Abstract. In the Amazon, as well as the Orinoco basin, flooded forests have been classified according to the rivers that flood into Várzea (white water) and Igapó (black water). Furthermore, these river differences have been shown to influence the forest soil composition, so that Várzea is characterized by having nutrient-rich soils while Igapó has nutrient-poor soils. To determine if these differences have driven ecological sorting processes, we evaluated the plant functional diversity of Várzea and Igapó and the influence of external and internal filters on the plant community assembly of each forest. We sampled six functional traits in two, 1 ha plots located in Casanare, Colombia, one in Várzea and the other in Igapó. We found that there is a partial functional differentiation between Várzea and Igapó, and a high functional divergence within each forest. We also observed a greater influence of internal filters on the community assembly of both forest types, compared to external filters. These results contribute to the understanding of community assembly and the expression of functional traits in rich and poor soils, as well as showing the importance of recognizing the functional diversity between and within Várzea and Igapó, despite their low taxonomic diversity.
