Publications by authors named "Claire M Belcher"

21 Publications

  • Page 1 of 1

The rise of angiosperms strengthened fire feedbacks and improved the regulation of atmospheric oxygen.

Nat Commun 2021 01 21;12(1):503. Epub 2021 Jan 21.

Global System Institute, University of Exeter, Exeter, EX4 4QE, UK.

The source of oxygen to Earth's atmosphere is organic carbon burial, whilst the main sink is oxidative weathering of fossil carbon. However, this sink is to insensitive to counteract oxygen rising above its current level of about 21%. Biogeochemical models suggest that wildfires provide an additional regulatory feedback mechanism. However, none have considered how the evolution of different plant groups through time have interacted with this feedback. The Cretaceous Period saw not only super-ambient levels of atmospheric oxygen but also the evolution of the angiosperms, that then rose to dominate Earth's ecosystems. Here we show, using the COPSE biogeochemical model, that angiosperm-driven alteration of fire feedbacks likely lowered atmospheric oxygen levels from ~30% to 25% by the end of the Cretaceous. This likely set the stage for the emergence of closed-canopy angiosperm tropical rainforests that we suggest would not have been possible without angiosperm enhancement of fire feedbacks.
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http://dx.doi.org/10.1038/s41467-020-20772-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820256PMC
January 2021

Publisher Correction: Impaired photosynthesis and increased leaf construction costs may induce floral stress during episodes of global warming over macroevolutionary timescales.

Sci Rep 2018 May 31;8(1):8661. Epub 2018 May 31.

The Italian National Research Council - Tree and Timber Institute (CNR-IVALSA), Via Madonna del Piano 10, Sesto Fiorentino, 50019, Florence, Italy.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
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http://dx.doi.org/10.1038/s41598-018-26883-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6044228PMC
May 2018

Impaired photosynthesis and increased leaf construction costs may induce floral stress during episodes of global warming over macroevolutionary timescales.

Sci Rep 2018 04 18;8(1):6206. Epub 2018 Apr 18.

The Italian National Research Council - Tree and Timber Institute (CNR-IVALSA) Via Madonna del Piano 10, Sesto Fiorentino, 50019, Florence, Italy.

Global warming events have coincided with turnover of plant species at intervals in Earth history. As mean global temperatures rise, the number, frequency and duration of heat-waves will increase. Ginkgo biloba was grown under controlled climatic conditions at two different day/night temperature regimes (25/20 °C and 35/30 °C) to investigate the impact of heat stress. Photosynthetic CO-uptake and electron transport were reduced at the higher temperature, while rates of respiration were greater; suggesting that the carbon balance of the leaves was adversely affected. Stomatal conductance and the potential for evaporative cooling of the leaves was reduced at the higher temperature. Furthermore, the capacity of the leaves to dissipate excess energy was also reduced at 35/30 °C, indicating that photo-protective mechanisms were no longer functioning effectively. Leaf economics were adversely affected by heat stress, exhibiting an increase in leaf mass per area and leaf construction costs. This may be consistent with the selective pressures experienced by fossil Ginkgoales during intervals of global warming such as the Triassic - Jurassic boundary or Early Eocene Climatic Optimum. The physiological and morphological responses of the G. biloba leaves were closely interrelated; these relationships may be used to infer the leaf economics and photosynthetic/stress physiology of fossil plants.
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http://dx.doi.org/10.1038/s41598-018-24459-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6049339PMC
April 2018

Charcoal evidence that rising atmospheric oxygen terminated Early Jurassic ocean anoxia.

Nat Commun 2017 05 12;8:15018. Epub 2017 May 12.

wildFIRE Lab, Hatherly Laboratories, University of Exeter, Prince of Wales Road, England, Exeter EX4 4PS, UK.

The Toarcian Oceanic Anoxic Event (T-OAE) was characterized by a major disturbance to the global carbon(C)-cycle, and depleted oxygen in Earth's oceans resulting in marine mass extinction. Numerical models predict that increased organic carbon burial should drive a rise in atmospheric oxygen (pO) leading to termination of an OAE after ∼1 Myr. Wildfire is highly responsive to changes in pO implying that fire-activity should vary across OAEs. Here we test this hypothesis by tracing variations in the abundance of fossil charcoal across the T-OAE. We report a sustained ∼800 kyr enhancement of fire-activity beginning ∼1 Myr after the onset of the T-OAE and peaking during its termination. This major enhancement of fire occurred across the timescale of predicted pO variations, and we argue this was primarily driven by increased pO. Our study provides the first fossil-based evidence suggesting that fire-feedbacks to rising pO may have aided in terminating the T-OAE.
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http://dx.doi.org/10.1038/ncomms15018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5437290PMC
May 2017

Changes to Cretaceous surface fire behaviour influenced the spread of the early angiosperms.

New Phytol 2017 Feb 7;213(3):1521-1532. Epub 2016 Nov 7.

wildFIRE Lab, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter, EX4 4PS, UK.

Angiosperms evolved and diversified during the Cretaceous period. Early angiosperms were short-stature weedy plants thought to have increased fire frequency and mortality in gymnosperm forest, aiding their own expansion. However, no explorations have considered whether the range of novel fuel types that diversified throughout the Cretaceous also altered fire behaviour, which should link more strongly to mortality than fire frequency alone. We measured ignitability and heat of combustion in analogue Cretaceous understorey fuels (conifer litter, ferns, weedy and shrubby angiosperms) and used these data to model palaeofire behaviour. Variations in ignition, driven by weedy angiosperms alone, were found to have been a less important feedback to changes in Cretaceous fire activity than previously estimated. Our model estimates suggest that fires in shrub and fern understories had significantly greater fireline intensities than those fuelled by conifer litter or weedy angiosperms, and whilst fern understories supported the most rapid fire spread, angiosperm shrubs delivered the largest amount of heat per unit area. The higher fireline intensities predicted by the models led to estimates of enhanced scorch of the gymnosperm canopy and a greater chance of transitioning to crown fires. Therefore, changes in fire behaviour driven by the addition of new Cretaceous fuel groups may have assisted the angiosperm expansion.
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http://dx.doi.org/10.1111/nph.14264DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5245107PMC
February 2017

The influence of leaf morphology on litter flammability and its utility for interpreting palaeofire.

Authors:
Claire M Belcher

Philos Trans R Soc Lond B Biol Sci 2016 06;371(1696)

wildFIRE Lab, Hatherly Laboratories, University of Exeter, Prince of Wales Road, Exeter EX4 4PS, UK

Studies of palaeofire rely on quantifying the abundance of fossil charcoals in sediments to estimate changes in fire activity. However, gaining an understanding of the behaviour of palaeofires is also essential if we are to determine the palaeoecological impact of wildfires. Here, I use experimental approaches to explore relationships between litter fire behaviour and leaf traits that are observable in the fossil record. Fire calorimetry was used to assess the flammability of 15 species of conifer litter and indicated that leaf morphology related to litter bulk density and fuel load that determined the duration of burning and the total energy released. These data were applied to a fossil case study that couples estimates of palaeolitter fire behaviour to charcoal-based estimates of fire activity and observations of palaeoecological changes. The case study reveals that significant changes in fire activity and behaviour likely fed back to determine ecosystem composition. This work highlights that we can recognize and measure plant traits in the fossil record that relate to fire behaviour and therefore that further research is warranted towards estimating palaeofire behaviour as it can enhance our ability to interpret the palaeoecological impact of palaeofires throughout Earth's long evolutionary history.This article is part of the themed issue 'The interaction of fire and mankind'.
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http://dx.doi.org/10.1098/rstb.2015.0163DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874401PMC
June 2016

The interaction of fire and mankind: Introduction.

Philos Trans R Soc Lond B Biol Sci 2016 06;371(1696)

Department of Anthropology, Southern Methodist University, Dallas, TX 75275-0336, USA.

Fire has been an important part of the Earth system for over 350 Myr. Humans evolved in this fiery world and are the only animals to have used and controlled fire. The interaction of mankind with fire is a complex one, with both positive and negative aspects. Humans have long used fire for heating, cooking, landscape management and agriculture, as well as for pyrotechnologies and in industrial processes over more recent centuries. Many landscapes need fire but population expansion into wildland areas creates a tension between different interest groups. Extinguishing wildfires may not always be the correct solution. A combination of factors, including the problem of invasive plants, landscape change, climate change, population growth, human health, economic, social and cultural attitudes that may be transnational make a re-evaluation of fire and mankind necessary. The Royal Society meeting on Fire and mankind was held to address these issues and the results of these deliberations are published in this volume.This article is part of the themed issue 'The interaction of fire and mankind'.
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http://dx.doi.org/10.1098/rstb.2015.0162DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874400PMC
June 2016

The interaction of fire and mankind.

Philos Trans R Soc Lond B Biol Sci 2016 06;371(1696)

Department of Anthropology, Southern Methodist University, Dallas, TX 75275-0336, USA.

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http://dx.doi.org/10.1098/rstb.2016.0149DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874423PMC
June 2016

Living on a flammable planet: interdisciplinary, cross-scalar and varied cultural lessons, prospects and challenges.

Philos Trans R Soc Lond B Biol Sci 2016 06;371(1696)

School of Environment and Sustainability, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5C8.

Living with fire is a challenge for human communities because they are influenced by socio-economic, political, ecological and climatic processes at various spatial and temporal scales. Over the course of 2 days, the authors discussed how communities could live with fire challenges at local, national and transnational scales. Exploiting our diverse, international and interdisciplinary expertise, we outline generalizable properties of fire-adaptive communities in varied settings where cultural knowledge of fire is rich and diverse. At the national scale, we discussed policy and management challenges for countries that have diminishing fire knowledge, but for whom global climate change will bring new fire problems. Finally, we assessed major fire challenges that transcend national political boundaries, including the health burden of smoke plumes and the climate consequences of wildfires. It is clear that to best address the broad range of fire problems, a holistic wildfire scholarship must develop common agreement in working terms and build across disciplines. We must also communicate our understanding of fire and its importance to the media, politicians and the general public.This article is part of the themed issue 'The interaction of fire and mankind'.
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http://dx.doi.org/10.1098/rstb.2015.0469DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4874422PMC
June 2016

Effects of spatial heterogeneity in moisture content on the horizontal spread of peat fires.

Sci Total Environ 2016 Dec 20;572:1422-1430. Epub 2016 Apr 20.

School of Biology and Environmental Science, Earth Institute, University College Dublin, Dublin D4, Ireland.

The gravimetric moisture content of peat is the main factor limiting the ignition and spread propagation of smouldering fires. Our aim is to use controlled laboratory experiments to better understand how the spread of smouldering fires is influenced in natural landscape conditions where the moisture content of the top peat layer is not homogeneous. In this paper, we study for the first time the spread of peat fires across a spatial matrix of two moisture contents (dry/wet) in the laboratory. The experiments were undertaken using an open-top insulated box (22×18×6cm) filled with milled peat. The peat was ignited at one side of the box initiating smouldering and horizontal spread. Measurements of the peak temperature inside the peat, fire duration and longwave thermal radiation from the burning samples revealed important local changes of the smouldering behaviour in response to sharp gradients in moisture content. Both, peak temperatures and radiation in wetter peat (after the moisture gradient) were sensitive to the drier moisture condition (preceding the moisture gradient). Drier peat conditions before the moisture gradient led to higher temperatures and higher radiation flux from the fire during the first 6cm of horizontal spread into a wet peat patch. The total spread distance into a wet peat patch was affected by the moisture content gradient. We predicted that in most peat moisture gradients of relevance to natural ecosystems the fire self-extinguishes within the first 10cm of horizontal spread into a wet peat patch. Spread distances of more than 10cm are limited to wet peat patches below 160% moisture content (mass of water per mass of dry peat). We found that spatial gradients of moisture content have important local effects on the horizontal spread and should be considered in field and modelling studies.
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http://dx.doi.org/10.1016/j.scitotenv.2016.02.145DOI Listing
December 2016

Determinants of flammability in savanna grass species.

J Ecol 2016 Jan 26;104(1):138-148. Epub 2015 Nov 26.

Department of Animal and Plant Sciences University of Sheffield Sheffield S10 2TN UK.

Tropical grasses fuel the majority of fires on Earth. In fire-prone landscapes, enhanced flammability may be adaptive for grasses via the maintenance of an open canopy and an increase in spatiotemporal opportunities for recruitment and regeneration. In addition, by burning intensely but briefly, high flammability may protect resprouting buds from lethal temperatures. Despite these potential benefits of high flammability to fire-prone grasses, variation in flammability among grass species, and how trait differences underpin this variation, remains unknown.By burning leaves and plant parts, we experimentally determined how five plant traits (biomass quantity, biomass density, biomass moisture content, leaf surface-area-to-volume ratio and leaf effective heat of combustion) combined to determine the three components of flammability (ignitability, sustainability and combustibility) at the leaf and plant scales in 25 grass species of fire-prone South African grasslands at a time of peak fire occurrence. The influence of evolutionary history on flammability was assessed based on a phylogeny built here for the study species.Grass species differed significantly in all components of flammability. Accounting for evolutionary history helped to explain patterns in leaf-scale combustibility and sustainability. The five measured plant traits predicted components of flammability, particularly leaf ignitability and plant combustibility in which 70% and 58% of variation, respectively, could be explained by a combination of the traits. Total above-ground biomass was a key driver of combustibility and sustainability with high biomass species burning more intensely and for longer, and producing the highest predicted fire spread rates. Moisture content was the main influence on ignitability, where species with higher moisture contents took longer to ignite and once alight burnt at a slower rate. Biomass density, leaf surface-area-to-volume ratio and leaf effective heat of combustion were weaker predictors of flammability components. . We demonstrate that grass flammability is predicted from easily measurable plant functional traits and is influenced by evolutionary history with some components showing phylogenetic signal. Grasses are not homogenous fuels to fire. Rather, species differ in functional traits that in turn demonstrably influence flammability. This diversity is consistent with the idea that flammability may be an adaptive trait for grasses of fire-prone ecosystems.
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http://dx.doi.org/10.1111/1365-2745.12503DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4738432PMC
January 2016

Charcoal reflectance reveals early holocene boreal deciduous forests burned at high intensities.

PLoS One 2015 8;10(4):e0120835. Epub 2015 Apr 8.

Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America.

Wildfire size, frequency, and severity are increasing in the Alaskan boreal forest in response to climate warming. One of the potential impacts of this changing fire regime is the alteration of successional trajectories, from black spruce to mixed stands dominated by aspen, a vegetation composition not experienced since the early Holocene. Such changes in vegetation composition may consequently alter the intensity of fires, influencing fire feedbacks to the ecosystem. Paleorecords document past wildfire-vegetation dynamics and as such, are imperative for our understanding of how these ecosystems will respond to future climate warming. For the first time, we have used reflectance measurements of macroscopic charcoal particles (>180μm) from an Alaskan lake-sediment record to estimate ancient charring temperatures (termed pyrolysis intensity). We demonstrate that pyrolysis intensity increased markedly from an interval of birch tundra 11 ky ago (mean 1.52%Ro; 485°C), to the expansion of trees on the landscape ~10.5 ky ago, remaining high to the present (mean 3.54%Ro; 640°C) irrespective of stand composition. Despite differing flammabilities and adaptations to fire, the highest pyrolysis intensities derive from two intervals with distinct vegetation compositions. 1) the expansion of mixed aspen and spruce woodland at 10 cal. kyr BP, and 2) the establishment of black spruce, and the modern boreal forest at 4 cal. kyr BP. Based on our analysis, we infer that predicted expansion of deciduous trees into the boreal forest in the future could lead to high intensity, but low severity fires, potentially moderating future climate-fire feedbacks.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0120835PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4390342PMC
December 2015

Charring temperatures are driven by the fuel types burned in a peatland wildfire.

Front Plant Sci 2014 16;5:714. Epub 2014 Dec 16.

School of Biology and Environmental Science, University College Dublin Dublin, Ireland ; Earth Institute, University College Dublin Dublin, Ireland.

Peatlands represent a globally important carbon store; however, the human exploitation of this ecosystem is increasing both the frequency and severity of fires on drained peatlands. Yet, the interactions between the hydrological conditions (ecotopes), the fuel types being burned, the burn severity, and the charring temperatures (pyrolysis intensity) remain poorly understood. Here we present a post-burn assessment of a fire on a lowland raised bog in Co. Offaly, Ireland (All Saints Bog). Three burn severities were identified in the field (light, moderate, and deeply burned), and surface charcoals were taken from 17 sites across all burn severities. Charcoals were classified into two fuel type categories (either ground or aboveground fuel) and the reflectance of each charcoal particle was measured under oil using reflectance microscopy. Charcoal reflectance shows a positive relationship with charring temperature and as such can be used as a temperature proxy to reconstruct minimum charring temperatures after a fire event. Resulting median reflectance values for ground fuels are 1.09 ± 0.32%Romedian, corresponding to estimated minimum charring temperatures of 447°C ± 49°C. In contrast, the median charring temperatures of aboveground fuels were found to be considerably higher, 646°C ± 73°C (3.58 ± 0.77%Romedian). A mixed-effects modeling approach was used to demonstrate that the interaction effects of burn severity, as well as ecotope classes, on the charcoal reflectance is small compared to the main effect of fuel type. Our findings reveal that the different fuel types on raised bogs are capable of charring at different temperatures within the same fire, and that the pyrolysis intensity of the fire on All Saints Bog was primarily driven by the fuel types burning, with only a weak association to the burn severity or ecotope classes.
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http://dx.doi.org/10.3389/fpls.2014.00714DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4267186PMC
January 2015

Accuracy and consistency of grass pollen identification by human analysts using electron micrographs of surface ornamentation.

Appl Plant Sci 2014 Aug 12;2(8). Epub 2014 Aug 12.

Department of Plant Biology, University of Illinois, 505 South Goodwin Avenue, Urbana, Illinois 61801 USA.

Unlabelled:

Premise Of The Study: Humans frequently identify pollen grains at a taxonomic rank above species. Grass pollen is a classic case of this situation, which has led to the development of computational methods for identifying grass pollen species. This paper aims to provide context for these computational methods by quantifying the accuracy and consistency of human identification. •

Methods: We measured the ability of nine human analysts to identify 12 species of grass pollen using scanning electron microscopy images. These are the same images that were used in computational identifications. We have measured the coverage, accuracy, and consistency of each analyst, and investigated their ability to recognize duplicate images. •

Results: Coverage ranged from 87.5% to 100%. Mean identification accuracy ranged from 46.67% to 87.5%. The identification consistency of each analyst ranged from 32.5% to 87.5%, and each of the nine analysts produced considerably different identification schemes. The proportion of duplicate image pairs that were missed ranged from 6.25% to 58.33%. •

Discussion: The identification errors made by each analyst, which result in a decline in accuracy and consistency, are likely related to psychological factors such as the limited capacity of human memory, fatigue and boredom, recency effects, and positivity bias.
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http://dx.doi.org/10.3732/apps.1400031DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4141715PMC
August 2014

Charcoal morphometry for paleoecological analysis: The effects of fuel type and transportation on morphological parameters.

Appl Plant Sci 2014 Aug 18;2(8). Epub 2014 Aug 18.

Earth System Science Group, College of Life and Environmental Sciences, University of Exeter, Level 7 Laver Building, North Park Road, Exeter EX4 4QE, United Kingdom.

Unlabelled:

Premise Of The Study: Charcoal particles preserved in sediments are used as indicators of paleowildfire. Most research focuses on abundance as an indicator of fire frequency, but charcoals also convey information about the vegetation from which they are derived. One potential source of information is their morphology, which is influenced by the parent material, the nature of the fire, and subsequent transportation and burial. •

Methods: We charcoalified 26 materials from a range of plant taxa, and subjected them to simulated fluvial transport by tumbling them with water and gravel. We photographed the resulting particles, and used image analysis software to measure morphological parameters. •

Results: Leaf charcoal displayed a logarithmic decrease in area, and a logarithmic increase in circularity, with transportation time. Trends were less clear for stem or wood charcoal. Grass charcoal displayed significantly higher aspect ratios than other charcoal types. •

Conclusions: Leaf charcoal displays more easily definable relationships between morphological parameters and degree of breakdown than stem or wood charcoal. The aspect ratios of fossil mesocharcoal can indicate the broad botanical source of an assemblage. Coupled to estimates of charcoal abundance, this will improve understanding of the variation in flammability of ancient ecosystems.
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http://dx.doi.org/10.3732/apps.1400004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4141710PMC
August 2014

Novel application of confocal laser scanning microscopy and 3D volume rendering toward improving the resolution of the fossil record of charcoal.

PLoS One 2013 15;8(8):e72265. Epub 2013 Aug 15.

Department of Geography, University of Exeter, Exeter, United Kingdom.

Variations in the abundance of fossil charcoals between rocks and sediments are assumed to reflect changes in fire activity in Earth's past. These variations in fire activity are often considered to be in response to environmental, ecological or climatic changes. The role that fire plays in feedbacks to such changes is becoming increasingly important to understand and highlights the need to create robust estimates of variations in fossil charcoal abundance. The majority of charcoal based fire reconstructions quantify the abundance of charcoal particles and do not consider the changes in the morphology of the individual particles that may have occurred due to fragmentation as part of their transport history. We have developed a novel application of confocal laser scanning microscopy coupled to image processing that enables the 3-dimensional reconstruction of individual charcoal particles. This method is able to measure the volume of both microfossil and mesofossil charcoal particles and allows the abundance of charcoal in a sample to be expressed as total volume of charcoal. The method further measures particle surface area and shape allowing both relationships between different size and shape metrics to be analysed and full consideration of variations in particle size and size sorting between different samples to be studied. We believe application of this new imaging approach could allow significant improvement in our ability to estimate variations in past fire activity using fossil charcoals.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0072265PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3744490PMC
January 2015

Increased atmospheric SO₂ detected from changes in leaf physiognomy across the Triassic-Jurassic boundary interval of East Greenland.

PLoS One 2013 10;8(4):e60614. Epub 2013 Apr 10.

School of Biology and Environmental Science, University College Dublin, Belfield, Dublin, Ireland.

The Triassic-Jurassic boundary (Tr-J; ∼201 Ma) is marked by a doubling in the concentration of atmospheric CO2, rising temperatures, and ecosystem instability. This appears to have been driven by a major perturbation in the global carbon cycle due to massive volcanism in the Central Atlantic Magmatic Province. It is hypothesized that this volcanism also likely delivered sulphur dioxide (SO2) to the atmosphere. The role that SO2 may have played in leading to ecosystem instability at the time has not received much attention. To date, little direct evidence has been presented from the fossil record capable of implicating SO2 as a cause of plant extinctions at this time. In order to address this, we performed a physiognomic leaf analysis on well-preserved fossil leaves, including Ginkgoales, bennettites, and conifers from nine plant beds that span the Tr-J boundary at Astartekløft, East Greenland. The physiognomic responses of fossil taxa were compared to the leaf size and shape variations observed in nearest living equivalent taxa exposed to simulated palaeoatmospheric treatments in controlled environment chambers. The modern taxa showed a statistically significant increase in leaf roundness when fumigated with SO2. A similar increase in leaf roundness was also observed in the Tr-J fossil taxa immediately prior to a sudden decrease in their relative abundances at Astartekløft. This research reveals that increases in atmospheric SO2 can likely be traced in the fossil record by analyzing physiognomic changes in fossil leaves. A pattern of relative abundance decline following increased leaf roundness for all six fossil taxa investigated supports the hypothesis that SO2 had a significant role in Tr-J plant extinctions. This finding highlights that the role of SO2 in plant biodiversity declines across other major geological boundaries coinciding with global scale volcanism should be further explored using leaf physiognomy.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0060614PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3622679PMC
October 2013

Fire-adapted traits of Pinus arose in the fiery Cretaceous.

New Phytol 2012 May 20;194(3):751-759. Epub 2012 Feb 20.

Department of Environment and Agriculture, Curtin University, PO Box U1987, Perth, WA 6845, Australia.

• The mapping of functional traits onto chronograms is an emerging approach for the identification of how agents of natural selection have shaped the evolution of organisms. Recent research has reported fire-dependent traits appearing among flowering plants from 60 million yr ago (Ma). Although there are many records of fossil charcoal in the Cretaceous (65-145 Ma), evidence of fire-dependent traits evolving in that period is lacking. • We link the evolutionary trajectories for five fire-adapted traits in Pinaceae with paleoatmospheric conditions over the last 250 million yr to determine the time at which fire originated as a selective force in trait evolution among seed plants. • Fire-protective thick bark originated in Pinus c. 126 Ma in association with low-intensity surface fires. More intense crown fires emerged c. 89 Ma coincident with thicker bark and branch shedding, or serotiny with branch retention as an alternative strategy. These innovations appeared at the same time as the Earth's paleoatmosphere experienced elevated oxygen levels that led to high burn probabilities during the mid-Cretaceous. • The fiery environments of the Cretaceous strongly influenced trait evolution in Pinus. Our evidence for a strong correlation between the evolution of fire-response strategies and changes in fire regime 90-125 Ma greatly backdates the key role that fire has played in the evolution of seed plants.
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http://dx.doi.org/10.1111/j.1469-8137.2012.04079.xDOI Listing
May 2012

Baseline intrinsic flammability of Earth's ecosystems estimated from paleoatmospheric oxygen over the past 350 million years.

Proc Natl Acad Sci U S A 2010 Dec 13;107(52):22448-53. Epub 2010 Dec 13.

School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland.

Atmospheric oxygen (O(2)) is estimated to have varied greatly throughout Earth's history and has been capable of influencing wildfire activity wherever fuel and ignition sources were present. Fires consume huge quantities of biomass in all ecosystems and play an important role in biogeochemical cycles. This means that understanding the influence of O(2) on past fire activity has far-reaching consequences for the evolution of life and Earth's biodiversity over geological timescales. We have used a strong electrical ignition source to ignite smoldering fires, and we measured their self-sustaining propagation in atmospheres of different oxygen concentrations. These data have been used to build a model that we use to estimate the baseline intrinsic flammability of Earth's ecosystems according to variations in O(2) over the past 350 million years (Ma). Our aim is to highlight times in Earth's history when fire has been capable of influencing the Earth system. We reveal that fire activity would be greatly suppressed below 18.5% O(2), entirely switched off below 16% O(2), and rapidly enhanced between 19-22% O(2). We show that fire activity and, therefore, its influence on the Earth system would have been high during the Carboniferous (350-300 Ma) and Cretaceous (145-65 Ma) periods; intermediate in the Permian (299-251 Ma), Late Triassic (285-201 Ma), and Jurassic (201-145 Ma) periods; and surprisingly low to lacking in the Early-Middle Triassic period between 250-240 Ma. These baseline variations in Earth's flammability must be factored into our understanding of past vegetation, biodiversity, evolution, and biogeochemical cycles.
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http://dx.doi.org/10.1073/pnas.1011974107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3012516PMC
December 2010

From fiery beginnings: wildfires facilitated the spread of angiosperms in the Cretaceous.

Authors:
Claire M Belcher

New Phytol 2010 Dec;188(4):913-5

School of Geosciences and BRE Centre for Fire Safety Engineering, The University of Edinburgh, The King's Buildings, West Mains Road, Edinburgh EH9 3JN, UK.

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http://dx.doi.org/10.1111/j.1469-8137.2010.03528.xDOI Listing
December 2010

Geochemical evidence for combustion of hydrocarbons during the K-T impact event.

Proc Natl Acad Sci U S A 2009 Mar 26;106(11):4112-7. Epub 2009 Feb 26.

Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, United Kingdom.

It has been proposed that extensive wildfires occurred after the Cretaceous-Tertiary (K-T) impact event. An abundance of soot and pyrosynthetic polycyclic aromatic hydrocarbons (pPAHs) in marine K-T boundary impact rocks (BIRs) have been considered support for this hypothesis. However, nonmarine K-T BIRs, from across North America, contain only rare occurrences of charcoal yet abundant noncharred plant remains. pPAHs and soot can be formed from a variety of sources, including partial combustion of vegetation and hydrocarbons whereby modern pPAH signatures are traceable to their source. We present results from multiple nonmarine K-T boundary sites from North America and reveal that the K-T BIRs have a pPAH signature consistent with the combustion of hydrocarbons and not living plant biomass, providing further evidence against K-T wildfires and compelling evidence that a significant volume of hydrocarbons was combusted during the K-T impact event.
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http://dx.doi.org/10.1073/pnas.0813117106DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2657452PMC
March 2009