Branchfall as a Demographic Filter for Epiphyte Communities: Lessons from Forest Floor-Based Sampling

Juliano Sarmento Cabral; Gunnar Petter; Glenda Mendieta-Leiva; Katrin Wagner; Gerhard Zotz; Holger Kreft

doi:10.1371/journal.pone.0128019

Branchfall as a Demographic Filter for Epiphyte Communities: Lessons from Forest Floor-Based Sampling

PLoS One. 2015 Jun 17;10(6):e0128019. doi: 10.1371/journal.pone.0128019. eCollection 2015.

Authors

Juliano Sarmento Cabral¹, Gunnar Petter¹, Glenda Mendieta-Leiva², Katrin Wagner², Gerhard Zotz³, Holger Kreft¹

Affiliations

¹ Biodiversity, Macroecology & Conservation Biogeography Group, Faculty of Forest Sciences and Forest Ecology, University of Göttingen, Göttingen, Germany.
² Functional Ecology of Plants, Department of Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany.
³ Functional Ecology of Plants, Department of Biology and Environmental Sciences, University of Oldenburg, Oldenburg, Germany; Smithsonian Tropical Research Institute, Panama City, Republic of Panama.

Abstract

Local variation in the abundance and richness of vascular epiphytes is often attributed to environmental characteristics such as substrate and microclimate. Less is known, however, about the impacts of tree and branch turnover on epiphyte communities. To address this issue, we surveyed branches and epiphytes found on the forest floor in 96 transects in two forests (Atlantic rainforest in Brazil and Caribbean rainforest in Panama). In the Brazilian forest, we additionally distinguished between edge and core study sites. We quantified branch abundance, epiphyte abundance, richness and proportion of adults to investigate the trends of these variables over branch diameter. Branches <2 cm in diameter comprised >90% of all branches on the forest floor. Abundance and richness of fallen epiphytes per transect were highest in the Brazilian core transects and lowest in the Panamanian transects. The majority of epiphytes on the floor (c. 65%) were found attached to branches. At all three study sites, branch abundance and branch diameter were negatively correlated, whereas epiphyte abundance and richness per branch, as well as the proportion of adults were positively correlated with branch diameter. The relationship between branch diameter and absolute epiphyte abundance or richness differed between study sites, which might be explained by differences in forest structure and dynamics. In the Panamanian forest, epiphytes had been previously inventoried, allowing an evaluation of our surveying method by comparing canopy and forest floor samplings. Individuals found on the forest floor corresponded to 13% of all individuals on branches <10 cm in diameter (including crowns), with abundance, richness and composition trends on forest floor reflecting canopy trends. We argue that forest floor surveys provide useful floristic and, most notably, demographic information particularly on epiphytes occurring on the thinnest branches, which are least accessible. Here, branchfall acts as an important demographic filter structuring epiphyte communities.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Brazil
Forests*
Panama
Plant Stems / metabolism
Rainforest
Trees / classification
Tropical Climate

Grants and funding

J.S.C. acknowledges financial support by a German Research Foundation (DFG) grant (SA-21331). G.P. and H.K. were funded by the DFG Initiative of Excellence Free Floater Program at the University of Göttingen. G.Z., K.W. and G.M.L.´s work in Panama was supported by the DFG (Zo 94/5-1) and the Smithsonian Tropical Research Institute.