In order to deal with the generalized losses in biodiversity and its adverse effect on the provision of ecosystem, services, it is critical to understand the mechanisms behind the assemblage and coexistence of species, including the relative effect of environmental and land-use factors, and its feedbacks to ecosystem functioning. There is growing consensus that the quantification of the kind, diversity, and relative abundance of functional traits in biotic communities, collectively defined as functional diversity (FD), can greatly contribute to understanding the assemblage of biodiversity and its effects on ecosystem service assessment and management.The latin word 'Tandem' means 'finally', and refers to a groups of persons or objects working together. The TANDEM (‘Trait diversity: Assemblage of commuNities and their feeDbacks to Ecosystem Multifunctionality’) will join the efforts of several ecologists aiming to reconcile the responses of functional traits to environmental variables with their effects on ecosystem functioning. Using this unified framework, the TANDEM project will address many of the key questions that remain to be solved in order to fully incorporate the functional component of biodiversity into theoretical and applied models of future biodiversity changes. A set of subprojects are considered, ranging from the study of processes shaping species coexistence, the effects of diversity on ecosystems functioning and to the role played by different traits and by phylogenetic differences on the assembly processes of plant communities across environmental and disturbance gradients. The project will address these challenges by merging different aspects from plant ecology (functional, evolutionary and community ecology) with the development of a new set of tools to estimate the functional diversity of biological communities.