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Background and Aims The existence of sclerophyllous plants has been considered an adaptive strategy against different environmental stresses. Given that it literally means ‘hard-leaved’, it is essential to quantify the leaf mechanical properties to understand sclerophylly. However, the relative importance of each leaf trait for mechanical properties is not yet well established. Methods Genus Quercus is an excellent system to shed light on this because it minimizes phylogenetic variation while having a wide variation in sclerophylly. We measured leaf anatomical traits and cell wall composition, analysing their relationship with leaf mass per area and leaf mechanical properties in a set of 25 oak species. Key Results The upper epidermis outer wall makes a strong and direct contribution to the leaf mechanical strength. Moreover, cellulose plays a crucial role in increasing leaf strength and toughness. The principal component analysis plot based on leaf trait values clearly separates Quercus species into two groups corresponding to evergreen and deciduous species. Conclusions Sclerophyllous Quercus species are tougher and stronger owing to their thicker epidermis outer wall and/or higher cellulose concentration. Furthermore, section Ilex species share common traits, although they occupy different climates. In addition, evergreen species living in mediterranean-type climates share common leaf traits irrespective of their different phylogenetic origin.

Leaf mass per area (LMA), which is an important functional trait in leaf economic spectrum and plant growth analysis, is measured from leaf discs or whole leaves. Differences between the measurement methods may lead to large differences in the estimates of LMA values.We examined to what extent estimates of LMA based on whole leaves match those based on discs using 334 woody species from a wide range of biomes (tropics, subtropics, savanna, and temperate), whether the relationship varied by leaf morphology (tissue density, leaf area, leaf thickness), punch size (0.6- and 1.0-cm diameter), and whether the extent of intraspecifc variation for each species matches.Disc-based estimates of species mean LMA matched the whole-leaf estimates well, and whole-leaf LMA tended to be 9.69% higher than leaf-disc LMA. The ratio of whole-leaf LMA to leaf-disc LMA was higher for species with higher leaf tissue density and larger leaves, and variance in the ratio was greater for species with lower leaf tissue density and thinner leaves. Estimates based on small leaf discs also inflated the ratio. The extent of the intraspecific variation only weakly matched between whole-leaf and disc-based estimates (ROur results suggest that simple conversion between whole-leaf and leaf-disc LMA is difficult for species obtained with a small leaf punch, but it should be possible for species obtained with a large+ leaf punch. Accurately representing leaf traits will likely require careful selection between leaf-disc and whole-leaf traits depending on the objectives. Quantifying intraspecific variation using leaf discs should be also considered with caution.

Phyllostachys edulis (Poales: Poaceae) is a bamboo species with well-developed rhizomes, which play important roles in growth, resource storage and transport. However, the extent to which rhizomes are produced, accumulated and turn over annually at the stand level remains largely unknown. We studied the biomass, production and turnover rate of rhizomes and other organs (culms, branches, leaves and roots) in a bamboo stand in Japan between 2013 and 2018. We sought to answer the following questions: To what extent is the newly assimilated carbon allocated to rhizomes, and how rapid is carbon turnover in rhizomes? How does biomass allocation to below-ground parts in bamboo ramets compare to that in woody plant individuals of similar size? We found the amount of newly produced rhizomes was 0.90 Mg C ha–1 year−1, which accounted for 9.5% of total new biomass. The carbon turnover rate of rhizomes was 0.11 g g−1 year−1, which was slower than that of other organs (i.e. longer lifespan). Compared to other woody plants of similar biomass, bamboo had 2.0-fold higher biomass allocation to below-ground organs due to the high biomass of rhizomes. Furthermore, bamboo allocated 8.7-fold lower biomass to leaves despite their high growth rates, perhaps due to the thin (but leathery) leaves and green stems that can photosynthesize as well. Our study highlights that the large storage capacity of below-ground rhizomes along with the efficient above-ground production system are the key growth features of P. edulis, which are likely to contribute to their success in temperate forests.

Leaf trichomes on the lower leaf surface are common in many plant species, especially those grown under dry and/or low-temperature conditions; however, their adaptive significance remains unclear. Lower-side leaf trichomes can directly decrease gas fluxes through increased gas-diffusion resistance but can indirectly increase gas fluxes through increased leaf temperature owing to increased heat-diffusion resistance. We examined whether the combined direct and indirect effects of trichome resistance increase photosynthetic rates and water-use efficiency (WUE) using Metrosideros polymorpha Gaud., which varies widely in the masses of lower-side non-glandular leaf trichomes across various environments on the Hawaiian Islands. We employed both field surveys, including ecophysiological measurements at five elevation sites, and simulation analyses to predict the gas-exchange rates of leaves with various trichome-layer thicknesses across a wide range of environmental conditions. Field surveys showed that the trichome-layer thickness was the largest at the coldest and driest site and the thinnest at the wettest site. Field surveys, experimental manipulations and simulation analyses demonstrated that leaf trichomes significantly increased leaf temperature owing to the increased heat resistance. Simulation analyses showed that the effect of leaf trichomes on heat resistance was much larger than that on gas-flux resistance. Leaf trichomes can increase daily photosynthesis only in cold dry areas by increasing the leaf temperature. However, the increased leaf temperature with leaf trichomes resulted in a consistent decrease in the daily WUE at all elevation sites. The magnitudes of trichome effects on gas-exchange rates were associated with the temperature difference across the elevational gradient, the strong light intensity in Hawaii, the leaf-size variation and the conservative stomatal behavior of M. polymorpha as well as the trichome-layer thickness. In summary, the lower-side leaf trichomes in M. polymorpha can be beneficial for carbon assimilation in low-temperature environments but not for water conservation in most environments in terms of diffusion resistance.

As Earth's climate has varied strongly through geological time, studying the impacts of past climate change on biodiversity helps to understand the risks from future climate change. However, it remains unclear how paleo-climate shapes spatial variation in biodiversity. Here, we assessed the influence of Quaternary climate change on spatial dissimilarity in taxonomic, phylogenetic, and functional composition among neighboring 200-kilometer cells (beta-diversity) for angiosperm trees worldwide. We found that larger glacial-interglacial temperature change was strongly associated with lower spatial turnover (species replacements) and higher nestedness (rich-ness changes) components of beta-diversity across all three biodiversity facets. Moreover, phylogenetic and functional turnover was lower and nestedness higher than random expectations based on taxonomic beta -di-versity in regions that experienced large temperature change, reflecting phylogenetically and functionally se-lective processes in species replacement, extinction, and colonization during glacial-interglacial oscillations. Our results suggest that future human-driven climate change could cause local homogenization and reduction in taxonomic, phylogenetic, and functional diversity of angiosperm trees worldwide. W.-B.X. and A.O. acknowledge support from the Aarhus University Research Foundation (AUFF) Starting Grant (AUFF-F-2018-7-8). J.-C.S. acknowledges support from the Danish Council for Independent Research|Natural Sciences (grant 6108-00078B) to the TREECHANGE Project. J.-C.S. also considers this work a contribution to the Center for Ecological Dynamics in a Novel Biosphere (ECONOVO) funded by Danish National Research Foundation (grant DNRF173) and the VILLUM Investigator project “Biodiversity Dynamics in a Changing World” funded by VILLUM FONDEN (grant 16549). W.L.E. was supported by the VILLUM FONDEN (grant 00025354). M.A. was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery grants program. C.B. was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (2022R1A2C1003504). A.G.G. was supported by the ANID PIA/BASAL (grant FB210006) and FONDECYT (grant 1200468). R.E.O. was supported by the German Research Foundation to German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig (DFG-FZT 118, 202548816). J.Pe. was supported by the Fundación Ramón Areces project (CIVP20A6621) and Spanish Government project (PID2019-110521GB-I00). J.Pi. was supported by the Estonian Research Council Grants (PUT1355, PRG 1405) and Mobilitas Pluss (MOBERC11). V.D.P. was supported by the National Council of Scientific and Technological Development (CNPq) of Brazil (grant 307689/2014-0).

Competitive asymmetry is one of the most important determinants of size structure in plant communities. Many studies indicated that light competition is size-asymmetric in monospecific stands of herbaceous plants, as taller individuals preempt light. However, competition is size-symmetric in multispecific stands because shorter species adapted to shade. Then, a question arises on whether light competition is asymmetric or symmetric if a shade-tolerant species occupies the stand, such as climax forests. Moreover, it is also interesting how gap dynamics affect competitive asymmetry, given the fact that gap formation can improve light availability in lower layers of the canopy. In cool temperate and natural climax forest of northern Japan, dominated by a shade-tolerant tree, Fagus crenata, we investigated the plant size, growth rate, and three-dimensional distribution of foliage and light availability. We found that competitive asymmetry varied dynamically across the forest. In closed canopies, the relative growth rate (RGR) was higher in taller trees, indicating size-asymmetric growth. Shorter trees partly compensated for their light interception by having higher leaf area per aboveground mass (leaf area ratio; LAR) but did not achieve comparative RGR to taller trees. Conversely, in gaps, the RGR of shorter trees was equivalent to those of taller trees because of the improved light availability for smaller trees, indicating size-symmetric growth. These results suggest that changes in competitive asymmetry driven by gap dynamics can influence the spatiotemporal diversity of size structures in forests.

Leaf functional traits and their covariation underlie plant ecological adaptations along environmental gradients, but there is limited information on the global covariation patterns of key leaf construction traits. To explore how leaf construction traits co-vary across diverse climate and soil environmental conditions, we compiled a global dataset including cell wall mass per unit leaf mass (CWmass ), leaf carbon (C) and calcium (Ca) concentrations, and specific leaf area (SLA) for 2348 angiosperm species from 340 sites world-wide. Our results demonstrated negative correlations between leaf C and Ca concentrations and between leaf C and SLA across diverse nongraminoid angiosperms. Leaf C concentration increased with increasing mean annual temperature (MAT) and mean annual precipitation (MAP) and with decreasing soil pH and calcium carbonate (CaCO3 ) concentration, whereas leaf Ca concentration and SLA exhibited the opposite responses to these environmental variables. The covariations of leaf Ca-C and of leaf SLA-C were stronger in habitats with lower MAT and MAP, and/or higher soil CaCO3 content. This global-scale analysis demonstrates that the leaf C and Ca concentrations and SLA together govern the C and biomass investment strategies in leaves of nongraminoids. We conclude that environmental conditions strongly shape leaf construction traits and their covariation patterns.

Safeguarding Earth?s tree diversity is a conservation priority due to the importance of trees for biodiversity and ecosystem functions and services such as carbon sequestration. Here, we improve the foundation for effective conservation of global tree diversity by analyzing a recently developed database of tree species covering 46,752 species. We quantify range protection and anthropogenic pressures for each species and develop conservation priorities across taxonomic, phylogenetic, and functional diversity dimensions. We also assess the effectiveness of several influential proposed conservation prioritization frameworks to protect the top 17% and top 50% of tree priority areas. We find that an average of 50.2% of a tree species? range occurs in 110-km grid cells without any protected areas (PAs), with 6,377 small-range tree species fully unprotected, and that 83% of tree species experience nonnegligible human pressure across their range on average. Protecting highpriority areas for the top 17% and 50% priority thresholds would increase the average protected proportion of each tree species? range to 65.5% and 82.6%, respectively, leaving many fewer species (2,151 and 2,010) completely unprotected. The priority areas identified for trees match well to the Global 200 Ecoregions framework, revealing that priority areas for trees would in large part also optimize protection for terrestrial biodiversity overall. Based on range estimates for >46,000 tree species, our findings show that a large proportion of tree species receive limited protection by current PAs and are under substantial human pressure. Improved protection of biodiversity overall would also strongly benefit global tree diversity. Made available in DSpace on 2022-06-21T15:23:55Z (GMT). No. of bitstreams: 1 Guo-et-al.-2022-PNAS-High-exposure-of-global-tree-diversity-to-human-pressure.pdf: 2523289 bytes, checksum: 245be3df3fb487ed152d25bf50f4e984 (MD5) Previous issue date: 2022 Proceedings of the National Academy of Sciences of the United States of America.

The mechanical strength of a plant stem (a load-bearing organ) helps the plant resist drooping, buckling and fracturing. We previously proposed a method for quickly evaluating the stiffness of an inflorescence stem in the model plant Arabidopsis thaliana based on measuring its natural frequency in a free-vibration test. However, the relationship between the stiffness and flexural rigidity of inflorescence stems was unclear. Here, we compared our previously described free-vibration test with the three-point bending test, the most popular method for calculating the flexural rigidity of A. thaliana stems, and examined the extent to which the results were correlated. Finally, to expand the application range, we present an example of a modified free-vibration test. Our results provide a reference for improving estimates of the flexural rigidity of A. thaliana inflorescence stems.

Purpose of Review: Defining the mechanisms behind and the leaf economic consequences of the development of sclerophylly in woody plants will allow us to understand its ecological implications, anticipate the potential for adaptation of different tree species to global change, and define new woody plant ideotypes for stress tolerance. Recent Findings: Sclerophylly has evolved independently in different woody plant genera and has been traditionally considered as a stress-tolerance trait. However, the underlying drivers for this functional trait are still a matter of debate; it has been proposed as an adaptive response to miscellaneous stress factors, such as nutrient scarcity, drought stress, herbivory, and cold tolerance, and due to the large investment costs of sclerophylly, it is generally associated with a longer leaf life span. Summary: The genus Quercus constitutes a unique living laboratory to understand global adaptive patterns along the leaf economic spectrum in forest trees. With more than 400 species, oaks are distributed along six zonobiomes and its versatility has resulted in a wide range of variations in leaf functional traits and contrasting adaptive strategies. However, although this wide variability cannot be explained alone by any of the ecological factors considered, such as drought, nutrient scarcity, low temperatures during vegetative period, and physical damage, neither any of them could be fully discarded. Noteworthy, our study also suggests that these constraints may have a synergistic effect, and from a functional point of view, we can conclude that in oaks leaf habit largely modulates the physiological implications of sclerophylly.

Aim We analyse how functional diversity (FD) varies across European natural forests to understand the effects of environmental and competitive filtering on plant trait distribution. Location Forest ecosystems in Europe from 11°W to 36°E and 29.5°N to 62°N. Taxon Pinaceae, Fagaceae and Betulaceae, Oleaceae, Tiliaceae, Aceraceae, Leguminosae (unspecific). Methods We adopted the existing Dynamic Global Vegetation Model Lund‐Potsdam‐Jena managed Land of flexible individual traits (LPJmL‐FIT) for Europe by eliminating both bioclimatic limits of plant functional types (PFTs) and replacing prescribed values of functional traits for PFTs with emergent values under influence of environmental filtering and competition. We quantified functional richness (FR), functional divergence (FDv) and functional evenness (FE) in representative selected sites and at Pan‐European scale resulting from simulated functional and structural trait combinations of individual trees. While FR quantifies the amount of occupied trait space, FDv and FE describe the distribution and abundance of trait combinations, respectively, in a multidimensional trait space. Results Lund‐Potsdam‐Jena managed Land of flexible individual traits reproduces spatial PFTs and local trait distributions and agrees well with observed productivity, biomass and tree height of European natural forests. The observed site‐specific trait distributions and spatial gradients of traits of the leaf‐ and stem‐resource economics spectra coincide with environmental filtering and the competition for light and water in environments with strong abiotic stress. Where deciduous and needle‐leaved trees co‐occur, for example, in boreal and mountainous forests, the potential niche space is wide (high FR), and extreme ends in the niche space are occupied (high FDv). We find high FDv in Mediterranean forests where drought increasingly limits tree growth, thus niche differentiation becomes more important. FDv decreases in temperate forests where a cold climate increasingly limits growth efficiency of broad‐leaved summer green trees, thus reducing the importance of competitive exclusion. Highest FE was simulated in wet Atlantic and southern Europe which indicated relatively even niche occupation and thus high resource‐use efficiency. Main Conclusions We find FD resulting from both environmental and competitive filtering. Pan‐European FR, FDv and FE demonstrate the influence of climate gradients and intra‐ and inter‐PFT competition. The indices underline a generally high FD of natural forests in Europe. Co‐existence of functionally diverse trees across PFTs emerges from alternative (life‐history) strategies, disturbance and tree demography.

Background and AimsPlants inhabiting arid environments tend to have leaf trichomes, but their adaptive significance remains unclear. Leaf trichomes are known to play a role in plant defence against herbivores, including gall makers. Because gall formation can increase water loss partly through increased surface area, we tested the novel hypothesis that leaf trichomes could contribute to avoiding extra water stress by impeding gall formation, which would have adaptive advantages in arid environments.MethodsWe focused on Metrosideros polymorpha, an endemic tree species in the Hawaiian Islands, whose leaves often suffer from galls formed by specialist insects, Hawaiian psyllids (Pariaconus spp.). There is large variation in the amount of leaf trichomes (0–40 % of leaf mass) in M. polymorpha. Three gall types are found on the island of Hawaii: the largest is the ‘cone’ type, followed by ‘flat’ and ‘pit’ types. We conducted laboratory experiments to quantify the extent to which gall formation is associated with leaf water relations. We also conducted a field census of 1779 individuals from 48 populations across the entire range of habitats of M. polymorpha on the island of Hawaii to evaluate associations between gall formation (presence and abundance) and the amount of leaf trichomes.Key ResultsOur laboratory experiment showed that leaf minimum conductance was significantly higher in leaves with a greater number of cone- or flat-type galls but not pit-type galls. Our field census suggested that the amount of trichomes was negatively associated with probabilities of the presence of cone- or flat-type galls but not pit-type galls, irrespective of environmental factors.ConclusionOur results suggest that leaf trichomes in M. polymorpha can contribute to the avoidance of extra water stress through interactions with some gall-making species, and potentially increase the fitness of plants under arid conditions.

Aims: Light availability varies drastically in forests, both vertically and horizontally. Vertical light heterogeneity (i.e., patterns of light attenuation from the forest canopy to the floor) may be related to light competition among trees, while horizontal light heterogeneity (i.e., variations in light intensity at a given height within forests) may be associated with light-niche partitioning among tree species. However, light heterogeneity in vertical and horizontal directions and their associations with forest structure are rarely studied to date. Here we report the first comprehensive study to compare the vertical and horizontal light heterogeneity in differently aged forests in two forest types. Location: Twelve forest stands of different ages in cool-temperate forests (consisting of deciduous broad-leaved trees) and five of different ages in warm-temperate forests (evergreen conifer and deciduous broad-leaved trees) in Japan. Methods: We measured vertical light profiles at 1-m intervals from the understorey (1 m above the ground) to the top canopy (12–22 m depending on stands) at 16 locations for each stand (20 m × 20 m). We also measured structural parameters (diameter at breast height, height, and crown dimensions) for all major trees in these stands. Results: Along the secondary successional gradients, the vertical and horizontal light heterogeneity changed in a systematic manner in both forests. The vertical light attenuation rate was steeper in early succession and more gradual in late succession, and the horizontal light heterogeneity was relatively small in early succession and more pronounced in late succession. The vertical light attenuation rate was different between the two forest types; the light intensity dropped more sharply from the canopy surface in the cool-temperate forests due to the crown being vertically shorter and denser (i.e., higher leaf density per unit volume). Conclusion: In early succession, a steeper light attenuation rate is likely related to the strong light competition among co-occurring trees and thus a self-thinning process. In late succession, the high spatial light heterogeneity in forests (i.e., larger horizontal light heterogeneity and gradual light attenuation rate) may allow more species to partition light, and thus may enhance species coexistence and diversity.

In recent years, attempts have been made in linking pressure–volume parameters and the leaf economics spectrum to expand our knowledge of the interrelationships among leaf traits. We provide theoretical and empirical evidence for the coordination of the turgor loss point and associated traits with net CO2 assimilation (An) and leaf mass per area (LMA). We measured gas exchange, pressure–volume curves and leaf structure in 45 ferns and angiosperms, and explored the anatomical and chemical basis of the key traits. We propose that the coordination observed between mass-based An, capacitance and the turgor loss point (πtlp) emerges from their shared link with leaf density (one of the components of LMA) and, specially, leaf saturated water content (LSWC), which in turn relates to cell size and nitrogen and carbon content. Thus, considering the components of LMA and LSWC in ecophysiological studies can provide a broader perspective on leaf structure and function. Published

The existence of sclerophyllous plants has been considered an adaptive strategy against different environmental stresses. As it literally means “hard-leaved”, it is essential to quantify the leaf mechanical properties to understand sclerophylly. However, the relative importance of each leaf trait on mechanical properties is not yet well established. The genusQuercusis an excellent system to shed light on this since it minimizes phylogenetic variation while having a wide variation in sclerophylly. Thus, leaf anatomical traits and cell wall composition were measured, analyzing their relationship with LMA and leaf mechanical properties in a set of 25 oak species. Outer wall contributed strongly to leaf mechanical strength. Moreover, cellulose plays a critical role in increasing leaf strength and toughness. The PCA plot based on leaf trait values clearly separatedQuercusspecies into two groups corresponding to evergreen and deciduous species. SclerophyllousQuercusspecies are tougher and stronger due to their thicker epidermis outer wall and/or higher cellulose concentration. Furthermore, sectionIlexspecies share common traits regardless of they occupy quite different climates. In addition, evergreen species living in Mediterranean-type climates share common leaf traits irrespective of their different phylogenetic origin.

Understanding how evolutionary history and the coordination between trait trade-off axes shape the drought tolerance of trees is crucial to predict forest dynamics under climate change. Here, we compiled traits related to drought tolerance and the fast-slow and stature-recruitment trade-off axes in 601 tropical woody species to explore their covariations and phylogenetic signals. We found that xylem resistance to embolism (P50) determines the risk of hydraulic failure, while the functional significance of leaf turgor loss point (TLP) relies on its coordination with water use strategies. P50 and TLP exhibit weak phylogenetic signals and substantial variation within genera. TLP is closely associated with the fast-slow trait axis: slow species maintain leaf functioning under higher water stress. P50 is associated with both the fast-slow and stature-recruitment trait axes: slow and small species exhibit more resistant xylem. Lower leaf phosphorus concentration is associated with more resistant xylem, which suggests a (nutrient and drought) stress-tolerance syndrome in the tropics. Overall, our results imply that (1) drought tolerance is under strong selective pressure in tropical forests, and TLP and P50 result from the repeated evolutionary adaptation of closely related taxa, and (2) drought tolerance is coordinated with the ecological strategies governing tropical forest demography. These findings provide a physiological basis to interpret the drought-induced shift toward slow-growing, smaller, denser-wooded trees observed in the tropics, with implications for forest restoration programmes.

We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge., Measurement(s)plant traitTechnology Type(s)digital curationSample Characteristic - OrganismViridiplantaeSample Characteristic - LocationAustralia Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14545755

Deciduous and evergreen species, which have evolved repeatedly across different clades, can coexist in a given environment despite substantial differences in their leaf traits. It remains unclear how these two groups differ in the development of leaf traits over their lifespans or how their carbon economy - the balance between lifetime carbon gain and leaf construction cost - is determined. We determined the photosynthetic rate (A

We synthesized non- and Eu-doped AlN ceramics by the spark plasma sintering (SPS) method and characterized their photoluminsecence (PL) and thermally stimutrated luminescence (TSL) properties. In the PL properties, the non-doped AlN samples showed a broad emission peaking around 400 nm. In contract, the Eu-doped AlN samples showed two broad emission bands around 400 and 520 nm, and two sharp emission peaks at 610 and 700 nm. The origins of the emission peaks at 400, 520, 610 and 700 nm were due to complexes composed of Al vacancy and O impurity, 5d-4f transitons of Eu2+, 5D0→7F2 and 5D0→7F4 transitions of Eu3+, respectively. Regarding the TSL properties, the TSL intensities of the 0.01 and 0.1% Eu-doped AlN samples were higher than that of the non-doped AlN sample. It was confirmed that the 0.1% Eu-doped AlN showed a good linearity from 0.01 to 1000 mGy.

Dense leaf trichomes can directly decrease gas fluxes through increased gas diffusion resistance and indirectly increase gas fluxes through increased leaf temperature due to increased heat diffusion resistance, which may contribute to adaptation to dry and/or low‐temperature conditions. However, it remains unclear whether the leaf‐trichome resistance increases or decreases the gas‐exchange rates through combined direct and indirect effects. We focused on Metrosideros polymorpha, a dominant tree species inhabiting a large range of environmental gradients in the Hawaiian Islands, whose leaves have an enormous variation in trichome thickness on the lower surface. In five elevational sites, we measured leaf morphological and physiological traits including trichome thickness, gas‐exchange characteristics, and leaf temperature. The trichome thickness was largest in the coldest and driest site and thinnest at the wettest site. Leaf temperature was significantly increased with trichome thickness. With biophysical and physiological models, we show that leaf trichomes can increase the daily photosynthesis through increasing leaf temperature only in the cold alpine area. The daily water‐use efficiency can be lower with increasing leaf trichomes at any elevational sites. Therefore, in terms of diffusion resistance, the leaf trichomes of M. polymorpha can contribute to the adaptation to low‐temperature environments but not to dry environments.

The acquisitive-conservative axis of plant ecological strategies results in a pattern of leaf trait covariation that captures the balance between leaf construction costs and plant growth potential. Studies evaluating trait covariation within species are scarcer, and have mostly dealt with variation in response to environmental gradients. Little work has been published on intraspecific patterns of leaf trait covariation in the absence of strong environmental variation.Methods: We analysed covariation of four leaf functional traits (SLA: specific leaf area, LDMC: leaf dry matter content, Ft: force to tear, and Nm: leaf nitrogen content) in six Poaceae and four Fabaceae species common in the dry Chaco forest of Central Argentina, growing in the field and in a common garden. We compared intraspecific covariation patterns (slopes, correlation and effect size) of leaf functional traits with global interspecific covariation patterns. Additionally, we checked for possible climatic and edaphic factors that could affect the intraspecific covariation pattern.Key Results: We found negative correlations for the LDMC-SLA, Ft-SLA, LDMC-Nm , and Ft-Nm trait pairs. This intraspecific covariation pattern found both in the field and in the common garden and not be explained by climatic or edaphic variation in the field follows the expected acquisitive-conservative axis. At the same time, we found quantitative differences in slopes among different species, and between these intraspecific patterns and the interspecific ones. Many of these differences seem to be idiosyncratic, but some appear consistent among species (e.g.all the intraspecific LDMC-SLA and LDMC-Nm slopes tend to be shallower than the global).Conclusions: Our study indicates that the acquisitive-conservative leaf functional trait covariation pattern occurs at the intraspecific level even in the absence of relevant environmental variation in the field. This suggests a high degree of variation-covariation in leaf functional traits not driven by environmental variables. Fil: Gorne, Lucas Damián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Díaz, Sandra Myrna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina Fil: Minden, Vanessa. University of Oldenburg; Alemania. Vrije Universiteit Brussel; Bélgica Fil: Onoda, Yusuke. Kyoto University. School of Agriculture; Japón Fil: Kramer, Koen. Wageningen University; Países Bajos Fil: Muir, Christopher. University Of Hawaii; Estados Unidos Fil: Michaletz, Sean T. University of British Columbia; Canadá Fil: Lavorel, Sandra. Centre National de la Recherche Scientifique; Francia Fil: Sharpe, Joanne. Sharplex Services, Edgecomb; Estados Unidos Fil: Jansen, Steven. Universitat Ulm; Alemania Fil: Slot, Martijn. Smithsonian Tropical Research Institute; Panamá Fil: Chacon, Maximiliano Eduardo. Universidad de Costa Rica; Costa Rica Fil: Boenisch, Gerhard. Max Planck Institute For Biogeochemistry; Alemania

Trees are of vital importance for ecosystem functioning and services at local to global scales, yet we still lack a detailed overview of the global patterns of tree diversity and the underlying drivers, particularly the imprint of paleoclimate. Here, we present the high-resolution (110 km) worldwide mapping of tree species richness, functional and phylogenetic diversities based on ∼7 million quality-assessed occurrences for 46,752 tree species (80.5% of the estimated total number of tree species), and subsequent assessments of the influence of paleo-climate legacies on these patterns. All three tree diversity dimensions exhibited the expected latitudinal decline. Contemporary climate emerged as the strongest driver of all diversity patterns, with Pleistocene and deeper-time (>107 years) paleoclimate as important co-determinants, and, notably, with past cold and drought stress being linked to reduced current diversity. These findings demonstrate that tree diversity is affected by paleoclimate millions of years back in time and highlight the potential for tree diversity losses from future climate change.

Although trees are key to ecosystem functioning, many forests and tree species across the globe face strong threats. Preserving areas of high biodiversity is a core priority for conservation; however, different dimensions of biodiversity and varied conservation targets make it difficult to respond effectively to this challenge. Here, we (i) identify priority areas for global tree conservation using comprehensive coverage of tree diversity based on taxonomy, phylogeny, and functional traits; and (ii) compare these findings to existing protected areas and global biodiversity conservation frameworks. We find that ca. 51% of the top-priority areas for tree biodiversity are located in current protected areas. The remaining half top-priority areas are subject to moderate to high human pressures, indicating conservation actions are needed to mitigate these human impacts. Our findings emphasize the effectiveness of using tree conservation priority areas for future global conservation planning.

The majority of variation in six traits critical to the growth, survival and reproduction of plant species is thought to be organised along just two dimensions, corresponding to strategies of plant size and resource acquisition. However, it is unknown whether global plant trait relationships extend to climatic extremes, and if these interspecific relationships are confounded by trait variation within species. We test whether trait relationships extend to the cold extremes of life on Earth using the largest database of tundra plant traits yet compiled. We show that tundra plants demonstrate remarkably similar resource economic traits, but not size traits, compared to global distributions, and exhibit the same two dimensions of trait variation. Three quarters of trait variation occurs among species, mirroring global estimates of interspecific trait variation. Plant trait relationships are thus generalizable to the edge of global trait-space, informing prediction of plant community change in a warming world., It is unclear whether plant trait relationships found at the global scale extend to climatic extremes. Here the authors analyse six major aboveground traits to show that known plant trait relationships extend to the tundra biomes and exhibit the same two dimensions of variation detected at the global scale.

Spatial variations of maximum canopy height are key indicators of many ecosystem processes such as above-ground biomass and productivity. With rapid advances in remote sensing techniques, such as airborne laser scanning (ALS), we can now measure canopy height, tree density, and canopy gaps from local to large scales. But these data are yet to be fully exploited for a better understanding of canopy height variations in relation to fine topographical heterogeneities and neighborhood conditions at the landscape level (>100 km2). In this study, we analyzed ALS data to extract spatial variations in canopy height and topographic features for a forest-dominated area of 230 km2 in Kyoto, Japan. The study area spanned an elevational range from 70 to 1000 m a.s.l and included four forest types, i.e., cedar or cypress plantations (PL), natural evergreen needle leaf forests (ENF), deciduous broadleaved forests (DBF), and evergreen broadleaved forests (EBF). PL had a greater mean canopy height than ENF, both of which were taller than DBF and EBF. Canopy height exhibited a hump-shaped relationship with elevation with the peak value at mid-altitude (461–560 m) in all forest types. Canopy height was greater by 5-10 m in the concave valleys than on the convex slopes and ridges. Trees were taller at greater distances from forest gaps and with lower tree density in the neighborhood. Local tree density, distance from the nearest canopy gap, and topographic curvatures were the most significant predictors in the best-fitted model (Random Forest: R2 = 0.41). The analytical approach developed in this study provides a useful tool for planning proper land use and maintaining a healthy forest stand at the regional scale.

The leaf economic spectrum is a widely studied axis of plant trait variability that defines a trade-off between leaf longevity and productivity. While this has been investigated at the global scale, where it is robust, and at local scales, where deviations from it are common, it has received less attention at the intermediate scale of plant functional types (PFTs). We investigated whether global leaf economic relationships are also present within the scale of plant functional types (PFTs) commonly used by Earth System models, and the extent to which this global-PFT hierarchy can be used to constrain trait estimates. We developed a hierarchical multivariate Bayesian model that assumes separate means and covariance structures within and across PFTs and fit this model to seven leaf traits from the TRY database related to leaf longevity, morphology, biochemistry, and photosynthetic metabolism. Although patterns of trait covariation were generally consistent with the leaf economic spectrum, we found three approximate tiers to this consistency. Relationships among morphological and biochemical traits (specific leaf area [SLA], N, P) were the most robust within and across PFTs, suggesting that covariation in these traits is driven by universal leaf construction trade-offs and stoichiometry. Relationships among metabolic traits (dark respiration [R-d], maximum RuBisCo carboxylation rate [V-c,V-max], maximum electron transport rate [J(max)]) were slightly less consistent, reflecting in part their much sparser sampling (especially for high-latitude PFTs), but also pointing to more flexible plasticity in plant metabolistm. Finally, relationships involving leaf lifespan were the least consistent, indicating that leaf economic relationships related to leaf lifespan are dominated by across-PFT differences and that within-PFT variation in leaf lifespan is more complex and idiosyncratic. Across all traits, this covariance was an important source of information, as evidenced by the improved imputation accuracy and reduced predictive uncertainty in multivariate models compared to univariate models. Ultimately, our study reaffirms the value of studying not just individual traits but the multivariate trait space and the utility of hierarchical modeling for studying the scale dependence of trait relationships.

Moso bamboo (Phyllostachys edulis) groves have been expanding in Japanese forests, thus an assessment of the rate of bamboo grove expansion is a critical issue. Previous studies used time-series data which span typically more than a few years in order to determine the expansion of bamboo groves. This method cannot be used when time-series data were not available. In this study, we developed and tested a simple indicator based on one-time measurement of spatial distribution of culms to estimate the rate of bamboo grove expansion. Among 19 locations at four sites, the distribution patterns of culms from the pure bamboo stands to the expanding front were highly correlated with the actual edge expansion rate (E) based on the aerial photographs collected over ca. 15- and 30-year periods. In contrast, the culm density in the original stand itself was not correlated with E. These results suggest that one-time measurement of the distribution patterns of living culms (but not stand density) could be a useful indicator for estimating the expansion rates of bamboo groves.

In an era of ecosystem degradation and climate change, maximizing microbial functions in agroecosystems has become a prerequisite for the future of global agriculture. However, managing species-rich communities of plant-associated microbiomes remains a major challenge. Here, we propose interdisciplinary research strategies to optimize microbiome functions in agroecosystems. Informatics now allows us to identify members and characteristics of 'core microbiomes', which may be deployed to organize otherwise uncontrollable dynamics of resident microbiomes. Integration of microfluidics, robotics and machine learning provides novel ways to capitalize on core microbiomes for increasing resource-efficiency and stress-resistance of agroecosystems.

The leaf economics spectrum (LES) represents a suite of intercorrelated leaf traits concerning construction costs per unit leaf area, nutrient concentrations, and rates of carbon fixation and tissue turnover. Although broad trade-offs among leaf structural and physiological traits have been demonstrated, we still do not have a comprehensive view of the fundamental constraints underlying the LES trade-offs. Here, we investigated physiological and structural mechanisms underpinning the LES by analysing a novel data compilation incorporating rarely considered traits such as the dry mass fraction in cell walls, nitrogen allocation, mesophyll CO2 diffusion and associated anatomical traits for hundreds of species covering major growth forms. The analysis demonstrates that cell wall constituents are major components of leaf dry mass (18-70%), especially in leaves with high leaf mass per unit area (LMA) and long lifespan. A greater fraction of leaf mass in cell walls is typically associated with a lower fraction of leaf nitrogen (N) invested in photosynthetic proteins; and lower within-leaf CO2 diffusion rates, as a result of thicker mesophyll cell walls. The costs associated with greater investments in cell walls underpin the LES: long leaf lifespans are achieved via higher LMA and in turn by higher cell wall mass fraction, but this inevitably reduces the efficiency of photosynthesis.

The effects of high atmospheric CO2 concentration ([CO2]) on ecosystem processes have been explored using temporal facilities such as open-top-chambers and free-air CO2 enrichment. However, the effects of high [CO2] on soil properties takes decades and may not be captured by short-term experiments. Natural CO2 springs provide a unique opportunity to study the long-term effects of high [CO2]. In this study, we investigated soil properties at a natural CO2 spring. We found that the amounts of total carbon (C) and nitrogen (N) stored in the soil at the high [CO2] site exceeded those in the reference site by 60 and 30%, respectively. The effects of high [CO2] were large in the upper slope position where the canopy openness was high and plants grew faster, but no effects were detected in the lowest position where the canopy openness was lower (half of that at the upper slope position). In contrast, effects of high [CO2] on soil N dynamics, such as N mineralization and nitrification rates, did not exhibit a slope gradient. This suggests that effects of high [CO2] differed among soil stoichiometric characteristics and N dynamics. These complicated effects of high [CO2] imply that the future effects of high [CO2] on ecosystems could vary widely in conjunction with environmental conditions such as light availability and/or topographic conditions.

International audience; The temperature response of photosynthesis is one of the key factors determining predicted responses to warming in global vegetation models (GVMs). The response may vary geographically, owing to genetic adaptation to climate, and temporally, as a result of acclimation to changes in ambient temperature. Our goal was to develop a robust quantitative global model representing acclimation and adaptation of photosynthetic temperature responses. We quantified and modelled key mechanisms responsible for photosynthetic temperature acclimation and adaptation using a global dataset of photosynthetic CO2 response curves, including data from 141 C3 species from tropical rainforest to Arctic tundra. We separated temperature acclimation and adaptation processes by considering seasonal and common‐garden datasets, respectively. The observed global variation in the temperature optimum of photosynthesis was primarily explained by biochemical limitations to photosynthesis, rather than stomatal conductance or respiration. We found acclimation to growth temperature to be a stronger driver of this variation than adaptation to temperature at climate of origin. We developed a summary model to represent photosynthetic temperature responses and showed that it predicted the observed global variation in optimal temperatures with high accuracy. This novel algorithm should enable improved prediction of the function of global ecosystems in a warming climate.

Leaf mechanical strength and photosynthetic capacity are critical plant life-history traits associated with tolerance and growth under various biotic and abiotic stresses. In principle, higher mechanical resistance achieved via higher relative allocation to cell walls should slow photosynthetic rates. However, interspecific relationships among these two leaf functions have not been reported. We measured leaf traits of 57 dominant woody species in a subtropical evergreen forest in China, focusing especially on photosynthetic rates, mechanical properties, and leaf lifespan (LLS). These species were assigned to two ecological strategy groups: shade-tolerant species and light-demanding species. On average, shade-tolerant species had longer LLS, higher leaf mechanical strength but lower photosynthetic rates, and exhibited longer LLS for a given leaf mass per area (LMA) or mechanical strength than light-demanding species. Depending on the traits and the basis of expression (per area or per mass), leaf mechanical resistance and photosynthetic capacity were either deemed unrelated, or only weakly negatively correlated. We found only weak support for the proposed trade-off between leaf biomechanics and photosynthesis among co-occurring woody species. This suggests there is considerable flexibility in these properties, and the observed relationships may result more so from trait coordination than any physically or physiologically enforced trade-off.

Summary Land-use change can modify the functional composition of tree communities, which is an essential determinant of the ecosystem functions. The lack of consensus about the functional responses of tree communities to land-use change is a major uncertainty in the assessments of human impacts on terrestrial ecosystem functions. In this study, we applied a machine-learning method to a large data set consisting of 2574 tree communities across Japan to examine changes in the functional composition of tree communities after land-use change while considering contexts including successional trajectories, forest types and the presence of gymnosperms. Specifically, we hypothesized that functional changes along successional gradients after land-use change can be different in different contexts. Effects of two successional variables (stand age and basal area) on functional composition were highly significant throughout the study region. Changes in functional composition with changes in the two successional variables differed greatly, and the effects of basal area often outweighed those of stand age. Tree communities with small basal area were generally characterized by functional traits related to the resource-acquisitive strategy, that is short adult stature, low leaf mass per unit area, small seeds, low wood density and large leaves, especially when gymnosperms were excluded from the analysis. Decreasing basal area but not decreasing stand age often led to a considerable loss in functional diversity. Despite these general trends, functional changes along successional gradients after land-use change were not necessarily parallel and the opposite patterns were sometimes observed among forest types, traits and taxonomic groups. Synthesis. As a whole, our analyses demonstrate that the functional changes in tree communities after land-use change are highly evident in a given context but can be different under different contexts. These changes in functional composition can trigger variable changes in ecosystem functions such as carbon and nutrient cycling that depend on the context.

Altres ajuts europeus: P.A.W. was additionally supported by the European Union Fourth Environment and Climate Framework Programme (Project Number ENV4-CT970586)P.A.W. was additionally supported by the European Union Fourth Environment and Climate Framework Programme (Project Number ENV4-CT970586). The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature-trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.

Plant leaves provide the following main functions: (1) light interception and utilization of light energy for photosynthesis. This includes efficient light absorption under low and moderate light, while reducing excess light absorption under high light. (2) Incorporating CO2 as the substrate of photosynthesis, while limiting the amount of water lost. (3) Maintaining a stable internal environment for physiological processes by modulating leaf temperature. (4) Maintaining structural integrity that allows leaves to photosynthesize under various mechanical stresses such as gravity, wind, rainfall and herbivory. (5) Transporting water, photosynthates, and nutrients to realize efficient functioning of the plant and the leaf.

Large variations are found in leaf morphology and physiology across species in nature, reflecting diversity in carbon fixation and growth strategies. These variations in leaf traits are not random; rather, they are tightly coordinated with each other. Leaf traits can be expressed per leaf dry mass or per leaf area. A leaf-mass basis reflects leaf economics, i.e., revenues and expenditures per unit investment of biomass, while a leaf-area basis reflects fluxes in relation to surfaces. Leaf N and P concentrations, and photosynthetic and respiration rates – all considered on a mass basis, are negatively correlated with leaf mass per area (LMA) whilst leaf lifespan is positively correlated with LMA. These correlations are summarized into a single major axis called the “leaf economics spectrum” that runs from “quick-return” to “slow-return” species. On the other hand, correlations among area-based traits are less consistent and less understood in relation to leaf economy. LMA was positively correlated with leaf N content but mostly independent from photosynthetic rates per unit leaf area. Given that N is an essential element in photosynthetic proteins and thus photosynthesis, clarifying the mechanisms why the efficiency of photosynthesis (photosynthesis per unit N) decreases with LMA is a major concern in understanding the correlations among area-based traits in relation to leaf economy. Currently available data suggest that greater amounts of cell wall are required for long-lived leaves, which reduces the efficiency of photosynthesis by lowering (1) the fraction of leaf N invested in photosynthetic proteins and (2) CO2 diffusion rates through thicker and denser mesophyll cell walls. These physiological and structural constraints are a fundamental mechanism underpinning the general correlations among leaf economic traits.