Microscopic Charcoal Particles Research Articles

From Ponds to Pine Plantations in 9000 Years: The Environmental Archaeology of Beck Burn, Solway Moss, Cumbria

ABSTRACT This article explores the evidence for environmental change at Beck Burn, Solway Moss, on the English/Scottish border. The analysed pollen, non-pollen palynomorphs (NPP) and microscopic charcoal particles permit several palaeoenvironmental events to be interpreted, supported by radiocarbon dating. These and previously published data suggest the presence of very early Mesolithic water-edge activity, later Mesolithic woodland management, clearance and small-scale cultivation during the early Neolithic period, followed by low-level disturbance for pastoral farming in the early Bronze Age. Woodland clearance and cereal cultivation are dated to the middle Bronze Age, with significant clearance and cultivation identified during the late Iron Age or early Roman period. The medieval period is characterised by evidence for a mixed subsistence economy, with reduced activity possibly coincident with the Wars of Scottish Independence, famines and the Black Death of the fourteenth century, as well as the Little Ice Age. Renewed activity, with evidence for both arable and pastoral farming, is dated to the late medieval to early post-medieval period. Pine plantations were then created, possibly in the eighteenth century or later. The data reveal the importance of palaeoenvironmental archaeology, in the absence of significant finds or features, in creating a link with the past.

Volcanic impact on terrestrial and aquatic ecosystems in the Eastern Mediterranean

Natural disturbances such as volcanic eruptions provide a unique opportunity to study past ecological dynamics. Here we illustrate the response of terrestrial and aquatic ecosystems to volcanic eruptions in connection to prevailing climate conditions. We selected five volcaniclastic depositions in the Lake Van (Turkey) sediments from different interglacial/glacial periods (Marine Isotope Stages 3 to 9e). Using high-resolution pollen data, non-pollen palynomorphs, and microscopic charcoal particles we attempted to disentangle climatic and volcanic forcing of natural environmental disturbances. Our results highlights that the thickness of subsequent volcanic deposits and the respective climatic conditions strongly influence the impact on terrestrial and aquatic ecosystems. The most common response to ash deposition is a shift towards herbaceous taxa and abrupt fire activity. The affected herbaceous vegetation recovers to pre-eruption levels in 20 to 40 varve-years. The lake water experiences intensified productivity due to subsequent nutrient input and significant increase in aquatic microfossils. Our findings pave the way for disentangling climatic and volcanic forcing of natural environmental disturbances.

A late-Holocene multiproxy fire record from a tropical savanna, eastern Arnhem Land, Northern Territory, Australia

Fire has a long history in Australia and is a key driver of vegetation dynamics in the tropical savanna ecosystems that cover one quarter of the country. Fire reconstructions are required to understand ecosystem dynamics over the long term but these data are lacking for the extensive savannas of northern Australia. This paper presents a multiproxy palaeofire record for Marura sinkhole in eastern Arnhem Land, Northern Territory, Australia. The record is constructed by combining optical methods (counts and morphology of macroscopic and microscopic charcoal particles) and chemical methods (quantification of abundance and stable isotope composition of pyrogenic carbon by hydrogen pyrolysis). This novel combination of measurements enables the generation of a record of relative fire intensity to investigate the interplay between natural and anthropogenic influences. The Marura palaeofire record comprises three main phases: 4600–2800 cal BP, 2800–900 cal BP and 900 cal BP to present. Highest fire incidence occurs at ~4600–4000 cal BP, coinciding with regional records of high effective precipitation, and all fire proxies decline from that time to the present. 2800–900 cal BP is characterised by variable fire intensities and aligns with archaeological evidence of occupation at nearby Blue Mud Bay. All fire proxies decline significantly after 900 cal BP. The combination of charcoal and pyrogenic carbon measures is a promising proxy for relative fire intensity in sedimentary records and a useful tool for investigating potential anthropogenic fire regimes.

A new hypothesis for the origin of Amazonian Dark Earths

Amazonian Dark Earths (ADEs) are unusually fertile soils characterised by elevated concentrations of microscopic charcoal particles, which confer their distinctive colouration. Frequent occurrences of pre-Columbian artefacts at ADE sites led to their ubiquitous classification as Anthrosols (soils of anthropic origin). However, it remains unclear how indigenous peoples created areas of high fertility in one of the most nutrient-impoverished environments on Earth. Here, we report new data from a well-studied ADE site in the Brazilian Amazon, which compel us to reconsider its anthropic origin. The amounts of phosphorus and calcium—two of the least abundant macronutrients in the region—are orders of magnitude higher in ADE profiles than in the surrounding soil. The elevated levels of phosphorus and calcium, which are often interpreted as evidence of human activity at other sites, correlate spatially with trace elements that indicate exogenous mineral sources rather than in situ deposition. Stable isotope ratios of neodymium, strontium, and radiocarbon activity of microcharcoal particles also indicate exogenous inputs from alluvial deposition of carbon and mineral elements to ADE profiles, beginning several thousands of years before the earliest evidence of soil management for plant cultivation in the region. Our data suggest that indigenous peoples harnessed natural processes of landscape formation, which led to the unique properties of ADEs, but were not responsible for their genesis. If corroborated elsewhere, this hypothesis would transform our understanding of human influence in Amazonia, opening new frontiers for the sustainable use of tropical landscapes going forward.

What was burning in the past? Charcoal identifications supplement an early-Holocene fire-history reconstruction in Yellowstone National Park, USA

Analysis of charcoal particles preserved in lake sediments has been frequently used to reconstruct fire, vegetation and climate history. Larger macroscopic particles (>125 μm) are attributed to local fires, whereas microscopic charcoal particles (<125 μm), observed on pollen slides, are a signal of regional fire. Taxonomic identification of the charcoal particles adds to the fire-history reconstruction by providing information about fuel composition and past fire conditions. Identification of charcoal can unravel one of the longstanding questions regarding past fire regimes, namely what was burning. This paper describes an analysis of charcoal particles preserved in the sediments of a small closed-basin lake in Yellowstone National Park. Blacktail Pond (44.954°N, 110.604°W; 2012 m elev) is located in steppe vegetation surrounded by conifer forest. Previous studies of the site have presented a multi-proxy environmental history of the last 14,650 years. The focus of this investigation was on the fire history of the early-Holocene (11,500–9900 cal yr BP). Thirty-nine sediment samples were taken at 0.5 cm intervals to examine macroscopic charcoal particles, with attention on two large charcoal peaks at 10,970 and 10,200 cal yr BP that registered large or near-site fires. Twenty-eight samples contained 243 large-enough particles (180–250 μm) to be examined with scanning electron microscopy. We were able to identify charcoal of conifers (Pinus, Picea, and Abies or Juniperus), Artemisia and unidentified deciduous shrubs, and unidentified monocotyledons. The first fire burned a mixture of fuels, whereas the second episode burned Artemisia, shrubs and herbs but no conifers. The results are consistent with previous pollen interpretations at Blacktail Pond that indicate an open mixed-conifer forest in the early Holocene prior to 10,750 cal yr BP, replaced by Pinus contorta forest on the slopes and steppe in the valley. The relative dominance of Pinus contorta-type charcoal points to the importance of fire as a catalyst for the spread of this species.

A usage-based size classification scheme for sedimentary charcoal

Terms referring to charcoal particle size classifications are inconsistent in the paleofire literature. Inconsistencies of terminology prevent effective scientific discourse and research comparability. In this paper, I use the Global Charcoal Database (GCD) to determine the relative usage of sieving size boundaries and use these metadata as a proxy for the consensus of the paleofire community. With consideration of the size classification bounds used in other fields, I propose a standardized size classification system and terminology for charcoal particles. This system consists of macroscopic (&gt;125 μm), mesoscopic (50–125 μm), and microscopic (10–50 μm) charcoal particles and aims to unify paleofire jargon by conforming to the terminology and most commonly used size bounds in the community.

Implementing microscopic charcoal particles into a global aerosol–climate model

Abstract. Microscopic charcoal particles are fire-specific tracers, which are ubiquitous in natural archives such as lake sediments or ice cores. Thus, charcoal records from lake sediments have become the primary source for reconstructing past fire activity. Microscopic charcoal particles are generated during forest and grassland fires and can be transported over large distances before being deposited into natural archives. In this paper, we implement microscopic charcoal particles into a global aerosol–climate model to better understand the transport of charcoal on a large scale. Atmospheric transport and interactions with other aerosol particles, clouds, and radiation are explicitly simulated. To estimate the emissions of the microscopic charcoal particles, we use recent European charcoal observations from lake sediments as a calibration data set. We found that scaling black carbon fire emissions from the Global Fire Assimilation System (a satellite-based emission inventory) by approximately 2 orders of magnitude matches the calibration data set best. The charcoal validation data set, for which we collected charcoal observations from all over the globe, generally supports this scaling factor. In the validation data set, we included charcoal particles from lake sediments, peats, and ice cores. While only the Spearman rank correlation coefficient is significant for the calibration data set (0.67), both the Pearson and the Spearman rank correlation coefficients are positive and significantly different from zero for the validation data set (0.59 and 0.48, respectively). Overall, the model captures a significant portion of the spatial variability, but it fails to reproduce the extreme spatial variability observed in the charcoal data. This can mainly be explained by the coarse spatial resolution of the model and uncertainties concerning fire emissions. Furthermore, charcoal fluxes derived from ice core sites are much lower than the simulated fluxes, which can be explained by the location properties (high altitude and steep topography, which are not well represented in the model) of most of the investigated ice cores. Global modelling of charcoal can improve our understanding of the representativeness of this fire proxy. Furthermore, it might allow past fire emissions provided by fire models to be quantitatively validated. This might deepen our understanding of the processes driving global fire activity.

Evidence of Neogene wildfires in central Chile: Charcoal records from the Navidad Formation

Mediterranean-type climate (MTC) ecosystems are characterized by recurrent wildfires. Although the majority of wildfires are human-ignited, non-anthropogenic (i.e., natural) wildfires are common in all MTC regions except central Chile. The low frequency of natural wildfires in this Chilean region is explained by the scarcity of non-anthropogenic ignition sources, basically thunderstorm-induced lightning and volcanic activity. However, from a geological perspective, the current relative absence of non-anthropogenic wildfires in central Chile is a recent phenomenon. In the transition from the Early to Middle Miocene, the climate in the region was likely warm and seasonally dry. Such climate conditions would allow the growth of fuel during the spring, becoming flammable during the dry season. This fire-prone landscape would likely have been ignited by the high volcanic activity that concomitantly occurred with the orogeny of the Andes. To evaluate this hypothesis, we sampled rocks from the three locations at the Navidad Formation, considering the fossil plant evidence deposited during this warm and seasonally dry period. We found a high concentration of charcoal in Playa Navidad, coinciding with the global warming event reported between 17 and 15Ma. The predominance of microscopic charcoal particles (between 125 and 250μm) only allows us to infer the occurrence of Neogene fires at a regional scale. The fused cell walls preserved in the charcoal anatomy likely suggest that such fire events were highly severe. The presence of pumice associated with the high charcoal concentrations supports the hypothesis of volcanic ignition sources. Very little charcoal was found in Punta Perro (Late Oligocene – Early Miocene) or in Cerro Los Pololos (late Middle Miocene), where fire may have been limited by fuel humidity and ignition sources respectively, although changes in the depositional environment would also help explain differences in the fire record throughout the Navidad Formation. In conclusion, our results provide the first quantitative Neogene charcoal record for South America. The evidence of fire occurrence in central Chile during the Neogene will contribute to understanding the evolution of the Mediterranean-type flora.

Long‐term drivers of forest composition in a boreonemoral region: the relative importance of climate and human impact

AbstractAimTo assess statistically the relative importance of climate and human impact on forest composition in the late Holocene.LocationEstonia, boreonemoral Europe.MethodsData on forest composition (10 most abundant tree and shrub taxa) for the late Holocene (5100–50 calibrated years before 1950) were derived from 18 pollen records and then transformed into land‐cover estimates using the REVEALS vegetation reconstruction model. Human impact was quantified with palaeoecological estimates of openness, frequencies of hemerophilous pollen types (taxa growing in habitats influenced by human activities) and microscopic charcoal particles. Climate data generated with the ECBilt‐CLIO‐VECODE climate model provided summer and winter temperature data. The modelled data were supported by sedimentary stable oxygen isotope (δ18O) records. Redundancy analysis (RDA), variation partitioning and linear mixed effects (LME) models were applied for statistical analyses.ResultsBoth climate and human impact were statistically significant predictors of forest compositional change during the late Holocene. While climate exerted a dominant influence on forest composition in the beginning of the study period, human impact was the strongest driver of forest composition change in the middle of the study period, c. 4000–2000 years ago, when permanent agriculture became established and expanded. The late Holocene cooling negatively affected populations of nemoral deciduous taxa (Tilia, Corylus, Ulmus, Quercus, Alnus and Fraxinus), allowing boreal taxa (Betula, Salix, Picea and Pinus) to succeed. Whereas human impact has favoured populations of early‐successional taxa that colonize abandoned agricultural fields (Betula, Salix, Alnus) or that can grow on less fertile soils (Pinus), it has limited taxa such as Picea that tend to grow on more mesic and fertile soils.Main conclusionsCombining palaeoecological and palaeoclimatological data from multiple sources facilitates quantitative characterization of factors driving forest composition dynamics on millennial time‐scales. Our results suggest that in addition to the climatic influence on forest composition, the relative abundance of individual forest taxa has been significantly influenced by human impact over the last four millennia.

Langzeit-Feuerökologie der Schweiz | Long-term fire ecology of Switzerland

Understanding past natural and anthropogenically induced forest fires and their long-term impact on the environment is a prerequisite for modern fire management. Thanks to modern paleoecological approaches it was possible to reconstruct the long-term role of fire for ecosystems, landscape properties and functions in various parts of Switzerland. In order to test and calibrate the paleoecological approach on a local scale, we compared the forest-fire statistics of the last 70 years around the small Lago di Origlio (southern Switzerland) with the yearly charcoal influx in the lake sediments. We demonstrated that the yearly deposition of microscopic charcoal particles (0.01−0.2 mm) correlates well with the regional forest-fire frequency 20 to 50 km around the lake, whereas macroscopic charcoal particles (&amp;gt; 0.2 mm) matched local fire events within a 2 km distance. Furthermore, the pilot study of lake Origlio provided insights into the different origins of forest fires and their long-term impact on vegetation. Studies in other areas in Switzerland suggest that that the long-term effects of forest fire are not limited to the southern slope of the Alps, but also concern the forests of the Swiss Plateau and the Alps. There, the diffusion of fire-sensitive tree species such as Ulmus spp., Tilia spp., Fraxinus spp., Acer spp. at the colline to mountain level, as well as Abies alba and Pinus cembra at the subalpine level was significantly reduced compared to the natural environmental conditions prior to the beginning of widespread slash and burn practices. The abundance reduction of tree species during the past millennia occurred in the southern and the northern Alps, on the Swiss Plateau, but not in the fire-prone dry valleys of the central Alps, where forest fires were more frequent naturally and exerted relevant ecosystem functions. Our results show that without considering sedimentary paleoenviromental information it is hardly possible to gain correct assessments of current and future fire, environmental and forest dynamics. The implementation of paleoecological results into practical management activities is thus indispensable, especially in the view of the expected climatic changes.

Anthropogenic impact on vegetation and environment during the Bronze Age in the area of Lake Durankulak, NE Bulgaria: Pollen, microscopic charcoal, non-pollen palynomorphs and plant macrofossils

A new pollen core, called “Durankulak-3”, comes from the lake of that name, situated at the Black Sea coast of northeastern Bulgaria. The location of the core close to archaeological sites permits the correlation of palynological data, including non-pollen palynomorphs (NPP) (spores of fungi, remains of algae etc., as defined by van Geel, B., 2001. Non-pollen palynomorphs. In: Smol, J.P., Birks, H.J.B., Last, W. M. (Eds.), Tracking environmental changes using lake sediments. Vol. 3: Terrestrial, algal and siliceous indicators. Kluwer Academic Press, Dordrecht, pp. 99–119.), microscopic charcoal, and plant macrofossils with the archaeological data. A detailed reconstruction of the past vegetation reveals the extent of anthropogenic influence in the area. Radiocarbon dates from the basal part of the core show that the palaeoecological record begins at about 4500 BP. This start corresponds to the end of Chalcolithic and transition to the Bronze Age in the area and is connected with a rise of the lake level around Great Island and the lake shore to the west. Peaks of microscopic charcoal in the lowest part of the core coincide well with those of anthropogenic indicators in the pollen diagram and with the NPP, indicating fire and erosion. These signals can be attributed to the Early Bronze Age activities of nomadic tribes in the area, according to the archaeological record. A second peak of the anthropogenic indicators, well correlated with a peak in the NPP-dung indicators, is probably connected with the Late Bonze Age and Early Iron Age occupation of the area. This suggestion is supported by peaks of Vitis-pollen and the first appearance of Juglans-pollen. In the last zone the vegetation is more and more similar to that of the modern reduced forests and expanded steppe vegetation. In this part of the diagram more specialized crop weeds like Agrostemma githago and Centaurea cyanus appear, most probably originating from rye cultivated there during the Middle Ages. In parallel is the last peak of microscopic charcoal particles and NPP indicators for dung and erosion.

Pollen evidence for late-Holocene climatic variability at Laguna de Aculeo, Central Chile (lat. 34°S)

A pollen record is presented from Laguna de Aculeo (33°50'S, 70°55'W, 360m a.s.l.) that documents important vegetation changes over the last 2500cal. yr in Central Chile. Grasses, composites, trees, paludal and aquatic taxa dominated the Aculeo watershed between 2500 and 100cal. yr BP under a humid climate. Large amplitude fluctuations of pollen and microalgal accumulation rates and numerous turbidite layers during this interval, however, suggest high precipitation variability probably linked to El Niño-Southern Oscillation (ENSO) events. Although the expansion of warm sclerophyllous forest taxa over the last 100 years could be interpreted as an onset of a drier and warmer climate, this trend was more likely linked to human activities in the watershed. High accumulation rates of microscopic charcoal particles, exotic pollen taxa, and a shift from oligo-mesotrophic to hypereutrophic indicators would seem to back the latter hypothesis.

A 3.5 ka record of paleoenvironments and human occupation at Angkor Borei, Mekong Delta, southern Cambodia

AbstractMicrofossil and sedimentological data from a 3.1 m core extracted from a reservoir (baray) at the ancient Cambodian settlement of Angkor Borei in the Mekong Delta have provided a continuous record of sedimentation and paleoenvironments dating from about 2000 cal yr B.C. Palynological data indicate that for much of the cal. 1st and 2nd millennia B.C. mangroves dominated the regional vegetation, while extensively and regularly burnt grasslands dominated the local vegetation. Turbid, nutrient‐rich standing water characterized the core locality, perhaps suggesting a connection with rivers in the area. An abrupt change during the cal. 5th to 6th centuries A.D. involved a dramatic reduction in grasslands and the expansion of secondary forest or re‐growth taxa. These changes are synchronous with an abrupt decline in the concentration of microscopic charcoal particles in the sediments, and the colonization of the core locality by swamp forest plants. These changes are taken to indicate a shift in land‐use strategies or, possibly, a period of land abandonment. The age for the construction of the baray is interpreted to be in the 17th–19th centuries, but this dating remains speculative. Construction of the Angkor Borei baray exploited a preexisting body of standing water, so its construction was fundamentally different from the methods used at the Angkorian capital in northern Cambodia. © 2003 Wiley Periodicals, Inc.

Methodological and practical aspects of the presentation and interpretation of microscopic charcoal data from lake sediments

Analysis of microscopic charcoal particles is a useful part of palaeoecological research and is mostly used in conjunction with pollen analysis. However, there is considerable variation in the methodology of charcoal analyses. This paper considers various methods for the analysis of microscopic charcoal and the presentation of charcoal data in the context of a study of the upper sediments of two lakes Estonia. The results are evaluated by comparing both the pollen and charcoal data with documentary evidence of forest fires over the past 60 years. Indications of fires both varying in extent and at different distances from the lakes are evaluated in both the pollen and charcoal diagrams. The results suggest that the total area curve for charcoal particles per unit mass of sediment dry matter (cm2 g−1) provides the best indicator of forest fires. Fires in the study area are reflected differently in the charcoal and pollen curves. It is suggested that the charcoal data have the potential to indicate disturbance at a greater distance from the coring site than indicated by the pollen data.

Climate, Fire, and Vegetation between About 13,000 and 9200 14C yr B.P. in the Chilean Lake District

A pollen record from Lago Condorito (41°45′S, 73°07′W) shows that North Patagonian Rain Forest taxa predominated between about 13,000 and 12,200 14C yr B.P. in the lowlands of southern Chile, near the city of Puerto Montt. This was followed by the expansion and persistence of the conifer Podocarpus nubigena between 12,200 and 9900 14C yr B.P. Trees favored by disturbance expanded between 11,200 and 9900 14C yr B.P., concurrent with sharp and sustained increases of microscopic charcoal particles. Taxa of low-elevation rain forests expanded and became more diverse in pulses centered at 9900 and 9000 14C yr B.P., following the disappearance of P. nubigena. These data suggest conditions approaching modern climate between about 13,000 and 12,200 14C yr B.P. The climate cooled between 12,200 and 9900 14C yr B.P., then quickly warmed to interglacial conditions. Stand-replacing fires occurred near Lago Condorito between 11,200 and 9900 14C yr B.P., under cool-temperate, humid conditions. The proximity and reported antiquity of the Monte Verde archeological site raise the possibility that these fires were set by human activities.

Comparison of two methods of counting microscopic charcoal particles in peat

Comparison of two methods of counting microscopic charcoal particles in peat