Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects.We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives. Geosphere-Biosphere Program (IGBP) and DIVERSITAS, the TRY database (TRY-not an acronym, rather a statement of sentiment; https ://www.try-db.org; Kattge et al., 2011) was proposed with the explicit assignment to improve the availability and accessibility of plant trait data for ecology and earth system sciences. The Max Planck Institute for Biogeochemistry (MPI-BGC) offered to host the database and the different groups joined forces for this community-driven program. Two factors were key to the success of TRY: the support and trust of leaders in the field of functional plant ecology submitting large databases and the long-term funding by the Max Planck Society, the MPI-BGC and the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, which has enabled the continuous development of the TRY database.

Plant species distribution and plant community composition vary along environmental gradients. At the continental scale, climate plays a major role in determining plant distribution, while at the local and regional scales vegetation patterns are more strongly related to edaphic and topographic factors. The projected global warming and alteration of the precipitation regime will influence tree physiology and phenology, and is likely to promote northward migration of tree species. However the influence of soil characteristics on tree species migration is not as well understood. Considering the broad tolerance of most tree species to variations in soil factors, soils should not represent a major constraint for the northward shift of tree species. However, locally or regionally, soil properties may constrain species migration. Thus, while climate change has the potential to induce a northward migration of tree species, local or regional soil properties may hinder their migratory response. These antagonistic forces are likely to slow down potential tree migration in response to climate change. Because tree species respond individualistically to climate variables and soil properties, new tree communities are likely to emerge from climate change.Résumé : La distribution des espèces et la composition des communautés végétales varient le long de gradients environnementaux. À l'échelle continentale, le climat joue un rôle primordial dans la distribution des espèces végétales, alors qu'aux échelles locale et régionale la distribution des espèces est surtout influencée par les variables édaphiques et la topographie. Le réchauffement climatique projeté et l'altération du régime des précipitations sont susceptibles d'influencer la physiologie et la phénologie des arbres, et d'entraîner leur migration vers le nord. Toutefois, l'influence des caractéristiques des sols sur le potentiel migratoire des arbres est peu connue. Puisque la plupart des espèces d'arbres possèdent une grande tolérance aux variations édaphiques, les sols ne devraient pas constituer un obstacle majeur à leur migration vers le nord. Toutefois, localement ou régionalement, les sols pourraient posséder des propriétés qui pourraient restreindre la migration des espèces. Alors que les changements climatiques ont le potentiel de provoquer la migration des espèces vers le nord, localement ou régionalement les propriétés des sols pourraient limiter leur capacité migratoire. Ces forces en opposition pourraient restreindre le potentiel migratoire des arbres en réponse aux changements climatiques. Parce que les espèces d'arbres répondent de manière individuelle aux variables climatiques et aux propriétés des sols, de nouvelles communautés d'arbres pourraient résulter des changements climatiques.