tree rings and the climate of new caledonia sw pacific preliminary results from araucariacae abstract the dendroclimatologic potential of some araucariacae of new caledonia including agathis or kauris and araucaria is assessed using ring thickness and 18o measurements new caledonia is a group of islands in the sw pacific that are currently under influence of enso events endemic to new caledonia the long living species of agathis lanceolata and a ovata growing on poor ultramafic derived soils may provide valuable proxies for the local climate and for enso these trees present visible growth bands of changing thickness along their circumference however several bands are locally absent and the growth axis is generally offset with respect to the geometrical axis of the tree this led us to compute so called composite ring thickness profiles accounting for the geometry of growth bands on the whole surface of a tree disk our computational method involves 10 optical density profiles measured along 10 equally spaced radii drawn from the bark toward the growth axis and 10 to 20 master rings that can be easily identified on the whole disk growth bands visible on less than 5 radii were discarded our method is similar to the cross dating method used by dendrochronologists except that it is applied here to a single tree disk our samples consist of three disks of a lanceolata one disk of a ovata and one disk of araucaria columnaris multiple regressions have been computed between composite profiles and climatic variables i e monthly and yearly temperatures and rainfall amounts the best correlation is found between the width of the ring growing between july n 1 and june n with the rainfalls of june n june n 1 and june n 2 monthly rainfalls allow to explain between 20 to 50 of the ring thickness variance a result similar to that obtained with other studies on agathis of new zealand no temperature parameter appears in the most stable regressions 30 measurements of tree ring cellulose 18o have been conducted on one single disk selected for the strong climate ring width correlation while earlier studies have used 18o measurements to identify seasonal cycles in tropical woods and date the rings our data suggest that the direct use of 18o is misleading due to false rings that do not correspond to a complete growth year when these false rings are identified from the disk analysis and discarded a fair visual correlation with the total rainfall during the growth season is obtained this requires information that cannot be found in single growth band thickness profiles for example as obtained by coring thus araucariacae of new caledonia may present a valuable potential for dendroclimatology however reconstructing a chronology of this region will require more extensive sampling and possibly an account of additional species

fingerprinting the 8 2 ka bp event climate response in a coupled climate model using results from coupled climate model simulations of the 8 2 ka climate event that produced a cold period over greenland in agreement with the reconstructed cooling from ice cores we investigate the typical pattern of climate anomalies fingerprint to provide a framework for the interpretation of global proxy data for the 8 2 ka climate event for this purpose we developed an analysis method that isolates the forced temperature response and provides information on spatial variations in magnitude timing and duration that characterise the detectable climate event in proxy archives our analysis shows that delays in the temperature response to the freshwater forcing are present mostly in the order of decades 30 a over central greenland the north atlantic ocean initially cools in response to the freshwater perturbation followed in certain parts by a warm response this delay occurring more than 200 a after the freshwater pulse hints at an overshoot in the recovery from the freshwater perturbation the south atlantic and the southern ocean show a warm response reflecting the bipolar seesaw effect the duration of the simulated event varies for different areas and the highest probability of recording the event in proxy archives is in the north atlantic ocean area north of 40 n our results may facilitate the interpretation of proxy archives recording the 8 2 ka event as they show that timing and duration cannot be assumed to correspond with the timing and duration of the event as recorded in greenland ice cores copyright 2011 john wiley sons ltd

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

alluvial charcoal in the sigatoka valley viti levu island fiji abstract charcoal concentrations in alluvial sediments throughout the sigatoka and adjacent catchments western viti levu island fiji were located sampled and where possible dated the earliest date 5579 5052 cal year bp almost certainly predates human arrival and represents a natural fire perhaps associated with drought conditions during an el nino event the next three dates are clustered around the time just after initial human arrival in fiji 2900 2700 cal year bp and could mean that humans transited the area 40 km inland within this time the next date 1520 1260 cal year bp is not associated with any other the final five dates are likewise clustered around the time of the ad 1300 event and are believed to mark the time when permanent inland upland settlement was established in this part of viti levu

central european vegetation response to abrupt climate change at 8 2 ka oxygen isotope records show a major climatic reversal at 8 2 ka in greenland and europe annually laminated sediments from two lakes in switzerland and germany were sampled contiguously to assess the response of european vegetation to climate change ca 8 2 ka with time resolution and precision comparable to those of the greenland ice cores the pollen assemblages show pronounced and immediate responses 0 20 yr of terrestrial vegetation to the climatic change at 8 2 ka a sudden collapse of corylus avellana hazel was accompanied by the rapid expansion of pinus pine betula birch and tilia linden and by the invasion of fagus silvatica beech and abies alba fir vegetational changes suggest that climatic cooling reduced drought stress allowing more drought sensitive and taller growing species to out compete corylus avellana by forming denser forest canopies climate cooling at 8 2 ka and the immediate reorganization of terrestrial ecosystems has gone unrecognized by previous pollen studies on the basis of our data we conclude that the early holocene high abundance of c avellana in europe was climatically caused and we question the conventional opinion that postglacial expansions of f silvatica and a alba were controlled by low migration rates rather than by climate the close connection between climatic change and vegetational response at a subcontinental scale implies that forecasted global warming may trigger rapid collapses expansions and invasions of tree species

palynological study of the late quaternary of loyalty basin sw pacific abstract palynological studies have been carried out on two cores from the loyalty basin one near the new caledonia shore kk 231 and the other near lifou island kk 88 the sediments under consideration cover the interval from the last interglacial to the holocene all the samples revealed the mixing of continental and marine palynomorphs varying with carbonate sediment variations that are themselves correlated with the late quaternary sea level fluctuations dinoflagellate cysts and foraminifera are the dominant components of the marine fraction dinoflagellate cysts reached their maximum abundance during the high sea level of the last interglacial while foraminifera were most abundant during the onset of the holocene transgression changes in the continental palynomorphs can also be observed these seem to be linked to sea level variations modifying conditions of production transport and deposition and to the effects of climatic changes on the community structure of terrestrial vegetation

environments favoring dolomite formation at cold seeps a case study from the gulf of mexico abstract dolomite rarely occurs in modern marine environments while it is ubiquitous in the geological record this apparent contradiction made the formation mechanism of dolomite a long standing problem haunting sedimentologists however dolomite is a constituent of many modern seep carbonates providing an opportunity to investigate the conditions favoring dolomite formation at low temperatures in the shallow subseafloor this study reports the petrology mineralogy carbon and oxygen stable isotopic compositions as well as sulfur isotopic compositions of both carbonate associated sulfate cas and chromium reducible sulfur crs of a set of dolomite bearing carbonates from two seep sites gc140 and gb382 on the northern slope of the gulf of mexico the 13c values of carbonates vary from 50 0 to 3 2 v pdb confirming that carbonate minerals mostly resulted from methane oxidation the corresponding 18o values range from 2 6 to 5 9 v pdb reflecting formation close to equilibrium with seawater composition all carbonate samples with dolomite show similar petrologies and lack skeletal remains of seep dwelling metazoans the homogenous texture of microcrystalline dolomite agrees with its formation in the shallow subseafloor dolomite bearing samples reveal 18ocas 34scas slopes of 0 425 and 0 435 for the two study sites respectively such high slopes are significantly different from the smaller slopes of seep carbonates consisting of calcite from gulf of mexico seeps suggesting low overall sulfate reduction rates during dolomite formation this explanation is also supported by relatively high 34scrs values ranging from 29 4 to 19 0 v cdt and the positive correlation of these values with dolomite contents interestingly an approximately stoichiometric dolomite sample yielded the most positive 34scrs value indicating a formation environment typified by low replenishment of seawater sulfate at a supposedly relatively deep sulfate methane transition zone smtz overall these results confirm that dolomite formation is facilitated where the smtz is situated at relatively great depth where sulfate reduction rates are slowed down due to the buildup of high contents of dissolved sulfide and low seawater sulfate replenishment

vegetation change in the coastal lowland rainforest at avai o vuna swamp vava u kingdom of tonga avai o vuna swamp a small coastal wetland in vava u kingdom of tonga produced a 4500 year pollen and sediment record results are 1 a mid holocene sea level highstand is confirmed for tonga between about 4500 and 2600 14 c yr b p marine clay contains pollen from mangroves rhizophora mangle coastal forest trees barringtonia asiatica and cocos nucifera and rainforest trees alphitonia rhus hedycarya and calophyllum 2 microscopic charcoal first appeared at 2600 14 c yr b p coincident with the arrival of polynesians 3 cocos pandanus excoecaria macaranga and elaeocarpaceae pollen reflects the establishment of a mixed coastal lowland rainforest in the last 2500 years 4 the loss of hedycarya elaeocarpus calophyllum and guettarda and the reduction of terminalia and taxa in the papilionaceae family by about 1000 years ago may be due to habitat destruction and the loss of dispersal capabilities of some species through the extinction of the two largest pigeons in tonga d 2005 university of washington all rights reserved

pollen based quantitative reconstructions of holocene climate variability in nw romania abstract a modern analogue technique is applied to two high resolution pollen sequences from nw romania to provide the first quantitative evidence for winter summer and annual temperatures and for precipitation across the holocene in this region the pollen based climate reconstructions allow the identification of four main intervals i an early less stable period between 11 700 and 11 200 cal yr bp ii generally stable conditions between 11 200 and 8300 cal yr bp with winter and annual temperatures and precipitation higher than at present and summer temperatures about the same iii lower winter and annual temperatures and higher summer temperatures and precipitation between 8000 and 2400 cal yr bp iv warmer winter and annual temperatures and lower precipitation for the last 2400 years whereas summer temperatures became cooler at steregoiu and remained stable at preluca tiganului the pollen based climate reconstructions at the two sites show similar patterns in annual and winter temperatures and precipitation changes during the holocene but the trends appear to be less consistent for summer temperatures our pollen based reconstructions revealed several short term climatic oscillations during the holocene the strongest of which occur between 10 300 10 100 8300 8000 6800 6400 5100 4900 4000 3600 and 3200 3000 cal yr bp

chironomid inferred holocene temperature changes in the south carpathians romania we present a holocene summer air temperature reconstruction based on fossil chironomids from lake brazi 1740 m a s l a shallow mountain lake in the south carpathians summer air temperature rec

a chironomid based reconstruction of late glacial summer temperatures in the southern carpathians romania late glacial and early holocene summer temperatures were reconstructed based on fossil chironomid assemblages at lake brazi retezat mountains with a joint norwegian swiss transfer function providing an important addition to the late glacial quantitative climate reconstructions from europe the pattern of the late glacial temperature changes in lake brazi show both similarities and some differences from the ngrip 18o record and other european chironomid based reconstructions our reconstruction indicates that at lake brazi 1740 m a s l summer air temperature increased by 2 8 c at the oldest dryas bolling transition gs 2 gi 1 and reached 8 1 8 7 c during the late glacial interstade the onset of the younger dryas gs 1 was characterized by a weak 1 c decrease in chironomid inferred temperatures similarly at the gs 1 holocene transition no major changes in summer temperature were recorded in the early holocene summer temperature increased in two steps and reached 12 0 13 3 c during the preboreal two short term cold events were detected during the early holocene between 11 480 11 390 and 10 350 10 190 cal yr bp the first cooling coincides with the preboreal oscillation and shows a weak 0 7 c temperature decrease while the second is characterized by 1 c cooling both cold events coincide with cooling events in the greenland ice core records and other european temperature reconstructions

cold event at 8200 yr b p recorded in annually laminated lake sediments in eastern europe a quantitative annual mean temperature reconstruction from an annually laminated lake sediment sequence in estonia eastern europe shows a distinct cold period at 8400 8080 yr b p before a d 2000 the timing is consistent with that seen in the greenland ice core data and various high resolution records from western europe during maximal cooling at 8250 8150 yr b p the annual mean temperature in estonia was 2 0 c colder than prior to and 3 0 c colder than after the cooling the pollen stratigraphic and sedimentological data suggest especially cold and snowy winter conditions the duration and amplitude of the cold event agree with the modeled impact of a sudden freshening of the north atlantic surface water and subsequent perturbation of the thermohaline circulation provided that the cold event was caused by a pulse of freshwater from the melting laurentide ice sheet to the north atlantic the results indicate a strong teleconnection between the north atlantic oceanic forcing and the east european climate at least up to long 26 e mediated probably by the changing intensity of the zonal atmospheric circulation

model data comparison for the 8 2 ka bp event confirmation of a forcing mechanism by catastrophic drainage of laurentide lakes abstract to improve our understanding of the mechanism behind the 8 2 ka bp cooling event we compare proxy evidence with climate model simulations in which the thermohaline ocean circulation is perturbed by a freshwater pulse into the labrador sea both the proxy data and model results show a cooling that is mainly concentrated in the north atlantic region ranging from more than 5 c cooling in the nordic seas to about 0 5 1 c over europe and less than 0 5 c over the subtropical north atlantic data and model also indicate a weakening of the summer monsoon and generally a drier circum north atlantic over the south atlantic ocean the model simulates a slight warming mostly less than 0 5 c which falls within the uncertainty of proxy data and thus could not be confirmed to examine in detail the structure of the 8 2 ka bp event we also compare the modeled climatological evolution at two locations with high quality records revealing a generally consistent picture the good model data agreement confirms the hypothesis that the 8 2 ka bp event was forced by a freshwater induced weakening of the thermohaline circulation other forcings are unlikely since they would result in an alternative geographical distribution and expression of the climate response

a late quaternary record of environmental change and human impact from new caledonia a late quaternary vegetation record is presented from a lowland site on the leeward southwest coast of new caledonia plum swamp is a backswamp on the plum river at around 10 m a s l just within the ultramafic terrain that dominates the southern third of new caledonia pollen analysis charcoal analysis radiocarbon dating and stratigraphic analysis are employed to reconstruct the vegetation and sedimentary history of the valley the vegetation record commences at around 20 000 yr bp and shows that from this time up until the late holocene the valley was forested the greater representation of taxa more prevalent at higher altitudes during the late glacial suggests a response to cooling and an enrichment of the lowland forest with more montane elements the late glacial transition between 14 000 and 9000 yr bp is a period of instability within the valley when vegetation is disturbed by fire forest recovers after this and there is increasing stability until the arrival of people in the late holocene at around 3000 yr bp the initial colonisers of new caledonia had a profound effect upon the vegetation of the valley converting the lowland forest to a stunted and species poor maquis on the ultramafic sediments and melaleuca woodland on the non ultramafic substrates however sedimentary processes are relatively unchanged during this time dramatic geomorphic change does occur in the catchment though during the latter part of the 20th century as a consequence of mining q 2001 elsevier science b v all rights reserved

holocene changes in seasonal precipitation highlighted by fire incidence in eastern canada postglacial fire history has been reconstructed for eastern canada from charcoal influx anomalies from 30 sites taken from a lacustrine charcoal database the reconstruction exhibits coherent patterns of fire occurrence in space and time the early holocene is characterised by high fire incidence there is a major change to much lower occurrence slightly after 8 ka bp a return to more fire appears after 3 ka bp this sequence does not fit with the hydro climatic reconstruction deduced from lake level reconstructions for northeastern north america which indicates a dry early and mid holocene and a wet late holocene fire occurrence however closely matches summer relative humidity inferred from 18o the differences between fire frequency and lake level history are due to changes in the seasonality of precipitation and drought frequency lake levels are essentially controlled by winter precipitation while summer precipitation controls fire occurrence the early holocene before 8 7 5 ka bp experienced dry summers due to higher solar radiation and dry adiabatic winds from the residual laurentide ice sheet the middle holocene was dominated by wet summers due to stability of the atlantic air mass over eastern canada after 2 5 ka bp summers became drier albeit not as fire conducive as during the early holocene late holocene summers conducive to fire are explained by more frequent incursions of dry cool pacific or cold arctic air masses over eastern canada

a 13 600 year diatom oxygen isotope record from the south carpathians romania reflection of winter conditions and possible links with north atlantic circulation changes this study provides a continuous lateglacial and holocene record of diatom silica oxygen isotope changes 18odiat in a subalpine lake sediment sequence obtained from the retezat mts taul dintre brazi 1740 m a s l this through flow shallow high altitude lake with a surface area of only 0 4 ha has short water residence time and is predominantly fed by snowmelt and rainwater its 18odiat record principally reflects the oxygen isotope composition of the winter and spring precipitation as diatom blooms occur mainly in the spring and early summer hence changes in 18odiat are interpreted as seasonal scale changes in the amount of winter precipitation low oxygen isotope values 27 28 5 occurred during the lateglacial until 12 300 cal bp followed by a sharp increase thereafter in the holocene 18odiat values ranged from 29 to 31 until 3200 cal bp followed by generally lower values during the late holocene 27 30 short term decreases in the isotopic values were found between 10 140 9570 9000 8500 7800 7300 6300 5800 5500 5000 and at 8015 4400 4000 cal bp after 3200 cal bp a decreasing trend was visible with the lowest values between 3100 2500 and after 2100 cal bp the general trend in the record suggests that contribution of winter precipitation was generally lower between 11 680 and 3200 cal bp followed by increased contribution during the last millennia the late holocene decrease in 18odiat shows good agreement with the speleothem 18o lake level and testate amoebae records from the carpathian mountains that also display gradual 18o decrease and lake level mire water table level rise after 3200 cal bp strong positive correlation with north atlantic circulation and solar activity proxies such as the austrian and hungarian speleothem records furthermore suggested that short term increases in the isotopic ratios in the early and mid holocene are likely connectable to high solar activity phases and high frequency of positive north atlantic oscillation indexes that may have resulted in decreased winter precipitation in this region

holocene environmental changes as recorded in the geochemistry of glacial lake sediments from retezat mountains south carpathians abstract sediment cores obtained from two deep 15 m glacial lakes were analyzed in context of terrestrial vegetation development and in lake processes from the retezat mountains southern carpathians romania only the holocene parts were chosen for study for testing what is the connection between geochemical changes and biotas around and in the lakes the lakes are situated at slightly different altitudes on the northern lake gales 1990 m a s l and southern slope lake bucura 2040 m a s l respectively changes in geochemical composition were relatively low amplitude during the studied period 10 300 1790 and 10 300 695 cal yr bp in both lakes but the applicability of enrichment factor ef for geochemical elements and diatom ecological traits guilds in paleoecological reconstruction were demonstrated in this paper the main changes have been observed at ca 10 670 9000 6500 and 3100 cal yr bp in geochemistry vegetation and siliceous algal assemblages catchment soil stabilization was apparent from 9000 cal yr bp onwards in lake and terrestrial productivity was the highest between 9000 and 6500 cal yr bp and human impact became the dominant driver in both terrestrial vegetation and sediment geochemical changes and in lake processes over the last 3400 years in both lakes the geochemical record displayed frequent erosional events within the holocene the strongest soil erosions clustered around 6500 7400 and 3200 900 cal yr bp

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

the late quaternary decline and extinction of palms on oceanic pacific islands late quaternary palaeoecological records of palm decline extirpation and extinction are explored from the oceanic islands of the pacific ocean despite the severe reduction of faunal diversity coincidental with human colonisation of these previously uninhabited oceanic islands relatively few plant extinctions have been recorded at low taxonomic levels recent faunal extinctions on oceanic islands are concentrated in larger bodied representatives of certain genera and families fossil and historic records of plant extinction show a similar trend with high representation of the palm family arecaceae late holocene decline of palm pollen types is demonstrated from most islands where there are palaeoecological records including the cook islands fiji french polynesia the hawaiian islands the juan fernandez islands and rapanui a strong correspondence between human impact and palm decline is measured from palynological proxies including increased concentrations of charcoal particles and pollen from cultivated plants and invasive weeds late holocene extinctions or extirpations are recorded across all five of the arecaceae subfamilies of the oceanic pacific islands these are most common for the genus pritchardia but also many sedis fossil palm types were recorded representing groups lacking diagnostic morphological characters

abrupt changes in early holocene tropical sea surface temperature derived from coral records for many high latitude regions of the globe it is now clear that the transition to modern climate following the last glacial maximum was punctuated by a number of rapid and substantial climate oscillations1 2 in contrast relatively little is known about how the tropics responded to the deglaciation because few high resolution records are available from lower latitudes corals have recently been shown to provide an important source of tropical climate records because they can be easily and accurately dated using either 14c or 230th and because past sea surface temperatures can be recovered from the sr ca ratios in coral skeletons here we use this technique to derive several early holocene sea surface temperature records from a coral drill core recovered from espiritu santo vanuatu in the tropical southwest pacific ocean these records indicate that sea surface temperatures in this region were depressed by as much as 6 5 c below modern values at 10 350 calendar years bp but rose very abruptly during the following 1 500 years this temperature increase lags the post younger dryas increase observed in a coral record from the tropical atlantic ocean3by about 3 000 years an unexpected phase shift that may ultimately shed light on the mechanisms of deglacial climate change

multicentury glacier fluctuations in the swiss alps during the holocene subfossil remains of wood and peat from six swiss glaciers found in proglacial fluvial sediments indicate that glaciers were smaller than the 1985 reference level and climatic conditions allowed vegetation growth in now glaciated basins an extended data set of swiss glacier recessions consisting of 143 radiocarbon dates is presented to improve the chronology of glacier fluctuations a comparison with other archives and dated glacier advances suggests 12 major recession periods occurring at 9850 9600 93008650 85508050 77007550 74506550 61505950 57005500 52004400 43003400 28002700 21501850 14001200 cal yr bp it is proposed that major glacier fluctuations occurred on a multicentennial scale with a changing pattern during the course of the holocene after the younger dryas glaciers receded to a smaller extent and prolonged recessions occurred repeatedly culminating around 7 cal kyr bp after a transition around 6 cal kyr bp weak fluctuations around the present level dominated after 3 6 cal kyr bp less frequent recessions interrupted the trend to advanced glaciers peaking with the prominent little ice age this trend is in line with a continuous decrease of summer insolation during the holocene

mid to late holocene environmental and climatic changes in new caledonia southwest tropical pacific inferred from the littoral plain gouaro deva abstract multiproxy analysis of three littoral cores from western new caledonia supports the hypothesis that the main controlling factors of environmental changes are sea level change enso variability and extra tropical phenomena such as the medieval warm period mwp marked by a tendency for la nina like conditions in the tropical pacific the record starts during the late holocene sea level rise when the terrestrial vegetation indicated wet and cool conditions the site was a coastal bay definitely transformed into a freshwater swamp at around 3400 cal yr bp after the rapid drawdown of sea level to its current level sediments and foraminiferal assemblages indicated subsequent episodes of freshwater infillings emersion or very high energy conditions likely related to climatic changes and mostly controlled by enso variability between 2750 and 2000 cal yr bp relatively dry and cool climate prevailed while wetter conditions predominated between ca 1800 and 900 cal yr bp the rhizophoraceae peak between ca 1080 and 750 cal yr bp coeval with the mwp may indicate a global phenomenon microcharcoal particles present throughout the record increased after 1500 cal yr bp suggesting an anthropogenic source from ca 750 cal yr bp the appearance of current type of vegetation marks the human impact

holocene vegetation history in the upper forest belt of the eastern romanian carpathians abstract pollen analysis supported by nine ams 14 c dates from the poiana tiol peat sequence 1540 m in the rodnei mountains eastern romanian carpathians romania is used to reconstruct the holocene vegetation history in this mountain region the results are then compared with other sequences from romania and eastern europe in order to better understand the past dynamics of the main forest constituents the vegetation record at poiana tiol starts at ca 11 000 cal yr bp with the occurrence of rather closed woodlands composed of betula pinus picea abies alnus a viridis and ulmus picea abies was the dominant tree species for almost the entire period however during the last 3000 years p abies forests were largely replaced by pinus in the area temperate tree taxa fraxinus quercus acer tilia and corylus avellana were also common but likely at lower elevation c avellana expanded around 10 300 cal yr bp and reached maximum values after 9000 cal yr bp pollen of carpinus betulus and fagus sylvatica was already recorded around 7000 cal yr bp however the spread of c betulus occurred at ca 6000 cal yr bp with maximum values between 4800 cal yr bp and 3000 cal yr bp while f sylvatica spread from ca 3200 cal yr bp and attained maximum values between 2000 and 200 cal yr bp the first indications of human activities appeared around 3200 cal yr bp and intensified within the last 200 years comparison with other sequences from romania and surrounding countries reveals both similarity and great differences related to the location of glacial refugia climate change and human impact

reconciling diverse diatom based lake responses to climate change in four mountain lakes in the south carpathian mountains during the last 17 kyrs abstract climatic changes were studied using siliceous algae diatoms and chrysophyta stomatocysts analyses in four mountain lakes in the retezat mountains in the south carpathian mountains with the aim to search for synchrony in aquatic ecosystem responses according to the basal radiocarbon dating of the lake sediment cores these lakes were formed around 17 000 15 000 cal yr bp high resolution diatom analyses were carried out together with loss on ignition loi and biogenic silica bisi measurements on the lakes comparison of the proxy results suggests that despite the different slope aspect water depth and basin parameters diatom assemblage changes show clear synchrony the most remarkable changes in the aquatic ecosystems were observed around 6500 cal yr bp on the northern slope and around 6100 cal yr bp on the southern slope during the holocene evidences for sharp concomitant shifts were found between 9200 9000 and 3200 3000 cal yr bp in the siliceous algal communities on both slopes the late glacial holocene boundary was not pronounced in the shallow lakes but was significant in a deep lake the signs of a dry and bipartite younger dryas gs 1 were evident but floristic changes differed in the lakes principal component analyses explained very similar variances along the first and second axes for three lakes while the fourth lake lake bucura proved less sensitive to climate change due to the dominance of moss inhabiting diatom assemblages lake level changes have only been reconstructed on the basis of diatom life forms in one of the deep lakes lake gales high lake levels were inferred between 9300 9000 and 3000 1700 cal yr bp in addition to loi biogenic silica content bisi was measured on the sediments of the northern slope and pointed to different seasonal biological productivities increasing loi was often coupled with low bisi values

diatom inferred lateglacial and holocene climatic variability in the south carpathian mountains romania climatic and environmental changes were studied using siliceous algae diatoms and chrysophycean cysts analyses in a mountain lake in the south carpathian mountains for the lateglacial and holocene lake brazi 1740 a s l is a small shallow lake in the retezat mountains according to the basal radiocarbon dating of the core the lake was formed around 15 750 cal bp and sediment accumulation has been continuous ever since high resolution diatom analyses were carried out together with loss on ignition and biogenic silica measurements total epilimnetic phosphorus tp concentrations and ph were reconstructed quantitatively ten statistically significant zones were distinguished six of which appeared in the lateglacial and early holocene suggesting the instability of diatom assemblages after deglaciation the uppermost zone covered six thousand years which suggests that diatom assemblages remained quite stable during the second half of the holocene high lake level occurred between 9500 and 9000 cal bp after 6300 cal bp the lake level gradually increased again until 5800 cal bp a further increase was detected at 3000 cal bp while after 1500 cal bp water level decreased although there is limited knowledge regarding the environmental constraints of several diatom taxa present in the sequence e g aulacoseira laevissima which makes the precise environmental interpretation of the diatom record more difficult the available data provide an important new insight into the environmental history of lake brazi and the carpathian mountains the most remarkable changes in the aquatic ecosystem were observed at 6000 cal bp in the holocene and 12 800 cal bp at the onset of the younger dryas marked changes were also detected at 10 500 10 300 9800 9500 9000 8900 8800 8300 6300 5800 and 3100 3000 cal bp

coral record of equatorial sea surface temperatures during the penultimate deglaciation at huon peninsula uplifted coral terraces at huon peninsula papua new guinea preserve a record of sea level sea surface temperature and salinity from the penultimate deglaciation remnants have been found of a shallow water reef that formed during a pause similar to the younger dryas in the penultimate deglaciation at 130 000 2000 years ago when sea level was 60 to 80 meters lower than it is today porites coral which grew during this period has oxygen isotopic values and strontium calcium ratios that indicate that sea surface temperatures were much cooler 22 2 c than either last interglacial or present day tropical temperatures 29 1 c these observations provide further evidence for a major cooling of the equatorial western pacific followed by an extremely rapid rise in sea level during the latter stages of termination ii

a late holocene record of human impact from the southwest coast of new caledonia a late holocene vegetation record is presented from the southwest coast of new caledonia lac saint louis is a freshwater swamp at 3 m a s l adjacent to the river coulee delta pollen analysis charcoal analysis radiocarbon dating and stratigraphic analyses have been used to reconstruct the vegetation and sedimentary history of the swamp the sediment record commences at 6000 bp and reflects rapid flood plain development associated with postglacial sea level rise this rapid accumulation of sediment ceased around 5500 bp and the site became a freshwater swamp from 5500 to 3000 bp the pollen record reflects several aspects of this coastal landscape coastal forest the swamp surface and the adjacent mangrove zone at 3000 bp charcoal levels increase significantly in conjunction with abrupt changes in the pollen record mangrove pollen declines and pollen indicative of coastal forest is replaced by pollen indicative of coastal savanna these changes coincide with the commencement of the archaeological record in new caledonia and mirror similar changes in other late holocene records elsewhere on the island and are interpreted as representing human impact yam terraces surrounding lac saint louis may have been built around 2000 bp based on mineral magnetic measurements and charcoal accumulation the decline in mangrove vegetation adjacent to site may be the result of a late holocene fall in sea level increased sedi ment accumulation along the coastal foreshore as a result of forest clearance in the river coulee s catch ment however is also considered

early holocene climatic oscillations recorded by lake level fluctuations in west central europe and in central italy abstract on the basis of lake level data the period of the preboreal oscillation pbo at 11 300 11 150 cal yr bp as defined by the grip oxygen isotope record appears to correspond to wetter climatic conditions in west central europe and to a marked drying in north central italy additional short lived phases of higher lake level have been identified before the pbo at ca 11 450 11 400 and 11 350 cal yr bp in west central europe and at ca 11 500 cal yr bp in italy such multiple climatic oscillations around the pbo have been observed in various records in northwestern europe on the basis of various proxies a map of changes in moisture over western europe during the pbo indicates a mid latitude zone between 58 and 43 n characterised by wetter conditions while a drier climate developed in southern and northern europe this wet middle zone shows a larger extension and suggests a more meandering weaker atlantic westerly jet during the pbo than during the 8 2 kyr event a comparison of lake level records in west central europe with 1 outbursts from north american and north european proglacial lakes and 2 variations in solar activity as reflected by 14 c and the 10 be records supports the hypothesis that the pbo was a response to successive meltwater pulses at 11 300 11 250 11 200 and 11 170 cal yr bp and to a sudden decrease in solar activity at 11 250 cal yr bp this study points to the necessity of developing integrated multi proxy approaches to construct more robust regional event stratigraphies and of better documenting palaeohydrological changes in the mediterranean area

rapid vegetation response to lateglacial and early holocene climatic fluctuation in the south carpathian mountains romania abstract high resolution pollen conifer stomata and plant macrofossil analyses of two glacial lake sediments 1740 and 1990 m a s l are used to reconstruct lateglacial lg and early holocene eh vegetation and tree line changes in the retezat mountains our results show that during the lg tree line was between 1750 and 1800 m a s l formed by larix decidua pinus mugo and picea abies early lg spread to high altitudes suggests refugia of these tree species in the mountain the younger dryas cooling resulted in regional steppe tundra expansion but tree line position and composition showed little change the abundance of trees and shrubs decreased at 1740 m a s l but species richness increased with the arrival of pinus cembra our data support climate model hindcasts for only modest decrease in accumulated growing season heat at mid high altitudes regionally the pollen records suggest enhanced aridity and seasonality in the eh tree line reached 2000 m a s l higher than today by 11 100 cal yr bp p mugo p cembra p abies established around the upper lake suggesting rapid increase in summer temperatures the eh maximum of l decidua between 11 200 10 600 cal yr bp was connected to high summer insolation high altitude expansion of abies alba between 10 600 10 300 cal yr bp suggested summer mean temperatures 2 8 c higher then today in comparison with other mountain sites in europe lg interstadial tree line was at similar altitude in the s alps and 350 m higher in the pirin mountains lg tree line fluctuation had similar low amplitude in the se alps retezat and pirin mts suggesting relatively weak influence of the north atlantic thermohaline circulation changes on growing season temperatures

ultra distal fine ash occurrences of the icelandic askja s plinian eruption deposits in southern carpathian lakes new age constraints on a continental scale tephrostratigraphic marker here we present the results of the first cryptotephra investigation of two late glacial holocene lake records from the southern carpathian mountains in romania lake brazi and lake lia the discovery of an important icelandic tephrostratigraphic marker the askja s in the sedimentary records of both sites significantly extends the known ash dispersal from this plinian eruption bayesian age depth modelling of available radiocarbon 14c data from both sedimentary records allows us to further refine the depositional age of this ultra distal tephra in combination with age constraints on the tephra from other well dated european sites we produce an updated age for this key tephrostratigraphic marker of 10 824 97 cal yrs bp 95 4 range the askja s tephra is stratigraphically positioned after the palaeoenvironmental proxy response to the preboreal oscillation at both sites the widespread distribution of this tephra across europe offers the potential to assess spatio temporal variability of this climatic signal the discovery of the askja s in lake records from the southern carpathians highlights the likelihood of finding other ultra distal icelandic cryptotephra marker layers within the region additionally given the location of the carpathian region it offers the opportunity to further enhance and integrate tephrostratigraphic frameworks of north western europe with those of the mediterranean and anatolia regions which will enable a more precise comparison of palaeoenvironmental archives across europe

late holocene paleoenvironment in northern new caledonia southwestern pacific from a multiproxy analysis of lake sediments abstract lithostratigraphic and palynological analysis of two cores recovered from the grand lac new caledonia combined with 35 14 c ams dates yields a paleoenvironmental record spanning the last 2000 yr the lithology is represented mainly by clayey or laminated layers a catastrophic event which is marked by very coarse deposits occurred probably between ca 1070 960 cal yr b p and possibly is associated with an unusually severe la nina event before and after this event a similar combination of the two main sediment types is recorded the repeated alternation of laminated and clayey layers is interpreted as the response to local hydrologic forcing which may reflect a shift from relatively wet to relatively drier conditions respectively variable amount of micro charcoal is detected all along the profile without additional evidence notwithstanding the initial local human settlement documented since ca 2900 14 c yr b p micro charcoal occurrence and variability cannot be linked directly to an anthropogenic origin no distinct palynological zonations in relation to the lithology are observed and the vegetation changes may only represent minor transitions across environmental limits

pollen inferred palaeoclimate reconstructions in mountain areas problems and perspectives transfer functions are an efficient tool for the quantitative reconstruction of past climate from low to mid elevation pollen sites however the application of existing methods to high altitude pollen assemblages frequently leads to unrealistic results in the aim of understanding the causes of these biases the standard best modern analogue method has been applied to two high altitude pollen sequences to provide quantitative climate estimates for the lateglacial and holocene periods both pollen sequences laghi dell orgials 2130 m sw aspect and lago delle fate 2240 m e aspect are located in the subalpine belt on opposing sides of the st anna di vinadio valley italian maritime alps different results were obtained from the two sequences the largest differences occurred in palaeotemperature reconstruction with notable differences in both the values and trends at each site these biases may be attributed to 1 a lack of high elevation best modern analogues in the database of modern samples 2 the problem of pollen taxa that have multiple climatic significance 3 problems related to the complexity of mountainous ecosystems such as the phenomenon of uphill transport of tree pollen by wind possible improvements to the reconstruction process are discussed copyright 2006 john wiley sons ltd

vegetation responses to the 8200 cal bp cold event and to long term climatic changes in the eastern alps possible influence of solar activity and north atlantic freshwater pulses subfossil pollen from two bogs in temperature sensitive high altitude regions were analysed in order to reconstruct early to mid holocene summer temperature fluctuations in the eastern alps the p

holocene climate variability although the dramatic climate disruptions of the last glacial period have received considerable attention relatively little has been directed toward climate variability in the holocene 11 500 cal yr b p to the present examination of similar to50 globally distributed paleoclimate records reveals as many as six periods of significant rapid climate change during the time periods 9000 8000 6000 5000 4200 3800 3500 2500 1200 1000 and 600 150 cal yr b p most of the climate change events in these globally distributed records are characterized by polar cooling tropical aridity and major atmospheric circulation changes although in the most recent interval 600 150 cal yr b p polar cooling was accompanied by increased moisture in some parts of the tropics several intervals coincide with major disruptions of civilization illustrating the human significance of holocene climate variability c 2004 university of washington all rights reserved

a long vegetation history from lowland irian jaya indonesia abstract this paper reports the pollen analysis of a 10 m core from a mire at 780 m altitude and 2 s latitude on ultrabasic soils on a northern coastal range of new guinea the area is almost undisturbed by humans and the record is believed to cover about 60 000 yr b p the results show that montane forest grew around the site continously through the late pleistocene with a distinct increases in higher altitude taxa from 25 000 to 10 500 yr b p the time of glacial maxima elsewhere the invasion of the site by lower altitude forest which commenced at 10 500 yr b p was reversed after a few hundred years and was not finally completed until about 7000 yr b p the results show that vegetation in the region has been sensitive to climatic change the pleistocene ecology being consistent with a temperature change of about 3 4 c times of change agree with other tropical areas even though the site climate was probably affected by changing sea levels however the tropical forest demonstrates overall long term stability in which changes in dominance may reflect minor shifts in disturbance and tree longevity a distinctive record of fine charcoal occurs after 10 900 yr b p but not at any level prior to that time this shows that the forest was continously fire free for a very long time the charcoal is probably an indication of anthropogenic disturbance which may correlate with the spread of agricultural innovation in lowland new guinea an increase in secondary species after 7000 yr b p may be a result of minor anthropogenic activity or the result of warmer conditions and shorter tree life in the lower altitude forests

isotopic climate record in a holocene stalagmite from ursilor cave romania the pu 2 stalagmite from ursilor cave provides the first dated romanian isotope record for the holocene the overall growth rate of the speleothem was 3 5 cm kyr 1 corresponding to a temporal resolution of 142 y between each isotope analysis the hendy tests indicate that isotopic equilibrium conditions occurred during the formation of pu 2 and hence that it is suitable for palaeoclimatic studies the relationship between 18 o and temperature was found to be positive this can be interpreted either as rain out with distance from the west northwest ocean source of evaporation or shifts in air mass source with changing north atlantic oscillation indices applying five u th thermal ionisation mass spectrometric tims dates to a 17 5 cm isotope profile 18 o

lateglacial to holocene vegetation development in the central rila mountains bulgaria the vegetation history of the central rila mountains for the last 14 000 years was reconstructed by means of pollen analysis and radiocarbon chronology of a core retrieved from lake manastirsko 2

high resolution isotope records of early holocene rapid climate change from two coeval stalagmites of katerloch cave austria abstract two coeval stalagmites from katerloch cave show pronounced intervals of low 18o values around 8 2 9 1 and 10 0 kyr all ages are reported before the year 2000 ad and represent an inorganic u th dated climate archive from the southeast of the european alps a region where only very few well dated climate records exist the o isotope curves providing near annual resolution allow a direct comparison to the greenland ice core records as temperature was the primary factor controlling the o isotopic composition of katerloch speleothems the 8 2 kyr climate anomaly lasted about one century from 8196 to 8100 yr with a maximum amplitude of 1 1 at 8175 yr the event is characterized by a rapid onset and a more gradual demise and u th data as well as annual lamina counting support a rapid climate change towards cooler conditions within 10 20 yr there is no strong evidence that the 8 2 kyr anomaly was superimposed on a pronounced longer term cooling episode nor do the new data support two separate cooling events within the 8 2 kyr event as reported by other studies our record also shows a distinct climate anomaly around 9 1 kyr which lasted 70 110 yr and showed a maximum amplitude of 1 0 i e it had a similar duration and amplitude as the central 8 2 kyr event compared to the 8 2 kyr event the 9 1 kyr anomaly shows a more symmetrical structure but onset and demise still occurred within a few decades only the different progression of the 8 2 asymmetrical and 9 1 kyr anomaly symmetrical suggests a fundamental difference in the trigger and or the response of the climate system moreover both stalagmites show evidence of a climate anomaly around 10 0 kyr which was of comparable magnitude to the two subsequent events using a well constrained modern calibration between air temperature and 18o of precipitation for the study area and cave monitoring data confirming speleothem deposition in katerloch reflecting cave air temperature a maximum cooling by ca 3 c can be inferred at 8 2 and 9 1 kyr which is similar to other estimates e g from lake ammersee north of the alps the o isotopic composition of meteoric precipitation however is a complex tracer of the hydrological cycle and these temperature estimates do not take into account additional effects such as changes in the source area or synoptic shifts apart from that the relative thickness of the seasonally controlled lamina types in the katerloch stalagmites remains rather constant across the intervals comprising the isotopic anomalies i e the stalagmite petrography argues against major shifts in seasonality during the early holocene climate excursions

synchronous holocene climatic oscillations recorded on the swiss plateau and at timberline in the alps eight synchronous pre roman cold phases were found at 9600 9200 8600 8150 7550 6900 6600 6200 5350 4900 4600 4400 3500 3200 and 2600 2350 radiocarbon years bp by reconstructing past climate at two sites on the swiss plateau and at timberline in the alps the cooling events during the early and mid holocene represent temperature values similar to today and apparently the onset of cooling events represents a deviation from today s mean annual temperature of about 1 c and is triggered at a 1000 year periodicity at wallisellen langachermoos 440 m a former oligotrophic lake near zurich the correlation between sum mertime lake levels and the seed production of the amphi atlantic aquatic plantnajas flexilis was used to reconstruct lake levels over a 3000 year period during the first part of the holocene at lake seedorf on the western swiss plateau 609 m the sedimentological palynological and macrofossil record revealed fluctuations of lake levels for the complete holocene from lago basso in the

younger dryas to mid holocene environmental history of the lowlands of nw transylvania romania pollen micro charcoal and total carbon analyses on sediments from the turbuta palaeolake in the transylvanian basin of nw romania reveal younger dryas to mid holocene environmental changes the chronostratigraphy relies on ams 14c measurements on organic matter and u th tims datings of snail shells results indicate the presence of pinus and betula open woodlands with small populations of picea ulmus alnus and salix before 12 000 cal yr bp a fairly abrupt replacement of pinus and betula by ulmus dominated woodlands at ca 11 900 cal yr bp likely represents competition effects of vegetation driven by climate warming at the onset of the holocene by 11 000 cal yr bp the woodlands were increasingly diverse and dense with the expansion of quercus fraxinus and tilia the establishment of corylus and the decline of upland herbaceous and shrubs taxa the marked expansion of quercus accompanied by tilia between 10 500 and 8000 cal yr bp could be the result of low effective moisture associated with both low elevation of the site and with regional change towards a drier climate at 10 000 cal yr bp corylus spread across the region and by 8000 cal yr bp it replaced quercus as a dominant forest constituent with only little representation of picea abies carpinus became established around 5500 cal yr bp but it was only a minor constituent in local woodlands until ca 5000 cal yr bp results from this study also indicate that the woodlands in the lowlands of turbuta were never closed

lake agassiz final drainage event in the northwest north atlantic 1 the 8 2 ka climate event recorded in greenland ice cores is subject of debates with respect to causal linkage with a collapse of the atlantic meridional overturning due to the drainage of the late glacial lake agassiz here we present records from the nw north atlantic down current the flood discharge route showing that the 9 5 8 ka interval was marked by a succession of events the drainage itself corresponds to a twin layer of carbonate rich turbidites deposited within the calibrated 8 35 8 5 ka interval proxies of sea surface and deep current conditions do not indicate significant concomitant changes in the nw north atlantic the dataset however supports the concept that the 8 2 ka climate event may represent one of the manifestations of climate instability during an interval with major changes of land drainage in ne america due to the collapse of the laurentide ice sheet subsequent fast sea level rise and large scale reorganization of the north atlantic thermohaline circulation pattern

small scale moisture availability increase during the 8 2 ka climatic event inferred from biotic proxy records in the south carpathians se romania in this paper we present high resolution early holocene pollen plant macrofossil charcoal diatom biogenic silica and loss on ignition records from a mountain lake in the south carpathians in order to reveal ecosystem response to the 8 2 ka climatic oscillation we found significant changes both in terrestrial vegetation and lake diatom assemblages in the northern slope of the retezat mts between c 8300 and 8000 cal yr bp rapid changes in relative frequencies and pollen accumulation rates of the major deciduous pollen types associated with peaks in microcharcoal accumulation rates suggested that vegetation disturbance mainly took place in the mixed deciduous forest zone where woodland fires partially destroyed the populations of fraxinus excelsior quercus and corylus avellana and facilitated the establishment of carpinus betulus in the forest openings the diatom record furthermore showed the spread of a planktonic diatom species aulacoseira valida at 8150 cal yr bp coincidently with a shor

reconstruction and palaeoclimatic interpretation of mid holocene vegetation and lake level changes at saint jorioz lake annecy french pre alps pollen and sediment analyses were used to reconstruct vegetation and lake level changes over the mid holocene period at saint jorioz lake annecy northern french pre alps episodes of forest clearings point to neolithic cultural activities in the northern french pre alps from c 6500 cal bp in agreement with other pollen and macrofossils records from eastern switzerland and the jura mountains the lake level record shows rises atc 8300 8200 6400 5900 and after 5730 cal bp the rise at c 8300 8200 cal bp shows a tripartition lower water levels developed before 8300 8200 and 6665 cal bp at c 6050 and 5730 cal bp rises at c 8300 8200 6400 5900 and after 5730 cal bp can be related to the 8200 yr event and north atlantic ice rafted debris ird events occurring at c 6200 5800 and 5500 cal bp respectively using a model based on pollen and lake level data the palaeoenvironmental changes reconstructed at saint jorioz were translated into quantitative climate parameters the results suggest that rises in lake level coincided with increasing annual precipitation runoff and available moisture and decreasing mean summer temperature and shortening of the growing season probably as a result of alternate southward northward displacements of the atlantic westerly jet at saint jorioz the period around the 8200 yr event corresponded to a c 2 5degreesc summer temperature cooling and a c 130 mm p e precipitation evaporation increase in agreement with other european and marine palaeoclimate records a c 4degreesc summer temperature cooling and a rise in annual precipitation by c 175 mm are reconstructed at c 5900 cal bp and after 5730 cal bp i e close to the time of the north atlantic ird events dated at 5800 and 5500 cal bp and are to be tested by further investigations a general trend toward temperature cooling and precipitation increase appears over the period documented by the sediment sequence of saint jorioz possibly related to an orbitally induced reduction of summer insolation

age depth relationship and accumulation rates in four sediment sequences from the retezat mts south carpathians romania abstract this study summarizes the results of radiocarbon dating and age depth modelling in four mountain lakes brazi gales bucura and lia in the retezat mountains altogether 69 ams 14 c measurements were performed on these deposits mostly on terrestrial plant macrofossils in several cases plant macrofossils aquatic animal remains cladoceran eggs and bulk sediment were measured from the same depth allowing for the comparison of various sediment components in terms of their dating potential age depth models were developed using both bayesian modelling with the bacon and smooth spline curve fitting with the clam software in this study bayesian models are applied to identify outlier 14 c dates while smooth spline models are used to model sediment accumulation age depth relations as these are more likely to follow natural deposition time changes of lake sediments changes in sediment deposition times dt in relation to catchment size and climate are also studied dt varied considerably in the late glacial lg part of the records the sediment sequence characterised by high deposition rates during the late glacial dt maximum around 100 110 years cm 1 was defined by small catchment size lake brazi 6 ha surface area 0 5 ha in contrast much slower lg sediment deposition in the southern slope lake characterised by large catchment area lake lia 171 ha 20 years cm 1 principally reflecting strong erosion in these catchment areas at times when vegetation cover was scarce holocene was characterised again by variable dt values but only lake gales showed extreme values 62 110 years between 10 900 and 6050 cal yr bp followed by much slower sediment deposition in the last 6000 years av 29 years cm 1 generally sediment deposition times were largely dependent on the stability and vegetation cover of the slope in the case of high altitude deep lakes while lower altitude shallow lakes showed slower sediment deposition time in the early and mid holocene when summer insolation was higher than today this reflects that in these shallow lakes in lake organic production probably increased with summer insolation which was a significant driver in the rate of deposition

late quaternary vegetation change in the tari basin papua new guinea the changes in late quaternary vegetation at two sites in the tari basin central highlands of new guinea are presented haeapugua basin 1650 m altitude and tugupugua basin 2300 m altitude lie within the lower montane forest belt where the climate is characterised by high relative humidity and low seasonality pollen analysis mineral magnetics carbonised particle analysis and dating by radiocarbon and thermoluminescence techniques are employed to reconstruct the vegetation and sediment history the sequences include fragmentary interglacial interstadial records from before 50 000 yr b p and a continuous record from at least 28 000 yr b p to the present the study shows that prior to 21 000 yr b p vegetation in the basin was dominated by fluctuating proportions of tree taxa indicative of a forested environment the montane forest taxon nothofagus is important throughout the record although other tree taxa including castanopsis myrtaceae dacrydium and pandanus attain dominance at different times under the influence of a range of environmental factors the creation of an open environment around 21 000 yr b p is considered to be a consequence of the arrival of humans in the region the late glacial transition between 14 500 and 8500 yr b p is a period of climatic instability with landscape and vegetation adjustments proceeding at different rates across the highlands vegetational adjustments match modern ranges by about 8500 yr b p when swamp forest developed across the sites at the lower altitude site there are indications of anthropogenic forest disturbance associated with swamp forest clearance commencing around 1700 yr b p and intensifying through to the present forest clearance is recorded only after 700 yr b p at the higher site where agriculture was probably only sustainable after the introduction of sweet potato ipomoea batatas

multiproxy evidence of an early holocene 8 2 kyr climate oscillation in central nova scotia canada an early holocene lake sediment record from central nova scotia contains a minerogenic oscillation that is closely correlative with the 8 2 kyr event ca 8200 cal yr bp an event that has not been reported elsewhere in atlantic canada a variety of biological and sedimentological indicators have been examined to characterise autochthonous and allochthonous changes that occurred during this time the minerogenic upper oscillation uo ca 8400 cal yr bp is marked by an increase in the chrysophyte diatom ratio following the oscillation the diatom community reflects a shift to more productive less acidic conditions the pollen record shows no major response to this short lived event lithostratigraphic analyses indicates that the uo is characterised by an increase in clastic content magnetic susceptibility and mean sediment grain size all indicators of changing environmental conditions most likely the result of regional cooling the taylor lake record adds to a growing body of evidence for a widespread hemispheric climate oscillation at 8 2 kyr copyright 2002 john wiley sons ltd

postglacial trends in palynological richness in the northern fennoscandian tree line area and their ecological interpretation the northern fennoscandian tree line area consists of fairly distinct vegetation zones the pollen stratigraphies of two boreal sites and two tundra sites were studied and the palynological data an

the late quaternary vegetational and climatic history of easter island easter island occupies an exceptionally isolated position in the south pacific ocean it is entirely volcanic and is famous for its giant statues late quaternary sediments have been investigated in three craters rano raraku rano aroi and rano kao giving a continuous record over the past 30 ka pollen records indicate that the island was formerly forested palynological and sedimentological evidence suggests a late pleistocene climate slightly cooler and drier than the present deforestation by people occurred mainly between 1200 and 800 yr bp this may have led to an ecological disaster and to the decline of the megalithic civilization the depauperation of the present native flora owes more to human activity than to isolation

the pace of holocene vegetation change testing for synchronous developments mid to high latitude forest ecosystems have undergone several major compositional changes during the holocene the temporal and spatial patterns of these vegetation changes hold potential information to their causes and triggers here we test the hypothesis that the timing of vegetation change was synchronous on a sub continental scale which implies a common trigger or a step like change in climate parameters pollen diagrams from selected european regions were statistically divided into assemblage zones and the temporal pattern of the zone boundaries analysed the results show that the temporal pattern of vegetation change was significantly different from random times of change cluster around 8 2 4 8 3 7 and 1 2 ka while times of higher than average stability were found around 2 1 and 5 1 ka compositional changes linked to the expansion of corylus avellana and alnus glutinosa centre around 10 6 and 9 5 ka respectively a climatic trigger initiating these changes may have occurred 0 5 to 1 ka earlier respectively the synchronous expansion of c avellana and a glutinosa exemplify that dispersal is not necessarily followed by population expansion the partly synchronous partly random expansion of a glutinosa in adjacent european regions exemplifies that sudden synchronous population expansions are not species specific traits but vary regionally

holocene forest dynamics in northwestern romnania pollen analyses and ams radiocarbon measurements were carried out on peat deposits from the former crater lake preluca tiganului located in a mid altitude area of the gutaiului mountains nw romania in order to reconstruct the postglacial vegetation history at the lateglacial holocene transition the open vegetation was replaced by forest suggesting a fast response to climatic warming the rapid expansion of pinus betula and later picea may be due to their existence in the area during the lateglacial at approximately 11 250 cal yr bp the dense forest was composed primarily of ulmus and some picea betula and pinus a small population of ulmus might also have survived in the area during the lateglacial at 10750 cal yr bp quercus tilia and fraxinus followed by corylus at c 10200 cal yr bp expanded significantly in the forest the delay of approximately 550 years in their establishment as compared to the expansion of ulmus was probably due to their immigration from more distant localities

tropical vegetational change in the late pleistocene of new caledonia the south eastern plateau of new caledonia 22 s preserves remnants of a deep regolith of ultramafic soils which is extensively gullied or eroded to form large alluvial fans dated sediments from four closed basins on the plaine des lacs ca 220 m altitude show that organic muds were accumulating prior to 30 000 yr b p over the next 5000 14 000 years limonitic clays infilled two basins as a result of slope instability in their catchment resistant laterite and bog iron surfaces became exposed during the period 30 000 15 000 yr b p by erosional events that seem to have been of greater magnitude than any in the earlier pleistocene two sites lake emeric and lake suprin were chosen for pollen analysis during the phases of organic deposition of these lakes nothofagus forests collapsed several times and were replaced by gymnostoma maquis apparently as a result of fires these pleistocene fires were associated with some inorganic deposition presumably due to the substantial loss of primary forest cover regeneration of forest usually followed after an estimated gap of several centuries thus fire was able to cause forest retreats of the same order of magnitude as that caused by massive fires today the low nutritional status of the soils or lateritic crusts means that as now forest had difficulty reclaiming sites human activity is unknown prior to 3000 years ago so the major erosion is presumed to have had natural causes thus many of the wide ranging changes are the result of natural instability in the sub tropics and some may be much older than hitherto thought climate change towards periods of dry fire prone conditions may have been an underlying cause in the holocene some climatic factor possibly cyclonic storms seems to prevent organic sedimentation switching from cyclone free to cyclone prone at the end of the pleistocene may reflect temperature change in sea surfaces in the region

quantifying the source area of macroscopic charcoal with a particle dispersal model abstract to aid interpreting the source area of charcoal in lake sediment records we compare charcoal deposition from an experimental fire to predictions from a particle dispersal model this provides both a theoretical framework for understanding how lake sediments reflect fire history and a foundation for simulating sediment charcoal records the dispersal model captures the two dimensional patterns in the empirical data predicted vs observed r2 0 67 p