This contribution was funded, in part, by the Inter-American Institute for Global Change Research (IAI) CRN 2015 and SGP-CRA2015, which were supported by US National Science Foundation Grants GEO-0452325 and GEO-1138881. The work was also funded by FONCyT (PICT 20441 and 365), CONICET (PIP 2006-2011 11220080101532), SECYT-Universidad Nacional de Córdoba – Argentina, and the US NSF (DEB-0620652). The authors particularly thank Phil Grime and the UCPE–University of Sheffield, and Mark Westoby and the ARC–NZ Network of Vegetation Function–Macquarie University, for inspiring discussion and development of trait measurement. The authors also thank Marcelo Cabido, William Bond, Paula Tecco, Fernando Casanoves and Bryan Finegan for valuable discussions. The authors thank Diana Abal Solis and Juan Pablo Bellini for assistance with figures and diagrams and Valeria Falczuk for technical assistance in the laboratory. The authors appreciate helpful comments of Adrienne Nicotra, Hans Lambers and one anonymous reviewer, which greatly improved the quality of the manuscript. Many users of the previous handbook gave useful feedback on trait measurements. Finally, we thank plant species around the world for beginning to give away the secrets of their functioning and ecosystem-level impacts.