Macroscopic Charcoal Research Articles

Surface microtextures of quartz grains and minor sedimentary components across the Paleolithic Jeongok‐ri sediments, Yeoncheon, South Korea

ABSTRACTThe Jeongok‐ri Paleolithic site in the central Korean peninsula is known as the first findspot of Acheulean‐type hand axes in East Asia. Although many previous studies have investigated the depositional environments of Jeongok‐ri sediments across the Paleolithic occupation, they remain controversial. In this study, we collected an 11‐m‐long core to obtain evidence from systematic surface microtextures of quartz grains (SMQs) concerning depositional environments in the Jeongok‐ri archeological site. SMQs in the Jeongok‐ri sediments are characterized by dominant angular to subangular outlines and small to large conchoidal fractures with arcuate steps, as well as sparse V‐shaped percussion cracks; these features suggest short distances and subaqueous transportation with grain‐to‐grain collisions and violent impacts of quartz grains. On the basis of simultaneous sedimentation of the hosting silt deposits, our SMQ results suggest that Jeongok‐ri sediments were originally fluvial, regardless of their intermediate sedimentary history. This evidence from quartz grain microtextures is consistent with minor sedimentary components found in the Jeongok‐ri core sediments, such as diatom grains as microfossil constituents, along with macroscopic charcoals and titanium‐bearing detrital magnetite grains. The geological and geomorphological conditions of the Jeongok‐ri site are also favorable for floodplain environments given the position adjacent to river terraces formed by the previous lateral erosion of a meandering channel in the nearby Hantan River. Our findings will help to understand environmental conditions during the development of Paleolithic cultures in East Asia.

“Antarctic on fire”: Paleo-wildfire events associated with volcanic deposits in the Antarctic Peninsula during the Late Cretaceous

The occurrence of paleo-wildfire events during the Campanian age of the Late Cretaceous is demonstrated in this study for the first time with deposits from the King George Island, South Shetland Islands, Antarctic Peninsula. With the aim of providing information that fills important paleoenvironmental and paleobiogeographic gaps about the end of the Cretaceous for the Gondwana, samples of macroscopic charcoal were collected at two different volcanic levels of the Price Point outcrop, King George Island, during the expeditions to the Antarctic Peninsula by the Brazilian Antarctic Program (PROANTAR). The samples of charcoal were treated and later analyzed under a stereomicroscope and scanning electron microscope. The analysis allowed the identification of morphoanatomical structures with potential taxonomic affinity with Podocarpaceae. These conifers were important in temperate forests of high-latitude environments during the Late Cretaceous, and this is in accordance with previous palaeobotanical records from Price Point. The analysis also showed that southern paleofloras were subject to the occurrence of paleo-wildfires much more frequently than previously thought. This indicates that fire and active volcanism were significant modifiers of the ecological niches of austral floras, because even in distal areas, the source of ignition for forest fires often came from contact with a hot volcanic ash cloud, where the vegetation was either totally or partially consumed by fire.

The transition from an Indigenous to a European influenced fire regime at Lake Werri Berri, south-east Australia

The drivers of fire regimes prior to the European occupation of Australia are still contentious, with some advocating regimes dominated by anthropogenic ignitions and others advocating a climate source or mixture of these elements. Here, we examine an 850-year history of fire regimes at Lake Werri Berri in south-east Australia, prior to and following European occupation. Macroscopic charcoal and FTIR spectroscopy were used to infer broad changes of the fire regime in proximity to the lake. We found little change through much of the 850-year period and most interesting, no apparent change following the initial displacement of Indigenous peoples and the introduction of farming and woodcutting to the region by Europeans. From the mid-20th Century onwards, there was an increase in both area burnt and fire severity or intensity, likely the result of increased fuel load and connectivity following an extended period of increased precipitation and heavier recreational land usage, which likely led to an increase in anthropogenic ignitions.

Investigating the Effect of Oxidants on the Quantification and Characterization of Charcoal in Two Southeast Australian Sedimentary Records

This study examined the effects of commonly used oxidants in sedimentary macroscopic charcoal analysis on two sediment cores from Thirlmere Lakes National Park, Southeast Australia. The cores, from Lake Werri Berri (WB3) and Lake Couridjah (LC2), span ~900 years and 135,000 years, respectively. The Charcoal Accumulation Rate (CHAR) for both charcoal area and count was quantified using four different chemical treatments and compared to a control using only water. We also quantified the Charring Intensity (CI) of isolated charcoal fragments, a proxy for the severity/intensity of fire, determined using the FTIR spectral characteristics of the remaining charcoal after each treatment. We found significant differences in both the area and number of particles across all treatments in both cores. Significantly, we found substantial differences in CI between treatments, with few charcoal particles formed in low-severity fire (e.g., below ~400 °C or 3.0 °C.s.106) in groups treated with an oxidant. In contrast, the control group displayed a wider range of CI values and contained lightly pyrolyzed particles. This suggests that methods using an oxidant to concentrate sedimentary charcoal are potentially biasing records towards high-intensity or -severity fires. We suggest that consideration should be used when choosing laboratory methods based on the hypotheses being tested.

Holocene fire regimes, fire‐related plant functional types, and climate in south‐coastal British Columbia forests

AbstractPaleoecological records of past fire events and forest composition provide long‐term ecological context for modern changes in fire regimes and forest dynamics. Here, we use pollen and contiguous macroscopic charcoal analyses of lake sediments from Pender Island, British Columbia, Canada to reconstruct changes in fire regimes over the last 10,000 years and investigate how these interact with changes in climate and forest composition with a focus on fire‐related plant functional types. The relatively warm and dry early Holocene was characterized by high charcoal accumulation rates, fire episodes of moderate severity, and a mean fire return interval of 100 ± 27 years. Forests at the time were open‐canopy Pseudotsuga menziesii forests with abundant fire endurer taxa (e.g., Pteridium aquilinum) that have a competitive advantage in regimes of frequent fire. Fire continued to occur every ~100 years, on average, during the establishment of Quercus garryana savanna communities; however, a decrease in charcoal peak magnitudes suggests the fire regime shifted to one characterized by smaller and/or lower intensity surface fires. As temperature and moisture deficits decreased in the mid‐ and late Holocene (i.e., after ~6000 calendar years before present), mean fire return intervals lengthened to 176 ± 54 years and increased variability in charcoal peak magnitudes suggests a mixed fire regime of low‐moderate‐intensity fires combined with infrequent crown or stand‐replacing fires. Relatively stable and moderate climate, longer fire return intervals, and mixed‐severity fires allowed P. menziesii (a fire resister) to dominate closed‐canopy forests and for fire avoiders to gradually become more common forest constituents. Millennial‐scale climate change has acted as the dominant driver of changes in both fire regimes and forest composition over the last 10,000 years; however, changes in fire‐related plant functional types highlight the important role that interactions between vegetation and fire play in long‐term fire regimes and forest dynamics.

Postglacial vegetation and fire history with a high-resolution analysis of tephra impacts, High Cascade Range, Oregon, USA

The postglacial history of vegetation, wildfire, and climate in the Cascade Range (Oregon) is only partly understood. This study uses high-resolution macroscopic charcoal and pollen analysis from a 13-m, 14,500 years sediment record from Gold Lake, located in a montane forest, to reconstruct forest vegetation and fire history. The occurrence of three tephra layers, including a 78-cm airfall Mazama tephra, as well as highly laminated segments, allows one to study tephra impacts on vegetation at a fine temporal resolution. From the Late Glacial through the Younger Dryas, pollen spectra vary little. The early Holocene is marked by a sudden increase in Pseudotsuga, indicating warmer conditions, while the late Holocene is marked by increasing Tsuga heterophylla and Tsuga mertensiana, indicating the onset of moist conditions in the region. High-resolution charcoal data show periods of large peaks during the Late Glacial, pre-, and post-Mazama eruption and since 4 ka (thousands of years before present). Low fire during the early Holocene is unexpected, given regional evidence of warmer and drier summers, but it may be the result of fuel limitation. After the Mazama tephra deposition (7.63 ka), the non-arboreal pollen composition was changed, with some taxa disappearing or reduced in abundance for 300 years. Arboreal taxa were little affected by the tephra, showing only a 20% increase in Pinus pollen and no discernible impact on the pollen accumulation rate (PAR).In contrast, the Mazama tephra was followed by ca. 70 years of very low charcoal input, followed by a large peak, consistent with the burial of surface fuels and decades of fuel accumulation. There was also increased fire frequency and peak magnitude at 1.5 ka, followed by very little fire after 0.4 ka, consistent with the current old-growth forest surrounding the lake. This detailed and high-resolution record adds significantly to understanding the impacts of climate change and the singular effect of the Mazama eruption, impacting watershed vegetation, and fire for centuries but with minimal impact on the regional forest composition.

Fires and rates of change in the temperate rainforests of northwestern Patagonia since ∼18 ka

We examine the temporal and spatial structure of wildfires and rates of vegetation change in the Pacific sector of northwestern Patagonia (40°-44°S) over the last ∼18,000 years. Macroscopic Charcoal Accumulation Rates (CHAR), a proxy of past local fires, shows a geographic variation that mirrors the modern north-to-south and low-to-high elevation increase in annual precipitation and decrease in precipitation seasonality, and the frequency of explosive volcanic events. Variability in past fires is evident at multiple timescales, with a significant multi-millennial low between ∼18–13.1 ka, an abrupt rise between ∼13.1–12.5 ka, and heightened fire activity between ∼11.4–8.2 ka with significant high values between ∼10–9.4 ka. A subsequent decline led to the lowest Holocene values between ∼6–5.4 ka, which rose and led to significant high values between ∼3.1 ka and the present. Andean and Western Upwind Environments share a multi-millennial structure of fire activity since ∼18 ka, overprinted by millennial and centennial-scale divergences. These differences underscore the role of explosive volcanism as a trigger or modulator of fire activity in the vicinity of Andean eruptive centers. We posit that fire activity in Western Upwind Environments was driven primarily by hydroclimate variations, namely changes in the intensity of the Southern Westerly Winds. Compilations of CHAR and the Rates of Change (ROC) parameter, a measure of the magnitude and rapidity of changes in the pollen records, covary during the onset of the interglacial fire regime at ∼13.1 ka and the last ∼4000 years, suggesting that fires catalyzed vegetation changes during specific intervals since the last glaciation. Highly mobile human occupations deployed along the coasts started at ∼6.2 ka, increased in pulses, and spread widely during the last two millennia. Covariation with CHAR and ROC since ∼4 ka suggests that hunter-gatherer-fishers contributed to enhanced fire activity and abrupt vegetation changes at regional scale. The ubiquitous fire maximum over the last four centuries relates to widespread settlement and associated large-scale land clearance conducted by European/Chilean settlers.

A 1300-year multi-proxy palaeoecological record from the northwest Putorana Plateau (Russian Subarctic): environmental changes, vegetation dynamics and fire history

This paper presents a reconstruction of natural environmental dynamics, wildfires and vegetation change in northwest Putorana Plateau during the last 1300 years. The study area is a remote and poorly investigated region of subarctic Siberia, relatively untouched by human impacts, which offers a unique opportunity to examine natural environmental dynamics and climate-vegetation-fire relationships. The paleoenvironmental reconstructions are based on multi-proxy analysis of the Gervi peatland including pollen, plant macrofossil, testate amoebae and charcoal analysis, loss on ignition measurements and AMS radiocarbon dating. The results revealed the main phases of regional paleoenvironmental change: a warm period between 680 and 1200 C.E. (Common Era) corresponding to the Mediaeval Climate Anomaly (MCA), followed by climate cooling during the Little Ice Age (LIA, 1200–1850 C.E.) and subsequent centuries. Climate amelioration during the MCA led to afforestation of northwestern Putorana Plateau and an expansion of spruce extending 70 km northeast of its present geographical range. A quantitative water-table reconstruction was generated using a testate amoebae transfer function and suggested that relatively dry climate conditions during the MCA triggered high fire frequencies. The LIA appeared in the study area as a period of pronounced climate cooling and moderate moistening, which caused an extension of tundra vegetation and a dramatic decline of fire activity. Distinct environmental changes at the study site were detected since 1990 C.E., characterized by a high peat accumulation rate and rising water table. Since 1990 C.E., the macroscopic charcoal accumulation rate in the peat core increased abruptly, suggesting a recent increase in the fire frequency in the study region.

The Holocene palaeoecology of the palsa mire near Igarka (Yenisei Siberia)

The paper presents a new paleoecological evidence covering the last 6500 years based on detailed AMS radiocarbon dating, plant macrofossils, loss on ignition and macroscopic charcoal records from a 8 m long peat sequence, obtained from the palsa mire situated near Igarka (Yenisei Siberia). The obtained data show that the peatland initiation, development of the perennial frost mound and local vegetation history were strongly influenced by the Holocene climatic fluctuations and permafrost dynamics. The main stages of palsa uplift occurred at about 5360 cal yr BP and 2250 cal yr BP and coincided with the periods of cooling in the Russian Arctic region. According to the radiocarbon dating and plant macrofossil analysis of the upper part of peat sequences the peat accumulation rate in the palsa decreased significantly during the last 2000 years. Nevertheless, we consider that the rate of the peat vertical growth could be underestimated due to the disturbance of the frost mound, water erosion and wildfires.

Holocene and recent fires influence on soil organic matter, microbiological and physico-chemical properties of peats in the European North-East of Russia

The influence of fires on the development and chemical composition of two Rheic Hemic Histosols in the native territory of the middle taiga of the Komi Republic was estimated. The development of peat on site I (SI) located in the south boarder of the middle taiga began in the Boreal period (about nine ths. years ago14C yr BP). The growth of peat on site II (SII) located at the foothills of the Northern Urals started in the middle of the Atlantic Holocene period (about 6.7 ths. years ago14C yr BP). This work shows that during the time of development, peatlands experienced various pyrogenic events. The organic horizons were burned out and often led to a change in the dominant ground cover plants. Also, the charcoal particles formed during the fire at the forest surrounding the bogs were transported by air and accumulated in the peat. The pyrogenic history of the studied peats is different, the SI was subjected to intense fires at least twice: at the beginning of formation and in the modern period (140 years ago). The Histosol on SII experienced only low-intensity and indirect fire effect. The highest burning activity of nearest forests in both sites estimated based on charcoal content occurred at the end of the Atlantic, middle of the Subboreal periods. It was shown that an increase in the aromatic compounds occurs in horizons with pyrogenic features; in some cases, an increase in the concentration of polycyclic aromatic hydrocarbons (PAHs) was revealed. The aromatic compounds content in the SOM is determined by the content of macroscopic charcoal particles with significant correlation (CAr-H(C), R = 0.49, p < 0.05, CAr-O,N, R = 0.68, p < 0.05). It is shown that a high frequency of fires leads to an increase in carbon stocks at Histosols.

Late Holocene environmental and hydro-climatic variability inferred from a shallow lake record, blowout dunes, Argentinian western Pampas, South America

The Pampas plains of southern South America were predominantly dry, eolian-shaped landscapes, besides some interposed humid phases, during most of the late Pleistocene-Middle Holocene, evolving to humid-subhumid grasslands hosting an increasingly large number of shallow lakes in the late Holocene. These lakes proved to preserve in their sediments worthy evidence to interpret past environmental-ecological conditions, offering tools to analyze climatic variability and human impacts during the last millennia. This is the case of the shallow lake Primera Laguna, located in the western and driest edge of the Pampas. Here, we present a multiproxy study from this shallow lake with the aims of contributing to reconstruct its past stages, infer the climatic scenarios that drove its evolution, evaluate the potential anthropogenic role in these changes, and correlate/analyze this record with available data from other Pampean lakes. We analyzed a high-resolution palynological record, accompanied by macroscopic charcoal accumulation rates, C/N, C and N stable isotopes, magnetic susceptibility, and sediment geochemistry, of a 41-cm long sediment core, extracted from the deepest sector of the lake. An age-depth model based on AMS chronology indicates a preserved lake history for the past ∼1400 cal yr BP. Ecological and sedimentological interpretations allowed us to propose four main periods during this time lapse. For the first period (1375–1069 cal yr BP, 575–881 CE), the integrative interpretation indicates a very low shallow lake –mostly oligotrophic, alkaline, and clear water–, dominated by the accumulation of epiclastic silty fine sand from the surrounded eolian landscape and covered by xerophytic vegetation. In the second period, between 1069 and 738 cal yr BP (881–1212 CE), we inferred a trend to rising lake levels and mesotrophic conditions, and more pollen taxa than the previous period, and with lake margins dominated by cattails and sedges. The third period (738–193 cal yr BP, 1212–1757 CE) was characterized by more variable and lower lake levels compared to previous periods and more frequent desiccation processes at the lake margins. Then, during the fourth period (last 195 cal yr, 1757–2015 CE), there was a gradual transition towards a larger and more stable shallow lake with a deeper water column, and under a turbid state probably related to eutrophication. From the comparison between Primera Laguna record and the previously studied Nassau shallow lake, located in the same eolian landscape, we found a synchronic evolution, implying common drivers of change in terms of climatic variability and human impact. Correlation with shallow lakes from the more humid belt of the Pampas suggests widespread increases of water availability in the region since ∼1500 cal yr BP, variable/lower lake levels during ∼600–200 cal yr BP, and a shift to positive hydrological balances up to the present highstands.

Late-Holocene vegetation and fire history in Western Putorana Plateau (subarctic Siberia, Russia)

We present a reconstruction of vegetation dynamics and fire history from the western part of the Putorana Plateau during the Late-Holocene. The study area is located in the remote and poorly investigated region of Central Siberia, which represents an important area for understanding climate and environmental changes in the Russian Subarctic. Pollen and macroscopic charcoal data from three closely located lakes along an altitudinal transect in the Khantaika River basin show no major changes in vegetation in the study area during the last 3.9 ka BP. However, a detailed analysis of the data reveals an extension of forest coverage in lake catchments at about 3.1 ka BP followed by a gradual degradation of woodlands, and an expansion of shrubs and tundra vegetation at around 2.7–2.5 ka BP. Fire activity was relatively high between 3.0 and 2.0 ka BP compared to all but the most modern part of the record, while macroscopic charcoal accumulation reaches a maximum in the most recent surface sediments. This suggests an increase in the frequency and area of fires in the region since the end of the 19th century, which has no analog during the Late-Holocene.

Evidence that modern fires may be unprecedented during the last 3400 years in permafrost zone of Central Siberia, Russia

Recent climate change in Siberia is increasing the probability of dangerous forest fires. The development of effective measures to mitigate and prevent fires is impossible without an understanding of long-term fire dynamics. This paper presents the first multi-site palaeo-fire reconstruction based on macroscopic charcoal data from peat and lake sediment cores located in different landscapes across the permafrost area of central Siberia. The obtained results show similar temporal patterns of charcoal accumulation rates in the cores under study, and near synchronous changes in fire regimes. The paleo-fire record revealed moderate biomass burning between 3.4 and 2.6 ka BP, followed by the period of lower burning occurring from 2.6 to 1.7 ka BP that coincided with regional climate cooling and moistening. Minimal fire activity was also observed during the Little Ice Age (0.7–0.25 ka BP). Fire frequencies increased during the interval from 1.7 to 0.7 ka BP and appears to be partly synchronous with climate warming during the Medieval Climate Anomaly. Regional reconstructions of long-term fire history show that recent fires are unprecedented during the late Holocene, with modern high biomass burning lying outside millennial and centennial variability of the last 3400 years.

Legacies of past human activities on one of the largest old-growth forests in the south-east European mountains

The Dinaric Mountains are a region considered as a hotspot for late-successional montane mixed Abies alba-Fagus sylvatica-Picea abies old-growth forests. This is likely due to historical deforestation levels being presumably lower than in other European regions. This paper provides new insights into the long-term vegetation dynamics and possible legacies of past human activities in old-growth forests in the montane zone of the Dinaric Mountains. Our extensive ground survey and the detailed land-cover types map show that the mixed A. alba-F. sylvatica old-growth forest with sparse P. abies is surrounded by almost pure F. sylvatica stands at Biogradska Gora. The well-dated stand-scale palaeoecological records (pollen, spores, stomata, macrofossils, macroscopic charcoal, and magnetic susceptibility) show that land use (cereal crop cultivation, cattle herding, and fire) during the Middle Ages caused a reduction of the A. alba and P. abies-dominated forest. After a major land abandonment around the Black Death pandemic (mid-14th century) and weaker land-use phases, F. sylvatica-dominated stands developed in the more accessible areas surrounding the old-growth forest. The legacy of past land uses is still visible as the almost pure F. sylvatica stands show less old-growth characteristics than other European beech-dominated old-growth forests. Markedly in contrast to decreasing tree cover elsewhere in the region, tree cover increased several centuries before the formal protection of the forest (1878 ce). These results support the view that historical land-use pressures played an important role for the small extent and the continuity of disturbance-sensitive A. alba and P. abies-dominated old-growth forest stands.

Sub-fossil bark beetles as indicators of past disturbance events in temperate Picea abies mountain forests

Temperate mountain forests have experienced an increase in frequency and severity of natural disturbances (e.g., droughts, fires, windstorms and insect outbreaks) in recent decades due to climate and environmental change. Outbreaks of bark beetles have caused significant dieback of conifer forests in Central Europe and it is essential to model and predict the potential severity of future bark beetle outbreaks. However, to predict future bark beetle activity, historical baseline information is required to contextualize the magnitude of current and potential future outbreaks. A fossil beetle record from a forest hollow in the Tatra Mountains, Slovakia; one of the best-preserved national parks in Central Europe, was produced to identify insect outbreaks during the last millennia. Sub-fossil bark beetle remains were compared with parallel pollen and charcoal to assess whether peaks in conifer bark beetle remains correspond with indications of disturbance documented in historical or sedimentary fossil records. Three peaks in bark beetle remains were detected (1) post-2004, (2) AD 1140–1440, and (3) AD 930–1030. The abundance of species Pityogenes chalcographus and Pityophthorus pityographus in the two top samples can be linked directly to large bark beetle outbreaks in the High Tatra Mountains after 2004. P. chalcographus and P. pityographus are also the abundant species in the second peak (AD 1140–1440) while the third peak (AD 930–1030) consists of the species Polygraphus poligraphus. The most prominent conifer bark beetle in Central Europe, Ips typographus, was found to be present in most of the samples but always at very low numbers. It is plausible that P. chalcographus and P. pityographus fossils might be useful proxies for past conifer bark beetle outbreaks in Central Europe, as they occur together with fossils of I. typographus but appear to be well-preserved. A significant correlation was found between primary bark beetles and macroscopic charcoal densities in the sediment, highlighting the complex interactions between disturbance agents, bark beetles and fire, in this long-term regime of natural disturbances. Our 1400-year disturbance record shows how bark beetle outbreaks have been an important component of the regional natural disturbance regime for over a millennium and have intensified with increasing anthropogenic activity. Bark beetle outbreaks are likely one of the drivers promoting the future ecological stability of the temperate conifer ecosystem over decades to centuries.

The last glacial termination in northwestern Patagonia viewed from the Lago Fonk (∼40°S) record

The anatomy of the Last Glacial Termination (T1) in the southern mid-latitudes, and its relationship with changes in the Southern Westerly Winds (SWW), offers empirical constraints for understanding the mechanisms involved in the transition from the Last Glacial Maximum into the current interglacial. Northwestern Patagonia (40°-44°S) is a sensitive region for monitoring past changes in the SWW, the Patagonian Ice Sheet, terrestrial ecosystems, and fire regimes through T1. Here we present results from Lago Fonk (∼40°S) to examine the structure of T1 based on the palynological, macroscopic charcoal, elemental, and isotopic composition of organic lake sediments.We observe an instantaneous establishment of Nothofagus-dominated forests at the onset of T1, followed by a diversification and densification trend that culminated with the establishment of thermophilous, Myrtaceae-dominated North Patagonian rainforests between ∼15.6–14.7 cal ka BP. The expansion of the conifer Podocarpus nubigena marks a shift to cool-temperate and hyperhumid conditions, coeval with high lake levels and enhanced algal productivity between ∼14.7–11.9 cal ka BP. Stand-replacing fires, driven by enhanced seasonality or high-frequency rainfall variability, started at ∼12.4 cal ka BP and catalyzed the rapid spread of Weinmannia trichosperma. Subsequent warming and a decline in precipitation at ∼11.4 cal ka BP led to intense fire activity, lake-level lowering, and establishment of the Valdivian rainforest trees Eucryphia/Caldcluvia. Our results suggest a coherent linkage between changes documented in the amphi south Pacific region and Antarctic ice cores during T1. This implies a zonal and hemispheric response to changes in the position/intensity of the SWW that emphasizes their central role as a key driver of the hemispheric and global climate evolution through T1.

Automatic identification of charcoal origin based on deep learning

The differentiation between the charcoal produced from (Eucalyptus) plantations and native forests is essential to control, commercialization, and supervision of its production in Brazil. The main contribution of this study is to identify the charcoal origin using macroscopic images and Deep Learning Algorithm. We applied a Convolutional Neural Network (CNN) using VGG-16 architecture, with preprocessing based on contrast enhancement and data augmentation with rotation over the training set images. on the performance of the CNN with fine-tuning using 360 macroscopic charcoal images from the plantation and native forests. The results pointed out that our method provides new perspectives to identify the charcoal origin, achieving results upper 95 % of mean accuracy to classify charcoal from native forests for all compared preprocessing strategies

Wildfires in the Early Triassic of northeastern Pangaea: Evidence from fossil charcoal in the Bogda Mountains, northwestern China

Fires are an integral part of modern and ancient ecosystems, serving as friends for renewal or foes for complete destruction and extinction. Indicators of palaeowildfire were so far absent from the Lower Triassic. Lack of plants in the Early Triassic due to the end-Permian mass extinction event and low atmospheric oxygen levels were proposed as the major reasons for the scarcity of wildfires. We present macroscopic charcoals from the Olenekian (Lower Triassic) in northwestern China, indicating probable ground/smoldering fires occurred on landscapes in mid-latitudes of northeastern Pangaea. Atmospheric oxygen concentration during the Olenekian would have been above 18.5%. These findings demonstrate that wildfires continued to be a source of disturbance of terrestrial ecosystems in Bogda Mountains after the end-Permian marine biotic crisis. There were adequate supplies of fuels and oxygen during this critical time period in the Earth history.

A lake sediment–based paleoecological reconstruction of late Holocene fire history and vegetation change in Great Basin National Park, Nevada, USA

AbstractAnalyses of macroscopic charcoal, sediment geochemistry (%C, %N, C/N, δ13C, δ15N), and fossil pollen were conducted on a sediment core recovered from Stella Lake, Nevada, establishing a 2000 year record of fire history and vegetation change for the Great Basin. Charcoal accumulation rates (CHAR) indicate that fire activity, which was minimal from the beginning of the first millennium to AD 750, increased slightly at the onset of the Medieval Climate Anomaly (MCA). Observed changes in catchment vegetation were driven by hydroclimate variability during the early MCA. Two notable increases in CHAR, which occurred during the Little Ice Age (LIA), were identified as major fire events within the catchment. Increased C/N, enriched δ15N, and depleted δ13C values correspond with these events, providing additional evidence for the occurrence of catchment-scale fire events during the late fifteenth and late sixteenth centuries. Shifts in the vegetation community composition and structure accompanied these fires, withPinusandPiceadecreasing in relative abundance and Poaceae increasing in relative abundance following the fire events. During the LIA, the vegetation change and lacustrine geochemical response was most directly influenced by the occurrence of catchment-scale fires, not regional hydroclimate.

Palaeobotanical and biomarker evidence for Early Permian (Artinskian) wildfire in the Rajmahal Basin, India

This study provides a combined analysis on the palynology, fossil charcoal and biomarkers of the subsurface coal deposits from a borehole RMB #2 drilled at the Dhulia Coal Block, Rajmahal Basin, India, in attempts to establish the chronology of sedimentation and to propose palaeobotanical as well as geochemical evidence for the occurrence of wildfires in these sediments. The palynological investigation suggests a Scheuringipollenites barakarensis palynoassemblage from the lower Barakar Formation, dated as Artinskian (Early Permian) in age. This assemblage reveals the dominance of Glossopteridales and sub-dominance of taxa belonging to Cordaitales and Coniferales. Fossil charcoal in sediments is usually recognized as a direct indicator for the occurrence of palaeo-wildfires. More data involving the anatomical features of fossil charcoal analyzed by Field Emission Scanning Electronic Microscope broaden our knowledge on Early Permian wildfires from the peninsula of India. The studied macroscopic charcoal fragments exhibit anatomical details such as homogenized cell walls, uniseriate simple and biseriate alternate pitting on tracheid walls and rays of varying heights pointing to a gymnospermous wood affinitity. The excellent preservation of charcoal fragments, shown by their large sizes and almost unabraded edges, suggests a parautochthonous origin. The embedded biomarker study performed for charcoal sediments and its characterization demonstrate the presence of n-alkanes, isoprenoids, terpenoids and aromatic compounds. A bimodal distribution pattern of n-alkanes with a Cmax at n-C25 is identified. Diterpenoids and pentacyclic terpenoids are identified, indicating the input of an early conifer vegetation and bacterial activity, respectively. The identified polyaromatic hydrocarbon (PAH) compounds, together with the charcoal fragments, clearly suggest that repeated wildfire events occurred during the deposition of these Artinskian sediments in the Rajmahal Basin.