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Pollen Data (pollen + data)

Distribution by Scientific Domains

Humanities and Social Sciences	72%
Earth and Environmental Science	13%
Life Sciences	9%

Kinds of Pollen Data

fossil pollen data

Selected Abstracts

Late Wisconsinan Port Eliza Cave deposits and their implications for human coastal migration, Vancouver Island, Canada

GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 4 2006
M. Al-Suwaidi
Sediments of Port Eliza Cave provide a record of the Last Glacial Maximum (LGM) on Vancouver Island that has important implications for human migration along the debated coastal migration route. Lithofacies changes from nonglacial diamict to glacial laminated silt and clay and till, then a return to nonglacial conditions with oxidized clay, colluvial block beds, and speleothems, along with radiocarbon and U/Th dates, define glacial,nonglacial transitions. Scanning electron microscope studies and clay mineralogy confirm that the laminated fines represent glaciation. Preglacial faunal evidence shows a diverse range from small species, including birds, fish, vole, and marmot, to larger species, such as mountain goat. Pollen data from the same unit show a cold, dry tundra environment with sparse trees. Deglaciation occurred prior to an age of 12.3 ka B.P. based on dated mountain goat bone. These data support the viability of the coastal migration route for humans prior to ,16 ka B.P. and then as early as ,13 ka B.P. © 2006 Wiley Periodicals, Inc. [source]

ORIGINAL ARTICLE: Towards an understanding of the Holocene distribution of Fagus sylvatica L.

JOURNAL OF BIOGEOGRAPHY, Issue 1 2007
Thomas Giesecke
Abstract Aim, Understanding the driving forces and mechanisms of changes in past plant distribution and abundance will help assess the biological consequences of future climate change scenarios. The aim of this paper is to investigate whether modelled patterns of climate parameters 6000 years ago can account for the European distribution of Fagus sylvatica at that time. Consideration is also given to the role of non-climatic parameters as driving forces of the Holocene spread and population expansion of F. sylvatica. Location, Europe. Methods, European distributions were simulated using a physiologically-based bioclimatic model (STASH) driven by three different atmospheric general circulation model (AGCM) outputs for 6000 years ago. Results, The three simulations generally showed F. sylvatica to have potentially been as widespread 6000 years ago as it is today, which gives a profound mismatch with pollen-based reconstructions of the F. sylvatica distribution at that time. The results indicate that drier conditions during the growing season 6000 years ago could have caused a restriction of the range in the south. Poorer growth conditions with consequently reduced competitive ability were modelled for large parts of France. Main conclusions, Consideration of the entire European range of F. sylvatica showed that no single driving force could account for the observed distributional limits 6000 years ago, or the pattern of spread during the Holocene. Climatic factors, particularly drought during the growing season, are the likely major determinants of the potential range. Climatic factors are regionally moderated by competition, disturbance effects and the intrinsically slow rate of population increase of F. sylvatica. Dynamic vegetation modelling is needed to account for potentially important competitive interactions and their relationship with changing climate. We identify uncertainties in the climate and pollen data, as well as the bioclimatic model, which suggest that the current study does not identify whether or not climate determined the distribution of F. sylvatica 6000 years ago. Pollen data are better suited for comparison with relative abundance gradients rather than absolute distributional limits. These uncertainties from a study of the past, where we have information about plant distribution and abundance, argue for extreme caution in making forecasts for the future using equilibrium models. [source]

Persistence of coastal spruce refugia during the Holocene in northern New England, USA, detected by stand-scale pollen stratigraphies

JOURNAL OF ECOLOGY, Issue 2 2002
Molly Schauffler
Summary 1 Pollen data from wet, forested hollows in five spruce (Picea) stands on the eastern coast of Maine, USA, reveal that spruce has been well-established (spruce pollen > 6%) for at least 5000 years at four of the sites (Isle au Haut, Schoodic Peninsula, and Roque Island). Spruce became dominant in the fifth stand (Blackwoods, Mount Desert Island) only in the last 2000 years. This is in contrast to pollen stratigraphies from two inland forest hollows and from inland lakes that indicate a significant region-wide increase in the abundance of spruce only 1000 years ago. 2 All five coastal pollen stratigraphies suggest that conditions along the east coast of Maine became cooler and moister sometime between 6000 and 5000 years ago. Mid-Holocene changes in vegetation and sediment accumulation correspond with the timing of rapid increases in tidal amplitude and diurnal mixing of cold water in the Gulf of Maine, suggestive that these resulted in increased marine effects on the local climate at a time that was generally warmer than present. 3 Two inland forest-hollow stratigraphies do not show evidence of mid-Holocene cooling. Coastal effects therefore persisted for several thousand years despite regional climate changes. 4 The pollen data suggest that refugia along the coast (and probably in isolated sites inland), may have played a critical role in allowing the rapid regional expansion of spruce around 1000 years ago. The steep increases in the abundance of spruce pollen in all forest-hollow and lake pollen stratigraphies in northern New England at that time corroborate other evidence of a region-wide shift to cooler and moister conditions. 5 Pollen stratigraphies from small forested hollows provide a means to examine local vegetation dynamics and interpret those dynamics in the context of regional signals. [source]

Past and present potential distribution of the Iberian Abies species: a phytogeographic approach using fossil pollen data and species distribution models

DIVERSITY AND DISTRIBUTIONS, Issue 2 2010
Francisca Alba-Sánchez
Abstract Aim, Quaternary palaeopalynological records collected throughout the Iberian Peninsula and species distribution models (SDMs) were integrated to gain a better understanding of the historical biogeography of the Iberian Abies species (i.e. Abies pinsapo and Abies alba). We hypothesize that SDMs and Abies palaeorecords are closely correlated, assuming a certain stasis in climatic and topographic ecological niche dimensions. In addition, the modelling results were used to assign the fossil records to A. alba or A. pinsapo, to identify environmental variables affecting their distribution, and to evaluate the ecological segregation between the two taxa. Location, The Iberian Peninsula. Methods, For the estimation of past Abies distributions, a hindcasting process was used. Abies pinsapo and A. alba were modelled individually, first calibrating the model for their current distributions in relation to the present climate, and then projecting it into the past,the last glacial maximum (LGM) and the Middle Holocene periods,in relation to palaeoclimate simulations. The resulting models were compared with Iberian-wide fossil pollen records to detect areas of overlap. Results, The overlap observed between past Abies refugia,inferred from fossil pollen records,and the SDMs helped to construct the Quaternary distribution of the Iberian Abies species. SDMs yielded two well-differentiated potential distributions: A. pinsapo throughout the Baetic mountain Range and A. alba along the Pyrenees and Cantabrian Range. These results propose that the two taxa remained isolated throughout the Quaternary, indicating a significant geographical and ecological segregation. In addition, no significant differences were detected comparing the three projections (present-day, Mid-Holocene and LGM), suggesting a relative climate stasis in the refuge areas during the Quaternary. Main conclusions, Our results confirm that SDM projections can provide a useful complement to palaeoecological studies, offering a less subjective and spatially explicit hypothesis concerning past geographic patterns of Iberian Abies species. The integration of ecological-niche characteristics from known occurrences of Abies species in conjunction with palaeoecological studies could constitute a suitable tool to define appropriate areas in which to focus proactive conservation strategies. [source]

Tectonic and environmental evolution of Quaternary intramontane basins in Southern Apennines (Italy): insights from palaeomagnetic and rock magnetic investigations

GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2010
M. Porreca
SUMMARY Southern Apennines is characterized by active extensional tectonics with NE,SW stretching direction. The seismicity of the region is very well understood and continuously monitored. In contrast, the onset of extensional tectonics is chronologically poorly constrained. The aim of this study is that to give important constraints on the development of extensional regime and the onset of the continental deposition during Quaternary in Southern Apennines. We report the results of palaeomagnetic and rock magnetic analyses from four Quaternary small intramontane basins in the Picentini Mountains (Southern Apennines). The sedimentary sequences are located at different altitudes, from 600 to 1200 m a.s.l., and were deposited in fluvial-lacustrine environments. We sampled 29 sites in clays and lacustrine limestones from Tizzano, Piano del Gaudo and Acerno basins and in red palaeosoils and matrix-supported conglomerates from the Iumaiano basins. In the clay and limestones samples magnetite, titano-magnetite, hematite and iron-sulphide have been recognized as the main magnetic carriers, whereas magnetite and hematite characterize the Iumaiano conglomerates and red soils. Palaeomagnetic results have been integrated with published radiometric data in order to constrain the age of each sedimentary basins. Sites from the Iumaiano basin, which represents the substrate of the Tizzano and Piano del Gaudo basins, show a reverse polarity and therefore have been attributed to the lower Matuyama chron. In contrast, palaeomagnetic data from Tizzano basin show a transition from reversed to normal polarity along the exposed section, which has been interpreted as the Matuyama/Brunhes transition. Sites from Acerno and Piano del Gaudo basins show a normal polarity, which, according to radiometric and pollen data, have been correlated to the Brunhes epoch. On the base of such results we discuss the tectono-stratigraphic evolution of the basins and the role of extensional tectonics in this portion of the Southern Apennine during the Quaternary. [source]

Holocene vegetation and climate change on the Colorado Great Plains, USA, and the invasion of Colorado piñon (Pinus edulis)

JOURNAL OF BIOGEOGRAPHY, Issue 12 2009
R. Scott Anderson
Abstract Aim, To reconstruct the last c. 7000 years of vegetation and climate change in an unusual region of modern Great Plains grassland and scarp woodland in south-east Colorado (USA), and to determine the late Holocene biogeography of Colorado piñon (Pinus edulis) at its easternmost extent, using a series of radiocarbon-dated packrat (Neotoma sp.) middens. Location, The West Carrizo Canyon drains the Chaquaqua Plateau, a plateau that projects into the western extent of the southern Great Plains grasslands in south-eastern Colorado, USA. Elevations of the study sites are 1448 to 1525 m a.s.l. Today the plateau is mostly Juniperus scopulorum,P. edulis woodland. Methods, Plant macrofossils and pollen assemblages were analysed from 11 14C-dated packrat middens. Ages ranged from 5990 yr bp (6839 cal. yr bp) to 280 yr bp (485 cal. yr bp). Results, The results presented here provide information on the establishment and expansion of Juniperus,P. edulis woodland at its eastern limits. The analysis of both plant macrofossils and pollen from the 11 middens documents changes in plant communities over the last 7000 years, and the establishment of P. edulis at its easternmost limit. Though very minor amounts of P. edulis pollen occur as early as the middle Holocene, plant macrofossils were only recovered in middens dating after c. 480 cal. yr bp. Main conclusions, Originally, midden research suggested a late glacial refuge to the north-east of the Carrizo Canyon site, and a middle Holocene expansion of P. edulis. Results reported here are consistent with a late Holocene expansion, here at its eastern limits, but noted elsewhere at its northern and north-eastern limits. In general, this late Holocene expansion is consistent with pollen data from sediments in Colorado and New Mexico, and suggests that P. edulis is still expanding its range at its present extremes. This has implications for further extension of its range due to changing climatic conditions in the future. [source]

Modern pollen,vegetation relationships in subarctic southern Greenland and the interpretation of fossil pollen data from the Norse landnám

JOURNAL OF BIOGEOGRAPHY, Issue 3 2007
J. Edward Schofield
Abstract Aim, The objective of this paper is to explore the relationships that exist between vegetation and modern pollen rain in the open, largely treeless landscape of subarctic Greenland. The implications of these results for the interpretation of fossil pollen assemblages from the time of the Norse landnám are then examined. Location, The study area is the sheep farming district of Qassiarsuk in the subarctic, subcontinental vegetational and climatic zone of southern Greenland (61° N, 45° W). Between c.ad 1000,1500 this region was contained within the Norse Eastern Settlement. Methods, Detrended Correspondence Analysis (DCA) of harmonized plant,pollen data sets is used to compare plant cover in 64 vegetation quadrats with pollen assemblages obtained from moss polsters at matching locations. Presence/absence data are also used to calculate indices of association, over- and under-representation for pollen types. Results, Good correspondence between paired vegetation,pollen samples occurs in many cases, particularly in locations where Salix glauca,Betula glandulosa dwarf shrub heath is dominant, and across herbaceous field boundaries and meadows. Pollen samples are found to be poor at reflecting actual ground cover where ericales or Juniperus communis are the locally dominant shrubs. Dominant or ubiquitous taxa within this landscape (Betula, Salix and Poaceae) are found to be over-represented in pollen assemblages, as are several of the ,weeds' generally accepted as introduced by the Norse settlers. Main conclusions, Due to their over-representation in the pollen rain, many of the Norse apophytes and introductions (e.g. Rumex acetosa and R. acetosella) traditionally used to infer human activity in Greenland should be particularly sensitive indicators for landnám, allowing early detection of Norse activity in fossil assemblages. Pteridophyte spores are found to be disassociated with the ground cover of ferns and clubmosses, but are over-represented in pollen assemblages, indicating extra-local or regional sources and long residence times in soil/sediment profiles for these microfossils. A pollen record for Hordeum -type registered in close proximity to a field containing barley suggests that summer temperatures under the current climatic regime are, at least on occasion, sufficient to allow flowering. [source]

Pollen,plant,climate relationships in sub-Saharan Africa

JOURNAL OF BIOGEOGRAPHY, Issue 3 2007
Julie Watrin
Abstract Aim, To demonstrate that incorporating the bioclimatic range of possible contributor plants leads to improved accuracy in interpreting the palaeoclimatic record of taxonomically complex pollen types. Location, North Tropical Africa. Methods, The geographical ranges of selected African plants were extracted from the literature and geo-referenced. These plant ranges were compared with the pollen percentages obtained from a network of surface sediments. Climate-response surfaces were graphed for each pollen taxon and each corresponding plant species. Results, Several patterns can be identified, including taxa for which the pollen and plant distributions coincide, and others where the range limits diverge. Some pollen types display a reduced climate range compared with that of the corresponding plant species, due to low pollen production and/or dispersal. For other taxa, corresponding to high pollen producers such as pioneer taxa, pollen types display a larger climatic envelope than that of the corresponding plants. The number of species contained in a pollen taxon is an important factor, as the botanical species included in a taxon may have different geographical and climate distributions. Main conclusions, The comparison between pollen and plant distributions is an essential step towards more precise vegetation and climate reconstructions in Africa, as it identifies taxa that have a high correspondence between pollen and plant distribution patterns. Our method is a useful tool to reassess biome reconstructions in Africa and to characterize accurately the vegetation and climate conditions at a regional scale, from pollen data. [source]

ORIGINAL ARTICLE: Towards an understanding of the Holocene distribution of Fagus sylvatica L.

Pollen-based reconstructions of biome distributions for Australia, Southeast Asia and the Pacific (SEAPAC region) at 0, 6000 and 18,000 14C yr BP

JOURNAL OF BIOGEOGRAPHY, Issue 9 2004
Elizabeth J. Pickett
Abstract Aim, This paper documents reconstructions of the vegetation patterns in Australia, Southeast Asia and the Pacific (SEAPAC region) in the mid-Holocene and at the last glacial maximum (LGM). Methods, Vegetation patterns were reconstructed from pollen data using an objective biomization scheme based on plant functional types. The biomization scheme was first tested using 535 modern pollen samples from 377 sites, and then applied unchanged to fossil pollen samples dating to 6000 ± 500 or 18,000 ± 1000 14C yr bp. Results, 1. Tests using surface pollen sample sites showed that the biomization scheme is capable of reproducing the modern broad-scale patterns of vegetation distribution. The north,south gradient in temperature, reflected in transitions from cool evergreen needleleaf forest in the extreme south through temperate rain forest or wet sclerophyll forest (WSFW) and into tropical forests, is well reconstructed. The transitions from xerophytic through sclerophyll woodlands and open forests to closed-canopy forests, which reflect the gradient in plant available moisture from the continental interior towards the coast, are reconstructed with less geographical precision but nevertheless the broad-scale pattern emerges. 2. Differences between the modern and mid-Holocene vegetation patterns in mainland Australia are comparatively small and reflect changes in moisture availability rather than temperature. In south-eastern Australia some sites show a shift towards more moisture-stressed vegetation in the mid-Holocene with xerophytic woods/scrub and temperate sclerophyll woodland and shrubland at sites characterized today by WSFW or warm-temperate rain forest (WTRF). However, sites in the Snowy Mountains, on the Southern Tablelands and east of the Great Dividing Range have more moisture-demanding vegetation in the mid-Holocene than today. South-western Australia was slightly drier than today. The single site in north-western Australia also shows conditions drier than today in the mid-Holocene. Changes in the tropics are also comparatively small, but the presence of WTRF and tropical deciduous broadleaf forest and woodland in the mid-Holocene, in sites occupied today by cool-temperate rain forest, indicate warmer conditions. 3. Expansion of xerophytic vegetation in the south and tropical deciduous broadleaf forest and woodland in the north indicate drier conditions across mainland Australia at the LGM. None of these changes are informative about the degree of cooling. However the evidence from the tropics, showing lowering of the treeline and forest belts, indicates that conditions were between 1 and 9 °C (depending on elevation) colder. The encroachment of tropical deciduous broadleaf forest and woodland into lowland evergreen broadleaf forest implies greater aridity. Main conclusions, This study provides the first continental-scale reconstruction of mid-Holocene and LGM vegetation patterns from Australia, Southeast Asia and the Pacific (SEAPAC region) using an objective biomization scheme. These data will provide a benchmark for evaluation of palaeoclimate simulations within the framework of the Palaeoclimate Modelling Intercomparison Project. [source]

Pollen-based biomes for Beringia 18,000, 6000 and 0 14C yr bp,

JOURNAL OF BIOGEOGRAPHY, Issue 3 2000
M. E. Edwards
Abstract The objective biomization method developed by Prentice et al. (1996) for Europe was extended using modern pollen samples from Beringia and then applied to fossil pollen data to reconstruct palaeovegetation patterns at 6000 and 18,000 14C yr bp. The predicted modern distribution of tundra, taiga and cool conifer forests in Alaska and north-western Canada generally corresponds well to actual vegetation patterns, although sites in regions characterized today by a mosaic of forest and tundra vegetation tend to be preferentially assigned to tundra. Siberian larch forests are delimited less well, probably due to the extreme under-representation of Larix in pollen spectra. The biome distribution across Beringia at 6000 14C yr bp was broadly similar to today, with little change in the northern forest limit, except for a possible northward advance in the Mackenzie delta region. The western forest limit in Alaska was probably east of its modern position. At 18,000 14C yr bp the whole of Beringia was covered by tundra. However, the importance of the various plant functional types varied from site to site, supporting the idea that the vegetation cover was a mosaic of different tundra types. [source]

Identification of arid phases during the last 50,cal. ka BP from the Fuentillejo maar-lacustrine record (Campo de Calatrava Volcanic Field, Spain),

JOURNAL OF QUATERNARY SCIENCE, Issue 7 2010
Juana Vegas
Abstract Geochemical (element analysis, molecular analysis of organic compounds), physical, palynological, mineralogical and sedimentary facies analysis were performed to characterise the sedimentary record in Fuentillejo maar-lake in the Central Spanish Volcanic Field of Campo de Calatrava, in order to reconstruct the palaeoenvironmental and palaeoclimatic processes which controlled vegetation patterns and deposition of different sedimentary facies. The upper 20,m of core FUENT-1 show variations in clastic input, water chemistry, vegetation and organic fraction sources in the lake throughout the Late Pleistocene and Holocene. The temporal framework provided by 14C accelerator mass spectrometry dating allows assigning the sequence to the last 50,cal. ka BP. Arid phases identified in the FUENT-1 sequence are correlated to Heinrich events (HE) and to stadials of the Dansgaard/Oeschger (D/O) cycles. Siliciclastic facies with high magnetic susceptibility values, high Juniperus pollen content, a low Paq index (aquatic macrophysics proxy index), a decrease in the relative percentage of the n -C27 and an increase in the n -C31 alkanes are indicative of arid and colder climatic events related to HE 2, HE 1 and the Younger Dryas (YD). Similar short cold and arid phases during the Holocene were identified at 9.2,8.6, 7.5,7 and 5.5,5,cal. ka BP. In dolomite,mud facies, the pollen data show an increase in the herbs component, mainly , Chenopodiaceae, Artemisia and Ephedra , steppe taxa; a low Paq index, a decrease in the relative percentage of the n -C27 alkane and an increase in the n -C31 alkane are also observed. This facies was probably the result of lower lake levels and more saline,alkaline conditions, which can be interpreted as linked to arid,warm periods. These warm and arid phases were more frequent during Marine Isotope Stage (MIS) 3 and the interstadials of MIS 2. HE 4, HE 2, HE 1 and the YD in core FUENT-1 were immediately followed by increases of warm steppe pollen assemblages that document rapid warming similar to the D/O cycles but do not imply increasing humidity in the area. Fuentillejo hydrology is controlled by changes in the atmospheric and oceanic systems that operated on the North Atlantic region at millennial scale during the last 50,cal. ka BP. Copyright © 2009 John Wiley & Sons, Ltd. [source]

A high-resolution pollen and geochemical analysis of late Holocene human impact and vegetation history in southern Cumbria, England,

JOURNAL OF QUATERNARY SCIENCE, Issue 3 2009
Paul M. V. Coombes
Abstract The historic era, which in Cumbria begins with the Roman invasion of AD 71, is a frequently neglected period in palaeoecological research, but its study can bring benefits in improving knowledge of landscape history and in understanding the significance and limitations of palaeoecological records. Pollen and geochemical data are presented for late Holocene records from Deer Dyke and Hulleter Mosses in southern Cumbria. The records show initially low levels of anthropogenic impact, followed by a phase of forest clearance and mixed agriculture from the 7th to 11th centuries AD. The timing of these clearances suggests that they were initially Anglo-Saxon in origin, rather than Norse. Further clearances in the 16th century AD are interpreted as a response to monastic dissolution and late Tudor population pressures; the landscapes reached their contemporary form following extensive clearances in the 17th century AD. Silicon and titanium concentrations at Deer Dyke Moss were used to reconstruct past levels of atmospheric dust loading, which is broadly related to soil erosion. Geochemical influx was found to peak during periods of landscape transition rather than from established land use. This relationship with pollen data is thought to reflect the predominantly low levels of anthropogenic impact in the region, which changes as substantial woodland clearances during the 16th century AD and continuous land use pressure since then have greatly increased the supply of airborne dust. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Ages and inferred causes of Late Pleistocene glaciations on Mauna Kea, Hawai'i,

JOURNAL OF QUATERNARY SCIENCE, Issue 6-7 2008
Jeffrey S. Pigati
Abstract Glacial landforms on Mauna Kea, Hawai'i, show that the summit area of the volcano was covered intermittently by ice caps during the Late Pleistocene. Cosmogenic 36Cl dating of terminal moraines and other glacial landforms indicates that the last two ice caps, called Older Makanaka and Younger Makanaka, retreated from their maximum positions approximately 23,ka and 13,ka, respectively. The margins and equilibrium line altitudes of these ice caps on the remote, tropical Pacific island were nearly identical, which would seem to imply the same mechanism for ice growth. But modelling of glacier mass balance, combined with palaeotemperature proxy data from the subtropical North Pacific, suggests that the causes of the two glacial expansions may have been different. Older Makanaka air atop Mauna Kea was likely wetter than today and cold, whereas Younger Makanaka times were slightly warmer but significantly wetter than the previous glaciation. The modelled increase in precipitation rates atop Mauna Kea during the Late Pleistocene is consistent with that near sea level inferred from pollen data, which suggests that the additional precipitation was due to more frequent and/or intense tropical storms associated with eastward-moving cold fronts. These conditions were similar to modern La Niña (weak ENSO) conditions, but persisted for millennia rather than years. Increased precipitation rates and the resulting steeper temperature lapse rates created glacial conditions atop Mauna Kea in the absence of sufficient cooling at sea level, suggesting that if similar correlations existed elsewhere in the tropics, the precipitation-dependent lapse rates could reconcile the apparent difference between glacial-time cooling of the tropics at low and high altitudes. Copyright © 2008 John Wiley & Sons, Ltd. [source]

The importance of local-scale openness within regions dominated by closed woodland,

JOURNAL OF QUATERNARY SCIENCE, Issue 6 2007
Ralph Fyfe
Abstract New and existing pollen data from Wales, UK, are used to assess the level of landscape openness at the regional and local scale. At the regional scale, the existing pollen data support the high-forest model of vegetation structure by 6000 cal. yr. BC prior to any palynological signal for anthropogenic impact in the region. New data from two sites in southwest Wales follow the general regional pattern of early to middle Holocene vegetation succession, but are striking owing to maintenance of high non-arboreal pollen percentages (NAPs) throughout the mid-Holocene. It is argued that these NAPs indicate that a significant degree of openness can be found at the local level (and beyond the confines of the peat-forming site) within regions characterised by closed woodland. It is possible that woodland development in these areas may have been suppressed by reduced drainage, although the role of grazing animals in maintenance of clearings cannot be assessed. Implications for this local degree of openness are discussed, in particular the significance of vegetation heterogeneity at the local scale for the construction of place or locale for prehistoric communities. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Holocene climate change in the eastern Mediterranean region: a comparison of stable isotope and pollen data from Lake Gölhisar, southwest Turkey,

JOURNAL OF QUATERNARY SCIENCE, Issue 4 2007
Warren J. Eastwood
Abstract Stable isotope and pollen data from Gölhisar Gölü, a small intramontane lake located in southwest Turkey, provide complementary records of Holocene climate change. Modern oxygen and hydrogen isotope water data are used as a means of comparing present-day isotope composition of the lake water to the past oxygen isotope composition of the lake water as calculated from 18O/16O ratios in calcite precipitated in the summer months. Despite the lake system being chemically dilute, the modern isotope data clearly establish that the lake water is evaporated in relation to its spring input, suggesting that the palaeo data can be interpreted primarily in terms of changing precipitation/evaporation ratios. ,18O and ,13C values from authigenic calcite through the Holocene show predominantly negative values indicating climatic conditions wetter than today. Particularly notable are low (depleted) isotope values during the earliest Holocene (ca. 10,600,8800 cal. yr. BP), a period for which pollen data imply drier conditions than at present. This divergence between pollen-inferred and stable isotope palaeoclimate data is found in other east Mediterranean lake sediment records, and suggests that vegetation may have taken several millennia to reach climatic equilibrium at the start of the Holocene. Isotopic fluctuations during the early-to-mid Holocene (8800,5100 cal. yr. BP) suggest oscillations between aridity and humidity. Higher ,18O and ,13C values for the second half of the Holocene indicate generally drier conditions than during the period before ca.5100 cal. yr BP although there is some evidence for increased humidity coinciding with pollen evidence for increasing human impact and intensification of agriculture, notably during the so-called Bey,ehir Occupation Phase (Classical and early Byzantine periods). The modern trend towards aridity started about 1300 yr ago. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Climatic oscillations in central Italy during the Last Glacial,Holocene transition: the record from Lake Accesa,

JOURNAL OF QUATERNARY SCIENCE, Issue 4 2006
Michel Magny
Abstract This paper presents an event stratigraphy based on data documenting the history of vegetation cover, lake-level changes and fire frequency, as well as volcanic eruptions, over the Last Glacial,early Holocene transition from a terrestrial sediment sequence recovered at Lake Accesa in Tuscany (north-central Italy). On the basis of an age,depth model inferred from 13 radiocarbon dates and six tephra horizons, the Oldest Dryas,Bølling warming event was dated to ca. 14,560,cal.,yr,BP and the Younger Dryas event to ca. 12,700,11,650,cal.,yr,BP. Four sub-millennial scale cooling phases were recognised from pollen data at ca. 14,300,14,200, 13,900,13,700, 13,400,13,100 and 11,350,11,150,cal.,yr,BP. The last three may be Mediterranean equivalents to the Older Dryas (GI-1d), Intra-Allerød (GI-1b) and Preboreal Oscillation (PBO) cooling events defined from the GRIP ice-core and indicate strong climatic linkages between the North Atlantic and Mediterranean areas during the last Termination. The first may correspond to Intra-Bølling cold oscillations registered by various palaeoclimatic records in the North Atlantic region. The lake-level record shows that the sub-millennial scale climatic oscillations which punctuated the last deglaciation were associated in central Italy with different successive patterns of hydrological changes from the Bølling warming to the 8.2,ka cold reversal. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Pollen-based biome reconstructions for Colombia at 3000, 6000, 9000, 12 000, 15 000 and 18 000 14C yr ago: Late Quaternary tropical vegetation dynamics

JOURNAL OF QUATERNARY SCIENCE, Issue 2 2002
Robert Marchant
Abstract Colombian biomes are reconstructed at 45 sites from the modern period extending to the Last Glacial Maximum (LGM). The basis for our reconstruction is pollen data assigned to plant functional types and biomes at six 3000-yr intervals. A reconstruction of modern biomes is used to check the treatment of the modern pollen data set against a map of potential vegetation. This allows the biomes reconstructed at past periods to be assessed relative to the modern situation. This process also provides a check on the a priori assignment of pollen taxa to plant functional types and biomes. For the majority of the sites, the pollen data accurately reflect the potential vegetation, even though much of the original vegetation has been transformed by agricultural practices. At 18 000 14C yr BP, a generally cool and dry environment is reflected in biome, assignments of cold mixed forests, cool evergreen forests and cool grassland,shrub; the latter extending to lower altitudes than presently recorded. This signal is strongly recorded at 15 000 and 12 000 14C yr BP, the vegetation at these times also reflecting a relatively cool and dry environment. At 9000 14C yr BP there is a shift to biomes thought to result from slightly cooler environmental conditions. This trend is reversed by 6000 14C yr BP; most sites, within a range of different environmental settings, recording a shift to more xeric biome types. There is an expansion of steppe and cool mixed-forest biomes, replacing tropical dry forest and cool grassland,shrub biomes, respectively. These changes in biome assignments from the modern situation can be interpreted as a biotic response to mid-Holocene climatic aridity. At 3000 14C yr BP the shift is mainly to biomes characteristic of slightly more mesic environmental conditions. There are a number of sites that do not change biome assignment relative to the modern reconstruction, although the affinities that these sites have to a specific biome do change. These ,anomalies' are interpreted on a site-by-site basis. Spatially constant, but differential response of the vegetation to climatic shifts are related to changes in moisture sources and the importance of edaphic controls on the vegetation. The Late Quaternary reconstruction of large-scale vegetation dynamics in Colombia allows an understanding of the environmental controls on these to be developed. In particular, shifts in the character of the main climatic systems that influence Colombian vegetation are described. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Detecting Holocene movements of the woodland,steppe ecotone in northern China using discriminant analysis

JOURNAL OF QUATERNARY SCIENCE, Issue 3 2001
Hongyan Liu
Abstract Discriminant functions link vegetation zones and surface pollen along the woodland,steppe ecotone in northern China. These links were utilised to reconstruct palaeovegetation using fossil pollen data from four lake sediment sites within the ecotone. Holocene movements of the vegetation zones were derived from the above results and were interpreted as the results of climatic, topographic and edaphic factors. This study shows that climatic change was the driving factor for ecotonal movement, but that the positions of vegetational zones were nevertheless controlled by topographical and edaphic conditions, and consequently boundaries between different vegetational zones responded individualistically. Copyright © 2001 John Wiley & Sons, Ltd. [source]

Colour characteristics of honeys as influenced by pollen grain content: a multivariate study

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 4 2004
Anass Terrab
Abstract A chromatic analysis by tristimulus colorimetry and a pollen analysis (pollen grains contained in each honey sample, considering their volume and geometrical shape) were carried out on 33 Eucalyptus unifloral honeys; the colour of the pollen grains was also considered. Multiple linear regression (MLR) and partial least squares regression (PLSR) were used to establish equations relating the chromatic variables to the pollen data, ie number and morphology of the pollen grains, thus allowing the prediction of the ultimate colour from the botanical characteristics. The results obtained show that lightness (L*) is significantly (p < 0.05) related to the pollen type Olea europaea; on the other hand, the variable that better relates to the chroma is the Zea mays pollen type. Copyright © 2004 Society of Chemical Industry [source]

Vegetation and climate history in the Westeifel Volcanic Field (Germany) during the past 11 000 years based on annually laminated lacustrine maar sediments

BOREAS, Issue 4 2009
THOMAS LITT
Lakes Holzmaar and Meerfelder Maar are located in the Westeifel Volcanic Field less than 10 km apart. Both maar lakes are well known for their annually laminated (varved) sediments covering the past 15 000 years. Here, we focus on reconstructing the history of Holocene vegetation, human impact and climate using high-resolution pollen data. Detailed correlation between the two records using palynologically defined tie-points provides for the first time a test of the precision of the individual varve chronologies. The high-resolution pollen records of both Holzmaar and Meerfelder Maar show continuous natural successions of vegetation during the early and mid-Holocene controlled by the development of soil, climate, immigration and competitive expansion of thermophilous tree species. From 6500 varve yr BP onwards, human impact became an increasingly more important factor. Given the high chronological precision of both records, regional similarities, but also local differences of anthropogenically influenced vegetation changes, can be recognized. The reconstructed July temperature between 8500 and 5000 varve yr BP is around 1 °C higher than today, most likely in response to higher summer insolation related to orbital forcing. High variability of reconstructed July and January temperatures as well as annual precipitation around 5000 varve yr BP is a prominent climatic signal. This is consistent with other records in several areas of Europe which also identify this period as climatically highly variable. [source]