trees can be important reservoirs of plant diversity at regional level. Future steps of this work include assessing the functional role of epiphyte biodiversity.
Acknowledgements: The Canon National Parks Science Scholars Program, Fondecyt 1050225, Fondap-Fondecyt 1501-0001, Conicyt PDA-24.