Charcoal Abundance Research Articles

Recurrent palaeo-wildfires in a Cisuralian coal seam: A palaeobotanical view on high-inertinite coals from the Lower Permian of the Paraná Basin, Brazil.

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.

Sedimentary record from Patagonia, southern Chile supports cosmic-impact triggering of biomass burning, climate change, and megafaunal extinctions at 12.8\u2009ka

The Younger Dryas (YD) impact hypothesis posits that fragments of a large, disintegrating asteroid/comet struck North America, South America, Europe, and western Asia ~12,800 years ago. Multiple airbursts/impacts produced the YD boundary layer (YDB), depositing peak concentrations of platinum, high-temperature spherules, meltglass, and nanodiamonds, forming an isochronous datum at >50 sites across ~50 million km² of Earth’s surface. This proposed event triggered extensive biomass burning, brief impact winter, YD climate change, and contributed to extinctions of late Pleistocene megafauna. In the most extensive investigation south of the equator, we report on a ~12,800-year-old sequence at Pilauco, Chile (~40°S), that exhibits peak YD boundary concentrations of platinum, gold, high-temperature iron- and chromium-rich spherules, and native iron particles rarely found in nature. A major peak in charcoal abundance marks an intense biomass-burning episode, synchronous with dramatic changes in vegetation, including a high-disturbance regime, seasonality in precipitation, and warmer conditions. This is anti-phased with northern-hemispheric cooling at the YD onset, whose rapidity suggests atmospheric linkage. The sudden disappearance of megafaunal remains and dung fungi in the YDB layer at Pilauco correlates with megafaunal extinctions across the Americas. The Pilauco record appears consistent with YDB impact evidence found at sites on four continents.

Позднеголоценовая динамика растительного покрова и увлажнённости климата юго-восточного сектора Западно-Сибирской равнины по данным палинологического и ризоподного исследований торфяных отложений

Позднеголоценовая динамика растительного покрова и увлажнённости климата юго-восточного сектора Западно-Сибирской равнины по данным палинологического и ризоподного исследований торфяных отложений

Reconstructing past fire temperatures from ancient charcoal material

Charcoal abundance measurements are commonly used to estimate fire activity in palaeoecological studies; however, fire temperature is not directly measured. Reconstructing fire temperature is desirable because the ecological response to fire is, in part, a function of the temperature of the fire, e.g. crown fires >500 °C, slash and burn agriculture <400 °C. Here, we determine whether charcoal chemistry, as inferred from Fourier Transformed Infrared Spectroscopy (FTIR), is a reliable proxy for fire (combustion) temperature. We generated reference charcoal material from a grass species (Panicum capillare) and a woody species (Alnus glutinosa), prepared with three different laboratory treatments (untreated, water, and hydrogen peroxide), and heated to six temperatures (200–700 °C). We picked individual charcoal fragments from lake sediments deposited between ca. 1400 and 450 years ago to compare with the reference charcoal material. FTIR spectra were used to infer the chemical composition of both modern reference and ancient charcoal. The FTIR spectra of the datasets were analysed with model-based clustering.The inferred chemistry of the reference charcoal from the FTIR spectra was in broad agreement with previous studies, and the model-based clustering algorithms were able to distinguish clusters based on the temperature to which the material was heated. The FTIR spectra from the ancient charcoal fragments fell within the range of variability of the modern reference charcoal, allowing for successful classification of the fragments created by fires in the long distant past. We used a probability density function of each statistically significant cluster to infer combustion temperatures for the ancient charcoal fragments. Our results suggest that the use of FTIR analysis of charcoal can differentiate low (200 °C–300 °C), medium (400 °C–600 °C) and high (600 °C–700 °C) temperature fires. Our findings pave the way for generating a better understanding of the role of fire in Earth's system through time.

Late Quaternary vegetation, climate, and fire history of the Southeast Atlantic Coastal Plain based on a 30,000-yr multi-proxy record from White Pond, South Carolina, USA

AbstractThe patterns and drivers of late Quaternary vegetation dynamics in the southeastern United States are poorly understood due to low site density, problematic chronologies, and a paucity of independent paleoclimate proxy records. We present a well-dated (15 accelerator mass spectrometry14C dates) 30,000-yr record from White Pond, South Carolina that consists of high-resolution analyses of fossil pollen, macroscopic charcoal, andSporormiellaspores, and an independent paleotemperature reconstruction based on branched glycerol dialkyl tetraethers. Between 30,000 and 20,000 cal yr BP, openPinus-Piceaforest grew under cold and dry conditions; elevatedQuercusbefore 26,000 cal yr BP, however, suggest warmer conditions in the Southeast before the last glacial maximum, possibly corresponding to regionally warmer conditions associated with Heinrich event H2. Warming between 19,700 and 10,400 cal yr BP was accompanied by a transition from conifer-dominated to mesic hardwood forest.Sporormiellaspores were not detected and charcoal was low during the late glacial period, suggesting megaherbivore grazers and fire were not locally important agents of vegetation change.Pinusreturned to dominance during the Holocene, with step-like increases inPinusat 10,400 and 6400 cal yr BP, while charcoal abundance increased tenfold, likely due to increased biomass burning associated with warmer conditions. Low-intensity surface fires increased after 1200 cal yr BP, possibly related to the establishment of the Mississippian culture in the Southeast.

A New High-Paleolatitude Late Permian Permineralized Peat Flora from the Sydney Basin, Australia

Premise of research. Permineralized peats are prized for hosting three-dimensionally preserved plant remains that provide insights into fossil plant anatomy and the composition of coal-forming ecosystems. A new record of siliceous permineralized peat is documented from a Lopingian-aged (upper Permian) strata from the southern Sydney Basin. It represents the fifth Permian permineralized peat identified from eastern Australia.Methodology. The single permineralized peat block was cut into smaller blocks, and both cellulose acetate peels and standard thin sections were prepared for study using transmitted light microscopy. Quantitative analysis of the peat was carried out using point counts perpendicular to bedding. One block examined using synchrotron X-ray computed tomography (CT) revealed the three-dimensional anatomy of abundant fossil seeds.Pivotal results. The peat contains a plant assemblage dominated by glossopterid leaves, seeds, and axes; although degraded, probable pteridophyte remains represent a significant subsidiary component of the assemblage. A new leaf form (Glossopteris thirroulensis McLoughlin et Mays sp. nov.) and a new type of seed (Illawarraspermum ovatum McLoughlin et Mays gen. et sp. nov.) are described. Leaf-, wood/seed-, and fine detritus-rich organic microfacies with gradational boundaries are evident within the peat.Conclusions. Regular growth rings in the small permineralized axes, together with the occurrence of autumnal mats of glossopterid leaves, signify a strongly seasonal climate. The presence of abundant charcoal in the peat indicates that fire was a significant influence on the high-paleolatitude mire ecosystem. Differentiation of organic microfacies within the peat profile indicates subtle variation in the contribution of plant components to the peat through time. The absence of mineral grains in thin section and CT, together with the presence of authigenic sulfides, indicates accumulation of organic matter in a stagnant mire away from the influence of clastic input.

Identifying the ‘savanna’ signature in lacustrine sediments in northern Australia

This study reports palynological and geochemical results for modern and ancient sediments from 19 lakes on a rainfall gradient (784–1880 mm), across a range of savannas in Northern Australia. All proxies varied significantly across the range of sites examined, providing a robust envelope of values that can reliably be employed to identify a savanna signature in the sedimentary record. While the results indicate it is possible to identify a savanna, we found only three statistically significant relationships between any proxy measured in surface sediments and the major climate driver of savanna vegetation composition (rainfall amount). This is because edaphic factors play a dominant role in determining vegetation composition and also potentially because of the impact of land use change.Measures of fire determined by charcoal counting were positively correlated with geochemical measures of pyrogenic carbon abundance, suggesting both record a similar signal. While measures of fire incidence were not correlated with rainfall, there was a significant positive correlation between charcoal abundance and number of fires early in the dry season, suggesting that charcoal abundance is controlled more by the number/timing of fires than climate. There was also a significant correlation between the δ13C-value of pyrogenic carbon and tree:grass ratio derived from palynological indicators, indicating that the δ13C-value of PyC is a reliable indicator of savanna ‘woodiness’. Comparison of the carbon isotope composition of total organic carbon, PyC and n-alkanes between modern and Holocene sediments suggest that the savannas of the region have remained either similar in ‘woodiness’ or have thickened over the last millennia.

The extraterrestrial impact evidence at the Palaeocene–Eocene boundary and sequence of environmental change on the continental shelf

We have identified clear evidence of an extraterrestrial impact within the onset of the carbon isotope excursion (CIE) that defines the Palaeocene-Eocene (P-E) boundary hyperthermal event (approx. 56 Ma) from several sites on the eastern Atlantic Coastal Plain and offshore. We review and update the state of the evidence for an impact at the P-E boundary, including a K-Ar cooling age of the ejecta that is indistinguishable from the depositional age at the P-E, which establishes the ejecta horizon as an isochronous stratigraphic indicator at the P-E. Immediately above the ejecta peak at the base of the coastal plain Marlboro Clay unit, we identify a sharp increase in charcoal abundance coincident with the previously observed dramatic increase in magnetic nanoparticles of soil pyrogenic origin. We therefore revisit the observed sequence of events through the P-E boundary on the western Atlantic Coastal Plain, showing that an extraterrestrial impact led to wildfires, landscape denudation and deposition of the thick Marlboro Clay, whose base coincides with the spherule horizon and CIE onset. The Sr/Ca ratio of the spherules indicates that the carbon responsible for the onset may be vaporized CaCO3 target rock mixed with isotopically light carbon from the impactor or elsewhere. Crucially, we do not argue that the impact was responsible for the full manifestation of the CIE observed globally (onset to recovery approx. 170 kyr), rather that a rapid onset was triggered by the impact and followed by additional carbon from other processes such as the eruption of the North Atlantic Igneous Province. Such a scenario agrees well with recent modelling work, though it should be revisited more explicitly.This article is part of a discussion meeting issue 'Hyperthermals: rapid and extreme global warming in our geological past'.

Columbus' environmental impact in the New World: Land use change in the Yaque River valley, Dominican Republic.

Columbus’ arrival in the New World in AD 1492 on the northern coast of Hispaniola was followed by a suite of changes in land-use. We reconstruct environmental change from a 225-cm-long sediment core from site Los Indios from an abandoned and sediment-filled meander of the Yaque River, Cibao Valley, northeastern Dominican Republic. The sediment record starts ca. AD 195 (ca. 1755 cal. yr BP) and the history of the meander infill was monitored by changing grain size distributions, organic matter concentration and pollen from wetland plants. From ca. AD 200 to ca. AD 1525, the pollen record indicates a diverse forest assemblage; however, the presence of pollen from potential crop plants suggest nearby small-scale subsistence crop cultivation. More abundant charcoal after ca. AD 1410 shows Amerindians increasingly used fire. The record of grain size distributions shows that the meander was temporarily part of a low energetic drainage system in which bedload and suspended sediments accumulated. After European colonization of Hispaniola increasing spores of coprophilous fungi evidence that Europeans had introduced during the first decades of colonization cattle in the Cibao Valley which gradually resulted in more open forest. The charcoal record around ca. AD 1650 reflects intensive forest clearing, suggesting that small-scale Pre-Colonial practice of crop cultivation became replaced by large-scale agriculture on the moist and nutrient rich soils along the Yaque River. Further deforestation and signals of erosion suggest that the population of colonists and introduced enslaved labour force must have increased rapidly. After ca. AD 1740 charcoal influx decreased suggesting that last deforestation activities used selective cutting to produce fire wood and timber for construction, rather than burning forest in situ. Two centuries after European colonization, by the 18th century, land-use within the Cibao Valley had become a balance between substantial livestock and crop cultivation (pollen grains have evidenced cereals, maize, and potentially also sugar cane, amaranthaceous crops and tobacco). After ca. AD 1950, swamp vegetation of Typha and Cyperaceae decreased, pointing to an almost fully terrestrialized meander with only few bodies of standing water, reflecting the present-day setting. This multiproxy reconstruction of anthropogenic environmental change shows a clear differentiation between an immediate introduction of livestock and after some 150 years the development of a European style agriculture, providing a context for archaeological investigations.

Woodlands and steppes: Pleistocene vegetation in Yakutia's most continental part recorded in the Batagay permafrost sequence

Based on fossil organism remains including plant macrofossils, charcoal, pollen, and invertebrates preserved in syngenetic deposits of the Batagay permafrost sequence in the Siberian Yana Highlands, we reconstructed the environmental history during marine isotope stages (MIS) 6 to 2. Two fossil assemblages, exceptionally rich in plant remains, allowed for a detailed description of the palaeo-vegetation during two climate extremes of the Late Pleistocene, the onset of the last glacial maximum (LGM) and the last interglacial. In addition, altogether 41 assemblages were used to outline the vegetation history since the penultimate cold stage of MIS 6. Accordingly, meadow steppes analogue to modern communities of the phytosociological order Festucetalia lenensis formed the primary vegetation during the Saalian and Weichselian cold stages. Cold-resistant tundra-steppe communities (Carici rupestris-Kobresietea bellardii) as they occur above the treeline today were, in contrast to more northern locations, mostly lacking. During the last interglacial, open coniferous woodland similar to modern larch taiga was the primary vegetation at the site. Abundant charcoal indicates wildfire events during the last interglacial. Zoogenic disturbances of the local vegetation were indicated by the presence of ruderal plants, especially by abundant Urtica dioica, suggesting that the area was an interglacial refugium for large herbivores. Meadow steppes, which formed the primary vegetation during cold stages and provided potentially suitable pastures for herbivores, were a significant constituent of the plant cover in the Yana Highlands also under the full warm stage conditions of the last interglacial. Consequently, meadow steppes occurred in the Yana Highlands during the entire investigated timespan from MIS 6 to MIS 2 documenting a remarkable environmental stability. Thus, the proportion of meadow steppe vegetation merely shifted in response to the respectively prevailing climatic conditions. Their persistence indicates low precipitation and a relatively warm growing season throughout and beyond the late Pleistocene. The studied fossil record also proves that modern steppe occurrences in the Yana Highlands did not establish as late as in the Holocene but instead are relicts of a formerly continuous steppe belt extending from Central Siberia to Northeast Yakutia during the Pleistocene. The persistence of plants and invertebrates characteristic of meadow steppe vegetation in interior Yakutia throughout the late Quaternary indicates climatic continuity and documents the suitability of this region as a refugium also for other organisms of the Pleistocene mammoth steppe including the iconic large herbivores.

Peatland carbon stocks and burn history: Blanket bog peat core evidence highlights charcoal impacts on peat physical properties and long‐term carbon storage

Peatlands are globally important carbon stores, yet both natural and human impacts can influence peatland carbon accumulation. While changes in climate can alter peatland water tables leading to changes in peat decomposition, managed burning of vegetation has also been claimed to reduce peat accumulation. Particularly in the UK, blanket bog peatlands are rotationally burned to encourage heather re‐growth on grouse shooting estates. However, the evidence of burning impacts on peat carbon stocks is very limited and contradictory. We assessed peat carbon accumulation over the last few hundred years in peat cores from three UK blanket bog sites under rotational grouse moor burn management. High resolution (0.5 cm) peat core analysis included dating based on spheroidal carbonaceous particles, determining fire frequency based on macro‐charcoal counts and assessing peat properties such as carbon content and bulk density. All sites showed considerable net carbon accumulation during active grouse moor management periods. Averaged over the three sites, burns were more frequent, and carbon accumulation rates were also higher, over the period since 1950 than in the period 1700–1950. Carbon accumulation rates during the periods 1950–2015 and 1700–1850 were greater on the most frequently burnt site, which was linked to bulk density and carbon accumulation rates showing a positive relationship with charcoal abundance. Charcoal input from burning was identified as a potentially crucial component in explaining reported differences in burning impacts on peat carbon accumulation, as assessed by carbon fluxes or stocks. Both direct and indirect charcoal impacts on decomposition processes are discussed to be important factors, namely charcoal production converting otherwise decomposable carbon into an inert carbon pool, increasing peat bulk density, altering peat moisture and possibly negative impacts on soil microbial activity. This study highlights the value of peat core records in understanding management impacts on peat accumulation and carbon storage in peatlands.

Natural and Anthropogenic Changes in the Soils and Environment of the Moskva River Floodplain in the Holocene: Pedogenic, Palynological, and Anthracological Evidences

Several series of well-developed paleosols of different ages have been examined on the Moskva River floodplain. In the beginning of the Holocene, forest-steppe biomes were widespread in this area, and dark-humus (Black) soils with stable humate humus and without features of textural differentiation predominated on the floodplain. The presence of meadow-steppe vegetation communities during this period is confirmed by the results of palynological and anthracological analyses. The lower paleosol in section RANIS 2 is represented by the deep humus horizon with 14C dates from 5500 to 8400 BP and the carbonate-accumulative horizon; it also contains large and deep tunnels of burrowing animals typical of chernozems. Wood charcoal is absent, and pollen of Artemisia and Chenopodium species predominates. Paleosols of the second half of the Holocene are represented by gray-humus and soddy-podzolic soils (Luvisols). In these soils and in the alluvial sediments, beginning from the Subboreal period, pollen of trees predominates; there are abundant charcoal of spruce and burnt spruce needles. In that time, forest-steppe and broadleaved forest biomes on the floodplain were replaced by southern taiga biomes. The second half of the Holocene is also specified by the human impacts on the local landscapes. Palynological and anthracological data attest to the large-scale burning of forests for pastures in the Bronze Age and, later, for cropland. The paleosol of the Iron Age is enriched in humus. It contains tunnels of burrowing animals related to the stage of anthropogenic meadows. It also contains pyrogenic calcite. The recent centuries have been characterized by extremely high floods triggered by the human activity; they have been accompanied by the fast accumulation of coarse-textured alluvial sediments and the formation of weakly developed alluvial soils.

Polylepiswoodland dynamics during the last 20,000 years

AbstractAimTo determine the palaeoecological influences of climate change and human land use on the spatial distribution patterns ofPolylepiswoodlands in the Andes.LocationTropical Andes above 2,900 m between 2°S and 18°S of latitude.MethodsPollen and charcoal data were gathered from 13 Andean lake sediment records and were rescaled by the maximum value in each site. The rescaled pollen data were used to estimate a mean abundance and coefficient of variation to show woodland expansions/contractions and woodland fragmentation over the last 20,000 years. The rescaled charcoal was displayed as a 200‐year moving median using 500‐year bins to infer the influence of fire on woodland dynamics at landscape scale. Pollen and charcoal were compared with speleothem, clastic flux and archaeological data to assess the influence of moisture balance, glacial activity and human impact on the spatial distribution ofPolylepiswoodlands.ResultsWoodland expansion and fire were correlated with precipitation changes and glacier dynamics fromc. 20 to 6 kcalbp(thousands of calibrated years before present). Charcoal abundances between 20 and 12 kcalbpwere less common than from 12 kcalbpto modern. However, human‐induced fires were unlikely to be the main cause of a woodland decline centred at 11 kcalbp, as woodlands recovered from 10.5 to 9.5 kcalbp(about twofold increase). Charcoal peaks analogous to those that induced the woodland decline at 11 kcalbpwere commonplace post‐9.5 kcalbpbut did not trigger an equivalent woodland contraction. An increase in the coefficient of variation afterc. 5.5 kcalbpsuggests enhanced fragmentation and coincided with the shift from logistic to exponential growth of human populations. Over the last 1,000 years,Polylepisbecame hyper‐fragmented with over half of sites losingPolylepisfrom the record and with coefficients of variation paralleling those of glacial times.Main conclusionsPolylepiswoodlands formed naturally patchy woodlands, rather than a continuous vegetation belt, prior to human occupation in the Andes. The main factors controlling pre‐human woodland dynamics were precipitation and landscape heterogeneity. Human activity led to hyper‐fragmentation during the lastc. 1,000 years.

Palaeoenvironments and palaeocommunities from Lower Cretaceous high-latitude sites, Otway Basin, southeastern Australia

Lower Cretaceous (Barremian to Albian) fossil plant assemblages are preserved in sediments of the Otway Group, Otway Basin, and contemporaneous Strzelecki Group, Gippsland Basin, southeastern Australia. Detailed lithofacies and biofacies analyses of terrestrial strata within the upper Eumeralla Formation (Albian), Otway Group, allow fine-scale interpretation of braided fluvial and paludal depositional environments throughout the succession. The previously described flora is re-assessed in light of changes in depositional style and plant communities to describe six Albian biofacies. Forests in the highlands are dominated by Araucariaceae conifers, which turn over to Podocarpaceae and Cheirolepidiaceae forests on the dry, raised areas in the lowlands. Ferns and angiosperms inhabit the moist floodplains and water ferns and lycophytes dwell in the ox-bow lakes.Significant changes occur between floral communities characteristic of riparian, levee and floodbasin settings through the Early Cretaceous. Albian floras are characterized by the dominance of broad-leafed araucarian conifers, an understory of diverse ferns and a dearth of seedferns and angiosperms. There is a notable absence of macrofossil ginkgoaleans in the Eumeralla Formation, although they reappear in younger (Turonian) deposits in southeastern Australia, but angiosperms are extremely scarce as macrofossils compared to the diversity recently recorded in the pollen record. Abundant charcoal demonstrates that fire continued to be a significant environmental factor at high latitudes during the middle to late Albian. The discovery of dinoflagellate species supports an earlier marine incursion and increased coastal environments, probably inhabited by cheirolepids, across the Otway Basin. Palaeontological, palynological and sedimentological data has provided a synthesis of the region's warm, high-latitude, palaeoclimatic setting in the Albian stage of the Early Cretaceous when compared to the cooler Barremian to Aptian.

Postpyrogenic Polycyclic Soils in the Forests of Yakutia and Transbaikal region

Periodical forest fires are typical natural events under the environmental and climatic conditions of central and southern Yakutia and Transbaikal region of Russia. Strong surface fires activate exogenous geomorphological processes. As a result, soils with polycyclic profiles are developed in the trans-accumulative landscape positions. These soils are specified by the presence of two–three buried humus horizons with abundant charcoal under the modern humus horizon. This indicates that these soils have been subjected to two–three cycles of zonal pedogenesis during their development. The buried pyrogenic humus horizons accumulate are enriched in humus; nitrogen; total and oxalate-extractable iron; exchangeable bases (Са+2 and Mg+2); and the fractions of coarse silt, physical clay (<0.01 mm), and clay (<0.001 mm) particles in comparison with the neighboring mineral horizons of the soil profile. The humus of buried pyrogenic horizons is characterized by the increased content of humic acids, particularly, those bound with mobile sesquioxides (HA-1) and calcium (HA-2) and by certain changes in the type of humus.

Pre-Quaternary wood decay ‘caught in the act’ by fire – examples of plant-microbe-interactions preserved in charcoal from clastic sediments

The fossil record contains abundant evidence for the activity of microorganisms in the form of characteristic decay structures within fossil plant remains. Despite an abundance of charcoal in many sedimentary environments, there is little published evidence of such decay structures within charcoal from pre-Quaternary clastic deposits. The present contribution presents some examples of pre-Quaternary charcoal from clastic sediments which exhibit pre-charring decay structures, stratigraphically reaching from the Permian up to the Oligocene. Examples include specimens affected by the principle types of wood rot known from modern ecosystems (i.e. brown-rot, white rot and soft-rot) as well as a peculiar decay pattern resembling an atypical type of white-rot, which is only rarely known from modern wood. Theoretically there are different, so far hypothetical, scenarios which could be used to explain the scarcity of published reports on such material. Besides taphonomical biases directly influencing the sedimentary record of charcoal towards material not affected by microbial decay, it is conceivable that the lack of reports of such material from pre-Quaternary clastic deposits represents a, maybe unintentional, bias introduced by scientists working on pre-Quaternary charcoal.

Does fuel type influence the amount of charcoal produced in wildfires? Implications for the fossil record

AbstractCharcoal occurrence is extensively used as a tool for understanding wildfires over geological timescales. Yet, the fossil charcoal literature to date rarely considers that fire alone is capable of creating a bias in the abundance and nature of charcoal it creates, before it even becomes incorporated into the fossil record. In this study we have used state‐of‐the‐art calorimetry to experimentally produce charcoal from 20 species that represent a range of surface fuels and growth habits, as a preliminary step towards assessing whether different fuel types (and plant organs) are equally likely to remain as charcoal post‐fire. We observe that charcoal production appears to be species specific, and is related to the intrinsic physical and chemical properties of a given fuel. Our observations therefore suggest that some taxa are likely to be overrepresented in fossil charcoal assemblages (i.e. needle‐shed conifers, tree ferns) and others poorly represented, or not preserved at all (i.e. broad shoot‐shed conifers, weedy angiosperms, shrub angiosperms, some ferns). Our study highlights the complexity of charcoal production in modern fuels and we consider what a bias in charcoal production may mean for our understanding of palaeowildfires.

THE SIGNIFICANCE OF PEATLAND AGGRADATION IN MODERN AND ANCIENT ENVIRONMENTS

Abstract: Peats are commonly used in paleoenvironmental and paleoclimatic studies but detailed sedimentological and facies models for peatlands are poorly developed relative to other sedimentary settings. A comparison of the palynology and charcoal abundances in modern and ancient Cenozoic peats (i.e., brown coals) demonstrates that, in a single cycle, their respective flora commonly evolves from inundated wetland assemblages to more elevated and well-drained forest. The repetitive nature of this pattern suggests that the changing floral compositions result from changes in substrate wetness during peatland aggradation in high rainfall settings. In this scenario, floristic changes within the peat are suggested to represent peatland facies that were controlled by the local peat-forming environment. We suggest that peatland aggradation is an important process that may ubiquitously control the floral and environmental changes documented in modern and Holocene ombrogenous peats, brown coal lithotype cycles, and perhaps black coal dulling-upwards cycles.

Late-Quaternary records of vegetation and fire in southeastern North Carolina from Jones Lake and Singletary Lake

We conducted fossil pollen, charcoal, and geochemical analyses of sediment cores from Jones Lake and Singletary Lake spanning the last ∼50,000 cal yr B.P. to examine the linkages between climate, vegetation, and fire activity on the Atlantic Coastal Plain, and particularly emphasize changes since the Last Glacial Maximum. Application of the modern analog technique (MAT) to fossil pollen data allowed for quantitative estimates of Holocene climate, but Pleistocene assemblages had no modern analogues preempting their use for quantitative reconstructions. The MAT data indicate markedly lower mean annual precipitation and temperatures during the late Pleistocene relative to the Holocene. Increased charcoal accumulation during interstadials indicates increased fire activity during these warm intervals. Geochemical data (δ13C, δ15N, C:N) and pollen concentrations indicate a sparsely-vegetated Pleistocene landscape that produced few fires followed by an increase in biomass and fire activity around the lakes during the Holocene transition. A Quercus spp. maximum in the early Holocene is associated with low charcoal abundances, while increased dominance of Pinus spp. during the middle Holocene is associated with dramatic increases in charcoal. It is unclear if the Quercus-Pinus transition was the result of changing fire regimes or if the fire regime changed in response to vegetation. The regional asynchronicity of the Quercus-Pinus transition may indicate another forcing mechanism besides climate change, such as prehistoric human activity, is responsible for the ecological change. Macroscopic charcoal and C:N ratios reach unprecedented values during the late Holocene, possibly as a result of deforestation by both prehistoric Native Americans and later immigrant populations.

Vegetation history since the last glacial maximum in the Ozark highlands (USA): A new record from Cupola Pond, Missouri

The timing and drivers of vegetation dynamics and formation of no-analog plant communities during the last deglaciation in the unglaciated southeastern US are poorly understood. We present a multi-proxy record spanning the past 19,800 years from Cupola Pond in the Ozarks Mountains, consisting of replicate high-resolution pollen records, 25 AMS radiocarbon dates, and macrofossil, charcoal, and coprophilous spore analyses. Full-glacial Pinus and Picea forests gave way to no-analog vegetation after 17,400 yr BP, followed by development of Quercus-dominated Holocene forests, with late Holocene rises in Pinus and Nyssa. Vegetation transitions, replicated in different cores, are closely linked to hemispheric climate events. Rising Quercus abundances coincide with increasing Northern Hemisphere temperatures and CO2 at 17,500 yr BP, declining Pinus and Picea at 14,500 yr BP are near the Bølling-Allerød onset, and rapid decline of Fraxinus and rise of Ostrya/Carpinus occur 12,700 yr BP during the Younger Dryas. The Cupola no-analog vegetation record is unusual for its early initiation (17,000 yr BP) and for its three vegetation zones, representing distinct rises of Fraxinus and Ostrya/Carpinus. Sporormiella was absent and sedimentary charcoal abundances were low throughout, suggesting that fire and megaherbivores were not locally important agents of disturbance and turnover. The Cupola record thus highlights the complexity of the late-glacial no-analog communities and suggests direct climatic regulation of their formation and disassembly.