ORCID Profile
0000-0001-5728-9827
Current Organisation
Western Sydney University - Hawkesbury Campus
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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)
Global Change Biology | Ecosystem Function | Ecological Physiology | Ecological Applications | Global Change Biology | Other Biological Sciences | Terrestrial Ecology | Ecology | Ecological Impacts of Climate Change | Plant Physiology | Photogrammetry and Remote Sensing | Environmental Science and Management | Ecology And Evolution Not Elsewhere Classified | Plant Biology | Management And Environment | Terrestrial Ecology | Plant Physiology | Conservation And Biodiversity |
ANZSRC Socio-Economic Objective (SEO)
Land and water management | Ecosystem Adaptation to Climate Change | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Forest and Woodlands Land Management | Climate change | Flora, Fauna and Biodiversity at Regional or Larger Scales | Global climate change adaptation measures | Ecosystem Assessment and Management of Forest and Woodlands Environments | Living resources (flora and fauna) | Native Forests | Land and water management | Rehabilitation/reafforestation | Management of Water Consumption by Plant Production | Sparseland, Permanent Grassland and Arid Zone Land and Water Management | Natural Hazards in Forest and Woodlands Environments | Forest and Woodlands Water Management | Mountain and High Country Land and Water Management | Forest and Woodlands Flora, Fauna and Biodiversity
Related Links
Publications
Xylem embolism measured retrospectively is linked to canopy dieback in natural populations of Eucalyptus piperita following drought
Publisher: Oxford University Press (OUP)
Date: 11-05-2018
Abstract: Manipulative experiments have suggested that embolism-induced hydraulic impairment underpins widespread tree mortality during extreme drought, yet in situ evidence is rare. One month after drought-induced leaf and branch dieback was observed in field populations of Eucalyptus piperita Sm. in the Blue Mountains (Australia), we measured the level of native stem embolism and characterized the extent of leaf death in co-occurring dieback and healthy (non-dieback) trees. We found that canopy dieback-affected trees showed significantly higher levels of native embolism (26%) in tertiary order branchlets than healthy trees (11%). Furthermore, there was a significant positive correlation (R2 = 0.51) between the level of leaf death and the level of native embolism recorded in branchlets from dieback-affected trees. This retrospective study suggests that hydraulic failure was the primary mechanism of leaf and branch dieback in response to a natural drought event in the field. It also suggests that post-drought embolism refilling is minimal or absent in this species of eucalypt.
Analyzing the impact of heterogeneous blocks on FPGA placement quality
Publisher: IEEE
Date: 12-2015
Tag Disentangled Generative Adversarial Network for Object Image Re-rendering
Publisher: International Joint Conferences on Artificial Intelligence Organization
Date: 08-2017
Abstract: In this paper, we propose a principled Tag Disentangled Generative Adversarial Networks (TD-GAN) for re-rendering new images for the object of interest from a single image of it by specifying multiple scene properties (such as viewpoint, illumination, expression, etc.). The whole framework consists of a disentangling network, a generative network, a tag mapping net, and a discriminative network, which are trained jointly based on a given set of images that are completely artially tagged (i.e., supervised/semi-supervised setting). Given an input image, the disentangling network extracts disentangled and interpretable representations, which are then used to generate images by the generative network. In order to boost the quality of disentangled representations, the tag mapping net is integrated to explore the consistency between the image and its tags. Furthermore, the discriminative network is introduced to implement the adversarial training strategy for generating more realistic images. Experiments on two challenging datasets demonstrate the state-of-the-art performance of the proposed framework in the problem of interest.
Comprehensive ecosystem model‐data synthesis using multiple data sets at two temperate forest free‐air CO2 enrichment experiments: Model performance at ambient CO2 concentration
Publisher: American Geophysical Union (AGU)
Date: 05-2014
DOI: 10.1002/2013JG002553
Applying the Concept of Ecohydrological Equilibrium to Predict Steady State Leaf Area Index
Publisher: American Geophysical Union (AGU)
Date: 08-2018
DOI: 10.1029/2017MS001169
Are worry, rumination, and post-event processing one and the same?. Development of the repetitive thinking questionnaire.
Publisher: Elsevier BV
Date: 06-2010
The AusTraits Plant Dictionary
Publisher: Cold Spring Harbor Laboratory
Date: 18-06-2023
DOI: 10.1101/2023.06.16.545047
Abstract: Traits with intuitive names, a clear scope and explicit description are essential for all trait databases. Reanalysis of data from a single database, or analyses that integrate data across multiple databases, can only occur if researchers are confident the trait concepts are consistent within and across sources. The lack of a unified, comprehensive resource for plant trait definitions has previously limited the utility of trait databases. Here we describe the AusTraits Plant Dictionary (APD), which extends the trait definitions included in the new trait database AusTraits. The development process of the APD included three steps: review and formalisation of the scope of each trait and the accompanying trait description addition of trait meta-data and publication in both human and machine-readable forms. Trait definitions include keywords, references and links to related trait concepts in other databases, and the traits are grouped into a hierarchy for easy searching. As well as improving the usability of AusTraits, the Dictionary will foster the integration of trait data across global and regional plant trait databases.
The carbon cost of the 2019–20 Australian fires varies with fire severity and forest type
Publisher: Wiley
Date: 28-05-2022
DOI: 10.1111/GEB.13548
Abstract: To estimate loss of above‐ground carbon (AGC) and conversion of live carbon to dead carbon following understorey and canopy fire. South‐eastern Australia. 2019–2020. Four widespread resprouting eucalypt forests. Above‐ground carbon was measured in 15 plots in each of four forest types one‐year post‐fire. We also assessed topkill, that is, trees subject to canopy loss that failed to resprout epicormically. While canopy fire was associated with greater declines in AGC than understorey fire, this was only statistically significant for only one forest type, where AGC declined from 154 to 85 Mg C ha −1 following canopy fire. Significant post‐fire increases in dead AGC were observed in one forest type, where dead carbon increased from 22 to 60% after canopy fire. Topkill of trees following canopy fire (48–78% of stems) was higher than topkill after understorey fire (36–53% of stems) and in unburnt forest (12–55%). Topkill occurred primarily in small‐diameter stems. Consequently, there was no effect of fire on the proportion of dead AGC in trees, with the exception of the forest with lowest productivity (i.e., lowest biomass) and lowest annual rainfall, where dead tree carbon increased from 8% in unburnt forest to 13 and 53% after understorey and canopy fire, respectively. AGC in understorey vegetation and coarse woody debris was similar or lower in burnt compared with unburnt forest. Litter carbon was significantly lower and pyrogenic carbon significantly higher in burnt forest, with no difference between understorey and canopy fire. While increased fire severity was associated with increased changes to carbon stocks, there were differences among forest types. Specifically, the driest forest type had the highest rates of topkill following canopy fire. These results highlight the importance of spatial variability in fire severity and forest type in determining the effects of fire on carbon stocks.
The relationship between interpersonal problems, negative cognitions, and outcomes from cognitive behavioral group therapy for depression
Publisher: Elsevier BV
Date: 09-2013
Multiple measurements constrain estimates of net carbon exchange by a Eucalyptus forest
Publisher: Elsevier BV
Date: 03-2009
Design and use of a database of model parameters from elevated [CO2 ] experiments
Publisher: Elsevier BV
Date: 12-1999
Observed and modelled historical trends in the water‐use efficiency of plants and ecosystems
Publisher: Wiley
Date: 06-05-2019
DOI: 10.1111/GCB.14634
Abstract: Plant water-use efficiency (WUE, the carbon gained through photosynthesis per unit of water lost through transpiration) is a tracer of the plant physiological controls on the exchange of water and carbon dioxide between terrestrial ecosystems and the atmosphere. At the leaf level, rising CO
Optimal stomatal behaviour under stochastic rainfall
Publisher: Elsevier BV
Date: 04-2016
DOI: 10.1016/J.JTBI.2016.01.003
Abstract: Vegetation CO2 uptake is always accompanied by water loss. The balance in this gas exchange is controlled by the stomata, through which CO2 and water vapour diffuse between the leaf and the atmosphere. The optimal stomatal behaviour theory proposes that vegetation should optimise its stomatal behaviour such that, for given water availability, photosynthesis is maximised. In this paper, we optimise stomatal conductance as a function of soil water content for the maximum expected value of photosynthesis rate. This optimisation process is considered under stochastic rainfall. The optimal solution is largely shaped by two constraints: the risks of soil water exhaustion and surface runoff, which results in an inverse S-shaped curve of stomatal conductance along the soil water gradient. We derive the optimal functional relationship between stomatal conductance and soil water content under varying rainfall frequency, mean annual precipitation and atmospheric CO2 concentration. Comparisons with large-scale observational data show that the model is able to broadly capture responses of photosynthesis, transpiration, and water use efficiency along rainfall gradients, although notable discrepancies suggest additional factors are important in shaping these responses. Our work provides a theoretical framework for analysing the vegetation gas exchange under environmental change.
Intolerance of uncertainty and negative metacognitive beliefs as transdiagnostic mediators of repetitive negative thinking in a clinical sample with anxiety disorders
Publisher: Elsevier BV
Date: 03-2013
Biochemical photosynthetic responses to temperature: How do interspecific differences compare with seasonal shifts?
Publisher: Oxford University Press (OUP)
Date: 09-07-2013
Abstract: Plants show flexible acclimation of leaf photosynthesis to temperature that depends both on their prevailing growth environment and the climate where they originated. This acclimation has been shown to involve changes in the temperature responses of the apparent maximum rate of Rubisco carboxylation (Vcmax) and apparent maximum rate of electron transport (Jmax), as well as changes in the ratio of these parameters. We asked whether such changes in photosynthetic biochemistry attributable to climate of origin are similar in nature and magnitude to those attributable to growth environment. To address this question, we measured temperature responses of photosynthesis and chlorophyll fluorescence on six Eucalyptus species from erse geographical and climatic regions growing in a common garden. Measurements were made in three seasons, allowing us to compare interspecific differences with seasonal changes. We found significant interspecific differences in apparent Vcmax and Jmax standardized to 25 °C, but there were no significant differences in the temperature responses of these parameters among species. Comparing data across seasons, we found significant seasonal changes in apparent Vcmax25, but not in Jmax25, causing a change in their ratio (J/V ratio). However, there were no seasonal changes in the temperature response of either parameter. We concluded that the growth environment had a much larger effect on temperature response than climate of origin among this set of species. Mean daytime temperature increased by 15 °C from winter to summer, whereas we estimated that the seasonal change in J/V ratio would cause a change in the optimum temperature (Topt) for gross photosynthesis of 3.6 °C. Use of a general relationship to describe photosynthetic temperature acclimation resulted in a strong underestimation of the Topt for photosynthesis for these species. Our results indicated that variation in photosynthetic temperature responses cannot be captured in one simple relationship with growth temperature. Further comparative research on species groups will be needed to develop a basis for modelling these interspecific differences in plant temperature acclimation.
Learning to rerank images with enhanced spatial verification
Publisher: IEEE
Date: 09-2012
R-SVM+: Robust Learning with Privileged Information
Publisher: International Joint Conferences on Artificial Intelligence Organization
Date: 07-2018
Abstract: In practice, the circumstance that training and test data are clean is not always satisfied. The performance of existing methods in the learning using privileged information (LUPI) paradigm may be seriously challenged, due to the lack of clear strategies to address potential noises in the data. This paper proposes a novel Robust SVM+ (RSVM+) algorithm based on a rigorous theoretical analysis. Under the SVM+ framework in the LUPI paradigm, we study the lower bound of perturbations of both ex le feature data and privileged feature data, which will mislead the model to make wrong decisions. By maximizing the lower bound, tolerance of the learned model over perturbations will be increased. Accordingly, a novel regularization function is introduced to upgrade a variant form of SVM+. The objective function of RSVM+ is transformed into a quadratic programming problem, which can be efficiently optimized using off-the-shelf solvers. Experiments on real-world datasets demonstrate the necessity of studying robust SVM+ and the effectiveness of the proposed algorithm.
Relationship between homework completion and outcome in cognitive behaviour therapy
Publisher: Informa UK Limited
Date: 12-2005
ROMIR: Robust Multi-View Image Re-Ranking
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2019
A common thermal niche among geographically diverse populations of the widely distributed tree species Eucalyptus tereticornis: No evidence for adaptation to climate-of-origin
Publisher: Wiley
Date: 08-07-2017
DOI: 10.1111/GCB.13771
Abstract: Impacts of climate warming depend on the degree to which plants are constrained by adaptation to their climate-of-origin or exhibit broad climatic suitability. We grew cool-origin, central and warm-origin provenances of Eucalyptus tereticornis in an array of common temperature environments from 18 to 35.5°C to determine if this widely distributed tree species consists of geographically contrasting provenances with differentiated and narrow thermal niches, or if provenances share a common thermal niche. The temperature responses of photosynthesis, respiration, and growth were equivalent across the three provenances, reflecting a common thermal niche despite a 2,200 km geographic distance and 13°C difference in mean annual temperature at seed origin. The temperature dependence of growth was primarily mediated by changes in leaf area per unit plant mass, photosynthesis, and whole-plant respiration. Thermal acclimation of leaf, stem, and root respiration moderated the increase in respiration with temperature, but acclimation was constrained at high temperatures. We conclude that this species consists of provenances that are not differentiated in their thermal responses, thus rejecting our hypothesis of adaptation to climate-of-origin and suggesting a shared thermal niche. In addition, growth declines with warming above the temperature optima were driven by reductions in whole-plant leaf area and increased respiratory carbon losses. The impacts of climate warming will nonetheless vary across the geographic range of this and other such species, depending primarily on each provenance's climate position on the temperature response curves for photosynthesis, respiration, and growth.
Low phosphorus supply constrains plant responses to elevated CO2: A meta‐analysis
Publisher: Wiley
Date: 31-07-2020
DOI: 10.1111/GCB.15277
Depression and anxiety in palliative care inpatients compared with those receiving palliative care at home
Publisher: Cambridge University Press (CUP)
Date: 22-11-2011
DOI: 10.1017/S1478951511000411
Abstract: This study compared the prevalence of anxiety and depression as measured on the Hospital Anxiety and Depression Scale (HADS) in palliative care patients being treated at home with those being treated as inpatients. The participants were palliative care patients being treated at home ( n = 46) and palliative care inpatients ( n = 46). Subjects were assessed for functionality on the Karnofsky Performance Status Scale (KPS) and anxiety and depression were measured on the HADS. The results showed that ~20% of all patients were depressed and anxious as measured on the HADS, regardless of the cutoff criteria. There was no significant difference in depression and anxiety between the two groups when socioeconomic status and functionality were controlled for. Functionality, as measured on the KPS, was uniquely a predictor of depression, and younger patients were shown to have greater anxiety. The results suggest that home-based palliative care patients and palliative care inpatients should receive equal psychological support, and that clinicians need to be aware of the psychological vulnerability of younger and less-functional patients. The prevalence of depression and anxiety indicates that all palliative care patients should be screened for psychological distress, to identify those who need further assessment and treatment.
Towards physiologically meaningful water-use efficiency estimates from eddy covariance data
Publisher: Wiley
Date: 11-10-2018
DOI: 10.1111/GCB.13893
Abstract: Intrinsic water-use efficiency (iWUE) characterizes the physiological control on the simultaneous exchange of water and carbon dioxide in terrestrial ecosystems. Knowledge of iWUE is commonly gained from leaf-level gas exchange measurements, which are inevitably restricted in their spatial and temporal coverage. Flux measurements based on the eddy covariance (EC) technique can overcome these limitations, as they provide continuous and long-term records of carbon and water fluxes at the ecosystem scale. However, vegetation gas exchange parameters derived from EC data are subject to scale-dependent and method-specific uncertainties that compromise their ecophysiological interpretation as well as their comparability among ecosystems and across spatial scales. Here, we use estimates of canopy conductance and gross primary productivity (GPP) derived from EC data to calculate a measure of iWUE (G
Pastures and Climate Extremes: Impacts of cool season warming and drought on the productivity of key pasture species in a field experiment
Publisher: Cold Spring Harbor Laboratory
Date: 22-12-2020
DOI: 10.1101/2020.12.21.423155
Abstract: Shifts in the timing, intensity and/or frequency of climate extremes, such as severe drought and heatwaves, can generate sustained shifts in ecosystem function with important ecological and economic impacts for rangelands and managed pastures. The Pastures and Climate Extremes experiment (PACE) in Southeast Australia was designed to investigate the impacts of a severe winter/spring drought (60% rainfall reduction) and, for a subset of species, a factorial combination of drought and elevated temperature (ambient +3 °C) on pasture productivity. The experiment included nine common pasture and Australian rangeland species from three plant functional groups (C 3 grasses, C 4 grasses and legumes) planted in monoculture. Winter/spring drought resulted in productivity declines of 45% on average and up to 74% for the most affected species ( Digitaria eriantha ) during the 6-month treatment period, with eight of the nine species exhibiting significant yield reductions. Despite considerable variation in species’ sensitivity to drought, C 4 grasses were more strongly affected by this treatment than C 3 grasses or legumes. Warming also had negative effects on cool-season productivity, associated at least partially with exceedance of optimum growth temperatures in spring and indirect effects on soil water content. The combination of winter/spring drought and year-round warming resulted in the greatest yield reductions. We identified responses that were either additive such that there was only as significant warming effect under drought ( Festuca ), or less-than-additive, where there was no drought effect under warming ( Medicago ), compared to ambient plots. Results from this study highlight the sensitivity of erse pasture species to increases in winter and spring drought severity similar to those predicted for this region, and that anticipated benefits of cool-season warming are unlikely to be realised. Overall, the substantial negative impacts on productivity suggest that future, warmer, drier climates will result in shortfalls in cool-season forage availability, with profound implications for the livestock industry and natural grazer communities.
Elevated CO2 does not increase eucalypt forest productivity on a low-phosphorus soil
Publisher: Springer Science and Business Media LLC
Date: 06-03-2017
DOI: 10.1038/NCLIMATE3235
Adaptive plasticity in plant traits increases time to hydraulic failure under drought in a foundation tree
Publisher: Oxford University Press (OUP)
Date: 26-07-2021
Abstract: The viability of forest trees, in response to climate change-associated drought, will depend on their capacity to survive through genetic adaptation and phenotypic plasticity in drought tolerance traits. Genotypes with enhanced plasticity for drought tolerance (adaptive plasticity) will have a greater ability to persist and delay the onset of hydraulic failure. By examining populations from different climate-origins grown under contrasting soil water availability, we tested for genotype (G), environment (E) and genotype-by-environment (G × E) effects on traits that determine the time it takes for saplings to desiccate from stomatal closure to 88% loss of stem hydraulic conductance (time to hydraulic failure, THF). Specifically, we hypothesized that: (i) THF is dependent on a G × E interaction, with longer THF for warm, dry climate populations in response to chronic water deficit treatment compared with cool, wet populations, and (ii) hydraulic and allometric traits explain the observed patterns in THF. Corymbia calophylla saplings from two populations originating from contrasting climates (warm-dry or cool-wet) were grown under well-watered and chronic soil water deficit treatments in large containers. Hydraulic and allometric traits were measured and then saplings were dried-down to critical levels of drought stress to estimate THF. Significant plasticity was detected in the warm-dry population in response to water-deficit, with enhanced drought tolerance compared with the cool-wet population. Projected leaf area and total plant water storage showed treatment variation, and minimum conductance showed significant population differences driving longer THF in trees from warm-dry origins grown in water-limited conditions. Our findings contribute information on intraspecific variation in key drought traits, including hydraulic and allometric determinants of THF. It highlights the need to quantify adaptive capacity in populations of forest trees in climate change-type drought to improve predictions of forest die-back.
Water‐use efficiency in a semi‐arid woodland with high rainfall variability
Publisher: Wiley
Date: 02-11-2020
DOI: 10.1111/GCB.14866
Abstract: As the ratio of carbon uptake to water use by vegetation, water‐use efficiency (WUE) is a key ecosystem property linking global carbon and water cycles. It can be estimated in several ways, but it is currently unclear how different measures of WUE relate, and how well they each capture variation in WUE with soil moisture availability. We evaluated WUE in an Acacia ‐dominated woodland ecosystem of central Australia at various spatial and temporal scales using stable carbon isotope analysis, leaf gas exchange and eddy covariance (EC) fluxes. Semi‐arid Australia has a highly variable rainfall pattern, making it an ideal system to study how WUE varies with water availability. We normalized our measures of WUE across a range of vapour pressure deficits using g 1 , which is a parameter derived from an optimal stomatal conductance model and which is inversely related to WUE. Continuous measures of whole‐ecosystem g 1 obtained from EC data were elevated in the 3 days following rain, indicating a strong effect of soil evaporation. Once these values were removed, a close relationship of g 1 with soil moisture content was observed. Leaf‐scale values of g 1 derived from gas exchange were in close agreement with ecosystem‐scale values. In contrast, values of g 1 obtained from stable isotopes did not vary with soil moisture availability, potentially indicating remobilization of stored carbon during dry periods. Our comprehensive comparison of alternative measures of WUE shows the importance of stomatal control of fluxes in this highly variable rainfall climate and demonstrates the ability of these different measures to quantify this effect. Our study provides the empirical evidence required to better predict the dynamic carbon–water relations in semi‐arid Australian ecosystems.
A test of an optimal stomatal conductance scheme within the CABLE land surface model
Publisher: Copernicus GmbH
Date: 24-02-2015
Abstract: Abstract. Stomatal conductance (gs) affects the fluxes of carbon, energy and water between the vegetated land surface and the atmosphere. We test an implementation of an optimal stomatal conductance model within the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model (LSM). In common with many LSMs, CABLE does not differentiate between gs model parameters in relation to plant functional type (PFT), but instead only in relation to photosynthetic pathway. We constrained the key model parameter "g1", which represents plant water use strategy, by PFT, based on a global synthesis of stomatal behaviour. As proof of concept, we also demonstrate that the g1 parameter can be estimated using two long-term average (1960–1990) bioclimatic variables: (i) temperature and (ii) an indirect estimate of annual plant water availability. The new stomatal model, in conjunction with PFT parameterisations, resulted in a large reduction in annual fluxes of transpiration (~ 30% compared to the standard CABLE simulations) across evergreen needleleaf, tundra and C4 grass regions. Differences in other regions of the globe were typically small. Model performance against upscaled data products was not degraded, but did not noticeably reduce existing model–data biases. We identified assumptions relating to the coupling of the vegetation to the atmosphere and the parameterisation of the minimum stomatal conductance as areas requiring further investigation in both CABLE and potentially other LSMs. We conclude that optimisation theory can yield a simple and tractable approach to predicting stomatal conductance in LSMs.
On the minimum leaf conductance: its role in models of plant water use, and ecological and environmental controls
Publisher: Wiley
Date: 25-08-2019
DOI: 10.1111/NPH.15395
Abstract: Contents Summary 693 I. Introduction 693 II. Comparison of various definitions and measurement techniques of minimum conductance 694 III. Cuticular conductance 695 IV. Contribution of stomata 696 V. Environmental and ecological variation in minimum conductance 696 VI. Use of minimum conductance in models 698 VII. Conclusions 703 Acknowledgements 703 References 703 SUMMARY: When the rate of photosynthesis is greatly diminished, such as during severe drought, extreme temperature or low light, it seems advantageous for plants to close stomata and completely halt water loss. However, water loss continues through the cuticle and incompletely closed stomata, together constituting the leaf minimum conductance (g
On the importance of including soil nutrient feedback effects for predicting ecosystem carbon exchange
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/FP02152
Abstract: To grow, plants need both carbon, which is fixed in photosynthesis, and inorganic nutrients, which are generally obtained from the soil. Much interest currently exists in trying to understand the uptake and storage of carbon by terrestrial ecosystems. This paper investigates to what extent carbon gain and storage are modified by soil nutrient availability. This issue is investigated in relation to both short-term carbon fluxes on the time scale of interannual variability and long-term ecosystem carbon stocks on time scales of several thousand years.We conclude from simulations with an ecosystem model (CenW) that interannual variations in carbon gain can be significantly affected by feedback effects through the nutrient cycle. This feedback effect operates principally through an imbalance between carbon and nutrient dynamics. In years that allow high carbon gain, nutrient supply typically does not match the increased carbon supply so that foliar nutrient concentrations are reduced. This lowers productivity below that which could be expected if foliar nutrient concentration remained the same. The importance of these feedback effects is shown to be greatest at intermediate levels of water availability and nutrient supply, and is relatively more important for net ecosystem carbon exchange than for net primary production.We conclude that the long-term build-up of carbon stocks in ecosystems is often controlled by the rate at which nutrients can be gained. This conclusion is based on data from published studies showing that the slow build-up of carbon matches the gain in nitrogen, phosphorus and sulfur, and on our simulations of system carbon stocks in response to fertiliser addition.The paper concludes with a discussion of the importance and feasibility of including these processes into models at different scales, including the broad continental scale. For modelling net ecosystem exchange for Australia, it is regarded as feasible and desirable to use models that are constrained by these system-internal feedback effects. Such models have already been used for large-scale simulations in Australia and other countries.
Anxiety as a mediator between perfectionism and eating disorders
Publisher: Springer Science and Business Media LLC
Date: 12-01-2013
Decoupling between stomatal conductance and photosynthesis occurs under extreme heat in broadleaf tree species regardless of water access
Publisher: Wiley
Date: 12-09-2023
DOI: 10.1111/GCB.16929
How do leaf and ecosystem measures of water-use efficiency compare?
Publisher: Wiley
Date: 02-06-2017
DOI: 10.1111/NPH.14626
Abstract: The terrestrial carbon and water cycles are intimately linked: the carbon cycle is driven by photosynthesis, while the water balance is dominated by transpiration, and both fluxes are controlled by plant stomatal conductance. The ratio between these fluxes, the plant water-use efficiency (WUE), is a useful indicator of vegetation function. WUE can be estimated using several techniques, including leaf gas exchange, stable isotope discrimination, and eddy covariance. Here we compare global compilations of data for each of these three techniques. We show that patterns of variation in WUE across plant functional types (PFTs) are not consistent among the three datasets. Key discrepancies include the following: leaf-scale data indicate differences between needleleaf and broadleaf forests, but ecosystem-scale data do not leaf-scale data indicate differences between C
Monitoring global tree mortality patterns and trends. Report from the VW symposium ‘Crossing scales and disciplines to identify global trends of tree mortality as indicators of forest healt
Publisher: Wiley
Date: 15-01-2018
DOI: 10.1111/NPH.14988
Interpersonal problems across anxiety, depression, and eating disorders: A transdiagnostic examination
Publisher: Wiley
Date: 19-10-2013
DOI: 10.1111/BJC.12005
Predicting long‐term carbon sequestration in response to CO2 enrichment: How and why do current ecosystem models differ?
Publisher: American Geophysical Union (AGU)
Date: 04-2015
DOI: 10.1002/2014GB004995
A mechanistic analysis of light and carbon use efficiencies
Publisher: Wiley
Date: 06-1998
Issues in Modelling Plant Ecosystem Responses to Elevated CO2: Interactions with Soil Nitrogen
Publisher: Wiley
Date: 10-10-2007
Satellite based estimates underestimate the effect of CO2 fertilization on net primary productivity
Publisher: Springer Science and Business Media LLC
Date: 28-09-2016
DOI: 10.1038/NCLIMATE3105
Multi-Task Learning for Blind Source Separation
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 09-2018
Mechanisms linking plant productivity and water status for a temperate Eucalyptus forest flux site: Analysis over wet and dry years with a simple model
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/FP08125
Abstract: A simple process-based model was applied to a tall Eucalyptus forest site over consecutive wet and dry years to examine the importance of different mechanisms linking productivity and water availability. Measured soil moisture, gas flux (CO2, H2O) and meteorological records for the site were used. Similar levels of simulated H2O flux in ‘wet’ and ‘dry’ years were achieved when water availability was not confined to the first 1.20 m of the soil profile, but was allowed to exceed it. Although the simulated effects of low soil and atmospheric water content on CO2 flux, presumably via reduction in stomatal aperture, also acted on transpiration, they were offset in the dry year by a higher vapour-pressure deficit. A sensitivity analysis identified the processes that were important in wet versus dry years, and on an intra-annual timeframe. Light-limited productivity dominated in both years, except for the driest period in the dry year. Vapour-pressure deficit affected productivity across more of each year than soil moisture, but both effects were larger in the dry year. The introduction of a reduced leaf area tended to decrease sensitivity in the dry year. Plant hydraulic architecture that increases plant available water, maximises productivity per unit water use and achieves lower sensitivity to low soil moisture levels should minimise production losses during dry conditions.
Why is plant-growth response to elevated CO2 amplified when water is limiting, but reduced when nitrogen is limiting? A growth-optimisation hypothesis
Publisher: CSIRO Publishing
Date: 2008
DOI: 10.1071/FP08128
Abstract: Experimental evidence indicates that the stomatal conductance and nitrogen concentration ([N]) of foliage decline under CO2 enrichment, and that the percentage growth response to elevated CO2 is lified under water limitation, but reduced under nitrogen limitation. We advance simple explanations for these responses based on an optimisation hypothesis applied to a simple model of the annual carbon–nitrogen–water economy of trees growing at a CO2-enrichment experiment at Oak Ridge, Tennessee, USA. The model is shown to have an optimum for leaf [N], stomatal conductance and leaf area index (LAI), where annual plant productivity is maximised. The optimisation is represented in terms of a trade-off between LAI and stomatal conductance, constrained by water supply, and between LAI and leaf [N], constrained by N supply. At elevated CO2 the optimum shifts to reduced stomatal conductance and leaf [N] and enhanced LAI. The model is applied to years with contrasting rainfall and N uptake. The predicted growth response to elevated CO2 is greatest in a dry, high-N year and is reduced in a wet, low-N year. The underlying physiological explanation for this contrast in the effects of water versus nitrogen limitation is that leaf photosynthesis is more sensitive to CO2 concentration ([CO2]) at lower stomatal conductance and is less sensitive to [CO2] at lower leaf [N].
Bridging drought experiment and modeling: Representing the differential sensitivities of leaf gas exchange to drought
Publisher: Frontiers Media SA
Date: 15-01-2019
A model of plant isoprene emission based on available reducing power captures responses to atmospheric CO 2
Publisher: Wiley
Date: 24-03-2014
DOI: 10.1111/NPH.12770
Abstract: We present a unifying model for isoprene emission by photosynthesizing leaves based on the hypothesis that isoprene biosynthesis depends on a balance between the supply of photosynthetic reducing power and the demands of carbon fixation. We compared the predictions from our model, as well as from two other widely used models, with measurements of isoprene emission from leaves of P opulus nigra and hybrid aspen ( P opulus tremula × P . tremuloides ) in response to changes in leaf internal CO 2 concentration ( C i ) and photosynthetic photon flux density ( PPFD ) under erse ambient CO 2 concentrations ( C a ). Our model reproduces the observed changes in isoprene emissions with C i and PPFD , and also reproduces the tendency for the fraction of fixed carbon allocated to isoprene to increase with increasing PPFD . It also provides a simple mechanism for the previously unexplained decrease in the quantum efficiency of isoprene emission with increasing C a . Experimental and modelled results support our hypothesis. Our model can reproduce the key features of the observations and has the potential to improve process‐based modelling of isoprene emissions by land vegetation at the ecosystem and global scales.
Global-scale environmental control of plant photosynthetic capacity
Publisher: Wiley
Date: 12-2015
DOI: 10.1890/14-2111.1
Abstract: Photosynthetic capacity, determined by light harvesting and carboxylation reactions, is a key plant trait that determines the rate of photosynthesis however, in Earth System Models (ESMs) at a reference temperature, it is either a fixed value for a given plant functional type or derived from a linear function of leaf nitrogen content. In this study, we conducted a comprehensive analysis that considered correlations of environmental factors with photosynthetic capacity as determined by maximum carboxylation (V(cm)) rate scaled to 25 degrees C (i.e., V(c),25 μmol CO2 x m(-2)x s(-1)) and maximum electron transport rate (J(max)) scaled to 25 degrees C (i.e., J25 μmol electron x m(-2) x s(-1)) at the global scale. Our results showed that the percentage of variation in observed V(c),25 and J25 explained jointly by the environmental factors (i.e., day length, radiation, temperature, and humidity) were 2-2.5 times and 6-9 times of that explained by area-based leaf nitrogen content, respectively. Environmental factors influenced photosynthetic capacity mainly through photosynthetic nitrogen use efficiency, rather than through leaf nitrogen content. The combination of leaf nitrogen content and environmental factors was able to explain -56% and -66% of the variation in V(c),25 and J25 at the global scale, respectively. Our analyses suggest that model projections of plant photosynthetic capacity and hence land-atmosphere exchange under changing climatic conditions could be substantially improved if environmental factors are incorporated into algorithms used to parameterize photosynthetic capacity in ESMs.
Tropical rainforest species have larger increases in temperature optima with warming than warm‐temperate rainforest trees
Publisher: Wiley
Date: 28-03-2022
DOI: 10.1111/NPH.18077
Abstract: While trees can acclimate to warming, there is concern that tropical rainforest species may be less able to acclimate because they have adapted to a relatively stable thermal environment. Here we tested whether the physiological adjustments to warming differed among Australian tropical, subtropical and warm‐temperate rainforest trees. Photosynthesis and respiration temperature responses were quantified in six Australian rainforest seedlings of tropical, subtropical and warm‐temperate climates grown across four growth temperatures in a glasshouse. Temperature‐response models were fitted to identify mechanisms underpinning the response to warming. Tropical and subtropical species had higher temperature optima for photosynthesis ( T optA ) than temperate species. There was acclimation of T optA to warmer growth temperatures. The rate of acclimation (0.35–0.78°C °C –1 ) was higher in tropical and subtropical than in warm‐temperate trees and attributed to differences in underlying biochemical parameters, particularly increased temperature optima of V cmax25 and J max25 . The temperature sensitivity of respiration ( Q 10 ) was 24% lower in tropical and subtropical compared with warm‐temperate species. Overall, tropical and subtropical species had a similar capacity to acclimate to changes in growth temperature as warm‐temperate species, despite being grown at higher temperatures. Quantifying the physiological acclimation in rainforests can improve accuracy of future climate predictions and assess their potential vulnerability to warming.
To what extent can rising [CO2] ameliorate plant drought stress?
Publisher: Wiley
Date: 28-07-2021
DOI: 10.1111/NPH.17540
Abstract: Plant responses to elevated atmospheric carbon dioxide (eCO 2 ) have been hypothesized as a key mechanism that may ameliorate the impact of future drought. Yet, despite decades of experiments, the question of whether eCO 2 reduces plant water use, yielding ‘water savings’ that can be used to maintain plant function during periods of water stress, remains unresolved. In this Viewpoint, we identify the experimental challenges and limitations to our understanding of plant responses to drought under eCO 2 . In particular, we argue that future studies need to move beyond exploring whether eCO 2 played ‘a role’ or ‘no role’ in responses to drought, but instead more carefully consider the timescales and conditions that would induce an influence. We also argue that considering emergent differences in soil water content may be an insufficient means of assessing the impact of eCO 2 . We identify eCO 2 impact during severe drought (e.g. to the point of mortality), interactions with future changes in vapour pressure deficit and uncertainty about changes in leaf area as key gaps in our current understanding. New insights into CO 2 × drought interactions are essential to better constrain model theory that governs future climate model projections of land–atmosphere interactions during periods of water stress.
Implementation of an optimal stomatal conductance model in the Australian Community Climate Earth Systems Simulator (ACCESS1.3b)
Publisher: Copernicus GmbH
Date: 03-07-2015
Abstract: Abstract. We implement a new stomatal conductance model, based on the optimality approach, within the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model. Coupled land-atmosphere simulations are then performed using CABLE within the Australian Community Climate and Earth Systems Simulator (ACCESS) with prescribed sea surface temperatures. As in most land surface models, the default stomatal conductance scheme only accounts for differences in model parameters in relation to the photosynthetic pathway, but not in relation to plant functional types. The new scheme allows model parameters to vary by plant functional type, based on a global synthesis of observations of stomatal conductance under different climate regimes over a wide range of species. We show that the new scheme reduces the latent heat flux from the land surface over the boreal forests during the Northern Hemisphere summer by 0.5 to 1.0 mm day-1. This leads to warmer daily maximum and minimum temperatures by up to 1.0 °C and warmer extreme maximum temperatures by up to 1.5 °C. These changes generally improve the climate model's climatology and improve existing biases by 10–20 %. The change in the surface energy balance also affects net primary productivity and the terrestrial carbon balance. We conclude that the improvements in the global climate model which result from the new stomatal scheme, constrained by a global synthesis of experimental data, provide a valuable advance in the long-term development of the ACCESS modelling system.
Multi-view manifold learning with locality alignment
Publisher: Elsevier BV
Date: 06-2018
Forest resilience and tipping points at different spatio‐temporal scales: approaches and challenges
Publisher: Wiley
Date: 2015
Large but decreasing effect of ozone on the European carbon sink
Publisher: Copernicus GmbH
Date: 13-07-2018
Abstract: Abstract. The capacity of the terrestrial biosphere to sequester carbon and mitigate climate change is governed by the ability of vegetation to remove emissions of CO2 through photosynthesis. Tropospheric O3, a globally abundant and potent greenhouse gas, is, however, known to damage plants, causing reductions in primary productivity. Despite emission control policies across Europe, background concentrations of tropospheric O3 have risen significantly over the last decades due to hemispheric-scale increases in O3 and its precursors. Therefore, plants are exposed to increasing background concentrations, at levels currently causing chronic damage. Studying the impact of O3 on European vegetation at the regional scale is important for gaining greater understanding of the impact of O3 on the land carbon sink at large spatial scales. In this work we take a regional approach and update the JULES land surface model using new measurements specifically for European vegetation. Given the importance of stomatal conductance in determining the flux of O3 into plants, we implement an alternative stomatal closure parameterisation and account for diurnal variations in O3 concentration in our simulations. We conduct our analysis specifically for the European region to quantify the impact of the interactive effects of tropospheric O3 and CO2 on gross primary productivity (GPP) and land carbon storage across Europe. A factorial set of model experiments showed that tropospheric O3 can suppress terrestrial carbon uptake across Europe over the period 1901 to 2050. By 2050, simulated GPP was reduced by 4 to 9 % due to plant O3 damage and land carbon storage was reduced by 3 to 7 %. The combined physiological effects of elevated future CO2 (acting to reduce stomatal opening) and reductions in O3 concentrations resulted in reduced O3 damage in the future. This alleviation of O3 damage by CO2-induced stomatal closure was around 1 to 2 % for both land carbon and GPP, depending on plant sensitivity to O3. Reduced land carbon storage resulted from diminished soil carbon stocks consistent with the reduction in GPP. Regional variations are identified with larger impacts shown for temperate Europe (GPP reduced by 10 to 20 %) compared to boreal regions (GPP reduced by 2 to 8 %). These results highlight that O3 damage needs to be considered when predicting GPP and land carbon, and that the effects of O3 on plant physiology need to be considered in regional land carbon cycle assessments.
Conserved stomatal behaviour under elevated CO2 and varying water availability in a mature woodland
Publisher: Wiley
Date: 27-08-2016
Impact of the representation of stomatal conductance on model projections of heatwave intensity
Publisher: Springer Science and Business Media LLC
Date: 21-03-2016
DOI: 10.1038/SREP23418
Abstract: Stomatal conductance links plant water use and carbon uptake and is a critical process for the land surface component of climate models. However, stomatal conductance schemes commonly assume that all vegetation with the same photosynthetic pathway use identical plant water use strategies whereas observations indicate otherwise. Here, we implement a new stomatal scheme derived from optimal stomatal theory and constrained by a recent global synthesis of stomatal conductance measurements from 314 species, across 56 field sites. Using this new stomatal scheme, within a global climate model, subtantially increases the intensity of future heatwaves across Northern Eurasia. This indicates that our climate model has previously been under-predicting heatwave intensity. Our results have widespread implications for other climate models, many of which do not account for differences in stomatal water-use across different plant functional types and hence, are also likely under projecting heatwave intensity in the future.
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.
New insights into the covariation of stomatal, mesophyll and hydraulic conductances from optimization models incorporating nonstomatal limitations to photosynthesis
Publisher: Wiley
Date: 31-10-2018
DOI: 10.1111/NPH.14848
Abstract: Optimization models of stomatal conductance (g
Using plant, microbe, and soil fauna traits to improve the predictive power of biogeochemical models
Publisher: Wiley
Date: 08-10-2018
Multi-View Intact Space Learning
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2015
How should we model plant responses to drought? An analysis of stomatal and non-stomatal responses to water stress
Publisher: Elsevier BV
Date: 12-2013
The response of ecosystem water‐use efficiency to rising atmospheric CO 2 concentrations: sensitivity and large‐scale biogeochemical implications
Publisher: Wiley
Date: 07-11-2016
DOI: 10.1111/NPH.14288
Abstract: Ecosystem water‐use efficiency ( WUE ) is an important metric linking the global land carbon and water cycles. Eddy covariance‐based estimates of WUE in temperate/boreal forests have recently been found to show a strong and unexpected increase over the 1992–2010 period, which has been attributed to the effects of rising atmospheric CO 2 concentrations on plant physiology. To test this hypothesis, we forced the observed trend in the process‐based land surface model JSBACH by increasing the sensitivity of stomatal conductance ( g s ) to atmospheric CO 2 concentration. We compared the simulated continental discharge, evapotranspiration ( ET ), and the seasonal CO 2 exchange with observations across the extratropical northern hemisphere. The increased simulated WUE led to substantial changes in surface hydrology at the continental scale, including a significant decrease in ET and a significant increase in continental runoff, both of which are inconsistent with large‐scale observations. The simulated seasonal litude of atmospheric CO 2 decreased over time, in contrast to the observed upward trend across ground‐based measurement sites. Our results provide strong indications that the recent, large‐scale WUE trend is considerably smaller than that estimated for these forest ecosystems. They emphasize the decreasing CO 2 sensitivity of WUE with increasing scale, which affects the physiological interpretation of changes in ecosystem WUE .
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
Effectiveness of Cognitive Behavior Therapy for Diagnostically Heterogeneous Groups: A Benchmarking Study
Publisher: American Psychological Association (APA)
Date: 2007
A roadmap for improving the representation of photosynthesis in Earth system models
Publisher: Wiley
Date: 28-11-2016
DOI: 10.1111/NPH.14283
Abstract: Accurate representation of photosynthesis in terrestrial biosphere models ( TBM s) is essential for robust projections of global change. However, current representations vary markedly between TBM s, contributing uncertainty to projections of global carbon fluxes. Here we compared the representation of photosynthesis in seven TBM s by examining leaf and canopy level responses of photosynthetic CO 2 assimilation ( A ) to key environmental variables: light, temperature, CO 2 concentration, vapor pressure deficit and soil water content. We identified research areas where limited process knowledge prevents inclusion of physiological phenomena in current TBM s and research areas where data are urgently needed for model parameterization or evaluation. We provide a roadmap for new science needed to improve the representation of photosynthesis in the next generation of terrestrial biosphere and Earth system models.
Temperature response of parameters of a biochemically based model of photosynthesis. I. Seasonal changes in mature maritime pine (Pinus pinaster Ait.)
Publisher: Wiley
Date: 15-08-2002
Which are the most important parameters for modelling carbon assimilation in boreal Norway spruce under elevated [CO2 ] and temperature conditions?
Publisher: Oxford University Press (OUP)
Date: 21-03-2013
Abstract: Photosynthesis is highly responsive to environmental and physiological variables, including phenology, foliage nitrogen (N) content, atmospheric CO2 concentration ([CO2]), irradiation (Q), air temperature (T) and vapour pressure deficit (D). Each of these responses is likely to be modified by long-term changes in climatic conditions such as rising air temperature and [CO2]. When modelling photosynthesis under climatic changes, which parameters are then most important to calibrate for future conditions? To assess this, we used measurements of shoot carbon assimilation rates and microclimate conditions collected at Flakaliden, northern Sweden. Twelve 40-year-old Norway spruce trees were enclosed in whole-tree chambers and exposed to elevated [CO2] and elevated air temperature, separately and in combination. The treatments imposed were elevated temperature, +2.8 °C in July/August and +5.6 °C in December above ambient, and [CO2] (ambient CO2 ∼370 μ mol mol(-1), elevated CO2 ∼700 μ mol mol(-1)). The relative importance of parameterization of Q, T and D responses for effects on the photosynthetic rate, expressed on a projected needle area, and the annual shoot carbon uptake was quantified using an empirical shoot photosynthesis model, which was developed and fitted to the measurements. The functional form of the response curves was established using an artificial neural network. The [CO2] treatment increased annual shoot carbon (C) uptake by 50%. Most important was effects on the light response curve, with a 67% increase in light-saturated photosynthetic rate, and a 52% increase in the initial slope of the light response curve. An interactive effect of light saturated photosynthetic rate was found with foliage N status, but no interactive effect for high temperature and high CO2. The air temperature treatment increased the annual shoot C uptake by 44%. The most important parameter was the seasonality, with an elongation of the growing season by almost 4 weeks. The temperature response curve was almost flat over much of the temperature range. A shift in temperature optimum had thus an insignificant effect on modelled annual shoot C uptake. The combined temperature and [CO2] treatment resulted in a 74% increase in annual shoot C uptake compared with ambient conditions, with no clear interactive effects on parameter values.
Do land surface models need to include differential plant species responses to drought? Examining model predictions across a mesic-xeric gradient in Europe
Publisher: Copernicus GmbH
Date: 21-12-2015
Abstract: Abstract. Future climate change has the potential to increase drought in many regions of the globe, making it essential that land surface models (LSMs) used in coupled climate models realistically capture the drought responses of vegetation. Recent data syntheses show that drought sensitivity varies considerably among plants from different climate zones, but state-of-the-art LSMs currently assume the same drought sensitivity for all vegetation. We tested whether variable drought sensitivities are needed to explain the observed large-scale patterns of drought impact on the carbon, water and energy fluxes. We implemented data-driven drought sensitivities in the Community Atmosphere Biosphere Land Exchange (CABLE) LSM and evaluated alternative sensitivities across a latitudinal gradient in Europe during the 2003 heatwave. The model predicted an overly abrupt onset of drought unless average soil water potential was calculated with dynamic weighting across soil layers. We found that high drought sensitivity at the most mesic sites, and low drought sensitivity at the most xeric sites, was necessary to accurately model responses during drought. Our results indicate that LSMs will over-estimate drought impacts in drier climates unless different sensitivity of vegetation to drought is taken into account.
Examining the evidence for decoupling between photosynthesis and transpiration during heat extremes
Publisher: Copernicus GmbH
Date: 26-02-2019
Abstract: Abstract. Recent experimental evidence suggests that during heat extremes, wooded ecosystems may decouple photosynthesis and transpiration, reducing photosynthesis to near zero but increasing transpiration into the boundary layer. This feedback may act to d en, rather than lify, heat extremes in wooded ecosystems. We examined eddy covariance databases (OzFlux and FLUXNET2015) to identify whether there was field-based evidence to support these experimental findings. We focused on two types of heat extremes: (i) the 3 days leading up to a temperature extreme, defined as including a daily maximum temperature ∘C (similar to the widely used TXx metric), and (ii) heatwaves, defined as 3 or more consecutive days above 35 ∘C. When focusing on (i), we found some evidence of reduced photosynthesis and sustained or increased latent heat fluxes at seven Australian evergreen wooded flux sites. However, when considering the role of vapour pressure deficit and focusing on (ii), we were unable to conclusively disentangle the decoupling between photosynthesis and latent heat flux from the effect of increasing the vapour pressure deficit. Outside of Australia, the Tier-1 FLUXNET2015 database provided limited scope to tackle this issue as it does not s le sufficient high temperature events with which to probe the physiological response of trees to extreme heat. Thus, further work is required to determine whether this photosynthetic decoupling occurs widely, ideally by matching experimental species with those found at eddy covariance tower sites. Such measurements would allow this decoupling mechanism to be probed experimentally and at the ecosystem scale. Transpiration during heatwaves remains a key issue to resolve, as no land surface model includes a decoupling mechanism, and any potential d ening of the land–atmosphere lification is thus not included in climate model projections.
Specific leaf area and vapour pressure deficit control live fuel moisture content
Publisher: Wiley
Date: 06-02-2023
Abstract: The live fuel moisture content (LFMC) is an important precondition for wildfire activity, yet it remains challenging to predict LFMC due to the dynamic interplay between atmospheric and hydrological conditions that determine the plant's access to, and loss of water. We monitored LFMC and a range of plant water‐use traits (predawn and midday leaf water potentials [Ψ leaf ]), leaf traits (specific leaf area [SLA]), hydrological status (soil water content [SWC] in the shallow layer and full profile) and atmospheric variables (air temperature, vapour pressure deficit [VPD], CO 2 concentrations) in a mature eucalypt woodland at the Eucalyptus Free‐Air CO 2 Enrichment (EucFACE) facility during a drought. We combined plant traits, hydrological status and atmospheric variables into a biophysical model to predict LFMC dynamics, and compared these with predictions of LFMC based on a satellite model and established relationships between Ψ leaf and LFMC from pressure–volume curves. Predawn Ψ leaf could be well predicted from changes in SWC, but variation in midday Ψ leaf and LFMC were more responsive to atmospheric than hydrological variables. The biophysical model explained up to 89% of variability in LFMC and outperformed established approaches to predict LFMC. SLA was the single most important variable to predict LFMC, followed by VPD, which explained 33% of the remaining variability in LFMC. Our study demonstrates that the co‐variation of plant traits and atmospheric and hydrological conditions affect LFMC during drought, suggesting a new way forward for predicting LFMC by combining biophysical and satellite‐based models of LFMC with seasonal forecasts of meteorological and hydrological variables. Read the free Plain Language Summary for this article on the Journal blog.
Efficacy of transdiagnostic treatments: A review of published outcome studies and future research directions
Publisher: Springer Publishing Company
Date: 02-2009
DOI: 10.1891/0889-8391.23.1.20
Abstract: Theory and evidence relating to biological and psychological vulnerabilities, comorbidity, latent structure, cognitive and behavioral maintaining factors, and treatment outcome suggest that commonalities across emotional disorders may outweigh the differences. Thus, researchers have recently begun evaluating transdiagnostic (or unified) treatment protocols, which target common maintaining factors, by applying them to in iduals with multiple disorders or to mixed-diagnosis groups. The aim of this article is to review the efficacy of unified protocols for anxiety and mood disorders. Evidence suggests that unified treatments are associated with symptom improvement, generally perform better than wait-list controls, are associated with improvements in comorbid disorders, and may compare well to diagnosis-specific treatments. Unified protocols are also associated with high client satisfaction, therapeutic alliance, group cohesion, and positive treatment expectations. However, these conclusions are tempered by the small number of studies and methodological limitations. We propose directions for future research.
Web-based teaching tool incorporating peer assessment and self-assessment: Example of aligned teaching
Publisher: American Roentgen Ray Society
Date: 1970
DOI: 10.2214/AJR.08.1910
Ideas and perspectives: How coupled is the vegetation to the boundary layer?
Publisher: Copernicus GmbH
Date: 09-10-2017
Abstract: Abstract. Understanding the sensitivity of transpiration to stomatal conductance is critical to simulating the water cycle. This sensitivity is a function of the degree of coupling between the vegetation and the atmosphere and is commonly expressed by the decoupling factor. The degree of coupling assumed by models varies considerably and has previously been shown to be a major cause of model disagreement when simulating changes in transpiration in response to elevated CO2. The degree of coupling also offers us insight into how different vegetation types control transpiration fluxes, which is fundamental to our understanding of land–atmosphere interactions. To explore this issue, we combined an extensive literature summary from 41 studies with estimates of the decoupling coefficient estimated from FLUXNET data. We found some notable departures from the values previously reported in single-site studies. There was large variability in estimated decoupling coefficients (range 0.05–0.51) for evergreen needleleaf forests. This is a result that was broadly supported by our literature review but contrasts with the early literature which suggests that evergreen needleleaf forests are generally well coupled. Estimates from FLUXNET indicated that evergreen broadleaved forests were the most tightly coupled, differing from our literature review and instead suggesting that it was evergreen needleleaf forests. We also found that the assumption that grasses would be strongly decoupled (due to vegetation stature) was only true for high precipitation sites. These results were robust to assumptions about aerodynamic conductance and, to a lesser extent, energy balance closure. Thus, these data form a benchmarking metric against which to test model assumptions about coupling. Our results identify a clear need to improve the quantification of the processes involved in scaling from the leaf to the whole ecosystem. Progress could be made with targeted measurement c aigns at flux sites and greater site characteristic information across the FLUXNET network.
Trees tolerate an extreme heatwave via sustained transpirational cooling and increased leaf thermal tolerance
Publisher: Wiley
Date: 02-02-2018
DOI: 10.1111/GCB.14037
Abstract: Heatwaves are likely to increase in frequency and intensity with climate change, which may impair tree function and forest C uptake. However, we have little information regarding the impact of extreme heatwaves on the physiological performance of large trees in the field. Here, we grew Eucalyptus parramattensis trees for 1 year with experimental warming (+3°C) in a field setting, until they were greater than 6 m tall. We withheld irrigation for 1 month to dry the surface soils and then implemented an extreme heatwave treatment of 4 consecutive days with air temperatures exceeding 43°C, while monitoring whole-canopy exchange of CO
Epidemiology of anxiety disorders in the Australian general population: Findings of the 2007 Australian National Survey of Mental Health and Wellbeing
Publisher: SAGE Publications
Date: 09-2079
DOI: 10.3109/00048674.2011.624083
Abstract: Objective: The aims of this study were to report 12-month and lifetime prevalence for anxiety disorders in the Australian general population, identify sociodemographic and clinical correlates of anxiety disorders, and report the rates of comorbidity among anxiety, affective, and substance use disorders across the lifespan. Method: The 2007 National Survey of Mental Health and Wellbeing was a nationally representative, face-to-face household survey of 8841 (60% response rate) community residents aged between 16 and 85 years. Diagnoses for anxiety, affective and substance use disorders were made according to the DSM-IV using the World Mental Health Survey Initiative version of the Composite International Diagnostic Interview. Results: 12-month and lifetime prevalence of anxiety disorders were 11.8% and 20.0%, respectively. Anxiety disorders had a similar median age of onset (19 years) compared to substance use disorders (20 years), but earlier than affective disorders (34 years). Social phobia was the earliest onset anxiety disorder (median 13 years), with generalized anxiety disorder the latest (median 33 years). Significant correlates of the presence of anxiety disorders included being female, single, not in the labour force, in the middle age groups, not having post-graduate qualifications, having a comorbid physical condition, and having a family history of mental disorders. Being in the oldest age ranges and being born in another non-English speaking country were associated with lower odds of having an anxiety disorder. Body mass index was not associated with the presence of an anxiety disorder. Anxiety disorders were highly comorbid, particularly with major depression, dysthymia, and alcohol dependence. Comorbidity with substance use disorders reduced with age. Comorbidity with affective disorders was high across the lifespan. Conclusions: Anxiety disorders are common, can have an early onset, and are highly comorbid. Prevention, early detection, and treatment of anxiety disorders should be a priority.
Conversion of canopy intercepted radiation to photosynthate: Review of modelling approaches for regional scales
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/FP02088
Abstract: A fundamental component of most models of terrestrial carbon balance is an estimate of plant canopy photosynthetic uptake driven by radiation interception by the canopy. In this article, we review approaches used to model the conversion of radiation into photosynthate. As this process is well understood at the leaf-scale, the modelling problem is essentially one of up-scaling, to canopy, regional or global scale. Our review therefore focuses on issues of scaling, including model identification, parameterisation and validation at large scales. Four different approaches are commonly taken to modelling photosynthate production at large scales: the maximum productivity, resource-use efficiency, big-leaf, and sun-shade models. Models representing each of these approaches are discussed and model predictions compared with estimates of gross primary productivity derived from eddy covariance data measured above a Sitka spruce forest. The sun-shade model was found to perform best at all time scales considered. However, other models had significant advantages including simplicity of implementation and the ability to combine the model with remotely-sensed information on vegetation radiation interception. We conclude that all four approaches can be successfully used to model photosynthetic uptake and that the best approach in a given situation will depend on model objectives and data availability.
Self-supervised representation learning by rotation feature decoupling
Publisher: IEEE
Date: 06-2019
Inferring the effects of sink strength on plant carbon balance processes from experimental measurements
Publisher: Copernicus GmbH
Date: 03-07-2018
Abstract: Abstract. The lack of correlation between photosynthesis and plant growth under sink-limited conditions is a long-standing puzzle in plant ecophysiology that currently severely compromises our models of vegetation responses to global change. To address this puzzle, we applied data assimilation to an experiment in which the sink strength of Eucalyptus tereticornis seedlings was manipulated by restricting root volume. Our goals were to infer which processes were affected by sink limitation and to attribute the overall reduction in growth observed in the experiment to the effects on various carbon (C) component processes. Our analysis was able to infer that, in addition to a reduction in photosynthetic rates, sink limitation reduced the rate of utilization of nonstructural carbohydrate (NSC), enhanced respiratory losses, modified C allocation and increased foliage turnover. Each of these effects was found to have a significant impact on final plant biomass accumulation. We also found that inclusion of an NSC storage pool was necessary to capture seedling growth over time, particularly for sink-limited seedlings. Our approach of applying data assimilation to infer C balance processes in a manipulative experiment enabled us to extract new information on the timing, magnitude and direction of the internal C fluxes from an existing dataset. We suggest that this approach could, if used more widely, be an invaluable tool to develop appropriate representations of sink-limited growth in terrestrial biosphere models.
Erratum: Conversion of canopy intercepted radiation to photosynthate: A review of modelling approaches for regional scales (Functional Plant Biology 30: 2 (153-169))
Publisher: CSIRO Publishing
Date: 2003
DOI: 10.1071/FP02088_CO
Abstract: A fundamental component of most models of terrestrial carbon balance is an estimate of plant canopy photosynthetic uptake driven by radiation interception by the canopy. In this article, we review approaches used to model the conversion of radiation into photosynthate. As this process is well understood at the leaf-scale, the modelling problem is essentially one of up-scaling, to canopy, regional or global scale. Our review therefore focuses on issues of scaling, including model identification, parameterisation and validation at large scales. Four different approaches are commonly taken to modelling photosynthate production at large scales: the maximum productivity, resource-use efficiency, big-leaf, and sun-shade models. Models representing each of these approaches are discussed and model predictions compared with estimates of gross primary productivity derived from eddy covariance data measured above a Sitka spruce forest. The sun-shade model was found to perform best at all time scales considered. However, other models had significant advantages including simplicity of implementation and the ability to combine the model with remotely-sensed information on vegetation radiation interception. We conclude that all four approaches can be successfully used to model photosynthetic uptake and that the best approach in a given situation will depend on model objectives and data availability.
The effect of nitrogen deposition on forest carbon sequestration: A model-based analysis
Publisher: Wiley
Date: 14-04-2010
Drought and resprouting plants
Publisher: Wiley
Date: 17-12-2014
DOI: 10.1111/NPH.13205
Abstract: Many species have the ability to resprout vegetatively after a substantial loss of biomass induced by environmental stress, including drought. Many of the regions characterised by ecosystems where resprouting is common are projected to experience more frequent and intense drought during the 21st Century. However, in assessments of ecosystem response to drought disturbance there has been scant consideration of the resilience and post‐drought recovery of resprouting species. Systematic differences in hydraulic and allocation traits suggest that resprouting species are more resilient to drought‐stress than nonresprouting species. Evidence suggests that ecosystems dominated by resprouters recover from disturbance more quickly than ecosystems dominated by nonresprouters. The ability of resprouters to avoid mortality and withstand drought, coupled with their ability to recover rapidly, suggests that the impact of increased drought stress in ecosystems dominated by these species may be small. The strategy of resprouting needs to be modelled explicitly to improve estimates of future climate‐change impacts on the carbon cycle, but this will require several important knowledge gaps to be filled before resprouting can be properly implemented.
Triggers of tree mortality under drought
Publisher: Springer Science and Business Media LLC
Date: 06-2018
DOI: 10.1038/S41586-018-0240-X
Abstract: Severe droughts have caused widespread tree mortality across many forest biomes with profound effects on the function of ecosystems and carbon balance. Climate change is expected to intensify regional-scale droughts, focusing attention on the physiological basis of drought-induced tree mortality. Recent work has shown that catastrophic failure of the plant hydraulic system is a principal mechanism involved in extensive crown death and tree mortality during drought, but the multi-dimensional response of trees to desiccation is complex. Here we focus on the current understanding of tree hydraulic performance under drought, the identification of physiological thresholds that precipitate mortality and the mechanisms of recovery after drought. Building on this, we discuss the potential application of hydraulic thresholds to process-based models that predict mortality.
Effects of elevated [CO2 ] on forest growth and carbon storage: A modelling analysis of the consequences of changes in litter quality/quantity and root exudation
Publisher: Springer Science and Business Media LLC
Date: 2000
DCT Regularized Extreme Visual Recovery
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2017
Increasing aridity will not offset CO2 fertilization in fast‐growing eucalypts with access to deep soil water
Publisher: Wiley
Date: 25-03-2021
DOI: 10.1111/GCB.15590
No evidence for triose phosphate limitation of light‐saturated leaf photosynthesis under current atmospheric CO2 concentration
Publisher: Wiley
Date: 22-08-2019
DOI: 10.1111/PCE.13639
Abstract: The triose phosphate utilization (TPU) rate has been identified as one of the processes that can limit terrestrial plant photosynthesis. However, we lack a robust quantitative assessment of TPU limitation of photosynthesis at the global scale. As a result, TPU, and its potential limitation of photosynthesis, is poorly represented in terrestrial biosphere models (TBMs). In this study, we utilized a global data set of photosynthetic CO
Comment on Drought-induced reduction in global terrestrial net primary production from 2000 through 2009
Publisher: American Association for the Advancement of Science (AAAS)
Date: 26-08-2011
Abstract: Zhao and Running (Reports, 20 August 2010, p. 940) reported that global net primary production has declined over the past decade and that this reduction was caused by drought. However, their findings are not direct measurements, but rather are based on outcomes from models in which a strong temperature dependence is assumed. I examine the assumptions underlying their results and show that their findings can be explained as logical consequences of these assumptions.
Psychometric properties of multigroup ethnic identity measure (MEIM) scores with Australian adolescents from diverse ethnocultural groups
Publisher: Wiley
Date: 23-07-2008
DOI: 10.1016/J.ADOLESCENCE.2007.06.003
Abstract: The present study investigated the reliability and factor structure of scores on a 12‐item version of Phinney's multigroup ethnic identity measure with an Australian s le from erse cultural backgrounds. Participants were 485 students aged between 10 and 15 years. The results generally supported the reliability of the ethnic identity scale scores and suggested a two‐factor structure of ethnic identity consisting of Affirmation/Belonging, and Exploration. Results concerning the other group orientation scale were mixed. Scores for this scale showed lower internal reliability and its inclusion in confirmatory factor analysis models with the ethnic identity scale showed only mediocre fit. Recommendations for future research include further investigations of the factor structure within ethnic identity as derived from social identity and developmental perspectives.
Changes in post-event processing and metacognitions during cognitive behavioral group therapy for social phobia
Publisher: Elsevier BV
Date: 06-2009
Intolerance of Uncertainty as a Contributor to Fear and Avoidance Symptoms of Panic Attacks
Publisher: Informa UK Limited
Date: 12-2013
Desiccation time during drought is highly predictable across species of Eucalyptus from contrasting climates
Publisher: Wiley
Date: 08-08-2019
DOI: 10.1111/NPH.16042
Abstract: Catastrophic failure of the water transport pathway in trees is a principal mechanism of mortality during extreme drought. To be able to predict the probability of mortality at an in idual and landscape scale we need knowledge of the time for plants to reach critical levels of hydraulic failure. We grew plants of eight species of Eucalyptus originating from contrasting climates before allowing a subset to dehydrate. We tested whether a trait-based model of time to plant desiccation t
A comparative analysis of simulated and observed photosynthetic CO 2 uptake in two coniferous forest canopies
Publisher: Oxford University Press (OUP)
Date: 07-2006
DOI: 10.1093/TREEPHYS/26.7.845
Abstract: Gross canopy photosynthesis (P(g)) can be simulated with canopy models or retrieved from turbulent carbon dioxide (CO2) flux measurements above the forest canopy. We compare the two estimates and illustrate our findings with two case studies. We used the three-dimensional canopy model MAESTRA to simulate P(g) of two spruce forests differing in age and structure. Model parameter acquisition and model sensitivity to selected model parameters are described, and modeled results are compared with independent flux estimates. Despite higher photon fluxes at the site, an older German Norway spruce (Picea abies L. (Karst.)) canopy took up 25% less CO2 from the atmosphere than a young Scottish Sitka spruce (Picea sitchensis (Bong.) Carr.) plantation. The average magnitudes of P(g) and the differences between the two canopies were satisfactorily represented by the model. The main reasons for the different uptake rates were a slightly smaller quantum yield and lower absorptance of the Norway spruce stand because of a more clumped canopy structure. The model did not represent the scatter in the turbulent CO2 flux densities, which was of the same order of magnitude as the non-photosynthetically-active-radiation-induced biophysical variability in the simulated P(g). Analysis of residuals identified only small systematic differences between the modeled flux estimates and turbulent flux measurements at high vapor pressure saturation deficits. The merits and limitations of comparative analysis for quality evaluation of both methods are discussed. From this analysis, we recommend use of both parameter sets and model structure as a basis for future applications and model development.
The peaked response of transpiration rate to vapour pressure deficit in field conditions can be explained by the temperature optimum of photosynthesis
Publisher: Elsevier BV
Date: 06-2014
Challenging terrestrial biosphere models with data from the long‐term multifactor Prairie Heating and CO 2 Enrichment experiment
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
New developments in the effort to model ecosystems under water stress
Publisher: Wiley
Date: 25-08-2016
DOI: 10.1111/NPH.14082
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.
Large-margin multi-view Gaussian process for image classification
Publisher: ACM
Date: 17-08-2013
The temperature optima for tree seedling photosynthesis and growth depend on water inputs
Publisher: Wiley
Date: 07-02-2020
DOI: 10.1111/GCB.14975
Abstract: Understanding how tree growth is affected by rising temperature is a key to predicting the fate of forests in future warmer climates. Increasing temperature has direct effects on plant physiology, but there are also indirect effects of increased water limitation because evaporative demand increases with temperature in many systems. In this study, we experimentally resolved the direct and indirect effects of temperature on the response of growth and photosynthesis of the widely distributed species Eucalyptus tereticornis. We grew E. tereticornis in an array of six growth temperatures from 18 to 35.5°C, spanning the climatic distribution of the species, with two watering treatments: (a) water inputs increasing with temperature to match plant demand at all temperatures (W
Photosynthesis of temperate Eucalyptus globulus trees outside their native range has limited adjustment to elevated CO2 and climate warming
Publisher: Wiley
Date: 11-10-2013
DOI: 10.1111/GCB.12314
Abstract: Eucalyptus species are grown widely outside of their native ranges in plantations on all vegetated continents of the world. We predicted that such a plantation species would show high potential for acclimation of photosynthetic traits across a wide range of growth conditions, including elevated [CO2] and climate warming. To test this prediction, we planted temperate Eucalyptus globulus Labill. seedlings in climate-controlled chambers in the field located >700 km closer to the equator than the nearest natural occurrence of this species. Trees were grown in a complete factorial combination of elevated CO2 concentration (eC ambient [CO2] +240 ppm) and air warming treatments (eT ambient +3 °C) for 15 months until they reached ca. 10 m height. There was little acclimation of photosynthetic capacity to eC and hence the CO2-induced photosynthetic enhancement was large (ca. 50%) in this treatment during summer. The warming treatment significantly increased rates of both carboxylation capacity (V(cmax)) and electron transport (Jmax) (measured at a common temperature of 25 °C) during winter, but decreased them significantly by 20-30% in summer. The photosynthetic CO2 compensation point in the absence of dark respiration (Γ*) was relatively less sensitive to temperature in this temperate eucalypt species than for warm-season tobacco. The temperature optima for photosynthesis and Jmax significantly changed by about 6 °C between winter and summer, but without further adjustment from early to late summer. These results suggest that there is an upper limit for the photosynthetic capacity of E. globulus ssp. globulus outside its native range to acclimate to growth temperatures above 25 °C. Limitations to temperature acclimation of photosynthesis in summer may be one factor that defines climate zones where E. globulus plantation productivity can be sustained under anticipated global environmental change.
Plant profit maximization improves predictions of European forest responses to drought
Publisher: Wiley
Date: 27-01-2020
DOI: 10.1111/NPH.16376
Abstract: Knowledge of how water stress impacts the carbon and water cycles is a key uncertainty in terrestrial biosphere models. We tested a new profit maximization model, where photosynthetic uptake of CO
Upside-down fluxes Down Under: CO 2 net sink in winter and net source in summer in a temperate evergreen broadleaf forest
Publisher: Copernicus GmbH
Date: 19-06-2018
Abstract: Abstract. Predicting the seasonal dynamics of ecosystem carbon fluxes is challenging in broadleaved evergreen forests because of their moderate climates and subtle changes in canopy phenology. We assessed the climatic and biotic drivers of the seasonality of net ecosystem–atmosphere CO2 exchange (NEE) of a eucalyptus-dominated forest near Sydney, Australia, using the eddy covariance method. The climate is characterised by a mean annual precipitation of 800 mm and a mean annual temperature of 18 ∘C, hot summers and mild winters, with highly variable precipitation. In the 4-year study, the ecosystem was a sink each year (−225 g C m−2 yr−1 on average, with a standard deviation of 108 g C m−2 yr−1) inter-annual variations were not related to meteorological conditions. Daily net C uptake was always detected during the cooler, drier winter months (June through August), while net C loss occurred during the warmer, wetter summer months (December through February). Gross primary productivity (GPP) seasonality was low, despite longer days with higher light intensity in summer, because vapour pressure deficit (D) and air temperature (Ta) restricted surface conductance during summer while winter temperatures were still high enough to support photosynthesis. Maximum GPP during ideal environmental conditions was significantly correlated with remotely sensed enhanced vegetation index (EVI r2 = 0.46) and with canopy leaf area index (LAI r2 = 0.29), which increased rapidly after mid-summer rainfall events. Ecosystem respiration (ER) was highest during summer in wet soils and lowest during winter months. ER had larger seasonal litude compared to GPP, and therefore drove the seasonal variation of NEE. Because summer carbon uptake may become increasingly limited by atmospheric demand and high temperature, and because ecosystem respiration could be enhanced by rising temperatures, our results suggest the potential for large-scale seasonal shifts in NEE in sclerophyll vegetation under climate change.
Comparing the Penman-Monteith equation and a modified Jarvis-Stewart model with an artificial neural network to estimate stand-scale transpiration and canopy conductance
Publisher: Elsevier BV
Date: 06-2009
Cognitive behavioral group therapy for social phobia with or without attention training: A controlled trial
Publisher: Elsevier BV
Date: 05-2009
Evaluation of 11 terrestrial carbon–nitrogen cycle models against observations from two temperate F ree‐A ir CO 2 E nrichment studies
Publisher: Wiley
Date: 28-01-2014
DOI: 10.1111/NPH.12697
Abstract: We analysed the responses of 11 ecosystem models to elevated atmospheric [ CO 2 ] (e CO 2 ) at two temperate forest ecosystems ( D uke and Oak Ridge National Laboratory ( ORNL ) F ree‐ A ir CO 2 E nrichment ( FACE ) experiments) to test alternative representations of carbon ( C )–nitrogen ( N ) cycle processes. We decomposed the model responses into component processes affecting the response to e CO 2 and confronted these with observations from the FACE experiments. Most of the models reproduced the observed initial enhancement of net primary production ( NPP ) at both sites, but none was able to simulate both the sustained 10‐yr enhancement at D uke and the declining response at ORNL : models generally showed signs of progressive N limitation as a result of lower than observed plant N uptake. Nonetheless, many models showed qualitative agreement with observed component processes. The results suggest that improved representation of above‐ground–below‐ground interactions and better constraints on plant stoichiometry are important for a predictive understanding of e CO 2 effects. Improved accuracy of soil organic matter inventories is pivotal to reduce uncertainty in the observed C – N budgets. The two FACE experiments are insufficient to fully constrain terrestrial responses to eCO 2 , given the complexity of factors leading to the observed erging trends, and the consequential inability of the models to explain these trends. Nevertheless, the ecosystem models were able to capture important features of the experiments, lending some support to their projections.
Self-supervised representation learning from multi-domain data
Publisher: IEEE
Date: 10-2019
Multi-Task Pose-Invariant Face Recognition
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2015
Diversified dictionaries for multi-instance learning
Publisher: Elsevier BV
Date: 04-2016
Amazon forest response to CO2 fertilization dependent on plant phosphorus acquisition
Publisher: Springer Science and Business Media LLC
Date: 05-08-2019
Transient dynamics of terrestrial carbon storage: mathematical foundation and its applications
Publisher: Copernicus GmbH
Date: 12-01-2017
Abstract: Abstract. Terrestrial ecosystems have absorbed roughly 30 % of anthropogenic CO2 emissions over the past decades, but it is unclear whether this carbon (C) sink will endure into the future. Despite extensive modeling and experimental and observational studies, what fundamentally determines transient dynamics of terrestrial C storage under global change is still not very clear. Here we develop a new framework for understanding transient dynamics of terrestrial C storage through mathematical analysis and numerical experiments. Our analysis indicates that the ultimate force driving ecosystem C storage change is the C storage capacity, which is jointly determined by ecosystem C input (e.g., net primary production, NPP) and residence time. Since both C input and residence time vary with time, the C storage capacity is time-dependent and acts as a moving attractor that actual C storage chases. The rate of change in C storage is proportional to the C storage potential, which is the difference between the current storage and the storage capacity. The C storage capacity represents instantaneous responses of the land C cycle to external forcing, whereas the C storage potential represents the internal capability of the land C cycle to influence the C change trajectory in the next time step. The influence happens through redistribution of net C pool changes in a network of pools with different residence times. Moreover, this and our other studies have demonstrated that one matrix equation can replicate simulations of most land C cycle models (i.e., physical emulators). As a result, simulation outputs of those models can be placed into a three-dimensional (3-D) parameter space to measure their differences. The latter can be decomposed into traceable components to track the origins of model uncertainty. In addition, the physical emulators make data assimilation computationally feasible so that both C flux- and pool-related datasets can be used to better constrain model predictions of land C sequestration. Overall, this new mathematical framework offers new approaches to understanding, evaluating, diagnosing, and improving land C cycle models.
Computer Therapy for the Anxiety and Depressive Disorders Is Effective, Acceptable and Practical Health Care: A Meta-Analysis
Publisher: Public Library of Science (PLoS)
Date: 13-10-2010
Effects of mesophyll conductance on vegetation responses to elevated CO2 concentrations in a land surface model
Publisher: Wiley
Date: 23-03-2019
DOI: 10.1111/GCB.14604
Stomatal conductance of forest species after long-term exposure to elevated CO2 concentration: A synthesis
Publisher: Wiley
Date: 02-2001
Drought Impacts on Australian Vegetation During the Millennium Drought Measured With Multisource Spaceborne Remote Sensing
Publisher: American Geophysical Union (AGU)
Date: 02-2020
DOI: 10.1029/2019JG005145
Drought by CO2 interactions in trees: a test of the water savings mechanism
Publisher: Wiley
Date: 16-02-2021
DOI: 10.1111/NPH.17233
Abstract: Elevated atmospheric CO 2 (eC a ) may benefit plants during drought by reducing stomatal conductance ( g s ) but any ‘water savings effect’ could be neutralized by concurrent stimulation of leaf area. We investigated whether eC a enhanced water savings, thereby ameliorating the impact of drought on carbon and water relations in trees. We report leaf‐level gas exchange and whole‐plant and soil water relations during a short‐term dry‐down in two Eucalyptus species with contrasting drought tolerance. Plants had previously been established for 9 to 11 months in steady‐state conditions of ambient atmospheric CO 2 (aC a ) and eC a , with half of each treatment group exposed to sustained drought for 5 to 7 months. The lower stomatal conductance under eC a did not lead to soil moisture savings during the dry‐down due to the counteractive effect of increased whole‐plant leaf area. Nonetheless, eC a ‐grown plants maintained higher photosynthetic rates and leaf water potentials, making them less stressed during the dry‐down, despite being larger. These effects were more pronounced in the xeric species than the mesic species, and in previously water‐stressed plants. Our findings indicate that eC a may enhance plant performance during drought despite a lack of soil water savings, especially in species with more conservative growth and water‐use strategies.
On the validation of models of forest CO2 exchange using eddy covariance data: Some perils and pitfalls
Publisher: Oxford University Press (OUP)
Date: 07-2005
DOI: 10.1093/TREEPHYS/25.7.839
Abstract: With the widespread application of eddy covariance technology, long-term records of hourly ecosystem mass and energy exchange are becoming available for forests around the world. These data sets hold great promise for testing and validation of models of forest function. However, model validation is not a straightforward task. The goals of this paper were to: (1) review some of the problems inherent in model validation and (2) survey the tools available to modelers to improve validation procedures, with particular reference to eddy covariance data. A simple set of models applied to a data set of ecosystem CO2 exchange is used to illustrate our points. The major problems discussed are equifinality, insensitivity and uncertainty. Equifinality is the problem that different models, or different parameterizations of the same model, may yield similar results, making it difficult to distinguish which is correct. Insensitivity arises because the major sources of variation in eddy covariance data are the annual and diurnal cycles, which are represented by even the most basic models, and the size of the response to these cycles can mask effects of other driving variables. Uncertainty arises from three main sources: parameters, model structure and data, each of which is discussed in turn. Uncertainty is a particular issue with eddy covariance data because of the lack of replicated measurements and the potential for unquantified systematic errors such as flux loss due to advection. We surveyed several tools that improve model validation, including sensitivity analysis, uncertainty analysis, residual analysis and model comparison. Illustrative ex les are used to demonstrate the use of each tool. We show that simplistic comparisons of model outputs with eddy covariance data are problematic, but use of these tools can greatly improve our confidence in model predictions.
The post-event processing questionnaire in a clinical sample with social phobia
Publisher: Elsevier BV
Date: 11-2006
Implementation of an optimal stomatal conductance scheme in the Australian Community Climate Earth Systems Simulator (ACCESS1.3b)
Publisher: Copernicus GmbH
Date: 08-12-2015
Abstract: Abstract. We implement a new stomatal conductance scheme, based on the optimality approach, within the Community Atmosphere Biosphere Land Exchange (CABLEv2.0.1) land surface model. Coupled land–atmosphere simulations are then performed using CABLEv2.0.1 within the Australian Community Climate and Earth Systems Simulator (ACCESSv1.3b) with prescribed sea surface temperatures. As in most land surface models, the default stomatal conductance scheme only accounts for differences in model parameters in relation to the photosynthetic pathway but not in relation to plant functional types. The new scheme allows model parameters to vary by plant functional type, based on a global synthesis of observations of stomatal conductance under different climate regimes over a wide range of species. We show that the new scheme reduces the latent heat flux from the land surface over the boreal forests during the Northern Hemisphere summer by 0.5–1.0 mm day−1. This leads to warmer daily maximum and minimum temperatures by up to 1.0 °C and warmer extreme maximum temperatures by up to 1.5 °C. These changes generally improve the climate model's climatology of warm extremes and improve existing biases by 10–20 %. The bias in minimum temperatures is however degraded but, overall, this is outweighed by the improvement in maximum temperatures as there is a net improvement in the diurnal temperature range in this region. In other regions such as parts of South and North America where ACCESSv1.3b has known large positive biases in both maximum and minimum temperatures (~ 5 to 10 °C), the new scheme degrades this bias by up to 1 °C. We conclude that, although several large biases remain in ACCESSv1.3b for temperature extremes, the improvements in the global climate model over large parts of the boreal forests during the Northern Hemisphere summer which result from the new stomatal scheme, constrained by a global synthesis of experimental data, provide a valuable advance in the long-term development of the ACCESS modelling system.
Reliable, robust and realistic: The three R's of next-generation land-surface modelling
Publisher: Copernicus GmbH
Date: 29-05-2015
Abstract: Abstract. Land-surface models (LSMs) are increasingly called upon to represent not only the exchanges of energy, water and momentum across the land–atmosphere interface (their original purpose in climate models), but also how ecosystems and water resources respond to climate, atmospheric environment, land-use and land-use change, and how these responses in turn influence land–atmosphere fluxes of carbon dioxide (CO2), trace gases and other species that affect the composition and chemistry of the atmosphere. However, the LSMs embedded in state-of-the-art climate models differ in how they represent fundamental aspects of the hydrological and carbon cycles, resulting in large inter-model differences and sometimes faulty predictions. These "third-generation" LSMs respect the close coupling of the carbon and water cycles through plants, but otherwise tend to be under-constrained, and have not taken full advantage of robust hydrological parameterizations that were independently developed in offline models. Benchmarking, combining multiple sources of atmospheric, biospheric and hydrological data, should be a required component of LSM development, but this field has been relatively poorly supported and intermittently pursued. Moreover, benchmarking alone is not sufficient to ensure that models improve. Increasing complexity may increase realism but decrease reliability and robustness, by increasing the number of poorly known model parameters. In contrast, simplifying the representation of complex processes by stochastic parameterization (the representation of unresolved processes by statistical distributions of values) has been shown to improve model reliability and realism in both atmospheric and land-surface modelling contexts. We provide ex les for important processes in hydrology (the generation of runoff and flow routing in heterogeneous catchments) and biology (carbon uptake by species- erse ecosystems). We propose that the way forward for next-generation complex LSMs will include: (a) representations of biological and hydrological processes based on the implementation of multiple internal constraints (b) systematic application of benchmarking and data assimilation techniques to optimize parameter values and thereby test the structural adequacy of models and (c) stochastic parameterization of unresolved variability, applied in both the hydrological and the biological domains.
SPA: Spatially Pooled Attributes for image retrieval
Publisher: Elsevier BV
Date: 09-2017
Near-optimal response of instantaneous transpiration efficiency to vapour pressure deficit, temperature and [CO2 ] in cotton (Gossypium hirsutum L.)
Publisher: Elsevier BV
Date: 2013
Using models to guide field experiments: a priori predictions for the CO 2 response of a nutrient‐ and water‐limited native Eucalypt woodland
Publisher: Wiley
Date: 09-05-2016
DOI: 10.1111/GCB.13268
Abstract: The response of terrestrial ecosystems to rising atmospheric CO2 concentration (Ca ), particularly under nutrient-limited conditions, is a major uncertainty in Earth System models. The Eucalyptus Free-Air CO2 Enrichment (EucFACE) experiment, recently established in a nutrient- and water-limited woodland presents a unique opportunity to address this uncertainty, but can best do so if key model uncertainties have been identified in advance. We applied seven vegetation models, which have previously been comprehensively assessed against earlier forest FACE experiments, to simulate a priori possible outcomes from EucFACE. Our goals were to provide quantitative projections against which to evaluate data as they are collected, and to identify key measurements that should be made in the experiment to allow discrimination among alternative model assumptions in a postexperiment model intercomparison. Simulated responses of annual net primary productivity (NPP) to elevated Ca ranged from 0.5 to 25% across models. The simulated reduction of NPP during a low-rainfall year also varied widely, from 24 to 70%. Key processes where assumptions caused disagreement among models included nutrient limitations to growth feedbacks to nutrient uptake autotrophic respiration and the impact of low soil moisture availability on plant processes. Knowledge of the causes of variation among models is now guiding data collection in the experiment, with the expectation that the experimental data can optimally inform future model improvements.
Predicting resilience through the lens of competing adjustments to vegetation function
Publisher: Wiley
Date: 06-07-2022
DOI: 10.1111/PCE.14376
Abstract: There is a pressing need to better understand ecosystem resilience to droughts and heatwaves. Eco‐evolutionary optimization approaches have been proposed as means to build this understanding in land surface models and improve their predictive capability, but competing approaches are yet to be tested together. Here, we coupled approaches that optimize canopy gas exchange and leaf nitrogen investment, respectively, extending both approaches to account for hydraulic impairment. We assessed model predictions using observations from a native Eucalyptus woodland that experienced repeated droughts and heatwaves between 2013 and 2020, whilst exposed to an elevated [CO 2 ] treatment. Our combined approaches improved predictions of transpiration and enhanced the simulated magnitude of the CO 2 fertilization effect on gross primary productivity. The competing approaches also worked consistently along axes of change in soil moisture, leaf area, and [CO 2 ]. Despite predictions of a significant percentage loss of hydraulic conductivity due to embolism (PLC) in 2013, 2014, 2016, and 2017 (99th percentile PLC 45%), simulated hydraulic legacy effects were small and short‐lived (2 months). Our analysis suggests that leaf shedding and/or suppressed foliage growth formed a strategy to mitigate drought risk. Accounting for foliage responses to water availability has the potential to improve model predictions of ecosystem resilience.
Optimal stomatal behaviour around the world
Publisher: Springer Science and Business Media LLC
Date: 02-03-2015
DOI: 10.1038/NCLIMATE2550
Interactive effects of elevated CO 2 and drought on nocturnal water fluxes in Eucalyptus saligna
Publisher: Oxford University Press (OUP)
Date: 25-05-2011
Abstract: Nocturnal water flux has been observed in trees under a variety of environmental conditions and can be a significant contributor to diel canopy water flux. Elevated atmospheric CO(2) (elevated [CO(2)]) can have an important effect on day-time plant water fluxes, but it is not known whether it also affects nocturnal water fluxes. We examined the effects of elevated [CO(2)] on nocturnal water flux of field-grown Eucalyptus saligna trees using sap flux through the tree stem expressed on a sapwood area (J(s)) and leaf area (E(t)) basis. After 19 months growth under well-watered conditions, drought was imposed by withholding water for 5 months in the summer, ending with a rain event that restored soil moisture. Reductions in J(s) and E(t) were observed during the severe drought period in the dry treatment under elevated [CO(2)], but not during moderate- and post-drought periods. Elevated [CO(2)] affected night-time sap flux density which included the stem recharge period, called 'total night flux' (19:00 to 05:00, J(s,r)), but not during the post-recharge period, which primarily consisted of canopy transpiration (23:00 to 05:00, J(s,c)). Elevated [CO(2)] wet (EW) trees exhibited higher J(s,r) than ambient [CO(2)] wet trees (AW) indicating greater water flux in elevated [CO(2)] under well-watered conditions. However, under drought conditions, elevated [CO(2)] dry (ED) trees exhibited significantly lower J(s,r) than ambient [CO(2)] dry trees (AD), indicating less water flux during stem recharge under elevated [CO(2)]. J(s,c) did not differ between ambient and elevated [CO(2)]. Vapour pressure deficit (D) was clearly the major influence on night-time sap flux. D was positively correlated with J(s,r) and had its greatest impact on J(s,r) at high D in ambient [CO(2)]. Our results suggest that elevated [CO(2)] may reduce night-time water flux in E. saligna when soil water content is low and D is high. While elevated [CO(2)] affected J(s,r), it did not affect day-time water flux in wet soil, suggesting that the responses of J(s,r) to environmental factors cannot be directly inferred from day-time patterns. Changes in J(s,r) are likely to influence pre-dawn leaf water potential, and plant responses to water stress. Nocturnal fluxes are clearly important for predicting effects of climate change on forest physiology and hydrology.
Temperature responses of leaf net photosynthesis: The role of component processes
Publisher: Oxford University Press (OUP)
Date: 25-01-2012
Abstract: The response of photosynthesis to temperature is a central facet of plant response to climate. Such responses have been found to be highly variable among species and among studies. Understanding this variability is key when trying to predict the effects of rising global temperatures on plant productivity. There are three major factors affecting the response of leaf net photosynthesis to temperature (A(n)-T): (i) photosynthetic biochemistry, (ii) respiration and (iii) vapour pressure deficit (D) and stomatal sensitivity to vapour pressure deficit during measurements. The overall goal of our study was to quantify the relative contribution of each of these factors in determining the response of A(n) to temperature. We first conducted a sensitivity analysis with a coupled photosynthesis-stomatal (A(n)-g(s)) model, using ranges for parameters of each factor taken from the literature, and quantified how these parameters affected the A(n)-T response. Second, we applied the A(n)-g(s) model to two ex le sets of field data, which had different optimum temperatures (T(opt)) of A(n), to analyse which factors were most important in causing the difference. We found that each of the three factors could have an equally large effect on T(opt) of A(n). In our comparison between two field datasets, the major cause for the difference in T(opt) was not the biochemical component, but rather the differences in respiratory components and in D conditions during measurements. We concluded that shifts in A(n)-T responses are not always driven by acclimation of photosynthetic biochemistry, but can result from other factors. The D conditions during measurements and stomatal responses to D also need to be quantified if we are to better understand and predict shifts in A(n)-T with climate.
Leaf age-related and diurnal variation in gas exchange of kauri (Agathis australis)
Publisher: Informa UK Limited
Date: 13-10-2017
The relationship between worry, rumination, and comorbidity: Evidence for repetitive negative thinking as a transdiagnostic construct
Publisher: Elsevier BV
Date: 10-2013
Effects of elevated atmospheric [CO2 ] on instantaneous transpiration efficiency at leaf and canopy scales in Eucalyptus saligna
Publisher: Wiley
Date: 19-09-2012
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
Supplementary material to "Do land surface models need to include differential plant species responses to drought? Examining model predictions across a latitudinal gradient in Europe"
Publisher: Copernicus GmbH
Date: 06-08-2015
Plant root distributions and nitrogen uptake predicted by a hypothesis of optimal root foraging
Publisher: Wiley
Date: 21-05-2012
DOI: 10.1002/ECE3.266
Forest water use and water use efficiency at elevated CO2 FACE sites
Publisher: Wiley
Date: 25-03-2013
DOI: 10.1111/GCB.12164
Abstract: Predicted responses of transpiration to elevated atmospheric CO2 concentration (eCO2 ) are highly variable amongst process-based models. To better understand and constrain this variability amongst models, we conducted an intercomparison of 11 ecosystem models applied to data from two forest free-air CO2 enrichment (FACE) experiments at Duke University and Oak Ridge National Laboratory. We analysed model structures to identify the key underlying assumptions causing differences in model predictions of transpiration and canopy water use efficiency. We then compared the models against data to identify model assumptions that are incorrect or are large sources of uncertainty. We found that model-to-model and model-to-observations differences resulted from four key sets of assumptions, namely (i) the nature of the stomatal response to elevated CO2 (coupling between photosynthesis and stomata was supported by the data) (ii) the roles of the leaf and atmospheric boundary layer (models which assumed multiple conductance terms in series predicted more decoupled fluxes than observed at the broadleaf site) (iii) the treatment of canopy interception (large intermodel variability, 2-15%) and (iv) the impact of soil moisture stress (process uncertainty in how models limit carbon and water fluxes during moisture stress). Overall, model predictions of the CO2 effect on WUE were reasonable (intermodel μ = approximately 28% ± 10%) compared to the observations (μ = approximately 30% ± 13%) at the well-coupled coniferous site (Duke), but poor (intermodel μ = approximately 24% ± 6% observations μ = approximately 38% ± 7%) at the broadleaf site (Oak Ridge). The study yields a framework for analysing and interpreting model predictions of transpiration responses to eCO2 , and highlights key improvements to these types of models.
Where does the carbon go? A model–data intercomparison of vegetation carbon allocation and turnover processes at two temperate forest free‐air CO2 enrichment sites
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.
A test of the 'one-point method' for estimating maximum carboxylation capacity from field-measured, light-saturated photosynthesis
Publisher: Wiley
Date: 31-12-2016
DOI: 10.1111/NPH.13815
Abstract: Simulations of photosynthesis by terrestrial biosphere models typically need a specification of the maximum carboxylation rate ( V cmax ). Estimating this parameter using A – C i curves (net photosynthesis, A , vs intercellular CO 2 concentration, C i ) is laborious, which limits availability of V cmax data. However, many multispecies field datasets include net photosynthetic rate at saturating irradiance and at ambient atmospheric CO 2 concentration ( A sat ) measurements, from which V cmax can be extracted using a ‘one‐point method’. We used a global dataset of A – C i curves (564 species from 46 field sites, covering a range of plant functional types) to test the validity of an alternative approach to estimate V cmax from A sat via this ‘one‐point method’. If leaf respiration during the day ( R day ) is known exactly, V cmax can be estimated with an r 2 value of 0.98 and a root‐mean‐squared error ( RMSE ) of 8.19 μmol m −2 s −1 . However, R day typically must be estimated. Estimating R day as 1.5% of V cmax, we found that V cmax could be estimated with an r 2 of 0.95 and an RMSE of 17.1 μmol m −2 s −1 . The one‐point method provides a robust means to expand current databases of field‐measured V cmax , giving new potential to improve vegetation models and quantify the environmental drivers of V cmax variation.
Common versus unique variance across measures of worry and rumination: Predictive utility and mediational models for anxiety and depression
Publisher: Springer Science and Business Media LLC
Date: 15-03-2013
CO 2 enhancement of forest productivity constrained by limited nitrogen availability
Publisher: Proceedings of the National Academy of Sciences
Date: 25-10-2010
Abstract: Stimulation of terrestrial plant production by rising CO 2 concentration is projected to reduce the airborne fraction of anthropogenic CO 2 emissions. Coupled climate–carbon cycle models are sensitive to this negative feedback on atmospheric CO 2 , but model projections are uncertain because of the expectation that feedbacks through the nitrogen (N) cycle will reduce this so-called CO 2 fertilization effect. We assessed whether N limitation caused a reduced stimulation of net primary productivity (NPP) by elevated atmospheric CO 2 concentration over 11 y in a free-air CO 2 enrichment (FACE) experiment in a deciduous Liquidambar styraciflua (sweetgum) forest stand in Tennessee. During the first 6 y of the experiment, NPP was significantly enhanced in forest plots exposed to 550 ppm CO 2 compared with NPP in plots in current ambient CO 2 , and this was a consistent and sustained response. However, the enhancement of NPP under elevated CO 2 declined from 24% in 2001–2003 to 9% in 2008. Global analyses that assume a sustained CO 2 fertilization effect are no longer supported by this FACE experiment. N budget analysis supports the premise that N availability was limiting to tree growth and declining over time —an expected consequence of stand development, which was exacerbated by elevated CO 2 . Leaf- and stand-level observations provide mechanistic evidence that declining N availability constrained the tree response to elevated CO 2 these observations are consistent with stand-level model projections. This FACE experiment provides strong rationale and process understanding for incorporating N limitation and N feedback effects in ecosystem and global models used in climate change assessments.
Discriminative Multi-View Interactive Image Re-Ranking
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2017
More than iso/anisohydry: Hydroscapes integrate plant water use and drought tolerance traits in 10 eucalypt species from contrasting climates
Publisher: Wiley
Date: 07-04-2019
Spatial–Temporal Attention-Based Human Dynamics Retrospection
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2019
Does the growth response of woody plants to elevated CO 2 increase with temperature? A model‐oriented meta‐analysis
Publisher: Wiley
Date: 22-09-2015
DOI: 10.1111/GCB.12962
Abstract: The temperature dependence of the reaction kinetics of the Rubisco enzyme implies that, at the level of a chloroplast, the response of photosynthesis to rising atmospheric CO2 concentration (Ca ) will increase with increasing air temperature. Vegetation models incorporating this interaction predict that the response of net primary productivity (NPP) to elevated CO2 (eCa ) will increase with rising temperature and will be substantially larger in warm tropical forests than in cold boreal forests. We tested these model predictions against evidence from eCa experiments by carrying out two meta-analyses. Firstly, we tested for an interaction effect on growth responses in factorial eCa × temperature experiments. This analysis showed a positive, but nonsignificant interaction effect (95% CI for above-ground biomass response = -0.8, 18.0%) between eCa and temperature. Secondly, we tested field-based eCa experiments on woody plants across the globe for a relationship between the eCa effect on plant biomass and mean annual temperature (MAT). This second analysis showed a positive but nonsignificant correlation between the eCa response and MAT. The magnitude of the interactions between CO2 and temperature found in both meta-analyses were consistent with model predictions, even though both analyses gave nonsignificant results. Thus, we conclude that it is not possible to distinguish between the competing hypotheses of no interaction vs. an interaction based on Rubisco kinetics from the available experimental database. Experiments in a wider range of temperature zones are required. Until such experimental data are available, model predictions should aim to incorporate uncertainty about this interaction.
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).
Mechanisms of woody-plant mortality under rising drought, CO2 and vapour pressure deficit
Publisher: Springer Science and Business Media LLC
Date: 29-03-2022
TRY plant trait database – enhanced coverage and open access
Publisher: Wiley
Date: 31-12-2019
DOI: 10.1111/GCB.14904
Abstract: Plant traits—the morphological, anatomical, physiological, biochemical and phenological characteristics of plants—determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to bio ersity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait‐based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits—almost complete coverage for ‘plant growth form’. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait–environmental relationships. These traits have to be measured on in idual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives.
Matrix Factorization for Collaborative Budget Allocation
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2018
Robust Extreme Multi-label Learning
Publisher: ACM
Date: 13-08-2016
Hydraulic failure and tree size linked with canopy die‐back in eucalypt forest during extreme drought
Publisher: Wiley
Date: 03-04-2021
DOI: 10.1111/NPH.17298
Abstract: Eastern Australia was subject to its hottest and driest year on record in 2019. This extreme drought resulted in massive canopy die‐back in eucalypt forests. The role of hydraulic failure and tree size on canopy die‐back in three eucalypt tree species during this drought was examined. We measured pre‐dawn and midday leaf water potential (Ψ leaf ), per cent loss of stem hydraulic conductivity and quantified hydraulic vulnerability to drought‐induced xylem embolism. Tree size and tree health was also surveyed. Trees with most, or all, of their foliage dead exhibited high rates of native embolism (78–100%). This is in contrast to trees with partial canopy die‐back (30–70% canopy die‐back: 72–78% native embolism), or relatively healthy trees (little evidence of canopy die‐back: 25–31% native embolism). Midday Ψ leaf was significantly more negative in trees exhibiting partial canopy die‐back (−2.7 to −6.3 MPa), compared with relatively healthy trees (−2.1 to −4.5 MPa). In two of the species the majority of in iduals showing complete canopy die‐back were in the small size classes. Our results indicate that hydraulic failure is strongly associated with canopy die‐back during drought in eucalypt forests. Our study provides valuable field data to help constrain models predicting mortality risk.
Optimal stomatal conductance in relation to photosynthesis in climatically contrasting Eucalyptus species under drought
Publisher: Wiley
Date: 07-08-2013
DOI: 10.1111/J.1365-3040.2012.02570.X
Abstract: Models of stomatal conductance (g(s)) are based on coupling between g(s) and CO(2) assimilation (A(net)), and it is often assumed that the slope of this relationship ('g(1) ') is constant across species. However, if different plant species have adapted to different access costs of water, then there will be differences in g(1) among species. We hypothesized that g(1) should vary among species adapted to different climates, and tested the theory and its linkage to plant hydraulics using four Eucalyptus species from different climatic origins in a common garden. Optimal stomatal theory predicts that species from sub-humid zones have a lower marginal water cost of C gain, hence lower g(1) than humid-zone species. In agreement with the theory that g(1) is related to tissue carbon costs for water supply, we found a relationship between wood density and g(1) across Eucalyptus species of contrasting climatic origins. There were significant reductions in the parameter g(1) during drought in humid but not sub-humid species, with the latter group maintaining g(1) in drought. There are strong differences in stomatal behaviour among related tree species in agreement with optimal stomatal theory, and these differences are consistent with the economics involved in water uptake and transport for carbon gain.
Long-term water stress leads to acclimation of drought sensitivity of photosynthetic capacity in xeric but not riparian Eucalyptus species
Publisher: Oxford University Press (OUP)
Date: 22-10-2016
DOI: 10.1093/AOB/MCV161
Corrigendum: Reconciling the optimal and empirical approaches to modelling stomatal conductance
Publisher: Wiley
Date: 04-10-2012
Short-term water stress impacts on stomatal, mesophyll and biochemical limitations to photosynthesis differ consistently among tree species from contrasting climates
Publisher: Oxford University Press (OUP)
Date: 04-09-2014
Abstract: Predicting the large-scale consequences of drought in contrasting environments requires that we understand how drought effects differ among species originating from those environments. A previous meta-analysis of published experiments suggested that the effects of drought on both stomatal and non-stomatal limitations to photosynthesis may vary consistently among species from different hydroclimates. Here, we explicitly tested this hypothesis with two short-term water stress experiments on congeneric mesic and xeric species. One experiment was run in Australia using Eucalyptus species and the second was run in Spain using Quercus species as well as two more mesic species. In each experiment, plants were grown under moist conditions in a glasshouse, then deprived of water, and gas exchange was monitored. The stomatal response was analysed with a recently developed stomatal model, whose single parameter g1 represents the slope of the relationship between stomatal conductance and photosynthesis. The non-stomatal response was partitioned into effects on mesophyll conductance (gm), the maximum Rubisco activity (Vcmax) and the maximum electron transport rate (Jmax). We found consistency among the drought responses of g1, gm, Vcmax and Jmax, suggesting that drought imposes limitations on Rubisco activity and RuBP regeneration capacity concurrently with declines in stomatal and mesophyll conductance. Within each experiment, the more xeric species showed relatively high g1 under moist conditions, low drought sensitivity of g1, gm, Vcmax and Jmax, and more negative values of the critical pre-dawn water potential at which Vcmax declines most steeply, compared with the more mesic species. These results indicate adaptive interspecific differences in drought responses that allow xeric tree species to continue transpiration and photosynthesis for longer during periods without rain.
Gross primary production responses to warming, elevated CO 2, and irrigation: quantifying the drivers of ecosystem physiology in a semiarid grassland
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
Nocturnal stomatal conductance responses to rising [CO 2 ], temperature and drought
Publisher: Wiley
Date: 09-12-2012
DOI: 10.1111/J.1469-8137.2011.03993.X
Abstract: The response of nocturnal stomatal conductance (g(s,n)) to rising atmospheric CO(2) concentration ([CO(2)]) is currently unknown, and may differ from responses of daytime stomatal conductance (g(s,d)). Because night-time water fluxes can have a significant impact on landscape water budgets, an understanding of the effects of [CO(2)] and temperature on g(s,n) is crucial for predicting water fluxes under future climates. Here, we examined the effects of [CO(2)] (280, 400 and 640 μmol mol(-1)), temperature (ambient and ambient + 4°C) and drought on g(s,n,) and g(s,d) in Eucalyptus sideroxylon saplings. g(s,n) was substantially higher than zero, averaging 34% of g(s,d). Before the onset of drought, g(s,n) increased by 85% when [CO(2)] increased from 280 to 640 μmol mol(-1), averaged across both temperature treatments. g(s,n) declined with drought, but an increase in [CO(2)] slowed this decline. Consequently, the soil water potential at which g(s,n) was zero (Ψ(0)) was significantly more negative in elevated [CO(2)] and temperature treatments. g(s,d) showed inconsistent responses to [CO(2)] and temperature. g (s,n) may be higher in future climates, potentially increasing nocturnal water loss and susceptibility to drought, but cannot be predicted easily from g(s,d). Therefore, predictive models using stomatal conductance must account for both g(s,n) and g(s,d) when estimating ecosystem water fluxes.
Reinforced molecule generation with heterogeneous states
Publisher: IEEE
Date: 11-2019
The fate of carbon in a mature forest under carbon dioxide enrichment
Publisher: Springer Science and Business Media LLC
Date: 08-04-2020
Achieving certainty about the structure of intolerance of uncertainty in a treatment-seeking sample with anxiety and depression
Publisher: Elsevier BV
Date: 2011
Stomatal and non-stomatal limitations of photosynthesis for four tree species under drought: A comparison of model formulations
Publisher: Elsevier BV
Date: 12-2017
Independent Feature and Label Components for Multi-label Classification
Publisher: IEEE
Date: 11-2018
The optimal allocation of nitrogen within the C3 photosynthetic system at elevated CO2
Publisher: CSIRO Publishing
Date: 1996
DOI: 10.1071/PP9960593
Abstract: The distribution of nitrogen among compounds involved in photosynthesis varies in response to changes in environmental conditions such as photon flux density. However, the extent to which the nitrogen distribution within leaves adjusts in response to increased atmospheric CO2 is unclear. A model was used to determine the nitrogen distribution which maximises photosynthesis under realistic light regimes at both current and elevated levels of CO2, and a comparison was made with observed leaf nitrogen distributions reported in the literature. The model accurately predicted the distribution of nitrogen within the photosynthetic system for leaves grown at current levels of CO2, except at very high leaf nitrogen contents. The model predicted that, under a doubling of CO2 concentration from its current level, the ratio of electron transport capacity to Rubisco activity (Jmax : Vcmax) should increase by 40%. In contrast, measurements of Jmax : Vcmax taken from the literature show a slight but non-significant increase in response to an increase in CO2. The discrepancy between predicted and observed Jmax : Vcmax suggests that leaf nitrogen distribution does not acclimate optimally to elevated CO2. Alternatively, the discrepancy may be due to effects of CO2 which the model fails to take into account, such as a possible decrease in the conductance to CO2 transfer between the intercellular spaces and the sites of carboxylation at elevated CO2.
Towards Evolutionary Compression
Publisher: ACM
Date: 19-07-2018
Local Rademacher Complexity for Multi-Label Learning
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2016
MAESPA: A model to study interactions between water limitation, environmental drivers and vegetation function at tree and stand levels, with an example application to [CO2 ] × drought interactions
Publisher: Copernicus GmbH
Date: 05-07-2012
Abstract: Abstract. Process-based models (PBMs) of vegetation function can be used to interpret and integrate experimental results. Water limitation to plant carbon uptake is a highly uncertain process in the context of environmental change, and many experiments have been carried out that study drought limitations to vegetation function at spatial scales from seedlings to entire canopies. What is lacking in the synthesis of these experiments is a quantitative tool incorporating a detailed mechanistic representation of the water balance that can be used to integrate and analyse experimental results at scales of both the whole-plant and the forest canopy. To fill this gap, we developed an in idual tree-based model (MAESPA), largely based on combining the well-known MAESTRA and SPA ecosystem models. The model includes a hydraulically-based model of stomatal conductance, root water uptake routines, drainage, infiltration, runoff and canopy interception, as well as detailed radiation interception and leaf physiology routines from the MAESTRA model. The model can be applied both to single plants of arbitrary size and shape, as well as stands of trees. The utility of this model is demonstrated by studying the interaction between elevated [CO2] (eCa) and drought. Based on theory, this interaction is generally expected to be positive, so that plants growing in eCa should be less susceptible to drought. Experimental results, however, are varied. We apply the model to a previously published experiment on droughted cherry, and show that changes in plant parameters due to long-term growth at eCa (acclimation) may strongly affect the outcome of Ca × drought experiments. We discuss potential applications of MAESPA and some of the key uncertainties in process representation.
Identifying areas at risk of drought‐induced tree mortality across South‐Eastern Australia
Publisher: Wiley
Date: 19-08-2020
DOI: 10.1111/GCB.15215
Volatile isoprenoid emissions from plastid to planet
Publisher: Wiley
Date: 12-11-2012
DOI: 10.1111/NPH.12021
Abstract: Approximately 1–2% of net primary production by land plants is re‐emitted to the atmosphere as isoprene and monoterpenes. These emissions play major roles in atmospheric chemistry and air pollution–climate interactions. Phenomenological models have been developed to predict their emission rates, but limited understanding of the function and regulation of these emissions has led to large uncertainties in model projections of air quality and greenhouse gas concentrations. We synthesize recent advances in erse fields, from cell physiology to atmospheric remote sensing, and use this information to propose a simple conceptual model of volatile isoprenoid emission based on regulation of metabolism in the chloroplast. This may provide a robust foundation for scaling up emissions from the cellular to the global scale.
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.
Effectiveness of cognitive behavioural group therapy for social phobia in a community clinic: A benchmarking study
Publisher: Elsevier BV
Date: 12-2007
Model–data synthesis for the next generation of forest free‐air CO 2 enrichment (FACE ) experiments
Publisher: Wiley
Date: 06-08-2015
DOI: 10.1111/NPH.13593
Abstract: The first generation of forest free‐air CO 2 enrichment ( FACE ) experiments has successfully provided deeper understanding about how forests respond to an increasing CO 2 concentration in the atmosphere. Located in aggrading stands in the temperate zone, they have provided a strong foundation for testing critical assumptions in terrestrial biosphere models that are being used to project future interactions between forest productivity and the atmosphere, despite the limited inference space of these experiments with regards to the range of global ecosystems. Now, a new generation of FACE experiments in mature forests in different biomes and over a wide range of climate space and bio ersity will significantly expand the inference space. These new experiments are: Euc FACE in a mature Eucalyptus stand on highly weathered soil in subtropical Australia Amazon FACE in a highly erse, primary rainforest in Brazil BIF oR‐ FACE in a 150‐yr‐old deciduous woodland stand in central England and Swed FACE proposed in a hemiboreal, Pinus sylvestris stand in Sweden. We now have a unique opportunity to initiate a model–data interaction as an integral part of experimental design and to address a set of cross‐site science questions on topics including responses of mature forests interactions with temperature, water stress, and phosphorus limitation and the influence of bio ersity.
Light interception efficiency explained by two simple variables: A test using a diversity of small- to medium-sized woody plants
Publisher: Wiley
Date: 08-11-2012
DOI: 10.1111/J.1469-8137.2011.03943.X
Abstract: • Plant light interception efficiency is a crucial determinant of carbon uptake by in idual plants and by vegetation. Our aim was to identify whole-plant variables that summarize complex crown architecture, which can be used to predict light interception efficiency. • We gathered the largest database of digitized plants to date (1831 plants of 124 species), and estimated a measure of light interception efficiency with a detailed three-dimensional model. Light interception efficiency was defined as the ratio of the hemispherically averaged displayed to total leaf area. A simple model was developed that uses only two variables, crown density (the ratio of leaf area to total crown surface area) and leaf dispersion (a measure of the degree of aggregation of leaves). • The model explained 85% of variation in the observed light interception efficiency across the digitized plants. Both whole-plant variables varied across species, with differences in leaf dispersion related to leaf size. Within species, light interception efficiency decreased with total leaf number. This was a result of changes in leaf dispersion, while crown density remained constant. • These results provide the basis for a more general understanding of the role of plant architecture in determining the efficiency of light harvesting.
Learning from multiple teacher networks
Publisher: ACM
Date: 04-08-2017
Internet treatment for social phobia reduces comorbidity
Publisher: SAGE Publications
Date: 2009
DOI: 10.1080/00048670903001992
Abstract: Objective: Social phobia can be treated by brief Internet-based cognitive behaviour therapy (CBT). Most people with social phobia, however, meet criteria for another mental disorder this comorbidity is associated with significant disability, and cases of comorbidity may be more difficult to treat. The present study examined the impact of the Shyness programme, an Internet-based treatment programme for social phobia, on comorbid symptoms of depression and generalized anxiety disorder. Method: Data from three randomized controlled trials using the Shyness programme to treat social phobia were reanalysed. The 211 subjects, all of whom met DSM-IV criteria for social phobia, were ided into four groups: (i) social phobia only (ii) social phobia with elevated symptoms of depression (iii) social phobia with elevated symptoms of generalized anxiety and (iv) social phobia with elevated symptoms of both generalized anxiety and depression. The improvement in social phobia, depression and anxiety following Internet-based treatment for social phobia was measured. Results: Improvement in social phobia was seen in all groups, whether comorbid or not. Significant improvements in comorbid symptoms of depression and generalized anxiety occurred even though the treatment was focused on the social phobia. Conclusions: Brief Internet-based CBT can reduce both the target disorder as well as comorbid symptoms. These findings are consistent with evidence that unified or transdiagnostic programmes may reduce the severity of comorbid disorders and symptoms, indicating an important direction for future research.
Visual and hydraulic techniques produce similar estimates of cavitation resistance in woody species
Publisher: Wiley
Date: 26-07-2020
DOI: 10.1111/NPH.16746
Abstract: Hydraulic failure of the plant vascular system is a principal cause of forest die‐off under drought. Accurate quantification of this process is essential to our understanding of the physiological mechanisms underpinning plant mortality. Imaging techniques increasingly are applied to estimate xylem cavitation resistance. These techniques allow for in situ measurement of embolism formation in real time, although the benefits and trade‐offs associated with different techniques have not been evaluated in detail. Here we compare two imaging methods, microcomputed tomography (microCT) and optical vulnerability (OV), to standard hydraulic methods for measurement of cavitation resistance in seven woody species representing a ersity of major phylogenetic and xylem anatomical groups. Across the seven species, there was strong agreement between cavitation resistance values (P 50 ) estimated from visualization techniques (microCT and OV) and between visual techniques and hydraulic techniques. The results indicate that visual techniques provide accurate estimates of cavitation resistance and the degree to which xylem hydraulic function is impacted by embolism. Results are discussed in the context of trade‐offs associated with each technique and possible causes of discrepancy between estimates of cavitation resistance provided by visual and hydraulic techniques.
Integrating the evidence for a terrestrial carbon sink caused by increasing atmospheric CO2
Publisher: Wiley
Date: 21-10-2020
DOI: 10.1111/NPH.16866
Abstract: Atmospheric carbon dioxide concentration ([CO 2 ]) is increasing, which increases leaf‐scale photosynthesis and intrinsic water‐use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO 2 ] increase and thus climate change. However, ecosystem CO 2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO 2 ]‐driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO 2 ] (iCO 2 ) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre‐industrial times. Established theory, supported by experiments, indicates that iCO 2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO 2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO 2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO 2 , albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change.
Transdiagnostic internet treatment for anxiety and depression: A randomised controlled trial
Publisher: Elsevier BV
Date: 08-2011
Online Dictionary Learning with Confidence
Publisher: IEEE
Date: 11-2018
Measuring and modelling energy partitioning in canopies of varying complexity using MAESPA model
Publisher: Elsevier BV
Date: 05-2018
Adaptive plasticity in plant traits increases time to hydraulic failure under drought in a foundation tree
Publisher: Cold Spring Harbor Laboratory
Date: 20-08-2020
DOI: 10.1101/2020.08.19.258186
Abstract: The viability of forest trees, in response to climate change-associated drought, will depend on their capacity to survive through genetic adaptation and phenotypic plasticity in drought tolerance traits. Genotypes with enhanced plasticity for drought tolerance (adaptive plasticity) will have a greater ability to persist and delay the onset of hydraulic failure. Corymbia calophylla populations from two contrasting climate-origins (warm-dry and cool-wet) were grown under well-watered and chronic soil water deficit treatments in large containers. Hydraulic and allometric traits were measured and then trees were dried-down to critical levels of drought stress. Significant plasticity was detected in the warm-dry population in response to water-deficit, with adjustments in drought tolerance traits that resulted in longer dry-down times from stomatal closure to 88% loss of stem hydraulic conductance (time to hydraulic failure, THF). Plasticity was limited in the cool-wet population, indicating a significant genotype-by-environment interaction in THF. Our findings contribute information on intraspecific variation in key drought tolerance traits and THF. It highlights the need to quantify adaptive capacity in populations of forest trees facing climate change-type drought to improve predictions of forest die-back. Corymbia calophylla may benefit from assisted gene migration by introducing adaptive warm-dry populations into vulnerable cool-wet population regions.
Analytical clustering score with application to postplacement register clustering
Publisher: Association for Computing Machinery (ACM)
Date: 11-05-2016
DOI: 10.1145/2894753
Abstract: Circuit clustering is usually done through discrete optimizations to enable circuit size reduction or design-specific cluster formation. In this article, we are interested in the register-clustering technique for clock-power reduction by leveraging new opportunities introduced by multibit flip-flop (MBFF). Currently, INTEGRA is the only existing postplacement MBFF clustering optimizer with a subquadratic time complexity. However, it severely degrades the wirelength, especially for realistic designs, which may nullify the benefits of MBFF clustering. In contrast, we formulate an analytical clustering score with a nonlinear programming framework, in which the wirelength objective can be seamlessly integrated and the solver has empirical subquadratic time complexity. With the MBFF library, the application of our analytical clustering method achieves comparable clock power to the state-of-the-art techniques, but further reduces the wirelength by about 25%. Even without the MBFF library, we can still achieve 30% clock wirelength reduction. In addition, the proposed method can potentially be integrated into an in-placement MBFF clustering solver and be applied to other problems that require formulating clustering scores in their objective functions.
Triose phosphate utilization limitation: an unnecessary complexity in terrestrial biosphere model representation of photosynthesis
Publisher: Wiley
Date: 17-12-2021
DOI: 10.1111/NPH.17092
Tree hydraulic traits are coordinated and strongly linked to climate-of-origin across a rainfall gradient
Publisher: Wiley
Date: 29-01-2018
DOI: 10.1111/PCE.13129
Abstract: Plant hydraulic traits capture the impacts of drought stress on plant function, yet vegetation models lack sufficient information regarding trait coordination and variation with climate-of-origin across species. Here, we investigated key hydraulic and carbon economy traits of 12 woody species in Australia from a broad climatic gradient, with the aim of identifying the coordination among these traits and the role of climate in shaping cross-species trait variation. The influence of environmental variation was minimized by a common garden approach, allowing us to factor out the influence of environment on phenotypic variation across species. We found that hydraulic traits (leaf turgor loss point, stomatal sensitivity to drought [P
Drought-related leaf functional traits control spatial and temporal dynamics of live fuel moisture content
Publisher: Elsevier BV
Date: 05-2022
Reconciling the optimal and empirical approaches to modelling stomatal conductance
Publisher: Wiley
Date: 11-01-2011
Carbon dioxide stimulation of photosynthesis in Liquidambar styraciflua is not sustained during a 12-year field experiment
Publisher: Oxford University Press (OUP)
Date: 2015
Reliable, robust and realistic: The three R's of next-generation land surface modelling
Publisher: Copernicus GmbH
Date: 26-09-2014
DOI: 10.5194/ACPD-14-24811-2014
Abstract: Abstract. Land surface models (LSMs) are increasingly called upon to represent not only the exchanges of energy, water and momentum across the land-atmosphere interface (their original purpose in climate models), but also how ecosystems and water resources respond to climate and atmospheric environment, and how these responses in turn influence land-atmosphere fluxes of carbon dioxide (CO2), trace gases and other species that affect the composition and chemistry of the atmosphere. However, the LSMs embedded in state-of-the-art climate models differ in how they represent fundamental aspects of the hydrological and carbon cycles, resulting in large inter-model differences and sometimes faulty predictions. These "third-generation" LSMs respect the close coupling of the carbon and water cycles through plants, but otherwise tend to be under-constrained, and have not taken full advantage of robust hydrological parameterizations that were independently developed in offline models. Benchmarking, combining multiple sources of atmospheric, biospheric and hydrological data, should be a required component of LSM development, but this field has been relatively poorly supported and intermittently pursued. Moreover, benchmarking alone is not sufficient to ensure that models improve. Increasing complexity may increase realism but decrease reliability and robustness, by increasing the number of poorly known model parameters. In contrast, simplifying the representation of complex processes by stochastic parameterization (the representation of unresolved processes by statistical distributions of values) has been shown to improve model reliability and realism in both atmospheric and land-surface modelling contexts. We provide ex les for important processes in hydrology (the generation of runoff and flow routing in heterogeneous catchments) and biology (carbon uptake by species- erse ecosystems). We propose that the way forward for next-generation complex LSMs will include: (a) representations of biological and hydrological processes based on the implementation of multiple internal constraints (b) systematic application of benchmarking and data assimilation techniques to optimize parameter values and thereby test the structural adequacy of models and (c) stochastic parameterization of unresolved variability, applied in both the hydrological and the biological domains.
Fast SVM Trained by Divide-and-Conquer Anchors
Publisher: International Joint Conferences on Artificial Intelligence Organization
Date: 08-2017
Abstract: Supporting vector machine (SVM) is the most frequently used classifier for machine learning tasks. However, its training time could become cumbersome when the size of training data is very large. Thus, many kinds of representative subsets are chosen from the original dataset to reduce the training complexity. In this paper, we propose to choose the representative points which are noted as anchors obtained from non-negative matrix factorization (NMF) in a ide-and-conquer framework, and then use the anchors to train an approximate SVM. Our theoretical analysis shows that the solving the DCA-SVM can yield an approximate solution close to the primal SVM. Experimental results on multiple datasets demonstrate that our DCA-SVM is faster than the state-of-the-art algorithms without notably decreasing the accuracy of classification results.
Multi-Positive and Unlabeled Learning
Publisher: International Joint Conferences on Artificial Intelligence Organization
Date: 08-2017
Abstract: The positive and unlabeled (PU) learning problem focuses on learning a classifier from positive and unlabeled data. Some methods have been developed to solve the PU learning problem. However, they are often limited in practical applications, since only binary classes are involved and cannot easily be adapted to multi-class data. Here we propose a one-step method that directly enables multi-class model to be trained using the given input multi-class data and that predicts the label based on the model decision. Specifically, we construct different convex loss functions for labeled and unlabeled data to learn a discriminant function F. The theoretical analysis on the generalization error bound shows that it is no worse than k√k times of the fully supervised multi-class classification methods when the size of the data in k classes is of the same order. Finally, our experimental results demonstrate the significance and effectiveness of the proposed algorithm in synthetic and real-world datasets.
Improving Adherence and Clinical Outcomes in Self-Guided Internet Treatment for Anxiety and Depression: Randomised Controlled Trial
Publisher: Public Library of Science (PLoS)
Date: 03-07-2013
Large sensitivity in land carbon storage due to geographical and temporal variation in the thermal response of photosynthetic capacity
Publisher: Wiley
Date: 10-04-2018
DOI: 10.1111/NPH.15100
An open trial of a brief transdiagnostic internet treatment for anxiety and depression
Publisher: Elsevier BV
Date: 12-2011
Forest productivity under climate change: A checklist for evaluating model studies
Publisher: Wiley
Date: 07-03-2011
DOI: 10.1002/WCC.108
Abstract: Climate change is highly likely to impact on forest productivity over the next century. The direction and magnitude of change are uncertain because many factors are changing simultaneously, such as atmospheric composition, temperature, rainfall, and land use. Simulation models have been widely used to estimate how these interacting factors might combine to alter forest productivity. Such studies have used many different types of models with different underlying assumptions. To evaluate predictions made by such studies, it is essential to understand the type of model and the assumptions used. In this article, we provide a checklist for use when evaluating modeled estimates of climate change impacts on forest productivity. The checklist highlights the assumptions that we believe are critical in determining model outcomes. Models are classified into different general types, and assumptions relating to effects of atmospheric CO 2 concentration, temperature, water availability, nutrient cycling, and disturbance are discussed. Our main aim is to provide a guide to enable correct interpretation of model projections. The article also challenges modelers to improve the quality of information provided about their model assumptions. WIREs Clim Change 2011 2 332–355 DOI: 10.1002/wcc.108 This article is categorized under: Assessing Impacts of Climate Change Evaluating Future Impacts of Climate Change
Carbon balance of coniferous forests growing in contrasting climates: Model-based analysis
Publisher: Elsevier BV
Date: 07-2005
Warming Reduces Net Carbon Gain and Productivity in Medicago sativa L. and Festuca arundinacea
Publisher: MDPI AG
Date: 19-10-2020
Abstract: High temperature stress imposes constraints on the productivity of agricultural systems, such as pastures, and predicted increases in global temperatures are set to exacerbate these limitations. Here, we sought to understand the impact of warmer growth temperature on gas exchange and net primary productivity for two widely cultivated pasture species. We grew a C3 legume, Medicago sativa (lucerne), and a C3 grass, Festuca arundinacea Schreb. (tall fescue), in a climate-controlled facility exposed to two temperature treatments (ambient: 26 °C, aT elevated: 30 °C, eT). Soil water was maintained at non-limiting conditions in both temperature treatments to control for the confounding effects of warming on soil moisture. We found that warming reduced photosynthetic capacity and increased leaf dark respiration (Rdark) in lucerne, while tall fescue showed little physiological change at the leaf level, but increased ecosystem respiration (Reco). Growth temperature had no significant impact on the thermal optimum of photosynthesis (Topt) or water use efficiency in either species. Both species exhibited significant reductions in productivity with warming lucerne had greater reductions in shoot biomass, while tall fescue had greater reductions in root biomass. Our results highlight the potential for significant declines in pasture productivity associated with even modest increases in average temperature and highlights the need for suitable management strategies and implementation of more heat-resistant cultivars. Improvements in photosynthetic performance for greater heat tolerance in lucerne, and traits associated with biomass allocation and root performance at higher temperatures in tall fescue, should be the focus for improving high temperature resistance in these plant species.
Trait versus situation-specific intolerance of uncertainty in a clinical sample with anxiety and depressive disorders
Publisher: Informa UK Limited
Date: 03-2012
Cost-Sensitive Feature Selection by Optimizing F-Measures
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 03-2018
A Transdiagnostic Examination of Intolerance of Uncertainty Across Anxiety and Depressive Disorders
Publisher: Informa UK Limited
Date: 09-2012
Mechanisms driving pre- and post-stressor repetitive negative thinking: Metacognitions, cognitive avoidance, and thought control
Publisher: Elsevier BV
Date: 03-2013
Biogeochemistry: Carbon dioxide and water use in forests
Publisher: Springer Science and Business Media LLC
Date: 07-2013
DOI: 10.1038/NATURE12411
Does physiological acclimation to climate warming stabilize the ratio of canopy respiration to photosynthesis?
Publisher: Wiley
Date: 28-04-2016
DOI: 10.1111/NPH.13978
Abstract: Given the contrasting short‐term temperature dependences of gross primary production (GPP) and autotrophic respiration, the fraction of GPP respired by trees is predicted to increase with warming, providing a positive feedback to climate change. However, physiological acclimation may d en or eliminate this response. We measured the fluxes of aboveground respiration ( R a ), GPP and their ratio ( R a /GPP) in large, field‐grown Eucalyptus tereticornis trees exposed to ambient or warmed air temperatures (+3°C). We report continuous measurements of whole‐canopy CO 2 exchange, direct temperature response curves of leaf and canopy respiration, leaf and branch wood respiration, and diurnal photosynthetic measurements. Warming reduced photosynthesis, whereas physiological acclimation prevented a coincident increase in R a . Ambient and warmed trees had a common nonlinear relationship between the fraction of GPP that was respired above ground ( R a /GPP) and the mean daily temperature. Thus, warming significantly increased R a /GPP by moving plants to higher positions on the shared R a /GPP vs daily temperature relationship, but this effect was modest and only notable during hot conditions. Despite the physiological acclimation of autotrophic respiration to warming, increases in temperature and the frequency of heat waves may modestly increase tree R a /GPP, contributing to a positive feedback between climate warming and atmospheric CO 2 accumulation.
Using ecosystem experiments to improve vegetation models
Publisher: Springer Science and Business Media LLC
Date: 21-05-2015
DOI: 10.1038/NCLIMATE2621
The multi-assumption architecture and testbed (MAAT v1.0): R code for generating ensembles with dynamic model structure and analysis of epistemic uncertainty from multiple sources
Publisher: Copernicus GmbH
Date: 10-08-2018
Abstract: Abstract. Computer models are ubiquitous tools used to represent systems across many scientific and engineering domains. For any given system, many computer models exist, each built on different assumptions and demonstrating variability in the ways in which these systems can be represented. This variability is known as epistemic uncertainty, i.e. uncertainty in our knowledge of how these systems operate. Two primary sources of epistemic uncertainty are (1) uncertain parameter values and (2) uncertain mathematical representations of the processes that comprise the system. Many formal methods exist to analyse parameter-based epistemic uncertainty, while process-representation-based epistemic uncertainty is often analysed post hoc, incompletely, informally, or is ignored. In this model description paper we present the multi-assumption architecture and testbed (MAAT v1.0) designed to formally and completely analyse process-representation-based epistemic uncertainty. MAAT is a modular modelling code that can simply and efficiently vary model structure (process representation), allowing for the generation and running of large model ensembles that vary in process representation, parameters, parameter values, and environmental conditions during a single execution of the code. MAAT v1.0 approaches epistemic uncertainty through sensitivity analysis, assigning variability in model output to processes (process representation and parameters) or to in idual parameters. In this model description paper we describe MAAT and, by using a simple groundwater model ex le, verify that the sensitivity analysis algorithms have been correctly implemented. The main system model currently coded in MAAT is a unified, leaf-scale enzyme kinetic model of C3 photosynthesis. In the Appendix we describe the photosynthesis model and the unification of multiple representations of photosynthetic processes. The numerical solution to leaf-scale photosynthesis is verified and ex les of process variability in temperature response functions are provided. For rapid application to new systems, the MAAT algorithms for efficient variation of model structure and sensitivity analysis are agnostic of the specific system model employed. Therefore MAAT provides a tool for the development of novel or toy models in many domains, i.e. not only photosynthesis, facilitating rapid informal and formal comparison of alternative modelling approaches.
Decadal biomass increment in early secondary succession woody ecosystems is increased by CO2 enrichment
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.
SERVE: Soft and Equalized Residual VEctors for image retrieval
Publisher: Elsevier BV
Date: 09-2016
Comparison of three models of alcohol craving in young adults: A cross-validation
Publisher: Wiley
Date: 25-03-2004
Limited Evidence of Cumulative Effects From Recurrent Droughts in Vegetation Responses to Australia's Millennium Drought
Publisher: American Geophysical Union (AGU)
Date: 05-2023
DOI: 10.1029/2022JG006818
Abstract: Drought‐induced vegetation declines have been reported across the globe and may have widespread implications for ecosystem composition, structure, and functions. Thus, it is critical to maximizing our understanding of how vegetation has responded to recent drought extremes. To date, most drought assessments emphasized the importance of drought intensity for vegetation responses. However, drought timing, duration, and repeat exposure all may be important aspects of ecosystem response with the potential for non‐linear effects. Cumulative effects are one such phenomenon, representing the additional decline due to repeated exposure to drought, and indicating gradual loss of ecosystem resistance. This study quantifies the frequency and magnitude of cumulative effects among Australian ecosystems as they responded to the Millennium Drought. Three distinct biophysical variables derived from satellite remote sensing were analyzed, including fraction of photosynthetically absorbed radiation, photosynthetic vegetation cover, and canopy density derived from passive microwave data. Cumulative effects were detected in only 8%–20% of the fire‐free landscape exposed to repeat or long‐duration drought, and could be a statistical artifact. In those limited cases, they approximately doubled drought impacts on leaf abundance, canopy cover, and vegetation density. Cultivated lands and grasslands were the most susceptible to cumulative effects, losing resistance to recurrent droughts, but could be false discovery. Despite being relatively infrequent in forests and savannas, cumulative effects caused larger additional declines in these ecosystems. Overall, our study demonstrates that repeated exposure appears to have limited influence on the magnitude of drought impacts on canopy structure affecting only a few areas.
Modelling forest response to increasing CO2 concentration under nutrient‐limited conditions
Publisher: Wiley
Date: 10-1994
Psychometric properties of the Repetitive Thinking Questionnaire in a clinical sample
Publisher: Elsevier BV
Date: 03-2012
Photosynthetic temperature responses of tree species in Rwanda: Evidence of pronounced negative effects of high temperature in montane rainforest climax species
Publisher: Wiley
Date: 05-02-2015
DOI: 10.1111/NPH.13291
Abstract: The sensitivity of photosynthetic metabolism to temperature has been identified as a key uncertainty for projecting the magnitude of the terrestrial feedback on future climate change. While temperature responses of photosynthetic capacities have been comparatively well investigated in temperate species, the responses of tropical tree species remain unexplored. We compared the responses of seedlings of native cold‐adapted tropical montane rainforest tree species with those of exotic warm‐adapted plantation species, all growing in an intermediate temperature common garden in Rwanda. Leaf gas exchange responses to carbon dioxide ( CO 2 ) at different temperatures (20–40°C) were used to assess the temperature responses of biochemical photosynthetic capacities. Analyses revealed a lower optimum temperature for photosynthetic electron transport rates than for Rubisco carboxylation rates, along with lower electron transport optima in the native cold‐adapted than in the exotic warm‐adapted species. The photosynthetic optimum temperatures were generally exceeded by daytime peak leaf temperatures, in particular in the native montane rainforest climax species. This study thus provides evidence of pronounced negative effects of high temperature in tropical trees and indicates high susceptibility of montane rainforest climax species to future global warming.
Reduced growth due to belowground sink limitation is not fully explained by reduced photosynthesis
Publisher: Oxford University Press (OUP)
Date: 04-04-2017
Abstract: Sink limitation is known to reduce plant growth, but it is not known how plant carbon (C) balance is affected, limiting our ability to predict growth under sink-limited conditions. We manipulated soil volume to impose sink limitation of growth in Eucalyptus tereticornis Sm. seedlings. Seedlings were grown in the field in containers of different sizes and planted flush to the soil alongside freely rooted (Free) seedlings. Container volume negatively affected aboveground growth throughout the experiment, and light saturated rates of leaf photosynthesis were consistently lower in seedlings in containers (-26%) compared with Free seedlings. Significant reductions in photosynthetic capacity in containerized seedlings were related to both reduced leaf nitrogen content and starch accumulation, indicating direct effects of sink limitation on photosynthetic downregulation. After 120 days, harvested biomass of Free seedlings was on average 84% higher than seedlings in containers, but biomass distribution in leaves, stems and roots was not different. However, the reduction in net leaf photosynthesis over the growth period was insufficient to explain the reduction in growth, so that we also observed an apparent reduction in whole-plant C-use efficiency (CUE) between Free seedlings and seedlings in containers. Our results show that sink limitation affects plant growth through feedbacks to both photosynthesis and CUE. Mass balance approaches to predicting plant growth under sink-limited conditions need to incorporate both of these feedbacks.
Perceptual Adversarial Networks for Image-to-Image Transformation
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2018
Co-optimal distribution of leaf nitrogen and hydraulic conductance in plant canopies
Publisher: Oxford University Press (OUP)
Date: 05-04-2012
Abstract: Leaf properties vary significantly within plant canopies, due to the strong gradient in light availability through the canopy, and the need for plants to use resources efficiently. At high light, photosynthesis is maximized when leaves have a high nitrogen content and water supply, whereas at low light leaves have a lower requirement for both nitrogen and water. Studies of the distribution of leaf nitrogen (N) within canopies have shown that, if water supply is ignored, the optimal distribution is that where N is proportional to light, but that the gradient of N in real canopies is shallower than the optimal distribution. We extend this work by considering the optimal co-allocation of nitrogen and water supply within plant canopies. We developed a simple 'toy' two-leaf canopy model and optimized the distribution of N and hydraulic conductance (K) between the two leaves. We asked whether hydraulic constraints to water supply can explain shallow N gradients in canopies. We found that the optimal N distribution within plant canopies is proportional to the light distribution only if hydraulic conductance, K, is also optimally distributed. The optimal distribution of K is that where K and N are both proportional to incident light, such that optimal K is highest to the upper canopy. If the plant is constrained in its ability to construct higher K to sun-exposed leaves, the optimal N distribution does not follow the gradient in light within canopies, but instead follows a shallower gradient. We therefore hypothesize that measured deviations from the predicted optimal distribution of N could be explained by constraints on the distribution of K within canopies. Further empirical research is required on the extent to which plants can construct optimal K distributions, and whether shallow within-canopy N distributions can be explained by sub-optimal K distributions.
Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data
Publisher: Wiley
Date: 15-08-2002
Do land surface models need to include differential plant species responses to drought? Examining model predictions across a latitudinal gradient in Europe
Publisher: Copernicus GmbH
Date: 06-08-2015
DOI: 10.5194/BGD-12-12349-2015
Abstract: Abstract. Future climate change has the potential to increase drought in many regions of the globe, making it essential that land surface models (LSMs) used in coupled climate models, realistically capture the drought responses of vegetation. Recent data syntheses show that drought sensitivity varies considerably among plants from different climate zones, but state-of-the-art LSMs currently assume the same drought sensitivity for all vegetation. We tested whether variable drought sensitivities are needed to explain the observed large-scale patterns of drought impact. We implemented data-driven drought sensitivities in the Community Atmosphere Biosphere Land Exchange (CABLE) LSM and evaluated alternative sensitivities across a latitudinal gradient in Europe during the 2003 heatwave. The model predicted an overly abrupt onset of drought unless average soil water potential was calculated with dynamic weighting across soil layers. We found that high drought sensitivity at the northernmost sites, and low drought sensitivity at the southernmost sites, was necessary to accurately model responses during drought. Our results indicate that LSMs will over-estimate drought impacts in drier climates unless different sensitivity of vegetation to drought is taken into account.
Multiview Vector-Valued Manifold Regularization for Multilabel Image Classification
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2013
Large-Margin Multi-ViewInformation Bottleneck
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 08-2014
A trait-based ecosystem model suggests that long-term responsiveness to rising atmospheric CO2 concentration is greater in slow-growing than fast-growing plants
Publisher: Wiley
Date: 07-06-2013
Developing an empirical model of canopy water flux describing the common response of transpiration to solar radiation and VPD across five contrasting woodlands and forests
Publisher: Wiley
Date: 13-04-2013
DOI: 10.1002/HYP.9280
The effect of comorbid substance use disorders on treatment outcome for anxiety disorders
Publisher: Elsevier BV
Date: 08-2008
Oscillatory behavior of two nonlinear microbial models of soil carbon decomposition
Publisher: Copernicus GmbH
Date: 07-04-2014
Abstract: Abstract. A number of nonlinear models have recently been proposed for simulating soil carbon decomposition. Their predictions of soil carbon responses to fresh litter input and warming differ significantly from conventional linear models. Using both stability analysis and numerical simulations, we showed that two of those nonlinear models (a two-pool model and a three-pool model) exhibit d ed oscillatory responses to small perturbations. Stability analysis showed the frequency of oscillation is proportional to √(& varepsilon −1−1) Ks/Vs in the two-pool model, and to √(& varepsilon −1−1) Kl/Vl in the three-pool model, where & varepsilon is microbial growth efficiency, Ks and Kl are the half saturation constants of soil and litter carbon, respectively, and /Vs and /Vl are the maximal rates of carbon decomposition per unit of microbial biomass for soil and litter carbon, respectively. For both models, the oscillation has a period of between 5 and 15 years depending on other parameter values, and has smaller litude at soil temperatures between 0 and 15 °C. In addition, the equilibrium pool sizes of litter or soil carbon are insensitive to carbon inputs in the nonlinear model, but are proportional to carbon input in the conventional linear model. Under warming, the microbial biomass and litter carbon pools simulated by the nonlinear models can increase or decrease, depending whether & varepsilon varies with temperature. In contrast, the conventional linear models always simulate a decrease in both microbial and litter carbon pools with warming. Based on the evidence available, we concluded that the oscillatory behavior and insensitivity of soil carbon to carbon input are notable features in these nonlinear models that are somewhat unrealistic. We recommend that a better model for capturing the soil carbon dynamics over decadal to centennial timescales would combine the sensitivity of the conventional models to carbon influx with the flexible response to warming of the nonlinear model.
Patterns of post‐drought recovery are strongly influenced by drought duration, frequency, post‐drought wetness, and bioclimatic setting
Publisher: Wiley
Date: 18-07-2021
DOI: 10.1111/GCB.15788
Abstract: Understanding vegetation recovery after drought is critical for projecting vegetation dynamics in future climates. From 1997 to 2009, Australia experienced a long‐lasting drought known as the Millennium Drought (MD), which led to widespread reductions in vegetation productivity. However, vegetation recovery post‐drought and its determinants remain unclear. This study leverages remote sensing products from different sources—fraction of absorbed photosynthetically active radiation (FPAR), based on optical data, and canopy density, derived from microwave data—and random forest algorithms to assess drought recovery over Australian natural vegetation during a 20‐year period centered on the MD. Post‐drought recovery was prevalent across the continent, with 6 out of 10 drought events seeing full recovery within about 6 months. Canopy density was slower to recover than leaf area seen in FPAR. The probability of full recovery was most strongly controlled by drought return interval, post‐drought hydrological condition, and drought length. Full recovery was seldom observed when drought events occurred at intervals of 3 months or less, and moderately dry (standardized water balance anomaly [SWBA] within [−1, −0.76]) post‐drought conditions resulted in less complete recovery than wet (SWBA 0.3) post‐drought conditions. Press droughts, which are long term but not extreme, delayed recovery more than pulse droughts (short term but extreme) and led to a higher frequency of persistent decline. Following press droughts, the frequency of persistent decline differed little among biome types but peaked in semi‐arid regions across aridity levels. Forests and savanna required the longest recovery times for press drought, while grasslands were the slowest to recover for pulse drought. This study provides quantitative thresholds that could be used to improve the modeling of ecosystem dynamics post‐drought.
One Stomatal Model to Rule Them All? Toward Improved Representation of Carbon and Water Exchange in Global Models
Publisher: American Geophysical Union (AGU)
Date: 04-2022
DOI: 10.1029/2021MS002761
Abstract: Stomatal conductance schemes that optimize with respect to photosynthetic and hydraulic functions have been proposed to address biases in land‐surface model (LSM) simulations during drought. However, systematic evaluations of both optimality‐based and alternative empirical formulations for coupling carbon and water fluxes are lacking. Here, we embed 12 empirical and optimization approaches within a LSM framework. We use theoretical model experiments to explore parameter identifiability and understand how model behaviors differ in response to abiotic changes. We also evaluate the models against leaf‐level observations of gas‐exchange and hydraulic variables, from xeric to wet forest/woody species spanning a mean annual precipitation range of 361–3,286 mm yr −1 . We find that models differ in how easily parameterized they are, due to: (a) poorly constrained optimality criteria (i.e., resulting in multiple solutions), (b) low influence parameters, (c) sensitivities to environmental drivers. In both the idealized experiments and compared to observations, sensitivities to variability in environmental drivers do not agree among models. Marked differences arise in sensitivities to soil moisture (soil water potential) and vapor pressure deficit. For ex le, stomatal closure rates at high vapor pressure deficit range between −45% and +70% of those observed. Although over half the new generation of stomatal schemes perform to a similar standard compared to observations of leaf‐gas exchange, two models do so through large biases in simulated leaf water potential (up to 11 MPa). Our results provide guidance for LSM development, by highlighting key areas in need for additional experimentation and theory, and by constraining currently viable stomatal hypotheses.
Whole-tree chambers for elevated atmospheric CO2 experimentation and tree scale flux measurements in south-eastern Australia: The Hawkesbury Forest Experiment
Publisher: Elsevier BV
Date: 15-07-2010
Biome-specific climatic space defined by temperature and precipitation predictability
Publisher: Wiley
Date: 24-09-2017
DOI: 10.1111/GEB.12635
Scaling KNN multi-class twin support vector machine via safe instance reduction
Publisher: Elsevier BV
Date: 05-2018
Privileged Matrix Factorization for Collaborative Filtering
Publisher: International Joint Conferences on Artificial Intelligence Organization
Date: 08-2017
Abstract: Collaborative filtering plays a crucial role in reducing excessive information in online consuming by suggesting products to customers that fulfil their potential interests. Observing that a user's review comments on purchases are often in companion with ratings, recent works exploit the review texts in representing user or item factors and have achieved prominent performance. Although effectiveness of reviews has been verified, one major defect of existing works is that reviews are used in justifying the learning of either user or item factors without noticing that each review associates a pair of user and item concurrently. To better explore the value of review comments, this paper presents the privileged matrix factorization method that utilize reviews in the learning of both user and item factors. By mapping review texts into the privileged feature space, a learned privileged function compensates the discrepancies between predicted ratings and groundtruth values rating-wisely. Thus by minimizing discrepancies and prediction errors, our method harnesses the information present in the review comments for the learning of both user and item factors. Experiments on five real datasets testify the effectiveness of the proposed method.
Collaborative Rating Allocation
Publisher: International Joint Conferences on Artificial Intelligence Organization
Date: 08-2017
Abstract: This paper studies the collaborative rating allocation problem, in which each user has limited ratings on all items. These users are termed ``energy limited''. Different from existing methods which treat each rating independently, we investigate the geometric properties of a user's rating vector, and design a matrix completion method on the simplex. In this method, a user's rating vector is estimated by the combination of user profiles as basis points on the simplex. Instead of using Euclidean metric, a non-linear pull-back distance measurement from the sphere is adopted since it can depict the geometric constraints on each user's rating vector. The resulting objective function is then efficiently optimized by a Riemannian conjugate gradient method on the simplex. Experiments on real-world data sets demonstrate our model's competitiveness versus other collaborative rating prediction methods.
Privileged Multi-label Learning
Publisher: International Joint Conferences on Artificial Intelligence Organization
Date: 08-2017
Abstract: This paper presents privileged multi-label learning (PrML) to explore and exploit the relationship between labels in multi-label learning problems. We suggest that for each in idual label, it cannot only be implicitly connected with other labels via the low-rank constraint over label predictors, but also its performance on ex les can receive the explicit comments from other labels together acting as an Oracle teacher. We generate privileged label feature for each ex le and its in idual label, and then integrate it into the framework of low-rank based multi-label learning. The proposed algorithm can therefore comprehensively explore and exploit label relationships by inheriting all the merits of privileged information and low-rank constraints. We show that PrML can be efficiently solved by dual coordinate descent algorithm using iterative optimization strategy with cheap updates. Experiments on benchmark datasets show that through privileged label features, the performance can be significantly improved and PrML is superior to several competing methods in most cases.
Paired comparison of water, energy and carbon exchanges over two young maritime pine stands (Pinus pinaster Ait.): Effects of thinning and weeding in the early stage of tree growth
Publisher: Oxford University Press (OUP)
Date: 30-06-2011
Abstract: The effects of management practices on energy, water and carbon exchanges were investigated in a young pine plantation in south-west France. In 2009-10, carbon dioxide (CO(2)), H(2)O and heat fluxes were monitored using the eddy covariance and sap flow techniques in a control plot (C) with a developed gorse layer, and an adjacent plot that was mechanically weeded and thinned (W). Despite large differences in the total leaf area index and canopy structure, the annual net radiation absorbed was only 4% lower in plot W. We showed that higher albedo in this plot was offset by lower emitted long-wave radiation. Annual evapotranspiration (ET) from plot W was 15% lower, due to lower rainfall interception and transpiration by the tree canopy, partly counterbalanced by the larger evaporation from both soil and regrowing weedy vegetation. The drainage belowground from plot W was larger by 113 mm annually. The seasonal variability of ET was driven by the dynamics of the soil and weed layers, which was more severely affected by drought in plot C. Conversely, the temporal changes in pine transpiration and stem diameter growth were synchronous between sites despite higher soil water content in the weeded plot. At the annual scale, both plots were carbon sinks, but thinning and weeding reduced the carbon uptake by 73%: annual carbon uptake was 243 and 65 g C m(-2) on plots C and W, respectively. Summer drought dramatically impacted the net ecosystem exchange: plot C became a carbon source as the gross primary production (GPP) severely decreased. However, plot W remained a carbon sink during drought, as a result of decreases in both GPP and ecosystem respiration (R(E)). In winter, both plots were carbon sources, plots C and W emitting 67.5 and 32.4 g C m(-2), respectively. Overall, this study highlighted the significant contribution of the gorse layer to mass and energy exchange in young pine plantations.
Stomatal optimization based on xylem hydraulics (SOX) improves land surface model simulation of vegetation responses to climate
Publisher: Wiley
Date: 17-02-2020
DOI: 10.1111/NPH.16419
Improving representation of photosynthesis in Earth System Models
Publisher: Wiley
Date: 26-08-2014
DOI: 10.1111/NPH.12972
Towards a more physiological representation of vegetation phosphorus processes in land surface models
Publisher: Wiley
Date: 19-02-2021
DOI: 10.1111/NPH.15688
Abstract: Contents Summary 1223 I. Introduction 1223 II. Photosynthesis and respiration 1224 III. Biomass growth 1224 IV. Carbon allocation 1225 V. Plant internal P redistribution 1226 VI. Plant P uptake 1227 VII. Conclusion 1227 Acknowledgements 1228 References 1228 SUMMARY: Our ability to understand the effect of nutrient limitation on ecosystem productivity is key to the prediction of future terrestrial carbon storage. Significant progress has been made to include phosphorus (P) cycle processes in land surface models (LSMs), but these efforts are focused on the soil component of the P cycle. Incorporating the soil component is important to estimate plant-available P, but does not necessarily address the vegetation response to P limitation or plant-soil interactions. A more detailed representation of plant P processes is needed to link nutrient availability and ecosystem productivity. We review physiological and biochemical evidence for vegetation responses to P availability, and recommend ways to move towards a more physiological representation of vegetation P processes in LSMs.
A novel optimization approach incorporating non-stomatal limitations predicts stomatal behaviour in species from six plant functional types
Publisher: Oxford University Press (OUP)
Date: 04-02-2019
DOI: 10.1093/JXB/ERZ020
Drought tolerance traits do not vary across sites differing in water availability in Banksia serrata (Proteaceae)
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/FP18238
Abstract: Interspecific variation in plant hydraulic traits plays a major role in shaping species distributions across climates, yet variation within species is poorly understood. Here we report on intraspecific variation of hydraulic traits in Banksia serrata (L.f.) s led from three sites characterised by contrasting climates (warm-wet, warm-dry and cool-wet). Hydraulic characteristics including vulnerability to embolism, hydraulic conductance, pressure-volume traits and key morphological traits were measured. Vulnerability to embolism in leaf and stem, defined by the water potential inducing 50 and 88% loss of hydraulic conductivity (P50 and P88 respectively), did not differ across sites. However, plants from the warm-dry environment exhibited higher stem conductivity (Ks) than the cool-wet environment. Leaf turgor loss point (TLP) did not vary among sites, but warm-dry site plants showed lower leaf capacitance (C*FT) and higher modulus of elasticity (ε) than the other two sites. Plants from the cool-wet site had lower specific leaf area (SLA) and plants from the warm-dry site had lower sapwood density (WD). Overall, key hydraulic traits were generally conserved across populations despite differences in mean site water availability, and the safety-efficiency trade-off was absent in this species. These results suggest that B. serrata has limited ability to adjust hydraulic architecture in response to environmental change and thus may be susceptible to climate change-type drought stress.
Retraction Note: A constraint on historic growth in global photosynthesis due to increasing CO2
Publisher: Springer Science and Business Media LLC
Date: 30-05-2022
Increased light-use efficiency sustains net primary productivity of shaded coffee plants in agroforestry system
Publisher: Wiley
Date: 20-06-2017
DOI: 10.1111/PCE.12964
Abstract: In agroforestry systems, shade trees strongly affect the physiology of the undergrown crop. However, a major paradigm is that the reduction in absorbed photosynthetically active radiation is, to a certain extent, compensated by an increase in light-use efficiency, thereby reducing the difference in net primary productivity between shaded and non-shaded plants. Due to the large spatial heterogeneity in agroforestry systems and the lack of appropriate tools, the combined effects of such variables have seldom been analysed, even though they may help understand physiological processes underlying yield dynamics. In this study, we monitored net primary productivity, during two years, on scales ranging from in idual coffee plants to the entire plot. Absorbed radiation was mapped with a 3D model (MAESPA). Light-use efficiency and net assimilation rate were derived for each coffee plant in idually. We found that although irradiance was reduced by 60% below crowns of shade trees, coffee light-use efficiency increased by 50%, leaving net primary productivity fairly stable across all shade levels. Variability of aboveground net primary productivity of coffee plants was caused primarily by the age of the plants and by intraspecific competition among them (drivers usually overlooked in the agroforestry literature) rather than by the presence of shade trees.
Drought × CO2 interactions in trees: A test of the low-intercellular CO2 concentration (Ci ) mechanism
Publisher: Wiley
Date: 03-11-2016
DOI: 10.1111/NPH.13715
Abstract: Models of tree responses to climate typically project that elevated atmospheric CO 2 concentration ( e C a ) will reduce drought impacts on forests. We tested one of the mechanisms underlying this interaction, the ‘low C i effect’, in which stomatal closure in drought conditions reduces the intercellular CO 2 concentration ( C i ), resulting in a larger relative enhancement of photosynthesis with e C a , and, consequently, a larger relative biomass response. We grew two Eucalyptus species of contrasting drought tolerance at ambient and elevated C a for 6–9 months in large pots maintained at 50% (drought) and 100% field capacity. Droughted plants did not have significantly lower C i than well‐watered plants, which we attributed to long‐term changes in leaf area. Hence, there should not have been an interaction between e C a and water availability on biomass, and we did not detect one. The xeric species did have higher C i than the mesic species, indicating lower water‐use efficiency, but both species exhibited similar responses of photosynthesis and biomass to e C a , owing to compensatory differences in the photosynthetic response to C i . Our results demonstrate that long‐term acclimation to drought, and coordination among species traits may be important for predicting plant responses to e C a under low water availability.
Large-margin multi-view Gaussian process
Publisher: Springer Science and Business Media LLC
Date: 23-05-2014
Rooting depth explains [CO 2 ]× drought interaction in Eucalyptus saligna
Publisher: Oxford University Press (OUP)
Date: 12-05-2011
Abstract: Elevated atmospheric [CO(2)] (eC(a)) often decreases stomatal conductance, which may delay the start of drought, as well as alleviate the effect of dry soil on plant water use and carbon uptake. We studied the interaction between drought and eC(a) in a whole-tree chamber experiment with Eucalyptus saligna. Trees were grown for 18 months in their C(a) treatments before a 4-month dry-down. Trees grown in eC(a) were smaller than those grown in ambient C(a) (aC(a)) due to an early growth setback that was maintained throughout the duration of the experiment. Pre-dawn leaf water potentials were not different between C(a) treatments, but were lower in the drought treatment than the irrigated control. Counter to expectations, the drought treatment caused a larger reduction in canopy-average transpiration rates for trees in the eC(a) treatment compared with aC(a). Total tree transpiration over the dry-down was positively correlated with the decrease in soil water storage, measured in the top 1.5 m, over the drying cycle however, we could not close the water budget especially for the larger trees, suggesting soil water uptake below 1.5 m depth. Using neutron probe soil water measurements, we estimated fractional water uptake to a depth of 4.5 m and found that larger trees were able to extract more water from deep soil layers. These results highlight the interaction between rooting depth and response of tree water use to drought. The responses of tree water use to eC(a) involve interactions between tree size, root distribution and soil moisture availability that may override the expected direct effects of eC(a). It is essential that these interactions be considered when interpreting experimental results.
A unifying conceptual model for the environmental responses of isoprene emissions from plants
Publisher: Oxford University Press (OUP)
Date: 19-09-2013
DOI: 10.1093/AOB/MCT206
Changes in intolerance of uncertainty during cognitive behavior group therapy for social phobia
Publisher: Elsevier BV
Date: 06-2012
RETRACTED ARTICLE: A constraint on historic growth in global photosynthesis due to increasing CO2
Publisher: Springer Science and Business Media LLC
Date: 08-12-2021
DOI: 10.1038/S41586-021-04096-9
Abstract: The global terrestrial carbon sink is increasing
Multi-View Learning With Incomplete Views
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2015
Analytical Clustering score with application to post-placement multi-bit flip-flop merging
Publisher: ACM
Date: 29-03-2015
Modelling forest-growth response to increasing CO2 concentration in relation to various factors affecting nutrient supply
Publisher: Wiley
Date: 1998
The optimal stomatal response to atmospheric CO2 concentration: Alternative solutions, alternative interpretations
Publisher: Elsevier BV
Date: 12-2013
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The University Of Edinburgh
Location: United Kingdom of Great Britain and Northern Ireland
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