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.

31Question: Climate change will likely modify patterns of precipitation, with an expected increase of 32 intra-annual variability and increased frequency and magnitude of extreme events. The 33Mediterranean area is expected to be very sensitive to such events as water availability is already 34 limited. However, the effect of precipitation variability on ecosystem services, such as plant 35 productivity, is widely unknown. 36What is the short-term effect of an experimental precipitation gradient on the above ground net

Biogeographical units are widely adopted in ecological research and nature conservation management, even though biogeographical regionalisation is still under scientific debate. The European Environment Agency provided an official map of the European Biogeographical Regions (EBRs), which contains the official boundaries used in the Habitats and Birds Directives. However, these boundaries bisect cells in the official EU 10 km × 10 km grid used for many purposes, including reporting species and habitat data, meaning that 6881 cells overlap two or more regions. Therefore, superimposing the EBRs vector map over the grid creates ambiguities in associating some cells with European Biogeographical Regions. To provide an operational tool to unambiguously define the boundaries of the eleven European Biogeographical Regions, we provide a specifically developed raster map of Grid-Based European Biogeographical Regions (GB-EBRs). In this new map, the borders of the EBRs are reshaped to coherently match the standard European 10 km × 10 km grid imposed for reporting tasks by Article 17 of the Habitats Directive and used for many other datasets. We assign each cell to the EBR with the largest area within the cell.

40The study of plant trait-environment links is rarely focused on traits that inform on space occupancy 41 and resprouting (both affecting plant persistence), especially in forest understories. Traits that can 42 effectively capture such key functions are associated with clonality and bud banks. We hypothesized 43 that: 1) climate is the main driver of clonal and bud bank traits, 2) traits related to space occupancy 44 (e.g., greater lateral spread) are more important in more mesic, richer soils forests, and 3) traits 45 related to resprouting ability (e.g., larger bud bank) are more important in more intensively and 46 recently managed forests. We addressed these hypotheses by analysing a unique dataset that is 47 statistically representative of Italian forests heterogeneity and includes three biogeographic regions 48 (Alpine, Continental, Mediterranean). We recorded data for sixteen climatic, soil and management 49 variables. We calculated community weighted mean (CWM) values of seven clonal and bud bank 50 traits for the forest understory vegetation. We used i) redundancy analysis to assess trait-51 environment relations, and ii) variance partitioning analyses to identifying the relative role of 52 different groups of abiotic variables on CWM variation of all traits combined together, as well as 53 clonal and bud bank traits taken separately. Climate alone had a pervasive effect in determining 54 patterns of clonal and bud bank traits in Italian forest understories, mainly related to the effects of 55 temperature extremes and seasonality. Unexpectedly, soil and management factors alone showed 56 marginal effects on clonal and bud bank traits. However, soil features influenced trait patterns when 57 joined with climate. Our results confirmed that, at the biogeographic scale, climate played a lion-58 share role in determining persistence-related traits of forest-floor plants. At the local-scale, other 59 interplaying factors (e.g., management, soil variables) may come into play in shaping patterns of the 60 studied plant traits. This study stressed the importance of examining functional trait patterns along 61 complex environmental gradients. 62 63 64