ORCID Profile
0000-0002-5721-1656
Current Organisation
University of Cape Town
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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)
Ecological Applications | Photogrammetry and Remote Sensing | Natural Resource Management | Terrestrial Ecology | Ecological Impacts of Climate Change | Ecosystem Function | Ecological Physiology
ANZSRC Socio-Economic Objective (SEO)
Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Ecosystem Adaptation to Climate Change | Ecosystem Assessment and Management of Forest and Woodlands Environments | Environmentally Sustainable Plant Production not elsewhere classified | Natural Hazards in Forest and Woodlands Environments |
Related Links
Publications
Does circadian regulation lead to optimal gas exchange regulation?
Publisher: Cold Spring Harbor Laboratory
Date: 06-06-2017
DOI: 10.1101/121368
Abstract: Optimal stomatal theory is an evolutionary model proposing that leaves trade-off Carbon (C) for water to maximise C assimilation ( A ) and minimise transpiration ( E ), thereby generating a marginal water cost of carbon gain (λ) that remains constant over short temporal scales. The circadian clock is a molecular timer of metabolism that controls A and stomatal conductance ( g s ), amongst other processes, in a broad array of plant species. Here, we test whether circadian regulation contributes towards achieving optimal stomatal behaviour. We subjected bean ( Phaseolus vulgaris ) and cotton ( Gossypium hirsutum ) canopies to fixed, continuous environmental conditions of photosynthetically active radiation, temperature and vapour pressure deficit over 48 hours. We observed a significant and self-sustained circadian oscillation in A and in stomatal conductance ( g s ) which also led to a circadian oscillation in λ . The lack of constant marginal water cost indicates that circadian regulation does not directly lead to optimal stomatal behaviour. However, the temporal pattern in gas exchange, indicative of either maximizing A or of minimizing E , depending upon time of day, indicates that circadian regulation could contribute towards optimizing stomatal responses. More broadly, our results add to the emerging field of plant circadian ecology and show that molecular controls may partially explain leaf-level patterns observed in the field.
Understorey productivity in temperate grassy woodland responds to soil water availability but not to elevated [CO2 ]
Publisher: Wiley
Date: 14-02-2018
DOI: 10.1111/GCB.14038
Abstract: Rising atmospheric [CO
Genetic variation in circadian regulation of nocturnal stomatal conductance enhances carbon assimilation and growth
Publisher: Wiley
Date: 19-09-2015
DOI: 10.1111/PCE.12598
Abstract: Circadian resonance, whereby a plant's endogenous rhythms are tuned to match environmental cues, has been repeatedly shown to be adaptive, although the underlying mechanisms remain elusive. Concomitantly, the adaptive value of nocturnal transpiration in C3 plants remains unknown because it occurs without carbon assimilation. These seemingly unrelated processes are interconnected because circadian regulation drives temporal patterns in nocturnal stomatal conductance, with maximum values occurring immediately before dawn for many species. We grew in iduals of six Eucalyptus camaldulensis genotypes in naturally lit glasshouses and measured sunset, predawn and midday leaf gas exchange and whole-plant biomass production. We tested whether sunrise anticipation by the circadian clock and subsequent increases in genotype predawn stomatal conductance led to rapid stomatal opening upon illumination, ultimately affecting genotype differences in carbon assimilation and growth. We observed faster stomatal responses to light inputs at sunrise in genotypes with higher predawn stomatal conductance. Moreover, early morning and midday stomatal conductance and carbon assimilation, leaf area and total plant biomass were all positively correlated with predawn stomatal conductance across genotypes. Our results lead to the novel hypothesis that genotypic variation in the circadian-regulated capacity to anticipate sunrise could be an important factor underlying intraspecific variation in tree growth.
Limits to post‐fire vegetation recovery under climate change
Publisher: Wiley
Date: 16-09-2021
DOI: 10.1111/PCE.14176
Abstract: Record‐breaking fire seasons in many regions across the globe raise important questions about plant community responses to shifting fire regimes (i.e., changing fire frequency, severity and seasonality). Here, we examine the impacts of climate‐driven shifts in fire regimes on vegetation communities, and likely responses to fire coinciding with severe drought, heatwaves and/or insect outbreaks. We present scenario‐based conceptual models on how overlapping disturbance events and shifting fire regimes interact differently to limit post‐fire resprouting and recruitment capacity. We demonstrate that, although many communities will remain resilient to changing fire regimes in the short‐term, longer‐term changes to vegetation structure, demography and species composition are likely, with a range of subsequent effects on ecosystem function. Resprouting species are likely to be most resilient to changing fire regimes. However, even these species are susceptible if exposed to repeated short‐interval fire in combination with other stressors. Post‐fire recruitment is highly vulnerable to increased fire frequency, particularly as climatic limitations on propagule availability intensify. Prediction of community responses to fire under climate change will be greatly improved by addressing knowledge gaps on how overlapping disturbances and climate change‐induced shifts in fire regime affect post‐fire resprouting, recruitment, growth rates, and species‐level adaptation capacity.
Author Correction: The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data
Publisher: Springer Science and Business Media LLC
Date: 25-02-2021
DOI: 10.1038/S41597-021-00851-9
Abstract: A Correction to this paper has been published: 0.1038/s41597-021-00851-9.
Optimal stomatal behaviour around the world
Publisher: Springer Science and Business Media LLC
Date: 02-03-2015
DOI: 10.1038/NCLIMATE2550
Circadian rhythms have significant effects on leaf-to-canopy scale gas exchange under field conditions
Publisher: Oxford University Press (OUP)
Date: 20-10-2016
Testing the limits of plant drought stress and subsequent recovery in four provenances of a widely distributed subtropical tree species
Publisher: Wiley
Date: 14-01-2022
DOI: 10.1111/PCE.14254
Abstract: Drought‐induced tree mortality may increase with ongoing climate change. Unraveling the links between stem hydraulics and mortality thresholds, and the effects of intraspecific variation, remain important unresolved issues. We conducted a water manipulation experiment in a rain‐out shelter, using four provenances of Schima superba originating from a gradient of annual precipitation (1124–1796 mm) and temperature (16.4–22.4°C). Seedlings were droughted to three levels of percentage loss of hydraulic conductivity (i.e., P 50 , P 88 and P 99) and subsequently rewatered to field capacity for 30 days traits related to water and carbon relations were measured. The lethal water potential associated with incipient mortality was between P 50 and P 88 . Seedlings exhibited similar drought responses in xylem water potential, hydraulic conductivity and gas exchange. Upon rehydration, patterns of gas exchange differed among provenances but were not related to the climate at the origin. The four provenances exhibited a similar degree of stem hydraulic recovery, which was correlated with the magnitude of antecedent drought and stem soluble sugar at the end of the drought. Results suggest that there were intraspecific differences in the capacity of S. superba seedlings for carbon assimilation during recovery, indicating a decoupling between gas exchange recovery and stem hydraulics across provenances.
Leaf vein density enhances vascular redundancy instead of carbon uptake at the expense of increasing water leaks in oaks
Publisher: Elsevier BV
Date: 08-2021
Woody plants optimise stomatal behaviour relative to hydraulic risk
Publisher: Wiley
Date: 23-04-2018
DOI: 10.1111/ELE.12962
Abstract: Stomatal response to environmental conditions forms the backbone of all ecosystem and carbon cycle models, but is largely based on empirical relationships. Evolutionary theories of stomatal behaviour are critical for guarding against prediction errors of empirical models under future climates. Longstanding theory holds that stomata maximise fitness by acting to maintain constant marginal water use efficiency over a given time horizon, but a recent evolutionary theory proposes that stomata instead maximise carbon gain minus carbon costs/risk of hydraulic damage. Using data from 34 species that span global forest biomes, we find that the recent carbon-maximisation optimisation theory is widely supported, revealing that the evolution of stomatal regulation has not been primarily driven by attainment of constant marginal water use efficiency. Optimal control of stomata to manage hydraulic risk is likely to have significant consequences for ecosystem fluxes during drought, which is critical given projected intensification of the global hydrological cycle.
An introduction to the Australian and New Zealand flux tower network – OzFlux
Publisher: Copernicus GmbH
Date: 31-10-2016
Abstract: Abstract. OzFlux is the regional Australian and New Zealand flux tower network that aims to provide a continental-scale national research facility to monitor and assess trends, and improve predictions, of Australia's terrestrial biosphere and climate. This paper describes the evolution, design, and current status of OzFlux as well as provides an overview of data processing. We analyse measurements from all sites within the Australian portion of the OzFlux network and two sites from New Zealand. The response of the Australian biomes to climate was largely consistent with global studies except that Australian systems had a lower ecosystem water-use efficiency. Australian semi-arid/arid ecosystems are important because of their huge extent (70 %) and they have evolved with common moisture limitations. We also found that Australian ecosystems had a similar radiation-use efficiency per unit leaf area compared to global values that indicates a convergence toward a similar biochemical efficiency. The two New Zealand sites represented extremes in productivity for a moist temperate climate zone, with the grazed dairy farm site having the highest GPP of any OzFlux site (2620 gC m−2 yr−1) and the natural raised peat bog site having a very low GPP (820 gC m−2 yr−1). The paper discusses the utility of the flux data and the synergies between flux, remote sensing, and modelling. Lastly, the paper looks ahead at the future direction of the network and concludes that there has been a substantial contribution by OzFlux, and considerable opportunities remain to further advance our understanding of ecosystem response to disturbances, including drought, fire, land-use and land-cover change, land management, and climate change, which are relevant both nationally and internationally. It is suggested that a synergistic approach is required to address all of the spatial, ecological, human, and cultural challenges of managing the delicately balanced ecosystems in Australasia.
Endogenous circadian rhythms in pigment composition induce changes in photochemical efficiency in plant canopies
Publisher: Wiley
Date: 30-03-2017
DOI: 10.1111/PCE.12909
Abstract: There is increasing evidence that the circadian clock is a significant driver of photosynthesis that becomes apparent when environmental cues are experimentally held constant. We studied whether the composition of photosynthetic pigments is under circadian regulation, and whether pigment oscillations lead to rhythmic changes in photochemical efficiency. To address these questions, we maintained canopies of bean and cotton, after an entrainment phase, under constant (light or darkness) conditions for 30-48 h. Photosynthesis and quantum yield peaked at subjective noon, and non-photochemical quenching peaked at night. These oscillations were not associated with parallel changes in carbohydrate content or xanthophyll cycle activity. We observed robust oscillations of Chl a/b during constant light in both species, and also under constant darkness in bean, peaking when it would have been night during the entrainment (subjective nights). These oscillations could be attributed to the synthesis and/or degradation of trimeric light-harvesting complex II (reflected by the rhythmic changes in Chl a/b), with the antenna size minimal at night and maximal around subjective noon. Considering together the oscillations of pigments and photochemistry, the observed pattern of changes is counterintuitive if we assume that the plant strategy is to avoid photodamage, but consistent with a strategy where non-stressed plants maximize photosynthesis.
Integrating plant physiology into simulation of fire behavior and effects
Publisher: Wiley
Date: 14-02-2023
DOI: 10.1111/NPH.18770
Abstract: Wildfires are a global crisis, but current fire models fail to capture vegetation response to changing climate. With drought and elevated temperature increasing the importance of vegetation dynamics to fire behavior, and the advent of next generation models capable of capturing increasingly complex physical processes, we provide a renewed focus on representation of woody vegetation in fire models. Currently, the most advanced representations of fire behavior and biophysical fire effects are found in distinct classes of fine‐scale models and do not capture variation in live fuel (i.e. living plant) properties. We demonstrate that plant water and carbon dynamics, which influence combustion and heat transfer into the plant and often dictate plant survival, provide the mechanistic linkage between fire behavior and effects. Our conceptual framework linking remotely sensed estimates of plant water and carbon to fine‐scale models of fire behavior and effects could be a critical first step toward improving the fidelity of the coarse scale models that are now relied upon for global fire forecasting. This process‐based approach will be essential to capturing the influence of physiological responses to drought and warming on live fuel conditions, strengthening the science needed to guide fire managers in an uncertain future.
Supplementary material to "A hydroclimatic model for the distribution of fire on Earth"
Publisher: Copernicus GmbH
Date: 25-11-2019
Effects of a Heat Wave on Nocturnal Stomatal Conductance in Eucalyptus camaldulensis
Publisher: MDPI AG
Date: 03-06-2018
DOI: 10.3390/F9060319
A hydroclimatic model for the distribution of fire on Earth
Publisher: IOP Publishing
Date: 03-2021
Abstract: The distribution of fire on Earth has been monitored from space for several decades, yet the geography of global fire regimes has proven difficult to reproduce from interactions of climate, vegetation, terrain, land use and other human activities by empirical and process-based fire models. Here, we propose a simple, yet robust, model for the global distribution of fire potential based on fundamental biophysical constraints controlling fire activity in all biomes. In our ‘top-down’ approach we ignored the dynamics of in idual fires and focus on capturing hydroclimatic constraints on the production and (seasonal) desiccation of fuels to predict the potential mean annual fractional burned area at 0.25° spatial resolution, here estimated by the 0.99 quantile of the observed mean annual fractional burned area ( F 0.99 ) over the 1995-2016 period of the Global Fire Emissions Database (GFED4). We show that 80% of the global variation in F 0.99 can be explained from a combination of mean annual precipitation and potential evapotranspiration. The proposed hydroclimatic model reproduced observed 0.99 quantile fire activity levels equally well across all biomes and provided the first objective underpinning for the dichotomy of global fire regimes in two domains characterised by either fuel production limitations on fire or fuel dryness limitations on fire. A sharp transition between the two climate-fire domains was found to occur at a mean annual aridity index of 1.9 (1.94 ± 0.02). Our model provides a simple but comprehensive basis for predicting fire potential under current and future climates, as well as an overarching framework for estimating effects of human activity via ignition regimes and manipulation of vegetation.
Effects of competition and herbivory over woody seedling growth in a temperate woodland trump the effects of elevated CO2
Publisher: Springer Science and Business Media LLC
Date: 27-04-2018
DOI: 10.1007/S00442-018-4143-1
Abstract: A trend of increasing woody plant density, or woody thickening, has been observed across grassland and woodland ecosystems globally. It has been proposed that increasing atmospheric [CO
A semi-mechanistic model for predicting daily variations in species-level live fuel moisture content
Publisher: Elsevier BV
Date: 08-2022
Utilizing intraspecific variation in phenotypic plasticity to bolster agricultural and forest productivity under climate change
Publisher: Wiley
Date: 09-2014
DOI: 10.1111/PCE.12424
Abstract: Climate change threatens the ability of agriculture and forestry to meet growing global demands for food, fibre and wood products. Information gathered from genotype-by-environment interactions (G × E), which demonstrate intraspecific variation in phenotypic plasticity (the ability of a genotype to alter its phenotype in response to environmental change), may prove important for bolstering agricultural and forest productivity under climate change. Nonetheless, very few studies have explicitly quantified genotype plasticity-productivity relationships in agriculture or forestry. Here, we conceptualize the importance of intraspecific variation in agricultural and forest species plasticity, and discuss the physiological and genetic factors contributing to intraspecific variation in phenotypic plasticity. Our discussion highlights the need for an integrated understanding of the mechanisms of G × E, more extensive assessments of genotypic responses to climate change under field conditions, and explicit testing of genotype plasticity-productivity relationships. Ultimately, further investigation of intraspecific variation in phenotypic plasticity in agriculture and forestry may prove important for identifying genotypes capable of increasing or sustaining productivity under more extreme climatic conditions.
Photosynthesis and carbon allocation are both important predictors of genotype productivity responses to elevated CO2 in Eucalyptus camaldulensis
Publisher: Oxford University Press (OUP)
Date: 08-05-2018
Abstract: Intraspecific variation in biomass production responses to elevated atmospheric carbon dioxide (eCO2) could influence tree species' ecological and evolutionary responses to climate change. However, the physiological mechanisms underlying genotypic variation in responsiveness to eCO2 remain poorly understood. In this study, we grew 17 Eucalyptus camaldulensis Dehnh. subsp. camaldulensis genotypes (representing provenances from four different climates) under ambient atmospheric CO2 and eCO2. We tested whether genotype leaf-scale photosynthetic and whole-tree carbon (C) allocation responses to eCO2 were predictive of genotype biomass production responses to eCO2. Averaged across genotypes, growth at eCO2 increased in situ leaf net photosynthesis (Anet) (29%) and leaf starch concentrations (37%). Growth at eCO2 reduced the maximum carboxylation capacity of Rubisco (-4%) and leaf nitrogen per unit area (Narea, -6%), but Narea calculated on a total non-structural carbohydrate-free basis was similar between treatments. Growth at eCO2 also increased biomass production and altered C allocation by reducing leaf area ratio (-11%) and stem mass fraction (SMF, -9%), and increasing leaf mass area (18%) and leaf mass fraction (5%). Overall, we found few significant CO2 × provenance or CO2 × genotype (within provenance) interactions. However, genotypes that showed the largest increases in total dry mass at eCO2 had larger increases in root mass fraction (with larger decreases in SMF) and photosynthetic nitrogen-use efficiency (PNUE) with CO2 enrichment. These results indicate that genetic differences in PNUE and carbon sink utilization (in roots) are both important predictors of tree productivity responsiveness to eCO2.
Fire activity as measured by burned area reveals weak effects of ENSO in China
Publisher: Springer Science and Business Media LLC
Date: 28-07-2022
A broader perspective on the causes and consequences of eastern Australia's 2019–20 season of mega-fires: A response to Adams et al
Publisher: Wiley
Date: 28-05-2020
DOI: 10.1111/GCB.15111
Predicting dead fine fuel moisture at regional scales using vapour pressure deficit from MODIS and gridded weather data
Publisher: Elsevier BV
Date: 03-2016
A semi-mechanistic model for predicting the moisture content of fine litter
Publisher: Elsevier BV
Date: 04-2015
Cover Image
Publisher: Wiley
Date: 22-10-2021
DOI: 10.1111/PCE.14201
Abstract: The cover image is based on the Invited Review Limits to post‐fire vegetation recovery under climate change by Rachael H. Nolan et al., 0.1111 ce.14176 . image
Causes and consequences of eastern Australia's 2019–20 season of mega‐fires
Publisher: Wiley
Date: 22-01-2020
DOI: 10.1111/GCB.14987
Abstract: See Letter to the Editor on this article by Adam et al ., 26, 3756–3758 . See also Response to the Letter by Bradstock et al ., 26, e8–e9 .
Termite sensitivity to temperature affects global wood decay rates
Publisher: American Association for the Advancement of Science (AAAS)
Date: 28-09-2022
Abstract: Deadwood is a large global carbon store with its store size partially determined by biotic decay. Microbial wood decay rates are known to respond to changing temperature and precipitation. Termites are also important decomposers in the tropics but are less well studied. An understanding of their climate sensitivities is needed to estimate climate change effects on wood carbon pools. Using data from 133 sites spanning six continents, we found that termite wood discovery and consumption were highly sensitive to temperature (with decay increasing .8 times per 10°C increase in temperature)—even more so than microbes. Termite decay effects were greatest in tropical seasonal forests, tropical savannas, and subtropical deserts. With tropicalization (i.e., warming shifts to tropical climates), termite wood decay will likely increase as termites access more of Earth’s surface.
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.
Narrating the polyphonic city translation and identity in translingual/transcultural writing
Publisher: Routledge
Date: 23-08-2017
Intraspecific variation in juvenile tree growth under elevated CO2alone and with O3: a meta-analysis
Publisher: Oxford University Press (OUP)
Date: 15-04-2016
Abstract: Atmospheric carbon dioxide (CO2) concentrations are expected to increase throughout this century, potentially fostering tree growth. A wealth of studies have examined the variation in CO2 responses across tree species, but the extent of intraspecific variation in response to elevated CO2 (eCO2) has, so far, been examined in in idual studies and syntheses of published work are currently lacking. We conducted a meta-analysis on the effects of eCO2 on tree growth (height, stem biomass and stem volume) and photosynthesis across genotypes to examine whether there is genetic variation in growth responses to eCO2 and to understand their dependence on photosynthesis. We additionally examined the interaction between the responses to eCO2 and ozone (O3), another global change agent. Most of the published studies so far have been conducted in juveniles and in Populus spp., although the patterns observed were not species dependent. All but one study reported significant genetic variation in stem biomass, and the magnitude of intraspecific variation in response to eCO2 was similar in magnitude to previous analyses on interspecific variation. Growth at eCO2 was predictable from growth at ambient CO2 (R(2) = 0.60), and relative rankings of genotype performance were preserved across CO2 levels, indicating no significant interaction between genotypic and environmental effects. The growth response to eCO2 was not correlated with the response of photosynthesis (P > 0.1), and while we observed 57.7% average increases in leaf photosynthesis, stem biomass and volume increased by 36 and 38.5%, respectively, and height only increased by 9.5%, suggesting a predominant role for carbon allocation in ultimately driving the response to eCO2 Finally, best-performing genotypes under eCO2 also responded better under eCO2 and elevated O3 Further research needs include widening the study of intraspecific variation beyond the genus Populus and examining the interaction between eCO2 and other environmental stressors. We conclude that significant potential to foster CO2-induced productivity gains through tree breeding exists, that these programs could be based upon best-performing genotypes under ambient conditions and that they would benefit from an increased understanding on the controls of allocation.
Future changes in climatic water balance determine potential for transformational shifts in Australian fire regimes
Publisher: IOP Publishing
Date: 06-2016
An introduction to the Australian and New Zealand flux tower network – OzFlux
Publisher: Copernicus GmbH
Date: 28-04-2016
DOI: 10.5194/BG-2016-152
Abstract: Abstract. OzFlux is the regional Australian and New Zealand flux tower network that aims to provide a continental-scale national research facility to monitor and assess trends, and improve predictions, of Australia’s terrestrial biosphere and climate. This paper describes the evolution, design and current status of OzFlux as well as an overview of data processing. We analyse measurements from the Australian portion of the OzFlux network and found that the response of Australian biomes to climate was largely consistent with global studies but that Australian systems had a lower ecosystem water-use efficiency. Australian semi-arid/arid ecosystems are important because of their huge extent (70 %) and they have evolved with common moisture limitations. We also found that Australian ecosystems had similar radiation use efficiency per unit leaf area compared to global values that indicates a convergence toward a similar biochemical efficiency. The paper discusses the utility of the flux data and the synergies between flux, remote sensing and modelling. Lastly, the paper looks ahead at the future direction of the network and concludes that there has been a substantial contribution by OzFlux and considerable opportunities remain to further advance our understanding of ecosystem response to disturbances including drought, fire, land use and land cover change, land management and climate change that are relevant both nationally and internationally. It is suggested that a synergistic approach is required to address all of the spatial, ecological, human and cultural challenges of managing the delicately balanced ecosystems in Australia.
Root relative water content is a potential signal for impending mortality of a subtropical conifer during extreme drought stress
Publisher: Wiley
Date: 12-06-2023
DOI: 10.1111/PCE.14639
Abstract: Adaptation to future climates characterized by more frequent severe droughts requires enhanced mechanistic understanding of tree mortality. However, our knowledge of the physiological limits to withstand extreme drought, and how the coordination between water and carbon traits enhances survival, is still limited. Potted seedlings of Pinus massoniana were dehydrated to three target droughts (percentage loss of stem hydraulic conductivity of ca. 50%, 85%, and 100% PLC 50 , PLC 85 and PLC 100 ) and then relieved from these target droughts by fully rewatering. Predawn and midday water potentials (Ψ), relative water content (RWC), PLC and nonstructural carbohydrates (NSC) were monitored. During drought, Ψ and RWC declined as PLC increased. Root RWC declined more rapidly than other organ RWCs, particularly after PLC 50 stress. All organ NSC concentrations were above predrought values. During rewatering, water trait recovery declined as drought increased, with no mortality at PLC 50 but 75% mortality at PLC 85 . The observed stem hydraulic recovery at PLC 50 following rewatering was not correlated to NSC dynamics. Collectively, our results highlighted the primary role of hydraulic failure in Pinus massoniana seedling mortality by assessing mortality threshold and links among water status and water supply. Root RWC can be considered as a potential warning signal of P. massoniana mortality.
Author Correction: Globe-LFMC, a global plant water status database for vegetation ecophysiology and wildfire applications
Publisher: Springer Science and Business Media LLC
Date: 29-11-2019
DOI: 10.1038/S41597-019-0315-Z
Abstract: An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Leaf photosynthetic, economics and hydraulic traits are decoupled among genotypes of a widespread species of eucalypt grown under ambient and elevated CO 2
Publisher: Wiley
Date: 27-04-2016
The 2019/20 eastern Australian mega forest fires - a global forest perspective
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-15693
Abstract: & & The 2019/20 forest fires in eastern Australia burned over 5.8 million hectares of mainly temperate broadleaf forest between September 2019 and January 2020. This burned area figure is expected to rise over the remainder of the austral summer, but is already an order of magnitude larger than the mean annual burned area for Australian forest fires over the last 20 years, which is ~0.59 Mha per year. Here we show that this forest fire event is of a record-breaking scale, both nationally and globally, and was pre-conditioned by wide-spread prolonged drought and extreme heat.& & & & We analysed global remotely sensed burned area data for 2000-2019 to estimate annual burned area fractions of all continental forest biomes. The annual burned area fraction, which is related to the length of fire intervals and other aspects of fire regimes, allows us to compare levels of fire activity across different forest biomes and continents.& & & & Though very large fires occur in some forest biomes, such as the boreal forests of North-America and Asia, over the 20 years covered by our data set, annual burned area fractions have been very small (& .03) for nearly all continental forest biomes including Australia& #8217 s temperate broadleaf forest biome. These findings provide a global historical reference for the interpretation of the scale of the 2019/20 eastern Australian mega forest fires.& & & & With fire activity in all forest biomes strongly constrained by the moisture content of the fuels, explanations for the unconstrained burning of millions of hectares of temperate broadleaf forest in a single season must be sought in the extreme drought that has affected eastern Australia for the last two years. We use gridded daily soil moisture predictions for the continent to show how widespread and prolonged dryness set the stage for the unprecedented forest fire event of 2019/20.& &
Relationships between climate of origin and photosynthetic responses to an episodic heatwave depend on growth CO2 concentration for Eucalyptus camaldulensis var. camaldulensis
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/FP17077
Abstract: Stressful episodic weather is likely to affect the C balance of trees as the climate changes, potentially altering survival. However, the role of elevated CO2 concentration ([CO2]) in tolerating off-season episodic extremes is not clear. We tested for interactive effects of elevated CO2 and springtime heat stress on photosynthesis for seven genotypes of Eucalyptus camaldulensis Dehnh. var. camaldulensis, representing its widespread distribution across south-eastern Australia. We grew clonal material under glasshouse conditions of ambient (aCO2 400 parts per million (ppm)) or elevated (eCO2 640 ppm) [CO2], and air temperatures of 25 : 17°C (day : night), and measured the electron transport rate in PSII (ETR), stomatal conductance to water vapour (gs) and net CO2 assimilation (A). Measurements were made before, during and after a four-day temperature excursion of 35 : 27°C. ETR and A were ~17% higher for plants grown in eCO2 than in aCO2. Photosynthesis remained stable for plants in eCO2 during the heatwave. Based on the effect size ratio (eCO2 : aCO2), gs and ETR were temporarily affected more by the heatwave than A. A reduction in ETR in eCO2 was the only lasting effect of the heatwave. There were no significant differences among genotypes. Correlations between photosynthesis and climate of origin differed for plants grown in aCO2 compared with eCO2, suggesting potential complex and multiple control points on photosynthesis.
Temperature sensitivity of termites determines global wood decay rates
Publisher: Research Square Platform LLC
Date: 11-01-2022
DOI: 10.21203/RS.3.RS-1242094/V1
Abstract: Animals, such as termites, have largely been overlooked as global-scale drivers of biogeochemical cycles 1,2 , despite site-specific findings 3,4 . Deadwood turnover, an important component of the carbon cycle, is driven by multiple decay agents. Studies have focused on temperate systems 5,6 , where microbes dominate decay 7 . Microbial decay is sensitive to temperature, typically doubling per 10°C increase (decay effective Q 10 = ~2) 8–10 . Termites are important decayers in tropical systems 3,11–13 and differ from microbes in their population dynamics, dispersal, and substrate discovery 14–16 , meaning their climate sensitivities also differ. Using a network of 133 sites spanning 6 continents, we report the first global field-based quantification of temperature and precipitation sensitivities for termites and microbes, providing novel understandings of their response to changing climates. Temperature sensitivity of microbial decay was within previous estimates. Termite discovery and consumption were both much more sensitive to temperature (decay effective Q 10 = 6.53), leading to striking differences in deadwood turnover in areas with and without termites. Termite impacts were greatest in tropical seasonal forests and savannas and subtropical deserts. With tropicalization 17 (i.e., warming shifts to a tropical climate), the termite contribution to global wood decay will increase as more of the earth’s surface becomes accessible to termites.
A hydroclimatic model for the distribution of fire on Earth
Publisher: Copernicus GmbH
Date: 25-11-2019
DOI: 10.5194/BG-2019-441
Abstract: Abstract. The distribution of fire on Earth has been monitored from space for several decades, yet the geography of global fire regimes has proven difficult to reproduce from interactions of climate, vegetation, terrain and land use by empirical and process-based fire models. Here, we propose a simple, yet robust, model for global fire potential based on fundamental biophysical constraints controlling fire activity in all biomes. In our top-down approach we ignored the dynamics of in idual fires and focus on capturing hydroclimatic constraints on the production and (seasonal) desiccation of fuels to predict the potential mean annual fractional burned area, here estimated by the 0.99 percentile of the observed mean annual fractional burned area (F0.99). We show that 80 % of the global variation in F0.99 can be explained from a combination of mean annual precipitation and potential evapotranspiration. The proposed hydroclimatic model reproduced observed fire activity levels equally well across all biomes and provided the first objective underpinning for the dichotomy of global fire regimes in two domains characterised by either fuel production limitations on fire or fuel dryness limitations on fire. A sharp transition between the two climate-fire domains was found to occur at a mean annual aridity index of 1.9 (1.94 ± 0.02). Our model provides a simple but comprehensive basis for predicting fire potential under current and future climates, as well as an overarching framework for estimating effects of human activity via ignition regimes and manipulation of vegetation.
Linking Forest Flammability and Plant Vulnerability to Drought
Publisher: MDPI AG
Date: 20-07-2020
DOI: 10.3390/F11070779
Abstract: Globally, fire regimes are being altered by changing climatic conditions. New fire regimes have the potential to drive species extinctions and cause ecosystem state changes, with a range of consequences for ecosystem services. Despite the co-occurrence of forest fires with drought, current approaches to modelling flammability largely overlook the large body of research into plant vulnerability to drought. Here, we outline the mechanisms through which plant responses to drought may affect forest flammability, specifically fuel moisture and the ratio of dead to live fuels. We present a framework for modelling live fuel moisture content (moisture content of foliage and twigs) from soil water content and plant traits, including rooting patterns and leaf traits such as the turgor loss point, osmotic potential, elasticity and leaf mass per area. We also present evidence that physiological drought stress may contribute to previously observed fuel moisture thresholds in south-eastern Australia. Of particular relevance is leaf cavitation and subsequent shedding, which transforms live fuels into dead fuels, which are drier, and thus easier to ignite. We suggest that capitalising on drought research to inform wildfire research presents a major opportunity to develop new insights into wildfires, and new predictive models of seasonal fuel dynamics.
Hydraulic and photosynthetic limitations prevail over root non‐structural carbohydrate reserves as drivers of resprouting in two Mediterranean oaks
Publisher: Wiley
Date: 16-06-2020
DOI: 10.1111/PCE.13781
Large-scale, dynamic transformations in fuel moisture drive wildfire activity across southeastern Australia
Publisher: American Geophysical Union (AGU)
Date: 06-05-2016
DOI: 10.1002/2016GL068614
Fire-induced deforestation in drought-prone Mediterranean forests: Drivers and unknowns from leaves to communities
Publisher: Wiley
Date: 22-01-2018
DOI: 10.1002/ECM.1285
Assessing the potential functions of nocturnal stomatal conductance in C
Publisher: Wiley
Date: 22-05-2019
DOI: 10.1111/NPH.15881
Abstract: Nocturnal stomatal conductance contributes to water loss at night without carbon gain in C
Drivers of nocturnal stomatal conductance in C3 and C4 plants
Publisher: Elsevier BV
Date: 03-2022
DOI: 10.1016/J.SCITOTENV.2021.151952
Abstract: Nocturnal water losses were for long considered negligible, but it is now known that incomplete stomatal closure during the night leads to significant water losses at leaf, plant and ecosystem scales. However, only daytime transpiration is currently accounted for in evapotranspiration studies. Important uncertainties on the drivers of nocturnal water fluxes hinder its incorporation within modelling frameworks because some studies indicate that night-time stomatal drivers may differ from day-time responses. Here, we synthesise the studies on nocturnal stomatal conductance (g
The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data
Publisher: Springer Science and Business Media LLC
Date: 09-07-2020
DOI: 10.1038/S41597-020-0534-3
Abstract: The FLUXNET2015 dataset provides ecosystem-scale data on CO 2 , water, and energy exchange between the biosphere and the atmosphere, and other meteorological and biological measurements, from 212 sites around the globe (over 1500 site-years, up to and including year 2014). These sites, independently managed and operated, voluntarily contributed their data to create global datasets. Data were quality controlled and processed using uniform methods, to improve consistency and intercomparability across sites. The dataset is already being used in a number of applications, including ecophysiology studies, remote sensing studies, and development of ecosystem and Earth system models. FLUXNET2015 includes derived-data products, such as gap-filled time series, ecosystem respiration and photosynthetic uptake estimates, estimation of uncertainties, and metadata about the measurements, presented for the first time in this paper. In addition, 206 of these sites are for the first time distributed under a Creative Commons (CC-BY 4.0) license. This paper details this enhanced dataset and the processing methods, now made available as open-source codes, making the dataset more accessible, transparent, and reproducible.
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.
Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the ‘Angry Summer’ of 2012/2013
Publisher: Copernicus GmbH
Date: 03-06-2016
DOI: 10.5194/BG-2016-183
Abstract: Abstract. As a result of climate change warmer temperatures are projected through the 21st century and are already increasing above modelled predictions. Apart from increases in the mean, warm/hot temperature extremes are expected to become more prevalent in the future, along with an increase in the frequency of droughts. It is crucial to better understand the response of terrestrial ecosystems to such temperature extremes for predicting land-surface feedbacks in a changing climate. During the 2012/2013 summer, Australia experienced a record-breaking heat wave with an exceptional spatial extent that lasted for several weeks. We synthesized eddy-covariance measurements from seven woodland and forest sites across climate zones in southern Australia, which we combined with model simulations from the CABLE land surface model to investigate the effect of this summer heat wave on the carbon and water exchange of terrestrial ecosystems. We found that the water-limited woodlands and the energy-limited forest ecosystem responded differently to the heat wave. During the most intense part of the heat wave, the woodlands experienced decreased latent heat flux, an increased Bowen ratio and a reduced carbon uptake while the forest ecosystem had increased latent heat flux, reduced Bowen ratio and increased carbon uptake. Ecosystem respiration was increased at all sites resulting in reduced net ecosystem productivity in the woodlands and constant net ecosystem productivity in the forest. Importantly all ecosystems remained carbon sinks during the event. Precipitation after the most intense first part of the heat wave and slightly cooler temperatures led to a decrease of the Bowen ratio and hence increased evaporative cooling. Carbon uptake in the woodlands also recovered quickly but respiration remained high. While woodlands and forest proved relatively resistant to this short-term heat extreme these carbon sinks may not sustainable in a future with an increased number, intensity and duration of heat waves.
Invasive forb benefits from water savings by native plants and carbon fertilization under elevated CO 2 and warming
Publisher: Wiley
Date: 23-08-2013
DOI: 10.1111/NPH.12459
Abstract: As global changes reorganize plant communities, invasive plants may benefit. We hypothesized that elevated CO 2 and warming would strongly influence invasive species success in a semi‐arid grassland, as a result of both direct and water‐mediated indirect effects. To test this hypothesis, we transplanted the invasive forb L inaria dalmatica into mixed‐grass prairie treated with free‐air CO 2 enrichment and infrared warming, and followed survival, growth, and reproduction over 4 yr. We also measured leaf gas exchange and carbon isotopic composition in L . dalmatica and the dominant native C 3 grass P ascopyrum smithii . CO 2 enrichment increased L . dalmatica biomass 13‐fold, seed production 32‐fold, and clonal expansion seven‐fold, while warming had little effect on L . dalmatica biomass or reproduction. Elevated CO 2 decreased stomatal conductance in P . smithii , contributing to higher soil water, but not in L . dalmatica . Elevated CO 2 also strongly increased L . dalmatica photosynthesis (87% versus 23% in P . smithii ), as a result of both enhanced carbon supply and increased soil water. More broadly, rapid growth and less conservative water use may allow invasive species to take advantage of both carbon fertilization and water savings under elevated CO 2 . Water‐limited ecosystems may therefore be particularly vulnerable to invasion as CO 2 increases.
Circadian Regulation Does Not Optimize Stomatal Behaviour
Publisher: MDPI AG
Date: 25-08-2020
Abstract: The circadian clock is a molecular timer of metabolism that affects the diurnal pattern of stomatal conductance (gs), amongst other processes, in a broad array of plant species. The function of circadian gs regulation remains unknown and here, we test whether circadian regulation helps to optimize diurnal variations in stomatal conductance. We subjected bean (Phaseolus vulgaris) and cotton (Gossypium hirsutum) canopies to fixed, continuous environmental conditions of photosynthetically active radiation, temperature, and vapour pressure deficit (free-running conditions) over 48 h. We modelled gs variations in free-running conditions to test for two possible optimizations of stomatal behaviour under circadian regulation: (i) that stomata operate to maintain constant marginal water use efficiency or (ii) that stomata maximize C net gain minus the costs or risks of hydraulic damage. We observed that both optimization models predicted gs poorly under free-running conditions, indicating that circadian regulation does not directly lead to stomatal optimization. We also demonstrate that failure to account for circadian variation in gs could potentially lead to biased parameter estimates during calibrations of stomatal models. More broadly, our results add to the emerging field of plant circadian ecology, where circadian controls may partially explain leaf-level patterns observed in the field.
Supplementary material to "Upside-down fluxes Down Under: CO<sub>2</sub> net sink in winter and net source in summer in a temperate evergreen broadleaf forest"
Publisher: Copernicus GmbH
Date: 02-01-2018
Upside-down fluxes Down Under: CO<sub>2</sub> net sink in winter and net source in summer in a temperate evergreen broadleaf forest
Publisher: Copernicus GmbH
Date: 02-01-2018
DOI: 10.5194/BG-2017-526
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 characterized 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 three-year study, the ecosystem was a small sink in 2014 (54 g C m−2 y−1), a stronger sink in 2015 (183 g C m−2 y−1) and even stronger sink in 2016 (337 g C m−2 y−1), but these variations were not related to precipitation. 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 correlated with canopy leaf area index (LAI) (r2 = 0.24), 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 drought and high temperature, and ecosystem respiration could be enhanced by rising temperature, our results suggest the potential for large-scale seasonal shifts in NEE in sclerophyll vegetation under climate change.
Circadian rhythms regulate the environmental responses of net CO2 exchange in bean and cotton canopies
Publisher: Elsevier BV
Date: 05-2017
Forest fire threatens global carbon sinks and population centres under rising atmospheric water demand
Publisher: Springer Science and Business Media LLC
Date: 22-11-2022
DOI: 10.1038/S41467-022-34966-3
Abstract: Levels of fire activity and severity that are unprecedented in the instrumental record have recently been observed in forested regions around the world. Using a large s le of daily fire events and hourly climate data, here we show that fire activity in all global forest biomes responds strongly and predictably to exceedance of thresholds in atmospheric water demand, as measured by maximum daily vapour pressure deficit. The climatology of vapour pressure deficit can therefore be reliably used to predict forest fire risk under projected future climates. We find that climate change is projected to lead to widespread increases in risk, with at least 30 additional days above critical thresholds for fire activity in forest biomes on every continent by 2100 under rising emissions scenarios. Escalating forest fire risk threatens catastrophic carbon losses in the Amazon and major population health impacts from wildfire smoke in south Asia and east Africa.
Soil phosphorous and endogenous rhythms exert a larger impact than CO 2 or temperature on nocturnal stomatal conductance in Eucalyptus tereticornis
Publisher: Oxford University Press (OUP)
Date: 11-2013
Abstract: High nocturnal transpiration rates (5-15% of total water loss in terrestrial plants) may be adaptive under limited fertility, by increasing nutrient uptake or transport via transpiration-induced mass flow, but the response of stomata in the dark to environmental variables is poorly understood. Here we tested the impact of soil phosphorous (P) concentration, atmospheric CO2 concentration and air temperature on stomatal conductance (gs) during early and late periods in the night, as well as at midday in naturally, sun-lit glasshouse-grown Eucalyptus tereticornis Sm. seedlings. Soil P was the main driver of nocturnal gs, which was consistently higher in low soil P (37.3-79.9 mmol m(-2) s(-1)) than in high soil P (17.7-49.3 mmol m(-2)(-1)). Elevated temperature had only a marginal (P = 0.07) effect on gs early in the night (gs decreased from 34.7 to 25.8 mmol m(-2) s(-1) with an increase in temperature of 4 °C). The effect of CO2 depended on its interaction with temperature. Stomatal conductance responses to soil P were apparently driven by indirect effects of soil P on plant anatomy, since gs was significantly and negatively correlated with wood density. However, the relationship of gs with environmental factors became weaker late in the night, relative to early in the night, likely due to apparent endogenous processes gs late in the night was two times larger than gs observed early in the night. Time-dependent controls over nocturnal gs suggest that daytime stomatal models may not apply during the night, and that different types of regulation may occur even within a single night. We conclude that the enhancement of nocturnal gs under low soil P availability is unlikely to be adaptive in our species because of the relatively small amount of transpiration-induced mass flow that can be achieved through rates of nocturnal water loss (3-6% of daytime mass flow).
Plant water potential improves prediction of empirical stomatal models
Publisher: Public Library of Science (PLoS)
Date: 12-10-2017
Changing Weather Extremes Call for Early Warning of Potential for Catastrophic Fire
Publisher: American Geophysical Union (AGU)
Date: 12-2017
DOI: 10.1002/2017EF000657
Climate change induced declines in fuel moisture may turn currently fire-free Pyrenean mountain forests into fire-prone ecosystems
Publisher: Elsevier BV
Date: 11-2021
Woody clockworks: circadian regulation of night‐time water use in E ucalyptus globulus
Publisher: Wiley
Date: 25-06-2013
DOI: 10.1111/NPH.12382
Abstract: The role of the circadian clock in controlling the metabolism of entire trees has seldom been considered. We tested whether the clock influences nocturnal whole‐tree water use. Whole‐tree chambers allowed the control of environmental variables (temperature, relative humidity). Night‐time stomatal conductance ( g s ) and sap flow ( Q ) were monitored in 6‐ to 8‐m‐tall E ucalyptus globulus trees during nights when environmental variables were kept constant, and also when conditions varied with time. Artificial neural networks were used to quantify the relative importance of circadian regulation of g s and Q . Under a constant environment, g s and Q declined from 0 to 6 h after dusk, but increased from 6 to 12 h after dusk. While the initial decline could be attributed to multiple processes, the subsequent increase is most consistent with circadian regulation of g s and Q . We conclude that endogenous regulation of g s is an important driver of night‐time Q under natural environmental variability. The proportion of nocturnal Q variation associated with circadian regulation (23–56%) was comparable to that attributed to vapor pressure deficit variation (25–58%). This study contributes to our understanding of the linkages between molecular and cellular processes related to circadian regulation, and whole‐tree processes related to ecosystem gas exchange in the field.
Globe-LFMC, a global plant water status database for vegetation ecophysiology and wildfire applications
Publisher: Springer Science and Business Media LLC
Date: 21-08-2019
DOI: 10.1038/S41597-019-0164-9
Abstract: Globe-LFMC is an extensive global database of live fuel moisture content (LFMC) measured from 1,383 s ling sites in 11 countries: Argentina, Australia, China, France, Italy, Senegal, Spain, South Africa, Tunisia, United Kingdom and the United States of America. The database contains 161,717 in idual records based on in situ destructive s les used to measure LFMC, representing the amount of water in plant leaves per unit of dry matter. The primary goal of the database is to calibrate and validate remote sensing algorithms used to predict LFMC. However, this database is also relevant for the calibration and validation of dynamic global vegetation models, eco-physiological models of plant water stress as well as understanding the physiological drivers of spatiotemporal variation in LFMC at local, regional and global scales. Globe-LFMC should be useful for studying LFMC trends in response to environmental change and LFMC influence on wildfire occurrence, wildfire behavior, and overall vegetation health.
Climate and stomatal traits drive covariation in nighttime stomatal conductance and daytime gas exchange rates in a widespread C4 grass
Publisher: Wiley
Date: 04-11-2020
DOI: 10.1111/NPH.16987
Unprecedented burn area of Australian mega forest fires
Publisher: Springer Science and Business Media LLC
Date: 24-02-2020
Convergence in critical fuel moisture and fire weather thresholds associated with fire activity in the pyroregions of Mediterranean Europe
Publisher: Elsevier BV
Date: 02-2022
DOI: 10.1016/J.SCITOTENV.2021.151462
Abstract: Wildfires are becoming an increasing threat to many communities worldwide. There has been substantial progress towards understanding the proximal causes of increased fire activity in recent years at regional and national scales. However, subcontinental scale examinations of the commonalities and differences in the drivers of fire activity across different regions are rare in the Mediterranean zone of the European Union (EUMed). Here, we first develop a new classification of EUMed pyroregions, based on grouping different ecoregions with similar seasonal patterns of burned area. We then examine the thresholds associated with fire activity in response to different drivers related to fuel moisture, surface meteorology and atmospheric stability. We document an overarching role for variation in dead fuel moisture content (FM
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.
Night and day – Circadian regulation of night-time dark respiration and light-enhanced dark respiration in plant leaves and canopies
Publisher: Elsevier BV
Date: 05-2017
Carbon uptake and water use in woodlands and forests in southern Australia during an extreme heat wave event in the angry Summer of 2012/2013
Publisher: Copernicus GmbH
Date: 11-2016
Abstract: Abstract. As a result of climate change warmer temperatures are projected through the 21st century and are already increasing above modelled predictions. Apart from increases in the mean, warm/hot temperature extremes are expected to become more prevalent in the future, along with an increase in the frequency of droughts. It is crucial to better understand the response of terrestrial ecosystems to such temperature extremes for predicting land-surface feedbacks in a changing climate. While land-surface feedbacks in drought conditions and during heat waves have been reported from Europe and the US, direct observations of the impact of such extremes on the carbon and water cycles in Australia have been lacking. During the 2012/2013 summer, Australia experienced a record-breaking heat wave with an exceptional spatial extent that lasted for several weeks. In this study we synthesised eddy-covariance measurements from seven woodlands and one forest site across three biogeographic regions in southern Australia. These observations were combined with model results from BIOS2 (Haverd et al., 2013a, b) to investigate the effect of the summer heat wave on the carbon and water exchange of terrestrial ecosystems which are known for their resilience toward hot and dry conditions. We found that water-limited woodland and energy-limited forest ecosystems responded differently to the heat wave. During the most intense part of the heat wave, the woodlands experienced decreased latent heat flux (23 % of background value), increased Bowen ratio (154 %) and reduced carbon uptake (60 %). At the same time the forest ecosystem showed increased latent heat flux (151 %), reduced Bowen ratio (19 %) and increased carbon uptake (112 %). Higher temperatures caused increased ecosystem respiration at all sites (up to 139 %). During daytime all ecosystems remained carbon sinks, but carbon uptake was reduced in magnitude. The number of hours during which the ecosystem acted as a carbon sink was also reduced, which switched the woodlands into a carbon source on a daily average. Precipitation occurred after the first, most intense part of the heat wave, and the subsequent cooler temperatures in the temperate woodlands led to recovery of the carbon sink, decreased the Bowen ratio (65 %) and hence increased evaporative cooling. Gross primary productivity in the woodlands recovered quickly with precipitation and cooler temperatures but respiration remained high. While the forest proved relatively resilient to this short-term heat extreme the response of the woodlands is the first direct evidence that the carbon sinks of large areas of Australia may not be sustainable in a future climate with an increased number, intensity and duration of heat waves.
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Discovery Projects - Grant ID: DP130102576
Start Date: 04-2013
End Date: 03-2017
Amount: $405,000.00
Funder: Australian Research Council
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Start Date: 10-2020
End Date: 10-2024
Amount: $524,027.00
Funder: Australian Research Council
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