ORCID Profile
0000-0002-7575-5526
Current Organisation
James Cook University
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Plant Physiology | Ecological Impacts of Climate Change | Plant Biology | Ecosystem Function | Ecological Applications | Terrestrial Ecology | Surfacewater Hydrology | Ecology | Geochemistry | Global Change Biology | Climate Change Processes | Global Change Biology | Isotope Geochemistry | Crop and Pasture Improvement (Selection and Breeding) | Plant Physiology | Terrestrial Ecology | Ecological Physiology
ANZSRC Socio-Economic Objective (SEO)
Ecosystem Adaptation to Climate Change | Forest and Woodlands Flora, Fauna and Biodiversity | Climate Change Models | Flora, Fauna and Biodiversity at Regional or Larger Scales | Ecosystem Assessment and Management of Forest and Woodlands Environments | Climate Change Adaptation Measures | Climate Variability (excl. Social Impacts) | Native forests | Native Forests | Living resources (flora and fauna) | Management of Water Consumption by Plant Production | Land and water management | Physical and Chemical Conditions of Water in Fresh, Ground and Surface Water Environments (excl. Urban and Industrial Use) | Expanding Knowledge in the Environmental Sciences | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in the Biological Sciences |
Related Links
Publications
Direct quantification of leaf transpiration isotopic composition
Publisher: Elsevier BV
Date: 03-2012
Two-Source δ18O Method to Validate the CO18O-Photosynthetic Discrimination Model: Implications for Mesophyll Conductance
Publisher: Oxford University Press (OUP)
Date: 13-09-2019
DOI: 10.1104/PP.19.00633
Lianas and trees exhibit divergent intrinsic water‐use efficiency along elevational gradients in South American and African tropical forests
Publisher: Wiley
Date: 31-08-2021
DOI: 10.1111/GEB.13382
Abstract: Elevational gradients provide excellent opportunities to explore long‐term morphological and physiological responses of plants to environmental change. We determined the difference in the elevational pattern of foliar carbon isotope composition (δ 13 C) between lianas and trees, and assessed whether this difference arises from changes in photosynthesis or stomatal conductance. We also explored the pattern of nutrient limitations with the elevation of these two growth forms. The study was conducted in two mountain forests situated in the Neotropics and Palaeotropics. August–September 2015 and August–October 2016. Lianas and trees. We conducted inventories of lianas and trees using standardized techniques along elevational gradients in Ecuador and Rwanda. We determined the values of several foliar traits including δ 13 C and chemical traits in dominant liana and tree species. We set up Bayesian linear mixed‐effect models to quantify the effects of elevation and growth form on each of the foliar traits , and the difference of the effect of elevation between the two growth forms (lianas and trees). We found consistent growth form specific ergences in foliar δ 13 C and carbon to nitrogen ratio (C : N) responses to elevation. While we noted a meaningful increase in foliar δ 13 C and C : N with elevation for trees, lianas did not exhibit such a trend. Foliar δ 13 C and C : N remained relatively constant for lianas along the transects. Lianas operate at relatively constant intrinsic water‐ and nitrogen‐use efficiencies with elevation compared with trees. Altogether, the study suggests the existence of a functional ergence of water and nutrient use strategies between lianas and trees along tropical elevational transects.
Oxygen isotope exchange between water and carbon dioxide in soils is controlled by pH, nitrate availability and microbial biomass through links to carbonic anhydrase activity
Publisher: Copernicus GmbH
Date: 23-07-2020
DOI: 10.5194/SOIL-2020-44
Abstract: Abstract. The oxygen isotope composition (δ18O) of atmospheric carbon dioxide (CO2) can be used to estimate gross primary production at the ecosystem-scale and above. Understanding how and why the rate of oxygen isotope exchange between soil water and CO2 (kiso) varies can help to reduce uncertainty in the retrieval of such estimates. The expression and activity of carbonic anhydrases in soils are important drivers of variations in kiso. Here we estimate kiso and measure associated soil properties in laboratory incubation experiments using 44 soils s led from sites across western Eurasia and northeastern Australia. Observed kiso exceeded theoretical uncatalysed rates indicating the significant influence of carbonic anhydrases on the variability observed among the soils studied. We identify soil pH as the principal source of variation, with greater kiso under alkaline conditions suggesting that shifts in microbial community composition or intra-extra cellular dissolved inorganic carbon gradients induce the expression of more or higher activity forms of carbonic anhydrases. We also show for the first time in soils that the presence of nitrate under acidic conditions reduces kiso, potentially reflecting the direct or indirect inhibition of carbonic anhydrases. This effect was confirmed by a supplementary ammonium nitrate fertilisation experiment conducted on a subset of the soils. Future changes in atmospheric nitrogen deposition or land-use may thus influence carbonic anhydrase activity. Greater microbial biomass also increased kiso under a given set of chemical conditions likely highlighting the ubiquity of carbonic anhydrase expression by soil microbial communities. These data provide the most extensive analysis of spatial variations in soil kiso to date and indicate key controls required to predict variations in kiso at the scales needed to improve efforts to constrain gross primary productivity using the δ18O of atmospheric CO2.
The Role of Hydraulic Failure in a Massive Mangrove Die-Off Event
Publisher: Frontiers Media SA
Date: 27-04-2022
Abstract: Between late 2015 and early 2016, more than 7,000 ha of mangrove forest died along the coastline of the Gulf of Carpentaria, in northern Australia. This massive die-off was preceded by a strong 2015/2016 El Niño event, resulting in lower precipitation, a drop in sea level and higher than average temperatures in northern Australia. In this study, we investigated the role of hydraulic failure in the mortality and recovery of the dominant species, Avicennia marina , 2 years after the mortality event. We measured predawn water potential (Ψ pd ) and percent loss of stem hydraulic conductivity (PLC) in surviving in iduals across a gradient of impact. We also assessed the vulnerability to drought-induced embolism (Ψ 50 ) for the species. Areas with severe canopy dieback had higher native PLC (39%) than minimally impacted areas (6%), suggesting that hydraulic recovery was ongoing. The high resistance of A. marina to water-stress-induced embolism (Ψ 50 = −9.6 MPa), indicates that severe water stress (Ψ pd & −10 MPa) would have been required to cause mortality in this species. Our data indicate that the natural gradient of water-stress enhanced the impact of El Niño, leading to hydraulic failure and mortality in A. marina growing on severely impacted (SI) zones. It is likely that lowered sea levels and less frequent inundation by seawater, combined with lower inputs of fresh water, high evaporative demand and high temperatures, led to the development of hyper-salinity and extreme water stress during the 2015/16 summer.
Photosynthetic refixation in branches of Western White Pine
Publisher: Wiley
Date: 06-2000
Physiological and isotopic (δ13C and δ18O) responses of three tropical tree species to water and nutrient availability
Publisher: Wiley
Date: 07-09-2009
DOI: 10.1111/J.1365-3040.2009.02010.X
Abstract: Water-use efficiency and stable isotope composition were studied in three tropical tree species. Seedlings of Tectona grandis, Swietenia macrophylla and Platymiscium pinnatum were grown at either high or low water supply, and with or without added fertilizer. These three species previously exhibited low, intermediate and high whole-plant water-use efficiency (TE) when grown at high water supply in unfertilized soil. Responses of TE to water and nutrient availability varied among species. The TE was calculated as experiment-long dry matter production ided by cumulative water use. Species-specific offsets were observed in relationships between TE and whole-plant (13)C discrimination (Delta(13)C(p)). These offsets could be attributed to a breakdown in the relationship between Delta(13)C(p) and the ratio of intercellular to ambient CO(2) partial pressures (c(i)/c(a)) in P. pinnatum, and to variation among species in the leaf-to-air vapour pressure difference (v). Thus, a plot of v.TE against c(i)/c(a) showed a general relationship among species. Relationships between delta(18)O of stem dry matter and stomatal conductance ranged from strongly negative for S. macrophylla to no relationship for T. grandis. Results suggest inter-specific variation among tropical tree species in relationships between stable isotope ratios (delta(13)C and delta(18)O) and the gas exchange processes thought to affect them.
Assessing the Australian Termite Diversity Anomaly: How Habitat and Rainfall Affect Termite Assemblages
Publisher: Frontiers Media SA
Date: 23-04-2021
Abstract: Termites are important ecosystem engineers in tropical habitats, with different feeding groups able to decompose wood, grass, litter, and soil organic matter. In most tropical regions, termite abundance and species ersity are assumed to increase with rainfall, with highest levels found in rainforests. However, in the Australian tropics, this pattern is thought to be reversed, with lower species richness and termite abundance found in rainforest than drier habitats. The potential mechanisms underlying this pattern remain unclear. We compared termite assemblages (abundance, activity, ersity, and feeding group composition) across five sites along a precipitation gradient (ranging from ∼800 to 4,000 mm annual rainfall), spanning dry and wet savanna habitats, wet sclerophyll, and lowland and upland rainforests in tropical North Queensland. Moving from dry to wet habitats, we observed dramatic decreases in termite abundance in both mounds and dead wood occupancy, with greater abundance and activity at savanna sites (low precipitation) compared with rainforest or sclerophyll sites (high precipitation). We also observed a turnover in termite species and feeding group ersity across sites that were close together, but in different habitats. Termite species and feeding group richness were highest in savanna sites, with 13 termite species from wood-, litter-, grass-, dung-, and soil-feeding groups, while only five termite species were encountered in rainforest and wet sclerophyll sites—all wood feeders. These results suggest that the Australian termite ersity anomaly may be partly driven by how specific feeding groups colonized habitats across Australia. Consequently, termites in Australian rainforests may be less important in ecosystem processes, such as carbon and nutrient cycling during decomposition, compared with termites in other tropical rainforests.
NAVKIDS2 trial: a multi-centre, waitlisted randomised controlled trial of a patient navigator intervention in children with chronic kidney disease — statistical analysis plan and update to the protoco
Publisher: Springer Science and Business Media LLC
Date: 30-09-2022
DOI: 10.1186/S13063-022-06783-Y
Abstract: This update summarises key changes made to the protocol since the publication of the original protocol for the NAVKIDS 2 trial of patient navigators for children with chronic kidney disease (CKD) experiencing social disadvantage and provides the statistical analysis plan (SAP) which has not previously been published. The original protocol was published in BMC Nephrology ( 0.1186/s12882-019-1325-y ) prior to the commencement of trial recruitment. During the course of the trial, some key methodological changes needed to be made including changes to eligibility criteria (addition of patients with CKD stages 1–2, broadening of financial status eligibility criterion, addition of patients living in rural/remote areas, modification of age eligibility to 0–16 years, addition of limits related to the language spoken by family, guidance regarding families with multiple eligible children), changes to sites, reduction of s le size, addition of virtual options for consent and study procedures in response to the COVID-19 pandemic, removal of staggered recruitment across sites, addition of outcomes, and changes to the timing and number of assessments. This update summarises the changes made and their rationale and provides the detailed plan for statistical analysis of the trial. These changes have been finalised prior to the completion of study follow-up and the commencement of data analysis. Australian New Zealand Clinical Trials Registry (ANZCTR) ACTRN12618001152213 . Prospectively registered on 12 July 2018
Wood traits explain microbial but not termite‐driven decay in Australian tropical rainforest and savanna
Publisher: Wiley
Date: 15-03-2023
Abstract: Variation in decay rates across woody species is a key uncertainty in predicting the fate of carbon stored in deadwood, especially in the tropics. Quantifying the relative contributions of biotic decay agents, particularly microbes and termites, under different climates and across species with erse wood traits could help explain this variation. To fill this knowledge gap, we deployed woody stems from 16 plant species native to either rainforest ( n = 10) or savanna ( n = 6) in northeast Australia, with and without termite access. For comparison, we also deployed standardized, non‐native pine blocks at both sites. We hypothesized that termites would increase rates of deadwood decay under conditions that limit microbial activity. Specifically, termite contributions to wood decay should be greater under dry conditions and in wood species with traits that constrain microbial decomposers. Termite discovery of stems was surprisingly low with only 17.6% and 22.6% of accessible native stems discovered in the rainforest and savanna respectively. Contrary to our hypothesis, stems discovered by termites decomposed faster only in the rainforest. Termites discovered and decayed pine blocks at higher rates than native stems in both the rainforest and savanna. We found significant variation in termite discovery and microbial decay rates across native wood species within the same site. Although wood traits explained 85% of the variation in microbial decay, they did not explain termite‐driven decay. For stems undiscovered by termites, decay rates were greater in species with higher wood nutrient concentrations and syringyl:guiacyl lignin ratios but lower carbon concentrations and wood densities. Synthesis . Ecosystem‐scale predictions of deadwood turnover and carbon storage should account for the impact of wood traits on decomposer communities. In tropical Australia, termite‐driven decay was lower than expected for native wood on the ground. Even if termites are present, they may not always increase decomposition rates of fallen native wood in tropical forests. Our study shows how the drivers of wood decay differ between Australian tropical rainforest and savanna further research should test whether such differences apply world‐wide.
Optimal stomatal behaviour around the world
Publisher: Springer Science and Business Media LLC
Date: 02-03-2015
DOI: 10.1038/NCLIMATE2550
Microwave extraction–isotope ratio infrared spectroscopy (ME‐IRIS): a novel technique for rapid extraction and in‐line analysis of δ18O and δ2H values of water in plants, soils a
Publisher: Wiley
Date: 09-2014
DOI: 10.1002/RCM.7005
Abstract: Traditionally, stable isotope analysis of plant and soil water has been a technically challenging, labour-intensive and time-consuming process. Here we describe a rapid single-step technique which combines Microwave Extraction with Isotope Ratio Infrared Spectroscopy (ME-IRIS). Plant, soil and insect water is extracted into a dry air stream by microwave irradiation within a sealed vessel. The water vapor thus produced is carried to a cooled condensation chamber, which controls the water vapor concentration and flow rate to the spectrometer. Integration of the isotope signals over the whole analytical cycle provides quantitative δ(18)O and δ(2) H values for the initial liquid water contained in the s le. Calibration is carried out by the analysis of water standards using the same apparatus. Analysis of leaf and soil water by cryogenic vacuum distillation and IRMS was used to validate the ME-IRIS data. Comparison with data obtained by cryogenic distillation and IRMS shows that the new technique provides accurate water isotope data for leaves from a range of field-grown tropical plant species. However, two exotic nursery plants were found to suffer from spectral interferences from co-extracted organic compounds. The precision for extracted leaf, stem, soil and insect water was typically better than ±0.3 ‰ for δ(18)O and ±2 ‰ for δ(2) H values, and better than ±0.1 ‰ for δ(18)O and ±1 ‰ for δ(2) H values when analyzing water standards. The effects of s le size, microwave power and duration and s le-to-s le memory on isotope values were assessed. ME-IRIS provides rapid and low-cost extraction and analysis of δ(18)O and δ(2) H values in plant, soil and insect water (≈10-15 min for s les yielding ≈ 0.3 mL of water). The technique can accommodate whole leaves of many plant species.
Storage and transpiration have negligible effects on 13C of stem CO2 efflux in large conifer trees
Publisher: Oxford University Press (OUP)
Date: 19-10-2009
Abstract: Stem respiration rates are often quantified by measuring the CO(2) efflux from stems into chambers. It has been suggested that these measurements underestimate respiration because some of the respired CO(2) can be either retained or transported upwards in the transpiration stream. If the stem CO(2) efflux does not represent all respired CO(2), then the interpretation of its isotopic signal may be compromised as well. The C-isotope composition of the respired CO(2) and the measured efflux could differ due to (i) the release of CO(2) produced elsewhere into the stem and transported upwards in xylem water (soil CO(2) or root respired CO(2)) (ii) the retention or release of CO(2) storage pools within the tree stem and (iii) the removal of CO(2) by the transpiration stream. We investigated the effects of these processes in large conifer trees using two manipulative experiments: a labelling experiment and a crown removal experiment. The labelling experiment used an extreme enrichment of dissolved CO(2) in soil water to assess the C uptake by the roots. In this experiment, we found no contamination of the stem CO(2) pool despite clear evidence that the water itself had been taken up. The crown removal experiment tested for vertical CO(2) flux in xylem water by eliminating transpiration. Here, we found no change in the delta(13)C of stem CO(2) efflux (delta(EA) P > 0.05). We concluded that for these large conifers, sap-flow influenced neither delta(13)C of stem efflux nor that of the stem CO(2) pool. By parameterizing Henry's Law for conditions inside the stem, we estimated the transport flux to represent 1-3% of the stem CO(2) efflux to the atmosphere. Finally, assuming a 2 per thousand difference between delta(13)C of root and stem respiration, we estimated that potential contamination of delta(EA) by root respired CO(2) would be < 0.1 per thousand. Thus, neither the release of soil or root CO(2), nor storage in the stem, nor vertical transport of CO(2) in the xylem sap had any detectable influence on delta(13)C of the CO(2) measured in stem efflux.
Examining ozone susceptibility in the genus Musa (bananas)
Publisher: CSIRO Publishing
Date: 2023
DOI: 10.1071/FP22293
Why are tropical conifers disadvantaged in fertile soils? Comparison of Podocarpus guatemalensis with an angiosperm pioneer, Ficus insipida
Publisher: Oxford University Press (OUP)
Date: 03-03-2020
Abstract: Conifers are, for the most part, competitively excluded from tropical rainforests by angiosperms. Where they do occur, conifers often occupy sites that are relatively infertile. To gain insight into the physiological mechanisms by which angiosperms outcompete conifers in more productive sites, we grew seedlings of a tropical conifer (Podocarpus guatemalensis Standley) and an angiosperm pioneer (Ficus insipida Willd.) with and without added nutrients, supplied in the form of a slow-release fertilizer. At the conclusion of the experiment, the dry mass of P. guatemalensis seedlings in fertilized soil was approximately twofold larger than that of seedlings in unfertilized soil on the other hand, the dry mass of F. insipida seedlings in fertilized soil was ~20-fold larger than seedlings in unfertilized soil. The higher relative growth rate of F. insipida was associated with a larger leaf area ratio and a higher photosynthetic rate per unit leaf area. Higher overall photosynthetic rates in F. insipida were associated with an approximately fivefold larger stomatal conductance than in P. guatemalensis. We surmise that a higher whole-plant hydraulic conductance in the vessel bearing angiosperm F. insipida enabled higher leaf area ratio and higher stomatal conductance per unit leaf area than in the tracheid bearing P. guatemalensis, which enabled F. insipida to capitalize on increased photosynthetic capacity driven by higher nitrogen availability in fertilized soil.
Isotopic and morphologic proxies for reconstructing light environment and leaf function of fossil leaves: a modern calibration in the Daintree Rainforest, Australia
Publisher: Wiley
Date: 08-2020
DOI: 10.1002/AJB2.1523
Inferring foliar water uptake using stable isotopes of water
Publisher: Springer Science and Business Media LLC
Date: 22-07-2017
DOI: 10.1007/S00442-017-3917-1
Abstract: A growing number of studies have described the direct absorption of water into leaves, a phenomenon known as foliar water uptake. The resultant increase in the amount of water in the leaf can be important for plant function. Exposing leaves to isotopically enriched or depleted water sources has become a common method for establishing whether or not a plant is capable of carrying out foliar water uptake. However, a careful inspection of our understanding of the fluxes of water isotopes between leaves and the atmosphere under high humidity conditions shows that there can clearly be isotopic exchange between the two pools even in the absence of a change in the mass of water in the leaf. We provide experimental evidence that while leaf water isotope ratios may change following exposure to a fog event using water with a depleted oxygen isotope ratio, leaf mass only changes when leaves are experiencing a water deficit that creates a driving gradient for the uptake of water by the leaf. Studies that rely on stable isotopes of water as a means of studying plant water use, particularly with respect to foliar water uptake, must consider the effects of these isotopic exchange processes.
Relationship between leaf functional traits and productivity in Aquilaria crassna (Thymelaeaceae) plantations: a tool to aid in the early selection of high-yielding trees
Publisher: Oxford University Press (OUP)
Date: 15-02-2017
Abstract: Physiological traits are frequently used as indicators of tree productivity. Aquilaria species growing in a research planting were studied to investigate relationships between leaf-productivity traits and tree growth. Twenty-eight trees were selected to measure isotopic composition of carbon (δ13C) and nitrogen (δ15N) and monitor six leaf attributes. Trees were s led randomly within each of four diametric classes (at 150 mm above ground level) ensuring the variability in growth of the whole population was represented. A model averaging technique based on the Akaike's information criterion was computed to identify whether leaf traits could assist in diameter prediction. Regression analysis was performed to test for relationships between carbon isotope values and diameter and leaf traits. Approximately one new leaf per week was produced by a shoot. The rate of leaf expansion was estimated as 1.45 mm day-1. The range of δ13C values in leaves of Aquilaria species was from -25.5‰ to -31‰, with an average of -28.4 ‰ (±1.5‰ SD). A moderate negative correlation (R2 = 0.357) between diameter and δ13C in leaf dry matter indicated that in iduals with high intercellular CO2 concentrations (low δ13C) and associated low water-use efficiency sustained rapid growth. Analysis of the 95% confidence of best-ranked regression models indicated that the predictors that could best explain growth in Aquilaria species were δ13C, δ15N, petiole length, number of new leaves produced per week and specific leaf area. The model constructed with these variables explained 55% (R2 = 0.55) of the variability in stem diameter. This demonstrates that leaf traits can assist in the early selection of high-productivity trees in Aquilaria species.
Towards species-level forecasts of drought-induced tree mortality risk
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-8249
Abstract: Australia is the driest inhabited continent. Annual rainfall is low and is accompanied by marked inter-annual variability, leading to multi-year droughts. n particular, & #8203 South-East Australia& #8203 & #8203 has recently experienced two of the worst droughts in the historical record (2000& #8211 and 2017& #8211 ). Predicting species-level responses to drought at the landscape scale is critical to reducing uncertainty in future terrestrial carbon and water cycle projections. We embedded a stomatal optimisation model in the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model and parameterised the model for 15 canopy-dominant eucalypt tree species across South-Eastern Australia (mean annual precipitation range: 344& #8211 mm yr-1). We carried out three experiments: applying CABLE to the recent drought a theoretical future drier drought (20% reduction in rainfall) and a future drier drought (20% reduction in rainfall) with a doubling of atmospheric carbon dioxide (CO2). The drought's severity was highlighted as at least 25% of their distribution ranges, and 60% of species experienced leaf water potentials beyond the water potential at which 50% of hydraulic conductivity is lost due to embolism. We identified areas of severe hydraulic stress within species& #8217 ranges, but we also pinpointed resilience in species found in predominantly semiarid regions. The importance of the role of CO2 in ameliorating drought stress was consistent across species. Our results represent an important advance in our capacity to forecast the resilience of in idual tree species, providing an evidence base for decision-making around the resilience of restoration plantings or net-zero emission strategies.
Unsaturation of vapour pressure inside leaves of two conifer species
Publisher: Springer Science and Business Media LLC
Date: 16-05-2018
DOI: 10.1038/S41598-018-25838-2
Abstract: Stomatal conductance ( g s ) impacts both photosynthesis and transpiration, and is therefore fundamental to the global carbon and water cycles, food production, and ecosystem services. Mathematical models provide the primary means of analysing this important leaf gas exchange parameter. A nearly universal assumption in such models is that the vapour pressure inside leaves ( e i ) remains saturated under all conditions. The validity of this assumption has not been well tested, because so far e i cannot be measured directly. Here, we test this assumption using a novel technique, based on coupled measurements of leaf gas exchange and the stable isotope compositions of CO 2 and water vapour passing over the leaf. We applied this technique to mature in iduals of two semiarid conifer species. In both species, e i routinely dropped below saturation when leaves were exposed to moderate to high air vapour pressure deficits. Typical values of relative humidity in the intercellular air spaces were as low 0.9 in Juniperus monosperma and 0.8 in Pinus edulis . These departures of e i from saturation caused significant biases in calculations of g s and the intercellular CO 2 concentration. Our results refute the longstanding assumption of saturated vapour pressure in plant leaves under all conditions.
Acclimation and adaptation components of the temperature dependence of plant photosynthesis at the global scale
Publisher: Wiley
Date: 08-02-2019
DOI: 10.1111/NPH.15668
Abstract: 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 CO
Wood microclimate as a predictor of carbon dioxide fluxes from deadwood in tropical Australia
Publisher: Copernicus GmbH
Date: 13-09-2023
Global climate and nutrient controls of photosynthetic capacity
Publisher: Springer Science and Business Media LLC
Date: 12-04-2021
DOI: 10.1038/S42003-021-01985-7
Abstract: There is huge uncertainty about how global exchanges of carbon between the atmosphere and land will respond to continuing environmental change. A better representation of photosynthetic capacity is required for Earth System models to simulate carbon assimilation reliably. Here we use a global leaf-trait dataset to test whether photosynthetic capacity is quantitatively predictable from climate, based on optimality principles and to explore how this prediction is modified by soil properties, including indices of nitrogen and phosphorus availability, measured in situ. The maximum rate of carboxylation standardized to 25 °C ( V cmax25 ) was found to be proportional to growing-season irradiance, and to increase—as predicted—towards both colder and drier climates. In idual species’ departures from predicted V cmax25 covaried with area-based leaf nitrogen ( N area ) but community-mean V cmax25 was unrelated to N area , which in turn was unrelated to the soil C:N ratio. In contrast, leaves with low area-based phosphorus ( P area ) had low V cmax25 (both between and within communities), and P area increased with total soil P. These findings do not support the assumption, adopted in some ecosystem and Earth System models, that leaf-level photosynthetic capacity depends on soil N supply. They do, however, support a previously-noted relationship between photosynthesis and soil P supply.
Author Correction: Nitrogen and phosphorus constrain the CO2 fertilization of global plant biomass
Publisher: Springer Science and Business Media LLC
Date: 26-05-2020
Transpiration efficiency of a tropical pioneer tree (Ficus insipida) in relation to soil fertility
Publisher: Oxford University Press (OUP)
Date: 10-2007
DOI: 10.1093/JXB/ERM201
Abstract: The response of whole-plant water-use efficiency, termed transpiration efficiency (TE), to variation in soil fertility was assessed in a tropical pioneer tree, Ficus insipida Willd. Measurements of stable isotope ratios (delta(13)C, delta(18)O, delta(15)N), elemental concentrations (C, N, P), plant growth, instantaneous leaf gas exchange, and whole-plant water use were used to analyse the mechanisms controlling TE. Plants were grown in idually in 19 l pots with non-limiting soil moisture. Soil fertility was altered by mixing soil with varying proportions of rice husks, and applying a slow release fertilizer. A large variation was observed in leaf photosynthetic rate, mean relative growth rate (RGR), and TE in response to experimental treatments these traits were well correlated with variation in leaf N concentration. Variation in TE showed a strong dependence on the ratio of intercellular to ambient CO(2) mole fractions (c(i)/c(a)) both for instantaneous measurements of c(i)/c(a) (R(2)=0.69, P <0.0001, n=30), and integrated estimates based on C isotope discrimination (R(2)=0.88, P <0.0001, n=30). On the other hand, variations in the leaf-to-air humidity gradient, unproductive water loss, and respiratory C use probably played only minor roles in modulating TE in the face of variable soil fertility. The pronounced variation in TE resulted from a combination of the strong response of c(i)/c(a) to leaf N, and inherently high values of c(i)/c(a) for this tropical tree species these two factors conspired to cause a 4-fold variation among treatments in (1-c(i)/c(a)), the term that actually modifies TE. Results suggest that variation in plant N status could have important implications for the coupling between C and water exchange in tropical forest trees.
Preface: advances in modelling photosynthetic processes in terrestrial plants
Publisher: Springer Science and Business Media LLC
Date: 17-06-2019
Fire in Australian savannas: from leaf to landscape
Publisher: Wiley
Date: 09-09-2014
DOI: 10.1111/GCB.12686
Abstract: Savanna ecosystems comprise 22% of the global terrestrial surface and 25% of Australia (almost 1.9 million km 2 ) and provide significant ecosystem services through carbon and water cycles and the maintenance of bio ersity. The current structure, composition and distribution of Australian savannas have coevolved with fire, yet remain driven by the dynamic constraints of their bioclimatic niche. Fire in Australian savannas influences both the biophysical and biogeochemical processes at multiple scales from leaf to landscape. Here, we present the latest emission estimates from Australian savanna biomass burning and their contribution to global greenhouse gas budgets. We then review our understanding of the impacts of fire on ecosystem function and local surface water and heat balances, which in turn influence regional climate. We show how savanna fires are coupled to the global climate through the carbon cycle and fire regimes. We present new research that climate change is likely to alter the structure and function of savannas through shifts in moisture availability and increases in atmospheric carbon dioxide, in turn altering fire regimes with further feedbacks to climate. We explore opportunities to reduce net greenhouse gas emissions from savanna ecosystems through changes in savanna fire management.
Coupled rainfall and water vapour stable isotope time series reveal tropical atmospheric processes on multiple timescales
Publisher: Wiley
Date: 12-09-2019
DOI: 10.1002/HYP.13576
The role of topography and plant functional traits in determining tropical reforestation success
Publisher: Wiley
Date: 22-10-2018
Elevated temperature and CO2 cause differential growth stimulation and drought survival responses in eucalypt species from contrasting habitats
Publisher: Oxford University Press (OUP)
Date: 11-2019
Abstract: Climate change scenarios predict increasing atmospheric CO2 concentrations ([CO2]), temperatures and droughts in tropical regions. In idually, the effects of these climate factors on plants are well established, whereas experiments on the interactive effects of a combination of factors are rare. Moreover, how these environmental factors will affect tree species along a wet to dry gradient (e.g., along tropical forest–savanna transitions) remains to be investigated. We hypothesized that under the simulated environmental conditions, plant growth, physiological performance and survivorship would vary in a manner consistent with the species’ positions of origin along this gradient. In a glasshouse experiment, we raised seedlings of three Eucalyptus species, each occurring naturally in a wet forest, savanna and forest–savanna ecotone, respectively. We evaluated the effect of drought, elevated temperature (4 °C above ambient glasshouse temperature of 22 °C) and elevated temperature in combination with elevated [CO2] (400 ppm [CO2] above ambient of 400 ppm), on seedling growth, survivorship and physiological responses (photosynthesis, stomatal conductance and water-use efficiency). Elevated temperature under ambient [CO2] had little effect on growth, biomass and plant performance of well-watered seedlings, but hastened mortality in drought-affected seedlings, affecting the forest and ecotone more strongly than the savanna species. In contrast, elevated [CO2] in combination with elevated temperatures delayed the appearance of drought stress symptoms and enhanced survivorship in drought-affected seedlings, with the savanna species surviving the longest, followed by the ecotone and forest species. Elevated [CO2] in combination with elevated temperatures also enhanced growth and biomass and photosynthesis in well-watered seedlings of all species, but modified shoot:root biomass partitioning and stomatal conductance differentially across species. Our study highlights the need for a better understand of the interactive effects of elevated [CO2], temperature and drought on plants and the potential to upscale these insights for understanding biome changes.
Relative roles of termites and saprotrophic microbes as drivers of wood decay: A wood block test
Publisher: Wiley
Date: 15-12-2017
DOI: 10.1111/AEC.12561
Global variability in leaf respiration in relation to climate, plant functional types and leaf traits
Publisher: Wiley
Date: 05-08-0008
DOI: 10.1111/NPH.13253
Abstract: Leaf dark respiration ( R dark ) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of R dark and associated leaf traits. Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed‐effects models were used to disentangle sources of variation in R dark . Area‐based R dark at the prevailing average daily growth temperature ( T ) of each site increased only twofold from the Arctic to the tropics, despite a 20°C increase in growing T (8–28°C). By contrast, R dark at a standard T (25°C, R dark 25 ) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher R dark 25 at a given photosynthetic capacity ( V cmax 25 ) or leaf nitrogen concentration ([N]) than species at warmer sites. R dark 25 values at any given V cmax 25 or [N] were higher in herbs than in woody plants. The results highlight variation in R dark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of R dark in terrestrial biosphere models (TBMs) and associated land‐surface components of Earth system models (ESMs).
Nitrogen and phosphorus constrain the CO2 fertilization of global plant biomass
Publisher: Springer Science and Business Media LLC
Date: 12-08-2019
Plant responses to rising vapor pressure deficit
Publisher: Wiley
Date: 20-03-2020
DOI: 10.1111/NPH.16485
Delayed greening during leaf expansion under ambient and elevated CO2 in tropical tree seedlings
Publisher: Wiley
Date: 10-12-2021
DOI: 10.1111/AEC.13139
Abstract: Tropical tree species employ varying strategies in young leaves to minimise losses to herbivory. The young leaves of species with delayed greening are thought to be less visible to herbivores, but likely incur a cost to leaf‐level carbon gain via lower photosynthetic rates during leaf development. Increasing atmospheric CO 2 concentrations may reduce the cost of delayed greening, and/or modify leaf expansion rates, altering the ecological interaction of species. In this study, we evaluated the effects of elevated CO 2 concentrations on physiological responses of three Australian rainforest tree species, two with delayed greening in young leaves. Net photosynthesis rates were significantly lower in recently flushed leaves of species with delayed greening than in the species with normal greening. Yet, surprisingly, total nitrogen concentrations were higher in the former than in the latter. Intrinsic water‐use efficiency increased at a steeper rate during leaf development under elevated CO 2 in all three species, irrespective of greening strategy. Leaf growth rate, in terms of area expansion, did not increase under elevated CO 2 in any of the species. Although elevated CO 2 did not boost the performance of the delayed greening species more than that of the normal greening species, we found higher nitrogen concentrations in their young leaves. This supports the intriguing possibility that delayed greening may have evolved in these species to protect young leaves that are especially rich in nitrogen.
Tropical tree mortality has increased with rising atmospheric water stress
Publisher: Springer Science and Business Media LLC
Date: 18-05-2022
DOI: 10.1038/S41586-022-04737-7
Abstract: Evidence exists that tree mortality is accelerating in some regions of the tropics
Thirty-eight years of CO<sub>2</sub> fertilization has outpaced growing aridity to drive greening of Australian woody ecosystems
Publisher: Copernicus GmbH
Date: 28-01-2022
Abstract: Abstract. Climate change is projected to increase the imbalance between the supply (precipitation) and atmospheric demand for water (i.e., increased potential evapotranspiration), stressing plants in water-limited environments. Plants may be able to offset increasing aridity because rising CO2 increases water use efficiency. CO2 fertilization has also been cited as one of the drivers of the widespread “greening” phenomenon. However, attributing the size of this CO2 fertilization effect is complicated, due in part to a lack of long-term vegetation monitoring and interannual- to decadal-scale climate variability. In this study we asked the question of how much CO2 has contributed towards greening. We focused our analysis on a broad aridity gradient spanning eastern Australia's woody ecosystems. Next we analyzed 38 years of satellite remote sensing estimates of vegetation greenness (normalized difference vegetation index, NDVI) to examine the role of CO2 in ameliorating climate change impacts. Multiple statistical techniques were applied to separate the CO2-attributable effects on greening from the changes in water supply and atmospheric aridity. Widespread vegetation greening occurred despite a warming climate, increases in vapor pressure deficit, and repeated record-breaking droughts and heat waves. Between 1982–2019 we found that NDVI increased (median 11.3 %) across 90.5 % of the woody regions. After masking disturbance effects (e.g., fire), we statistically estimated an 11.7 % increase in NDVI attributable to CO2, broadly consistent with a hypothesized theoretical expectation of an 8.6 % increase in water use efficiency due to rising CO2. In contrast to reports of a weakening CO2 fertilization effect, we found no consistent temporal change in the CO2 effect. We conclude rising CO2 has mitigated the effects of increasing aridity, repeated record-breaking droughts, and record-breaking heat waves in eastern Australia. However, we were unable to determine whether trees or grasses were the primary beneficiary of the CO2-induced change in water use efficiency, which has implications for projecting future ecosystem resilience. A more complete understanding of how CO2-induced changes in water use efficiency affect trees and non-tree vegetation is needed.
A reporting format for leaf-level gas exchange data and metadata
Publisher: Elsevier BV
Date: 03-2021
Responses of Legume Versus Nonlegume Tropical Tree Seedlings to Elevated CO2 Concentration
Publisher: Oxford University Press (OUP)
Date: 25-07-2011
Abstract: We investigated responses of growth, leaf gas exchange, carbon-isotope discrimination, and whole-plant water-use efficiency (W P) to elevated CO2 concentration ([CO2]) in seedlings of five leguminous and five nonleguminous tropical tree species. Plants were grown at CO2 partial pressures of 40 and 70 Pa. As a group, legumes did not differ from nonlegumes in growth response to elevated [CO2]. The mean ratio of final plant dry mass at elevated to ambient [CO2] (M E/M A) was 1.32 and 1.24 for legumes and nonlegumes, respectively. However, there was large variation in M E/M A among legume species (0.92–2.35), whereas nonlegumes varied much less (1.21–1.29). Variation among legume species in M E/M A was closely correlated with their capacity for nodule formation, as expressed by nodule mass ratio, the dry mass of nodules for a given plant dry mass. W P increased markedly in response to elevated [CO2] in all species. The ratio of intercellular to ambient CO2 partial pressures during photosynthesis remained approximately constant at ambient and elevated [CO2], as did carbon isotope discrimination, suggesting that W P should increase proportionally for a given increase in atmospheric [CO2]. These results suggest that tree legumes with a strong capacity for nodule formation could have a competitive advantage in tropical forests as atmospheric [CO2] rises and that the water-use efficiency of tropical tree species will increase under elevated [CO2].
Assessing the CO2 concentration at the surface of photosynthetic mesophyll cells
Publisher: Wiley
Date: 12-03-2023
DOI: 10.1111/NPH.18784
Abstract: We present a robust estimation of the CO 2 concentration at the surface of photosynthetic mesophyll cells ( c w ), applicable under reasonable assumptions of assimilation distribution within the leaf. We used Capsicum annuum , Helianthus annuus and Gossypium hirsutum as model plants for our experiments. We introduce calculations to estimate c w using independent adaxial and abaxial gas exchange measurements, and accounting for the mesophyll airspace resistances. The c w was lower than adaxial and abaxial estimated intercellular CO 2 concentrations ( c i ). Differences between c w and the c i of each surface were usually larger than 10 μmol mol −1 . Differences between adaxial and abaxial c i ranged from a few μmol mol −1 to almost 50 μmol mol −1 , where the largest differences were found at high air saturation deficits (ASD). Differences between adaxial and abaxial c i and the c i estimated by mixing both fluxes ranged from −30 to +20 μmol mol −1 , where the largest differences were found under high ASD or high ambient CO 2 concentrations. Accounting for c w improves the information that can be extracted from gas exchange experiments, allowing a more detailed description of the CO 2 and water vapor gradients within the leaf.
CO2Diffusion in Douglas Fir Bark
Publisher: Informa UK Limited
Date: 1999
Water Relations Link Carbon and Oxygen Isotope Discrimination to Phloem Sap Sugar Concentration in Eucalyptus globulus
Publisher: Oxford University Press (OUP)
Date: 04-2003
Abstract: A strong correlation was previously observed between carbon isotope discrimination (Δ13C) of phloem sap sugars and phloem sap sugar concentration in the phloem-bleeding tree Eucalyptus globulus Labill. (J. Pate, E. Shedley, D. Arthur, M. Adams [1998] Oecologia 117: 312–322). We hypothesized that correspondence between these two parameters results from covarying responses to plant water potential. We expected Δ13C to decrease with decreasing plant water potential and phloem sap sugar concentration to increase, thereby maintaining turgor within sieve tubes. The hypothesis was tested with analyses of E. globulus trees growing on opposite ends of a rainfall gradient in southwestern Australia. The Δ13C of phloem sap sugars was closely related to phloem sap sugar concentration (r = −0.90,P & 0.0001, n = 40). As predicted, daytime shoot water potential was positively related to Δ13C (r = 0.70, P& 0.0001, n = 40) and negatively related to phloem sap sugar concentration (r = −0.86,P & 0.0001, n = 40). Additional measurements showed a strong correspondence between predawn shoot water potential and phloem sap sugar concentration measured at midday (r = −0.87, P & 0.0001, n = 30). The Δ13C of phloem sap sugars collected from the stem agreed well with that predicted from instantaneous measurements of the ratio of intercellular to ambient carbon dioxide concentrations on subtending donor leaves. In accordance, instantaneous ratio of intercellular to ambient carbon dioxide concentrations correlated negatively with phloem sap sugar concentration (r = −0.91, P & 0.0001, n = 27). Oxygen isotope enrichment (Δ18O) in phloem sap sugars also varied with phloem sap sugar concentration (r = 0.91,P & 0.0001, n = 39), consistent with predictions from a theoretical model of Δ18O. We conclude that drought induces correlated variation in the concentration of phloem sap sugars and their isotopic composition in E. globulus.
Abundance and distribution of leaf wax n-alkanes in leaves of Acacia and Eucalyptus trees along a strong humidity gradient in northern Australia
Publisher: Elsevier BV
Date: 09-2013
Plant functional groups within a tropical forest exhibit different wood functional anatomy
Publisher: Wiley
Date: 10-11-2017
Computational models of populations of bacteria and lytic phage.
Publisher: Informa UK Limited
Date: 02-2016
Tropical tree growth sensitivity to climate is driven by species intrinsic growth rate and leaf traits
Publisher: Wiley
Date: 28-11-2021
DOI: 10.1111/GCB.15982
Abstract: A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long‐term climate averages (mean climate) drive spatial variations in species’ baseline growth rates, whereas deviations from these averages over time (anomalies) can create growth variation around the local baseline. However, the rarity of long‐term tree census data spanning climatic gradients has so far limited our understanding of their respective role, especially in tropical systems. Furthermore, tree growth sensitivity to climate is likely to vary widely among species, and the ecological strategies underlying these differences remain poorly understood. Here, we utilize an exceptional dataset of 49 years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how multiannual tree growth responds to both climate means and anomalies, and how species’ functional traits mediate these growth responses to climate. We show that anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast‐growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both climate means and anomalies. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests and that species traits can provide insights into understanding these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.
Isoscapes: a new dimension in community ecology
Publisher: Oxford University Press (OUP)
Date: 18-10-2016
Stability of tropical forest tree carbon‐water relations in a rainfall exclusion treatment through shifts in effective water uptake depth
Publisher: Wiley
Date: 21-09-2021
DOI: 10.1111/GCB.15869
Abstract: Increasing severity and frequency of drought is predicted for large portions of the terrestrial biosphere, with major impacts already documented in wet tropical forests. Using a 4‐year rainfall exclusion experiment in the Daintree Rainforest in northeast Australia, we examined canopy tree responses to reduced precipitation and soil water availability by quantifying seasonal changes in plant hydraulic and carbon traits for 11 tree species between control and drought treatments. Even with reduced soil volumetric water content in the upper 1 m of soil in the drought treatment, we found no significant difference between treatments for predawn and midday leaf water potential, photosynthesis, stomatal conductance, foliar stable carbon isotope composition, leaf mass per area, turgor loss point, xylem vessel anatomy, or leaf and stem nonstructural carbohydrates. While empirical measurements of aboveground traits revealed homeostatic maintenance of plant water status and traits in response to reduced soil moisture, modeled belowground dynamics revealed that trees in the drought treatment shifted the depth from which water was acquired to deeper soil layers. These findings reveal that belowground acclimation of tree water uptake depth may buffer tropical rainforests from more severe droughts that may arise in future with climate change.
The role of radiative cooling and leaf wetting in air–leaf water exchange during dew and radiation fog events in a temperate grassland
Publisher: Elsevier BV
Date: 2023
Functional susceptibility of tropical forests to climate change
Publisher: Springer Science and Business Media LLC
Date: 16-05-2022
DOI: 10.1038/S41559-022-01747-6
Abstract: Tropical forests are some of the most bio erse ecosystems in the world, yet their functioning is threatened by anthropogenic disturbances and climate change. Global actions to conserve tropical forests could be enhanced by having local knowledge on the forests' functional ersity and functional redundancy as proxies for their capacity to respond to global environmental change. Here we create estimates of plant functional ersity and redundancy across the tropics by combining a dataset of 16 morphological, chemical and photosynthetic plant traits s led from 2,461 in idual trees from 74 sites distributed across four continents together with local climate data for the past half century. Our findings suggest a strong link between climate and functional ersity and redundancy with the three trait groups responding similarly across the tropics and climate gradient. We show that drier tropical forests are overall less functionally erse than wetter forests and that functional redundancy declines with increasing soil water and vapour pressure deficits. Areas with high functional ersity and high functional redundancy tend to better maintain ecosystem functioning, such as aboveground biomass, after extreme weather events. Our predictions suggest that the lower functional ersity and lower functional redundancy of drier tropical forests, in comparison with wetter forests, may leave them more at risk of shifting towards alternative states in face of further declines in water availability across tropical regions.
Predicting species abundance by implementing the ecological niche theory
Publisher: Wiley
Date: 12-10-2021
DOI: 10.1111/ECOG.05776
Abstract: Species are not uniformly distributed across the landscape. For every species, there should be few favoured sites where abundance is high and many other sites of lower suitability where abundance is low. Consequently, local abundance could be thought of as a natural expression of species response to local conditions. The correlation between abundance and environmental suitability has been well documented, and a recent meta‐analysis has suggested that this relationship could be a generality. Despite the importance and potential implication of the abundance–suitability relationship, its predictive power for meaningful extrapolations has been surprisingly poorly explored. In this study, we showed how a highly predictable trend can be extracted from the abundance–suitability relationship, accurately predicting the variation in species abundance at a high spatial resolution. We produced high‐quality environmental suitability estimations for 50 endemic species in the Australian Wet Tropics. Environmental suitability derived from species distribution models was related to observed abundance estimated using data from 29 years of uninterrupted monitoring effort. We used the fitted relationship to accurately predict abundance at a fine scale across the species range. Our results showed that the abundance–suitability relationship was strong for endemic species in the Australian Wet Tropics. The predictive power of our models was high, explaining, on average, 55% of the deviance across taxa. Despite interspecific variation in the strength of the abundance–suitability relationship associated with potential intrinsic estimation biases, our approach provides a powerful tool for predicting abundance across the species range at a fine scale. The potential for robust abundance predictions from occurrence‐based species distribution models shown in this study are numerous, and it could have a significant impact in enhancing species conservation and management decisions.
Beyond tree-ring widths: stable isotopes sharpen the focus on climate responses of temperate forest trees
Publisher: Oxford University Press (OUP)
Date: 2015
Epiphytic ant‐plant obtains nitrogen from both native and invasive ant inhabitants
Publisher: Wiley
Date: 27-04-2022
DOI: 10.1111/BTP.13104
Abstract: Ant‐plants have been extensively used as model systems in the study of the evolution and ecology of mutualisms. Using a 15 N isotope labeling experiment, we found that both a native ant mutualist ( Philidris cordata ) and an invasive ant ( Pheidole megacephala ) provide nitrogen to the Australian ant‐plant Myrmecodia beccarii .
Deoxyribonucleic Acid Base Composition and Taxonomy of Thiobacilli and some Nitrifying Bacteria
Publisher: Microbiology Society
Date: 08-1968
Temperature, nutrient availability, and species traits interact to shape elevation responses of Australian tropical trees
Publisher: Frontiers Media SA
Date: 19-01-2023
DOI: 10.3389/FFGC.2023.1089167
Abstract: Elevation gradients provide natural laboratories for investigating tropical tree ecophysiology in the context of climate warming. Previously observed trends with increasing elevation include decreasing stem diameter growth rates (GR), increasing leaf mass per area (LMA), higher root-to-shoot ratios (R:S), increasing leaf δ 13 C, and decreasing leaf δ 15 N. These patterns could be driven by decreases in temperature, lower soil nutrient availability, changes in species composition, or a combination thereof. We investigated whether these patterns hold within the genus Flindersia (Rutaceae) along an elevation gradient (0–1,600 m) in the Australian Wet Tropics. Flindersia species are relatively abundant and are important contributors to biomass in these forests. Next, we conducted a glasshouse experiment to better understand the effects of temperature, soil nutrient availability, and species on growth, biomass allocation, and leaf isotopic composition. In the field, GR and δ 15 N decreased, whereas LMA and δ 13 C increased with elevation, consistent with observations on other continents. Soil C:N ratio also increased and soil δ 15 N decreased with increasing elevation, consistent with decreasing nutrient availability. In the glasshouse, relative growth rates (RGR) of the two lowland Flindersia species responded more strongly to temperature than did those of the two upland species. Interestingly, leaf δ 13 C displayed an opposite relationship with temperature in the glasshouse compared with that observed in the field, indicating the importance of covarying drivers in the field. Leaf δ 15 N increased in nutrient-rich compared to nutrient-poor soil in the glasshouse, like the trend in the field. There was a significant interaction for δ 15 N between temperature and species upland species showed a steeper increase in leaf δ 15 N with temperature than lowland species. This could indicate more flexibility in nitrogen acquisition in lowland compared to upland species with warming. The distinguishing feature of a mountaintop restricted Flindersia species in the glasshouse was a very high R:S ratio in nutrient-poor soil at low temperatures, conditions approximating the mountaintop environment. Our results suggest that species traits interact with temperature and nutrient availability to drive observed elevation patterns. Capturing this complexity in models will be challenging but is important for making realistic predictions of tropical tree responses to global warming.
Leaf nitrogen to phosphorus ratios of tropical trees: experimental assessment of physiological and environmental controls
Publisher: Wiley
Date: 03-12-2009
DOI: 10.1111/J.1469-8137.2009.03106.X
Abstract: We investigated the variation in leaf nitrogen to phosphorus ratios of tropical tree and liana seedlings as a function of the relative growth rate, whole-plant water-use efficiency, soil water content and fertilizer addition. First, seedlings of 13 tree and liana species were grown in idually in 38-l pots prepared with a homogeneous soil mixture. Second, seedlings of three tree species were grown in 19-l pots at high or low soil water content, and with or without added fertilizer containing nitrogen, phosphorus and potassium. For plants grown under common soil conditions, leaf nitrogen to phosphorus ratios showed a unimodal, or hump-shaped, relationship with the relative growth rate. The leaf nitrogen to phosphorus ratio increased in response to low soil water content in three species, and increased in response to fertilizer addition in two of the three species. Across all species and treatments, the leaf nitrogen to phosphorus ratio was positively correlated with the water-use efficiency. The results suggest that the within-site variation among tropical tree species in the leaf nitrogen to phosphorus ratio may be caused by associations between this ratio and the relative growth rate. Modification of the soil environment changed the leaf nitrogen to phosphorus ratio, but underlying associations between this ratio and the relative growth rate were generally maintained. The observed correlation between the leaf nitrogen to phosphorus ratio and water-use efficiency has implications for linking nutrient stoichiometry with plant transpiration.
Examining the vulnerability of Australian eucalypts to future drought-induced tree mortality
Publisher: Copernicus GmbH
Date: 04-03-2021
DOI: 10.5194/EGUSPHERE-EGU21-14527
Abstract: & & Australia is the driest inhabited continent. Annual rainfall is low and is accompanied by marked inter-annual variability, leading to multi-year droughts. Climate change is expected to alter the frequency, magnitude, and intensity of future droughts, with potentially major environmental and socio-economic consequences for Australia. However, Australian vegetation is well adapted to extended dry periods, thus, the likelihood of drought-induced mortality in the future depends both on the severity of future drought events and inherent vegetation resilience. Here, we used the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model, coupled with a stomatal optimisation scheme, to examine the projected impact of future drought for 24 Eucalyptus species. We forced CABLE with future climate from four global climate models (MIROC, ECHAM, CCCMA, and CSIRO) dynamically downscaled by three regional climate models. We separated the impact of climate change (e.g. increasing VPD, precipitation variability) from rising CO& sub& & /sub& (increasing water use-efficiency) to provide the first assessment of future drought risk to Australian trees.& &
Do 2H and 18O in leaf water reflect environmental drivers differently?
Publisher: Wiley
Date: 12-04-2022
DOI: 10.1111/NPH.18113
Abstract: We compiled hydrogen and oxygen stable isotope compositions (δ 2 H and δ 18 O) of leaf water from multiple biomes to examine variations with environmental drivers. Leaf water δ 2 H was more closely correlated with δ 2 H of xylem water or atmospheric vapour, whereas leaf water δ 18 O was more closely correlated with air relative humidity. This resulted from the larger proportional range for δ 2 H of meteoric waters relative to the extent of leaf water evaporative enrichment compared with δ 18 O. We next expressed leaf water as isotopic enrichment above xylem water (Δ 2 H and Δ 18 O) to remove the impact of xylem water isotopic variation. For Δ 2 H, leaf water still correlated with atmospheric vapour, whereas Δ 18 O showed no such correlation. This was explained by covariance between air relative humidity and the Δ 18 O of atmospheric vapour. This is consistent with a previously observed diurnal correlation between air relative humidity and the deuterium excess of atmospheric vapour across a range of ecosystems. We conclude that 2 H and 18 O in leaf water do indeed reflect the balance of environmental drivers differently our results have implications for understanding isotopic effects associated with water cycling in terrestrial ecosystems and for inferring environmental change from isotopic biomarkers that act as proxies for leaf water.
Conifers, Angiosperm Trees, and Lianas: Growth, Whole-Plant Water and Nitrogen Use Efficiency, and Stable Isotope Composition (δ 13C and δ 18O) of Seedlings Grown in a Tropical Environ
Publisher: Oxford University Press (OUP)
Date: 03-07-2008
Abstract: Seedlings of several species of gymnosperm trees, angiosperm trees, and angiosperm lianas were grown under tropical field conditions in the Republic of Panama physiological processes controlling plant C and water fluxes were assessed across this functionally erse range of species. Relative growth rate, r, was primarily controlled by the ratio of leaf area to plant mass, of which specific leaf area was a key component. Instantaneous photosynthesis, when expressed on a leaf-mass basis, explained 69% of variation in r (P & 0.0001, n = 94). Mean r of angiosperms was significantly higher than that of the gymnosperms within angiosperms, mean r of lianas was higher than that of trees. Whole-plant nitrogen use efficiency was also significantly higher in angiosperm than in gymnosperm species, and was primarily controlled by the rate of photosynthesis for a given amount of leaf nitrogen. Whole-plant water use efficiency, TEc, varied significantly among species, and was primarily controlled by c i/c a, the ratio of intercellular to ambient CO2 partial pressures during photosynthesis. Instantaneous measurements of c i/c a explained 51% of variation in TEc (P & 0.0001, n = 94). Whole-plant 13C discrimination also varied significantly as a function of c i/c a (R 2 = 0.57, P & 0.0001, n = 94), and was, accordingly, a good predictor of TEc. The 18O enrichment of stem dry matter was primarily controlled by the predicted 18O enrichment of evaporative sites within leaves (R 2 = 0.61, P & 0.0001, n = 94), with some residual variation explained by mean transpiration rate. Measurements of carbon and oxygen stable isotope ratios could provide a useful means of parameterizing physiological models of tropical forest trees.
Tropical tree growth sensitivity to climate is driven by species intrinsic growth rate and leaf traits
Publisher: Cold Spring Harbor Laboratory
Date: 09-06-2021
DOI: 10.1101/2021.06.08.447571
Abstract: A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long-term climate averages (mean climate) and short-term deviations from these averages (anomalies) both influence tree growth, but the rarity of long-term data integrating climatic gradients with tree censuses has so far limited our understanding of their respective role, especially in tropical systems. Here, we combined 49 years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how tree growth responds to both climate means and anomalies, and how species functional traits mediate these tree growth responses to climate. We showed that short-term, anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast-growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both long-term and short-term climate variations. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests, and that species traits can be leveraged to understand these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.
Effect of climate change on regeneration of plants from seeds in tropical wet forests
Publisher: Elsevier
Date: 2022
Tropical languor
Publisher: Springer Science and Business Media LLC
Date: 15-12-2014
DOI: 10.1038/NGEO2328
Bridge to the future: Important lessons from 20 years of ecosystem observations made by the OzFlux network
Publisher: Wiley
Date: 22-03-2022
DOI: 10.1111/GCB.16141
Abstract: In 2020, the Australian and New Zealand flux research and monitoring network, OzFlux, celebrated its 20 th anniversary by reflecting on the lessons learned through two decades of ecosystem studies on global change biology. OzFlux is a network not only for ecosystem researchers, but also for those ‘next users’ of the knowledge, information and data that such networks provide. Here, we focus on eight lessons across topics of climate change and variability, disturbance and resilience, drought and heat stress and synergies with remote sensing and modelling. In distilling the key lessons learned, we also identify where further research is needed to fill knowledge gaps and improve the utility and relevance of the outputs from OzFlux. Extreme climate variability across Australia and New Zealand (droughts and flooding rains) provides a natural laboratory for a global understanding of ecosystems in this time of accelerating climate change. As evidence of worsening global fire risk emerges, the natural ability of these ecosystems to recover from disturbances, such as fire and cyclones, provides lessons on adaptation and resilience to disturbance. Drought and heatwaves are common occurrences across large parts of the region and can tip an ecosystem's carbon budget from a net CO 2 sink to a net CO 2 source. Despite such responses to stress, ecosystems at OzFlux sites show their resilience to climate variability by rapidly pivoting back to a strong carbon sink upon the return of favourable conditions. Located in under‐represented areas, OzFlux data have the potential for reducing uncertainties in global remote sensing products, and these data provide several opportunities to develop new theories and improve our ecosystem models. The accumulated impacts of these lessons over the last 20 years highlights the value of long‐term flux observations for natural and managed systems. A future vision for OzFlux includes ongoing and newly developed synergies with ecophysiologists, ecologists, geologists, remote sensors and modellers.
Oxygen isotope composition of CAM and C3Clusia species: non‐steady‐state dynamics control leaf water 18O enrichment in succulent leaves
Publisher: Wiley
Date: 06-10-2008
DOI: 10.1111/J.1365-3040.2008.01868.X
Abstract: Leaf gas exchange and leaf water (18)O enrichment (Delta(18)O(L)) were measured in three Clusia species under field conditions during dry and wet seasons and in Miconia argentea during the dry season in the Republic of Panama. During the dry season, all three Clusia species used crassulacean acid metabolism (CAM) during the wet season Clusia pratensis operated in the C(3) mode, while Clusia uvitana and Clusia rosea used CAM. Large departures from isotopic steady state were observed in daytime Delta(18)O(L) of the Clusia species, especially during the dry season. In contrast, daytime Delta(18)O(L) was near isotopic steady state in the C(3) tree M. argentea. Across the full data set, non-steady-state predictions explained 49% of variation in observed Delta(18)O(L), whereas steady-state predictions explained only 14%. During the wet season, when Delta(18)O(L) could be compared with Clusia in iduals operating in both C(3) and CAM modes, steady-state and non-steady-state models gave contrasting predictions with respect to interspecific variation in daytime Delta(18)O(L). The observed Delta(18)O(L) pattern matched that predicted for the non-steady state. The results provided a clear ex le of how non-steady-state control of leaf water (18)O dynamics can shift the slope of the relationship between transpiration rate and daytime Delta(18)O(L) from negative to positive.
Automated calibration of laser spectrometer measurements of δ18O and δ2H values in water vapour using a Dew Point Generator
Publisher: Wiley
Date: 14-05-2018
DOI: 10.1002/RCM.8131
Abstract: Continuous measurement of stable O and H isotope compositions in water vapour requires automated calibration for remote field deployments. We developed a new low-cost device for calibration of both water vapour mole fraction and isotope composition. We coupled a commercially available dew point generator (DPG) to a laser spectrometer and developed hardware for water and air handling along with software for automated operation and data processing. We characterised isotopic fractionation in the DPG, conducted a field test and assessed the influence of critical parameters on the performance of the device. An analysis time of 1 hour was sufficient to achieve memory-free analysis of two water vapour standards and the δ The automated calibration system provides high accuracy and precision and is a robust, cost-effective option for long-term field measurements of water vapour isotopes. The necessary modifications to the DPG are minor and easily reversible.
Dynamic responses of gas exchange and photochemistry to heat interference during drought in wheat and sorghum
Publisher: CSIRO Publishing
Date: 2020
DOI: 10.1071/FP19242
Abstract: Drought and heat stress significantly affect crop growth and productivity worldwide. It is unknown how heat interference during drought affects physiological processes dynamically in crops. Here we focussed on gas exchange and photochemistry in wheat and sorghum in response to simulated heat interference via +15°C of temperature during ~2 week drought and re-watering. Results showed that drought decreased net photosynthesis (Anet), stomatal conductance (gs), maximum velocity of ribulose-1, 5-bisphosphate carboxylase/oxygenase carboxylation (Vcmax) and electron transport rate (J) in both wheat and sorghum. Heat interference did not further reduce Anet or gs. Drought increased non-photochemical quenching (Φnpq), whereas heat interference decreased Φnpq. The δ13C of leaf, stem and roots was higher in drought-treated wheat but lower in drought-treated sorghum. The results suggest that (1) even under drought conditions wheat and sorghum increased or maintained gs for transpirational cooling to alleviate negative effects by heat interference (2) non-photochemical quenching responded differently to drought and heat stress (3) wheat and sorghum responded in opposing patterns in δ13C. These findings point to the importance of stomatal regulation under heat crossed with drought stress and could provide useful information on development of better strategies to secure crop production for future climate change.
Humidity gradients in the air spaces of leaves
Publisher: Springer Science and Business Media LLC
Date: 08-08-2022
DOI: 10.1038/S41477-022-01202-1
Abstract: Stomata are orifices that connect the drier atmosphere with the interconnected network of more humid air spaces that surround the cells within a leaf. Accurate values of the humidities inside the substomatal cavity, w
Identifying areas at risk of drought‐induced tree mortality across South‐Eastern Australia
Publisher: Wiley
Date: 19-08-2020
DOI: 10.1111/GCB.15215
Infidelity in the outback: climate signal recorded in Δ18O of leaf but not branch cellulose of eucalypts across an Australian aridity gradient
Publisher: Oxford University Press (OUP)
Date: 21-12-2016
Abstract: The isotopic composition of leaf water in terrestrial plants is highly dependent upon a plant's environment. This isotopic signature can become integrated into organic molecules, allowing the isotopic composition of biomarkers such as cellulose to be used as sensitive paleo and climatic proxies. However, the mechanisms by which cellulose isotopic composition reflect environmental conditions are complex, and may vary between leaf and woody tissues. To date few empirical tests have been made on the relative roles of leaf-water enrichment and source water on the isotopic composition of leaf and wood cellulose within the same plant. Here, we study both leaf and branch wood cellulose, as well as xylem/source water of eucalypts across a 900 km aridity gradient in NE Australia. Across 11 sites, spanning average annual precipitation of 235-1400 mm and average relative humidity of 33-70%, we found a strong and consistent trend in leaf cellulose. However, once the effect of altered source water was considered we found wood cellulose to show no trend across this environmental gradient. We consider potential mechanisms that could explain the 'd ing' of a climatic signal within wood cellulose and consider the implication and limitations on the use of tree-ring cellulose as a climate proxy.
Robust Response of Terrestrial Plants to Rising CO2
Publisher: Elsevier BV
Date: 07-2019
DOI: 10.1016/J.TPLANTS.2019.04.003
Abstract: Human-caused CO
Nocturnal stomatal conductance and implications for modelling δ18O of leaf-respired CO2 in temperate tree species
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/FP05118
Abstract: Variation in the oxygen isotope composition of within-canopy CO2 has potential to allow partitioning of the ecosystem respiratory flux into above- and below-ground components. Recent theoretical work has highlighted the sensitivity of the oxygen isotope composition of leaf-respired CO2 (δRl) to nocturnal stomatal conductance. When the one-way flux model was tested on Ricinus communis L. large enrichments in δRl were observed. However, most species for which the isotope flux partitioning technique has been or would be applied (i.e. temperate tree species) are much more conservative users of water than R. communis. So, high stomatal conductance and very high enrichment of δRl observed may not be typical for temperate tree species. Using existing gas-exchange measurements on six temperate tree species, we demonstrate significant water loss through stomata for all species (i.e. statistically significantly greater than cuticular loss alone) at some time for some leaves during the night. δRl values predicted by the one-way flux model revealed that δRl might be very much more enriched than when the net flux alone is considered, particularly close to sunrise and sunset. Incorporation of the one-way flux model into ecosystem respiration partitioning studies will affect model outputs and interpretation of variation in the oxygen isotope composition of atmospheric CO2.
The multifaceted relationship between leaf water 18O enrichment and transpiration rate
Publisher: Wiley
Date: 19-03-2013
DOI: 10.1111/PCE.12081
Towards species‐level forecasts of drought‐induced tree mortality risk
Publisher: Wiley
Date: 22-04-2022
DOI: 10.1111/NPH.18129
Abstract: Predicting species‐level responses to drought at the landscape scale is critical to reducing uncertainty in future terrestrial carbon and water cycle projections. We embedded a stomatal optimisation model in the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model and parameterised the model for 15 canopy dominant eucalypt tree species across South‐Eastern Australia (mean annual precipitation range: 344–1424 mm yr −1 ). We conducted three experiments: applying CABLE to the 2017–2019 drought a 20% drier drought and a 20% drier drought with a doubling of atmospheric carbon dioxide (CO 2 ). The severity of the drought was highlighted as for at least 25% of their distribution ranges, 60% of species experienced leaf water potentials beyond the water potential at which 50% of hydraulic conductivity is lost due to embolism. We identified areas of severe hydraulic stress within‐species’ ranges, but we also pinpointed resilience in species found in predominantly semiarid areas. The importance of the role of CO 2 in ameliorating drought stress was consistent across species. Our results represent an important advance in our capacity to forecast the resilience of in idual tree species, providing an evidence base for decision‐making around the resilience of restoration plantings or net‐zero emission strategies.
Pantropical modelling of canopy functional traits using Sentinel-2 remote sensing data
Publisher: Elsevier BV
Date: 2021
Stable Isotopes Reveal the Contribution of Corticular Photosynthesis to Growth in Branches of Eucalyptus miniata
Publisher: Oxford University Press (OUP)
Date: 15-11-2010
The validity of optimal leaf traits modelled on environmental conditions
Publisher: Wiley
Date: 29-10-2019
DOI: 10.1111/NPH.15495
Abstract: The ratio of leaf intercellular to ambient CO
Transpiration efficiency over an annual cycle, leaf gas exchange and wood carbon isotope ratio of three tropical tree species
Publisher: Oxford University Press (OUP)
Date: 06-08-2009
Abstract: Variation in transpiration efficiency (TE) and its relationship with the stable carbon isotope ratio of wood was investigated in the saplings of three tropical tree species. Five in iduals each of Platymiscium pinnatum (Jacq.) Dugand, Swietenia macrophylla King and Tectona grandis Linn. f. were grown in idually in large (760 l) pots over 16 months in the Republic of Panama. Cumulative transpiration was determined by repeatedly weighing the pots with a pallet truck scale. Dry matter production was determined by destructive harvest. The TE, expressed as experiment-long dry matter production ided by cumulative water use, averaged 4.1, 4.3 and 2.9 g dry matter kg(-1) water for P. pinnatum, S. macrophylla and T. grandis, respectively. The TE of T. grandis was significantly lower than that of the other two species. Instantaneous measurements of the ratio of intercellular to ambient CO(2) partial pressures (c(i)/c(a)), taken near the end of the experiment, explained 66% of variation in TE. Stomatal conductance was lower in S. macrophylla than in T. grandis, whereas P. pinnatum had similar stomatal conductance to T. grandis, but with a higher photosynthetic rate. Thus, c(i)/c(a) and TE appeared to vary in response to both stomatal conductance and photosynthetic capacity. Stem-wood delta(13)C varied over a relatively narrow range of just 2.2 per thousand, but still explained 28% of variation in TE. The results suggest that leaf-level processes largely determined variation among the three tropical tree species in whole-plant water-use efficiency integrated over a full annual cycle.
Transpiration modulates phosphorus acquisition in tropical tree seedlings
Publisher: Oxford University Press (OUP)
Date: 08-2011
Abstract: Several experiments were conducted with tropical tree and liana seedlings in which transpiration ratio and leaf phosphorus to carbon ratio (P:C) were measured. Transpiration ratio was expressed as kg H(2)O transpired&emsp14 g(-1) C incorporated into plant biomass, and leaf P:C as mg P&emsp14 g(-1) C. Leaf P:C was positively correlated with transpiration ratio across 19 species for plants grown under similar conditions (R(2) = 0.35, P < 0.01, n = 19). For five species in the dataset, multiple treatments were imposed to cause intra-specific variation in transpiration ratio. Within four of these five species, leaf P:C correlated positively with transpiration ratio. The slope and strength of the correlation varied among species. In one experiment, whole-plant P:C was measured in addition to leaf P:C. Patterns of correlation between whole-plant P:C and transpiration ratio were similar to those between leaf P:C and transpiration ratio. Together, these observations suggest that transpiration can influence the rate of P uptake from soil in tropical tree and liana seedlings. We suggest that this occurs through transport of inorganic phosphate and organic P compounds to root surfaces by transpiration-induced mass flow of the soil solution. The positive correlation between leaf P:C and transpiration ratio suggests that leaf P:C could decline in tropical forests as atmospheric CO(2) concentration rises, due to decreasing transpiration ratios.
Ozone impacts on tropical forest productivity
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-15707
Abstract: Tropospheric ozone (O3) reduces plant productivity by entering leaves, generating reactive oxygen species and causing oxidative stress which in turn increases respiration, decreases photosynthesis, plant growth, biomass accumulation, and consequently reduces the land carbon sink. Tropical forests are potentially most vulnerable to future O3 scenarios given their high productivity, generally high stomatal conductance and environmental conditions conducive to O3 uptake (eg precursor emissions during biomass burning).Here we present the first comprehensive set of measurements of O3 effects on plant physiology and biomass accumulation in tropical forests. We exposed twelve tropical tree species to elevated O3 concentrations in Open Top Chambers (OTCs) based at the James Cook University O3 experimental facility in Cairns, Australia, from which we generate O3 dose-response functions for each species. We test the importance of Leaf Mass per unit Area (LMA) as an indicator of O3 sensitivity.We use these relationships to parameterize the global land-surface model JULES, and apply the model over the pan-tropical region using contemporary near-surface O3 concentration fields. For the first time we quantify the impact of O3 on contemporary tropical productivity.
Environmental and physiological determinants of carbon isotope discrimination in terrestrial plants
Publisher: Wiley
Date: 31-07-2013
DOI: 10.1111/NPH.12423
Abstract: Stable carbon isotope ratios (δ 13 C ) of terrestrial plants are employed across a erse range of applications in environmental and plant sciences however, the kind of information that is desired from the δ 13 C signal often differs. At the extremes, it ranges between purely environmental and purely biological. Here, we review environmental drivers of variation in carbon isotope discrimination (Δ) in terrestrial plants, and the biological processes that can either d or lify the response. For C 3 plants, where Δ is primarily controlled by the ratio of intercellular to ambient CO 2 concentrations ( c i / c a ), coordination between stomatal conductance and photosynthesis and leaf area adjustment tends to constrain the potential environmentally driven range of Δ. For C 4 plants, variation in bundle‐sheath leakiness to CO 2 can either d or lify the effects of c i / c a on Δ. For plants with crassulacean acid metabolism ( CAM ), Δ varies over a relatively large range as a function of the proportion of daytime to night‐time CO 2 fixation. This range can be substantially broadened by environmental effects on Δ when carbon uptake takes place primarily during the day. The effective use of Δ across its full range of applications will require a holistic view of the interplay between environmental control and physiological modulation of the environmental signal. Contents Summary 950 I. Introduction 950 II. Carbon isotope discrimination 951 III. The C 3 photosynthetic pathway 951 IV. The C 4 photosynthetic pathway 957 V. Crassulacean acid metabolism 959 VI. Conclusion 961 Acknowledgements 961 Reference 961
Environmental impacts of abrasive blasting of transmission towers in protected areas
Publisher: Elsevier BV
Date: 12-2019
DOI: 10.1016/J.JENVMAN.2019.109430
Abstract: In Australia, and other parts of the world, tower infrastructure in electricity transmission networks are nearing the end of their asset life. In changing economic, political and regulatory environments Transmission Network Service Providers are implementing new approaches to asset management and reinvestment, such as refurbishment to extend the life of existing assets, instead of replacement. As part of these refurbishment efforts, abrasive blasting and recoating is being employed to remove corrosion and extend the life of steel electricity transmission towers. New controls and procedures have been developed to manage the most likely impacts associated with the abrasive blasting of transmission towers. However, little or no data have been available on the environmental impacts of abrasive blasting or the effectiveness of management procedures currently being used to mitigate potential adverse environmental impacts.We conducted an integrated study on the impacts of abrasive blasting, which brought together on-site research modelling and controlled laboratory trials. The study was undertaken during a transmission tower refurbishment project within the World Heritage listed Wet Tropics Region in Queensland, Australia. Measured metal deposition around towers due to blasting, was primarily as large particles (>PM10) at 12-30 m from the tower. Soil concentrations of metals were highest under towers, with a small number of s les showing elevated zinc at 12-30 m. The presence of spent abrasive media and dust on the geofabric material used under the towers and up to 15 m from the tower base, as part of control measures used to contain the abrasive products, indicates that deposition also occurs between 0 and 12 m from the tower.The potential impacts of the abrasive blasting technique on plants and invertebrates appear to be low. Five species of tropical rainforest tree seedlings exposed to abrasive blasting dust at worst-case levels had no negative impact on physiological performance or plant health. This research will assist Transmission Network Service Providers and other operators of corroded linear infrastructure to plan and implement mitigating management actions and procedures during abrasive blasting projects and assist regulators and the community to better understand the impacts of the practice.
Towards species-level forecasts of drought-induced tree mortality risk
Publisher: Copernicus GmbH
Date: 27-03-2022
DOI: 10.5194/EGUSPHERE-EGU22-2419
Abstract: & & Predicting species-level responses to drought at the landscape scale is critical to reducing future uncertainty in terrestrial carbon and water cycle projections. We embedded a stomatal optimisation model in the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model. We parameterised the model for 15 canopy dominant eucalypt tree species representative of a broad precipitation gradient across South East Australia (mean annual precipitation range: 344& #8211 mm yr& sup& -1& /sup& ). We conducted three experiments: (i) applying CABLE to the 2017& #8211 drought in South East Australia (ii) a 20% drier drought and (iii) a 20% drier drought with a doubling of atmospheric carbon dioxide (CO& sub& & /sub& ). We identified several drought hotspots across the ranges of & em& E.viminalis& /em& , & em& E.obliqua& /em& , & em& E.globulus& /em& , & em& E.saligna,& /em& and & em& E.grandis& /em& . By contrast, CABLE simulated drought resilience in species that are found predominately in semi-arid areas such as & em& E.largiflorens& /em& and & em& E.populnea& /em& . We identified several key model assumptions (& em& e& /em& .& em& g& /em& ., the degree of stomatal control) and sensitivities (& em& e& /em& .& em& g& /em& ., the role of CO& sub& & /sub& in ameliorating drought) that require future research. Our results represent an important step forward in our capacity to forecast the resilience of in idual tree species, providing an evidence base for decision-making around the resilience of restoration plantings or strategies associated with achieving net-zero emissions.& &
Red light shines a path forward on leaf minimum conductance
Publisher: Wiley
Date: 29-10-2021
DOI: 10.1111/NPH.17794
Abstract: This article is a Commentary on Márquez et al . (2022), 233 : 156–168 .
Diurnal variation in the stable isotope composition of water and dry matter in fruiting Lupinus angustifolius under field conditions
Publisher: Wiley
Date: 27-06-2002
Living on the edge
Publisher: Wiley
Date: 20-05-2021
DOI: 10.1111/GCB.15641
Abstract: Globally, forests are facing an increasing risk of mass tree mortality events associated with extreme droughts and higher temperatures. Hydraulic dysfunction is considered a key mechanism of drought‐triggered dieback. By leveraging the climate breadth of the Australian landscape and a national network of research sites (Terrestrial Ecosystem Research Network), we conducted a continental‐scale study of physiological and hydraulic traits of 33 native tree species from contrasting environments to disentangle the complexities of plant response to drought across communities. We found strong relationships between key plant hydraulic traits and site aridity. Leaf turgor loss point and xylem embolism resistance were correlated with minimum water potential experienced by each species. Across the data set, there was a strong coordination between hydraulic traits, including those linked to hydraulic safety, stomatal regulation and the cost of carbon investment into woody tissue. These results illustrate that aridity has acted as a strong selective pressure, shaping hydraulic traits of tree species across the Australian landscape. Hydraulic safety margins were constrained across sites, with species from wetter sites tending to have smaller safety margin compared with species at drier sites, suggesting trees are operating close to their hydraulic thresholds and forest biomes across the spectrum may be susceptible to shifts in climate that result in the intensification of drought.
Effect of Vapor Pressure Deficit on Gas Exchange in Wild-Type and Abscisic Acid–Insensitive Plants
Publisher: Oxford University Press (OUP)
Date: 27-09-2019
DOI: 10.1104/PP.19.00436
Identifying drivers of leaf water and cellulose stable isotope enrichment in Eucalyptus in northern Australia
Publisher: Springer Science and Business Media LLC
Date: 31-10-2016
DOI: 10.1007/S00442-016-3761-8
Abstract: Several previous studies have investigated the use of the stable hydrogen and oxygen isotope compositions in plant materials as indicators of palaeoclimate. However, accurate interpretation relies on a detailed understanding of both physiological and environmental drivers of the variations in isotopic enrichments that occur in leaf water and associated organic compounds. To progress this aim we measured δ
Optimal climate for large trees at high elevations drives patterns of biomass in remote forests of Papua New Guinea
Publisher: Wiley
Date: 31-05-2017
DOI: 10.1111/GCB.13741
Abstract: Our ability to model global carbon fluxes depends on understanding how terrestrial carbon stocks respond to varying environmental conditions. Tropical forests contain the bulk of the biosphere's carbon. However, there is a lack of consensus as to how gradients in environmental conditions affect tropical forest carbon. Papua New Guinea (PNG) lies within one of the largest areas of contiguous tropical forest and is characterized by environmental gradients driven by altitude yet, the region has been grossly understudied. Here, we present the first field assessment of aboveground biomass (AGB) across three main forest types of PNG using 193 plots stratified across 3,100-m elevation gradient. Unexpectedly, AGB had no direct relationship to rainfall, temperature, soil, or topography. Instead, natural disturbances explained most variation in AGB. While large trees (diameter at breast height > 50 cm) drove altitudinal patterns of AGB, resulting in a major peak in AGB (2,200-3,100 m) and some of the most carbon-rich forests at these altitudes anywhere. Large trees were correlated to a set of climatic variables following a hump-shaped curve. The set of "optimal" climatic conditions found in montane cloud forests is similar to that of maritime temperate areas that harbor the largest trees in the world: high ratio of precipitation to evapotranspiration (2.8), moderate mean annual temperature (13.7°C), and low intra-annual temperature range (7.5°C). At extreme altitudes (2,800-3,100 m), where tree ersity elsewhere is usually low and large trees are generally rare or absent, specimens from 18 families had girths >70 cm diameter and maximum heights 20-41 m. These findings indicate that simple AGB-climate-edaphic models may not be suitable for estimating carbon storage in forests where optimal climate niches exist. Our study, conducted in a very remote area, suggests that tropical montane forests may contain greater AGB than previously thought and the importance of securing their future under a changing climate is therefore enhanced.
Leaf vein fraction influences the Péclet effect and 18O enrichment in leaf water
Publisher: Wiley
Date: 21-09-2016
DOI: 10.1111/PCE.12792
Abstract: The process of evaporation results in the fractionation of water isotopes such that the lighter
Elevated temperature and carbon dioxide alter resource allocation to growth, storage and defence in cassava (Manihot esculenta)
Publisher: Elsevier BV
Date: 05-2020
A meta‐analysis of responses of C3 plants to atmospheric CO2: dose–response curves for 85 traits ranging from the molecular to the whole‐plant level
Publisher: Wiley
Date: 26-11-2021
DOI: 10.1111/NPH.17802
Abstract: Generalised dose–response curves are essential to understand how plants acclimate to atmospheric CO 2 . We carried out a meta‐analysis of 630 experiments in which C 3 plants were experimentally grown at different [CO 2 ] under relatively benign conditions, and derived dose–response curves for 85 phenotypic traits. These curves were characterised by form, plasticity, consistency and reliability. Considered over a range of 200–1200 µmol mol −1 CO 2 , some traits more than doubled (e.g. area‐based photosynthesis intrinsic water‐use efficiency), whereas others more than halved (area‐based transpiration). At current atmospheric [CO 2 ], 64% of the total stimulation in biomass over the 200–1200 µmol mol −1 range has already been realised. We also mapped the trait responses of plants to [CO 2 ] against those we have quantified before for light intensity. For most traits, CO 2 and light responses were of similar direction. However, some traits (such as reproductive effort) only responded to light, others (such as plant height) only to [CO 2 ], and some traits (such as area‐based transpiration) responded in opposite directions. This synthesis provides a comprehensive picture of plant responses to [CO 2 ] at different integration levels and offers the quantitative dose–response curves that can be used to improve global change simulation models.
Factors Affecting the Oxygen Isotope Ratio of Plant Organic Material
Publisher: Elsevier
Date: 2005
Stem and leaf gas exchange and their responses to fire in a north Australian tropical savanna
Publisher: Wiley
Date: 12-2005
DOI: 10.1111/J.1365-3040.2005.01442.X
Abstract: We measured stem CO2 efflux and leaf gas exchange in a tropical savanna ecosystem in northern Australia, and assessed the impact of fire on these processes. Gas exchange of mature leaves that flushed after a fire showed only slight differences from that of mature leaves on unburned trees. Expanding leaves typically showed net losses of CO2 to the atmosphere in both burned and unburned trees, even under saturating irradiance. Fire caused stem CO2 efflux to decline in overstory trees, when measured 8 weeks post-fire. This decline was thought to have resulted from reduced availability of C substrate for respiration, due to reduced canopy photosynthesis caused by leaf scorching, and to priority allocation of fixed C towards reconstruction of a new canopy. At the ecosystem scale, we estimated the annual above-ground woody-tissue CO2 efflux to be 275 g C m(-2) ground area year(-1) in a non-fire year, or approximately 13% of the annual gross primary production. We contrasted the canopy physiology of two co-dominant overstory tree species, one of which has a smooth bark on its branches capable of photosynthetic re-fixation (Eucalyptus miniata), and the other of which has a thick, rough bark incapable of re-fixation (Eucalyptus tetrodonta). Eucalyptus miniata supported a larger branch sapwood cross-sectional area in the crown per unit subtending leaf area, and had higher leaf stomatal conductance and photosynthesis than E. tetrodonta. Re-fixation by photosynthetic bark reduces the C cost of delivering water to evaporative sites in leaves, because it reduces the net C cost of constructing and maintaining sapwood. We suggest that re-fixation allowed leaves of E. miniata to photosynthesize at higher rates than those of E. tetrodonta, while the two invested similar amounts of C in the maintenance of branch sapwood.
The benefits of recycling: how photosynthetic bark can increase drought tolerance
Publisher: Wiley
Date: 04-11-2015
DOI: 10.1111/NPH.13723
A continental-scale assessment of variability in leaf traits: Within species, across sites and between seasons
Publisher: Wiley
Date: 06-04-2018
Responses of foliar 13C, gas exchange and leaf morphology to reduced hydraulic conductivity in Pinus monticola branches
Publisher: Oxford University Press (OUP)
Date: 10-2001
DOI: 10.1093/TREEPHYS/21.16.1215
Abstract: We tested the hypothesis that branch hydraulic conductivity partly controls foliar stable carbon isotope ratio (delta13C) by its influence on stomatal conductance in Pinus monticola Dougl. Notching and phloem-girdling treatments were applied to reduce branch conductivity over the course of a growing season. Notching and phloem girdling reduced leaf-specific conductivity (LSC) by about 30 and 90%, respectively. The 90% reduction in LSC increased foliar delta13C by about 1 per thousand (P < 0.0001, n = 65), whereas the 30% reduction in LSC had no effect on foliar delta13C (P = 0.90, n = 65). Variation in the delta13C of dark respiration was similar to that of whole-tissues when compared among treatments. These isotopic measurements, in addition to instantaneous gas exchange measurements, suggested only minor adjustments in the ratio of intercellular to atmospheric CO2 partial pressures (ci/ca) in response to experimentally reduced hydraulic conductivity. A strong correlation was observed between stomatal conductance (gs) and photosynthetic demand over a tenfold range in gs. Although ci/ca and delta13C appeared to be relatively homeostatic, current-year leaf area varied linearly as a function of branch hydraulic conductivity (r2 = 0.69, P < 0.0001, n = 18). These results suggest that, for Pinus monticola, adjustment of leaf area is a more important response to reduced branch conductivity than adjustment of ci/ca.
Supplementary material to Wood microclimate as a predictor of carbon dioxide fluxes from deadwood in tropical Australia
Publisher: Copernicus GmbH
Date: 13-09-2023
The effects of an experimental drought on the ecophysiology and fruiting phenology of a tropical rainforest palm
Publisher: Oxford University Press (OUP)
Date: 09-10-2020
DOI: 10.1093/JPE/RTAA069
Abstract: Anthropogenic climate change is predicted to increase mean temperatures and rainfall seasonality. How tropical rainforest species will respond to this climate change remains uncertain. Here, we analysed the effects of a 4-year experimental throughfall exclusion (TFE) on an Australian endemic palm (Normambya normanbyi) in the Daintree rainforest of North Queensland, Australia. We aimed to understand the impact of a simulated reduction in rainfall on the species’ physiological processes and fruiting phenology. We examined the fruiting phenology and ecophysiology of this locally abundant palm to determine the ecological responses of the species to drought. Soil water availability was reduced overall by ~30% under a TFE experiment, established in May 2015. We monitored monthly fruiting activity for 8 years in total (2009–2018), including 4 years prior to the onset of the TFE. In the most recent year of the study, we measured physiological parameters including photosynthetic rate, stomatal conductance and carbon stable isotopes (δ 13C, an integrated measure of water use efficiency) from young and mature leaves in both the dry and wet seasons. We determined that the monthly fruiting activity of all palms was primarily driven by photoperiod, mean solar radiation and mean temperature. However, in iduals exposed to lower soil moisture in the TFE decreased significantly in fruiting activity, photosynthetic rate and stomatal conductance. We found that these measures of physiological performance were affected by the TFE, season and the interaction of the two. Recovery of fruiting activity in the TFE palms was observed in 2018, when there was an increase in shallow soil moisture compared with previous years in the treatment. Our findings suggest that palms, such as the N. normanbyi, will be sensitive to future climate change with long-term monitoring recommended to determine population-scale impacts.
Directional change in leaf dry matter δ 13C during leaf development is widespread in C3 plants
Publisher: Oxford University Press (OUP)
Date: 24-06-2020
DOI: 10.1093/AOB/MCAA114
Abstract: The stable carbon isotope ratio of leaf dry matter (δ 13Cp) is generally a reliable recorder of intrinsic water-use efficiency in C3 plants. Here, we investigated a previously reported pattern of developmental change in leaf δ 13Cp during leaf expansion, whereby emerging leaves are initially 13C-enriched compared to mature leaves on the same plant, with their δ 13Cp decreasing during leaf expansion until they eventually take on the δ 13Cp of other mature leaves. We compiled data to test whether the difference between mature and young leaf δ 13Cp differs between temperate and tropical species, or between deciduous and evergreen species. We also tested whether the developmental change in δ 13Cp is indicative of a concomitant change in intrinsic water-use efficiency. To gain further insight, we made online measurements of 13C discrimination (∆ 13C) in young and mature leaves. We found that the δ 13Cp difference between mature and young leaves was significantly larger for deciduous than for evergreen species (−2.1 ‰ vs. −1.4 ‰, respectively). Counter to expectation based on the change in δ 13Cp, intrinsic water-use efficiency did not decrease between young and mature leaves rather, it did the opposite. The ratio of intercellular to ambient CO2 concentrations (ci/ca) was significantly higher in young than in mature leaves (0.86 vs. 0.72, respectively), corresponding to lower intrinsic water-use efficiency. Accordingly, instantaneous ∆ 13C was also higher in young than in mature leaves. Elevated ci/ca and ∆ 13C in young leaves resulted from a combination of low photosynthetic capacity and high day respiration rates. The decline in leaf δ 13Cp during leaf expansion appears to reflect the addition of the expanding leaf’s own 13C-depleted photosynthetic carbon to that imported from outside the leaf as the leaf develops. This mixing of carbon sources results in an unusual case of isotopic deception: less negative δ 13Cp in young leaves belies their low intrinsic water-use efficiency.
Stable isotopes in leaf water of terrestrial plants
Publisher: Wiley
Date: 23-03-2016
DOI: 10.1111/PCE.12703
Abstract: Leaf water contains naturally occurring stable isotopes of oxygen and hydrogen in abundances that vary spatially and temporally. When sufficiently understood, these can be harnessed for a wide range of applications. Here, we review the current state of knowledge of stable isotope enrichment of leaf water, and its relevance for isotopic signals incorporated into plant organic matter and atmospheric gases. Models describing evaporative enrichment of leaf water have become increasingly complex over time, reflecting enhanced spatial and temporal resolution. We recommend that practitioners choose a model with a level of complexity suited to their application, and provide guidance. At the same time, there exists some lingering uncertainty about the biophysical processes relevant to patterns of isotopic enrichment in leaf water. An important goal for future research is to link observed variations in isotopic composition to specific anatomical and physiological features of leaves that reflect differences in hydraulic design. New measurement techniques are developing rapidly, enabling determinations of both transpired and leaf water δ(18) O and δ(2) H to be made more easily and at higher temporal resolution than previously possible. We expect these technological advances to spur new developments in our understanding of patterns of stable isotope fractionation in leaf water.
Leaf water deuterium enrichment shapes leaf wax n-alkane δD values of angiosperm plants II: Observational evidence and global implications
Publisher: Elsevier BV
Date: 06-2013
Oxygen and carbon isotope composition of parasitic plants and their hosts in southwestern Australia
Publisher: Springer Science and Business Media LLC
Date: 04-2004
DOI: 10.1007/S00442-004-1506-6
Abstract: We measured leaf dry matter delta(18)O and delta(13)C in parasitic plants and their hosts growing in southwestern Australia. Parasite/host pairs included two mistletoe species, three species of holoparasites, and five species of root hemiparasites. Among these parasite functional types, significant variation was observed in parasite/host isotopic differences for both delta(18)O ( P<0.0001, n=65) and delta(13)C ( P<0.0001, n=64). Mistletoes were depleted in both (18)O and (13)C compared to their hosts parasite/host differences were -4.0 per thousand for delta(18)O ( P<0.0001) and -1.9 per thousand for delta(13)C ( P<0.0001). The lower delta(18)O in mistletoe leaf dry matter compared to their hosts is consistent with the frequently observed high transpiration rates of these parasites. Root hemiparasites were also depleted in (18)O and (13)C compared to their hosts, but not to the same extent as mistletoes parasite/host differences were -1.0 per thousand for delta(18)O ( P=0.04) and -1.2 per thousand for delta(13)C ( P=0.0006). In contrast to mistletoes and root hemiparasites, holoparasites were enriched in both (18)O and (13)C compared to their hosts parasite/host differences were +3.0 per thousand for delta(18)O ( P<0.0001) and +1.5 per thousand for delta(13)C ( P=0.02). The enrichment in (18)O for holoparasite dry matter did not result from more enriched tissue water holoparasite tissue water delta(18)O was less than host leaf water delta(18)O by a difference of -3.8 per thousand when s led at midday ( P=0.0003). Enrichment of holoparasites in (13)C compared to their hosts is consistent with a generally observed pattern of enrichment in heterotrophic plant tissues. Results provide insights into the ecology of parasitic plants in southwestern Australia additionally, they provide a context for the formulation of specific hypotheses aimed at elucidating mechanisms underlying isotopic variations among plants.
Large variation in whole‐plant water‐use efficiency among tropical tree species
Publisher: Wiley
Date: 02-11-2006
DOI: 10.1111/J.1469-8137.2006.01913.X
Abstract: It is well known that whole-plant water-use efficiency (transpiration efficiency of carbon gain, TE(C)) varies among plant species with different photosynthetic pathways. However, less is known of such variation among tree species within the C(3) group. Here we measured the TE(C) of seven C(3) tropical tree species. Isotopic analyses (delta(13)C, delta(18)O, and delta(15)N) and elemental analyses (carbon and nitrogen) were undertaken to provide insight into sources of variation in TE(C). Plants were grown over several months in approx. 80% full sunlight in in idual 38-l containers in the Republic of Panama. Soil moisture content was nonlimiting. Significant variation was observed in TE(C) among the C(3) tree species. Values ranged from 1.6 mmol C mol(-1) H(2)O for teak (Tectona grandis) to 4.0 mmol C mol(-1) H(2)O for a legume, Platymiscium pinnatum. Variation in TE(C) was correlated with both leaf N concentration, a proxy for photosynthetic capacity, and oxygen-isotope enrichment, a proxy for stomatal conductance. The TE(C) varied with C-isotope discrimination within species, but the relationship broke down among species, reflecting the existence of species-specific offsets.
The relationship of leaf photosynthetic traits – Vcmax and Jmax – to leaf nitrogen, leaf phosphorus, and specific leaf area: a meta‐analysis and modeling study
Publisher: Wiley
Date: 25-07-2014
DOI: 10.1002/ECE3.1173
Photosynthetic physiology of eucalypts along a sub-continental rainfall gradient in northern Australia
Publisher: Elsevier BV
Date: 11-2011
Why are non-photosynthetic tissues generally 13C enriched compared with leaves in C3 plants? Review and synthesis of current hypotheses
Publisher: CSIRO Publishing
Date: 2009
DOI: 10.1071/FP08216
Abstract: Non-photosynthetic, or heterotrophic, tissues in C3 plants tend to be enriched in 13C compared with the leaves that supply them with photosynthate. This isotopic pattern has been observed for woody stems, roots, seeds and fruits, emerging leaves, and parasitic plants incapable of net CO2 fixation. Unlike in C3 plants, roots of herbaceous C4 plants are generally not 13C-enriched compared with leaves. We review six hypotheses aimed at explaining this isotopic pattern in C3 plants: (1) variation in biochemical composition of heterotrophic tissues compared with leaves (2) seasonal separation of growth of leaves and heterotrophic tissues, with corresponding variation in photosynthetic discrimination against 13C (3) differential use of day v. night sucrose between leaves and sink tissues, with day sucrose being relatively 13C-depleted and night sucrose 13C-enriched (4) isotopic fractionation during dark respiration (5) carbon fixation by PEP carboxylase and (6) developmental variation in photosynthetic discrimination against 13C during leaf expansion. Although hypotheses (1) and (2) may contribute to the general pattern, they cannot explain all observations. Some evidence exists in support of hypotheses (3) through to (6), although for hypothesis (6) it is largely circumstantial. Hypothesis (3) provides a promising avenue for future research. Direct tests of these hypotheses should be carried out to provide insight into the mechanisms causing within-plant variation in carbon isotope composition.
Photosynthesis and water-use efficiency of seedlings from northern Australian monsoon forest, savanna and swamp habitats grown in a common garden
Publisher: CSIRO Publishing
Date: 2010
DOI: 10.1071/FP09306
Abstract: Islands of monsoon rainforest and Melaleuca sw punctuate vast tracts of savanna in monsoonal northern Australia. Seedlings of species from each of these habitat associations were grown in a common garden. Monsoon forest species had higher specific leaf area, lower photosynthetic capacity and lower photosynthetic light compensation points, and required lower irradiance to achieve 50% of light-saturated photosynthesis compared with savanna or sw species. These traits probably contribute towards greater shade tolerance beneath dense monsoon-forest canopies, whereas savanna and sw canopies are relatively open. Sw species, especially two Melaleuca species, had high stomatal conductance and small CO2 drawdown during photosynthesis, and more negative leaf δ13C, compared with monsoon forest and savanna species. Higher stomatal conductance increases carbon uptake during photosynthesis and a high transpiration rate would increase transport of nutrients to absorbing surfaces in the root by mass flow. Thus, a strategy of high transpiration and low water-use efficiency appears to be favoured in sw species compared with monsoon-forest and savanna species. Instantaneous measurements of the ratio of intercellular to ambient CO2 concentrations (ci/ca) explained 81% of variation in leaf δ13C across 44 species s led in this and other studies, suggesting that leaf δ13C generally provides a robust proxy for comparisons of ci/ca, even when applied across species.
Climate and soils together regulate photosynthetic carbon isotope discrimination within C3 plants worldwide
Publisher: Wiley
Date: 09-2018
DOI: 10.1111/GEB.12764
Termite sensitivity to temperature affects global wood decay rates
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-09-2022
Abstract: Deadwood is a large global carbon store with its store size partially determined by biotic decay. Microbial wood decay rates are known to respond to changing temperature and precipitation. Termites are also important decomposers in the tropics but are less well studied. An understanding of their climate sensitivities is needed to estimate climate change effects on wood carbon pools. Using data from 133 sites spanning six continents, we found that termite wood discovery and consumption were highly sensitive to temperature (with decay increasing .8 times per 10°C increase in temperature)—even more so than microbes. Termite decay effects were greatest in tropical seasonal forests, tropical savannas, and subtropical deserts. With tropicalization (i.e., warming shifts to tropical climates), termite wood decay will likely increase as termites access more of Earth’s surface.
Effects of forest thinning on soil-plant carbon and nitrogen dynamics
Publisher: Springer Science and Business Media LLC
Date: 10-09-2017
On the use of leaf water to determine plant water source: A proof of concept
Publisher: Wiley
Date: 03-2021
DOI: 10.1002/HYP.14073
Functional traits of lianas in an Australian lowland rainforest align with post‐disturbance rather than dry season advantage
Publisher: Wiley
Date: 12-05-2019
DOI: 10.1111/AEC.12764
Zea mays rhizosphere respiration, but not soil organic matter decomposition was stable across a temperature gradient
Publisher: Elsevier BV
Date: 11-2010
Tropical forest responses to increasing atmospheric CO2: current knowledge and opportunities for future research
Publisher: CSIRO Publishing
Date: 2013
DOI: 10.1071/FP12309
Abstract: Elevated atmospheric CO2 concentrations (ca) will undoubtedly affect the metabolism of tropical forests worldwide however, critical aspects of how tropical forests will respond remain largely unknown. Here, we review the current state of knowledge about physiological and ecological responses, with the aim of providing a framework that can help to guide future experimental research. Modelling studies have indicated that elevated ca can potentially stimulate photosynthesis more in the tropics than at higher latitudes, because suppression of photorespiration by elevated ca increases with temperature. However, canopy leaves in tropical forests could also potentially reach a high temperature threshold under elevated ca that will moderate the rise in photosynthesis. Belowground responses, including fine root production, nutrient foraging and soil organic matter processing, will be especially important to the integrated ecosystem response to elevated ca. Water use efficiency will increase as ca rises, potentially impacting upon soil moisture status and nutrient availability. Recruitment may be differentially altered for some functional groups, potentially decreasing ecosystem carbon storage. Whole-forest CO2 enrichment experiments are urgently needed to test predictions of tropical forest functioning under elevated ca. Smaller scale experiments in the understorey and in gaps would also be informative, and could provide stepping stones towards stand-scale manipulations.
Unenriched xylem water contribution during cellulose synthesis influenced by atmospheric demand governs the intra‐annual tree‐ring δ18O signature
Publisher: Wiley
Date: 27-09-2023
DOI: 10.1111/NPH.19278
Assessing the effects of a drought experiment on the reproductive phenology and ecophysiology of a wet tropical rainforest community
Publisher: Oxford University Press (OUP)
Date: 2023
Drought reduces the growth and health of tropical rainforest understory plants
Publisher: Elsevier BV
Date: 05-2022
Savanna fires and their impact on net ecosystem productivity in North Australia
Publisher: Wiley
Date: 25-04-2007
Forest system hydraulic conductance: partitioning tree and soil components
Publisher: Wiley
Date: 20-12-2021
DOI: 10.1111/NPH.17895
Abstract: Soil–leaf hydraulic conductance determines canopy–atmosphere coupling in vegetation models, but it is typically derived from ex‐situ measurements of stem segments and soil s les. Using a novel approach, we derive robust in‐situ estimates for whole‐tree conductance ( k tree ), ‘functional’ soil conductance ( k soil ), and ‘system’ conductance ( k system , water table to canopy), at two climatically different tropical rainforest sites. Hydraulic ‘functional rooting depth’, determined for each tree using profiles of soil water potential (Ψ soil ) and sap flux data, enabled a robust determination of k tree and k soil . k tree was compared across species, size classes, seasons, height above nearest drainage (HAND), two field sites, and to alternative representations of k tree k soil was analysed with respect to variations in site, season and HAND. k tree was lower and changed seasonally at the site with higher vapour pressure deficit (VPD) and rainfall k tree differed little across species but scaled with tree circumference r soil (1/ k soil ) ranged from 0 in the wet season to 10× less than r tree (1/ k tree ) in the dry season. VPD and not rainfall may influence plot‐level k leaf water potentials and sap flux can be used to determine k tree , k soil and k system Ψ soil profiles can provide mechanistic insights into ecosystem‐level water fluxes.
Leaf Water δ18O, δ2H and d-excess: Isoscapes for Australia
Publisher: Wiley
Date: 05-2023
DOI: 10.1002/HYP.14878
Abstract: Oxygen (δ 18 O) and hydrogen (δ 2 H) isotope ratios, and their relationship to one another ( d ‐excess) are altered as water travels from the atmosphere to the land surface, into soils and plants and back to the atmosphere. Plants return water to the atmosphere through transpiration (evaporation through the stomata), which causes isotopic fractionation concentrating the heavier isotopes ( 18 O and 2 H) in the water that remains behind in the leaves. The degree of isotopic fractionation during transpiration is controlled largely by climate, and as a result can be predicted using process‐based models and climate data. The modelled transpirational isotopic fractionation can be applied to plant source water isotopic values to predict leaf water isotope ratios and generate maps of isotopic composition, or isoscapes. This approach of mechanistic modelling has been well demonstrated in the first generation of global leaf water isoscapes ( PLoS One , 3 (6), e2447, 2008). However, use of leaf water isoscapes in fields such as hydrology, ecology, and forensics requires a new generation of updated region‐specific isoscapes. Here, we generate leaf water isoscapes of δ 18 O, δ 2 H and d ‐excess for Australia, the driest vegetated continent on Earth, where leaf water represents a critical water resource for ecosystems. These isoscapes represent an improvement over previous global isoscapes due to their higher resolution, region‐specific, empirically derived plant parameters, and non‐equilibrium corrections for water vapour isotopic composition. The new isoscapes for leaf water are evaluated relative to observed isotope ratios of leaf cellulose and cherry juice. The model predictions for annual average leaf water isotope ratios showed strong correlations with these plant tissues that integrate over time. Moreover, inclusion of region‐specific leaf temperature estimates and non‐equilibirum vapour corrections improved prediction accuracy. Regionally based isoscapes provide improved characterisations of average leaf water isotope ratios needed to support research in hydrology, plant ecophysiology, atmospheric science, ecology, and geographic provenancing of biological materials.
Leaf:wood allometry and functional traits together explain substantial growth rate variation in rainforest trees
Publisher: Oxford University Press (OUP)
Date: 16-04-2019
Abstract: Plant growth rates drive ecosystem productivity and are a central element of plant ecological strategies. For seedlings grown under controlled conditions, a large literature has firmly identified the functional traits that drive interspecific variation in growth rate. For adult plants, the corresponding knowledge is surprisingly poorly understood. Until recently it was widely assumed that the key trait drivers would be the same (e.g. specific leaf area, or SLA), but an increasing number of papers has demonstrated this not to be the case, or not generally so. New theory has provided a prospective basis for understanding these discrepancies. Here we quantified relationships between stem diameter growth rates and functional traits of adult woody plants for 41 species in an Australian tropical rainforest. From various cost-benefit considerations, core predictions included that: (i) photosynthetic rate would be positively related to growth rate (ii) SLA would be unrelated to growth rate (unlike in seedlings where it is positively related to growth) (iii) wood density would be negatively related to growth rate and (iv) leaf mass:sapwood mass ratio (LM:SM) in branches (analogous to a benefit:cost ratio) would be positively related to growth rate. All our predictions found support, particularly those for LM:SM and wood density photosynthetic rate was more weakly related to stem diameter growth rates. Specific leaf area was convincingly correlated to growth rate, in fact negatively. Together, SLA, wood density and LM:SM accounted for 52 % of variation in growth rate among these 41 species, with each trait contributing roughly similar explanatory power. That low SLA species can achieve faster growth rates than high SLA species was an unexpected result but, as it turns out, not without precedent, and easily understood via cost-benefit theory that considers whole-plant allocation to different tissue types. Branch-scale leaf:sapwood ratio holds promise as an easily measurable variable that may help to understand growth rate variation. Using cost-benefit approaches teamed with combinations of leaf, wood and allometric variables may provide a path towards a more complete understanding of growth rates under field conditions.
Temperature sensitivity of termites determines global wood decay rates
Publisher: Research Square Platform LLC
Date: 11-01-2022
DOI: 10.21203/RS.3.RS-1242094/V1
Abstract: Animals, such as termites, have largely been overlooked as global-scale drivers of biogeochemical cycles 1,2 , despite site-specific findings 3,4 . Deadwood turnover, an important component of the carbon cycle, is driven by multiple decay agents. Studies have focused on temperate systems 5,6 , where microbes dominate decay 7 . Microbial decay is sensitive to temperature, typically doubling per 10°C increase (decay effective Q 10 = ~2) 8–10 . Termites are important decayers in tropical systems 3,11–13 and differ from microbes in their population dynamics, dispersal, and substrate discovery 14–16 , meaning their climate sensitivities also differ. Using a network of 133 sites spanning 6 continents, we report the first global field-based quantification of temperature and precipitation sensitivities for termites and microbes, providing novel understandings of their response to changing climates. Temperature sensitivity of microbial decay was within previous estimates. Termite discovery and consumption were both much more sensitive to temperature (decay effective Q 10 = 6.53), leading to striking differences in deadwood turnover in areas with and without termites. Termite impacts were greatest in tropical seasonal forests and savannas and subtropical deserts. With tropicalization 17 (i.e., warming shifts to a tropical climate), the termite contribution to global wood decay will increase as more of the earth’s surface becomes accessible to termites.
AusTraits, a curated plant trait database for the Australian flora
Publisher: Springer Science and Business Media LLC
Date: 30-09-2021
DOI: 10.1038/S41597-021-01006-6
Abstract: 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 c aigns, published literature, taxonomic monographs, and in idual 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 in idual- 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.
Convergence in phosphorus constraints to photosynthesis in forests around the world
Publisher: Springer Science and Business Media LLC
Date: 25-08-2022
DOI: 10.1038/S41467-022-32545-0
Abstract: Tropical forests take up more carbon (C) from the atmosphere per annum by photosynthesis than any other type of vegetation. Phosphorus (P) limitations to C uptake are paramount for tropical and subtropical forests around the globe. Yet the generality of photosynthesis-P relationships underlying these limitations are in question, and hence are not represented well in terrestrial biosphere models. Here we demonstrate the dependence of photosynthesis and underlying processes on both leaf N and P concentrations. The regulation of photosynthetic capacity by P was similar across four continents. Implementing P constraints in the ORCHIDEE-CNP model, gross photosynthesis was reduced by 36% across the tropics and subtropics relative to traditional N constraints and unlimiting leaf P. Our results provide a quantitative relationship for the P dependence for photosynthesis for the front-end of global terrestrial C models that is consistent with canopy leaf measurements.
A sub-continental scale living laboratory
Publisher: Elsevier BV
Date: 11-2011
Thirty-eight years of CO<sub>2</sub> fertilization have outpaced growing aridity to drive greening of Australian woody ecosystems
Publisher: Copernicus GmbH
Date: 23-08-2021
DOI: 10.5194/BG-2021-218
Abstract: Abstract. Climate change is projected to increase the imbalance between the supply (precipitation) and atmospheric demand for water (i.e. increased potential evapotranspiration), stressing plants in water-limited environments. Plants may be able to offset increasing aridity because rising CO2 increases water-use-efficiency. CO2 fertilization has also been cited as one of the drivers of the widespread ‘greening’ phenomenon. However, attributing the size of this CO2 fertilization effect is complicated, due in part to a lack of long-term vegetation monitoring and interannual to decadal-scale climate variability. In this study we asked the question, how much has CO2 contributed towards greening? We focused our analysis on a broad aridity gradient spanning eastern Australia’s woody ecosystems. Next we analysed 38-years of satellite remote sensing estimates of vegetation greenness (normalized difference vegetation index, NDVI) to examine the role of CO2 in ameliorating climate change impacts. Multiple statistical techniques were applied to separate the CO2-attributable effects on greening from the changes in water supply and atmospheric aridity. Widespread vegetation greening occurred despite a warming climate, increases in vapor pressure deficit, and repeated record-breaking droughts and heatwaves. Between 1982–2019 we found that NDVI increased (median 11.3 %) across 90.5 % of the woody regions. After masking disturbance effects (e.g. fire), we statistically estimated an 11.7 % increase in NDVI attributable to CO2, broadly consistent with a hypothesized theoretical expectation of an 8.6 % increase in water-use-efficiency due to rising CO2. In contrast to reports of a weakening CO2 fertilization effect, we found no consistent temporal change in the CO2 effect. We conclude rising CO2 has mitigated the effects of increasing aridity, repeated record-breaking droughts, and record-breaking heat waves in eastern Australia. However, we were unable to determine whether trees or grasses were the primary beneficiary of the CO2 induced change in water-use-efficiency, which has implications for projecting future ecosystem resilience. A more complete understanding of how CO2 induced changes in water-use-efficiency affect trees and non-tree vegetation is needed.
Plant δ15N Correlates with the Transpiration Efficiency of Nitrogen Acquisition in Tropical Trees
Publisher: Oxford University Press (OUP)
Date: 02-09-2009
Heavy Water Fractionation during Transpiration
Publisher: Oxford University Press (OUP)
Date: 2007
A new method to measure carbon isotope composition of CO2 respired by trees: stem CO2 equilibration
Publisher: Wiley
Date: 09-11-2009
Stem diameter growth rates in a fire-prone savanna correlate with photosynthetic rate and branch-scale biomass allocation, but not specific leaf area
Publisher: Wiley
Date: 20-11-2019
DOI: 10.1111/AEC.12678
Two tropical conifers show strong growth and water-use efficiency responses to altered CO2concentration
Publisher: Oxford University Press (OUP)
Date: 30-08-2016
DOI: 10.1093/AOB/MCW162
Characterizing the O3 yield gap in the sugarcane production of SE Brazil
Publisher: Copernicus GmbH
Date: 15-05-2023
DOI: 10.5194/EGUSPHERE-EGU23-14543
Abstract: Sugarcane a vitally important crop across many tropical and subtropical regions. S& #227 o Paulo (SP) state, Brazil the largest single regional producer of both raw sugar and the production of bioethanol has experienced large-scale conversion of pasture to sugarcane production in recent decades. This predominantly rain-fed agricultural area is exposed to seasonal drought and periodic high tropospheric ozone (O3) pollution at levels known elsewhere to be detrimental to plant productivity. Given the large current extent, and planned expansion of sugarcane production to meet global demand for & #8216 green& #8217 biofuels there is a pressing need to characterize the risk of current tropospheric O3 to the sugarcane industry. This is a key step towards limiting the O3 yield gap under future climate and land use change scenarios. In this study, we therefore sought to a) derive realistic sugarcane O3 dose response functions across a full range of O3 exposure and b) model the implications of this observed O3 response across the globally important production area of SE Brazil.We found a significant and substantial impact of O3 on a range of sugarcane cultivars, including a number of commercially relevant varieties. When combined with biologically relevant predictions of O3 exposure across Brazil this allows us to predict the current regional impact of O3 on sugarcane production. We find that up to 25 million tonnes of total crop productivity a year may be lost across S& #227 o Paulo alone due to the direct impacts of O3 exposure & #8211 but that substantial differences in O3 sensitivity of different cultivars highlights the need for future work to elucidate the true impacts of O3 in this important tropical cropping system.
Covariation between oxygen and hydrogen stable isotopes declines along the path from xylem water to wood cellulose across an aridity gradient
Publisher: Wiley
Date: 07-09-2023
DOI: 10.1111/NPH.19248
Leaf manganese concentrations as a tool to assess belowground plant functioning in phosphorus-impoverished environments
Publisher: Springer Science and Business Media LLC
Date: 09-09-2020
Gas exchange and water‐use efficiency in plant canopies
Publisher: Wiley
Date: 19-12-2018
DOI: 10.1111/PLB.12939
Abstract: In this review, I first address the basics of gas exchange, water-use efficiency and carbon isotope discrimination in C
Supplementary material to "Oxygen isotope exchange between water and carbon dioxide in soils is controlled by pH, nitrate availability and microbial biomass through links to carbonic anhydras
Publisher: Copernicus GmbH
Date: 23-07-2020
Ternary effects on the gas exchange of isotopologues of carbon dioxide
Publisher: Wiley
Date: 21-02-2012
DOI: 10.1111/J.1365-3040.2012.02484.X
Abstract: The ternary effects of transpiration rate on the rate of assimilation of carbon dioxide through stomata, and on the calculation of the intercellular concentration of carbon dioxide, are now included in standard gas exchange studies. However, the equations for carbon isotope discrimination and for the exchange of oxygen isotopologues of carbon dioxide ignore ternary effects. Here we introduce equations to take them into account. The ternary effect is greatest when the leaf-to-air vapour mole fraction difference is greatest, and its impact is greatest on parameters derived by difference, such as the mesophyll resistance to CO(2) assimilation, r(m) . We show that the mesophyll resistance to CO(2) assimilation has been underestimated in the past. The impact is also large when there is a large difference in isotopic composition between the CO(2) inside the leaf and that in the air. We show that this partially reconciles estimates of the oxygen isotopic composition of CO(2) in the chloroplast and mitochondria in the light and in the dark, with values close to equilibrium with the estimated oxygen isotopic composition of water at the sites of evaporation within the leaf.
Modelling advection and diffusion of water isotopologues in leaves
Publisher: Wiley
Date: 15-06-2007
DOI: 10.1111/J.1365-3040.2007.01676.X
Abstract: We described advection and diffusion of water isotopologues in leaves in the non-steady state, applied specifically to histomatous leaves. This explains the isotopic enrichment of leaf water from the xylem to the mesophyll, and we showed how it relates to earlier models of leaf water enrichment in non-steady state. The effective length or tortuosity factor of isotopologue movement in leaves is unknown and, therefore, is a fitted parameter in the model. We compared the advection-diffusion model to previously published data sets for Lupinus angustifolius and Eucalyptus globulus. Night-time stomatal conductance was not measured in either data set and is therefore another fitted parameter. The model compared very well with the observations of bulk mesophyll water during the whole diel cycle. It compared well with the enrichment at the evaporative sites during the day but showed some deviations at night for E. globulus. It became clear from our analysis that night-time stomatal conductance should be measured in the future and that the temperature dependence of the tracer diffusivities should be accounted for. However, varying mesophyll water volume did not seem critical for obtaining a good prediction of leaf water enrichment, at least in our data sets. In addition, observations of single diurnal cycles do not seem to constrain the effective length that relates to the tortuosity of the water path in the mesophyll. Finally, we showed when simpler models of leaf water enrichment were suitable for applications of leaf water isotopes once weighted with the appropriate gas exchange flux. We showed that taking an unsuitable leaf water enrichment model could lead to large biases when cumulated over only 1 day.
Coordination of photosynthetic traits across soil and climate gradients
Publisher: Wiley
Date: 16-11-2022
DOI: 10.1111/GCB.16501
Abstract: “Least‐cost theory” posits that C 3 plants should balance rates of photosynthetic water loss and carboxylation in relation to the relative acquisition and maintenance costs of resources required for these activities. Here we investigated the dependency of photosynthetic traits on climate and soil properties using a new Australia‐wide trait dataset spanning 528 species from 67 sites. We tested the hypotheses that plants on relatively cold or dry sites, or on relatively more fertile sites, would typically operate at greater CO 2 drawdown (lower ratio of leaf internal to ambient CO 2 , C i : C a ) during light‐saturated photosynthesis, and at higher leaf N per area (N area ) and higher carboxylation capacity ( V cmax 25 ) for a given rate of stomatal conductance to water vapour, g sw . These results would be indicative of plants having relatively higher water costs than nutrient costs. In general, our hypotheses were supported. Soil total phosphorus (P) concentration and (more weakly) soil pH exerted positive effects on the N area – g sw and V cmax 25 – g sw slopes, and negative effects on C i : C a . The P effect strengthened when the effect of climate was removed via partial regression. We observed similar trends with increasing soil cation exchange capacity and clay content, which affect soil nutrient availability, and found that soil properties explained similar amounts of variation in the focal traits as climate did. Although climate typically explained more trait variation than soil did, together they explained up to 52% of variation in the slope relationships and soil properties explained up to 30% of the variation in in idual traits. Soils influenced photosynthetic traits as well as their coordination. In particular, the influence of soil P likely reflects the Australia's geologically ancient low‐relief landscapes with highly leached soils. Least‐cost theory provides a valuable framework for understanding trade‐offs between resource costs and use in plants, including limiting soil nutrients.
Critical review: incorporating the arrangement of mitochondria and chloroplasts into models of photosynthesis and carbon isotope discrimination
Publisher: Springer Science and Business Media LLC
Date: 06-04-2019
DOI: 10.1007/S11120-019-00635-8
Abstract: The arrangement of mitochondria and chloroplasts, together with the relative resistances of cell wall and chloroplast, determine the path of diffusion out of the leaf for (photo)respired CO
Oxygen isotope composition of phloem sap in relation to leaf water in Ricinus communis
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/FP03137
Abstract: We measured the oxygen isotope composition of both the water and dry matter components of phloem sap exported from photosynthesising Ricinus communis L. leaves. The 18O / 16O composition of exported dry matter matched almost exactly that expected for equilibrium with average lamina leaf water (leaf water exclusive of water associated with primary veins) with an isotope effect of αo=1.027, where αo=Ro / Rw , and Ro and Rw are 18O / 16O of organic molecules and water, respectively. Average lamina leaf water was enriched by 14–22‰ compared with source water under our experimental conditions, and depleted by 4–7‰, compared with evaporative site water. This showed that it is the average lamina leaf water 18O / 16O signal that is exported from photosynthesising leaves rather than a signal more closely related to that of evaporative site water or source water. Additionally, we found that water exported in phloem sap from photosynthesising leaves was enriched compared with source water the mean phloem water enrichment observed for leaf petioles was 4.0 ± 1.5‰ (mean ± 1 s.d., n = 27). Phloem water collected from stem bases was also enriched compared with source water. However, the enrichment was approximately 0.8 times that observed for leaf petioles, suggesting some mixing between enriched phloem water and unenriched xylem water occurred during translocation. Results validated the assumption that organic molecules exported from photosynthesising leaves are enriched by 27‰ compared with average lamina leaf water. Furthermore, results suggest that the potential influence of enriched phloem water should be considered when interpreting the 18O / 16O signatures of plant organic material and plant cellulose.
Carbon isotope discrimination in photosynthetic bark
Publisher: Springer Science and Business Media LLC
Date: 06-2001
Abstract: We developed and tested a theoretical model describing carbon isotope discrimination during photosynthesis in tree bark. Bark photosynthesis reduces losses of respired CO
AusTraits – a curated plant trait database for the Australian flora
Publisher: Cold Spring Harbor Laboratory
Date: 07-01-2021
DOI: 10.1101/2021.01.04.425314
Abstract: 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 c aigns, published literature, taxonomic monographs, and in idual 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 in idual-, 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.
On the isotopic composition of leaf water in the non-steady state
Publisher: CSIRO Publishing
Date: 2005
DOI: 10.1071/FP04232
Abstract: An expression is derived for the isotopic composition of water in leaves under conditions where the composition of water entering the leaf is not necessarily the same as that of water being transpired. The treatment is simplified and considers the average composition of the lamina and of the sites of evaporation. The concept of ‘isostorage’ is introduced as the product of leaf water content and the isotopic enrichment of leaf water above source water. It is shown that the rate of increase of isostorage is minus the ‘isoflux’ through the stomata, with the latter expressed as the product of the transpiration flux and the enrichment of the transpired water beyond source water. The approach of the isostorage to the steady state depends on the deviation of the isotopic enrichment of water at the evaporating sites from the steady value, and on the gross (one way) diffusive flux out of the leaf. To achieve model closure, it is assumed that the relationship between leaf water enrichment and that at the sites of evaporation depends on the radial Péclet number in the same manner as in the steady state. The equations have an analytical solution, and we also show how to calculate the results simply using a commonly available computer tool. The form of the equations emphasises that the one-way fluxes of water into and out of the stomata must sometimes be considered separately, rather than as a net outward flux. In this narrow sense we come to the interesting conclusion that more water usually enters the leaf from the air than from the roots.
Nitrogen to phosphorus ratio of plant biomass versus soil solution in a tropical pioneer tree, Ficus insipida
Publisher: Oxford University Press (OUP)
Date: 30-06-2010
DOI: 10.1093/JXB/ERQ183
Predicted alteration of vertebrate communities in response to climate‐induced elevational shifts
Publisher: Wiley
Date: 04-2022
DOI: 10.1111/DDI.13514
Abstract: Climate change is driving species to migrate to novel areas as current environments become unsuitable. As a result, species distributions have shifted uphill in montane ecosystems globally. Heterogeneous dispersal rates among shifting species could result in complex changes to community assemblages. For ex le, interspecific differences in dispersal ability could lead to the disruption, or creation, of species interactions and processes within communities, likely lifying the impact of climate change on ecosystems. Here, we studied the dispersal success of vertebrate species in a tropical montane ecosystem under a climate‐induced uphill shift and assessed the derived impacts on community structures. The Australian Wet Tropics bioregion. We simulated the uphill shift of 7613 community assemblages across the elevational gradient using thermal resistance layers for movement analyses. Dispersal success was calculated as the probability of shifting given species’ dispersal ability and landscape composition. We then used dissimilarity indices to measure the potential changes in community structures resulting from the heterogeneous dispersal success among migrating species. Dispersal success was strongly influenced by species’ dispersal ability, landscape composition and climate change. The heterogeneous dispersal success among migrating species induced marked temporal changes between community assemblages along the elevational gradient. The local extinction rate (i.e. the proportion of species unable to shift) was especially remarkable at high elevations, suggesting potential mass local extinctions of upland species. Furthermore, the increasing local extinction rate with elevation resulted in substantial declines in species co‐occurrence in high‐altitude ecosystems. Our study highlights the escalating impact of climate change on community assemblages in response to climate‐induced elevational shifts, providing a classic ex le of the "escalator to extinction." Future predictions of the impacts of climate change on ecosystems will benefit from improvements in understanding species interactions, population dynamics and species potential to adapt to a changing environment.
Oxygen isotope exchange between water and carbon dioxide in soils is controlled by pH, nitrate and microbial biomass through links to carbonic anhydrase activity
Publisher: Copernicus GmbH
Date: 02-06-2021
Abstract: Abstract. The oxygen isotope composition of atmospheric carbon dioxide (CO2) is intimately linked to large-scale variations in the cycling of CO2 and water across the Earth's surface. Understanding the role the biosphere plays in modifying the oxygen isotope composition of atmospheric CO2 is particularly important as this isotopic tracer has the potential to constrain estimates of important processes such as gross primary production at large scales. However, constraining the atmospheric mass budget for the oxygen isotope composition of CO2 also requires that we understand better the contribution of soil communities and how they influence the rate of oxygen isotope exchange between soil water and CO2 (kiso) across a wide range of soil types and climatic zones. As the carbonic anhydrases (CAs) group of enzymes enhances the rate of CO2 hydration within the water-filled pore spaces of soils, it is important to develop understanding of how environmental drivers can impact kiso through changes in their activity. Here we estimate kiso and measure associated soil properties in laboratory incubation experiments using 44 soils s led from sites across western Eurasia and north-eastern Australia. Observed values for kiso always exceeded theoretically derived uncatalysed rates, indicating a significant influence of CAs on the variability of kiso across the soils studied. We identify soil pH as the principal source of variation, with greater kiso under alkaline conditions suggesting that shifts in microbial community composition or intra–extra-cellular dissolved inorganic carbon gradients induce the expression of more or higher activity forms of CAs. We also show for the first time in soils that the presence of nitrate under naturally acidic conditions reduces kiso, potentially reflecting a direct or indirect inhibition of CAs. This effect appears to be supported by a supplementary ammonium nitrate fertilisation experiment conducted on a subset of the soils. Greater microbial biomass also increased kiso under a given set of chemical conditions, highlighting a putative link between CA expression and the abundance of soil microbes. These data provide the most extensive analysis of spatial variations in soil kiso to date and indicate the key soil trait datasets required to predict variations in kiso at large spatial scales, a necessary next step to constrain the important role of soil communities in the atmospheric mass budget of the oxygen isotope composition of CO2.
tri-PRI: A three band reflectance index tracking dynamic photoprotective mechanisms in a mature eucalypt forest
Publisher: Elsevier BV
Date: 07-2019
Vapour pressure deficit modulates hydraulic function and structure of tropical rainforests under nonlimiting soil water supply
Publisher: Wiley
Date: 14-09-2023
DOI: 10.1111/NPH.19257
One year of spectroscopic high-frequency measurements of atmospheric CO2, CH4, H2O and δ13C-CO2 at an Australian Savanna site
Publisher: Wiley
Date: 05-10-2022
DOI: 10.1002/GDJ3.180
Abstract: We provide a 1‐year dataset of atmospheric surface CO 2 , CH 4 and H 2 O concentrations and δ 13 C‐CO 2 values from an Australian savanna site. These semi‐arid ecosystems act as carbon sinks in wet years but the persistence of the sink in dry years is uncertain. The dataset can be used to constrain uncertainties in modelling of greenhouse gas budgets, improve algorithms for satellite measurements and characterize the role of vegetation and soil in modulating atmospheric CO 2 concentrations. We found pronounced seasonal variations in daily mean CO 2 concentrations with an increase (by 5–7 ppmv) after the first rainfall of the wet season in early December with peak concentrations maintained until late January. The CO 2 increase reflected the initiation of rapid microbial respiration from soil and vegetation sources upon initial wetting. As the wet season progressed, daily CO 2 concentrations were variable, but generally decreased back to dry season levels as CO 2 assimilation by photosynthesis increased. Mean daily concentrations of CH 4 increased in the wet season by up to 0.2 ppmv relative to dry season levels as the soil profile became waterlogged after heavy rainfall events. During the dry season there was regular cycling between maximum CO 2 /minimum δ 13 C‐CO 2 at night and minimum CO 2 /maximum δ 13 C‐CO 2 during the day. In the wet season diel patterns were less regular in response to variable cloud cover and rainfall. CO 2 isotope data showed that in the wet season, surface CO 2 was predominantly a two‐component mixture influenced by C 3 plant assimilation (day) and soil lant respiration (night), while regional background air from higher altitudes represented an additional CO 2 source in the dry season. Higher wind speeds during the dry season increased vertical mixing compared to the wet season. In addition, night‐time advection of high‐altitude air during low temperature conditions also promoted mixing in the dry season.
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