ORCID Profile
0000-0002-0334-5464
Current Organisation
Australian National University
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: American Geophysical Union (AGU)
Date: 05-2014
DOI: 10.1002/2013JG002553
Publisher: Wiley
Date: 11-04-2019
DOI: 10.1111/NPH.15805
Publisher: Wiley
Date: 12-2016
DOI: 10.1002/ECS2.1631
Publisher: Wiley
Date: 06-03-2017
DOI: 10.1111/GCB.13643
Abstract: Multifactor experiments are often advocated as important for advancing terrestrial biosphere models (TBMs), yet to date, such models have only been tested against single-factor experiments. We applied 10 TBMs to the multifactor Prairie Heating and CO
Publisher: Wiley
Date: 22-03-2017
DOI: 10.1111/GCB.13602
Abstract: Determining whether the terrestrial biosphere will be a source or sink of carbon (C) under a future climate of elevated CO
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1CP05300K
Abstract: Room-temperature sodium sulfur batteries (RT-NSBs) are among the promising candidates for large-scale energy storage applications because of the natural abundance of the electrode materials and impressive energy density.
Publisher: Elsevier BV
Date: 08-2023
Publisher: Oxford University Press (OUP)
Date: 2014
Publisher: Oxford University Press (OUP)
Date: 13-04-2015
Abstract: How trees sense source-sink carbon balance remains unclear. One potential mechanism is a feedback from non-structural carbohydrates regulating photosynthesis and removing excess as waste respiration when the balance of photosynthesis against growth and metabolic activity changes. We tested this carbohydrate regulation of photosynthesis and respiration using branch girdling in four tree species in a wet tropical rainforest in Costa Rica. Because girdling severs phloem to stop carbohydrate export while leaving xylem intact to allow photosynthesis, we expected carbohydrates to accumulate in leaves to simulate a carbon imbalance. We varied girdling intensity by removing phloem in increments of one-quarter of the circumference (zero, one--quarter, half, three-quarters, full) and surrounded a target branch with fully girdled ones to create a gradient in leaf carbohydrate content. Light saturated photosynthesis rate was measured in situ, and foliar respiration rate and leaf carbohydrate content were measured after destructive harvest at the end of the treatment. Girdling intensity created no consistent or strong responses in leaf carbohydrates. Glucose and fructose slightly increased in all species by 3.4% per one-quarter girdle, total carbon content and leaf mass per area increased only in one species by 5.4 and 5.5% per one-quarter girdle, and starch did not change. Only full girdling lowered photosynthesis in three of four species by 59-69%, but the decrease in photosynthesis was unrelated to the increase in glucose and fructose content. Girdling did not affect respiration. The results suggest that leaf carbohydrate content remains relatively constant under carbon imbalance, and any changes are unlikely to regulate photosynthesis or respiration. Because girdling also stops the export of hormones and reactive oxygen species, girdling may induce physiological changes unrelated to carbohydrate accumulation and may not be an effective method to study carbohydrate feedback in leaves. In three species, removal of three-quarters of phloem area did not cause leaf carbohydrates to accumulate nor did it change photosynthesis or respiration, suggesting that phloem transport is flexible and transport rate per unit phloem can rapidly increase under an increase in carbohydrate supply relative to phloem area. Leaf carbohydrate content thus may be decoupled from whole plant carbon balance by phloem transport in some species, and carbohydrate regulation of photosynthesis and respiration may not be as common in trees as previous girdling studies suggest. Further studies in carbohydrate regulation should avoid using girdling as girdling can decrease photosynthesis through unintended means without the tested mechanisms of accumulating leaf carbohydrates.
Publisher: Wiley
Date: 09-05-2023
Abstract: To determine the impact of the COVID‐19 state‐wide lockdown on ED presentations for older adults in Queensland, Australia. A retrospective cohort study pertaining to adults aged 70+ years who presented to Queensland public hospital EDs across three separate time periods 11 March to 30 June 2018 and 2019 (pre‐pandemic average), 2020 (COVID‐19 state‐wide lockdown) and 2021 (post‐state‐wide lockdown). The primary outcome was change in presentation rates to ED. Secondary outcomes included change in triage category rates, length of stay (LOS), diagnosis and disposition. There was 380 854 older adult presentations. During the COVID‐19 state‐wide lockdown, ED presentation rates decreased by 12.5% (incidence rate ratio 0.875 [95% confidence interval 0.867–0.883]). All triage category presentation rates decreased, as did ED LOS and reasons for presentation, except sepsis and disorders of the nervous system. In the post‐state‐wide lockdown period a 22% (incidence rate ratio 1.22 [95% confidence interval 1.21–1.23]) increase in the presentation rate was observed and presentations in all triage categories increased. ED LOS increased to longer than pre‐pandemic ( P 0.001). Respiratory presentations increased by 346%. Patients who ‘did not wait’ increased by 212% and ED mortality rose by 42% compared to during the lockdown. There was a significant decrease in presentation rates to EDs during the COVID‐19 state‐wide lockdown for the older population, followed by an increase in presentation rates, longer ED LOS, and an increased ED mortality rate, in the post‐state‐wide lockdown period. It is important to ensure older adults continue to seek appropriate, timely medical care, during a pandemic.
Publisher: Wiley
Date: 06-05-2020
DOI: 10.1111/NPH.16579
Publisher: Copernicus GmbH
Date: 23-10-2017
Abstract: Abstract. For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely responding to the rapid global warming, intensifying water stress, and increasing atmospheric CO2 levels. Projections of the future C balance of the tropics vary widely among global models. A current effort of the modeling community, the ILAMB (International Land Model Benchmarking) project, is to compile robust observations that can be used to improve the accuracy and realism of the land models for all major biomes. Our goal with this paper is to identify field observations of tropical-forest ecosystem C stocks and fluxes, and of their long-term trends and climatic and CO2 sensitivities, that can serve this effort. We propose criteria for reference-level field data from this biome and present a set of documented ex les from old-growth lowland tropical forests. We offer these as a starting point towards the goal of a regularly updated consensus set of benchmark field observations of C cycling in tropical forests.
Publisher: Elsevier BV
Date: 12-2012
Publisher: Wiley
Date: 21-05-2014
DOI: 10.1111/NPH.12847
Abstract: Elevated atmospheric CO 2 concentration ( eCO 2 ) has the potential to increase vegetation carbon storage if increased net primary production causes increased long‐lived biomass. Model predictions of eCO 2 effects on vegetation carbon storage depend on how allocation and turnover processes are represented. We used data from two temperate forest free‐air CO 2 enrichment ( FACE ) experiments to evaluate representations of allocation and turnover in 11 ecosystem models. Observed eCO 2 effects on allocation were dynamic. Allocation schemes based on functional relationships among biomass fractions that vary with resource availability were best able to capture the general features of the observations. Allocation schemes based on constant fractions or resource limitations performed less well, with some models having unintended outcomes. Few models represent turnover processes mechanistically and there was wide variation in predictions of tissue lifespan. Consequently, models did not perform well at predicting eCO 2 effects on vegetation carbon storage. Our recommendations to reduce uncertainty include: use of allocation schemes constrained by biomass fractions careful testing of allocation schemes and synthesis of allocation and turnover data in terms of model parameters. Data from intensively studied ecosystem manipulation experiments are invaluable for constraining models and we recommend that such experiments should attempt to fully quantify carbon, water and nutrient budgets.
Publisher: Wiley
Date: 14-10-2020
DOI: 10.1111/NPH.16929
Abstract: Short‐term temperature response curves of leaf dark respiration ( R–T ) provide insights into a critical process that influences plant net carbon exchange. This includes how respiratory traits acclimate to sustained changes in the environment. Our study analysed 860 high‐resolution R–T (10–70°C range) curves for: (a) 62 evergreen species measured in two contrasting seasons across several field sites/biomes and (b) 21 species (subset of those s led in the field) grown in glasshouses at 20°C : 15°C, 25°C : 20°C and 30°C : 25°C, day : night. In the field, across all sites/seasons, variations in R 25 (measured at 25°C) and the leaf T where R reached its maximum ( T max ) were explained by growth T (mean air‐ T of 30‐d before measurement), solar irradiance and vapour pressure deficit, with growth T having the strongest influence. R 25 decreased and T max increased with rising growth T across all sites and seasons with the single exception of winter at the cool‐temperate rainforest site where irradiance was low. The glasshouse study confirmed that R 25 and T max thermally acclimated. Collectively, the results suggest: (1) thermal acclimation of leaf R is common in most biomes and (2) the high T threshold of respiration dynamically adjusts upward when plants are challenged with warmer and hotter climates.
Publisher: Wiley
Date: 06-02-2022
DOI: 10.1111/PCE.14267
Abstract: Our understanding of the regulation of respiration in C 4 plants, where mitochondria play different roles in the different types of C 4 photosynthetic pathway, remains limited. We examined how leaf dark respiration rates ( R dark ), in the presence and absence of added malate, vary in monocots representing the three classical biochemical types of C 4 photosynthesis (NADP‐ME, NAD‐ME and PCK) using intact leaves and extracted bundle sheath strands. In particular, we explored to what extent rates of R dark are associated with mitochondrial number, volume and ultrastructure. Based on examination of a single species per C 4 type, we found that the respiratory response of NAD‐ME and PCK type bundle sheath strands to added malate was associated with differences in mitochondrial number, volume, and/or ultrastructure, while NADP‐ME type bundle sheath strands did not respond to malate addition. In general, mitochondrial traits reflected the contributions mitochondria make to photosynthesis in the three C 4 types. However, despite the obvious differences in mitochondrial traits, no clear correlation was observed between these traits and R dark . We suggest that R dark is primarily driven by cellular maintenance demands and not mitochondrial composition per se, in a manner that is somewhat independent of mitochondrial organic acid cycling in the light.
Publisher: Wiley
Date: 13-11-2021
DOI: 10.1111/NPH.17818
Abstract: C 4 photosynthesis involves a series of biochemical and anatomical traits that significantly improve plant productivity under conditions that reduce the efficiency of C 3 photosynthesis. We explore how evolution of the three classical biochemical types of C 4 photosynthesis (NADP‐ME, NAD‐ME and PCK types) has affected the functions and properties of mitochondria. Mitochondria in C 4 NAD‐ME and PCK types play a direct role in decarboxylation of metabolites for C 4 photosynthesis. Mitochondria in C 4 PCK type also provide ATP for C 4 metabolism, although this role for ATP provision is not seen in NAD‐ME type. Such involvement has increased mitochondrial abundance/size and associated enzymatic capacity, led to changes in mitochondrial location and ultrastructure, and altered the role of mitochondria in cellular carbon metabolism in the NAD‐ME and PCK types. By contrast, these changes in mitochondrial properties are absent in the C 4 NADP‐ME type and C 3 leaves, where mitochondria play no direct role in photosynthesis. From an eco‐physiological perspective, rates of leaf respiration in darkness vary considerably among C 4 species but does not differ systematically among the three C 4 types. This review outlines further mitochondrial research in key areas central to the engineering of the C 4 pathway into C 3 plants and to the understanding of variation in rates of C 4 dark respiration.
Publisher: Springer Science and Business Media LLC
Date: 14-02-2019
DOI: 10.1038/S41467-019-08348-1
Abstract: Increasing atmospheric CO 2 stimulates photosynthesis which can increase net primary production (NPP), but at longer timescales may not necessarily increase plant biomass. Here we analyse the four decade-long CO 2 -enrichment experiments in woody ecosystems that measured total NPP and biomass. CO 2 enrichment increased biomass increment by 1.05 ± 0.26 kg C m −2 over a full decade, a 29.1 ± 11.7% stimulation of biomass gain in these early-secondary-succession temperate ecosystems. This response is predictable by combining the CO 2 response of NPP (0.16 ± 0.03 kg C m −2 y −1 ) and the CO 2 -independent, linear slope between biomass increment and cumulative NPP (0.55 ± 0.17). An ensemble of terrestrial ecosystem models fail to predict both terms correctly. Allocation to wood was a driver of across-site, and across-model, response variability and together with CO 2 -independence of biomass retention highlights the value of understanding drivers of wood allocation under ambient conditions to correctly interpret and predict CO 2 responses.
Publisher: Copernicus GmbH
Date: 05-05-2017
DOI: 10.5194/BG-2017-169
Abstract: Abstract. For more accurate projections of both the global carbon (C) cycle and the changing climate, a critical current need is to improve the representation of tropical forests in Earth system models. Tropical forests exchange more C, energy, and water with the atmosphere than any other class of land ecosystems. Further, tropical-forest C cycling is likely responding to the rapid global warming, intensifying water-stress, and increasing atmospheric CO2 levels. Projections of the future C balance of the tropics vary widely among global models. A current effort of the modeling community, ILAMB (the International Land Model Benchmarking Project), is to compile robust observations that can be used to improve the accuracy and realism of the land models for all major biomes. Our goal with this paper is to identify field observations of tropical-forest ecosystem C stocks and fluxes that can support this effort. We propose criteria for reference-level field data from this biome and present a set of documented ex les from old-growth lowland tropical forests. We offer these as a starting point towards the goal of a regularly updated consensus set of benchmark field observations of C-cycling in tropical forests.
Publisher: Elsevier BV
Date: 11-2023
Publisher: Wiley
Date: 08-2018
DOI: 10.1002/ECS2.2370
Publisher: Oxford University Press (OUP)
Date: 16-01-2015
Abstract: As tropical forests respond to environmental change, autotrophic respiration may consume a greater proportion of carbon fixed in photosynthesis at the expense of growth, potentially turning the forests into a carbon source. Predicting such a response requires that we measure and place autotrophic respiration in a complete carbon budget, but extrapolating measurements of autotrophic respiration from chambers to ecosystem remains a challenge. High plant species ersity and complex canopy structure may cause respiration rates to vary and measurements that do not account for this complexity may introduce bias in extrapolation more detrimental than uncertainty. Using experimental plantations of four native tree species with two canopy layers, we examined whether species and canopy layers vary in foliar respiration and wood CO2 efflux and whether the variation relates to commonly used scalars of mass, nitrogen (N), photosynthetic capacity and wood size. Foliar respiration rate varied threefold between canopy layers, ∼0.74 μmol m(-2) s(-1) in the overstory and ∼0.25 μmol m(-2) s(-1) in the understory, but little among species. Leaf mass per area, N and photosynthetic capacity explained some of the variation, but height explained more. Chamber measurements of foliar respiration thus can be extrapolated to the canopy with rates and leaf area specific to each canopy layer or height class. If area-based rates are s led across canopy layers, the area-based rate may be regressed against leaf mass per area to derive the slope (per mass rate) to extrapolate to the canopy using the total leaf mass. Wood CO2 efflux varied 1.0-1.6 μmol m(-2) s(-1) for overstory trees and 0.6-0.9 μmol m(-2) s(-1) for understory species. The variation in wood CO2 efflux rate was mostly related to wood size, and little to species, canopy layer or height. Mean wood CO2 efflux rate per surface area, derived by regressing CO2 efflux per mass against the ratio of surface area to mass, can be extrapolated to the stand using total wood surface area. The temperature response of foliar respiration was similar for three of the four species, and wood CO2 efflux was similar between wet and dry seasons. For these species and this forest, vertical s ling may yield more accurate estimates than would temporal s ling.
Publisher: Wiley
Date: 19-08-2013
DOI: 10.1111/NPH.12440
Abstract: The rhizosphere priming effect ( RPE ) is a mechanism by which plants interact with soil functions. The large impact of the RPE on soil organic matter decomposition rates (from 50% reduction to 380% increase) warrants similar attention to that being paid to climatic controls on ecosystem functions. Furthermore, global increases in atmospheric CO 2 concentration and surface temperature can significantly alter the RPE . Our analysis using a game theoretic model suggests that the RPE may have resulted from an evolutionarily stable mutualistic association between plants and rhizosphere microbes. Through model simulations based on microbial physiology, we demonstrate that a shift in microbial metabolic response to different substrate inputs from plants is a plausible mechanism leading to positive or negative RPE s. In a case study of the Duke Free‐Air CO 2 Enrichment experiment, performance of the PhotoCent model was significantly improved by including an RPE ‐induced 40% increase in soil organic matter decomposition rate for the elevated CO 2 treatment – demonstrating the value of incorporating the RPE into future ecosystem models. Overall, the RPE is emerging as a crucial mechanism in terrestrial ecosystems, which awaits substantial research and model development. Contents Summary 31 I. Introduction 31 II. Magnitude and driving variables of the rhizosphere priming effect 32 III. Will global environmental change alter the RPE? 34 IV. A game theoretic model: is priming the result of evolutionarily stable strategies? 35 V. A microbial physiology‐based model: simulating positive and negative RPEs 37 VI. A case study: matching simulation results with observations at the Duke FACE 38 VII. Research needs and future perspectives 39 Acknowledgements 41 References 41
Publisher: Wiley
Date: 07-06-2020
DOI: 10.1111/NPH.16661
Publisher: SPIE
Date: 04-09-2015
DOI: 10.1117/12.2188206
Publisher: Elsevier BV
Date: 06-2015
Publisher: American Geophysical Union (AGU)
Date: 04-2015
DOI: 10.1002/2014GB004995
Publisher: Wiley
Date: 14-12-2019
DOI: 10.1111/NPH.15576
Abstract: Contents Summary 670 I. Introduction 671 II. Principle 1 - Plant respiration performs three distinct functions 673 III. Principle 2 - Metabolic pathway flexibility underlies plant respiratory performance 676 IV. Principle 3 - Supply and demand interact over time to set plant respiration rate 677 V. Principle 4 - Plant respiratory acclimation involves adjustments in enzyme capacities 679 VI. Principle 5 - Respiration is a complex trait that helps to define, and is impacted by, plant lifestyle strategies 680 VII. Future directions 680 Acknowledgements 682 References 682 SUMMARY: Respiration is a core biological process that has important implications for the biochemistry, physiology, and ecology of plants. The study of plant respiration is thus conducted from several different perspectives by a range of scientific disciplines with dissimilar objectives, such as metabolic engineering, crop breeding, and climate-change modelling. One aspect in common among the different objectives is a need to understand and quantify the variation in respiration across scales of biological organization. The central tenet of this review is that different perspectives on respiration can complement each other when connected. To better accommodate interdisciplinary thinking, we identify distinct mechanisms which encompass the variation in respiratory rates and functions across biological scales. The relevance of these mechanisms towards variation in plant respiration are explained in the context of five core principles: (1) respiration performs three distinct functions (2) metabolic pathway flexibility underlies respiratory performance (3) supply and demand interact over time to set respiration rates (4) acclimation involves adjustments in enzyme capacities and (5) respiration is a complex trait that helps to define, and is impacted by, plant lifestyle strategies. We argue that each perspective on respiration rests on these principles to varying degrees and that broader appreciation of how respiratory variation occurs can unite research across scales.
No related grants have been discovered for Shinichi Asao.