Biology subjects

Choat, B.

Publications and source records attributed to Choat, B..

8 recordsLinked to original sources

bioRxiv2026

Lack of co-ordination of stomatal, hydraulic and leaf browning traits in 16 perennial Australian grass species of differing climate origins

Grasslands are vulnerable to increasing drought with global warming, but process-based models lack the mechanistic knowledge required to predict the magnitude of drought impacts. While a plant hydraulics framework has been successful in advancing process understanding of drought responses in trees, and how drought responses vary across rainfall gradients, similar approaches have rarely been applied to grasses. Here, we quantified the progression of key drought response processes in sixteen dominant perennial grasses (seven C3 and nine C4) with differing climatic origins across eastern Australia. We found that stomatal closure, hydraulic impairment and leaf browning occurred concurrently, in contrast to the progressive sequence typically observed in trees. We also found that drought response traits were not correlated with species climate of origin. The early impairment of leaf hydraulic conductance and leaf browning along with the lack of correlation with climate of origin suggest that grasses may employ fundamentally different strategies to adapt to low water availability than trees. These results highlight the need for grass-specific parameterization of drought responses in process-based models.

ecology↗

bioRxiv2025

Linking drought strategy to climate of origin in a widespread C4 grass species: hydraulic traits, xylem anatomy and stomatal behaviour in Themeda triandra

O_LIHydraulic, stomatal and anatomical traits strongly influence drought survival and productivity, but the extent to which these trait-types are coordinated and relate to climate-of-origin in herbaceous species remains poorly understood. C_LIO_LIWe quantified hydraulic, stomatal and anatomical traits in eight populations of Themeda triandra selected from diverse temperature and precipitation regimes across Australia, grown under common conditions and exposed to drought. Trait - climate-of-origin relationships were quantified using multiple linear mixed models. C_LIO_LILeaf xylem embolism resistance (P50) was unrelated to climate-of-origin precipitation. Instead, plants from drier climates exhibited lower maximum stomatal conductance, earlier stomatal closure during drought and higher stomatal safety margins (the difference between water potential at stomatal closure and P50). Plants from warmer climates exhibited greater embolism resistance and higher hydraulic conductance, along with wider vessels and lower vein density, suggesting adaptation to high evaporative demand. C_LIO_LIOur findings highlight two primary hydraulic strategies related to climate-of-origin: 1) conservative water use and drought avoidance in drier climates, and 2) embolism resistance and hydraulic efficiency in warmer climates. These findings provide new insights into the intraspecific differences in traits and adaptive strategies used by C4 grasses to persist in contrasting climates. C_LI

ecology↗

bioRxiv2025

Drought, thermal response and climate-patterning in cuticular conductance of the widespread C4 grass, Themeda triandra

O_LIBackground and Aims: Grasslands underpin global biodiversity, carbon storage, and ecosystem resilience, yet are increasingly threatened by rising temperatures and water scarcity. Understanding how key physiological traits respond to drought and heat is essential for ensuring grassland function under future conditions. Here, we investigated intraspecific variation in leaf cuticular traits--specifically minimum cuticular conductance after stomatal closure (gmin) and its response to temperature--in six Australian accessions of Themeda triandra spanning a wide climatic gradient. We asked whether gmin and its response to drought reflect climate-of-origin and whether the cuticle shows a thermal threshold (Tp) beyond which conductance rises sharply. C_LIO_LIMethods: Plants from six accessions were grown under well-watered (control) glasshouse conditions and then exposed to drought. We measured gmin in both control and drought treatments and assessed the response of gmin to increasing temperature (30-55 {degrees}C) using fresh fully hydrated leaves (control). Climatic data for each site of origin were used to explore trait-environment relationships. C_LIO_LIKey results: Under well-watered conditions, gmin showed no link to climate-of-origin. Under drought, however, gmin displayed clearer climate-linked patterns: accessions from cooler, wetter regions had lower values, contrary to expectations. Drought responses varied strongly among accessions, ranging from marked reductions to significant increases in gmin. With increasing temperature, gmin declined gradually and no accession exhibited a distinct phase transition, indicating a thermally stable cuticle. C_LIO_LIConclusions: Themeda triandra shows considerable intraspecific diversity in gmin and its response to drought. The clearer alignment between climate of origin and gmin measured under drought conditions suggests drought stress is an important filter for gmin expression. These findings provide a physiological basis for identifying genotypes with enhanced resilience for use in grassland conservation and restoration under a warming, drying climate. C_LI

ecology↗

bioRxiv2025

Beyond species means - the intraspecific contribution to global wood density variation

Wood density is central for estimating vegetation carbon storage and a plant functional trait of great ecological and evolutionary importance. However, the global extent of wood density variation is unclear, especially at the intraspecific level. We assembled the most comprehensive wood density collection to date (GWDD v.2), including 109,626 records from 16,829 plant species across woody life forms and biomes. Using the GWDD v.2, we explored the sources of variation in wood density within individuals, within species, and across environmental gradients. Intraspecific variation accounted for up to 15% of overall wood density variation (sd = 0.068 g cm-3). Sapwood densities varied 50% less than heartwood densities, and branchwood densities varied 30% less than trunkwood densities. Individuals in extreme environments (dry, hot, acidic soils) had higher wood density than conspecifics elsewhere (+0.02 g cm-3, [~]4% of the mean). Intraspecific environmental effects strongly tracked interspecific patterns (r = 0.83) but were only 20-30% as large and varied considerably among taxa. Individual plant wood density was difficult to predict (RMSE > 0.08 g cm-3; single-measurement R2 = 0.59). We recommend (i) systematic within-species sampling for local applications, and (ii) expanded taxonomic coverage combined with integrative models for robust estimates across ecological scales.

plant biology↗

bioRxiv2025

A global map of wood density

Wood density influences how quickly woody plants grow, how long they live and how much carbon they store, yet its global variation remains poorly mapped. Here we combined 109,626 wood density measurements from 16,829 species with 300,949 vegetation plots to produce a km-scale map of community-weighted wood density for every woody biome. Our model led to a prediction accuracy 32-51 % higher than previous global products, and a 1.8-3.7-fold wider wood density range (0.28-1.00 g cm-3; global mean: 0.57 g cm-3) than previously assumed. Spatial cross-validation showed low bias ({+/-}2.5 % of the mean), and uncertainties decreased from 20% in poorly sampled drylands and boreal regions to 5% in data-rich temperate forests. Mean annual temperature was the best predictor of community-weighted mean wood density, increasing by 0.01 g cm-3 for every 1{degrees}C change. We deliver a low-bias, high-resolution wood density layer for Earth system models, together with spatially explicit error maps. This study represents a major step forward for carbon accounting and trait-based forecasts of vegetation change.

plant biology↗

bioRxiv2023

The AusTraits Plant Dictionary

Traits with intuitive names, a clear scope and explicit description are essential for all trait databases. Reanalysis of data from a single database, or analyses that integrate data across multiple databases, can only occur if researchers are confident the trait concepts are consistent within and across sources. The lack of a unified, comprehensive resource for plant trait definitions has previously limited the utility of trait databases. Here we describe the AusTraits Plant Dictionary (APD), which extends the trait definitions included in the new trait database AusTraits. The development process of the APD included three steps: review and formalisation of the scope of each trait and the accompanying trait description; addition of trait meta-data; and publication in both human and machine-readable forms. Trait definitions include keywords, references and links to related trait concepts in other databases, and the traits are grouped into a hierarchy for easy searching. As well as improving the usability of AusTraits, the Dictionary will foster the integration of trait data across global and regional plant trait databases.

ecology↗

bioRxiv2021

AusTraits: a curated plant trait database for the Australian flora

We introduce the AusTraits database - a compilation of measurements of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 375 traits across 29230 taxa from field campaigns, published literature, taxonomic monographs, and individual taxa descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological parameters (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual-, species- and genus-level observations coupled to, where available, contextual information on site properties. This data descriptor provides information on version 2.1.0 of AusTraits which contains data for 937243 trait-by-taxa combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data to increase our collective understanding of the Australian flora.

ecology↗

bioRxiv2020

Drought tolerance of Hakea species (Proteaceae) from a range of biomes and life-histories predicted by climatic niche.

Extreme drought conditions across the globe are impacting biodiversity with serious implications for the persistence of native species. However, quantitative data on drought tolerance is not available for diverse flora to inform conservation management. We quantified physiological drought tolerance in the diverse Hakea genus (Proteaceae) to test predictions based on climatic-origin, life history and functional traits. We sampled terminal branches of replicate plants of 16 species in a common garden. Xylem cavitation was induced in branches under varying water potential (tension) in a centrifuge and the tension generating 50% loss of conductivity (stem P50) was characterized as a metric for drought tolerance. The same branches were used to estimate plant functional traits, including wood density, specific leaf area, and Huber value (sap flow area to leaf area ratio). There was significant variation in stem P50 among species, which was negatively associated with the species climate-origin (rainfall and aridity). Drought tolerance did not differ among life histories; however, a drought avoidance strategy with terete leaf form and greater Huber value may be important for species to colonize and persist in the arid biome. Our findings will contribute to future prediction of species vulnerability to drought and adaptive management under climate change.

ecology↗