Variation in the community hemiepiphytes explaining for phorophyte size or soil, Floresta Nacional de Amapá, northeastern Amazonia , AP, BRAZIL, 2017

We investigate the role of tree (host) size, soil fertility, and recruitment strategy on community variation of two vascular epiphytic functional groups. Based on the distributional analyses of > 4,000 ramets from a host pool of > 3,000 individuals ranging in stem diameters from 1 to 200 cm in a northeastern Amazonian upland forest to test three predictions: 1) Primary hemiepiphytes (PH), due to their direct establishment on hosts are positively affected by host size due to greater longevity, and habitat quality to determine germination success; 2) Nomadic vines (NV), due to their dependence on ground germination, are influenced by edaphic factors particularly in highly weathered soils of lowland Amazonia (e.g., phosphorous); and 3) Compositional convergence increases with tree-size due to direct biotic effects. Our results show that larger hosts (> 30 cm DBH) supported more species for both PH and NV. However, NV occupancy probabilities saturated at significantly smaller stem sizes than those of PH indicating that tree size influences functional group distributions. Soil effects were stronger on NV than PH for smaller hosts classes (<30 cm DBH), whereas no significant differences were detected among functional groups in relation to edaphic changes among larger host size classes. NV abundance increased relative to phosphorus content, and decreased in correlation with soil sum of bases and clay content only for smaller-statured hosts. Finally, compositional convergence of 18 core species representing both functional groups among larger hosts suggests that autogenic processes driven by environmental, and biotic filters influence succession. Synthesis. Maintaining mixed-age class forests in lowland Amazonia to maximize hemiepiphytic community diversity is imperative. Interactions among host size and edaphic factors result from the contrasting ecological requirements at recruitment demonstrating the necessity for further intensive demographic studies of this ecologically dominant component of plant-plant interactions in Amazonia.