Charcoal Record Research Articles

Tracing long‐term tropical montane ecosystem change in the Eastern Arc Mountains of Tanzania

ABSTRACTPollen, charcoal, stable carbon and nitrogen isotope, and radiocarbon analyses are used to reconstruct a palaeoenvironmental record from the Eastern Arc Mountains (EAM), Tanzania, dating back >45 000 years. A sedimentary hiatus covering the last glacial‐interglacial transition (LGIT) and early to mid Holocene follows the lead up to the Last Glacial Maximum (LGM) period. A late Holocene portion of the record is included as a modern analogue. Before 45 000 cal a BP, very low regional pollen counts imply open vegetation surrounding the site. Subsequently, the development of extensive montane forest characterizes a relatively mesic pre‐LGM. The transition into the LGM witnessed a marked shift from C3‐ to C4‐dominated biomass, representing an expansion of open forest dominated by grasses. These changes may be attributed to a combination of enhanced moisture stress and CO2 limitation, factors that may have been exacerbated by an intensive fire regime, as evident from the charcoal record. This is supported by a decrease in montane forest taxa, coupled with an associated expansion of C4 graminoids and ericaceous heathland to form a montane grassland mosaic similar to that previously recorded on other East African mountains around the time of the LGM but not, to date, having been shown in the Eastern Arc Mountains.

Climatic influence upon early to mid-Holocene fire regimes within temperate woodlands: a multi-proxy reconstruction from the New Forest, southern England

A combined pollen, charcoal and climatic record is presented from Cranes Moor, southern England, covering the period c. 10 500–5850 cal a BP. It is shown that the occurrence of burning is closely related to natural processes, including prevailing climatic conditions and vegetation composition. These burning events are often linked to an increase in the summer moisture deficit, implying that the timing of burning events is linked to periods of warmer/drier climate during the Holocene Thermal Maximum (c. 11 000–5000 cal a BP). These events play an important role in the vegetation composition and succession around the site. The nature of the burning recorded at the site shows strong similarities with other records from northern Europe. This study throws caution on suggestions that fire in the Holocene record from areas such as the British Isles is linked only to human activity, and enhances the possibility that natural fire incidence played an important role in natural woodland structure dynamics.

POSTGLACIAL CLIMATE AND FIRE‐MEDIATED VEGETATION CHANGE ON THE WESTERN OLYMPIC PENINSULA, WASHINGTON

It is difficult to study responses of old-growth forests to climate change due to significant inertia in the population response of established trees to a change in climate. Paleoecological approaches, such as pollen analysis from small lakes, may address such questions, but due to limitations in pollen data it is difficult to understand population responses at the grain at which trees are competing. This study used a stratigraphic record of needle macrofossils and charcoal, representing local forests and fires, to show that fire could break the forest's inertia to climate change, but often only several centuries after landscape-level vegetation change was underway. Forest on the northwest shore of Yahoo Lake, on the western portion of the Olympic Peninsula. Old-growth forests of western redcedar, Pacific silver fir, and western hemlock surround the lake. Photograph by Daniel Gavin. These photographs illustrate the article “Postglacial climate and fire-mediated vegetation change on the western Olympic Peninsula, Washington,” by Daniel G. Gavin, Linda B. Brubaker, and D. Noah Greenwald, tentatively scheduled to appear in Ecological Monographs 83(4), November 2013. doi: http://dx.doi.org/10.1890/12-1742.1

Novel Application of Confocal Laser Scanning Microscopy and 3D Volume Rendering toward Improving the Resolution of the Fossil Record of Charcoal

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

La gestión de recursos leñosos por cazadores-recolectores transicionales en los sectores intermedios de Antofagasta de la Sierra (Catamarca, Argentina): el caso de alero sin cabeza

This paper presents the results of the analysis of charcoal record corresponding to transitional hunter-gathereroccupations of the Alero Sin Cabeza site, dated ca.3500 years BP. We are interested in ancient management practicesof plant resources and, particularly, the supply of woody raw materials. The results indicate the use of different woodfuel local species, predominating taxa Adesmia sp. a firewood with good fuel properties. We propose the use of Tolarand Campo as main woody procurement areas, as well as the articulation with more remote areas, such as Pajonal.It is proposed that during hunter-gatherer transitional occupations of this site, forage for woody materials prioritizednear-site areas, complemented with firewood collections conducted in more distant areas. This is consistent with theoccurrence of reduced residential mobility around 3500 years BP.

A MIS 3 charcoal and pollen record and quantitative precipitation inferences from the Jingerwa section of the Nihewan Basin, north-central China

Pollen and charcoal data from the Jingerwa section of the Nihewan Basin, north-central China, were used to reconstruct vegetation and climate changes during Marine Isotope Stage (MIS) 3. Mean annual precipitation changes were quantified by applying pollen-climate transfer functions. Sparse vegetation cover dominated by herbs indicates relatively dry climate between 51 and 43 cal ka BP. Between 43 and 35 cal ka BP, a Pinus-dominated forest reached its maximum extent, implying that climate was wetter than today. Severe fire episodes during that period suggest warm temperatures. Between 35 and 32 cal ka BP, forest retreat and the expansion of dryland vegetation are indicative of drier climates. Slightly wetter conditions prevailed between 32 and 29 cal ka BP, as indicated by the expansion of ferns. Our results suggest that the climate conditions in the Nihewan Basin during middle and late MIS 3 were probably wetter than today. This may have been caused by intensification of Asian monsoon circulation in response to greater insolation in June at 30°N. However, increases in summer temperatures and evaporation, triggered by peak summer insolation levels, may have led to a reduction in humidity around 35 cal ka BP.

Holocene fire frequency variability in Vesijako, Strict Nature Reserve, Finland, and its application to conservation and management

Fire disturbance is considered paramount for regeneration and biodiversity in the boreal forest with prescribed burning widely advocated in present day forest management. Palaeoecological knowledge is beneficial in understanding the role of fire as a driver of past vegetation dynamics. We use a sedimentary pollen and charcoal record to reconstruct 5000years of fire and vegetation history from a small forest hollow (approximate area 12m2) in the Vesijako Strict Nature Reserve, currently one of the few remaining old-growth forest stands in southern Finland. Results indicate three distinct periods in the environmental history (1) 5000–2000cal. yrs. BP; semi-natural low frequency (430year return period), low intensity fires in a diverse mixed stand with little evidence of anthropogenic disturbance and an expanding Picea abies (Norway spruce) population (2) 2000–750cal. yrs. BP; anthropogenic-driven high frequency (180year return period), high intensity stand-replacing fires in a low diversity stand with evidence of slash and burn cultivation and a decline of Picea population, (3) 750cal. yrs. BP to present day; fire absence through a reduction in human-induced fire or active fire suppression and the expansion of the currently dominant Picea forest. The changing fire frequency has had a major influence on the forest composition during the last 5000years. The loss of floristic diversity is associated with an increase in the human use of fire and without this human interference the previously high biodiversity in the stand may have remained up until the present day. If fire remains absent in Vesijako then it is likely that the Picea population will continue to dominate in the stand supporting a negative feedback mechanism that will result in lower frequency, higher intensity fires in the future.

Paleofire reconstruction based on an ensemble‐member strategy applied to sedimentary charcoal

AbstractPaleofire events obtained from the statistical treatment of sedimentary charcoal records rely on a number of assumptions and user's choices, increasing the uncertainty of reconstructio\ns. Among the assumptions made when analyzing charcoal series is the choice of a filtering method for raw Charcoal Accumulation Rate (CHARraw). As there is no ultimate CHARraw filtering method, we propose an ensemble‐member approach to reconstruct fire events. We modified the commonly used procedure by including a routine replicating the analysis of a charcoal record using custom smoothing parameters. Dates of robust fire events, uncertainties in fire‐return intervals and fire frequencies are derived from members' distributions. An application of the method is used to quantify uncertainties due to data treatment in two CHARraw sequences from two different biomes, subalpine and boreal.

Carbon in Korea

The history of carbon science in Korea is summarized in this review. There is a record of charcoal being used to maintain collections of woodblock prints at a stable relative humidity such as the Tripitaka Koreana that were engraved from 1237 to 1248 and are designated a World Heritage Site by UNESCO. Carbon research in Korea has been led by researchers educated in foreign countries such as Germany, Japan, US, and England since the 1970s. These research activities resulted in the foundation of the Korean Carbon Society (KCS) in 1999 and its status was enhanced by hosting Carbon 2005 in Gyeongju. Nano-carbon research has further increased in universities following the award of the Nobel Prizes for research on fullerene and graphene. The regional governments of Jeonju City and Jeonbuk Province have supported the “Carbon Valley” project by establishing the Jeonju Institute of Machinery and Carbon Composites (JMC) in 2003 and inviting a Korea Institute of Science & Technology (KIST) branch, named the Institute of Advanced Composite Materials to focus on research on carbon composites in 2008. In 2011, JMC organized the 1st Carbon Industry Forum with strong support from carbon industries. In 2012, the Korean government supported the research of the Institute of Basic Science (IBS) to promote basic science in Korea and two carbon-related centers were selected. [TANSO 2013 (No. 257) 145–148]

Climate change, vegetation history, and agricultural activity of Lake Li-yu Tan, central Taiwan, during the last 2.6 ka BP

Pollen record derived from the sediment core of Lake Li-yu Tan, central Taiwan, provides valuable information of vegetation history, climate change, and agricultural activity. Subtropical evergreen forests dominated the uplands surrounding this lake from 2.6 ka BP, indicating the climate was warm. However, the appearance of warm-temperate forest vegetation suggests two relatively cool periods, prior to 2.3 ka BP and between 1.6 and 1.2 ka BP. Based on the presence of cultivated pollen, including Poaceae (>40 μm), Lagerstroemia, and Melia, agricultural activity was expansive between 1.6 and 1.2 ka BP and from 0.6 ka BP. This study also provides the first charcoal record in Taiwan. Natural fires occurred frequently during the interval 2.6 to 1.7 ka BP, as shown by continuous and stable charcoal influxes. Decline in charcoal influxes elucidates that fires decreased during the interval 1.7 to 1.6 ka BP. Fire events resulting from agricultural activity occurred between 1.6 and 1.2 ka BP. The high fluctuation of charcoal influxes during this period also indicates charcoal production by humans, presumably near the lake, based on the appearance of large charcoal particles (>500 μm). Fires decreased gradually from 1.2 ka BP.

Fire activity in North West Africa during the last 30,000 cal years BP inferred from a charcoal record from Lake Ifrah (Middle atlas–Morocco): Climatic implications

Paleofire activity in North Africa and its connections with past climatic changes still remains poorly documented. A new multiproxy analysis using mineralogy, geochemistry and microcharcoal data from Lake Ifrah (Middle Atlas, Morocco) provides new insights for better understanding paleofire occurrence from the Last Glacial Maximum to the present. The comparison between microcharcoal distribution and lacustrine multiproxy data highlights the variability of paleofire activity that is interpreted in term of long-term climate-driven changes. From 20,000 to 13,000calyr BP, the concentration in microcharcol was very low in connection with low fire activity and cold climate. The early to mid-Holocene (between 10,800 and 4,500calyr BP) marked a significant increase in microcharcoal abundance which likely testifies to regional emissions from forest fires. Such biomass burning events were associated to prolonged periods of drought, as inferred by synchronous abrupt decreases in surface runoff input records (e.g. organic matter, trace elements and magnetic susceptibility) and increases in carbonate content, calcite and Mg–calcite concentrations.

The charcoal record in peat and mineral soil across a boreal landscape and possible linkages to climate change and recent fire history

This study combines tree-ring and charcoal data to explore possible drivers of the charcoal record and its spatial variation in a boreal Norwegian forest landscape. Peat and mineral soil samples were collected in a multiple site sampling approach and the amount of charcoal in the peat is related to fire history, Holocene climate variation, major shifts in the vegetation composition, and fuel availability. Dendrochronologic dating was used to reveal the fire history over the last 600 years with spatial and temporal accuracy, and AMS radiocarbon dating of 20 peat columns and their charcoal records from four peatlands was used to elucidate the fire history over the Holocene. The average amount of charcoal was about 2.5 times higher in the mineral soil than in the peat (270 versus 100 g/m2, respectively), and there were considerable between- and within-site variations. There was no relationship between the age of a given peatland and its content of charcoal, nor between the amount of charcoal in a given peatland and in the neighboring mineral soil. Although most of the charcoal mass in the peatlands was found in parts of the peat columns originating from relatively warm climatic periods and from the period before the local establishment of Norway spruce ( Picea abies), charcoal accumulation rates (per 1000 yr) were higher during cold climatic periods and similar before and after spruce establishment. Recent fires showed up to a low degree in the peat columns. On fine spatial scales (1–10 m), fuel quality and distribution together with fire behaviour throughout millennia are likely to be responsible for variations in the charcoal record. On the landscape scale (100–1000 m), the charcoal records were site-specifically idiosyncratic, presumably due to topography, distribution of fire breaks and fuel types, and human land use, coupled with long-term variations inherent in these factors.

Climate and vegetation change during the late-glacial/early-Holocene transition inferred from multiple proxy records from Blacktail Pond, Yellowstone National Park, USA

A series of environmental changes from late-glacial ice recession through the early Holocene are revealed in a 7000-yr-long record of pollen, charcoal, geochemistry, and stable isotopes from Blacktail Pond, a closed-basin lake in Yellowstone National Park. Prior to 11,500calyrBP, cool conditions dominated, fire activity was low, and alpine tundra and Picea parkland grew on the landscape. A step-like climate change to warm summer conditions occurred at 11,500calyrBP. In response, fire activity increased facilitating a transition from Picea parkland to closed Pinus forest. From 11,500 to 8280calyrBP, warm summers and abundant moisture mostly likely from high winter snowfall supported closed Pinus contorta forests. Cooler drier summer conditions prevailed beginning 8280calyrBP due to decreased summer insolation and winter snowpack, and lower parkland developed. The timing of vegetation change in the Blacktail Pond record is similar to other low- and middle-elevation sites in the northern Rocky Mountains during the late-glacial period, suggesting local plant communities responded to regional-scale climate change; however, the timing of vegetation changes was spatially variable during the early and middle Holocene due to the varying influences of strengthened summer monsoons and subtropical high on regional precipitation patterns.

Grass páramo as hunter-gatherer landscape

Tussock grass páramo constitutes the dominant vegetation of the high tropical Andes and cordilleras of Costa Rica. Its distribution, composition and the location of the upper forest line are ascribed, by broad consensus, to climate. The zonal argument finds support in the altitudinal movements of páramo during the Pleistocene, clearly responding to changes in precipitation and temperature. I ask here, however, if the principal ecological variables driving post-Pleistocene páramos are circumscribed solely by climate. The combined pollen, charcoal and archaeological evidence generated in recent decades suggests a distinct Holocene etiology. Five principal conclusions emerge: (1) the sedimentary charcoal record establishes that grass páramo is a fired landscape, (2) natural sources of fire, specifically volcanoes and lightning, are incapable of generating the fire regime apparent in the sedimentary charcoal record, (3) burning at most sites intensified significantly between 13,000 and 11,000 cal. yr BP, and maintained heightened levels during the Holocene, (4) archaeological findings suggest that the original settlement of the Andes coincided with the sedimentary charcoal rise, and (5) the subsistence logic of hunter-gatherers argues strongly for firing the vegetation to increase resource productivity and reliability. From the pioneering mixed vegetation after deglaciation, anthropic fire selected in favor of tussocks and against woody species, generating a novel plant association. I propose, therefore, that Holocene grass páramo is not zonal vegetation, but rather a hunter-gatherer landscape.

Joseph Birdsell's legacy – a database of biological variation in modern Australian Indigenous peoples

The extent of prehistoric human impact on the environment is a contentious topic in various palaeo-environmental sciences. The long history of humans in Australia and its extensive fire-prone biota makes this continent a key research area for better characterization of prehistoric human–fire interactions. Here we use statistically robust cross-correlation of archaeological radiocarbon data (n = 4102 ages from 1616 sites) and a new synthesis of charcoal records (n = 155 sites) to test for any relationship between people and fire over the last 20,000 years at continental and regional (25–45°S) scales. We find that the statistical correlation between the two datasets is weak at both spatial scales, with short-lived synchronous responses only in the terminal Pleistocene–Holocene transition, at the onset of the mid-Holocene climatic optimum (~ 10–7 ka) and during significant transitions of El Niño Southern Oscillation (~ 5–4 ka and 1.2–0.8 ka). One interpretation of this is that Aboriginal populations were implementing ‘fire-stick farming’ only intermittently during periods of societal stress resulting from climatic variability. However, the synchronicity of the correlations with climate changes, along with the low populations through much of this time, suggests that both datasets were independently responding to external climatic forcing. Under either scenario, a lack of significant change in the charcoal record implies that there were no long-lasting impacts to the environmental biota, and macro-scale palaeoenvironmental records prior to European colonization largely reflect responses to non-human influences. While we do not discount the possibility of systematic or deliberate manipulation of fire regimes at local spatial scales, we conclude that human control of fire by prehistoric people in Australia is not evident at broad landscape levels. This conclusion contradicts persistent suggestions of Australian-wide land management and the pervasiveness of the impacts of ‘fire-stick farming’.

Vicariant models for the initial colonization of North America

The extent of prehistoric human impact on the environment is a contentious topic in various palaeo-environmental sciences. The long history of humans in Australia and its extensive fire-prone biota makes this continent a key research area for better characterization of prehistoric human–fire interactions. Here we use statistically robust cross-correlation of archaeological radiocarbon data (n = 4102 ages from 1616 sites) and a new synthesis of charcoal records (n = 155 sites) to test for any relationship between people and fire over the last 20,000 years at continental and regional (25–45°S) scales. We find that the statistical correlation between the two datasets is weak at both spatial scales, with short-lived synchronous responses only in the terminal Pleistocene–Holocene transition, at the onset of the mid-Holocene climatic optimum (~ 10–7 ka) and during significant transitions of El Niño Southern Oscillation (~ 5–4 ka and 1.2–0.8 ka). One interpretation of this is that Aboriginal populations were implementing ‘fire-stick farming’ only intermittently during periods of societal stress resulting from climatic variability. However, the synchronicity of the correlations with climate changes, along with the low populations through much of this time, suggests that both datasets were independently responding to external climatic forcing. Under either scenario, a lack of significant change in the charcoal record implies that there were no long-lasting impacts to the environmental biota, and macro-scale palaeoenvironmental records prior to European colonization largely reflect responses to non-human influences. While we do not discount the possibility of systematic or deliberate manipulation of fire regimes at local spatial scales, we conclude that human control of fire by prehistoric people in Australia is not evident at broad landscape levels. This conclusion contradicts persistent suggestions of Australian-wide land management and the pervasiveness of the impacts of ‘fire-stick farming’.

Just how far and just how fast? Clovis in Late Glacial North America

The extent of prehistoric human impact on the environment is a contentious topic in various palaeo-environmental sciences. The long history of humans in Australia and its extensive fire-prone biota makes this continent a key research area for better characterization of prehistoric human–fire interactions. Here we use statistically robust cross-correlation of archaeological radiocarbon data (n = 4102 ages from 1616 sites) and a new synthesis of charcoal records (n = 155 sites) to test for any relationship between people and fire over the last 20,000 years at continental and regional (25–45°S) scales. We find that the statistical correlation between the two datasets is weak at both spatial scales, with short-lived synchronous responses only in the terminal Pleistocene–Holocene transition, at the onset of the mid-Holocene climatic optimum (~ 10–7 ka) and during significant transitions of El Niño Southern Oscillation (~ 5–4 ka and 1.2–0.8 ka). One interpretation of this is that Aboriginal populations were implementing ‘fire-stick farming’ only intermittently during periods of societal stress resulting from climatic variability. However, the synchronicity of the correlations with climate changes, along with the low populations through much of this time, suggests that both datasets were independently responding to external climatic forcing. Under either scenario, a lack of significant change in the charcoal record implies that there were no long-lasting impacts to the environmental biota, and macro-scale palaeoenvironmental records prior to European colonization largely reflect responses to non-human influences. While we do not discount the possibility of systematic or deliberate manipulation of fire regimes at local spatial scales, we conclude that human control of fire by prehistoric people in Australia is not evident at broad landscape levels. This conclusion contradicts persistent suggestions of Australian-wide land management and the pervasiveness of the impacts of ‘fire-stick farming’.

Exploring the requirement for anthropogenic disturbance to assist the stand-scale expansion of Fagus sylvatica L. outside southern Scandinavia

This paper presents a pollen and charcoal record from a forest hollow located in northern Germany. The initial stand-scale colonization and subsequent expansion of the species Fagus sylvatica (European Beech) is examined and compared with examples from southern Scandinavia. In the early Holocene, a diverse forest stand is present. The recording of Fagus sylvatica in nine contiguous samples over the time period 8600–7950 cal. yr BP, constrained by three AMS dates, suggests its presence close to the hollow. This early occurrence is critiqued against the current paradigm of mid- to late-Holocene Fagus sylvatica spread in northern Central Europe. Between 6200 and 2900 cal. yr BP, Fagus sylvatica was a minor constituent of the forest community but did not expand despite periods of favorable conditions including relatively open forest landscape, wetter-cooler climatic conditions and a suitable fire regime. The eventual expansion of Fagus sylvatica, around 2900 cal. yr BP, is initiated by significant anthropogenic disturbance around the hollow. After the initial phase of expansion, its growing importance in the forest was potentially aided by a period of wetter-cooler conditions and a switch in the fire regime from one of regular episodes, to one of sporadic occurrence. Two fire events and an increase in anthropogenic activity occur at the same time as the decline in the relative abundance of Fagus sylvatica at 1200 cal. yr BP. This site highlights the strong anthropogenic influence on the species dynamics throughout the late Holocene.

A new Middle Pleistocene interglacial record from Denmark: Chronostratigraphic correlation, palaeovegetation and fire dynamics

Previously only three terrestrial interglacial periods were known from southern Scandinavia, all of which could be relatively easily correlated within the central European stratigraphical framework. Here, we present a new interglacial–interstadial pollen, plant macrofossil and charcoal record from Trelde Klint, Denmark, and analyse its biostratigraphy, correlation with other European records, vegetation development, fire dynamics and absolute dating. Except for a slight truncation of the early part of the record, the pollen stratigraphy exhibits a full interglacial succession, including temperate trees (Quercus, Ulmus and Tilia) during its mesocratic stage. Macrofossil analysis allowed identification to species level for Quercus robur, Picea abies and two mosses. Conifers (Pinus and Picea) dominate the pollen record of the interglacial sequence, and the occurrence of Larix pollen in the top part of the interglacial record as well as in the interstadial sediments is especially indicative of this interglacial. The overall diversity of tree genera is rather low. These biostratigraphical features suggest that Trelde Klint is unique among Danish records, but it is similar to records from northern Germany. Numerical analyses (REVEALS and DCA) indicate that forests during the temperate stage were dense and that vegetation openness increased only towards the end of the interglacial, accompanied by increased fire occurrence. A short interstadial sequence with a dominance of Pinus and Betula and the presence of Larix is present above the interglacial deposit. We argue that lack of attention to differences in fire regimes may hamper understanding of between‐site correlations of interglacial pollen records. OSL dating, using a novel feldspar technique, yields an average age of 350±20 ka for the sandy sediments above the interglacial layers at Trelde Klint, suggesting that the whole interglacial–interstadial succession belongs to Marine Isotope Stage 11.

Fire regimes of quaking aspen in the Mountain West

Quaking aspen (Populus tremuloides Michx.) is the most widespread tree species in North America, and it is found throughout much of the Mountain West (MW) across a broad range of bioclimatic regions. Aspen typically regenerates asexually and prolifically after fire, and due to its seral status in many western conifer forests, aspen is often considered dependent upon disturbance for persistence. In many landscapes, historical evidence for post-fire aspen establishment is clear, and following extended fire-free periods senescing or declining aspen overstories sometimes lack adequate regeneration and are succeeding to conifers. However, aspen also forms relatively stable stands that contain little or no evidence of historical fire. In fact, aspen woodlands range from highly fire-dependent, seral communities to relatively stable, self-replacing, non-seral communities that do not require fire for persistence. Given the broad geographic distribution of aspen, fire regimes in these forests likely co-vary spatially with changing community composition, landscape setting, and climate, and temporally with land use and climate – but relatively few studies have explicitly focused on these important spatiotemporal variations. Here we reviewed the literature to summarize aspen fire regimes in the western US and highlight knowledge gaps. We found that only about one-fourth of the 46 research papers assessed for this review could be considered fire history studies (in which mean fire intervals were calculated), and all but one of these were based primarily on data from fire-scarred conifers. Nearly half of the studies reported at least some evidence of persistent aspen in the absence of fire. We also found that large portions of the MW have had little or no aspen fire history research. As a result of this review, we put forth a classification framework for aspen that is defined by key fire regime parameters (fire severity and probability), and that reflects underlying biophysical settings and correlated aspen functional types. We propose the following aspen fire regime types: (1) fire-independent, stable aspen; (2) fire-influenced, stable aspen; (3) fire-dependent, seral, conifer-aspen mix; (4) fire-dependent, seral, montane aspen-conifer; and (5) fire-dependent, seral, subalpine aspen-conifer. Closing research gaps and validating our proposed aspen fire regime classification will likely require additional site-specific research, enhanced dendrochronology techniques, charcoal and pollen record analysis, spatially-explicit modeling, and other techniques. We hope to encourage development of site-appropriate disturbance ecology characterizations, in order to aid efforts to manage and restore aspen communities and to diagnose key factors contributing to changes in aspen.