Large diameters and tree bark physical attributes drive vascular epiphyte-phorophyte relationships in Amazonian black-water floodplain forest

Abstract

Understanding the interactive relationships between organisms is key to understanding community structure and planning appropriate conservation measures. Even more so for plant-plant interactions, which are poorly understood. We studied the vascular epiphyte community and its interactions with the tree community (phorophytes) in Amazonian black-water floodplain forests (igapó), analyzing 58 floristic inventory plots located along a 517 km stretch of the Brazilian Negro River, in the Central Amazon. The vascular epiphytes and trees were identified and quantified, and the physical attributes of the bark were measured, as well as the diameter at breast height (DBH) of the tree species. A total of 2746 trees ≥ 10 cm DBH were inventoried, of which 969 were phorophytes (35.29%), hosting 4692 individuals of epiphytic species, belonging to 17 families 50 genera, and 106 species. Pouteria elegans was the most abundant phorophyte, however, Aldina latifolia showed proportionally higher richness and abundance of epiphytes. Codonanthopsis crassifolia was the epiphyte that colonized most of the phorophytes and showed the highest Epiphytic Importance Value (EIV). The average values for thickness, saturated weight, water retention capacity, and diameter were significantly higher in the tree species that housed vascular epiphytes. In addition, the vascular epiphyte richness (R²m = 0.32; R²c = 0.41) and abundance (R²m = 0.36; R²c = 0.90) were strongly influenced by larger diameters of phorophytes and their saturated bark weight. Our results confirm the importance of phorophyte size (DBH) for epiphyte colonization, present the most complete epiphyte list of Amazonian black-water floodplain forests and provide evidence that physical attributes of tree bark drive the structure of vascular epiphyte-phorophyte interactions.