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McElwain JC, Matthaeus WJ, Barbosa C, Chondrogiannis C, O' Dea K, Jackson B, Knetge AB, Kwasniewska K, Nair R, White JD, Wilson JP, Montañez IP, Buckley YM, Belcher CM, Nogué S. Functional traits of fossil plants. THE NEW PHYTOLOGIST 2024; 242:392-423. [PMID: 38409806 DOI: 10.1111/nph.19622] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Accepted: 12/19/2023] [Indexed: 02/28/2024]
Abstract
A minuscule fraction of the Earth's paleobiological diversity is preserved in the geological record as fossils. What plant remnants have withstood taphonomic filtering, fragmentation, and alteration in their journey to become part of the fossil record provide unique information on how plants functioned in paleo-ecosystems through their traits. Plant traits are measurable morphological, anatomical, physiological, biochemical, or phenological characteristics that potentially affect their environment and fitness. Here, we review the rich literature of paleobotany, through the lens of contemporary trait-based ecology, to evaluate which well-established extant plant traits hold the greatest promise for application to fossils. In particular, we focus on fossil plant functional traits, those measurable properties of leaf, stem, reproductive, or whole plant fossils that offer insights into the functioning of the plant when alive. The limitations of a trait-based approach in paleobotany are considerable. However, in our critical assessment of over 30 extant traits we present an initial, semi-quantitative ranking of 26 paleo-functional traits based on taphonomic and methodological criteria on the potential of those traits to impact Earth system processes, and for that impact to be quantifiable. We demonstrate how valuable inferences on paleo-ecosystem processes (pollination biology, herbivory), past nutrient cycles, paleobiogeography, paleo-demography (life history), and Earth system history can be derived through the application of paleo-functional traits to fossil plants.
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Affiliation(s)
- Jennifer C McElwain
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - William J Matthaeus
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Catarina Barbosa
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | | | - Katie O' Dea
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Bea Jackson
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Antonietta B Knetge
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Kamila Kwasniewska
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Richard Nair
- School of Natural Sciences, Botany, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | - Joseph D White
- Department of Biology, Baylor University, Waco, 76798-7388, TX, USA
| | - Jonathan P Wilson
- Department of Environmental Studies, Haverford College, Haverford, Pennsylvania, 19041, PA, USA
| | - Isabel P Montañez
- UC Davis Institute of the Environment, University of California, Davis, CA, 95616, USA
- Department of Earth and Planetary Sciences, University of California, Davis, CA, 95616, USA
| | - Yvonne M Buckley
- School of Natural Sciences, Zoology, Trinity College Dublin, Dublin, D02 PN40, Ireland
| | | | - Sandra Nogué
- Universitat Autònoma de Barcelona, Bellaterra (Cerdanyola del Vallès), 08193, Catalonia, Spain
- CREAF, Bellaterra (Cerdanyola del Vallès), 08193, Catalonia, Spain
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2
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Gurung K, Field KJ, Batterman SA, Poulton SW, Mills BJW. Geographic range of plants drives long-term climate change. Nat Commun 2024; 15:1805. [PMID: 38418475 PMCID: PMC10901853 DOI: 10.1038/s41467-024-46105-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 02/14/2024] [Indexed: 03/01/2024] Open
Abstract
Long computation times in vegetation and climate models hamper our ability to evaluate the potentially powerful role of plants on weathering and carbon sequestration over the Phanerozoic Eon. Simulated vegetation over deep time is often homogenous, and disregards the spatial distribution of plants and the impact of local climatic variables on plant function. Here we couple a fast vegetation model (FLORA) to a spatially-resolved long-term climate-biogeochemical model (SCION), to assess links between plant geographical range, the long-term carbon cycle and climate. Model results show lower rates of carbon fixation and up to double the previously predicted atmospheric CO2 concentration due to a limited plant geographical range over the arid Pangea supercontinent. The Mesozoic dispersion of the continents increases modelled plant geographical range from 65% to > 90%, amplifying global CO2 removal, consistent with geological data. We demonstrate that plant geographical range likely exerted a major, under-explored control on long-term climate change.
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Affiliation(s)
- Khushboo Gurung
- School of Earth and Environment, University of Leeds, Leeds, UK.
| | - Katie J Field
- Plants, Photosynthesis and Soil, School of Biosciences, University of Sheffield, Sheffield, UK
| | - Sarah A Batterman
- Cary Institute of Ecosystem Studies, Millbrook, NY, USA
- School of Geography, University of Leeds, Leeds, UK
- Smithsonian Tropical Research Institute, Panama City, Panama, USA
| | - Simon W Poulton
- School of Earth and Environment, University of Leeds, Leeds, UK
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3
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Gastaldo RA, Gensel PG, Glasspool IJ, Hinds SJ, King OA, McLean D, Park AF, Stimson MR, Stonesifer T. Enigmatic fossil plants with three-dimensional, arborescent-growth architecture from the earliest Carboniferous of New Brunswick, Canada. Curr Biol 2024; 34:781-792.e3. [PMID: 38309270 DOI: 10.1016/j.cub.2024.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Revised: 10/31/2023] [Accepted: 01/03/2024] [Indexed: 02/05/2024]
Abstract
The evolution of arborescence in Devonian plants, followed by their architectural radiation in the Carboniferous, is a transition fundamental to Earth-system processes and ecological development. However, this evolutionary transition in trees is based on preserved trunks, of which only a few known specimens possess crowns. We describe Mississippian-aged (Tournaisian) trees with a unique three-dimensional crown morphology from New Brunswick, Canada. The trees were preserved by earthquake-induced, catastrophic burial of lake-margin vegetation. The tree architecture consists of an unbranched, 16-cm-diameter trunk with compound leaves arranged in spirals of ∼13 and compressed into ∼14 cm of vertical trunk length. Compound leaves in the upper ∼0.75 m of the trunk measure >1.75 m in length and preserve alternately arranged secondary laterals beginning at 0.5 m from the trunk; the area below the trunk bears only persistent leaf bases. The principal specimen lacks either apical or basal sections, although an apex is preserved in another. Apically, the leaves become less relaxed toward horizontal and are borne straight at an acute angle at the crown. The compact leaf organization and leaf length created a crown volume of >20-30 m3. This growth strategy likely maximized light interception and reduced resource competition from groundcover. From their growth morphology, canopy size, and volume, we propose that these fossils represent the earliest evidence of arborescent subcanopy-tiering. Moreover, although systematically unresolved, this specimen shows that Early Carboniferous vegetation was more complex than realized, signaling that it was a time of experimental, possibly transitional and varied, growth architectures.
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Affiliation(s)
- Robert A Gastaldo
- Department of Geology, Colby College, Waterville, ME 04901, USA; Department of Paleobiology, NMNH Smithsonian, Washington, DC 20560, USA.
| | - Patricia G Gensel
- Deptartment of Biology, UNC, Chapel Hill, Chapel Hill, NC 27599, USA
| | - Ian J Glasspool
- Department of Geology, Colby College, Waterville, ME 04901, USA; Field Museum of Natural History, Chicago, IL 60605, USA
| | - Steven J Hinds
- Geological Surveys Branch, New Brunswick Department of Natural Resources and Energy Development, Fredericton, NB E3B 5H1, Canada
| | - Olivia A King
- New Brunswick Museum, Saint John, NB E2K 1E5, Canada; Deptartment of Geology, Saint Mary's University, Halifax, NS B3H 3C3, Canada
| | | | - Adrian F Park
- Geological Surveys Branch, New Brunswick Department of Natural Resources and Energy Development, Fredericton, NB E3B 5H1, Canada
| | - Matthew R Stimson
- New Brunswick Museum, Saint John, NB E2K 1E5, Canada; Deptartment of Geology, Saint Mary's University, Halifax, NS B3H 3C3, Canada
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Di Giuseppe F, Vitolo C, Barnard C, Libertá G, Maciel P, San-Miguel-Ayanz J, Villaume S, Wetterhall F. Global seasonal prediction of fire danger. Sci Data 2024; 11:128. [PMID: 38272947 PMCID: PMC10810953 DOI: 10.1038/s41597-024-02948-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2023] [Accepted: 01/10/2024] [Indexed: 01/27/2024] Open
Abstract
The European Centre for Medium range weather forecast (ECMWF) on behalf of the Copernicus Emergency Management Service (CEMS) has recently widened the fire danger data offering in the Climate Data Store (CDS) to include a set of fire danger forecasts with lead times up to 7 months. The dataset incorporates fire danger indices for three different models developed in Canada, United States and Australia. The indices are calculated using ECMWF Seasonal Forecasting System 5 (SEAS5) and verified against the relevant reanalysis of fire danger based on the ECMWF Re-Analysis (ERA5). The data set is made openly available for the period 1981 to 2023 and will be updated regularly providing a resource to assess the predictability of fire weather at the seasonal time scale. The data set complements the availability of seasonal forecast provided by the Copernicus Emergency Management Service in real time.A preliminary analysis shows that globally anomalous conditions for fire weather can be predicted with confidence 1 month ahead. In some regions the prediction can extend to 2 months ahead. In most situations beyond this horizon, forecasts do not show more skill than climatology. However an extended predictability window, up to 6-7 months ahead is possible when anomalous fire weather is the results of large scale phenomena such as the El Niño Southern Oscillation and the Indian Ocean Dipole, often conducive of extensive fire burning in regions such as Indonesia and Australia.
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Affiliation(s)
- Francesca Di Giuseppe
- Europen Centre for Medium-Range Weather Forecast, Reading (ECMWF), Reading, United Kingdom.
| | - Claudia Vitolo
- Europen Centre for Medium-Range Weather Forecast, Reading (ECMWF), Reading, United Kingdom
- European Space Agency (ESA), Frascati, Italy
| | - Christopher Barnard
- Europen Centre for Medium-Range Weather Forecast, Reading (ECMWF), Reading, United Kingdom
| | | | - Pedro Maciel
- Europen Centre for Medium-Range Weather Forecast, Reading (ECMWF), Reading, United Kingdom
| | | | - Sebastien Villaume
- Europen Centre for Medium-Range Weather Forecast, Reading (ECMWF), Reading, United Kingdom
| | - Fredrik Wetterhall
- Europen Centre for Medium-Range Weather Forecast, Reading (ECMWF), Reading, United Kingdom
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Gao D, Guo H, Wang J, Shi Y, Chen D. Paleo-Wildfires and Their Paleoclimatic Effects in Early Permian Coal in the Southern North China Basin. ACS OMEGA 2023; 8:24210-24217. [PMID: 37457456 PMCID: PMC10339330 DOI: 10.1021/acsomega.3c00127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Accepted: 06/12/2023] [Indexed: 07/18/2023]
Abstract
Paleo-wildfires can help elucidate the transition trends of Earth from "icehouse" to "greenhouse," thereby allowing us to forecast the current changes associated with wildfires of this era. In this study, the early Permian Shanxi Formation in the Pingdingshan coalfield, located south of the North China Basin, was selected as a study site. Based on data on inertinite content, inertinite reflectance, nine polycyclic aromatic hydrocarbons (PAHs), paleo-wildfires, and their paleoclimate effect during the early Permian coal formation were systematically analyzed. The inertinite content in coal in the study area ranged from 9.76 to 29.65%, with an average of 19.32%. Meanwhile, the average inertinite reflectance values ranged from 2.41-4.74%, with an average of 2.75%. PAHs in the study area were mainly tricyclic and tetracyclic; the contents of fluorene, phenanthrene, pyrene, bypyrene, benzo[b]fluoranthene, and benzo[e]pyrene were higher than those of other PAHs in the same stratum. The total concentration of PAHs varied widely between layers (3601-21,894 ng/g). The presence of paleo-wildfires was confirmed by the contents of inertinite and PAHs. It can be concluded that paleo-wildfires in the study area were dominated by surface fires at low and medium temperatures based on the combustion equation. The oxygen content in the paleo-atmosphere of the Early Permian Shanxi Formation in the study area was 24.29%, which provided the necessary conditions for the occurrence of wildfires.
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Affiliation(s)
- Di Gao
- School
of Resources and Environments, Henan Polytechnic
University, Jiaozuo 454003, China
- State
Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China
- Collaborative
Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Jiaozuo 454003, China
| | - Huiling Guo
- School
of Resources and Environments, Henan Polytechnic
University, Jiaozuo 454003, China
| | - Juan Wang
- School
of Resources and Environments, Henan Polytechnic
University, Jiaozuo 454003, China
- Collaborative
Innovation Center of Coal Work Safety and Clean High Efficiency Utilization, Jiaozuo 454003, China
| | - Yi Shi
- School
of Resources and Environments, Henan Polytechnic
University, Jiaozuo 454003, China
| | - Di Chen
- School
of Resources and Environments, Henan Polytechnic
University, Jiaozuo 454003, China
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6
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Cao D, Baskin JM, Baskin CC, Li DZ. Burning lignin: overlooked cues for post-fire seed germination. TRENDS IN PLANT SCIENCE 2023; 28:386-389. [PMID: 36801194 DOI: 10.1016/j.tplants.2023.01.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 01/18/2023] [Accepted: 01/26/2023] [Indexed: 06/18/2023]
Abstract
Information about smoke cues for seed germination is fundamental to understanding fire adaptation. Recently, lignin-derived syringaldehyde (SAL) was identified as a new smoke cue for seed germination, which challenges the assumption that cellulose-derived karrikins are the primary smoke cues. We highlight the overlooked association between lignin and the fire adaptation of plants.
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Affiliation(s)
- Dechang Cao
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China
| | - Jerry M Baskin
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA
| | - Carol C Baskin
- Department of Biology, University of Kentucky, Lexington, KY 40506-0225, USA; Department of Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546-0312, USA
| | - De-Zhu Li
- Germplasm Bank of Wild Species, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China.
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7
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Khan K, Van Aken O. The colonization of land was a likely driving force for the evolution of mitochondrial retrograde signalling in plants. JOURNAL OF EXPERIMENTAL BOTANY 2022; 73:7182-7197. [PMID: 36055768 PMCID: PMC9675596 DOI: 10.1093/jxb/erac351] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 08/29/2022] [Indexed: 06/15/2023]
Abstract
Most retrograde signalling research in plants was performed using Arabidopsis, so an evolutionary perspective on mitochondrial retrograde regulation (MRR) is largely missing. Here, we used phylogenetics to track the evolutionary origins of factors involved in plant MRR. In all cases, the gene families can be traced to ancestral green algae or earlier. However, the specific subfamilies containing factors involved in plant MRR in many cases arose during the transition to land. NAC transcription factors with C-terminal transmembrane domains, as observed in the key regulator ANAC017, can first be observed in non-vascular mosses, and close homologs to ANAC017 can be found in seed plants. Cyclin-dependent kinases (CDKs) are common to eukaryotes, but E-type CDKs that control MRR also diverged in conjunction with plant colonization of land. AtWRKY15 can be traced to the earliest land plants, while AtWRKY40 only arose in angiosperms and AtWRKY63 even more recently in Brassicaceae. Apetala 2 (AP2) transcription factors are traceable to algae, but the ABI4 type again only appeared in seed plants. This strongly suggests that the transition to land was a major driver for developing plant MRR pathways, while additional fine-tuning events have appeared in seed plants or later. Finally, we discuss how MRR may have contributed to meeting the specific challenges that early land plants faced during terrestrialization.
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Affiliation(s)
- Kasim Khan
- Department of Biology, Lund University, Lund, Sweden
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Sperling EA, Boag TH, Duncan MI, Endriga CR, Marquez JA, Mills DB, Monarrez PM, Sclafani JA, Stockey RG, Payne JL. Breathless through Time: Oxygen and Animals across Earth's History. THE BIOLOGICAL BULLETIN 2022; 243:184-206. [PMID: 36548971 DOI: 10.1086/721754] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
AbstractOxygen levels in the atmosphere and ocean have changed dramatically over Earth history, with major impacts on marine life. Because the early part of Earth's history lacked both atmospheric oxygen and animals, a persistent co-evolutionary narrative has developed linking oxygen change with changes in animal diversity. Although it was long believed that oxygen rose to essentially modern levels around the Cambrian period, a more muted increase is now believed likely. Thus, if oxygen increase facilitated the Cambrian explosion, it did so by crossing critical ecological thresholds at low O2. Atmospheric oxygen likely remained at low or moderate levels through the early Paleozoic era, and this likely contributed to high metazoan extinction rates until oxygen finally rose to modern levels in the later Paleozoic. After this point, ocean deoxygenation (and marine mass extinctions) is increasingly linked to large igneous province eruptions-massive volcanic carbon inputs to the Earth system that caused global warming, ocean acidification, and oxygen loss. Although the timescales of these ancient events limit their utility as exact analogs for modern anthropogenic global change, the clear message from the geologic record is that large and rapid CO2 injections into the Earth system consistently cause the same deadly trio of stressors that are observed today. The next frontier in understanding the impact of oxygen changes (or, more broadly, temperature-dependent hypoxia) in deep time requires approaches from ecophysiology that will help conservation biologists better calibrate the response of the biosphere at large taxonomic, spatial, and temporal scales.
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Borges FO, Sampaio E, Santos CP, Rosa R. Impacts of Low Oxygen on Marine Life: Neglected, but a Crucial Priority for Research. THE BIOLOGICAL BULLETIN 2022; 243:104-119. [PMID: 36548969 DOI: 10.1086/721468] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
AbstractGlobal ocean O2 content has varied significantly across the eons, both shaping and being shaped by the evolutionary history of life on planet Earth. Indeed, past O2 fluctuations have been associated with major extinctions and the reorganization of marine biota. Moreover, its most recent iteration-now anthropogenically driven-represents one of the most prominent challenges for both marine ecosystems and human societies, with ocean deoxygenation being regarded as one of the main drivers of global biodiversity loss. Yet ocean deoxygenation has received far less attention than concurrent environmental variables of marine climate change, namely, ocean warming and acidification, particularly in the field of experimental marine ecology. Together with the lack of consistent criteria defining gradual and acute changes in O2 content, a general lack of multifactorial studies featuring all three drivers and their interactions prevents an adequate interpretation of the potential effects of extreme and gradual deoxygenation. We present a comprehensive overview of the interplay between O2 and marine life across space and time and discuss the current knowledge gaps and future steps for deoxygenation research. This work may also contribute to the ongoing call for an integrative perspective on the combined effects of these three drivers of change for marine organisms and ecosystems worldwide.
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Iglesias V, Balch JK, Travis WR. U.S. fires became larger, more frequent, and more widespread in the 2000s. SCIENCE ADVANCES 2022; 8:eabc0020. [PMID: 35294238 PMCID: PMC8926334 DOI: 10.1126/sciadv.abc0020] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Recent fires have fueled concerns that regional and global warming trends are leading to more extreme burning. We found compelling evidence that average fire events in regions of the United States are up to four times the size, triple the frequency, and more widespread in the 2000s than in the previous two decades. Moreover, the most extreme fires are also larger, more common, and more likely to co-occur with other extreme fires. This documented shift in burning patterns across most of the country aligns with the palpable change in fire dynamics noted by the media, public, and fire-fighting officials.
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Affiliation(s)
- Virginia Iglesias
- Earth Lab, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Boulder, CO 80309, USA
- Corresponding author.
| | - Jennifer K. Balch
- Earth Lab, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Boulder, CO 80309, USA
- Department of Geography, University of Colorado, Boulder, Boulder, CO 80309, USA
| | - William R. Travis
- Earth Lab, Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, Boulder, CO 80309, USA
- Department of Geography, University of Colorado, Boulder, Boulder, CO 80309, USA
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A Multi-Method Approach for Deciphering Rockshelter Microstratigraphies—The Role of the Sodicho Rockshelter (SW Ethiopia) as a Geoarchaeological Archive. GEOSCIENCES 2022. [DOI: 10.3390/geosciences12020092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The Sodicho Rockshelter in the southwestern Ethiopian Highlands presents a unique site that contains sediments of Upper Pleistocene and Holocene occupation phases of hunter-gatherer communities. Excavations and previous geoarchaeological research provided a first 14C chronostratigraphic framework for the last 27 ka cal BP, which supports the hypothesis of a potential environmental refugium during the Late Glacial Maximum (LGM, ~21 ± 2 ka). Nonetheless, it is necessary to extend the preliminary interpretation of stone tool assemblages, and the geoarchaeological analyses carried out so far to provide in-depth information on prehistoric human behavior at the site under changing climatic and environmental conditions. In this study, we reinvestigate the complex stratigraphy and the paleoclimatic context of Sodicho in order to expand the knowledge about site formation, post-depositional disturbances, weathering influences, and the anthropogenic impact on the sediment deposits. Micromorphological observations and the determination of active pedogenic oxides offered a more detailed look at the microstratigraphic record in relation to shifting moisture conditions during the African Humid Period (AHP, ~15 − 5 ka). Sediment alteration and reworking are connected to the influence of sheet flow, biological activity, and human impacts such as dumping activity and site maintenance. A comparison with black carbon (BC) analyses and a qualitative phytolith ratio (quantification of dark and light phytoliths) provided evidence for variations in human fire intensity. Our collaborative and multidisciplinary approach demonstrates how the complex formation of a rockshelter site in a tropical setting with changing climatic and anthropogenic impacts can be tackled.
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Su WQ, Tang C, Lin J, Yu M, Dai Z, Luo Y, Li Y, Xu J. Recovery patterns of soil bacterial and fungal communities in Chinese boreal forests along a fire chronosequence. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 805:150372. [PMID: 34818758 DOI: 10.1016/j.scitotenv.2021.150372] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 09/11/2021] [Accepted: 09/12/2021] [Indexed: 05/17/2023]
Abstract
Wildfire has profound and pervasive consequences for forest ecosystems via directly altering soil physicochemical properties and modulating microbial community. In this study, we examined the changes in soil properties and microbial community composition and structure at different periods after highly severe wildfire events (44 plots, 113 samples) in the Chinese Great Khingan Mountains. We also separated charcoal from burnt soils to establish the relationship between microbial community structures in soils and charcoal. We found that wildfire only significantly altered bacterial and fungal β-diversity, but had no effect on microbial α-diversity across a 29-year chronosequence. The network analysis revealed that the complexity and connectivity of bacterial and fungal communities were significantly increased from 17 years after fire, compared with either unburnt soils or soils with recent fires (0-4 years after fire). Differential abundance analysis suggested that bacterial and fungal OTUs were enriched or depleted only during 0-4 years after fire compared with the unburnt soils. In addition, soil pH, dissolved organic C and dissolved organic N were key determinants of soil bacterial and fungal communities during 17-29 years after fire. The fire-derived charcoal provided a new niche for microbial colonization, and microbes colonized in the charcoal had a significantly different community structure from those of burnt soils. Our data suggest that soil bacterial and fungal communities changed significantly during the recovery from fire events in terms of the abundance and co-occurrence networks in the boreal forest ecosystems.
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Affiliation(s)
- Wei-Qin Su
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China
| | - Caixian Tang
- Department of Animal, Plant and Soil Sciences, La Trobe University, Melbourne Campus, Bundoora, VIC 3086, Australia
| | - Jiahui Lin
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China
| | - Mengjie Yu
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China
| | - Zhongmin Dai
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China
| | - Yu Luo
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China
| | - Yong Li
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China
| | - Jianming Xu
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Agricultural Resources and Environment, Zhejiang University, Hangzhou 310058, China.
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13
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Sønderholm F, Bjerrum CJ. Minimum levels of atmospheric oxygen from fossil tree roots imply new plant-oxygen feedback. GEOBIOLOGY 2021; 19:250-260. [PMID: 33608990 PMCID: PMC8248171 DOI: 10.1111/gbi.12435] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 12/16/2020] [Accepted: 01/14/2021] [Indexed: 06/12/2023]
Abstract
The appearance and subsequent evolution of land plants is among the most important events in the earth system. Plant resulted in a change of earth surface albedo and the hydrological cycle, as well as increased rock weatherability thereby causing a persistent change in atmospheric CO2 and O2 . Land plants are, however, themselves dependent on O2 for respiration and long-term survival, something not considered in current geochemical models. In this perspective, we highlight two aspects of land plants' dependency on O2 relevant for the geobiological community: (a) fossil root systems can be used as a proxy for minimum levels of past atmospheric O2 consistent with a given fossil root depth; and (b) by identifying a positive feedback mechanism involving atmospheric O2 , root intensity, terrestrial primary production and organic carbon burial. As an example, we consider archaeopterid fossil root systems, resembling those of modern mature conifers. Our soil-plant model suggest that atmospheric O2 with 1 SD probably reached pressures of 18.2 ± 1.9 kPa and 16.8 ± 2.1 kPa by the Middle and Late Devonian, respectively, that is 86 ± 9% and 79 ± 10% of the present-day 21.2 kPa.
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Affiliation(s)
- Fredrik Sønderholm
- Department of Geosciences and Natural Resource ManagementUniversity of CopenhagenCopenhagen KDenmark
| | - Christian J. Bjerrum
- Department of Geosciences and Natural Resource ManagementUniversity of CopenhagenCopenhagen KDenmark
- Nordic Center for Earth Evolution, Department of Geoscience and Natural Resource ManagementUniversity of CopenhagenCopenhagen KDenmark
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14
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Xu X, Li F, Lin Z, Song X. Holocene fire history in China: Responses to climate change and human activities. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 753:142019. [PMID: 33207464 DOI: 10.1016/j.scitotenv.2020.142019] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 08/22/2020] [Accepted: 08/25/2020] [Indexed: 06/11/2023]
Abstract
Fire is an intrinsic feature of terrestrial ecosystems as well as a key Earth system process that significantly influences ecosystem patterns, the carbon cycle, and climate. Although local and regional paleofires across China have been investigated, the history of these phenomena at the national scale as well as possible drivers remain unknown. This study investigated spatiotemporal patterns in fire activity across China based on 107 individual site charcoal records. The aim of this work was to discuss the possible impact of climate and human activities on fire in China. Results showed that fire activities across China declined gradually overall between the early Holocene (12 ka BP) and the middle Holocene (7.3 ka BP) but then sharply increased in occurrence after 7.3 ka BP. Data showed that although regional fire activities did not vary synchronously, more events tended to occur in the late Holocene and there were relative less in the early-to-middle Holocene. These changes in Holocene fire activity closely mirrored millennial scale moisture variations across China. Intensified human activities over the last 3 ka might also be responsible for a sharp increase in fire activity. Variable trends in fire activities within regions might also be attributed to large-scale climatic controls modulated by local factors, which determined burn likelihood. This study enhances our insights into the fire history of China and may help to provide improved future projections for such phenomena given current climate change.
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Affiliation(s)
- Xin Xu
- International Center for Climate and Environmental Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Fang Li
- International Center for Climate and Environmental Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China.
| | - Zhongda Lin
- State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
| | - Xiang Song
- International Center for Climate and Environmental Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China
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15
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Lasslop G, Hantson S, Harrison SP, Bachelet D, Burton C, Forkel M, Forrest M, Li F, Melton JR, Yue C, Archibald S, Scheiter S, Arneth A, Hickler T, Sitch S. Global ecosystems and fire: Multi-model assessment of fire-induced tree-cover and carbon storage reduction. GLOBAL CHANGE BIOLOGY 2020; 26:5027-5041. [PMID: 32407565 DOI: 10.1111/gcb.15160] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 04/28/2020] [Indexed: 05/09/2023]
Abstract
In this study, we use simulations from seven global vegetation models to provide the first multi-model estimate of fire impacts on global tree cover and the carbon cycle under current climate and anthropogenic land use conditions, averaged for the years 2001-2012. Fire globally reduces the tree covered area and vegetation carbon storage by 10%. Regionally, the effects are much stronger, up to 20% for certain latitudinal bands, and 17% in savanna regions. Global fire effects on total carbon storage and carbon turnover times are lower with the effect on gross primary productivity (GPP) close to 0. We find the strongest impacts of fire in savanna regions. Climatic conditions in regions with the highest burned area differ from regions with highest absolute fire impact, which are characterized by higher precipitation. Our estimates of fire-induced vegetation change are lower than previous studies. We attribute these differences to different definitions of vegetation change and effects of anthropogenic land use, which were not considered in previous studies and decreases the impact of fire on tree cover. Accounting for fires significantly improves the spatial patterns of simulated tree cover, which demonstrates the need to represent fire in dynamic vegetation models. Based upon comparisons between models and observations, process understanding and representation in models, we assess a higher confidence in the fire impact on tree cover and vegetation carbon compared to GPP, total carbon storage and turnover times. We have higher confidence in the spatial patterns compared to the global totals of the simulated fire impact. As we used an ensemble of state-of-the-art fire models, including effects of land use and the ensemble median or mean compares better to observational datasets than any individual model, we consider the here presented results to be the current best estimate of global fire effects on ecosystems.
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Affiliation(s)
- Gitta Lasslop
- Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany
| | - Stijn Hantson
- Department of Earth System Sciences, University of California Irvine, Irvine, CA, USA
| | - Sandy P Harrison
- School of Archaeology, Geography and Environmental Sciences (SAGES), University of Reading, Reading, UK
| | | | | | - Matthias Forkel
- Environmental Remote Sensing Group, Institute of Photogrammetry and Remote Sensing, Technische Universität Dresden, Dresden, Germany
| | - Matthew Forrest
- Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany
| | - Fang Li
- International Center for Climate and Environmental Sciences, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, China
| | - Joe R Melton
- Climate Research Division, Environment Canada, Victoria, BC, Canada
| | - Chao Yue
- State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling, Shaanxi, People's Republic of China
| | - Sally Archibald
- Centre for African Ecology, School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Johannesburg, South Africa
| | - Simon Scheiter
- Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany
| | - Almut Arneth
- Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Atmospheric Environmental Research, Garmisch-Partenkirchen, Germany
| | - Thomas Hickler
- Senckenberg Biodiversity and Climate Research Centre, Frankfurt am Main, Germany
- Department of Physical Geography, Goethe University, Frankfurt am Main, Germany
| | - Stephen Sitch
- College of Life and Environmental Sciences, University of Exeter, Exeter, UK
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16
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Abstract
Accurately quantifying the composition of continental crust on Hadean and Archean Earth is critical to our understanding of the physiography, tectonics, and climate of our planet at the dawn of life. One longstanding paradigm involves the growth of a relatively mafic planetary crust over the first 1 to 2 billion years of Earth history, implying a lack of modern plate tectonics and a paucity of subaerial crust, and consequently lacking an efficient mechanism to regulate climate. Others have proposed a more uniformitarian view in which Archean and Hadean continents were only slightly more mafic than at present. Apart from complications in assessing early crustal composition introduced by crustal preservation and sampling biases, effects such as the secular cooling of Earth's mantle and the biologically driven oxidation of Earth's atmosphere have not been fully investigated. We find that the former complicates efforts to infer crustal silica from compatible or incompatible element abundances, while the latter undermines estimates of crustal silica content inferred from terrigenous sediments. Accounting for these complications, we find that the data are most parsimoniously explained by a model with nearly constant crustal silica since at least the early Archean.
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18
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Hodshire AL, Akherati A, Alvarado MJ, Brown-Steiner B, Jathar SH, Jimenez JL, Kreidenweis SM, Lonsdale CR, Onasch TB, Ortega AM, Pierce JR. Aging Effects on Biomass Burning Aerosol Mass and Composition: A Critical Review of Field and Laboratory Studies. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:10007-10022. [PMID: 31365241 DOI: 10.1021/acs.est.9b02588] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Biomass burning is a major source of atmospheric particulate matter (PM) with impacts on health, climate, and air quality. The particles and vapors within biomass burning plumes undergo chemical and physical aging as they are transported downwind. Field measurements of the evolution of PM with plume age range from net decreases to net increases, with most showing little to no change. In contrast, laboratory studies tend to show significant mass increases on average. On the other hand, similar effects of aging on the average PM composition (e.g., oxygen-to-carbon ratio) are reported for lab and field studies. Currently, there is no consensus on the mechanisms that lead to these observed similarities and differences. This review summarizes available observations of aging-related biomass burning aerosol mass concentrations and composition markers, and discusses four broad hypotheses to explain variability within and between field and laboratory campaigns: (1) variability in emissions and chemistry, (2) differences in dilution/entrainment, (3) losses in chambers and lines, and (4) differences in the timing of the initial measurement, the baseline from which changes are estimated. We conclude with a concise set of research needs for advancing our understanding of the aging of biomass burning aerosol.
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Affiliation(s)
- Anna L Hodshire
- Department of Atmospheric Science , Colorado State University , Fort Collins , Colorado 80523 , United States
| | - Ali Akherati
- Department of Mechanical Engineering , Colorado State University , Fort Collins , Colorado 80523 , United States
| | - Matthew J Alvarado
- Atmospheric and Environmental Research, Inc. , Lexington , Massachusetts 02421 , United States
| | - Benjamin Brown-Steiner
- Atmospheric and Environmental Research, Inc. , Lexington , Massachusetts 02421 , United States
| | - Shantanu H Jathar
- Department of Mechanical Engineering , Colorado State University , Fort Collins , Colorado 80523 , United States
| | - Jose L Jimenez
- Dept. of Chemistry and Cooperative Institute for Research in Environmental Sciences (CIRES) , University of Colorado , Boulder , Colorado 80309 , United States
| | - Sonia M Kreidenweis
- Department of Atmospheric Science , Colorado State University , Fort Collins , Colorado 80523 , United States
| | - Chantelle R Lonsdale
- Atmospheric and Environmental Research, Inc. , Lexington , Massachusetts 02421 , United States
| | - Timothy B Onasch
- Aerodyne Research Inc. , Billerica , Massachusetts 01821 , United States
| | - Amber M Ortega
- Dept. Atmospheric and Oceanic Sciences Department and Cooperative Institute for Research in Environmental Sciences (CIRES) , University of Colorado , Boulder , Colorado 80309 , United States
| | - Jeffrey R Pierce
- Department of Atmospheric Science , Colorado State University , Fort Collins , Colorado 80523 , United States
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19
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Abstract
Looking across our planet's four-and-a-half billion-year history, the rise of dioxygen-an interval sometimes called the Great Oxygenation Event (GOE)-is arguably the most important environmental change. This revolution occurred approximately 2.3 billion years ago, roughly at the mid-way point in Earth history, and it was ultimately driven by a biological innovation: the evolution of oxygenic photosynthesis. The evolution of oxygenic photosynthesis conferred the ability to use water as a photosynthetic substrate (earlier photosynthesis was anoxygenic and required reduced iron, sulfur, carbon, or hydrogen). Primary productivity-no longer limited by a source of electrons-greatly expanded across the Earth surface. In turn, dioxygen accumulated and became widely available for use in anabolic and catabolic metabolisms, forming a rich cascade of evolutionary potential and consequence. The modern biosphere figured out how to balance harmful oxidative stress with the beneficial ways dioxygen can be used. But how did life come to first tolerate and then thrive in an oxygenated world? It's this question that attracted the diverse perspectives reflected in this special issue.
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Affiliation(s)
| | - Joan Selverstone Valentine
- California Institute of Technology, Pasadena, CA, 91125, USA; University of California Los Angeles, Los Angeles, CA, USA
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20
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Theoretical Reflectance Spectra of Earth-like Planets through Their Evolutions: Impact of Clouds on the Detectability of Oxygen, Water, and Methane with Future Direct Imaging Missions. ACTA ACUST UNITED AC 2019. [DOI: 10.3847/1538-3881/ab14e3] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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21
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Recurrent palaeo-wildfires in a Cisuralian coal seam: A palaeobotanical view on high-inertinite coals from the Lower Permian of the Paraná Basin, Brazil. PLoS One 2019; 14:e0213854. [PMID: 30870527 PMCID: PMC6417680 DOI: 10.1371/journal.pone.0213854] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2018] [Accepted: 03/03/2019] [Indexed: 11/19/2022] Open
Abstract
Distribution and abundance of charcoal in coal seams (in form of pyrogenic macerals of the inertinites group) have been considered as a reliable tool to interpret the local and regional palaeo-wildfire regimes in peat-forming depositional environments. Although the occurrence of inertinites is globally well documented for the Late Palaeozoic, the description of palaeobotanical evidence concerning the source plants of such charcoal is so far largely missing. In the present study, we provide the first detailed analysis of macro-charcoal preserved in the Barro Branco coal seam, Rio Bonito Formation, Cisuralian of the Paraná Basin, Santa Catarina State, Brazil. Charcoal, in form of macro-charcoal and inertinites, was documented in all the six coal-bearing strata that compose the succession, confirming the occurrence of recurrent palaeo-wildfires during its deposition. Reflectance values indicated a mean charring temperature reaching ~515°C (and up to 1,045°C in excess) and the macro-charcoal exhibits anatomical features of secondary xylem of Agathoxylon. Combination of results derived from palaeobotanical and petrological data demonstrates that gymnosperm-dominated vegetation was repeatedly submitted to fire events and reinforced the hypothesis that Gondwanan mires were high-fire systems during the Cisuralian.
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22
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Clack JA, Bennett CE, Davies SJ, Scott AC, Sherwin JE, Smithson TR. A Tournaisian (earliest Carboniferous) conglomerate-preserved non-marine faunal assemblage and its environmental and sedimentological context. PeerJ 2019; 6:e5972. [PMID: 30627480 PMCID: PMC6321757 DOI: 10.7717/peerj.5972] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 10/19/2018] [Indexed: 11/24/2022] Open
Abstract
A conglomerate bed from the Tournaisian Ballagan Formation of Scotland preserves a rich array of vertebrate and other nonmarine fossils providing an insight into the wider ecosystem and paleoenvironment that existed during this pivotal stage of Earth history. It challenges hypotheses of a long-lasting post-extinction trough following the end-Devonian extinction event. The fauna recovered includes a wide size range of tetrapods, rhizodonts, and dipnoans, from tiny juveniles or small-bodied taxa up to large adults, and more than one taxon of each group is likely. Some fauna, such as actinopterygians and chondrichthyans, are rare as macrofauna but are better represented in the microfossil assemblage. The fauna provides evidence of the largest Carboniferous lungfish ever found. The specimens are preserved in a localized, poorly-sorted conglomerate which was deposited in the deepest part of a river channel, the youngest of a group of channels. In addition to the fossils (micro- and macro-), the conglomerate includes locally-derived clasts of paleosols and other distinctive elements of the surrounding floodplains. Charcoal fragments represent small woody axes and possible larger trunk tissue from arborescent pteridosperms. Preservation of the fossils indicates some aerial exposure prior to transport, with abrasion from rolling. The findings presented here contrast with other published trends in vertebrate size that are used to interpret a reduction in maximum sizes during the Tournaisian. The richness of the fauna runs counter to the assumption of a depauperate nonmarine fauna following the end-Devonian Hangenberg event, and charcoal content highlights the occurrence of fire, with the requisite levels of atmospheric oxygen during that stage.
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Affiliation(s)
| | - Carys E Bennett
- School of Geography, Geology and Environment, University of Leicester, Leicester, UK
| | - Sarah J Davies
- School of Geography, Geology and Environment, University of Leicester, Leicester, UK
| | - Andrew C Scott
- Department of Earth Sciences, Royal Holloway University of London, Egham, UK
| | - Janet E Sherwin
- School of Geography, Geology and Environment, University of Leicester, Leicester, UK
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23
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Do relationships between leaf traits and fire behaviour of leaf litter beds persist in time? PLoS One 2018; 13:e0209780. [PMID: 30586427 PMCID: PMC6306239 DOI: 10.1371/journal.pone.0209780] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 12/11/2018] [Indexed: 11/28/2022] Open
Abstract
Wildland fires are a dominant disturbance on Earth. On the local scale, fire activity is also influenced by species-specific fire behaviour of leaf litter beds. Thus, researchers strive to identify plant functional traits governing fire behaviour. The currently accepted relationships between morphological characteristics of the individual particles, fuel bed structure and resulting fire behaviour have been established on freshly constructed leaf litter beds. To investigate to what degree these relationships are altered upon exposure of constructed leaf litter beds to outside weather conditions, a novel testing system was designed. It enables outdoor exposure of the constructed litter beds, their subsequent retrieval and fire behaviour testing without disturbing the sample structure. Two treatments were applied on seven monospecific leaf litters. “Fresh treatment” corresponded to the common practice of testing fire behaviour directly after fuel bed construction. In the “settled treatment” constructed fuel beds were exposed for 30 days to outside weather conditions before being tested. The “settled treatment” was designed to address physical changes in the fuel bed structure which occur due to repeated wetting of the fuel bed. Thus, to minimise the effects of decomposition and fragmentation, winter exposure was chosen. Within the “fresh treatment” previously established relationships between size, curl, bulk density and fire behaviour characteristics could be confirmed. In the “settled treatment” the majority of these relationships lost their significance. The “settled treatment” had significantly lower bulk density (BD), rate of spread, maximum flame height and maximum sand temperature at 1 cm depth; and significantly higher flaming duration and amount of unburned residues compared to the “fresh treatment”. Species with low initial BD were more affected by the treatment than species with high initial BD. The abrupt change in the fire behaviour of some leaf litter beds and the loss of numerous relationships between morphological characteristics of the individual particles and fire behaviour characteristics upon settled treatment indicate that fast occurring changes in the fuel bed structure should be taken into consideration if we are to understand the relationships between functional traits and local fire activity.
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24
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Abstract
Oxygen is essential for animal life, and while geochemical proxies have been instrumental in determining the broad evolutionary history of oxygen on Earth, much of our insight into Phanerozoic oxygen comes from biogeochemical modelling. The GEOCARBSULF model utilizes carbon and sulphur isotope records to produce the most detailed history of Phanerozoic atmospheric O2 currently available. However, its predictions for the Paleozoic disagree with geochemical proxies, and with non-isotope modelling. Here we show that GEOCARBSULF oversimplifies the geochemistry of sulphur isotope fractionation, returning unrealistic values for the O2 sourced from pyrite burial when oxygen is low. We rebuild the model from first principles, utilizing an improved numerical scheme, the latest carbon isotope data, and we replace the sulphur cycle equations in line with forwards modelling approaches. Our new model, GEOCARBSULFOR, produces a revised, highly-detailed prediction for Phanerozoic O2 that is consistent with available proxy data, and independently supports a Paleozoic Oxygenation Event, which likely contributed to the observed radiation of complex, diverse fauna at this time. The GEOCARBSULF model provides the most detailed reconstructions of Phanerozoic O2, but its predictions are not supported by geochemical data. Here, a GEOCARBSULF model rebuilt from first principles, with the addition of an amended sulphur cycle and the latest isotope records, supports a Paleozoic Oxygenation Event.
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25
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Little A, Schwerdt JG, Shirley NJ, Khor SF, Neumann K, O'Donovan LA, Lahnstein J, Collins HM, Henderson M, Fincher GB, Burton RA. Revised Phylogeny of the Cellulose Synthase Gene Superfamily: Insights into Cell Wall Evolution. PLANT PHYSIOLOGY 2018; 177:1124-1141. [PMID: 29780036 PMCID: PMC6052982 DOI: 10.1104/pp.17.01718] [Citation(s) in RCA: 90] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2017] [Accepted: 05/10/2018] [Indexed: 05/18/2023]
Abstract
Cell walls are crucial for the integrity and function of all land plants and are of central importance in human health, livestock production, and as a source of renewable bioenergy. Many enzymes that mediate the biosynthesis of cell wall polysaccharides are encoded by members of the large cellulose synthase (CesA) gene superfamily. Here, we analyzed 29 sequenced genomes and 17 transcriptomes to revise the phylogeny of the CesA gene superfamily in angiosperms. Our results identify ancestral gene clusters that predate the monocot-eudicot divergence and reveal several novel evolutionary observations, including the expansion of the Poaceae-specific cellulose synthase-like CslF family to the graminids and restiids and the characterization of a previously unreported eudicot lineage, CslM, that forms a reciprocally monophyletic eudicot-monocot grouping with the CslJ clade. The CslM lineage is widely distributed in eudicots, and the CslJ clade, which was thought previously to be restricted to the Poales, is widely distributed in monocots. Our analyses show that some members of the CslJ lineage, but not the newly identified CslM genes, are capable of directing (1,3;1,4)-β-glucan biosynthesis, which, contrary to current dogma, is not restricted to Poaceae.
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Affiliation(s)
- Alan Little
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Julian G Schwerdt
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Neil J Shirley
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Shi F Khor
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Kylie Neumann
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Lisa A O'Donovan
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Jelle Lahnstein
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Helen M Collins
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Marilyn Henderson
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Geoffrey B Fincher
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
| | - Rachel A Burton
- Australian Research Council Centre of Excellence in Plant Cell Walls, School of Agriculture, Food, and Wine, University of Adelaide, Waite Campus, Glen Osmond, South Australia 5064, Australia
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26
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A record of deep-ocean dissolved O 2 from the oxidation state of iron in submarine basalts. Nature 2018; 553:323-327. [PMID: 29310121 DOI: 10.1038/nature25009] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2017] [Accepted: 11/02/2017] [Indexed: 11/08/2022]
Abstract
The oxygenation of the deep ocean in the geological past has been associated with a rise in the partial pressure of atmospheric molecular oxygen (O2) to near-present levels and the emergence of modern marine biogeochemical cycles. It has also been linked to the origination and diversification of early animals. It is generally thought that the deep ocean was largely anoxic from about 2,500 to 800 million years ago, with estimates of the occurrence of deep-ocean oxygenation and the linked increase in the partial pressure of atmospheric oxygen to levels sufficient for this oxygenation ranging from about 800 to 400 million years ago. Deep-ocean dissolved oxygen concentrations over this interval are typically estimated using geochemical signatures preserved in ancient continental shelf or slope sediments, which only indirectly reflect the geochemical state of the deep ocean. Here we present a record that more directly reflects deep-ocean oxygen concentrations, based on the ratio of Fe3+ to total Fe in hydrothermally altered basalts formed in ocean basins. Our data allow for quantitative estimates of deep-ocean dissolved oxygen concentrations from 3.5 billion years ago to 14 million years ago and suggest that deep-ocean oxygenation occurred in the Phanerozoic (541 million years ago to the present) and potentially not until the late Palaeozoic (less than 420 million years ago).
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27
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Hanke UM, Reddy CM, Braun ALL, Coppola AI, Haghipour N, McIntyre CP, Wacker L, Xu L, McNichol AP, Abiven S, Schmidt MWI, Eglinton TI. What on Earth Have We Been Burning? Deciphering Sedimentary Records of Pyrogenic Carbon. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:12972-12980. [PMID: 28994589 DOI: 10.1021/acs.est.7b03243] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Humans have interacted with fire for thousands of years, yet the utilization of fossil fuels marked the beginning of a new era. Ubiquitous in the environment, pyrogenic carbon (PyC) arises from incomplete combustion of biomass and fossil fuels, forming a continuum of condensed aromatic structures. Here, we develop and evaluate 14C records for two complementary PyC molecular markers, benzene polycarboxylic acids (BPCAs) and polycyclic aromatic hydrocarbons (PAHs), preserved in aquatic sediments from a suburban and a remote catchment in the United States (U.S.) from the mid-1700s to 1998. Results show that the majority of PyC stems from local sources and is transferred to aquatic sedimentary archives on subdecadal to millennial time scales. Whereas a small portion stems from near-contemporaneous production and sedimentation, the majority of PyC (∼90%) experiences delayed transmission due to "preaging" on millennial time scales in catchment soils prior to its ultimate deposition. BPCAs (soot) and PAHs (precursors of soot) trace fossil fuel-derived PyC. Both markers parallel historical records of the consumption of fossil fuels in the U.S., yet never account for more than 19% total PyC. This study demonstrates that isotopic characterization of multiple tracers is necessary to constrain histories and inventories of PyC and that sequestration of PyC can markedly lag its production.
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Affiliation(s)
- Ulrich M Hanke
- Department of Geography, University of Zurich , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Christopher M Reddy
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution , 266 Woods Hole Road, Woods Hole, Massachusetts 02543-1050, United States
| | - Ana L L Braun
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution , 266 Woods Hole Road, Woods Hole, Massachusetts 02543-1050, United States
| | - Alysha I Coppola
- Department of Geography, University of Zurich , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Negar Haghipour
- Geological Institute, ETH Zürich , Sonneggstrasse 5, 8092 Zurich, Switzerland
| | - Cameron P McIntyre
- Geological Institute, ETH Zürich , Sonneggstrasse 5, 8092 Zurich, Switzerland
- Laboratory of Ion Beam Physics, ETH Zürich , Otto-Stern-Weg 5, 8093 Zurich, Switzerland
- Scottish Universities Environmental Research Centre , East Kilbride G75 0QF, United Kingdom
| | - Lukas Wacker
- Laboratory of Ion Beam Physics, ETH Zürich , Otto-Stern-Weg 5, 8093 Zurich, Switzerland
| | - Li Xu
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution , 266 Woods Hole Road, Woods Hole, Massachusetts 02543-1050, United States
| | - Ann P McNichol
- Department of Geology and Geophysics, Woods Hole Oceanographic Institution , 266 Woods Hole Road, Woods Hole, Massachusetts 02543-1050, United States
| | - Samuel Abiven
- Department of Geography, University of Zurich , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Michael W I Schmidt
- Department of Geography, University of Zurich , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Timothy I Eglinton
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution , 266 Woods Hole Road, Woods Hole, Massachusetts 02543-1050, United States
- Geological Institute, ETH Zürich , Sonneggstrasse 5, 8092 Zurich, Switzerland
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Scott AC, Chaloner WG, Belcher CM, Roos CI. The interaction of fire and mankind: Introduction. Philos Trans R Soc Lond B Biol Sci 2017; 371:rstb.2015.0162. [PMID: 27216519 DOI: 10.1098/rstb.2015.0162] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2016] [Indexed: 01/28/2023] Open
Abstract
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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Affiliation(s)
- Andrew C Scott
- Department of Earth Sciences, Royal Holloway University of London, Egham TW20 OEX, UK
| | - William G Chaloner
- Department of Earth Sciences, Royal Holloway University of London, Egham TW20 OEX, UK
| | - Claire M Belcher
- wildFIRE Lab, Hatherly Laboratories, University of Exeter, Exeter EX4 4PS, UK
| | - Christopher I Roos
- Department of Anthropology, Southern Methodist University, Dallas, TX 75275-0336, USA
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29
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Laakso TA, Schrag DP. A theory of atmospheric oxygen. GEOBIOLOGY 2017; 15:366-384. [PMID: 28378894 DOI: 10.1111/gbi.12230] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 10/04/2017] [Indexed: 05/18/2023]
Abstract
Geological records of atmospheric oxygen suggest that pO2 was less than 0.001% of present atmospheric levels (PAL) during the Archean, increasing abruptly to a Proterozoic value between 0.1% and 10% PAL, and rising quickly to modern levels in the Phanerozoic. Using a simple model of the biogeochemical cycles of carbon, oxygen, sulfur, hydrogen, iron, and phosphorous, we demonstrate that there are three stable states for atmospheric oxygen, roughly corresponding to levels observed in the geological record. These stable states arise from a series of specific positive and negative feedbacks, requiring a large geochemical perturbation to the redox state to transition from one to another. In particular, we show that a very low oxygen level in the Archean (i.e., 10-7 PAL) is consistent with the presence of oxygenic photosynthesis and a robust organic carbon cycle. We show that the Snowball Earth glaciations, which immediately precede both transitions, provide an appropriate transient increase in atmospheric oxygen to drive the atmosphere either from its Archean state to its Proterozoic state, or from its Proterozoic state to its Phanerozoic state. This hypothesis provides a mechanistic explanation for the apparent synchronicity of the Proterozoic Snowball Earth events with both the Great Oxidation Event, and the Neoproterozoic oxidation.
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Affiliation(s)
- T A Laakso
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
| | - D P Schrag
- Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA, USA
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30
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He T, Lamont BB. Baptism by fire: the pivotal role of ancient conflagrations in evolution of the Earth's flora. Natl Sci Rev 2017. [DOI: 10.1093/nsr/nwx041] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Fire became a defining feature of the Earth's processes as soon as land plants evolved 420 million years ago and has played a major role in shaping the composition and physiognomy of many ecosystems ever since. However, there remains a general lack of appreciation of the place of fire in the origin, evolution, ecology and conservation of the Earth's biodiversity. We review the literature on the presence of fire throughout the Earth's history following the evolution of land plants and examine the evidence for the origin and evolution of adaptive functional traits, biomes and major plant groups in relation to fire. We show that: (1) fire activities have fluctuated throughout geological time due to variations in climate, and more importantly in atmospheric oxygen, as these affected fuel levels and flammability; (2) fire promoted the early evolution and spread of major terrestrial plant groups; (3) fire has shaped the floristics, structure and function of major global biomes; and (4) fire has initiated and maintained the evolution of a wide array of fire-adapted functional traits since the evolution of land plants. We conclude that fire has been a fundamental agent of natural selection on terrestrial plants throughout the history of life on the Earth's land surface. We suggest that a paradigm shift is required to reassess ecological and evolutionary theories that exclude a role for fire, and also there is a need to review fire-suppression policies on ecosystem management and biodiversity conservation in global fire-prone regions.
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Affiliation(s)
- Tianhua He
- Department of Environment and Agriculture, Curtin University, Perth, WA 6845, Australia
| | - Byron B Lamont
- Department of Environment and Agriculture, Curtin University, Perth, WA 6845, Australia
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31
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Waters MT. From little things big things grow: karrikins and new directions in plant development. FUNCTIONAL PLANT BIOLOGY : FPB 2017; 44:373-385. [PMID: 32480571 DOI: 10.1071/fp16405] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2016] [Accepted: 01/16/2017] [Indexed: 06/11/2023]
Abstract
Karrikins are a family of compounds generated via the incomplete combustion of plant matter. Since their discovery as seed germination stimulants in 2004, a great deal has been learned about the chemistry and the biological mode of action of karrikins. Much interest and progress have stemmed from the structural similarity of karrikins to that of strigolactones - the shoot branching hormone. This review will provide a historical account of some of the more significant discoveries in this area of plant biology. It will discuss how the study of these abiotic signalling molecules, combined with advances in our understanding of strigolactones, has led us towards the discovery of new mechanisms that regulate plant growth and development.
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Affiliation(s)
- Mark T Waters
- School of Molecular Sciences and ARC Centre of Excellence in Plant Energy Biology, The University of Western Australia, Perth, WA 6009, Australia. Email
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32
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Daines SJ, Mills BJW, Lenton TM. Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon. Nat Commun 2017; 8:14379. [PMID: 28148950 PMCID: PMC5296660 DOI: 10.1038/ncomms14379] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Accepted: 12/21/2016] [Indexed: 11/08/2022] Open
Abstract
It is unclear why atmospheric oxygen remained trapped at low levels for more than 1.5 billion years following the Paleoproterozoic Great Oxidation Event. Here, we use models for erosion, weathering and biogeochemical cycling to show that this can be explained by the tectonic recycling of previously accumulated sedimentary organic carbon, combined with the oxygen sensitivity of oxidative weathering. Our results indicate a strong negative feedback regime when atmospheric oxygen concentration is of order pO2∼0.1 PAL (present atmospheric level), but that stability is lost at pO2<0.01 PAL. Within these limits, the carbonate carbon isotope (δ13C) record becomes insensitive to changes in organic carbon burial rate, due to counterbalancing changes in the weathering of isotopically light organic carbon. This can explain the lack of secular trend in the Precambrian δ13C record, and reopens the possibility that increased biological productivity and resultant organic carbon burial drove the Great Oxidation Event.
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Affiliation(s)
- Stuart J. Daines
- Earth System Science Group, Department of Geography, College of Life and Environmental Sciences, University of Exeter, Laver Building (Level 7), North Parks Road, Exeter EX4 4QE, UK
| | - Benjamin J. W. Mills
- Earth System Science Group, Department of Geography, College of Life and Environmental Sciences, University of Exeter, Laver Building (Level 7), North Parks Road, Exeter EX4 4QE, UK
- School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK
| | - Timothy M. Lenton
- Earth System Science Group, Department of Geography, College of Life and Environmental Sciences, University of Exeter, Laver Building (Level 7), North Parks Road, Exeter EX4 4QE, UK
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Abstract
The ocean has undergone several profound biogeochemical transformations in its 4-billion-year history, and these were an integral part of the coevolution of life and the planet. This review focuses on changes in ocean redox state as controlled by changes in biological activity, nutrient concentrations, and atmospheric O2. Motivated by disparate interpretations of available geochemical data, we aim to show how quantitative modeling-spanning microbial mats, shelf seas, and the open ocean-can help constrain past ocean biogeochemical redox states and show what caused transformations between them. We outline key controls on ocean redox structure and review pertinent proxies and their interpretation. We then apply this quantitative framework to three key questions: How did the origin of oxygenic photosynthesis transform ocean biogeochemistry? How did the Great Oxidation transform ocean biogeochemistry? And how was ocean biogeochemistry transformed in the Neoproterozoic-Paleozoic?
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Affiliation(s)
- Timothy M Lenton
- Earth System Science Group, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QE, United Kingdom; ,
| | - Stuart J Daines
- Earth System Science Group, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4QE, United Kingdom; ,
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34
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Pereira P, Rein G, Martin D. Past and Present Post-Fire Environments. THE SCIENCE OF THE TOTAL ENVIRONMENT 2016; 573:1275-1277. [PMID: 27369092 DOI: 10.1016/j.scitotenv.2016.05.040] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2016] [Accepted: 05/06/2016] [Indexed: 06/06/2023]
Affiliation(s)
- Paulo Pereira
- Environmental Management Centre, Mykolas Romeris University, Ateities g. 20, 08303 Vilnius, Lithuania
| | - Guillermo Rein
- Department of Mechanical Engineering, Imperial College London, London, UK
| | - Deborah Martin
- U.S. Geological Survey, 3215 Marine Street (E127), Boulder, CO 80303-1066, United States
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35
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Phylogenetic and environmental context of a Tournaisian tetrapod fauna. Nat Ecol Evol 2016; 1:2. [DOI: 10.1038/s41559-016-0002] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2016] [Accepted: 10/11/2016] [Indexed: 11/08/2022]
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Glikson A. Cenozoic mean greenhouse gases and temperature changes with reference to the Anthropocene. GLOBAL CHANGE BIOLOGY 2016; 22:3843-3858. [PMID: 27151305 DOI: 10.1111/gcb.13342] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 04/30/2016] [Indexed: 06/05/2023]
Abstract
Cenozoic greenhouse gases (GHG) variations and warming periods underscore the extreme rates of current climate change, with major implications for the adaptability and survivability of terrestrial and marine habitats. Current rise rate of greenhouse gases, reaching 3.3 ppm CO2 per year during March 2015-2016, is the fastest recorded since the Paleocene-Eocene Thermal Event (PETM) when carbon release to the atmosphere was about an order of magnitude less than at present. The ice core evidence of concentration of (GHG) and temperatures in the atmosphere/ocean/cryosphere system over the last 740 kyr suggests that the rate of rise in GHG over the last ~260 years, CO2 rates rising from 0.94 ppm yr-1 in 1959 (315.97 ppm) to 1.62 ppm yr-1 in 2000 (369.52 ppm) to 3.05 ppm yr-1 in 2015 (400.83 ppm), constitutes a unique spike in the history of the atmosphere. The reliance of pre-740 kyr paleoclimate estimates on multiple proxies, including benthic and plankton fossils, fossil plants, residual organic matter, major and trace elements in fossils, sediments and soils, place limits on the resolution of pre-upper Pleistocene paleoclimate estimates, rendering it likely recorded mean Cenozoic paleoclimate trends may conceal abrupt short-term climate fluctuations. However, as exemplified by the Paleocene-Eocene thermal maximum (PETM) and earlier GHG and temperature spikes associated with major volcanic and asteroid impact events, the long-term residence time of CO2 in the atmosphere extends the signatures of abrupt warming events to within detection limits of multiple paleoproxies. The mean post-1750 temperature rise rate (approximately ~0.0034 °C per yr, or ~0.008 °C per yr where temperature is not masked by sulfur aerosols) exceeds those of the PETM (approximately ~0.0008-0.0015 °C per yr) by an order of magnitude and mean glacial termination warming rates (last glacial termination [LGT] ~ 0.00039; Eemian ~0.0004 °C per yr) by near to an order of magnitude. Consistent with previous interglacial peaks an increasing likelihood of collapse of the Atlantic Meridional Ocean Circulation is threatening a severe stadial event.
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Affiliation(s)
- Andrew Glikson
- Australian National University, Canberra, ACT, 2601, Australia
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Abstract
The progressive oxygenation of the Earth's atmosphere was pivotal to the evolution of life, but the puzzle of when and how atmospheric oxygen (O2) first approached modern levels (∼21%) remains unresolved. Redox proxy data indicate the deep oceans were oxygenated during 435-392 Ma, and the appearance of fossil charcoal indicates O2 >15-17% by 420-400 Ma. However, existing models have failed to predict oxygenation at this time. Here we show that the earliest plants, which colonized the land surface from ∼470 Ma onward, were responsible for this mid-Paleozoic oxygenation event, through greatly increasing global organic carbon burial-the net long-term source of O2 We use a trait-based ecophysiological model to predict that cryptogamic vegetation cover could have achieved ∼30% of today's global terrestrial net primary productivity by ∼445 Ma. Data from modern bryophytes suggests this plentiful early plant material had a much higher molar C:P ratio (∼2,000) than marine biomass (∼100), such that a given weathering flux of phosphorus could support more organic carbon burial. Furthermore, recent experiments suggest that early plants selectively increased the flux of phosphorus (relative to alkalinity) weathered from rocks. Combining these effects in a model of long-term biogeochemical cycling, we reproduce a sustained +2‰ increase in the carbonate carbon isotope (δ(13)C) record by ∼445 Ma, and predict a corresponding rise in O2 to present levels by 420-400 Ma, consistent with geochemical data. This oxygen rise represents a permanent shift in regulatory regime to one where fire-mediated negative feedbacks stabilize high O2 levels.
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38
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Surawski NC, Sullivan AL, Roxburgh SH, Meyer CPM, Polglase PJ. Incorrect interpretation of carbon mass balance biases global vegetation fire emission estimates. Nat Commun 2016; 7:11536. [PMID: 27146785 PMCID: PMC4858743 DOI: 10.1038/ncomms11536] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 04/06/2016] [Indexed: 11/25/2022] Open
Abstract
Vegetation fires are a complex phenomenon in the Earth system with many global impacts, including influences on global climate. Estimating carbon emissions from vegetation fires relies on a carbon mass balance technique that has evolved with two different interpretations. Databases of global vegetation fire emissions use an approach based on ‘consumed biomass', which is an approximation to the biogeochemically correct ‘burnt carbon' approach. Here we show that applying the ‘consumed biomass' approach to global emissions from vegetation fires leads to annual overestimates of carbon emitted to the atmosphere by 4.0% or 100 Tg compared with the ‘burnt carbon' approach. The required correction is significant and represents ∼9% of the net global forest carbon sink estimated annually. Vegetation fire emission studies should use the ‘burnt carbon' approach to quantify and understand the role of this burnt carbon, which is not emitted to the atmosphere, as a sink enriched in carbon. Vegetation fires contribute to global carbon emissions, but uncertainty exists due to inconsistencies in the treatment of post-burn combustion. Here, it is shown that the ‘consumed biomass' approach overestimates emissions by 4%, which can be corrected using an alternative ‘burnt carbon' method.
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Affiliation(s)
- N C Surawski
- CSIRO Agriculture, GPO Box 1700, Canberra, Acton 2601, Australian Capital Territory, Australia
| | - A L Sullivan
- CSIRO Land and Water, GPO Box 1700, Canberra, Acton 2601, Australian Capital Territory, Australia
| | - S H Roxburgh
- CSIRO Land and Water, GPO Box 1700, Canberra, Acton 2601, Australian Capital Territory, Australia
| | - C P Mick Meyer
- CSIRO Oceans and Atmosphere, 107-121 Station Street, Aspendale, Victoria 3195, Australia
| | - P J Polglase
- CSIRO Land and Water, GPO Box 1700, Canberra, Acton 2601, Australian Capital Territory, Australia
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Fischer WW, Hemp J, Valentine JS. How did life survive Earth's great oxygenation? Curr Opin Chem Biol 2016; 31:166-78. [PMID: 27043270 DOI: 10.1016/j.cbpa.2016.03.013] [Citation(s) in RCA: 64] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Revised: 03/11/2016] [Accepted: 03/15/2016] [Indexed: 12/26/2022]
Abstract
Life on Earth originated and evolved in anoxic environments. Around 2.4 billion-years-ago, ancestors of Cyanobacteria invented oxygenic photosynthesis, producing substantial amounts of O2 as a byproduct of phototrophic water oxidation. The sudden appearance of O2 would have led to significant oxidative stress due to incompatibilities with core cellular biochemical processes. Here we examine this problem through the lens of Cyanobacteria-the first taxa to observe significant fluxes of intracellular dioxygen. These early oxygenic organisms likely adapted to the oxidative stress by co-opting preexisting systems (exaptation) with fortuitous antioxidant properties. Over time more advanced antioxidant systems evolved, allowing Cyanobacteria to adapt to an aerobic lifestyle and become the most important environmental engineers in Earth history.
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Affiliation(s)
- Woodward W Fischer
- Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States.
| | - James Hemp
- Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States
| | - Joan Selverstone Valentine
- Division of Geological & Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, United States; Department of Chemistry and Biochemistry, UCLA, Los Angeles, CA 90095, United States.
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40
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Douglas MR, Davis MA, Amarello M, Smith JJ, Schuett GW, Herrmann HW, Holycross AT, Douglas ME. Anthropogenic impacts drive niche and conservation metrics of a cryptic rattlesnake on the Colorado Plateau of western North America. ROYAL SOCIETY OPEN SCIENCE 2016; 3:160047. [PMID: 27152218 PMCID: PMC4852641 DOI: 10.1098/rsos.160047] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2016] [Accepted: 03/31/2016] [Indexed: 06/05/2023]
Abstract
Ecosystems transition quickly in the Anthropocene, whereas biodiversity adapts more slowly. Here we simulated a shifting woodland ecosystem on the Colorado Plateau of western North America by using as its proxy over space and time the fundamental niche of the Arizona black rattlesnake (Crotalus cerberus). We found an expansive (= end-of-Pleistocene) range that contracted sharply (= present), but is blocked topographically by Grand Canyon/Colorado River as it shifts predictably northwestward under moderate climate change (= 2080). Vulnerability to contemporary wildfire was quantified from available records, with forested area reduced more than 27% over 13 years. Both 'ecosystem metrics' underscore how climate and wildfire are rapidly converting the Plateau ecosystem into novel habitat. To gauge potential effects on C. cerberus, we derived a series of relevant 'conservation metrics' (i.e. genetic variability, dispersal capacity, effective population size) by sequencing 118 individuals across 846 bp of mitochondrial (mt)DNA-ATPase8/6. We identified five significantly different clades (net sequence divergence = 2.2%) isolated by drainage/topography, with low dispersal (F ST = 0.82) and small sizes (2N ef = 5.2). Our compiled metrics (i.e. small-populations, topographic-isolation, low-dispersal versus conserved-niche, vulnerable-ecosystem, dispersal barriers) underscore the susceptibility of this woodland specialist to a climate and wildfire tandem. We offer adaptive management scenarios that may counterbalance these metrics and avoid the extirpation of this and other highly specialized, relictual woodland clades.
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Affiliation(s)
- M. R. Douglas
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
| | - M. A. Davis
- Illinois Natural History Survey, University of Illinois, Champaign, IL, USA
| | - M. Amarello
- Life Sciences, Arizona State University, Tempe, AZ, USA
| | - J. J. Smith
- Life Sciences, Arizona State University, Tempe, AZ, USA
| | | | - H.-W. Herrmann
- Natural Resources and Environment, University of Arizona, Tucson, AZ, USA
| | | | - M. E. Douglas
- Department of Biological Sciences, University of Arkansas, Fayetteville, AR, USA
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41
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Bateman RM, Stevens LG, Hilton J. Stratigraphy, palaeoenvironments and palaeoecology of the Loch Humphrey Burn lagerstätte and other Mississippian palaeobotanical localities of the Kilpatrick Hills, southwest Scotland. PeerJ 2016; 4:e1700. [PMID: 26925325 PMCID: PMC4768698 DOI: 10.7717/peerj.1700] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/27/2016] [Indexed: 11/20/2022] Open
Abstract
Background and Aims. The largely Mississippian strata of the Kilpatrick Hills, located at the western end of the Scottish Midland Valley, enclose several macrofossil floras that together contain ca 21 organ-species of permineralised plants and ca 44 organ-species of compressed plants, here estimated to represent 25 whole-plant species (Glenarbuck = nine, Loch Humphrey Burn Lower = 11, Upper = seven). The most significant locality is the internationally important volcanigenic sequence that is reputedly intercalated within the Clyde Plateau Lava Formation at Loch Humphrey Burn, where ca 30 m of reworked tuffs and other clastic sediments enclose one of the world’s most important terrestrial lagerstätten of this period. We here explore the palaeoecology and palaeoenvironments of the locality, and elucidate its controversial age. Methods. Repeated re-excavation of key exposures allowed recognition of five main depositional units, differing in thickness from 4 m to 12 m. It also permitted detailed sampling for plant macrofossils and microfossils throughout the succession. Several approaches are integrated to re-assess the taphonomy and preservation of these exceptional plant fossils. Key Results. The deposits are rich in taxonomically diverse miospores and in toto contain at least six well-developed compression floras, together with two beds yielding nodules that enclose well-researched anatomically preserved plants permineralised in calcite. Bulk geochemistry shows that the upper nodules formed by migration of Ca with subordinate Mn and Na. Some phylogenetically important plant fossils recovered in the early 20th century have been traced to their source horizons. Trends in relative proportions of macrofossil and microfossil taxa through the sequence are only moderately congruent, perhaps reflecting the likelihood that microfossils sample the regional rather than the local flora. Conclusions. The Loch Humphrey Burn sequence encompasses a wide range of depositional environments that intercalates high-energy fluvial channels (possibly developed during flash floods in a seasonally arid environment) with lower energy flood plains and a brief lacustrine interval; all yield macrofloras typically dominated by allochthonous pteridosperms. The uppermost unit represents clastic swamps dominated by (hypo)autochthonous lycopsids and ferns s.l., and is tentatively correlated with the entire—reputedly mid-Visean—exposure at nearby Glenarbuck. Other nearby localities with rooted tree-lycopsids appear to have immediately pre-dated the onset of regional volcanism. These interpretations allow revised provenancing and dating of historical collections of key plant fossils. The late Tournaisian date previously attributed on palynological evidence to the lowest unit at Loch Humphrey Burn appears increasingly improbable when our re-appraisal of the macrofloras and microfloras is placed in the context of (a) statistical comparison with other permineralised Mississippian assemblages and (b) recent stratigraphic and geochronologic studies in the region; rather, we ascribe the entire Kilpatrick Hills sequence to the mid-Visean. Stratigraphic and palaeoenvironmental interpretations of the Mississippian rocks of the Kilpatrick Hills have especially profound implications for our understanding of the physical evolution of Scotland during the Variscan orogeny and formation of Pangea.
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Affiliation(s)
| | - Liadan G Stevens
- Earth Sciences, Natural History Museum, London, United Kingdom; School of Geography, Earth and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Jason Hilton
- School of Geography, Earth and Environmental Sciences, University of Birmingham , Birmingham , United Kingdom
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42
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43
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Shih PM, Occhialini A, Cameron JC, Andralojc PJ, Parry MAJ, Kerfeld CA. Biochemical characterization of predicted Precambrian RuBisCO. Nat Commun 2016; 7:10382. [PMID: 26790750 PMCID: PMC4735906 DOI: 10.1038/ncomms10382] [Citation(s) in RCA: 76] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2015] [Accepted: 12/04/2015] [Indexed: 01/02/2023] Open
Abstract
The antiquity and global abundance of the enzyme, RuBisCO, attests to the crucial and longstanding role it has played in the biogeochemical cycles of Earth over billions of years. The counterproductive oxygenase activity of RuBisCO has persisted over billions of years of evolution, despite its competition with the carboxylase activity necessary for carbon fixation, yet hypotheses regarding the selective pressures governing RuBisCO evolution have been limited to speculation. Here we report the resurrection and biochemical characterization of ancestral RuBisCOs, dating back to over one billion years ago (Gyr ago). Our findings provide an ancient point of reference revealing divergent evolutionary paths taken by eukaryotic homologues towards improved specificity for CO2, versus the evolutionary emphasis on increased rates of carboxylation observed in bacterial homologues. Consistent with these distinctions, in vivo analysis reveals the propensity of ancestral RuBisCO to be encapsulated into modern-day carboxysomes, bacterial organelles central to the cyanobacterial CO2 concentrating mechanism.
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Affiliation(s)
- Patrick M. Shih
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA
| | - Alessandro Occhialini
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK
| | - Jeffrey C. Cameron
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA
| | - P John Andralojc
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK
| | - Martin A. J. Parry
- Department of Plant Biology and Crop Science, Rothamsted Research, Harpenden, Herts AL5 2JQ, UK
- Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1, 4YQ, UK
| | - Cheryl A. Kerfeld
- Department of Plant and Microbial Biology, University of California, Berkeley, California 94720-3102, USA
- Department of Biochemistry and Molecular Biology, DOE Plant Research Laboratories, Michigan State University, East Lansing, Michigan 488242, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
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Petrology, Palynology, and Geochemistry of Gray Hawk Coal (Early Pennsylvanian, Langsettian) in Eastern Kentucky, USA. MINERALS 2015. [DOI: 10.3390/min5030511] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Poulsen CJ, Tabor C, White JD. CLIMATE CHANGE. Long-term climate forcing by atmospheric oxygen concentrations. Science 2015; 348:1238-41. [PMID: 26068848 DOI: 10.1126/science.1260670] [Citation(s) in RCA: 66] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2014] [Accepted: 05/05/2015] [Indexed: 11/02/2022]
Abstract
The percentage of oxygen in Earth's atmosphere varied between 10% and 35% throughout the Phanerozoic. These changes have been linked to the evolution, radiation, and size of animals but have not been considered to affect climate. We conducted simulations showing that modulation of the partial pressure of oxygen (pO2), as a result of its contribution to atmospheric mass and density, influences the optical depth of the atmosphere. Under low pO2 and a reduced-density atmosphere, shortwave scattering by air molecules and clouds is less frequent, leading to a substantial increase in surface shortwave forcing. Through feedbacks involving latent heat fluxes to the atmosphere and marine stratus clouds, surface shortwave forcing drives increases in atmospheric water vapor and global precipitation, enhances greenhouse forcing, and raises global surface temperature. Our results implicate pO2 as an important factor in climate forcing throughout geologic time.
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Affiliation(s)
- Christopher J Poulsen
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA.
| | - Clay Tabor
- Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, USA
| | - Joseph D White
- Department of Biology, Baylor University, Waco, TX 76798, USA
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Abstract
The lack of fossil tetrapod bearing deposits in the earliest Carboniferous (‘Romer’s Gap’) has provoked some recent discussions regarding the proximal cause, with three explanations being offered: environmental, taphonomic, and collection failure. One of the few, and earliest, windows into this time is the locality of Blue Beach exposed in the Tournaisian deposits at Horton Bluff lying along the Avon River near Hantsport, Nova Scotia, Canada. This locality has long been known but, because the fossils were deposited in high energy settings they are almost always disarticulated, so the fauna has not been described in detail. Recent intensive collection has revealed a diverse assemblage of material, including for the first time associated elements, which permits an evaluation of the faunal constituents at the locality. Although not diagnosable to a fine taxonomic level, sufficient apomorphies are present to identify representatives from numerous clades known from more complete specimens elsewhere. The evidence suggests a diverse fauna was present, including whatcheeriids and embolomeres. A single humerus previously had been attributed to a colosteid, but there is some uncertainty with this identification. Additional elements suggest the presence of taxa otherwise only known from the late Devonian. Depositional biases at the locality favor tetrapod fossils from larger individuals, but indirect evidence from trackways and tantalizing isolated bones evidences the presence of small taxa that remain to be discovered. The fossils from Blue Beach demonstrate that when windows into the fauna of ‘Romer’s Gap’ are found a rich diversity of tetrapods will be shown to be present, contra arguments that suggested this hiatus in the fossil record was due to extrinsic factors such as atmospheric oxygen levels. They also show that the early tetrapod fauna is not easily divisible into Devonian and Carboniferous faunas, suggesting that some tetrapods passed through the end Devonian extinction event unaffected.
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Iglesias V, Yospin GI, Whitlock C. Reconstruction of fire regimes through integrated paleoecological proxy data and ecological modeling. FRONTIERS IN PLANT SCIENCE 2015; 5:785. [PMID: 25657652 PMCID: PMC4302794 DOI: 10.3389/fpls.2014.00785] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Accepted: 12/17/2014] [Indexed: 06/04/2023]
Abstract
Fire is a key ecological process affecting vegetation dynamics and land cover. The characteristic frequency, size, and intensity of fire are driven by interactions between top-down climate-driven and bottom-up fuel-related processes. Disentangling climatic from non-climatic drivers of past fire regimes is a grand challenge in Earth systems science, and a topic where both paleoecology and ecological modeling have made substantial contributions. In this manuscript, we (1) review the use of sedimentary charcoal as a fire proxy and the methods used in charcoal-based fire history reconstructions; (2) identify existing techniques for paleoecological modeling; and (3) evaluate opportunities for coupling of paleoecological and ecological modeling approaches to better understand the causes and consequences of past, present, and future fire activity.
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Affiliation(s)
- Virginia Iglesias
- Montana Institute on Ecosystems, Montana State UniversityBozeman, MT, USA
| | - Gabriel I. Yospin
- Montana Institute on Ecosystems, Montana State UniversityBozeman, MT, USA
| | - Cathy Whitlock
- Montana Institute on Ecosystems, Montana State UniversityBozeman, MT, USA
- Department of Earth Sciences, Montana State UniversityBozeman, MT, USA
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Glasspool IJ, Scott AC, Waltham D, Pronina N, Shao L. The impact of fire on the Late Paleozoic Earth system. FRONTIERS IN PLANT SCIENCE 2015; 6:756. [PMID: 26442069 PMCID: PMC4585212 DOI: 10.3389/fpls.2015.00756] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Accepted: 09/04/2015] [Indexed: 05/22/2023]
Abstract
Analyses of bulk petrographic data indicate that during the Late Paleozoic wildfires were more prevalent than at present. We propose that the development of fire systems through this interval was controlled predominantly by the elevated atmospheric oxygen concentration (p(O2)) that mass balance models predict prevailed. At higher levels of p(O2), increased fire activity would have rendered vegetation with high-moisture contents more susceptible to ignition and would have facilitated continued combustion. We argue that coal petrographic data indicate that p(O2) rather than global temperatures or climate, resulted in the increased levels of wildfire activity observed during the Late Paleozoic and can, therefore, be used to predict it. These findings are based upon analyses of charcoal volumes in multiple coals distributed across the globe and deposited during this time period, and that were then compared with similarly diverse modern peats and Cenozoic lignites and coals. Herein, we examine the environmental and ecological factors that would have impacted fire activity and we conclude that of these factors p(O2) played the largest role in promoting fires in Late Paleozoic peat-forming environments and, by inference, ecosystems generally, when compared with their prevalence in the modern world.
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Affiliation(s)
- Ian J. Glasspool
- Department of Geology, Colby CollegeWaterville, ME, USA
- Science and Education, Field Museum of Natural HistoryChicago, IL, USA
| | - Andrew C. Scott
- Department of Earth Sciences, Royal Holloway University of LondonEgham, Surrey, UK
- *Correspondence: Andrew C. Scott, Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK,
| | - David Waltham
- Department of Earth Sciences, Royal Holloway University of LondonEgham, Surrey, UK
| | | | - Longyi Shao
- State Key Laboratory of Coal Resources and Safe Mining, and School of Geosciences and Survey Engineering, China University of Mining and TechnologyBeijing, China
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The largest Silurian vertebrate and its palaeoecological implications. Sci Rep 2014; 4:5242. [PMID: 24921626 PMCID: PMC4054400 DOI: 10.1038/srep05242] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2014] [Accepted: 05/23/2014] [Indexed: 12/03/2022] Open
Abstract
An apparent absence of Silurian fishes more than half-a-metre in length has been viewed as evidence that gnathostomes were restricted in size and diversity prior to the Devonian. Here we describe the largest pre-Devonian vertebrate (Megamastax amblyodus gen. et sp. nov.), a predatory marine osteichthyan from the Silurian Kuanti Formation (late Ludlow, ~423 million years ago) of Yunnan, China, with an estimated length of about 1 meter. The unusual dentition of the new form suggests a durophagous diet which, combined with its large size, indicates a considerable degree of trophic specialisation among early osteichthyans. The lack of large Silurian vertebrates has recently been used as constraint in palaeoatmospheric modelling, with purported lower oxygen levels imposing a physiological size limit. Regardless of the exact causal relationship between oxygen availability and evolutionary success, this finding refutes the assumption that pre-Emsian vertebrates were restricted to small body sizes.
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Klebsormidium flaccidum genome reveals primary factors for plant terrestrial adaptation. Nat Commun 2014; 5:3978. [PMID: 24865297 PMCID: PMC4052687 DOI: 10.1038/ncomms4978] [Citation(s) in RCA: 398] [Impact Index Per Article: 39.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2014] [Accepted: 04/28/2014] [Indexed: 01/20/2023] Open
Abstract
The colonization of land by plants was a key event in the evolution of life. Here we report
the draft genome sequence of the filamentous terrestrial alga Klebsormidium flaccidum
(Division Charophyta, Order Klebsormidiales) to elucidate the early transition step from
aquatic algae to land plants. Comparison of the genome sequence with that of other algae and
land plants demonstrate that K. flaccidum acquired many genes specific to land
plants. We demonstrate that K. flaccidum indeed produces several plant hormones and
homologues of some of the signalling intermediates required for hormone actions in higher
plants. The K. flaccidum genome also encodes a primitive system to protect against
the harmful effects of high-intensity light. The presence of these plant-related systems in
K. flaccidum suggests that, during evolution, this alga acquired the fundamental
machinery required for adaptation to terrestrial environments. Plant colonization of land is an important evolutionary event. Here, the
authors sequence the genome of a filamentous terrestrial alga and, through a comparative
analysis with related algae and land plant species, provide insight into how aquatic algae
adapted to terrestrial environments.
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