Within the growth-survival trade-off framework, embolism resistance is considered a contributor to survival, yet whether greater embolism resistance inherently limits growth remains unclear. We investigated this relationship among 22 Eucalyptus species spanning wide precipitation and temperature gradients, grown under controlled conditions for 6-10 months. We quantified embolism resistance (drought-induced stem P50), growth, and wood anatomy. Our experimental results reveal a clear trade-off between embolism resistance and growth rate, consistently supported by both cross-species and phylogenetic (correlated-divergence) analyses. Faster growing species exhibited less negative P50 and higher vessel lumen fraction, driven by wider vessels, enhancing hydraulic conductivity. Conversely, slower growing species had more negative P50, characterised by thicker vessel walls and a greater density of narrower vessels, reducing hydraulic conductivity. P50 and growth rate were significantly related to climate-of-origin, with species from drier or colder regions exhibiting greater embolism resistance and slower growth. Furthermore, we conducted a global vote-counting review of 34 studies, showing weak but context-dependent support for the growth rate-P50 trade-off, with no evidence of concurrent faster growth and greater embolism resistance. These findings advance understanding of growth rate-embolism resistance trade-offs, reveal climatic adaptation mechanisms in woody species, and inform predictions of plant persistence under climate change.

Several transects have been established to study the sensitivity of carbon isotope discrimination (Δ13C) in woody plants to mean annual precipitation (MAP) across Australia. These have shown a surprising divergence in Δ13C-MAP sensitivity among subcontinental regions. We analysed previously reported data alongside new measurements from a transect in northeastern Queensland to explore potential drivers of regional-scale Δ13C-MAP sensitivity. Multiple lines of evidence indicated this sensitivity is related to soil phosphorus. In phosphorus-poor regions, Δ13C decreased less with decreasing MAP than in phosphorus-rich regions. Along two contrasting transects in northern Australia, Δ13C correlated with leaf phosphorus in the phosphorus-poor Northern Territory, but not in phosphorus-rich northeastern Queensland, where it instead correlated with leaf nitrogen. Common garden experiments for species from phosphorus-poor vs phosphorus-rich regions showed contrasting relationships between Δ13C and species range MAP. Finally, using an Australia-wide leaf gas exchange dataset, we showed that soil phosphorus influenced the ratio of intercellular to ambient CO2 concentrations (ci : ca), which in turn controls Δ13C; the influence was through stomatal conductance, not photosynthetic capacity. Higher stomatal conductance in phosphorus-poor regions appeared to moderate the decrease in Δ13C with decreasing precipitation. We suggest that high transpiration rates in these regions help to facilitate phosphorus foraging in phosphorus-impoverished, ancient soils.

Summary Quantifying relationships between traits and climate using plants collected from diverse climatic origins, grown under common conditions, potentially provides valuable insights into climate adaptation. We report on fifteen accessions of kangaroo grass ( Themeda triandra ), a C4 species distributed across Australia, Asia, the Middle East and Africa from the Andropogoneae clade of grasses that is vital to global agriculture. Plants were grown to maturity in glasshouses under two thermal regimes, with ample water supplied. Numerous physiological, “economic” and developmental traits were characterised. As expected, plants grown at 20°C maxima had lower photosynthetic rates (A sat ) and dark respiration rates, reduced leaf expansion, and delayed flowering compared with plants grown at 30°C. However, surprisingly few traits varied with climate-of-origin: accessions from colder climates had higher A sat alongside lower leaf mass per area, but only when grown at 20°C; flowering time showed the strongest correlation with site climate, with plants from wetter, warmer or less variable climates taking longer to flower. Our findings highlight remarkable phenotypic flexibility in key traits of T. triandra ; this flexibility is likely key to its wide distribution. The strong relationship between flowering time and climate-of-origin underscores the importance of reproductive phenology as an adaptive trait.

Plants employ multiple strategies to adapt to their growth environment. Characterizing key dimensions in plant trait space is important for understanding functional diversity within ecosystems. Leaf and root functional traits have been studied in the context of resource economics, but whether they covary, and through which mechanisms, is still debated. We investigated this in subtropical forests by sampling root and leaf traits on individuals of co-existing species in two communities with different resource availability. We found largely non-correlated variation between leaf and fine root traits both across and within communities, and a clear decoupling between leaf economic spectrum and root economic space, independent of evolutionary history. Our results suggest that leaf-root trait relationships are shaped by an interplay between microenvironmental heterogeneity that drives decoupling and shared selection pressures promoting covariation. The interplay explains the weak observed coordination and highlights the importance of environmental context in predicting above- and below-ground plant functions.

The sapwood area supporting a given leaf area (Huber value, vH) reflects the coupling between carbon uptake and water transport and loss at a whole-plant level. Geographic variation in vH presumably reflects plant strategic adaptations, but the lack of a general explanation for such variation hinders its representation in vegetation models and assessment of its impact on the global carbon and water cycles. Here we develop a simple hydraulic trait model to predict optimal vH by matching stem water supply and leaf water loss, and test its performance against two extensive plant hydraulic datasets. We show that our eco-evolutionary optimality-based model explains nearly 60% of global vH variation in response to light, vapour pressure deficit, temperature and sapwood conductivity. Enhanced hydraulic efficiency with warmer temperatures reduces the sapwood area required to support a given leaf area, whereas high irradiance (supporting increased photosynthetic capacity) and drier air increase it. This study thus provides a route to modelling variation in functional traits through the coordination of carbon uptake and water transport processes.

BACKGROUND AND AIMS:The C4 Andropogoneae grass, Sorghum bicolor is an important crop for food, forage and biofuel in tropical and subtropical, arid to semi-arid regions worldwide. There are 25 species in Sorghum, providing an important source of genes and traits to guide breeding programs for "future-proofing" sorghum against expected increasing frequency of droughts and heatwaves in coming decades. METHODS:We grew nine Sorghum species native to the northern Australian tropics under controlled glasshouse conditions, measuring traits related to plant performance and tolerances to heat and drought. First, we quantified relationships between traits and climate-at-origin (climate at the location from where each species was sourced), teasing apart the associations with site precipitation and temperature. Second, we quantified relationships between traits and climate niche width (climate range across a species' entire distribution), testing for putative trade-offs between performance and generality. Third, we quantified relationships among the measured traits. KEY RESULTS:Key findings included: (i) Species from drier sites exhibited higher intrinsic water use efficiency; (ii) Species from warmer climates had less negative turgor loss point; (iii) Photosynthetic temperature tolerance, Tcrit, showed quadratic trends with precipitation- and temperature-of-origin. (iv) Species with broader climate niches displayed lower photosynthetic rates under standard conditions yet strong photosynthetic performance across a wider range of leaf temperatures. CONCLUSIONS:Physiological adaptations related to water use and tolerance to water stress were clearly evident in Australian Sorghum. Dry-site species seemingly economise on photosynthetic water use; hot-site species - subject to periods of high evaporative demand - display a drought avoidance strategy (early onset of stomatal closure), protecting tissues against drought-related damage. Heat tolerance traits showed few relationships to climate, or non-linear trends that were difficult to interpret. This study provides valuable insights for understanding climate adaptation among C4 grasses, potentially informing agricultural breeding programs in the context of climate change.

Understanding the role of site climate in driving geographic trait variation and revealing the relative contributions of adaptation and plasticity are key goals in plant sciences. We tested mechanistic hypotheses for trait-climate relationships for mature eucalypt trees grown in common garden and in situ field conditions, quantifying joint and individual effects of mean annual precipitation (MAP) and temperature (MAT) on eight functionally important traits. Trait-MAP relationships were particularly strong, with all but one trait consistently related to precipitation in both growth conditions. Trait-MAT relationships were notably weaker, but where relationships existed, most traits responded to low temperature in the same direction as to low rainfall, as predicted. Comparing cross-species trait-climate relationships in situ with trait-climate-of-origin relationships in the common garden indicated substantial contributions from both adaptation and plasticity, with plasticity contributing more to variation in photosynthetic traits than in leaf structural or wood traits. Two key advances were: teasing apart the roles of site temperature and rainfall on trait variation, which are often confounded; and inferring the contributions of adaptation and plasticity to observed trait patterns. The relative importance of these processes may determine the timescales over which plant traits shift with climate change.

Aims: Australia's coastline is fringed by more than 8000 continental islands. These islands feature a diverse array of landforms, rock and soil types and geological origins. Some of these islands are among the least invaded, most pristine habitats in Australia and support high plant diversity. Here, we present a new Australia-wide curated dataset for plant species occurrences on islands. Results: Combining information from 1349 species lists and floras, A-Islands includes data on > 6500 plant species from 844 islands ranging in size from 18 m(2) to 4400 km(2), exhibiting different degrees of isolation from the mainland, and spanning all major Australian climate zones. Of these, 251 islands have been repeatedly sampled up to 11 times, making it possible to investigate temporal compositional change. A-Islands is open access and will be continuously updated. Its simple data structure, consisting of three comma-separated files allows easy integration with other Australian and global plant-occurrence databases and can serve as a repository for island research in Australia. Conclusions: Knowing which species occur on Australia's islands will provide opportunities for future research, including studying changes in biodiversity and species turnover within and among archipelagos, tests of classical island biogeography theory, and as a baseline for ecological monitoring and conservation.

Indisputably, temperature and precipitation are key environmental variables driving plant trait variation and shaping plant ecological strategies. However, it is challenging to ascertain their relative influences because site temperature and precipitation are often correlated. Here, using Eucalyptus as a model system representing woody evergreen species more broadly, we sought to disentangle their influence on wood anatomical traits underpinning plant hydraulics. From a common garden we sampled 29 pairs of closely-related Eucalyptus species, each species-pair representing either a contrast in site temperature or precipitation, but never both. Very clearly, and both in phylogenetic and non-phylogenetic analyses, species from lower-rainfall and from colder regions had thicker vessel walls, likely an adaptation to drought and freezing, enabling water transport at more negative water potentials with reduced risk of cavitation or vessel implosion. On average, species from warmer regions had smaller vessels, but theoretical hydraulic conductivity remained stable across site temperatures due to increased vessel density compensating for reduced diameters. These trends being observed for adult plants grown under common conditions suggests that key hydraulic anatomy traits are "hard-wired", and gene × environment interactions are relatively weak. This is a key insight for understanding the trait-basis of plant ecological strategies related to site climate.

Accurately representing the relationships between nitrogen supply and photosynthesis is crucial for reliably predicting carbon-nitrogen cycle coupling in Earth System Models (ESMs). Most ESMs assume positive correlations amongst soil nitrogen supply, leaf nitrogen content, and photosynthetic capacity. However, leaf photosynthetic nitrogen demand may influence the leaf nitrogen response to soil nitrogen supply; thus, responses to nitrogen supply are expected to be the largest in environments where demand is the greatest. Using a nutrient addition experiment replicated across 26 sites spanning four continents, we demonstrated that climate variables were stronger predictors of leaf nitrogen content than soil nutrient supply. Leaf nitrogen increased more strongly with soil nitrogen supply in regions with the highest theoretical leaf nitrogen demand, increasing more in colder and drier environments than warmer and wetter environments. Thus, leaf nitrogen responses to nitrogen supply are primarily influenced by climatic gradients in photosynthetic nitrogen demand, an insight that could improve ESM predictions.

Terrestrial plants exhibit immense variation in their form and function among species. Coordination between resource acquisition by roots and reproduction through seeds could promote the fitness of plant populations. How root and seed traits covary has remained unclear until our analysis of the largest-ever compiled joint global dataset of root traits and seed mass. Here we demonstrate that seed mass and seed phosphorus mass scale positively with root diameter in arbuscular mycorrhizal (AM) plants, depending on variation in root cortical thickness instead of root vessel size. These findings suggest a dual role of AM association in phosphorus uptake and pathogen resistance which drives the global root–seed coordination, instead of initially expected resource transport via root vessels as the main driver. In contrast, we found no relationship between root traits and seed mass in ectomycorrhizal plants. Overall, our study reveals coordination between roots and seeds in AM plants, which is probably regulated by root–mycorrhizal symbiosis, and may be crucial in shaping global plant diversity and species distributions. In this study, Yang et al. compile a global dataset to uncover the degree to which plants coordinate root and seed traits. They report a global positive correlation between root diameter and seed size, driven by dual roles of arbuscular mycorrhiza in phosphorus uptake and pathogen defence.

BACKGROUND AND AIMS:Phosphorus (P)-impoverished soils shape plant adaptation in biodiverse ecosystems worldwide, from Australian heathlands to Amazonian rainforests to southern China's karst regions. While non-mycorrhizal lineages like Proteaceae and Cyperaceae use carboxylate exudation that mobilise P, and are celebrated for such strategies, the mechanisms allowing mycorrhizal Myrtaceae-especially eucalypts-to thrive in these soils without fungal assistance remain unclear. Given Myrtaceae's dominance in P-impoverished Australian ecosystems, a key question arises: How do mycorrhizal plants succeed in P-impoverished environments without relying on fungal symbiosis? We challenge the paradigm that carboxylate-driven P acquisition is exclusive to non-mycorrhizal species. METHODS:Using leaf manganese concentrations ([Mn]) as a proxy for carboxylate exudation, we assessed trait diversification across Myrtaceae genera. We collected leaf and soil samples from 34 species of eucalypt (Angophora, Blakella, Corymbia, Eucalyptus) and other Myrtaceae from 18 sites in south-eastern Australia. KEY RESULTS:Our findings reveal consistently high leaf [Mn] in many Myrtaceae, comparable to that in known carboxylate-releasing species, indicating intensive P mining. This suggests convergent evolution of carboxylate exudation in mycorrhizal Myrtaceae, fundamentally reshaping our understanding of nutrient acquisition in symbiotic plants. Significant interspecific variation was observed, with Angophora showing markedly higher [Mn] than Eucalyptus, suggesting divergent P-acquisition strategies within Myrtaceae. Weak phylogenetic signals for leaf [Mn] and [P] in eucalypts imply repeated evolutionary change in these traits, similar to what is known in other Australian species adapted to P scarcity. CONCLUSIONS:By demonstrating carboxylate-driven P mining in mycorrhizal Myrtaceae, we redefine the mechanisms behind their dominance in low-P environments. Trait diversity-linked to variation in carboxylate-mediated P acquisition and plant-soil feedbacks-likely drives niche differentiation and genus-level distribution across south-eastern Australia. Connecting leaf [Mn] to carboxylate-driven P mining advances our understanding of trait evolution in Myrtaceae and provides a framework for predicting plant-soil interactions in P-impoverished ecosystems globally.

The leaf economics spectrum links strategies of plant investment in resource-acquiring leaves to overall fitness. We test whether an economic spectrum can also explain variation in ecological strategies of ant species across environmental gradients, where colony investment in workers is analogous to plant investment in leaves. A fast return of resource investment was associated with large colonies of smaller, less robust, short-lived workers with low nitrogen:phosphorus ratios. Slow resource payback was associated with small colonies of densely built, energetically conservative and longer-lived workers with high nitrogen:phosphorus ratios. Species representing the entire economic continuum co-occurred in all communities. Phylogenetic analyses suggest genus level conservation of core investment templates. These results unify studies of plants and ants, suggesting common economic principles apply across the tree of life.

AimArbuscular mycorrhizas (AM) and ectomycorrhizas (ECM) have different impacts on nutrient cycling, carbon storage, community dynamics and enhancement of photosynthesis by rising CO2. Recent global analyses have concluded that patterns of AM/ECM dominance in forests worldwide are shaped by climate, with soil nutrients contributing negligible additional explanatory power. However, their reliance on nutrient data from GIS surfaces masks important local influences of parent material, topography and soil age on soil nutrient status. We asked if use of site-specific nutrient data reveals a more important role for nutrients.Time PeriodPresent day.LocationGlobal dataset comprising 703 sites, encompassing forests, savanna/woodlands, shrublands and deserts on all continents except Antarctica.Taxa StudiedArborescent plants, including angiosperms, gymnosperms and tree ferns.MethodsGeneralised Additive Models for Location, Scale and Shape (GAMLSS) to determine the effects of climate variables, soil nitrogen and soil phosphorus on the proportional representation of ECM and of non-mycorrhizal species (NM) in woody vegetation.ResultsGAMLSS showed a strong negative relationship of ECM representation with mean annual temperature (MAT), and a strong negative relationship with soil total nitrogen. NM representation was highest on dry sites and phosphorus-poor sites. Reanalysis showed that GIS-derived soil nutrient data had less explanatory power than site-specific nutrient data, and resulted in poorer model fits.ConclusionsOur results support the long-held belief that soil nutrients as well as climate influence the relative fitness of different mycorrhizal syndromes worldwide, and demonstrate the value of using site-specific nutrient data. Soil nutrients should be considered when predicting the impact of climate change on the mycorrhizal composition of vegetation and resulting shifts in ecosystem processes.

Wind is an important ecological factor for plants as it can increase evapotranspiration and cause dehydration. However, the impact of wind on plant hydraulics at a global scale remains unclear. Here we compiled plant key hydraulic traits, including water potential at 50% loss of hydraulic conductivity (P50), xylem-specific hydraulic conductivity (KS), leaf area to sapwood area ratio (AL/AS) and conduit diameter (D) with 2,786 species-at-site combinations across 1,922 woody species at 469 sites worldwide and analysed their correlations with wind speed. Even with other climatic factors controlled (for example, moisture index, temperature and vapour pressure deficit), wind speed clearly affected plant hydraulics; for example, on average, species from windier sites constructed sapwood with smaller D and lower KS that was more resilient to drought (more negative P50), deploying less leaf total area for a given sapwood cross-section. Species with these traits may be at an advantage under future climates with higher wind speeds.

Vegetation productivity is the key process supporting all terrestrial ecosystem services. Predicting the trajectories of change in vegetation productivity against the backdrop of precipitation change is a key challenge. Here, with global satellite datasets of vegetation growth and in-situ observations of productivity at > 2,000 sites, we show that using theory from microeconomics, we can successfully predict how vegetation productivity responds to short-term (inter-annual) and longer-term changes in precipitation. Asymmetric responses of productivity to inter-annual precipitation variability, as well as well-documented spatial patterns of productivity, precipitation-use efficiency, and precipitation sensitivity, are all well explained by this theory when precipitation is considered the limiting resource and vegetation productivity. Our results suggest that evaluating ecosystems from a microeconomics perspective can provide novel insights and improve our understanding, and predictive ability regarding, how vegetation productivity and hence ecosystem carbon sinks may change in the future.

The efflux of carbon dioxide (CO 2 ) from woody stems, a proxy for stem respiration, is a critical carbon flux from ecosystems to the atmosphere, which increases with temperature on short timescales. However, plants acclimate their respiratory response to temperature on longer timescales, potentially weakening the carbon-climate feedback. The magnitude of this acclimation is uncertain despite its importance for predicting future climate change. We develop an optimality-based theory dynamically linking stem respiration with leaf water supply to predict its thermal acclimation. We show that the theory accurately reproduces observations of spatial and seasonal change. We estimate the global value for current annual stem CO 2 efflux as 27.4 ± 5.9 PgC. By 2100, incorporating thermal acclimation reduces projected stem respiration without considering acclimation by 24 to 46%, thus reducing land ecosystem carbon emissions.

Predicting forest responses to climate change requires a detailed understanding of trait-environment coordination. Adaptation to environment comprises both conserved and labile components of trait variation. However, few studies explore the decomposition of trait-environment relationships in a rigorous phylogenetic framework. Combining trait, climate and soil data for an unprecedented number of species (Nspecies = 767, ~85%), we identified patterns of replicated evolution that allowed the evergreen tree genus, Eucalyptus, to rapidly radiate across Australia in response to aridification. Eucalypts from arid regions are short, produce dense wood, and have small, physically robust leaves with high nitrogen content, promoting hydraulic safety and economies in photosynthetic water use. Phylogenetic modelling reveals strong niche conservatism, with adaptation to aridity occurring primarily via clade-level divergences, followed by phylogenetically independent adjustments to local conditions. Ancestral state reconstructions accounting for trends in the paleoclimate record indicate that transitions in aridity tolerance are associated with distinct signals of environmental filtering and directional selection on functional trait variation. However, astonishing repeatability of trait changes in different clades reveals a narrow optimal solution to water availability, opening a path to predict future species distributions from phylogenetically structured trait data and signalling major implications for functional and species diversity under progressive climate change. ### Competing Interest Statement The authors have declared no competing interest.