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.

No abstract

Abstract1. In recent years, belowground plant ecology has experienced a booming interest.This has resulted in major advances towards a greater understanding of belowground plant and ecosystem functioning focused on fine roots, mycorrhizal associations and nutrient acquisition.2. Despite this, other important functions (e.g., on-spot persistence, space occupancy, resprouting after biomass removal) exerted by different belowground plant organs (e.g., roots, rhizomes, bulbs) remain largely unexplored.3. Here, we propose a framework providing a comprehensive perspective on the entire set of belowground plant organs and functions. We suggest a compartment-based approach. We identify two major belowground compartments, that is, acquisitive and nonacquisitive, associated with biomass allocation into these functions. Also, we recommend the nonacquisitive compartment to be divided into structural (e.g., functional roles carried out by rhizomes, such as sharing of resources, space occupancy) and nonstructural (e.g., functional roles exerted by carbohydrates reserve affecting resprouting ability, protection against climate adversity) subcompartments. We discuss methodological challenges-and their possible solutions-posed by changes in biomass allocation across growth forms and ontogenetic stages, and in relation to biomass partitioning and turnover. 4. We urge the implementation of methods and approaches considering all the belowground plant compartments. This way, we would make sure that key, yet lessstudied functions would be incorporated into the belowground plant ecology research agenda. The framework has potential to advance the understanding of belowground plant and ecosystem functioning by considering relations and tradeoffs between different plant functions and organs. At last, we identify four major areas where using the proposed compartment-based approach would be particularly important, namely (a) biomass scaling, (b) clonality-resource acquisition relations, (c) linkages between resprouting and changing environmental conditions and (d) carbon sequestration. K E Y W O R D Sacquisitive and nonacquisitive compartments, belowground plant functions, biomass allocation and turnover, buds and carbohydrates storage, growth forms, ontogeny, rhizomes, roots

No abstract

The proposed functional signature concept allows the systematic integration of plant functional traits and phylogeny into the study of endemism hotspots and refugia, but more data on functional traits in these entities are urgently needed. Overcoming this limitation would facilitate rigorous testing of the proposed predictions for the functional signature, advancing the eco-evolutionary understanding of endemism hotspots and refugia.

Dominants are key species shaping ecosystem functioning. Plant dominance is typically 25 assessed on aboveground appearance but aboveground-belowground dominance of 26 individual species may not scale proportionally. This is especially important in biomes 27where most biomass is allocated belowground, and includes areas accounting for >60% 28 of biomes' land cover worldwide.

On-spot persistence, space occupancy, and recovery after damage are key plant functions largely understudied. Traits relevant to these functions are difficult to assess because of their relationships to plant modularity. We suggest that developing collection protocols for these traits is feasible and could facilitate their inclusion in global syntheses.

The theory of island biogeography postulates that size and isolation are key drivers of biodiversity on islands. This theory has been applied not only to true (e.g. oceanic) islands but also to terrestrial island‐like systems (e.g. edaphic islands). Recently, a debate has opened as to whether terrestrial island‐like systems function like true islands. However, identifying the effect of insularity in terrestrial systems is conceptually and methodologically challenging because recognizing species source(s) and measuring isolation is not as straightforward as for true islands. We contribute to the debate by proposing an approach to contextualize the definition of insularity and to identify the role of isolation in terrestrial island‐like systems. To test this approach, we explored the relationship between insularity predictors and specialist species richness of edaphic islands in three systems in Europe (spring fens, mountaintops, and outcrops). We detected that insularity affected specialist richness of edaphic islands through island size and target effect (i.e. an emergent property of islands depending on their isolation and size). As predicted by the Theory of Island Biogeography, species richness decreased with increasing isularity. Given the comprehensiveness and ease of implementation of our approach, we encourage its extension to other island‐like systems.