The processes and interactions that occur within natural ecosystems determine the ecosystem functioning, which may be described by nutrient cycling, energy flow, and carbon storage, for instance. One way to evaluate ecosystem functioning is by examining the functional traits of the plants from these ecosystems. Functional traits are measurable features that influence the individual performance, providing insights into how they contribute to ecosystem functioning. When selecting functional traits to evaluate ecosystem functioning, it is important to consider specific traits linked to each function. By using a literature review, we assessed the state of the art on the knowledge regarding the relationship between plant functional traits (in terms of functional diversity and dominance) and productivity, as a proxy for ecosystem processes. We conducted this evaluation on forest and grassland ecosystems, across tropical and temperate regions. Our research has revealed that the strength of the relationship depends on the specific functional traits considered when evaluating productivity, and there is little consistency among the traits used in the different studies. Our chapter sheds light on the significance of traits in understanding productivity and also emphasizes the necessity for further research to paint a more comprehensive and detailed picture.