late quaternary pollen records from two ugandan mires evidence for environmental changes in the rukiga highlands of southwest uganda abstract high resolution pollen data from two mires in the rukiga highlands southwest uganda ahakagyezi swamp and muchoya swamp provide detailed evidence of the environmetal history of the region since ca 42 000 yr b p according to these data there a was period pre ca 42 000 yr b p when climatic conditions were similar to the present conditions considerably colder and drier than the present occurred during two periods in the past pre ca 42 000 yr b p to ca 32 000 yr b p and ca 21 000 yr b p to ca 12 000 yr b p the most recent period of climatic improvement began ca 14 000 yr b p moist lower montane forest colonised the muchoya catchment by ca 11 100 yr b p and the ahakagyezi catchment by ca 10 600 yr b p indicating the establishment there of climatic conditions broadly similar to the present pollen data from both mires reveal forest disturbances beginning ca 2200 yr b p this disturbances is likely to have been human induced

the transition from glacimarine to marine conditions during the last deglaciation in eastern skagerrak the paleoceanographic and paleoenvironmental evolution is described in the eastern skagerrak separable stratigraphic units in seismic profiles and twelve piston cores document a changing balance between erosion and accumulation since the latest deglaciation sediment supply and water depth but also whether the water mass is stratified or not are the important parameters in the processes controlling the depositional environment the cores can be divided into two main units a lower well consolidated and clay rich glacimarine mud with low organic content and a silty sandy marine mud with relatively high organic content the boundary between these two main units consists of an erosional surface overlain by a coarse grained lag the deposition of the lower glacimarine mud started directly after deglaciation at about 18 0 kyr bp a major change in the sedimentation conditions at about 9 0 kyr bp led to a change from depositional to erosional conditions the erosion has presumably removed a great part of the earlier deposits creating the erosional surface which is present in the entire study area several dated samples above and below the erosional surface indicate a hiatus of about 10 kyr in the south the conditions changed again at about 5 0 cal kyr bp allowing accumulation of the marine mud while in the northern part erosive conditions continue to prevail in the northern part the marine mud is only deposited in limited areas preferably sheltered areas along the coast

charcoal analysis for paleoenvironmental interpretation a chemical assay a nitric acid digestion and ignition technique developed to measure relative frequencies of charcoal in lake and bog sediments measures the weight of charcoal relative to the dry weight of the sample percentage charcoal and gives results comparable to counting of microscopic charcoal differences in the two techniques caused by changes in sediment type were found especially in postsettlement and late glacial parts of cores charcoal values from sediments less than 100 yr old cannot be compared to older charcoal values unless wood charcoal and charcoal from fossil fuel burning are separated microscopically tests of this chemical assay on mixtures of known weights of charcoal leaves and sand give correlations between observed and expected values of 0 99 to 1 00

late quaternary vegetation and fire dynamics on mount kenya abstract pollen and charcoal data generated from a 1469 cm core radiocarbon dated to 26 430 14 c yr bp recovered from rumuiku swamp on the southeast of mount kenya are used to document changes in the distribution and composition of montane vegetation and fire regimes over the late quaternary throughout the transition from the last glacial maximum lgm high resolution sub centennial scale analysis documents a highly dynamic ecosystem and fire regime the pollen record shows that under a cool but rather moist lgm climate ericaceae and stoebe species shifted down slope more than 1000 m relative to the present day rather than simple altitudinal lowering of current vegetation zonation these taxa formed a vegetation assemblage that mixed high altitude components with relatively lowland taxa in particular juniperus that is presently found at altitudes lower than the study site but on the drier side of mount kenya there is noticeable addition and co dominance of hagenia to the ecosystem from 20 500 14 c yr bp until around 14 000 14 c yr bp when a mix of ericaceous belt and upper montane forest taxa such as artemisia polycias schefflera and stoebe dominated the initial development of montane forest reduced levels of hagenia juniperus olea and podocarpus are recorded about the time of the younger dryas with highly variable presence of more mesic taxa such as polyscias and schefflera this development of montane forest over the late pleistocene to holocene transition reflects a significant reorganization of the ecosystem composition that was heavily influenced by a variable fire regime shifts in vegetation composition reflect the onset of a warmer moist climate from the beginning of holocene as mixed montane forest became more established the latter part of the holocene registers human impact and forest clearance with increased anthropogenic impact marked by a transition to open vegetation and increased fire frequency

late quaternary stratigraphic charcoal records from madagascar the classic view regarding the cause of the extinction of at least 17 species of large mammals birds and reptiles in madagascar during the late holocene implicates human use of fire to modify the environment however analysis of the charcoal stratigraphy of three sediment cores from madagascar shows that late pleistocene and early to mid holocene sediments deposited prior to human settlement often contain more charcoal than postsettlement and modern sediments this observation which is confirmed by independent measurements from direct assay and palynological counting techniques suggests that widely held but previously untested beliefs concerning the importance of anthropogenic fires in late holocene environmental changes and megafaunal extinctions of madagascar may be based on an overly simplified version of actual prehistoric conditions moderate to low charcoal values characterized only the late holocene millennia immediately prior to the presumed time of arrival of the first settlers human settlement is probably indicated in the stratigraphy by the sharp rise in charcoal content observed beginning ca 1500 yr b p fire appears to be a significant natural component of prehuman environments in madagascar but some factor probably climate has modulated the extent of natural burning

the selection of sites for paleovegetational studies the judicious selection of sites for paleovegetational and paleoclimatic studies permits paleoecologists to answer specific research questions that go beyond primary descriptions of past vegetation we present a model that describes the relationship between basin size and pollen source area and predicts the proportions of local extralocal and regional pollen sampled by lake basins of different size the distinctive sampling properties of lakes peats and small hollows can be exploited to provide details of pattern in paleovegetation so long as attention is given to the limitations and problems of these types of sites combinations of site types in a single study most fully exploit the information contained in sediments

late quaternary vegetation dynamics in a biodiversity hotspot the uluguru mountains of tanzania abstract late quaternary vegetation history and environmental changes in a biodiverse tropical ecosystem are inferred from pollen charcoal and carbon isotope evidence derived from a 48 000 yr sedimentary record from the uluguru mountains a component of the eastern arc mountains of kenya and tanzania results indicate that eastern arc forest composition has remained relatively stable during the past 48 000 yr long term environmental stability of the eastern arc forests has been proposed as a mechanism for the accumulation and persistence of species during glacial periods thus resulting in the diverse forests observed today the pollen and isotope data presented here indicate some marked changes in abundance but no significant loss in moist forest taxa through the last glacial maximum thereby providing support for the long term environmental stability of the eastern arc anthropogenic activities including burning and forest clearance were found to play a moderate role in shaping the mosaic of forest patches and high altitude grasslands that characterise the site today however this influence was tempered by the inaccessibility of the mountain

palaeoenvironmental changes during the last ca 8590 calibrated yr 7800 radiocarbon yr in the dry forest ecosystem of the patia valley southern colombian andes a multiproxy approach two sediment cores were recovered from two swamps in the dry forest lowland ecosystem of the patia valley colombia the 500 cm long core el patia 1 was analysed using diatoms pollen lithostratigraphy geochemistry charcoal and radiocarbon dates the 270 cm long core patia 2 was analysed using pollen lithostratigraphy and radiocarbon dates the environmental reconstruction includes the local development and history of the patia 1 swamp and the regional vegetation history of the two swamps the environmental reconstruction shows a fluvial system in the area before 7830 14c yr bp ca 8590 cal yr bp after this date the river gradually moved away leading to the formation of the swamp patia 1 open vegetation with patches of dry forest surrounded the swamp between 7670 and 6860 14c yr bp 8350 7690 cal yr bp the swamp become partially isolated from the river and was a permanent water body which was alkaline and mesotrophic during this period the surroundings were covered by dry forest from 6860 to 5870 14c yr bp 7690 6690 cal yr bp the swamp was totally isolated from the river and suffered from frequent periods of desiccation and erosion from 5870 to 3570 14c yr bp 6690 3890 cal yr bp the swamp turned into a marsh terrestrial environment and in the surrounding area the dry forest alternated with open vegetation it is possible that there were human impacts on the environment during this period between 3570 and 1990 14c yr bp 3890 2000 cal yr bp unstable conditions prevailed after 1990 14c yr bp 2000 cal yr bp swamp conditions of permanent water were re established open vegetation surrounded the swamp agriculture and human activities were present and have continued since then the climatic reconstruction suggests an increase in humidity at ca 7670 14c yr bp 8350 cal yr bp and a dry climate between 6860 and 5870 14c yr bp 7690 6690 cal yr bp

late pleistocene and holocene history at mubwindi swamp southwest uganda abstract deposits beneath mubwindi swamp provide a partial record of vegetation history since at least 43 000 yr ago we studied pollen from two cores and obtained nine radiocarbon ages from one of these cores and three radiocarbon ages from the other pollen deposited before and soon after the last glacial maximum represents vegetation very different from the modern vegetation of the mubwindi swamp catchment although species now associated with higher altitudes were dominant some elements of moist lower montane forest persisted possibly because of favorable soils or topography the pollen data provides evidence for a late glacial montane forest refuge near mubwindi swamp moist lower montane forest became much more widespread soon after the glacial maximum the only irrefutably holocene sediments from mubwindi swamp date to the past 2500 yr during this time a combination of climatic and human induced changes in vegetation can be seen in the pollen records

middle holocene dry period in the northern midwestern united states lake levels and pollen stratigraphy abstract four cores from lake mendota in the yahara river valley of south central wisconsin provide pollen charcoal and sediment stratigraphic evidence of a middle holocene dry period in the northern midwest the lake level was lower between about 6500 and 3500 yr b p indicating that runoff from the upper yahara river basin may have ceased during the drier seasons of the year derived estimates of precipitation between 6500 and 3500 yr b p indicate a decrease of about 10 down to about 700 mm from the present precipitation value of 800 mm a warming between 6500 and 3500 yr b p is also interpreted based on a change of vegetation from rich mesophytic forest before 6500 yr b p to quercus savanna with increased charcoal abundances after that time after 3500 yr b p a closed quercus forest and decreased charcoal suggest a cooler and wetter climate the qualitative paleoecological interpretations quantitative precipitation reconstructions based on pollen from the region including the lake mendota data and estimates of hydrologic budget based on lake level changes all show indications of a dry and warm middle holocene evidence from a large regional array of sites also supports these interpretations

charcoal recognition taphonomy and uses in palaeoenvironmental analysis abstract charcoal predominantly the product of wildfires is abundant in many sedimentary rocks deposited in a wide range of environments from terrestrial to marine it also occurs in some volcanic rocks this paper outlines aspects of charcoal formation both natural and experimental and briefly considers the taphonomic processes leading to a final assemblage this is done using examples from recent fires and through experimentation the ways in which charcoal assemblages are recognized in the field and extraction in the laboratory are also considered methods of charcoal identification are presented the range of charcoalified plant organs that can be found is discussed and a wide range of study methods outlined including light microscopy dark field light microscopy reflectance microscopy scanning electron microscopy and synchrotron radiation x ray tomographic microscopy emphasis in this paper is on the study of macro and meso charcoal above180 m finally there is a consideration of the broad use of charcoal from plant evolution studies fire history studies vegetation studies anatomical studies climate and atmospheric studies and the wider importance of charcoal for the earth and biological sciences charcoal is information rich but yet is an under utilized resource

tracing long term tropical montane ecosystem change in the eastern arc mountains of tanzania pollen 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 t o 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 copyright 2014 john wiley sons ltd

10 000 yr record of extreme hydrologic events well dated lacustrine sediments provide a hydrologic record indicating that the frequency and magnitude of runoff events and by inference storms have varied over the past 10 k y in northern new england we used five sediment cores and radiocarbon dating to develop a chronology of holocene hydrologic events for the ritterbush pond basin northern vermont chemical and physical analyses allow us to identify 52 distinct layers of predominately inorganic sediment that represent terrestrially derived material delivered to the pond by runoff events the thickness of some layers suggests hydrologic events at least equal in size to and probably much larger than any storm or flood recorded during nearly 300 yr of written regional history layer thickness and frequency and by analogy storm size and recurrence change through the holocene the largest events occurred 2620 6840 and 9440 calibrated 14c years before present cal 14c yr b p the most frequent hydrologic events occurred in three periods 1750 to 2620 6330 to 6840 and 8600 cal yr b p the recurrence interval of layer deposition during stormy periods averages 130 100 cal yr whereas the recurrence interval during less stormy periods is longer 270 170 cal yr the ritterbush pond event record illustrates the potential of inorganic lacustrine sediment to serve as a proxy record for estimating paleoflood frequency and deciphering climate change

biomass burning and oceanic primary production estimates in the sulu sea area over the last 380 kyr and the east asian monsoon dynamics abstract coccolithophorid assemblages and micro charcoal content were analysed in giant piston core md97 2141 recovered in the sulu sea philippines these proxies help to reconstruct respectively the dynamics of the oceanic primary production pp and biomass burning in that area pp in the sulu sea intensifies during the east asian winter monsoon eawm and therefore pp constitutes a proxy for eawm dynamics most of the precipitation in the sulu sea region occurs during the east asian summer monsoon easm because the intensity of biomass burning is related to dryness of the surrounding area the sedimentary micro charcoal content can be used as an inverse proxy for easm intensity our results show that the eawm intensifies during glacial times in agreement with previous studies precessional forcing appears to act directly on eawn because of the early response of pp in that frequency band the micro charcoal record exhibits complex dynamics which we attribute to the competing influence of the long term el nino southern oscillation enso like forcing and the glacial interglacial cycle on easm these influences create an unusual frequency spectrum with power around 30 kyr and 19 kyr attributed to the non linear response to the 100 kyr cycle glacial and the 23 kyr enso cycle a factor of two increase in the amplitude of the micro charcoal variability between 51 and 10 ka bp could correspond to homo sapiens biomass burning in the style of the fire stick farming of the australian aborigines we also find on precession cycles an opposite phase between easm and eawm records and an advance of 18 o and 18 o respectively by 2000 yr

holocene variations of sea surface conditions in the southeastern barents sea reconstructed from dinoflagellate cyst assemblages palynomorphs were analysed in two sediment cores from the southeastern barents sea representing the past 8 3 and 4 4 kyr high dinocyst contents and species diversity enabled the application of the best analogue method to quantitatively reconstruct sea surface salinities temperatures and ice cover using 677 modern reference sites from the north atlantic and arctic seas including new data from the barents sea reported here at the southern core site where waters are affected by the atlantic inflow sea surface conditions were relatively warm and stable between ca 8000 and 5000 calendar yr bp in contrast the past 5 kyr had periods with cooler temperatures and extended ice cover fluctuating mostly at 1 1 5 kyr frequencies at both sites most pronounced coolings occurred around 8 1 5 3 5 3 2 and 2 5 ka the northern site additionally shows younger cooling events tentatively dated to 1 4 0 3 and 0 1 ka identified variations in sea surface conditions indicate changes in atlantic water inputs to the barents sea our results generally correlate to palaeoclimatic reconstructions from northwestern eurasia exemplified by palynological records from karelia this correlation suggests that sea surface variations in the barents sea reflect large scale changes in atmospheric and oceanic interactions between the north atlantic and the arctic copyright 2001 john wiley sons ltd

pollen inferred climatic fluctuations in ethiopia during the last 3000 years abstract although lake levels fluctuations are known from ethiopia during the late holocene few continuous paleoclimatic records are available from the high plateau a 3000 yr high resolution pollen record from the arsi mountain in arussi province of southeastern ethiopia provides information on recent changes in the vegetation above the upper tree line at 3600 m elevation the organic sediment was deposited into the dega sala swamp ca 3000 yr b p on top of a coarse gravel reepresenting a solifuxion deposit linked to neoglacial the surrounding vegetation was established as that of the ericaceous belt with ericaceae shrub dominant the pollen diagram registers significant changes in the relative frequencies of the local herbaceous pollen component versus the arboreal taxa from the upper forest limit allowing the high altitude of the site such changes indicate downward movements of the vegetation belts that are due mainly to temperature variations an estimated cooling of 2 c is registered at 560 120 yr b p ams date contemporaneous with the little ice age the successive upward regrowth of the forest is rather indicative of a recent warming than linked to recolonization of the forest following anthropogenic deforestation unlikely at altitude above potential cultivation

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

glacialanterglacial record from intertropical africa high resolution pollen and carbon data at rusaka burundi abstract in northern intertropical africa many geological data have documented several abrupt climatic fluctuations taking place during the time of the last deglaciation one of them is an aridity event generally placed in the interval 11 000 10 000 bp and synchronous with the younger dryas cold episode of the temperate regions that has been explained by the influence of the atlantic ocean circulation on global climate in this paper we present high resolution 50 to 150 years studies of organic matter and pollen undertaken on a new core from the rusaka peat bog 3 26 south 29 37 east 2070 m altitude dated by the conventional l2 dates and the ams methods 18 dates obtained on bulk sediment and macroremains although the sediment at the bottom of the core was deposited during the last glacial period prior to 21 000 bp the dating provides a reliable chronology for the last 12 000 bp only several vegetational changes are documented in the interval 12 000 9000 bp but their chronological placement can only be achieved with a few years of uncertainties a great dispersion of ams dates is attributed to contamination by charcoal dated between 11 700 and 11 500 bp and to a possible age plateau at ca 10 000 bp therefore the results are preferably presented versus depth to keep synchronism in the stratigraphic placement of the successive events at rusaka increase in carbon storage c n ratio for terrestrial plants and tree cover began at ca 12 000 bp soon after the swamp had been established this date is in good agreement with a major increased hydrological balance well documented throughout the intertropical region the forest installation is progressive rather complex and seen as a two step process the first forest phase 11 700 bp to 10 600 bp is dominated by hagenia a montane taxon in good correspondance with previous records from other authors in east african mountains the second forest regeneration took place post 10 000 bp after a clearly reversed trend of tree cover from 10 600 to 10 000 bp ending with a short episode of minimum trees lasting no more than about 200 years but there is no indication of cooling whatsoever and the opening of the forest is better explained by increased aridity rather than normal pattern of forest succession this will remain a controversal interpretation among palynologists until high resolution pollen data can be obtained for the 13 000 bp and earlier period nevertheless the timing of the arid episode at rusaka is in good agreement with other evidence mentioned from highland and lowland pollen data a detailed comparison with 25 available pollen diagrams is limited by poor or inconsistent dating or low resolution of the pollen data nevertheless pollen from four of them document an arid event in good agreement with its timing at rusaka and high resolution isotopic results from two sites in equatorial lowlands and from the sahel this work shows that the arid younger dryas occurred at the same time both in lowlands and highlands and therefore was most likely a precipitation signal rather than a response to temperature decrease

the reconstruction of boreal forest fire history from lake sediments a comparison of charcoal pollen sedimentological and geochemical indices abstract fossil charcoal fossil pollen sedimentological and geochemical analyses of lake sediments have been used previously to reconstruct a history of local fires and resulting vegetation change the rationale behind these approaches is described and the usefulness of each technique for reconstructing fire history in the boreal forest is assessed empirically historical and dendrochronological records provide regional and local fire histories for a site in wood buffalo national park alberta canada the local and regional history of fires is compared with the microscopic charcoal content macroscopic charcoal content elemental carbon content fossil pollen content sedimentology and geochemistry of annually laminated sediments from a small lake there is no significant correlation between the abundance of microscopic charcoal macroscopic charcoal and total elemental carbon content of the sediments automated measures of microscopic charcoal abundance made with an image analysis system are correlated significantly with optical counts of microscopic charcoal none of the charcoal measures provide unequivocal records of local fire activity and the abundance of microscopic charcoal appears to be influenced by variations in regional fire activity however the highest depositional rate of macrofossil charcoal occurred during the time of a fire that burned within the drainage basin variations in sedimentological measures and geochemistry do not correlate with local fire activity fossil pollen percentages and accumulation rates display a pattern of variation that is consistent with observed vegetation responses to fire in the boreal forest what is likely apparent in the pollen record are the results of a series of burns of sufficient extent and intensity to kill most of the above ground biomass of the vegetation in an area at least as great as the drainage basin the inability of evidence from lake sediments to provide detailed histories of past fire activity is not surprising given the wide range of variation in the spatial extent proximity intensity and impact of individual fires

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

environmental change in montane southwest uganda a pollen record for the holocene from ahakagyezi swamp the environmental history of montane southwest uganda over the last c 12 300 years is described using data from a 22 84 m long core of sediment from ahakagyezi swamp rukiga highlands these data include plant microfossils and macrofossils charcoal and nine radiocarbon dates according to evidence from plant fossils and radiocarbon dates vegetation in the ahakagyezi catchment was very different to the expected climax today until c 10500 bp the surface of the swamp was dominated by sedges whilst the adjacent hillsides were largely devoid of trees changes in pollen suggest that a form of dry montane scrub was replaced by moist lower montane forest from c 11000bp subsequent fluctuations in pollen indicate that once established the composition of moist lower montane forest varied during the holocene and that unreversed forest reduction commenced in the ahakagyezi catchment at c 800 bp on the surface of the swamp itself syzygium dominated swamp forest increased in extent from c 5800 bp and mor

late quaternary peat formation and vegetation dynamics in a lowland tropical swamp nee soon singapore abstract cores of sediment from nee soon a peat forming freshwater swamp located in the perimarine zone of singapore have yielded a record of vegetation history that comprises parts of the last glacial and holocene periods the evidence includes two conventional and four ams radiocarbon dates the oldest of which is 23 050 330 b p uncalibrated radiocarbon years and variations in the abundances of sub fossil pollen and spores and charcoal the results of a study of the relationship between contemporary vegetation and modern pollen accumulation facilitated interpretation of sub fossil tree pollen data peat formation occurred at nee soon during the last glacial when sea levels on the sunda continental shelf were well below those at present the occurrence of montane pollen types notably podocarpaceae in sediment samples dated to the late glacial and early holocene suggests either temperatures substantially lower than those of the present and possibly humid conditions or cold seasonally dry climates and reduced levels of atmospheric co 2 the abundance of charcoal indicates the widespread occurrence of fires throughout the entire period represented by the cores for the mid holocene the evidence indicates an increased saline influence presumably as a result of relatively high sea levels falling sea levels during the late holocene appear to have preceded the onset of the most recent period of peat formation at nee soon the evidence confirms that long last glacial interglacial records of lowland vegetation history are available from terrestrial locations in the humid core of southeast asia and suggests that the complexity of perimarine swamp dynamics is not captured fully by anderson s model which assumes a close relationship between peat formation and sea level

a 12 000 year history of vegetation and climate for cape cod massachusetts abstract pollen and charcoal analysis of radiocarbon dated sediment cores from duck pond in the cape cod national seashore provide a continuous 12 000 yr vegetation and climate history of outer cape cod a picea hudsonia parkland and then a picea pinus banksiana alnus crispa boreal forest association grew near the site between 12 000 and 10 000 yr b p this vegetation was replaced by a northern conifer forest of pinus strobus p banksiana and subsequently by a more mesophytic forest pinus strobus tsuga quercus fagus acer ulmus fraxinus ostrya as the climate became warmer and wetter by 9500 yr b p by 9000 yr b p a pinus rigida quercus association dominated the landscape high charcoal frequencies from this and subsequent levels suggest that the pine barrens association developed during a warmer and drier climate that lasted from 9000 to about 5000 yr b p increased percentages of pinus strobus pollen indicate a return to moister and cooler conditions by about 3500 yr b p a doubled sedimentation rate increased charcoal and increased herb pollen suggest land disturbance near the pond before european settlement these results suggest a rapid warming in the northeast in the early holocene and support a hypothesis of a rapid sea level rise at that time comparison of the pollen results from duck pond with those from rogers lake connecticut illustrates the importance of edaphic factors in determining the disturbance frequency and vegetation history of an area

postglacial evolution of a fine grained alluvial fan in the northern great plains canada abstract this paper reports on the first subsurface core taken from an alluvial fan in the interior plains of western canada sedimentary structures grain size grain roundness loss on ignition charcoal abundance bulk authigenic geochemistry colour mineralogy and microscopic charcoal identifications show that a fine grained fan developed through a succession of depositional environments within each environment sediment erosion transportation and deposition processes were conditioned by changing dominant partial area contributions and complex geomorphic responses neither the rate nor the processes of aggradation have been constant through time succession from one depositional environment to another involved the crossing of geomorphic thresholds while climate may have affected sediment yield and therefore the timing of threshold crossings the basic sequence was controlled by aggradation alone the sensitivity of this site to climate change is thus overwhelmed by internal processes

determination of black carbon by chemical oxidation and thermal treatment in recent marine and lake sediments and cretaceous tertiary clays abstract several sample treatments and analytical methods for the measurement of black carbon in a wide variety of sediments were considered in which the removal of organic carbon is a critical step in the procedure a comparison between chemical oxidation and thermal treatment was conducted and the latter was shown to be inappropriate due to the polymerisation of organic matter using acid dichromate oxidation reactive kerogen was separated from black carbon in a variety of lake and marine and recent and ancient sediments with relatively small and quantifiable losses 1 6 of black carbon under carefully controlled reaction conditions

late holocene vegetation and fire history at the southern boreal forest margin in alberta canada abstract a transect of three shallow ponds across the aspen parkland boreal forest transition in elk island national park alberta canada shows changes in late holocene vegetation and disturbance dynamics and consequent carbon storage in response to climate change and to recent anthropogenesis pollen and charcoal analyses reveal unexpected changes in fire regime although there is the expected decline in fire activity during the historic period presumed due to agricultural clearance around the park there is also a prehistoric fluctuation in fire regime at one of the sites pollen evidence suggests that the fluctuations in fire regime may be due to changes in hydrology declining groundwater levels during the medieval warm period allowed the replacement of substantial areas of shrub birch betula glandulosa with the less fire prone aspen populus tremuloides causing a decline in fire frequency and or severity while increasing carbon storage on the landscape this is counter to the intuitive increase in fire activity with warmer and drier climate canadian national parks are currently managed under a natural processes and conditions paradigm the changes in conditions and consequent changes in processes evident due to the relatively minor climatic fluctuations of the little ice age and medieval warm period shown here suggest a need to revisit this paradigm in consideration of future anthropogenic climate change

particle motion and the theory of charcoal analysis source area transport deposition and sampling principles from particle motion physics were applied to recurring problems of the interpretation of stratigraphic charcoal data 1 fires within catchments of lakes often produce no record in fossil charcoal curves and 2 periods characterized by no local fire e g 20th century fire suppression often display as much charcoal as times when local fire was frequent quantitative theory on source area transport deposition and sampling of charcoal shows the relationship between particle sizes counted by alternative methods of charcoal analysis pollen slides for particles 5 80 m in diameter petrographic thin sections for particles 50 10 000 m diameter and charcoal diagrams the relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods charcoal recorded on pollen slides is of a size that is difficult to lift but once entrained it remains in suspension thin section charcoal is lifted at relatively low wind velocities but it is not suspended at normal surface wind speeds thermal buoyancy during fire lofts charcoal above the forest canopy depending on particle size and wind speed pollen slide charcoal sizes are underrepresented near the fire because they remain in suspension and are preferentially exported from the burn area thin section charcoal is convected to lower heights on average and is deposited nearby following fire thin section charcoal is redistributed locally by wind and thus may enter lakes because of cohesive forces and aerodynamics more pollen slide charcoal remains on the ground and less enters lakes source areas for pollen slide charcoal are subcontinental to global and diagrams of pollen slide charcoal are biased toward nonlocal charcoal they can be used to interpret importance of fire for broad spatial and temporal scales thin section charcoal represents the catchment fire regime simulation models that generate charcoal during fire mix sediments and then sample at specified intervals indicate that 1 in the absence of sediment mixing the pollen slide method should consistently resolve individual fires that occur with an expectation of 30 50 yr 2 unless samples are continuous neither method will produce useful estimates of fire frequency and 3 even a modest amount of sediment mixing will obscure the signal

black carbon records in chinese loess plateau over the last two glacial cycles and implications for paleofires abstract to study the temporal and spatial changes in paleofires over the chinese loess plateau black carbon concentrations were analyzed on the loess paleosol samples from three sections along a north south transect using the orbitally tuned time scales of the sections the black carbon mass sedimentation rates bcmsr were calculated results show that in the last two glacial cycles the bcmsr values in glacial periods are 2 3 times higher than in interglacial periods and the bcmsr variability has a relatively strong precession associated 23 ky period suggesting that the glacial cold dry climate conditions were apt to induce natural fires over the loess plateau comparison of the bcmsr records among the three loess sections demonstrates that natural fire occurrence was much more intensive and frequent in the northern loess plateau than in the southern part coinciding with the previous conclusion that the northern plateau has experienced a drier climate regime in both glacial and interglacial periods the substantial increase in bcmsr of the upper s0 relative to the lower s0 at lingtai and weinan indicates that human activities have exerted a significant influence on fire regimes in the middle and southern loess plateau during late holocene due to the relatively intensive agricultural usage of land