While Amazonian forests are extraordinarily diverse, the abundance of trees is skewed strongly towards relatively few ‘hyperdominant’species. In addition to their diversity, Amazonian trees are a key component of the global carbon cycle, assimilating and storing morecarbon than any other ecosystem on Earth. Here we ask, using a unique data set of 530 forest plots, if the functions of storing andproducing woody carbon are concentrated in a small number of tree species, whether the most abundant species also dominate carboncycling, and whether dominant species are characterized by specific functional traits.