Phenotypic traits and their associated trade-offs have been shown to have globally consistent effects on individual plant physiological functions 1-3 , but how these effects scale up to influence competition, a key driver of community assembly in terrestrial vegetation, has remained unclear 4 . Here we use growth data from more than 3 million trees in over 140,000 plots across the world to show how three key functional traits-wood density, specific leaf area and maximum height-consistently influence competitive interactions. Fast maximum growth of a species was correlated negatively with its wood density in all biomes, and positively with its specific leaf area in most biomes. Low wood density was also correlated with a low ability to tolerate competition and a low competitive effect on neighbours, while high specific leaf area was correlated with a low competitive effect. Thus, traits generate trade-offs between performance with competition versus performance without competition, a fundamental ingredient in the classical hypothesis that the coexistence of plant species is enabled via differentiation in their successional strategies 5 . Competition within species was stronger than between species, but an increase in trait dissimilarity between species had little influence in weakening competition. No benefit of dissimilarity was detected for specific leaf area or wood density, and only a weak benefit for maximum height. Our traitbased approach to modelling competition makes generalization possible across the forest ecosystems of the world and their highly diverse species composition.Phenotypic traits are considered fundamental drivers of community assembly and thus species diversity 1,6 . The effects of traits on individual plant physiologies and functions are increasingly understood, and have been shown to be underpinned by well-known and globally consistent trade-offs 1-3 . For instance, traits such as wood density and specific leaf area capture trade-offs between the construction cost and longevity or strength of wood and leaf tissues 2,3 . By contrast, we still have a limited understanding of how such trait-based trade-offs translate into competitive interactions between species, particularly for long-lived organisms such as trees. Competition is a key filter through which ecological and evolutionary success is determined 4 . A long-standing hypothesis is that the intensity of competition decreases as two species diverge in trait values 7 (trait dissimilarity). The few studies [8][9][10][11][12][13] that have explored links between traits and competition have shown that linkages were more complex than this, as particular trait values may also confer competitive advantage independently from trait dissimilarity 9,13,14 . This distinction is fundamental for species coexistence and the local mixture of traits. If neighbourhood competition is driven mainly by trait dissimilarity, this will favour a wide spread of trait values at a local scale. By contrast, if neighbourhood interactions are mainly driven by the c...

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.

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

Numerous studies have revealed the existence of nonrandom trait distribution patterns as a sign of environmental filtering and/or biotic interactions in a community assembly process. A number of metrics with various algorithms have been used to detect these patterns without any clear guidelines. Although some studies have compared their statistical powers, the differences in performance among the metrics under the conditions close to actual studies are not clear. Therefore, the performances of five metrics of convergence and 16 metrics of divergence under alternative conditions were comparatively analyzed using a suite of simulated communities. We focused particularly on the robustness of the performances to conditions that are often uncertain and uncontrollable in actual studies; e.g., atypical trait distribution patterns stemming from the operation of multiple assembly mechanisms, a scaling of trait-function relationships, and a sufficiency of analyzed traits. Most tested metrics, for either convergence or divergence, had sufficient statistical power to distinguish nonrandom trait distribution patterns without uncertainty. However, the performances of the metrics were considerably influenced by both atypical trait distribution patterns and other uncertainties. Influences from these uncertainties varied among the metrics of different algorithms and their performances were often complementary. Therefore, under the uncertainties of an assembly process, the selection of appropriate metrics and the combined use of complementary metrics are critically important to reliably distinguish nonrandom patterns in a trait distribution. We provide a tentative list of recommended metrics for future studies.

Accurate estimation of tree and forest biomass is key to evaluating forest ecosystem functions and the global carbon cycle. Allometric equations that estimate tree biomass from a set of predictors, such as stem diameter and tree height, are commonly used. Most allometric equations are site specific, usually developed from a small number of trees harvested in a small area, and are either species specific or ignore interspecific differences in allometry. Due to lack of site-specific allometries, local equations are often applied to sites for which they were not originally developed (foreign sites), sometimes leading to large errors in biomass estimates. In this study, we developed generic allometric equations for aboveground biomass and component (stem, branch, leaf, and root) biomass using large, compiled data sets of 1203 harvested trees belonging to 102 species (60 deciduous angiosperm, 32 evergreen angiosperm, and 10 evergreen gymnosperm species) from 70 boreal, temperate, and subtropical natural forests in Japan. The best generic equations provided better biomass estimates than did local equations that were applied to foreign sites. The best generic equations included explanatory variables that represent interspecific differences in allometry in addition to stem diameter, reducing error by 4-12% compared to the generic equations that did not include the interspecific difference. Different explanatory variables were selected for different components. For aboveground and stem biomass, the best generic equations had species-specific wood specific gravity as an explanatory variable. For branch, leaf, and root biomass, the best equations had functional types (deciduous angiosperm, evergreen angiosperm, and evergreen gymnosperm) instead of functional traits (wood specific gravity or leaf mass per area), suggesting importance of other traits in addition to these traits, such as canopy and root architecture. Inclusion of tree height in addition to stem diameter improved the performance of the generic equation only for stem biomass and had no apparent effect on aboveground, branch, leaf, and root biomass at the site level. The development of a generic allometric equation taking account of interspecific differences is an effective approach for accurately estimating aboveground and component biomass in boreal, temperate, and subtropical natural forests.

Summary 1.Tree architecture is a major determinant of performance, such as height growth, light capture, and mechanical stability. Studies both in temperate and tropical forests have shown significant architectural differences associated with adult stature and light demand. 2. However, studies in temperate forests have not been as thorough in examining these relationships with respect to phylogeny and ontogeny, thus preventing a complete understanding of the patterns in temperate forests and limiting comparisons of the relationship between tropical and temperate forests. Therefore, we performed a community-level analysis of the relationship between tree form and ecology in a temperate forest with statistical consideration of phylogeny and ontogeny. 3. The height-diameter relationship throughout tree development was asymptotic in most species. Crown diameter and depth increased allometrically with tree height, with no asymptote. The tree height, crown diameter, and crown depth of small trees were estimated using these relationships and were similar to those reported for tropical species. 4. Taller species had more slender stems at any reference size and narrower crowns at small reference sizes, whereas crown depth was relatively independent of adult stature. Light-wooded species had narrower and shallower crowns at medium to large reference heights. Stem thickness was virtually independent of wood density throughout the size range. 5. Our results support the hypothesis that the architecture of short or shade-tolerant species is optimized for light capture and mechanical stability, whereas that of tall or light-demanding species is optimized for height growth. These relationships generally agree with results from studies in tropical rain forests, although considerable differences exist, and may potentially promote the stable coexistence of the species.

Summary 1.Tree architecture is a major determinant of performance, such as height growth, light capture, and mechanical stability. Studies both in temperate and tropical forests have shown significant architectural differences associated with adult stature and light demand. 2. However, studies in temperate forests have not been as thorough in examining these relationships with respect to phylogeny and ontogeny, thus preventing a complete understanding of the patterns in temperate forests and limiting comparisons of the relationship between tropical and temperate forests. Therefore, we performed a community-level analysis of the relationship between tree form and ecology in a temperate forest with statistical consideration of phylogeny and ontogeny. 3. The height-diameter relationship throughout tree development was asymptotic in most species. Crown diameter and depth increased allometrically with tree height, with no asymptote. The tree height, crown diameter, and crown depth of small trees were estimated using these relationships and were similar to those reported for tropical species. 4. Taller species had more slender stems at any reference size and narrower crowns at small reference sizes, whereas crown depth was relatively independent of adult stature. Light-wooded species had narrower and shallower crowns at medium to large reference heights. Stem thickness was virtually independent of wood density throughout the size range. 5. Our results support the hypothesis that the architecture of short or shade-tolerant species is optimized for light capture and mechanical stability, whereas that of tall or light-demanding species is optimized for height growth. These relationships generally agree with results from studies in tropical rain forests, although considerable differences exist, and may potentially promote the stable coexistence of the species.

1. Environmental control and dispersal limitation are both essential processes in plant community assembly and species distribution. Although numerous studies in the past decade have examined their importance as determinants of community composition, remarkably little is known about interspecific differences in the importance of these two processes. 2. To quantify these interspecific differences, we compared the importance of environmental factors and space as correlates of species distribution among 24 understorey plant species in a Japanese cool-temperate forest by performing variation partitioning at the species level. Specifically, we hypothesized that the importance of environment and space differs among species, and these differences can be partly predicted from the functional traits and ⁄ or phylogenetic identity of each species. 3. The unique contributions of both environment and space were significant in the community-level analysis. However, at the species level, the relative and absolute sizes of the unique contributions of environment and space differed considerably among the 24 species. Environment and space were not necessarily significant variables explaining the distribution of many species. 4. No significant relationships were found between the unique contribution of environment and the four functional traits tested, that is, dispersal mode, seed mass, plant height and specific leaf area among the 24 species. In contrast, the unique contribution of space was significantly larger in species with no dispersal mechanisms than in animal-dispersed species. No significant phylogenetic signal was detected for the unique contribution of environment or space, suggesting that importance of environmental control and dispersal limitation as determinants of species distribution is evolution-arily labile. 5. Synthesis. Our results suggest that the relative and absolute importance of different processes of community assembly (i.e. environmental control and dispersal limitation) differs remarkably among species even within a single community. These interspecific differences may be explained in part by interspecific differences in dispersal mode.