late holocene environments at lake mitsinjo northwestern madagascar two sediment cores from lake mitsinjo in northwestern madagascar were analysed for evidence of past environmental changes the unconformities in a 503 cm core from the centre of the lake and a 306 cm core from the shore were correlated to identify a hiatus in sedimentation that occurred just before ca 1000 bp the 3500 year stratigraphic record was analysed for fossil pollen charcoal algae organic matter and carbonate content pollen stratigraphy indicates the following vegetational changes 1 a mosaic of dry forest and grassland from ca 3500 bp until the time the lake dried up 2 a savanna from ca 1000 500 bp and 3 a highly disturbed grassland with fire adapted trees and ruderal herbs in the last 500 years pollen spectra and lithologic correlation indicate that prior to the hiatus the lake experienced a highstand and after the hiatus lake levels were lower the lake level changes probably reflect the local effective moisture pollen evidence indicates a possible human disturbance of the s

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

climate and human influence on late holocene fire regimes in the british virgin islands global climate change poses significant threats to the caribbean islands yet little is known about the long term disturbance regimes in island ecosystems this research investigates 2000 yr of natural and anthropogenic fire disturbance through the analysis of a latitudinal transect of sediment records from coastal salt ponds in the british virgin islands bvi the two research objectives in this study are 1 to determine the fire regime history for the bvi over the last 2000 yr and 2 to explore ecological impacts from anthropogenic landscape modification pre and post european settlement the magnitude of anthropogenic landscape modification including the introduction of agriculture was investigated through a multiproxy approach using sedimentary records of fossil pollen and charcoal our results suggest fire regimes from belmont pond thatch island and skeleton pond have been influenced by human activity particularly during the postsettlement era from 500 cal yr bp to modern our results suggest that fire regimes during the medieval climate anomaly were responding to changes in climate via dominant atmospheric drivers the presettlement fire regimes from these islands suggest that fires occurred every 90 to 120 yr this research represents a significant data contribution to a region with little disturbance and vegetation data available

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

sensitivity of carbon isotopic proxies to paleoclimatic forcing a case study from lake bosumtwi ghana over the last 32 000 years 1 analyses of carbon isotopic ratios in concomitant bulk sediment samples and fossil grass epidermal fragments from lake bosumtwi ghana demonstrate that both records reflect paleohydrologic variability however the bulk sediment signal is dominated by within lake processes whereas the fossil grass epidermal record provides the terrestrial vegetation response to changes in available moisture the direction of change is similar but the magnitude and timing of response are different during the terminal pleistocene the aquatic record shows a dramatic flip flop behavior bulk sediment 13c 4 to 32 while the terrestrial grass epidermis record is much more muted 13c shifts from 11 to 15 furthermore during the transition to the relatively moister conditions of the holocene a dominance of c4 plants persisted for at least 800 1000 years after limnological changes began on the other hand the epidermal isotopic record shows a much more dramatic response than that provided by the bulk sediment to the onset of drier more seasonally contrasted conditions during the late holocene these results emphasize the need to consider varying response times of the biogeochemical systems that control the production of proxies especially when attempting to correlate widely separated records based upon fundamentally different proxies

systematic analysis of deep seismicity 200 centroid moment tensor solutions for earthquakes between 1977 and 1980 summary a systematic study of deep seismicity is performed using waveform data from the gdsn between 1977 and 1980 and the centroid moment tensor method of dziewonski et al two hundred new cmt solutions are found for events deeper than 100km their moments obtained using the same algorithm range between 7 x and 1 4 x lo2 dyne cm a factor of 20 000 a statistical analysis of the cmt parameters provides important conclusions among these the shift in origin time for deep events is found to be almost independent of the seismic moment providing an indication of the complexity of deep earthquakes the deviation from the double couple model appears to be correlated to the state of stress of the subducting slabs mechanisms showing down dip compression are generally dominated by the eigenvalue corresponding to the compression axis and down dip tension correlates with the predominance of the tensional eigenvalue comparison with moment tensors obtained by other authors using different waveform data shows good agreement between different methods comparison with published focal plane mechanisms confirms the precision and reliability of the cmt method examples of cmt solutions used to identify patterns of seismicity associated with deep fault planes are shown

late holocene environmental changes in arid southwestern madagascar a 5000 yr stratigraphic record containing fossil pollen charcoal and bones of the extinct quaternary megafauna from andolonomby a hypersaline pond in arid southwestern madagascar shows evidence for climatic desiccation beginning about 3000 yr b p pollen spectra shift at this time from primarily arboreal taxa characteristic of forests and woodlands of more mesic western madagascar to wooded savanna typical of somewhat drier localities between 3000 and 2000 yr b p the site became increasingly arid charcoal and pollen evidence indicates that increased fire and disturbance occurred at the site beginning ca 1900 yr b p probably signaling the beginning of human settlement in the area the fossil record suggests that various human and natural factors on the island may have interacted in the subsequent millennium to culminate in the extinction of the entire endemic megafauna

changes in graminoid stomatal morphology over the last glacial interglacial transition evidence from mount kenya east africa abstract stomatal size and density were measured from graminoid cuticular fragments extracted from dated sediments in two tropical montane crater lakes on mount kenya the sediments had been dated in other studies and spanned 1500 37 000 calibrated years bp changes in the mean size and density of the graminoid stomata were found using a coarse signal analysis the two lakes gave fairly similar results although there was some divergence at the start and end of the time period analyzed there is some correspondence between the atmospheric co 2 concentration and graminoid stomatal density during the transition from the lgm to the start of the holocene where stomatal density decreased while co 2 concentrations increased all the changes observed may have been plastic responses within existing species at the site or competitive replacements of grass floras we argue that higher stomatal density may have been a response to falling co 2 levels during the last glaciation accompanying the replacement of a c 3 flora by c 4 species the stomatal size changes exhibited over this time period may have adapted plants to changes in soil water availability that stomatal morphology changes in a sample flora not a single taxon over millennia is a novel finding and one that may have implications for paleoecological interpretation and the prediction of grass behavior in the future

holocene charcoal stratigraphy from laguna tortuguero puerto rico and the timing of human arrival on the island an 8 m sediment core from laguna tortuguero puerto rico provides a 7000 calendar year history of fire occurrence and sedimentation on the island s north coast after c 5300 cal bp microscopic charcoal particle concentration and influx increase abruptly and values remain high for the next two millennia subsequent to c 3200 cal bp fire occurrence gradually declines to more moderate levels it seems likely that the mid holocene acceleration in fire frequency documented here may signal the onset of human disturbance of the landscape indirect detection of human arrival on oceanic islands from a sudden increase in stratigraphic charcoal may be a useful technique in other island contexts although it is important to consider that wildfires can occur without a human ignition source

glacial interglacial variations in carbon cycling revealed by molecular and isotope stratigraphy of lake nkunga mt kenya east africa abstract the lipid content n alkanes n alkanols n alkanoic acids and the 13c values of these lipids were measured in nineteen sediment samples taken from a 21 18 m long core from lake nkunga a high altitude 1820 m a s l freshwater lake situated in the montane rain forest on mt kenya the record spans the early last glacial marine isotope stages 5a to 4 and the late holocene 1030 45 14c yr bp to the present day the intervening hiatus spans the last glacial maximum and the early to mid holocene the molecular biogeochemical results are interpreted in terms of past changes in climate vegetation and atmospheric co2 concentration three different sources of organic matter input were identified from the n alkyl lipids namely terrestrial plants aquatic plants and algae unusual distribution patterns of dominant mid chain length n alkanes c23 25 n alkanols c22 24 and n alkanoic acids c22 24 are attributed to aquatic macrophytes an 11 decrease in bulk carbon isotope values between the sediments of early glacial 17 and late holocene age 28 is also apparent in the individual homologues of the n alkyl lipids the observed isotopic shift in terrestrial higher plant biomarkers is similar to that observed in nearby sacred lake and is consistent with an expansion of c4 grasses or sedges during the early glacial the corresponding vegetation was a dry montane juniper olive forest with a grassy understorey representing cold dry conditions with lower co2

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

on the thermal regime of some tectonic units in a continental collision environment in romania an analysis of the evolution of the main tectonic units in romania shows that the thermal regime of the lithosphere should be derived according on the one hand to the particular tectonic interactions the various tectonic units have been involved in and on the other hand to the investigated depth interval a steady state conduction model of the crustal temperature field based on the heat flow distribution and information on the structure is presented for the romanian territory it shows large lateral thermal variations between tectonic units as a result of different geological and thermal histories within the frame of a complex modelling of the thermal evolution of the lithosphere in the east carpathians as proposed in this study the zero order thermal effects of the pre miocene oceanic subduction of the eurasian plate are evaluated the deep thermal structure of the subducted slab is derived and shown to be compatible with the velocity structure of the lithosphere and the intermediate depth seismicity of the vrancea area

interhemispheric synchrony of the last deglaciation inferred from alkenone palaeothermometry the relative timings of the last deglacial warming in the southern and northern hemispheres are not well constrained but are a crucial component in understanding the mechanisms of deglaciation1 a clearer picture of the degree of interhemispheric synchrony has been obscured by a dearth of high resolution temperature records that can be tied to the absolute calendar timescale moreover the quantification of tropical temperatures during the last glacial cycle is controversial2 8 here we apply the alkenone method of sea surface temperature reconstruction9 10 to several high resolution sediment cores recovered from the tropical indian ocean between 20 n and 20 s the inferred initial sea surface temperature warming 15 000 calendar years ago at 20 s is in phase with northern hemisphere sea this study and air11 temperature changes but lags antarctic warming12 14 by several millennia this finding along with the results of recent modelling studies15 16 provides strong support for the idea that changes in the ocean s global thermohaline circulation were not the only cause of interhemispheric climate teleconnection during the last deglaciation

variations in fire frequency and climate over the past 17 000 yr in central yellowstone national park a 17000 yr fire history from yellowstone national park demonstrates a strong link between changes in climate and variations in fire frequency on millennial time scales the fire history reconstruction is based on a detailed charcoal stratigraphy from cygnet lake in the rhyolite plateau region macroscopic charcoal particles were tallied from contiguous 1 cm samples of a 6 69 m long core and the data were converted to charcoal accumulation rates at evenly spaced time intervals intervals of high charcoal accumulation rates were interpreted as local fire events on the basis of information obtained from modern charcoal calibration studies in the yellowstone region the record indicates that fire frequency was moderate 4 fires 1000 yr during the late glacial period reached highest values in the early holocene 10 fires 1000 yr and decreased after 7000 calendar yr b p the present fire regime 2 3 fires 1000 yr was established in the past 2000 yr the charcoal stratigraphy correlates well with variations in july insolation through time which suggests that regional climate changes are responsible for the long term variations in fire frequency in the early holocene summer insolation was near its maximum which resulted in warmer effectively drier conditions throughout the northwestern united states at this time the fire frequency near cygnet lake was at its highest after 7000 calendar yr b p summer insolation decreased to present values the regional climate became cooler and wetter and fires were less frequent the cygnet lake record suggests that long term fire frequencies have varied continuously with climate change even when the vegetation has remained constant

paleofire severity and vegetation change in the cascade range oregon usa paleoecological research has expanded our knowledge of the relationships between climate fire and vegetation fire can be a significant driver of forest composition and structure change but identifying and quantifying fire regimes has been elusive using high resolution charcoal analysis and pollen analysis we reconstructed a 13 200 year old fire and vegetation history from breitenbush lake oregon located in the central cascade range usa our objective was to examine if fire occurrence and severity may have been a driver of holocene forest composition change the data from this study suggests that while fire can create opportunities for successional process to occur fire events were not significant catalysts for forest change instead most major transitions at breitenbush lake occurred during prolonged fire free intervals our results reinforce the view that climate is the major control of vegetation composition change in the cascade range

cloud dynamic contribution to high elevation peatland growth during the holocene escalerani central andes bolivia changes in climate conditions during the holocene are documented in different parts of south america showing contrasting responses to global changes this study was conducted in the wet puna at an

reconstruction of a subalpine grass dominated ecosystem lake rutundu mount kenya a novel multi proxy approach palaeoecological reconstructions based on a single proxy are limited but by combining pollen biogeochemistry and grass cuticle analysis ecosystem structure and function can be better understood lake rutundu is a small subalpine lake on the northeast flank of mt kenya during the last glacial pollen evidence suggests a shrub grassland dominated by afroalpine taxa and poaceae representing a dry cold open environment the 13c values of terrestrial biomarkers imply a high proportion of c4 plants grass cuticle analysis allows resolution of the different c4 subtypes and shows that the vegetation was dominated by tall c4 panicoid grasses prone to frequent fires during the holocene poaceae pollen declined while subalpine shrubs increased the 13c values of terrestrial biomarkers imply a c3 dominated vegetation together with an expansion of rainforest at lower altitudes this suggests wetter conditions more favourable to c3 plants increased percentages of c3 pooid grass cuticles confirm a reduction in moisture stress

holocene hydroclimate and environmental change inferred from a high resolution multi proxy record from lago ditkebi chirripo national park costa rica abstract multi proxy analysis of a sediment core recovered from lago ditkebi in chirripo national park costa rica was undertaken to develop a multi decadal to sub centennial scale reconstruction of holocene hydroclimate and environmental change for the region analyses of sub fossil chironomid assemblages macroscopic charcoal and bulk sediment geochemistry suggest that the glacial highlands in chirripo national park experienced notable hydroclimate variability periodical burning by wildfires and climate related vegetation change during the last 8100 years a single chironomid taxon procladius most commonly associated with cold glacial lakes in costa rica dominates the holocene sub fossil chironomid assemblage in lago ditkebi inferred from the proxy records the interval between 8100 and 5270 cal yr bp at the glacial highlands was relatively cold and dry with low effective moisture and limited fire activity cool and dry conditions were also observed between 2820 cal yr bp and present but co occurred with more frequent low severity fires the highest fire frequency occurred between 3300 and 1600 cal yr bp the shifts in the chironomid assemblage and the low 13c values detected between 5270 and 2820 cal yr bp suggest a warm and wet climate and a decrease in abundance of muhlenbergia a c4 grass during that time concurrent maxima in c n charcoal accumulation and the abundance of thermophilous chironomid taxon polypedilum n type at 5200 cal yr bp are indicative of an abrupt climate change event that was characterized by rapid warming quickly increased effective moisture and intense wildfires in the glacial highlands of costa rica

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

holocene vegetation history and quantitative climate reconstructions in a high elevation oceanic district of the italian alps evidence for a middle to late holocene precipitation increase abstract we reconstructed the vegetation and climate history during the last 10 ka in a high elevation sedimentary record armentarga peat bog 2345 m asl on the southern flank of the european alps through the study of paleoecological and sedimentary proxies we included a specific elevational transect of modern pollen accumulation rates for timberline forming trees and shrubs alnus viridis pinus sylvestris mugo pinus cembra quantitative reconstructions of july temperature and annual precipitation were obtained by applying numerical transfer functions built on an extensive pollen climate calibration set from the european alps changes in elevational vegetation arrangement were primarily driven by phases of precipitation increase and to a lesser extent by millennial scale temperature changes already known from glacier timberline chironomids and speleothem records at alpine scale changes in pollen inferred annual precipitation occurred in three main steps an early holocene moderately humid phase is mirrored by the early spread of alnus viridis dwarf forests precipitation started to increase at 6 2 ka cal bp a further prominent step forward at the middle to late holocene transition led to the high values of snowfall and runoff characterizing today s oceanic elevational climates of the outer italian alps this change led to timberline depression and grassland expansion locally human impact was weak at the late neolithic bronze age transition this event correlates with lake level oscillations in the northern mediterranean borderlands suggesting intensification of southern air masses conveyed by tyrrhenian cyclones towards windward districts

mineral magnetic proxies of erosion oxidation cycles in tropical maar lake sediments lake tritrivakely madagascar paleoenvironmental implications abstract mineral magnetic measurements were performed on the upper 16 m of five piston cored sedimentary sequences from lake tritrivakely madagascar ams 14 c dating and correlation of the five magnetic susceptibility records allowed establishment of a composite sedimentary record of the last 46 kyr our data suggest that mineral magnetic changes result from changes in concentration of strongly ferrimagnetic terrigenous minerals and from preservation dissolution cycles of detrital iron oxides primarily high coercivity fe iii phases such as hematite in alternately oxic and anoxic depositional environments high coercivity iron oxide phases are restricted to stratigraphic intervals that are interpreted to represent dry periods with oxic conditions comparison with other paleoenvironmental proxies pollen total organic carbon lithology suggests that the sediments record relatively humid conditions before 22 kyr bp and relatively dry conditions during the last glacial maximum lgm and the early holocene such results contrast with the previous observations of relatively dry glacial conditions and humid mid holocene conditions in the summer rainfall area of east and se africa

active deformation in the vrancea region rumania recent and historical seismicity as well as reliable fault plane solutions are used to study the active deformation caused by the occurrence of intermediate depth 60 170 km earthquakes of the vrancea region rumania in this area located in the southeastern part of the carpathian arc the westward subduction of the carpathian trench has terminated leaving continental lithosphere at present at the arc the principalt axis of the intermediate depth events trends n159 e and has a plunge of 74 which is the same as the dip of the subducted plate thep axis has a trend of 314 and a shallow plunge of 15 the analysis of the moment tensor of six focal mechanisms showed that the dominant mode of deformation of the subducted lithosphere is a down dip extension at a rate of about 2 cm yr based on seismicity data

interpretation of charcoal morphotypes in sediments from ferry lake wisconsin usa do different plant fuel sources produce distinctive charcoal morphotypes we describe five common charcoal morphotypes observed in late holocene lake sediments from northern wisconsin and compare them with charcoal produced by burning modern plant material our experiments show that grass cuticle conifer wood and leaves of some broadleaved taxa all produce recognizable charcoal types that are preserved in sediments we use the identification of charcoal morphotypes to enhance our interpretation of a previously published charcoal record from ferry lake wisconsin the occurrence of the different charcoal morphotypes changed as the vegetation and fire regimes changed over the past 2300 yr charred grass cuticle was more common before 1300 cal yr bp when small charcoal peaks were frequent and the pollen assemblage suggests that an open oak savanna surrounded the lake charcoal with bordered pits produced from burned conifer wood was more common after 1300 cal yr bp when red jack pine pollen increased and the frequency of charcoal peaks decreased suggesting a switch from a sur

environmental variability within the chinese desert loess transition zone over the last 20000 years the desert loess transition zone in northern china is sensitive to climate variability which is con trolled mainly by the relative strengths of the east asian summer and winter monsoons sandy loess layers found in the loess plateau and palaeosol sequences found in the sandy desert demonstrate latitudinal shifts of the southern desert margin over the last 20000 years stratigraphic investigations together with radiocarbon and some thermoluminescence dating show that during the last glacial maximum the desert margin was at its most southerly position 38 n during the early holocene it moved northward about three degrees in latitude 41 n at present the desert margin is again close to its most southerly position 38 219 n yet the northern boundary position of modern summer monsoon activity is placed at 41 459 n which is close to the estimated holocene optimum desert margin 41 n this situation cannot be explained from natural climate models hence an external driving mechanism needs to be considered and the most obvious one is that caused by human activity on the natural environment over the last 3000 years historical evidence tends to reinforce this consideration

an 11 000 year long record of fire and vegetation history at beaver lake oregon central willamette valley high resolution macroscopic charcoal and pollen analysis were used to reconstruct an 11 000 year long record of fire and vegetation history from beaver lake oregon the first complete holocene paleoecological record from the floor of the willamette valley in the early holocene ca 11 000e7500 calendar years before present cal yr bp warmer drier summers than at present led to the establishment of xeric woodland of quercus corylus and pseudotsuga near the site disturbances i e floods fires were common at this time and as a result alnus rubra grew nearby high fire frequency occurred in the early holocene from ca 11 200e9300 cal yr bp riparian forest and wet prairie developed in the middle holocene ca 7500 cal yr bp likely the result of a decrease in the frequency of flooding and a shift to effectively cooler wetter conditions than before the vegetation at beaver lake remained generally unchanged into the late holocene from 4000 cal yr bp to present with the exception of land clearance associated with euro american settlement of the valley ca 160 cal yr bp middle to late holocene increases in fire frequency coupled with abrupt shifts in fire episode magnitude and charcoal composition likely indicate the influence anthropogenic burning near the site the paleoecological record from beaver lake and in particular the general increase in fire frequency over the last 8500 years differs significantly from other low elevation sites in the pacific northwest which suggests that local controls e g shifts in vegetation structure intensification of human land use rather than regional climatic controls more strongly influenced its environmental history

the initiation and growth of gullies in madagascar are humans to blame abstract lavaka madagascar s unusual gullies require thick lateritic regolith on smoothly convex hills and they are initiated locally by a variety of cultural and natural proximate causes such as paths roads defensive trenches around hillforts steep fields unchanneled to slightly concentrated storm run off springs mass movements etc growth continues by rain attack incision by run off earthfalls caused by wetting and drying cycles and especially basal sapping by diffuse groundwater flow above bedrock somewhat in that order lavaka are less directly permitted and promoted by 1 hardening of exposed laterite surfaces which creates a hard soft hard profile from bedrock to laterite which favors incision relative to lateral erosion 2 the superimposition of concave run off profiles onto convex hills and locally 3 re equilibration of watersheds after stream piracy and faulting run off and hardening are interrelated with devegetation because hardening results from exposure following devegetation because both hardening and devegetation increase run off relative to infiltration and because hardening rain attack and run off impede vegetation devegetation is certainly worsened by harmful human activities such as range burning forest cutting and or overgrazing but tectonism and natural climatic aridification are probably ultimately more important given that many lavaka are simply a natural part of the landscape s evolution and that some lavaka clearly predate primary uncut rain forest

a 40 000 yr pollen and diatom record from lake tritrivakely madagascar in the southern tropics abstract links between southern and northern hemisphere climates during the late quaternary are poorly known partly due to the scarcity of continuous climatic records in the southern tropics pollen and diatom evidence from lake tritrivakely 19 47 s provides information on vegetational and hydrological changes in the central highlands of madagascar over the past 40 000 yr most of the record reflects natural environmental variability since humans arrived on the island ca 2000 yr b p during glacial times the migration of mountain plants toward lower altitudes is consistent with a temperature decrease and with reduced atmospheric co2levels in the lake a positive mean annual hydrologic balance from 38 000 to 36 000 and from 17 500 to 9800 cal yr b p coincided with periods of decreasing summer insolation and preceded by several millennia lake rises in the northern tropics a negative hydrologic budget during periods of maximum seasonal contrast in solar radiation is partly attributed to high summer evaporation rate the last glacial maximum was cool and dry the deglacial warming occurred in two steps the first step accompanied by an increase in wetness occurred abruptly at ca 17 000 cal yr b p about two millennia earlier than in the northern hemisphere it is abundantly documented in southern terrestrial data the second step at 15 000 cal yr b p was in phase with the first major temperature change in the northern hemisphere

late holocene vegetational change in central madagascar abstract a sediment core from lake kavitaha central madagascar provides a stratigraphic record of changes in pollen spectra and charcoal influx in the late holocene the earliest pollen spectra distantly resemble the modern pollen rain of a vegetational mosaic in northern madagascar although results of principal component analysis suggest no close modern analog at about 1300 yr b p a marked rise in charcoal is followed by a decline in pollen of woody taxa culminating in a change to grass dominated pollen spectra within about 4 centuries pollen of woody taxa decline below 15 of total terrestrial pollen and spores beginning about 600 yr b p the influx of charcoal from graminoid sources remains high until recent centuries the late holocene changes in vegetation and fire ecology at the site were approximately contemporaneous with the latest 14 c dates for the extinct megafauna and the earliest dates for human occupation

a study on the active crustal deformation of the north and east anatolian fault zones abstract active crustal deformation in the north anatolian fault zone nafz and the east anatolian fault zone eafz based on seismicity data is examined the results show that the deformation in the nafz is taken up by extension on an azimuth of 59 at a rate of 27 mm yr and as compression on an azimuth of 149 and a rate of 20 mm yr the average dextral lateral motion on the naf is about 23 mm yr this motion in the western part of the naf is 16 mm yr while it increases in the eastern part of the fault to 27 mm yr in the eafz the deformation is taken up as nearly n s compression n7 e at a rate of 5 mm yr and as nearly e w extension n97 at a rate of about 9 mm yr the average sinistral lateral motion has a rate of about 6 mm yr the expected slip rates from plate motions along the north anatolian fault are of the order of 38 mm yr the predicted slip rates for east anatolian fault are 19 mm yr or 29 mm yr the seismicity of the last 140 years can account for the expected deformation along the nafz for the eafz however it is possible that part of the total deformation has been expressed aseismically

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

rates of crustal deformation in the north aegean trough north anatolian fault deduced from seismicity the rates and configuration of seismic deformation in the north aegean trough north anatolian fault are determined from the moment tensor mechanisms of the earthquakes that occurred within this region the analysis is based onkostrov s 1974 formulation the fault plane solutions of the earthquakes of the period 1913 1983 withms 6 0 are used the focal mechanism of some of the past events before 1960 is assumed based on the present knowledge of the seismotectonics as well as on the macroseismic records of the area studied the analysis showed that the deformation of the northern aegean is dominated by ew contraction at a rate of about 15 mm yr which is relieved by ns extension at a rate of about 9 mm yr it was also shown that the northern part of north anatolia north of 39 7 n parallel undergoes contraction in the ew direction at a rate of about 9 mm yr and ns extension as the dominant mode of deformation at a rate of about 5 mm yr it may be stated therefore that the pattern of deformation of the northern aegean and the northern part of north anatolian fault is controlled by the ns extension the aegean is undergoing as a whole and the dextral strike slip motion of the north anatolian fault the southern part of north anatolia is undergoing crustal thinning at a rate of 2 3 mm yr ns extension at a rate of 5 mm yr as well as ew extension at a rate of 4 mm yr which are consistent with the occurrence of major normal faulting and justify the separation of north anatolia into two separate subareas

ecosystem development following deglaciation a new sedimentary record from devils lake wisconsin usa abstract processes and rates of ecosystem development can be reconstructed using lacustrine sedimentary sequences but this approach often requires records that contain the start of primary succession most lakes in the upper midwestern u s were formed by glaciers at the end of the last ice age approximately 11 700 cal yr bp devils lake wisconsin is a rare example of a lake from this region whose sediments extend into the pleistocene and may include the last glacial maximum sediment magnetic geochemical pollen and charcoal records were generated from a 10 m core whose basal sediments may be 28 000 years old together with a previously published pollen record these proxies combine to reveal a history of long term climatic vegetative and geologic change during the late pleistocene to holocene we identify six sedimentary units that indicate a series of consecutive events rather than a predictable trajectory of ecosystem development at the site productivity in the lake was low during the late pleistocene and increased during the holocene as reflected by the sediment lithology which shows a sudden shift from glacial vivianite rich and organic poor clastic dominated sediments to holocene diatomaceous sapropels several important processes initiated around 17 000 cal yr bp including the onset of organic matter accumulation and fire in the terrestrial ecosystem however the post glacial landscape was not devoid of vegetation because pollen assemblages indicate that terrestrial vegetation likely a spruce tundra survived near the site a switch to a hardwood forest period during the holocene also led to a change in the fire regime with increased frequency of burning aquatic ecosystem productivity lagged terrestrial ecosystem productivity throughout the record nutrient cycling as recorded by sedimentary 15n was variable but not directional and appeared to be correlated with climate conditions early in the record and terrestrial ecosystem processes later in the record throughout the holocene magnetic mineral concentration decreased as productivity increased and the source of magnetic material shifted from almost exclusively lithogenic to approximately 50 derived from soil or biogenic sources magnetic grain size ambrosia pollen percentages and charcoal concentration increased and 15n decreased in the most recent part of the record due to anthropogenic influence in the region including agricultural activities

large eddy simulation of the diurnal cycle of shallow cumulus convection over land summary large eddy simulations of the development of shallow cumulus convection over land are presented many characteristics of the cumulus layer previously found in simulations of quasi steady convection over the sea are found to be reproduced in this more strongly forced unsteady case furthermore the results are shown to be encouragingly robust with similar results obtained with eight independent models and also across a range of numerical resolutions the datasets produced are already being used in the development and evaluation of parametrizations used in numerical weather prediction and climate models

convectively induced secondary circulations in fine grid mesoscale numerical weather prediction models abstractmesoscale numerical weather prediction models using fine grid o 1 km meshes for weather forecasting environmental assessment and other applications capture aspects of larger than grid mesh size convectively induced secondary circulations ciscs such as cells and rolls that occur in the convective planetary boundary layer pbl however 1 km grid spacing is too large for the simulation of the interaction of ciscs with smaller scale turbulence the existence of ciscs also violates the neglect of horizontal gradients of turbulent quantities in current pbl schemes both aspects poorly resolved ciscs and a violation of the assumptions behind pbl schemes are examples of what occurs in wyngaard s terra incognita where horizontal grid spacing is comparable to the scale of the simulated motions thus model ciscs m ciscs cannot be simulated reliably this paper describes how the superadiabatic layer in the lower convective pbl together with increased horizontal resolution allow the critical ra

late quaternary fires and grassland palaeoecology of mount kenya east africa evidence from charred grass cuticles in lake sediments abstract multi proxy evidence from sacred lake on mount kenya including pollen and compound specific carbon isotope data indicates grassland expansion at the last glacial maximum lgm circa 18 000 14c years bp but lacks the taxonomic resolution with which to derive ecological inferences about past grasslands analysis of grass cuticles preserved in east african lake sediments is presented here as a palaeoecological tool for addressing this problem sub fossil grass cuticles retain micro morphological features that often permit identification to subfamily supertribe tribe and in some instances genus or species level a method for isolating and identifying this novel resource is presented along with an analysis of late quaternary to recent age sediments from sacred lake mount kenya data derived from 43 sediment samples and over 5000 graminoid cuticles support isotopic evidence for the presence of grasslands at sacred lake during the lgm size class analysis of charred graminoid fragments indicates that relatively local low intensity fires occurred throughout the sequence current autoecological understanding of the taxa identified indicates that the grassland present at the lgm possessed specific adaptations to burning we conclude that fire was an important landscape feature on mount kenya reinforcing the impact of past variations in climate and atmospheric co2

charcoal signatures defined by multivariate analysis of charcoal records from 10 lakes in northwest wisconsin usa article i nfo article history received 16 july 2007 available online 20 november 2010 we show how sedimentary charcoal records from multiple sites within a single landscape can be used to compare fire histories and reveal small scale patterns in fire regimes our objective is to develop strategies for classifying and comparing late holocene charcoal records in midwestern oak and pine dominated sand plain ecosystems where fire regimes include a mix of surface and crown fires using standard techniques for the analysis of charcoal from lake sediments we compiled 1000 to 4000 yr long records of charcoal accumulation and charcoal peak frequencies from 10 small lakes across a sand plain in northwestern wisconsin we used cluster analysis to identify six types of charcoal signatures that differ in their charcoal influx rates amount of grass charcoal and frequency and magnitude of charcoal peaks the charcoal records demonstrate that while fire histories vary among sites there are regional patterns in the occurrence of charcoal signature types that are consistent with expected differences in fire regimes based on regional climate and vegetation reconstructions the fire histories also show periods of regional change in charcoal signatures occurring during times of regional climate changes at 700 1000 and 3500 cal yr bp

late quaternary vegetation climate and fire history of the southeast atlantic coastal plain based on a 30 000 yr multi proxy record from white pond south carolina usa the patterns and drivers of late quaternary vegetation dynamics in the southeastern united states are poorly understood due to low site density problematic chronologies and a paucity of independent paleoclimate proxy records we present a well dated 15 accelerator mass spectrometry 14 c dates 30 000 yr record from white pond south carolina that consists of high resolution analyses of fossil pollen macroscopic charcoal and sporormiella spores and an independent paleotemperature reconstruction based on branched glycerol dialkyl tetraethers between 30 000 and 20 000 cal yr bp open pinus picea forest grew under cold and dry conditions elevated quercus before 26 000 cal yr bp however suggest warmer conditions in the southeast before the last glacial maximum possibly corresponding to regionally warmer conditions associated with heinrich event h2 warming between 19 700 and 10 400 cal yr bp was accompanied by a transition from conifer dominated to mesic hardwood forest sporormiella spores were not detected and charcoal was low during the late glacial period suggesting megaherbivore grazers and fire were not locally important agents of vegetation change pinus returned to dominance during the holocene with step like increases in pinus at 10 400 and 6400 cal yr bp while charcoal abundance increased tenfold likely due to increased biomass burning associated with warmer conditions low intensity surface fires increased after 1200 cal yr bp possibly related to the establishment of the mississippian culture in the southeast

postglacial vegetation climate and fire history along the east side of the andes lat 41 42 5 s argentina abstract the history of the low elevation forest and forest steppe ecotone on the east side of the andes is revealed in pollen and charcoal records obtained from mid latitude lakes prior to 15 000 cal yr bp the vegetation was characterized by steppe vegetation with isolated stands of nothofagus the climate was generally dry and the sparse vegetation apparently lacked sufficient fuels to burn extensively after 15 000 cal yr bp a mixture of nothofagus forest and shrubland steppe developed fire activity increased between 13 250 and 11 400 cal yr bp contemporaneous with a regionally defined cold dry period huelmo mascardi cold reversal the early holocene period was characterized by an open nothofagus forest shrubland mosaic and fire frequency was high in dry sites and low in wet sites the data suggest a sharp decrease in moisture eastward from the andes a shift to a surface fire regime occurred at 7500 cal yr bp at the wet site and at 4400 cal yr bp at the dry site preceding the expansion of austrocedrus by 1000 1500 yr the spread of austrocedrus is explained by a shift towards a cooler and wetter climate in the middle and late holocene the change to a surface fire regime is consistent with increased interannual climate variability and the onset or strengthening of enso the present day mixed forest dominated by nothofagus and austrocedrus was established in the last few millennia

near vertical seismic reflection image using a novel acquisition technique across the vrancea zone and foscani basin south eastern carpathians romania the dacia plan danube and carpathian integrated action on process in the lithosphere and neotectonics deep seismic sounding survey was performed in august september 2001 in south eastern romania at the same time as the regional deep refraction seismic survey vrancea 2001 the main goal of the experiment was to obtain new information on the deep structure of the external carpathians nappes and the architecture of tertiary quaternary basins developed within and adjacent to the seismically active vrancea zone including the focsani basin the seismic reflection line had a wnw ese orientation running from internal east carpathians units across the mountainous south eastern carpathians and the foreland focsani basin towards the danube delta there were 131 shot points along the profile with about 1 km spacing and data were recorded with stand alone reftek 125s also known as btexansq supplied by the university texas at el paso and the passcal institute the entire line was recorded in three deployments using about 340 receivers in the first deployment and 640 receivers in each of the other two deployments the resulting deep seismic reflection stacks processed to 20 s along the entire profile and to 10 s in the eastern focsani basin are presented here the regional architecture of the latter interpreted in the context of abundant independent constraint from exploration seismic and subsurface data is well imaged image quality within and beneath the thrust belt is of much poorer quality nevertheless there is good evidence to suggest that a thick 10 km sedimentary basin having the structure of a graben and of indeterminate age underlies the westernmost part of the focsani basin in the depth range 10 25 km most of the crustal depth seismicity observed in the vrancea zone as opposed to the more intense upper mantle seismicity appears to be associated with this sedimentary basin the sedimentary successions within this basin and other horizons visible further to the west beneath the carpathian nappes suggest that the geometry of the neogene and recent uplift observed in the vrancea zone likely coupled with contemporaneous rapid subsidence in the foreland is detached from deeper levels of the crust at about 10 km depth the moho lies at a depth of about 40 km along the profile its poor expression in the reflection stack being strengthened by independent estimates from the refraction data given the apparent thickness of the meta sedimentary supracrustal units the crystalline crust beneath this area is quite thin b20 km supporting the hypothesis that

palynological evidence of climate change and land degradation in the lake baringo area kenya east africa since ad 1650 abstract paleoenvironmental records derived from pollen fungal spores and microscopic charcoal from lake baringo kenya reveal a largely dry environment in the east african region since ad 1650 the dry environment is punctuated by a succession of centennial to decadal scale wet and dry episodes disjointed by sharp transitions including two intense dry episodes that led to drying of the lake at ca ad 1650 and ad 1720 which coincide with the little ice age lia period in europe the baringo record shows that land degradation in the area began prior to the colonial period in east africa and has persisted to the present land degradation and increased soil erosion in the lake baringo drainage basin was severe enough to significantly age the lake sediments due to influx of old carbon resulting in the dating inversion

ams 14c dates for extinct lemurs from caves in the ankarana massif northern madagascar abstract an extensive late quaternary fauna including many extinct giant lemurs has been collected recently in a 110 km system of caves in the ankarana massif of northern madagascar ams 14c dates for the acid insoluble collagen gelatin fraction of bones of the giant lemur megaladapis 26 150 400 and 12 760 70 yr b p confirm its presence in the area during the late pleistocene and provide the first pleistocene 14 c ages from bones of the extinct megafauna of the island the first date from bones of the recently described extinct babakotia radofilai 4400 60 yr b p shows that it was present in northern madagascar in mid holocene times a comparatively recent age of 1020 50 yr b p for the extinct archaeolemur indicates survival of this genus for at least a millennium after the first direct evidence for humans in madagascar this suggests that the island s extinction window may have represented a longer time span than would have been expected under the blitzkrieg model of late quaternary extinctions a mid holocene age 4560 70 yr b p for a bone sample of the small extant lemur hapalemur simus indicates that the disappearance of this now restricted species from the ankarana occurred after this date new data from the ankarana and other sites on the island add to the consensus that major biotic changes occurred on madagascar in the late holocene

2 5d seismic velocity modelling in the south eastern romanian carpathians orogen and its foreland 2 5 d seismic velocity modelling in the south easter romainan carpathians orogen and its foreland

modern pollen spectra from madagascar abstract modern sediments from 13 perennial lakes and bogs in central eastern and northern madagascar malagasy republic provide information concerning modern pollen rain many of the major pollen types could be positively identified to genus land cover analysis utilizing landsat mss false color imagery stereo airphotos published vegetation maps and ground reconnaissance was used to classify the vegetation at each site pollen spectra from environments such as grassland forest and montane shrub grassland have discernible differences wooded grasslands and various types of mosaic environments produce spectra that are of an intermediate character

shallow cumulus representation and its interaction with radiation and surface at the convection gray zone abstractthis study presents a systematic analysis of convective parameterizations performance with interactive radiation microphysics and surface on an idealized day with shallow convection to t

fossil grass cuticles from lacustrine sediments a review of methods applicable to the analysis of tropical african lake cores the need for alternatives to fossil pollen for the reconstruction of vegetation dominated by grasses has prompted the use of grass cuticles which lack a described method of analysis methods used to analyse sediments for palaeoecological materials allied to grass cuticles including microscopic charcoal phytoliths and plant cuticles are reviewed a simple set of methods and protocols for extracting identifying and quantifying fossil grass cuticles are presented

paleoenvironmental change in tropical africa during the holocene based on a record from lake kifuruka western uganda a 10 000 year palynological record of vegetation and environmental changes in tropical africa is presented based on sediment data from a 230 cm long core recovered from lake kifuruka in western uganda the lake kifuruka record provides new sedimentary and paleoecological data for human environment interactions and anthropogenic disturbance in the tropical african region during the holocene the record shows evidence for prolonged dry conditions in the region at the terminus of the last glaciation period and the onset of the holocene period the early holocene and mid holocene periods were characterized by largely warm and wet climatic conditions the pollen record shows evidence of forest disturbance that is probably associated with agricultural activities near lake kifuruka shortly after ca 4300bp cal a bp coinciding with a time of increased desiccation in the region the forest disturbance in the record appears to have intensified and continued into the modern period but with no significant change in the overall vegetation diversity suggesting quick environmental recovery the lake kifuruka record is largely devoid of the abrupt climatic changes that have been observed from a couple of sites in the east african region which implies that the changes may be site specific rather than regional scale

a high resolution sedimentary charcoal and geochemistry based reconstruction of late holocene fire regimes in the paramo of chirripό national park costa rica multiproxy analysis of two sediment cores recovered from lagos morrenas 3c and ditkebi located in the paramo of costa rica s chirripo national park was undertaken to develop multidecadal scale reconstructions of late holocene fire regimes for the region analysis of macroscopic charcoal and sediment geochemistry c n 13 c 15 n and c n ratios documents periodic burning of the paramo in chirripo national park during the past 1700 yr the charcoal records provide evidence of high fire frequency between ad 560 and 720 and between ad 980 and 1230 severe fire episodes are reflected by a rapid increase in the flux of carbon c and nitrogen n from the surrounding catchment because of the volatilization of paramo vegetation additionally 15 n which sharply increases following local fire events captures postfire changes in nutrient loading and likely the decadal scale rate of postfire recovery of paramo vegetation the consistently high 13 c and c n values observed between ad 700 and 1100 suggest an expansion of muhlenbergia a native c 4 grass growing near shore suggesting that the interval between ad 700 and 1100 broadly corresponding to the terminal classic drought and medieval climate anomaly was characterized by a decrease in effective moisture and temperature

a formulation for reliable estimation of active crustal deformation and its application to central greece summary a procedure for the analysis of data concerning seismic moment release and fault plane solutions for the estimation of active crustal deformation is proposed the formulation takes advantage of all the available historical and instrumental data for the calculation of the size of the deformation in a seismic zone and of all the reliable fault plane solutions which are available for a broader seismic belt for the determination of the shape of the deformation a detailed analysis of the errors involved in each parameter based on a monte carlo numerical method is suggested the proposed procedure is applied to a region of extensional tectonics in central greece the resulting seismic strain rates show that the dominant mode of deformation in the area is extension at a rate of the order of 6 mm yr and a mean azimuth of n25 w a vertical contraction rate of about 1 mm yr has also been calculated the results from geodetic measurements performed by billiris et al 1991 declare that the calculated seismic deformation represents about 60 per cent of the total strain of this area

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

1200 years of fire and vegetation history in the willamette valley oregon and washington reconstructed using high resolution macroscopic charcoal and pollen analysis article high resolution macroscopic charcoal and pollen analyses were used to reconstruct the fire and vegetation history of the willamette valley for the last 1200 years presented in this paper are three new paleoecological reconstructions from lake oswego porter lake and warner lake oregon and portions of previous reconstructions from battle ground lake washington and beaver lake oregon the reconstructions show that prior to euro american settlement vegetation and fire regimes were influenced by a combination of natural and anthropogenic factors battle ground lake shows a stronger influence from climate while lake oswego beaver lake porter lake and warner lake were more controlled by human activity however human set fires were also modulated by regional climate variability during the medieval climate anomaly and the little ice age fire reconstructions from battle ground lake lake oswego beaver lake and porter lake imply that fires were infrequent in the willamette valley 200 300 years prior to euro american settlement the decline of native american populations due to introduced disease may have led to this reduction in fire activity the prehistoric record from warner lake however indicates that fires in the foothills of the cascade range were more frequent than on the valley floor at least until ca ad 1800 the historic portions of the reconstructions indicate that euro american land clearance for agriculture and logging produced the most dramatic shifts in vegetation and fire regimes all five records indicate that few fires in the willamette valley have occurred since ca ad 1930 and fires today are predominantly grass fires 2010 elsevier b v all rights reserved

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

δ13c analyses of individual lignin phenols in quaternary lake sediments a novel proxy for deciphering past terrestrial vegetation changes this study of the sediments from sacred lake mount kenya demonstrates that 13 c analyses of individual lignin phenols can be used to assess past changes in the proportion of c 3 and c 4 plants within different plant groups in the lake catchment vegetation changes resulting from climatic and atmospheric changes since the last glacial maximum can be deduced from specific lignin phenols lignin a major biopolymer in vascular plants differs from n alkyl lipids in 1 its higher specificity and more quantitative representation of vascular plant input and 2 its major transport mechanism into the sediments by fluvial runoff as opposed to the greater importance of eolian transport for leaf waxes and pollen lignin 13 c data support the hypothesis that atmospheric co 2 concentration is an important factor controlling the vegetation in tropical mountain ecosystems and provide additional insights into past changes in vegetation structure specifically the 13 c values of p coumaric acid indicate the persistence of c 4 grasses during the late glacial when the lake level was lower than today suggesting that aridity also played a role in controlling the abundance of c 4 plants

late quaternary vegetation changes around lake rutundu mount kenya east africa evidence from grass cuticles pollen and stable carbon isotopes woody subalpine shrubs and grasses currently surround lake rutundu mount kenya multiple proxies including carbon isotopes pollen and grass cuticles from a 755 cm long core were used to reconstruct the vegetation over the past 38 300 calendar years stable carbon isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the c4 photosynthetic pathway was greater during the late pleistocene than in the holocene pollen data show that grasses were a major constituent of the vegetation throughout the late pleistocene and holocene the proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum lgm grass cuticles confirm evidence that c4 grass taxa were present at the lgm and that the majority followed the cold tolerant nadp mec4 subpathway copyright 2003 john wiley sons ltd

a 14 300 year long record of fire vegetation climate linkages at battle ground lake southwestern washington high resolution macroscopic charcoal analysis was used to reconstruct a 14 300 year long fire history record from the lower columbia river valley in southwestern washington which was compared to a previous vegetation reconstruction for the site in the late glacial period ca 14 300 13 100 cal yr bp pinus picea dominated parkland supported little to no fire activity from the late glacial to the early holocene ca 13 100 10 800 cal yr bp pseudotsuga abies dominated forest featured more frequent fire episodes that burned mostly woody vegetation in the early to middle holocene ca 10 800 5200 cal yr bp quercus dominated savanna was associated with frequent fire episodes of low to moderate severity with an increased herbaceous i e grass charcoal content from the middle to late holocene ca 5200 cal yr bp to present forest dominated by pseudotsuga thuja type and tsuga heterophylla supported less frequent but mostly large or high severity fire episodes fire episodes were least frequent but were largest or most severe after ca 2500 cal yr bp the fire history at battle ground lake was apparently driven by climate directly through the length and severity of the fire season and indirectly through climate driven vegetation shifts which affected available fuel biomass

analyzing the grell freitas convection scheme from hydrostatic to nonhydrostatic scales within a global model abstractthe authors implemented the grell freitas gf parameterization of convection in which the cloud base mass flux varies quadratically as a function of the convective updraft fraction in the global nonhydrostatic model for prediction across scales mpas they evaluated the performance of gf using quasi uniform meshes and a variable resolution mesh centered over south america the resolution of which varied between hydrostatic 50 km and nonhydrostatic 3 km scales four day forecasts using a 50 km and a 15 km quasi uniform mesh initialized with gfs data for 0000 utc 10 january 2014 reveal that mpas overestimates precipitation in the tropics relative to the tropical rainfall measuring mission multisatellite precipitation analysis data results of 4 day forecasts using the variable resolution mesh reveal that over the refined region of the mesh gf performs as a precipitating shallow convective scheme whereas over the coarse region of the mesh gf acts as a conventional deep convective scheme a

multiple proxy analyses of a u th dated stalagmite to reconstruct paleoenvironmental changes in northwestern madagascar between 370 ce and 1300 ce abstract the timing and causes of paleoenvironmental changes in madagascar have been debated specifically in respect to human activity following the settlement in the late holocene here we present 18o 13c layer bounding surfaces layer specific width mineralogy and distribution of macroholes from stalagmite ma3 from anjohibe cave to provide a detailed understanding of the paleoenvironmental changes in northwestern madagascar between 370 ce and 1300 ce the stable isotope records of stalagmite ma3 are compared with stable isotope records of stalagmites anj94 5 and ma2 detailed examination of the proxies suggests three distinct intervals of changes 1 prior to 795 ce changes in vegetation seem to have responded to changes in monsoonal rainfall linked to the relative position of the itcz the period between ca 755 ce and 795 was the driest and the stalagmite ma3 record is consistent with sediment records pollen and lithology from lake mitsinjo northwestern madagascar and with sediment records fossil pollen and charcoal from sainte luce southeastern madagascar 2 between 795 ce and 870 the environmental conditions became more favorable when vegetation recovered from the driest interval the new conditions must have been suitable for community development in the region as suggested by archaeological evidence around lake mitsinjo and the boeny region and the establishment of the stone town of mahilaka 3 after 870 ce a gradational change in plant communities from c3 to c4 marks the record until around 1130 ce after which vegetation was dominated by c4 plants this change cannot be explained by climate alone as there is no clear relationship in the climate sensitive proxies instead it could have been caused by tavy a variety of swidden agriculture practiced in the region

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

what the past can say about the present and future of fire wildfires are an integral part of most terrestrial ecosystems paleofire records composed of charcoal soot and other combustion products deposited in lake and marine sediments soils and ice provide a record of the varying importance of fire over time on every continent this study reviews paleofire research to identify lessons about the nature of fire on earth and how its past variability is relevant to modern environmental challenges four lessons are identified first fire is highly sensitive to climate change and specifically to temperature changes as long as there is abundant dry fuel we can expect that in a warming climate fires will continue to grow unusually large severe and uncontrollable in fire prone environments second a better understanding of slow interannual to multidecadal socioecological processes is essential for predicting future wildfire and carbon emissions third current patterns of burning which are very low in some areas and very high in others are often unprecedented in the context of the holocene taken together these insights point to a fourth lesson that current changes in wildfire dynamics provide an opportunity for paleoecologists to engage the public and help them understand the potential consequences of anthropogenic climate change