extreme fires under warmer and drier conditions inferred from sedimentary charcoal morphotypes from opatcho lake central british columbia canada predictions of the extent of forest fires under warmer and drier conditions in boreal regions require knowledge of long term relationships between fire and climate however many long term studies

holocene fire regime changes from multiple site sedimentary charcoal analyses in the lourdes basin pyrenees france one lake and three peat bogs from the lourdes glacial basin france were used for macrocharcoal analyses and fire frequency reconstruction over the entire holocene 11700 years the chronology was based upon thirty three 14c ams dates comparison of the distribution of both charcoal accumulation rate char and fire return intervals showed that charcoal accumulation significantly differs between the lake and the peat bogs but that frequency calculation overcomes the disparity between these site types a composite frequency was built from the four individual records to assess regional versus local variability and fire regime controls by comparisons with regional fire activity holocene climatic oscillations and vegetation history the millennial variability can be depicted as follows relatively high frequency between 8000 and 5000 cal a bp up to 5 fires 500 yrs relatively low frequency between 5000 and 3000 cal a bp down to 0 fires 500 yrs and an increase between 3000 and 500 cal a bp up to 4 fires 500 yrs from 8000 to 5000 cal a bp fire frequency displays strong synchrony between sites and appears to be mostly driven by increased summer temperature characterizing the holocene thermal maximum htm on the contrary during the last 3000 years fire frequency was heterogeneous between sites and most probably human driven however higher frequency at the millennial scale during the mid holocene strongly suggests that the perception of human driven fire regime depends on the strength of natural controls

experiments in waterlogging and sedimentology of charcoal results and implications abstract fossil charcoal has a sporadic occurrence in sedimentary rocks since devonian time it is moderately common as a component of the organic material found in a wide variety of facies but there are also some notable concentrations which occur locally these occurrences have considerable palaeobotanical and palaeoecological value because the process of charring may result in excellent preservation of plant tissue if assemblages of charred material are to be used to interpret palaeoenvironments it is important to understand the behaviour of charcoal during transport from the site of the fire charcoal is an unusual sedimentary material because most fresh material floats but with prolonged immersion becomes waterlogged and sinks we carried out a series of waterlogging experiments on uncharred material and charcoal from a range of different plant types and tissues these show considerable variations in the rates of waterlogging of different charred and uncharred plant tissues and it is suggested that buoyancy contrasts are likely to result in separation during transport and deposition furthermore experiments in a flume tank have shown that the process of deposition of charcoal in sand is controlled by the rate of migration of bedforms which is in turn determined by depth flow velocity and sediment supply allochthonous assemblages of charred and uncharred plant debris will most probably be biased and not fully representative of the contemporaneous plants or vegetation the presence of charcoal concentrations may be used as an aid in interpreting palaeohydraulic conditions

a double bottom simulating reflector in the western ross sea antarctica 1 we present seismic evidence of the presence of gas hydrates and free gas in victoria land basin western ross sea antarctica the occurrence of gas hydrates is inferred from a bottom simulating reflector bsr the first identified in the ross sea area the gas presence was analyzed through targeted reprocessing of the multichannel seismic reflection data 3000 m streamer 120 channels 60 fold acquired in 1990 by the italian r v ogs explora the seismic data were reprocessed in order to increase the signal to noise ratio by adopting a true amplitude approach allowing a subsequent amplitude variations with offset avo analysis to extract information on both p and s wave reflectivity along a profile from the deeper basin to an intrabasin structural high the bsr evolves into crosscutting reflectors ccrs and enhanced amplitude reflectors ears locally another seismic event is interpreted to be a second bsr bsr0 identified about 150 m below the first bsr and is possibly related to the presence of a mixture of gases comprising methane and hydrocarbons with heavier molecular weight and therefore associated with a deeper hydrate stability zone the presence of faults controls the upward gas migration connecting the free gas zone below the bsr and the mud volcanoes and pockmarks on the seafloor the modeling of the hydrate equilibrium zone shows that the observed bsr bsr0 could be stable at the present pressure temperature conditions

tracking recorded fires using charcoal morphology from the sedimentary sequence of prosser lake british columbia canada abstract quantitative analyses of variations in morphological features of charcoal were undertaken in a 210pb dated sediment core from prosser lake british columbia canada seven morphological types of charcoal were defined by particle shape major minor axis ratio apparent porosity and progradation to unburned material the distribution of morphotypes and total charcoal abundances were assessed as a proxy for fire events recorded between 1919 and 2000 and to subsequent mechanisms of transportation sedimentation to lake sediments charcoal morphotypes showed distinct relationships to recorded area burned by fires fragile charcoal fragments with highly irregular porosity termed type m displayed the strongest correlation to burned area r2 0 51 p 0 0001 and did not produce any false positive signal for fires recorded within a radius of 20 km around the lake we infer that high porosity and low density type m fragments are aerially transported and directly deposited on the lake and that the fragility of type m charcoal prevents significant quantities from being secondarily transported and incorporated into the sedimentary record we propose that charcoal morphology is an important but underutilized technique that can yield important insights into fire type proximity and transportation sedimentation processes

relationships between charcoal particles in air and sediments in west central siberia production and size of charred particles determine transport and deposition in lakes lack of such data is a principal obstacle to interpretation of past fire from charcoal profiles our two part a

micromorphological study of irrigation canal sediments landscape evolution and hydraulic management in the middle gila river valley phoenix basin arizona during the hohokam occupation the hohokam were a long lived 300 1450 ad agrarian society in the deserts of southern arizona with an efficient irrigation system and a complex socio political organization dependent on environmental conditions they coped with hydrological and geomorphic changes which potentially had an impact on their cultural evolution irrigation canals were regularly maintained and or abandoned and their fills record secondary signatures of fluvial dynamics landscape change and land use micromorphological studies allow for the creation of a typology of canal fills based on semi quantitative measurements a synchronous and diachronic analysis of canal systems can then be undertaken by means of pedosedimentary correlation as part of cultural resource management projects on the gila river indian reservation south of phoenix studies have been conducted on the prehistoric santan irrigation system in use from the 10th to the 15th century ad phases of low flow were identified followed by alluvial fan flooding and seasonal deposition between the 10th 14th century ad sedentary early classic period during the 14th 15th century ad late classic period evidence of active erosion is initially recorded in the sediments followed by seasonal water supply and ultimately canal abandonment despite probable efficient irrigation

forests of the tropical eastern andean flank during the middle pleistocene inter bedded volcanic and organic sediments from erazo ecuador indicate the presence of four different forest assemblages on the eastern andean flank during the middle pleistocene radiometric dates 40ar 39ar obtained from the volcanic ash indicate that deposition occurred between 620 000 and 192 000 years ago examination of the organic sediment composition and the fossil pollen wood and charcoal it contains provides insight into depositional environment vegetation assemblage and fire history the high organic content and abundance of macro fossils found throughout the sediment suggest that during the period of deposition the local environment was either a swamp or a shallow water body the correlation of fire activity peaks in charcoal abundance with volcanic ash deposits through most of the record suggests that volcanoes were the main source of ignition the low abundance of grass typically 10 throughout the sedimentary sequence along with the low abundance of other taxa indicative of open vegetation suggests the persistence of forest at erazo four types of forest assemblage were identified with the first taxa as the most dominant i alnus arecaceae ii miconia melastomataceae combretaceae moraceae urticaceae iii arecaceae alnus and iv podocarpus with oreopanax sp and melastomataceae combretaceae changes in the forest floristic composition indicate high vegetation turnover and reassortment of taxa between upper and lower montane forests during the middle pleistocene as well as the persistence of forest cover

last glacial fire regime variability in western france inferred from microcharcoal preserved in core md04 2845 bay of biscay abstract high resolution multiproxy analysis microcharcoal pollen organic carbon neogloboquadrina pachyderma s ice rafted debris of the deep sea record md04 2845 bay of biscay provides new insights for understanding mechanisms of fire regime variability of the last glacial period in western france fire regime of western france closely follows dansgaard oeschger climatic variability and presents the same pattern than that of southwestern iberia namely low fire regime associated with open vegetation during stadials including heinrich events and high fire regime associated with open forest during interstadials this supports a regional climatic control on fire regime for western europe through fuel availability for the last glacial period additionally each of heinrich events 6 5 and 4 is characterised by three episodes of fire regime with a high regime bracketed by lower fire regime episodes related to vegetational succession and complex environmental condition changes

late miocene intensification of continentality in the black sea region the black sea basin is the sink for some of the largest european rivers and has acted as such since it was part of the eastern paratethys the late miocene to pliocene sedimentary record of the black sea documents several phases of strongly evaporitic conditions associated with extreme changes in regional hydrology here we present the first combined record of continental temperature soil type and biomass burning in the circum black sea region from the late miocene to the transition into pliocene 10 0 to 5 0 ma we use branched glycerol dialkyl glycerol tetraethers brgdgt to reconstruct mean annual air temperature mat and soil ph within the catchment of the black sea basin and complement these data with evidence from charcoal morphology as a proxy for burned biomass the brgdgt data reveal generally decreasing temperatures and acidic soils between 10 and 8 5 ma overlapping with increase in herbaceous cover in the black sea region the pontian flooding at 6 12 ma is characterized by large quantities of organic debris and charcoal fragments in the basin and is followed by cooling starting at 5 97 ma event that is superimposed on the tg 20 and tg 22 glacial peaks at 5 8 ma between 5 8 and 5 0 ma the brgdgts seem to be primarily derived from a cold steppe environment enhanced fire activity coinciding with generally cooler temperatures and a higher proportion of herbaceous plants are indicative of increased continentality between 5 8 and 5 0 ma in the black sea region

forest vegetation change and disturbance interactions over the past 7500 years at sasquatch lake columbia mountains western canada abstract fire is the most important abiotic disturbance in the interior cedar hemlock ich and engelmann spruce subalpine fir essf forest zone of southeastern british columbia canada other disturbances are also important such as defoliator and boring insect outbreaks windthrow diseases and rapid mass movements few studies have examined the interaction between multiple types of disturbances in these forests over long timescales here we present high resolution analyses of biomass burning erosion and vegetation assemblage changes at sasquatch lake nel02 a valley lake in the columbia mountains the 531 5 cm sediment core was radiocarbon dated and provided a 7500 year stratigraphy that was used for pollen macroscopic charcoal 150 m and sedimentologic analyses pollen and charcoal data provided evidence of forest composition changes and fire activity magnetic susceptibility loss on ignition and particle size distribution analyses characterised changes in erosion into the basin the results show that coniferous forests with a high abundance of pinus pollen had established in the catchment by the beginning of the record and were subject to intermittent burning and high energy erosive events tsuga heterophylla expanded by 4400 cal bp and the modern interior cedar hemlock forests expanded throughout the lower elevations due to increased regional continentality since 4500 cal bp high energy erosional inputs to the lake were less frequent from 3500 to 750 cal bp and rapid mass movements may have increased in frequency during the little ice age dendrochronological evidence in these stands suggests a mixed severity fire regime during past 300 years which has not been fully examined for charcoal based fire event reconstruction here we use identified peaks as an indicator of increased biomass burning and charcoal movement in the catchment in relation to peaks in allochthonous clastic material to understand the potential relationships between biomass burning and erosion events at multiple temporal scales in the catchment this suggests that post fire conditions up to several decades were subject to increased erosion to the lake and erosion events were more common during the early holocene establishment of dense essf and ich forests decreased siliciclastic input to the lake throughout the mid holocene until a recent rockslide the high resolution sampling of this lake sediment record provides long term evidence of variability in the relationships between vegetation cover fire and erosion at a catchment scale

stratigraphic charcoal analysis on petrographic thin sections application to fire history in northwestern minnesota results of stratigraphic charcoal analysis from thin sections of varved lake sediments have been compared with fire scars on red pine trees in northwestern minnesota to determine if charcoal data accurately reflect fire regimes pollen and opaque spherule analyses were completed from a short core to confirm that laminations were annual over the last 350 yr a good correspondence was found between fossil charcoal and fire scar data individual fires could be identified as specific peaks in the charcoal curves and times of reduced fire frequency were reflected in the charcoal data charcoal was absent during the fire suppression era from 1920 a d to the present distinct charcoal maxima from 1864 to 1920 occurred at times of fire within the lake catchment fire was less frequent during the 19th century and charcoal was substantially less abundant fire was frequent from 1760 to 1815 and charcoal was abundant continuously fire scars and fossil charcoal indicate that fires did not occur during 1730 1750 and 1670 1700 several fires occurred from 1640 to 1670 and 1700 to 1730 charcoal counted from pollen preparations in the area generally do not show this changing fire regime simulated sampling of the thin section data in a fashion comparable to pollen slide methods suggests that sampling alone is not sufficient to account for differences between the two methods integrating annual charcoal values in this fashion still produced much higher resolution than the pollen slide method and the postfire suppression decline of charcoal characteristic of my method but not of pollen slides is still evident consideration of the differences in size of fragments counted by the two methods is necessary to explain charcoal representation in lake sediments

fire and vegetation history from the coastal rain forest of the western oregon coast range high resolution charcoal and pollen analyses were used to reconstruct a 4600 yr long history of fire and vegetation near taylor lake in the wettest forests of coastal oregon today fires in these forests are rare because the season of ignition does not coincide with months of dry fuels from ca 4600 to 2700 cal yr b p fire episodes occurred at intervals of 140 30 yr while forest vegetation was dominated by disturbance adapted taxa such as alnus rubra from ca 2700 cal yr b p to the present fire episodes have become less common occurring at intervals of 240 30 yr and firesensitive forest taxa such as tsuga heterophylla and picea sitchensis have become more prominent fire occurrence during the midholocene was similar to that of the more xeric forests in the eastern coast range and suggests that summer drought was widespread after ca 2700 cal yr b p a decrease in fire episode frequency suggests that cooler conditions and possibly increased summer fog allowed the establishment of present day picea sitchensis forests within the watershed these results provide evidence that fire has been an important disturbance agent in the coast range of oregon and variations in fire frequency and climate have led to the establishment of present day forests c 2002 university of washington

holocene climate fire vegetation interactions at a subalpine watershed in southeastern british columbia canada abstract vegetation assemblages and associated disturbance regimes are spatially heterogeneous in mountain ecosystems throughout the world due to the complex terrain and strong environmental gradients given this complexity numerous sites describing postglacial vegetation and fire histories are needed to adequately understand forest development and ecosystem responses to varying climate and disturbance regimes to gain insight into long term historical climate fire vegetation interactions in southeastern british columbia canada sedimentological and paleoecological analyses were performed on a sediment core recovered from a small subalpine lake the pollen assemblages stomata and macroremains indicate that from 9500 to 7500 cal yr bp pinus dominated forests occurred within the catchment and alnus was also present climate was an important control of fire and fire frequency was highest at this time peaking at 8 fires 1000 yr 1 yet charcoal accumulation rates were low indicative of low terrestrial biomass abundance from 7500 to 4600 cal yr bp pinus decreased as picea abies and larix increased and fire frequencies decreased to 3 6 fires 1000 yr 1 since 7500 cal yr bp the fire regime varied at a millennial scale driven by forest biomass abundance and fuel accumulation changes local scale bottom up controls of fire increased in relative importance since at least 6000 cal yr bp

rapid deforestation of south island new zealand by early polynesian fires in most parts of the world where people have colonized and modified their landscapes for several millennia or more it is often difficult to discriminate anthropogenic burning from natural fire regimes that are linked to climate regimes new zealand provides a unique setting for identifying human influence on fire occurrence because it was settled recently c ad 1280 at a time when climates are considered to be similar to today late holocene pollen and charcoal records from new zealand provide striking evidence for initial polynesian m ori arrival being strongly associated with widespread burning and loss of native forest the duration of initial forest clearance and the spatial pattern of burning that led to this transformation are still poorly understood we present high resolution charcoal and pollen analyses of sediment cores from five lakes located on the deforested eastern side of the southern alps these records document the local fire history of the last 1000 years and the response of vegeta

near inertial oscillations interacting with mesoscale circulation in the southwestern japan east sea 1 the near inertial internal wave energy distribution is investigated in the southwestern japan east sea using vertical round trip travel time of sound data from 23 pressure sensor equipped inverted echo sounders piess and data from aanderaa recording current meters cms currents associated with low mode near inertial internal waves are slightly inclined and displace the thermocline vertically which can be detected in the band pass filtered records exhibit high near inertial energy distributions that vary interannually with changes observed in mesoscale circulation an explanation for this is offered as trapping of near inertial energy in anticyclonic regions which is supported by scatterplots of monthly rms band pass filtered at inertial frequency bands vs monthly mean relative vorticity the spectra from all but one deep cm exhibit a blue shift consistent with the equatorward propagation of near inertial waves the exception has the highest near inertial wave energy and is located near the center of a warm anticyclonic eddy

anthracology and taphonomy from wood gathering to charcoal analysis a review of the taphonomic processes modifying charcoal assemblages in archaeological contexts abstract a discussion on the representativeness of charcoal from archaeological contexts and their potential for palaeoecological reconstruction is presented the charcoal deposits studied are the result of human activities and natural processes difficult to separate on the basis of their effects only this is why taphonomy should not be limited to the study of charcoal after the extinction of fire as a result our questioning has been widened to include the entire succession of processes from past vegetation to the anthracological diagram we propose a review of the taphonomic processes affecting anthracological assemblages in archaeological contexts from wood gathering to the analysis of charcoal results human practices appear clearly as the first filter determining or conditioning the assemblage the combustion process can induce a double filter by limiting the taxonomic information and by falsifying the initial quantity of burned wood post depositional agents represent a third level of filters between the vegetation and the anthracological assemblage finally sampling and quantification methods can also induce a distortion of the assemblage the aim of this paper is to present the state of the discipline today the problems already solved and the questions that remain to be studied

assessing the spatial fidelity of sedimentary charcoal size fractions as fire history proxies with a high resolution sediment record and historical data abstract fire reconstructions provide context for modern rates of burning and inform predictions of fire regimes responses to climate and or ecological changes charcoal particles preserved in lake sediments are a widely employed fire proxy although many studies have calibrated the charcoal proxy the spatial scales of charcoal dispersal and source area remain disputed understanding the spatial fidelity of charcoal accumulation is increasingly important in light of recent efforts to aggregate multiple charcoal records to infer changes in regional continental and global scale fire regimes using a high resolution sediment record from swamp lake california we compare charcoal accumulation rate char variations of three size fractions of sedimentary charcoal 63 150 150 and 250 m to historical area burned data we find that macroscopic 250 and 150 m and mesoscopic 63 150 m charcoal source areas are within 25 35 and 150 km of swamp lake respectively we also use a dispersal model to confirm these findings our estimates of charcoal source area fall within the large range of estimates for forest fires in the literature further our methodology shows potential for constraining source areas of charcoal in sedimentary records which is requisite for the reliable inference of the spatial extent of fire in paleorecords

particle size evidence for source areas of charcoal accumulation in late holocene sediments of eastern north american lakes abstract two methods of analyzing charcoal in sediment reveal changes in charcoal accumulation across temperate eastern north america during the last several hundred years in one method the analyst counts mostly small particles that reflect regional emissions in the other the analyst counts only larger particles derived mostly from such local sources as catchment fires we used these methods to compare charcoal accumulation at 14 lakes from the prairie forest border in minnesota to eastern maine the two methods gave concordant accumulation rates for sediments of pre 1850 age at each of 4 lakes analyzed by both methods this concordance is consistent with the interpretation that pre 1850 emissions were controlled by broad scale factors such as climatically controlled regional differences in fuels and moisture since 1900 large particles decreased greatly and small particles decreased slightly in minnesota and wisconsin by contrast in the northeast the large particle accumulation has remained at the low values measured in pre 1900 sediments at most sites while small particles increased everywhere east of central new york and pennsylvania the observed patterns suggest that 1 large particles primarily reflect local fires that were common in the midwest before fire suppression became effective 2 large particles were rare in the northeast especially before extensive land clearance 3 small particles reflect regional combustion that increased in the northeast after extensive use of fire for land clearance and wood burning for industrial purposes of the 19th century and 4 small particles remain abundant in the midwest long after effective fire suppression probably because these well dispersed small particles have a large source area that extends beyond the local wildfires that account for large particles before european settlement

controls on the deposition of charcoal implications for sedimentary accumulations of fusain abstract the effects of formation temperature particle size water salinity and composition of suspended clay and substrate on the sedimentation of charcoal under agitated conditions in a wave tank were studied in a series of experiments the temperature of formation of charcoal has a strong effect on the rate at which charcoal becomes waterlogged examination of the microstructure of the chars formed at different temperatures shows that the formation of fractures within the wood affects the permeability and hence the rate of water penetration heating up to 300 c results in fusion of the cell walls which inhibits water penetration and shows the rate of settling at higher temperatures the cell walls progressively fracture increasing the permeability and the chars waterlog and settle aster the settling rates and hence the distribution of charcoal in sedimentary deposits are therefore controlled by the temperatures reached in the fire that generated the material this sorting related to temperature of charcoal formation has implications for the determination of the size of a paleowildfire from the volume of fusain in a sedimentary deposit salinity variations and the presence of a clay substrate were also shown to have a small effect on charcoal sedimentation rates

a 750 year fire history based on lake sediment records in central yellowstone national park usa a 750 year fire history was reconstructed for the central plateau of yellowstone national park from the deep water sediments of five lakes the charcoal record from a large lake provided a chronology of regional fires data from four small lakes were used to study local and extralocal fires the co occurrence of abundant charcoal and high magnetic susceptibility values at the same stratigraphic level was used as evidence of a local catchment fire and a charcoal peak without high magnetic susceptibility was ascribed to an extralocal fire or a local fire without a related erosion event the fire history was compared with the dendrochronologic fire record for the last 450 years and the close agreement provided the justification to extend the chronology back in time large areas of the region burned in ad 1988 c 1700 c 1560 and c 1440 from c 1220 to 1440 and c 1700 to 1987 intermediate to small areas burned the near absence of fires in the twentieth century prior to the large fires of 1988 is evi