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.

These data demonstrate that variation in leaf size is associated with major changes in within-leaf support investments and in large modifications in integrated leaf chemical and structural characteristics. These size-dependent alterations can importantly affect general leaf structure vs. function scaling relationships. These data further demonstrate important life-form effects on and climatic differentiation in foliage support costs.

Summary• The implications of extensive variation in leaf size for biomass distribution between physiological and support tissues and for overall leaf physiological activity are poorly understood. Here, we tested the hypotheses that increases in leaf size result in enhanced whole-plant support investments, especially in compound-leaved species, and that accumulation of support tissues reduces average leaf nitrogen (N) content per unit dry mass ( N M ), a proxy for photosynthetic capacity.• Leaf biomass partitioning among the lamina, mid-rib and petiole, and whole-plant investments in leaf support (within-leaf and stem) were studied in 33 simple-leaved and 11 compound-leaved species.• Support investments in mid-ribs and petioles increased with leaf size similarly in simple leaves and leaflets of compound leaves, but the overall support mass fraction within leaves was larger in compound-leaved species as a result of prominent rachises. Within-leaf and within-plant support mass investments were negatively correlated. Therefore, the total plant support fraction was independent of leaf size and lamina dissection. Because of the lower N M of support biomass, the difference in N M between the entire leaf and the photosynthetic lamina increased with leaf size.• We conclude that whole-plant support costs are weakly size-dependent, but accumulation of support structures within the leaf decreases whole-leaf average N M , potentially reducing the integrated photosynthetic activity of larger leaves.

CABI:20153174020Understanding how plants are constructed - i.e., how key size dimensions and the amount of mass invested in different tissues varies among individuals - is essential for modeling plant growth, carbon stocks, and energy fluxes in the terrestrial biosphere. Allocation patterns can differ through ontogeny, but also among coexisting species and among species adapted to different environments. While a variety of models dealing with biomass allocation exist, we lack a synthetic understanding of the underlying processes. This is partly due to the lack of suitable data sets for validating and parameterizing models. To that end, we present the Biomass And Allometry Database (BAAD) for woody plants. The BAAD contains 259634 measurements collected in 176 different studies, from 21084 individuals across 678 species. Most of these data come from existing publications. However, raw data were rarely made public at the time of publication. Thus, the BAAD contains data from different studies, transformed into standard units and variable names. The transformations were achieved using a common workflow for all raw data files. Other features that distinguish the BAAD are: (i) measurements were for individual plants rather than stand averages; (ii) individuals spanning a range of sizes were measured; (iii) plants from 0.01-100 m in height were included; and (iv) biomass was estimated directly, i.e., not indirectly via allometric equations (except in very large trees where biomass was estimated from detailed sub-sampling). We included both wild and artificially grown plants. The data set contains the following size metrics: total leaf area; area of stem cross-section including sapwood, heartwood, and bark; height of plant and crown base, crown area, and surface area; and the dry mass of leaf, stem, branches, sapwood, heartwood, bark, coarse roots, and fine root tissues. We also report other properties of individuals (age, leaf size, leaf mass per area, wood density, nitrogen content of leaves and wood), as well as information about the growing environment (location, light, experimental treatment, vegetation type) where available. It is our hope that making these data available will improve our ability to understand plant growth, ecosystem dynamics, and carbon cycling in the world's vegetation

Summary 1.Plants encounter a variety of light and nutrient availabilities during succession. However, there is an ongoing debate to which extent light-dependent structural and physiological plasticity is associated with species shade tolerance. 2. Seedlings of five species, Betula pubescens Ehrh., B. pendula Roth, Populus tremula L., Quercus robur L. and Acer platanoides L. (from most intolerant to most shade-tolerant), were grown at four different light and nutrient availabilities to test the hypotheses that intolerant species have higher physiological and tolerant species higher structural plasticity to light and also that there is an overall increase in plasticity with increasing nutrient availability. Two replicate experiments in different years were conducted. Plasticity was characterized by four estimates: (1) the range of variation of the components of relative growth rate (RGR), leaf area ratio (LAR) and net assimilation rate (NAR) (RGR = LAR·NAR) at common RGR; (2) average standardized slopes of physiological (RGR, NAR, i.e. physiological plasticity, Π P ) and structural (LAR, leaf dry mass per unit area, biomass allocation traits, i.e. structural plasticity, Π S ) traits vs. irradiance relationships; (3) standardized difference of plant traits measured at low to medium irradiance; (4) coefficient of variation across different irradiance treatments. 3. Plant growth was more strongly associated with NAR than with structural traits, but shade-intolerant species had a greater range of variation in both NAR and LAR at a common RGR. RGR, NAR and structural characteristics also responded more strongly to increases in irradiance in shade-intolerant species, but at low irradiance RGR and NAR were similar among all species. Owing to higher biomass fraction in leaves, the intolerant species produced less woody biomass. In nonfertilized plants, both Π P and Π S were negatively associated with shade tolerance. The plasticity was enhanced by nutrient addition, but the nutrient-dependent enhancement in plasticity was greater in more tolerant species. Therefore, differences in plasticity among species of varying tolerance were lower at higher nutrient availability. 4. Our study does not support the hypothesis of a trade-off between structural and physiological plasticity. Shade-tolerant species are generally less plastic than intolerant species, but increases in nutrient availability during succession reduce the differences in plasticity. Despite similar RGR in low light, first-year seedlings of shade-tolerant species produce more woody biomass, favouring survival and growth in subsequent years.