1. Plants must balance water expenditure from their crown with water supplied through root and stem tissues. Although many different combinations of hydraulic traits could accomplish water balance, we ask whether variation across species in stem hydraulic traits has been concentrated along few, or many, dimensions of trait variation. 2. We measured stem hydraulic traits for 120 woody dicot species across a range of different biomes in eastern Australia. Mean annual temperatures ranged from 10 to 27 °C and aridity (precipitation ⁄ potential evapotranspiration) from 0AE33 to 1AE02 across study sites. 3. Xylem-specific conductivity, species' height and ratio of leaf area to xylem area were positively correlated, manifesting as a single axis of trait variation, with other traits mostly orthogonal to this axis. Thus, as height and ratio of leaf area to xylem area increased across species and habitats (increasing resistance per leaf area), xylem-specific conductivity partially compensated for this resistance. Xylem-specific conductivity was well predicted by increasing height (r 2 = 0AE45) and ratio of leaf area to xylem area (r 2 = 0AE36). This three-trait axis was positively correlated with increasing precipitation (r 2 = 0AE28) and temperature (r 2 = 0AE15), but most of the explained variance lay within sites (39%) rather than across sites (10%). Thus, the spread of species' traits along this functional axis reflected structural and hydraulic differences among co-occurring species, at least as much as it reflected differences associated with contrasting climates. 4. High xylem-specific conductivity in stems was accomplished by high vessel diameter to number ratio (r 2 = 0AE32) and ⁄ or by high vessel lumen fraction (r 2 = 0AE13). Low midday water potential (higher xylem tension) was associated with low ratio of vessel diameter to number (r 2 = 0AE25), whereas low specific gravity (r 2 = 0AE18) and stiffness (r 2 = 0AE12) were associated with high vessel lumen fraction. 5. Light capture (i.e. increasing height and leafiness) may be facilitated by high xylem-specific conductivity, but marked increases in xylem-specific conductivity may also be associated with reduced hydraulic and mechanical safety. Although the trade-offs associated with increasing xylem-specific conductivity remain unclear, our data suggest that xylem-specific conductivity is important for maintaining water balance across a large range of species and biomes.

The widely held assumption that any important scientific information would be available in English underlies the underuse of non-English-language science across disciplines. However, non-English-language science is expected to bring unique and valuable scientific information, especially in disciplines where the evidence is patchy, and for emergent issues where synthesising available evidence is an urgent challenge. Yet such contribution of non-English-language science to scientific communities and the application of science is rarely quantified. Here, we show that non-English-language studies provide crucial evidence for informing global biodiversity conservation. By screening 419,679 peer-reviewed papers in 16 languages, we identified 1,234 non-English-language studies providing evidence on the effectiveness of biodiversity conservation interventions, compared to 4,412 English-language studies identified with the same criteria. Relevant non-English-language studies are being published at an increasing rate in 6 out of the 12 languages where there were a sufficient number of relevant studies. Incorporating non-English-language studies can expand the geographical coverage (i.e., the number of 2° × 2° grid cells with relevant studies) of English-language evidence by 12% to 25%, especially in biodiverse regions, and taxonomic coverage (i.e., the number of species covered by the relevant studies) by 5% to 32%, although they do tend to be based on less robust study designs. Our results show that synthesising non-English-language studies is key to overcoming the widespread lack of local, context-dependent evidence and facilitating evidence-based conservation globally. We urge wider disciplines to rigorously reassess the untapped potential of non-English-language science in informing decisions to address other global challenges. Please see the Supporting information files for Alternative Language Abstracts.

Editor: Linda E. GrahamPremise of research. Plants are faced with a challenge across all climates they inhabit-they must transport water to their leaves so that photosynthesis can take place. Although this is simple in concept, it can be achieved by different arrangements of root, stem, and leaf traits. The hydraulic functioning of species across aridity gradients is determined by the coordination of these traits. Nevertheless, we have an imperfect understanding of which trait shifts are favored across aridity gradients as well as the alignment of trait shifts with climate.Methodology. We measured hydraulic traits relating to Darcy's law for 120 angiosperm species across a broad range of climates in eastern Australia; nearly one-third of all biome space on Earth was represented. We then determined which hydraulic trait shifts have been favored across aridity gradients and which climate characteristics these trait shifts aligned with.Pivotal results. Increasing aridity, from climates with similar precipitation and evaporation to climates where precipitation was only a third of evaporation, was associated with a 4.8-fold decrease in plant height, a 3.0-fold decrease in leaf area-to-sapwood area ratio, and a 3.3-fold decrease in leaf water potential. However, sapwood-specific conductivity decreased by 5.9-fold, more than any other hydraulic trait. Greater sapwoodspecific conductivity (decreasing resistance) at wet sites compensated for increasing resistance and hydraulic demand that was associated with taller plants and leafier shoots. All hydraulic traits were strongly correlated with growth season aridity ( ; ) but were not correlated with maximum aridity. This suggests r 1 0.82 P ! 0.05 that plant hydraulic traits are most responsive to water availability and evaporative demand present during the most suitable months for growth rather than the driest months.Conclusions. We suggest that evolution has equipped plants with various mechanisms to avoid desiccation during the dry season while optimizing hydraulic traits for carbon gain during the growth season.

The widely held assumption that any important scientific information would be available in English underlies the underuse of non-English-language science across disciplines. However, non-English-language science is expected to bring unique and valuable scientific information, especially in disciplines where the evidence is patchy, and for emergent issues where synthesising available evidence is an urgent challenge. Yet such contribution of non-English-language science to scientific communities and the application of science is rarely quantified. Here we show that non-English-language studies provide crucial evidence for informing global biodiversity conservation. By screening 419,680 peer-reviewed papers in 16 languages, we identified 1,234 non-English-language studies providing evidence on the effectiveness of biodiversity conservation interventions, compared to 4,412 English-language studies identified with the same criteria. Relevant non-English-language studies are being published at an increasing rate, and can expand the geographical (by 12-25%) and taxonomic (by 5-32%) coverage of English-language evidence, especially in biodiverse regions, albeit often based on less robust study designs. Our results show that synthesising non-English-language studies is key to overcoming the widespread lack of local, context-dependent evidence and facilitating evidence-based conservation globally. We urge wider disciplines to rigorously reassess the untapped potential of non-English-language science in informing decisions to address other global challenges.

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