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Hilary H Birks - One of the best experts on this subject based on the ideXlab platform.
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plant Macrofossil introduction
Encyclopedia of Quaternary Science (Second Edition), 2013Co-Authors: Hilary H BirksAbstract:This article provides an introduction to plant Macrofossil analysis and an overview of the articles in this subsection. A plant Macrofossil can be defined as a plant fossil that is visible to the naked eye and that can be manipulated by hand. There are short accounts of where Macrofossils can be found, how they are sampled and analyzed, their taphonomy, and how they represent the vegetation that produced them. Macrofossil types of particular paleoecological interest are illustrated by photographs. Examples are discussed of the contributions made by Macrofossil studies to aspects of Quaternary paleoecology, such as vegetation history and situations where they greatly enhance interpretations from pollen analysis. Their application in accelerator mass spectrometry radiocarbon dating is summarized, including high-resolution chronologies, avoidance and correction of lake and marine reservoir ages, and dating of tephras as time markers, as well as their use in reconstructing past atmospheric carbon dioxide (CO2) concentrations from fossil leaves.
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plant Macrofossil introduction
Encyclopedia of Quaternary Science, 2007Co-Authors: Hilary H BirksAbstract:This article provides an introduction to plant Macrofossil analysis and an overview of the articles in this subsection. A plant Macrofossil can be defined as a plant fossil that is visible to the naked eye and that can be manipulated by hand. There are short accounts of where Macrofossils can be found, how they are sampled and analyzed, their taphonomy, and how they represent the vegetation that produced them. Macrofossil types of particular paleoecological interest are illustrated by photographs. Examples are discussed of the contributions made by Macrofossil studies to aspects of Quaternary paleoecology, such as vegetation history and situations where they greatly enhance interpretations from pollen analysis. Their application in accelerator mass spectrometry (AMS) radiocarbon dating is summarized, including high-resolution chronologies, avoidance and correction of lake and marine reservoir ages, and dating of tephras as time markers, and also their use in reconstructing past atmospheric carbon dioxide (CO2) concentrations from fossil leaves.
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Holocene forest development along the Setesdal valley, southern Norway, reconstructed from Macrofossil and pollen evidence
Vegetation History and Archaeobotany, 2006Co-Authors: Wenche Eide, Hilary H Birks, Nancy H. Bigelow, Sylvia M. Peglar, H. John B. BirksAbstract:The Setesdal valley in South Norway runs north to south for 200 km, from alpine vegetation at 1200 m, passing the tree-line at around 1000 m, through Boreal forests, to Nemoral forest at sea level. The Holocene vegetation history and its altitudinal differentiation were reconstructed using pollen percentages and influx and plant Macrofossil concentration records from four lakes along an altitudinal transect. During the early Holocene (c. 10500–8000 cal b.p. ) Betula pubescens, Pinus sylvestris , Alnus , and Corylus expanded in the lowlands. Only Pinus and B. pubescens reached 1000 m asl (Lille Kjelavatn). Only B. pubescens reached Holebudalen (1144 m asl) at about the same time as it arrived in the lowlands. Between c. 8000–3000 cal b.p. mixed deciduous forest developed around Dalane (40 m asl) and to a lesser extent around Grostjørna (180 m asl), birch woodland with pine surrounded Lille Kjelavatn and birch woodland occurred at Holebudalen. From c. 3000 cal b.p. to present, the vegetation at Dalane hardly changed except for slight human impact and the immigration of Picea abies . At Grostjørna Pinus expanded. At Lille Kjelavatn Pinus disappeared and Betula became sparse as at the tree-line today. Betula retreated from Holebudalen thus leaving it above the tree-line in low-alpine vegetation. The strengths and weaknesses of pollen and plant Macrofossil data were assessed for forest reconstructions. Where local pollen production is low, as near the tree-line, percentages of long-distance tree pollen can be misleadingly high. Pollen influxes of Betula and Pinus were much smaller near their altitudinal limits than at lower altitudes, although their Macrofossils were equally abundant. The limited dispersal capacity of Macrofossils documents the local presence of species and the character of the local vegetation, although Macrofossils of some tree taxa are rarely found. Pollen and plant Macrofossil evidence complement each other to provide a more complete reconstruction of Holocene tree-limits and tree-lines and hence climate changes, than either form of evidence alone.
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full glacial upland tundra vegetation preserved under tephra in the beringia national park seward peninsula alaska
Quaternary Science Reviews, 2001Co-Authors: Victoria G Goetcheus, Hilary H BirksAbstract:The nature of the full-glacial vegetation of Beringia has been the subject of a great deal of investigation and debate. Here we present a reconstruction of an intact example of the full-glacial upland vegetation of part of the northern Seward Peninsula at one point in time. The area was blanketed by more than 1 m of tephra ca. 18,000 14C BP (ca. 21,500 cal. BP), and the former land-surface was preserved in the permafrost. The discovery of the land-surface provides a unique opportunity to study a fossil ecosystem preserved in situ. Macrofossils were used to reconstruct the vegetation growing at several sites on the buried land-surface. The Macrofossil assemblages indicate a vegetation characterized by graminoids and forbs, with the occasional occurrence of Salix arctica. The vegetation was dominated by Kobresia myosuroides, other sedges (Carex), and grasses, with a "ne-scale mosaic related to snow accumulation and moisture availability. Overall, the vegetation was a closed, dry, herb-rich tundra-grassland with a continuous moss layer, growing on calcareous soil that was continuously supplied with loess. Nutrient renewal by loess deposition was probably responsible for the relatively fertile vegetation, and the occurrence of a continuous mat of acrocarpous mosses. Good physiognomic analogues can be suggested, but no exact modern vegetational analogues have been found, probably because the full-glacial environment and climate with loess deposition do not occur today. ( 2000 Elsevier Science Ltd. All rights reserved.
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Distinguishing fossil Betula nana and B. pubescens using their wingless fruits: implications for the late-glacial vegetational history of western Norway
Vegetation History and Archaeobotany, 1996Co-Authors: Marieke Dinter, Hilary H BirksAbstract:Principal components analysis of 7 size and shape variables measured on 154 modern fruit bodies of Betula species and hybrids shows that B. pubescens and B. nana can be distinguished from each other on the basis of their fruit bodies, and that B. pubescens ssp. tortuosa and hybrids either fall within the range of B. pubescens or have an intermediate position on PCA axes 1 and 2. Passive positioning on the modern PCA axes of fossil fruit bodies from late-glacial sediments at Eigebakken, south-west Norway, shows that only B. nana was locally present in the Allerød. This contradicts earlier inferences from pollen analyses alone of birch woodland development in the Allerød in south-west Norway. There is no Macrofossil evidence for tree-birches in the Allerød near Eigebakken. The relatively large amounts of Betula pollen, including B. pubescens , at Eigebakken are thus probably derived by long-distance transport from tree-birches in Denmark, south Sweden, and Britain, whose presence is proved there by Macrofossils. Consequently, earlier estimates of mean July temperature during the Allerød in southwestern Norway should be reduced to around 7.5–10°C. In contrast, the PCA shows that fruit bodies from Holocene sediments at Eigebakken and at Kråkenes, western Norway, are mostly derived from B. pubescens . Birch trees were able to spread quickly and effectively across Norway in the early Holocene.
Gina E Hannon - One of the best experts on this subject based on the ideXlab platform.
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dynamic early holocene vegetation development on the faroe islands inferred from high resolution plant Macrofossil and pollen data
Quaternary Research, 2010Co-Authors: Gina E Hannon, Mats Rundgren, Catherine JessenAbstract:Vegetation dynamics during the earliest part of the Holocene (11,250-10,250 cal yr BP) have been reconstructed from a lacustrine sequence on Sandoy, the Faroe Islands, using detailed plant Macrofossil and pollen evidence. The plant Macrofossils suggest the initial vegetation was sparse herb and shrub tundra, with Salix herbacea and open-ground species, followed by the development of a denser and more species-rich arctic heathland after 11,150 cal yr BP. Despite high pollen values for Betula nana, Macrofossils are rare. The bulk of the Macrofossils recorded are S. herbacea and Empetrum leaves with numerous herb taxa and an abundance of Racomitrium moss. Conditions start to change around 10,800 cal yr BP, with increased catchment erosion and sediment delivery to the lake from ca. 10,600 cal yr BP, and a transition to alternating Cyperaceae and Poaceae communities between ca. 10,450 and 10,250 cal yr BP. This vegetation change, which has been recorded throughout the Faroes, has previously been interpreted as a retrogressive shift from woody shrubs to a herbaceous community. The detailed plant Macrofossil data show the shift is the replacement of an Empetrum arctic heathland by grassland and moist sedge communities. These taxa dominate the modern landscape. (C) 2009 University of Washington. Published by Elsevier Inc. All rights reserved. (Less)
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The plant-Macrofossil record of past lake-level changes
Journal of Paleolimnology, 1997Co-Authors: Gina E Hannon, Marie-josé GaillardAbstract:Plant-Macrofossil analysis is one of the most useful biostratigraphical methods for the reconstruction of former lake-level changes. The distribution of submerged, floating-leaved and emergent lake-shore vegetation is mainly dependant on water depth, but water chemistry and nutrient status must also be taken into account when interpreting water-level changes. Lake-level studies should be based on the investigation of several littoral cores along a transect perpendicular to the lake-shore. Multiple cores are essential for separating genuine lake-level changes from other processes influencing the plant-Macrofossil record. Physical analyses of sediment stratigraphy provide important additional information to the plant-fossil record, because natural infilling processes and erosion from the catchment must be distinguished from climatic events causing a change in the water level. Here we review several important concepts, including suitability of lakes for lake-level study, the degree of detail required in the analysis, and Macrofossil records of lake-level changes, and illustrate those concepts by examples from southern Sweden and Minnesota. We discuss how to reconcile alternative hypotheses for the stratigraphic changes seen in the Macrofossil assemblages.
Brigitta Ammann - One of the best experts on this subject based on the ideXlab platform.
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early holocene afforestation processes in the lower subalpine belt of the central swiss alps as inferred from Macrofossil and pollen records
The Holocene, 2005Co-Authors: Erika Gobet, Willy Tinner, Christian Bigler, Peter A Hochuli, Brigitta AmmannAbstract:To reconstruct the vegetation history of the Upper Engadine, continuous sediment cores covering the past 11 800 years from Lej da Champfer and Lej da San Murezzan (Upper Engadine Valley, c. 1800 m a.s.l., southeastern Switzerland) have been analysed for pollen and plant Macrofossils. The chronologies of the cores are based on 16 and 22 radiocarbon dates, respectively. The palaeobotanical records of both lakes are in agreement for the Holocene, but remarkable differences exist between the sites during the period 11 100 to 10 500 cal. BP, when Lej da Champfer was affected by re-sedimentation processes. Macrofossil data suggest that Holocene afforestation began at around 11400 cal. BP. A climatic deterioration, the Preboreal Oscillation, stopped and subsequently delayed the establishment of trees until c. 11000 cal. BP, when first Betula, then Pinus sylvestrislmugo, then Larix 300 years later, and finally Pinus cembra expanded within the lake catchment. Treeline was at c. 1500 m during the Younger Dryas (12 542- 11 550 cal. BP) in the Central Alps. Our results, along with other Macrofossil studies from the Alps, suggest a nearly simultaneous afforestation (e.g., by Pinus sylvestris in the lower subalpine belt) between 1500 and 2340 m a.s.l. at around 11 400 to 11 300 cal. BP. We suggest that forest-limit species (e.g., Pinus cembra, Larix decidua) could expand faster at today's treeline (c. 2350 m a.s.l.), than 550 m lower. Earlier expansions at higher altitudes probably resulted from reduced competition with low-altitude trees (e.g. Pinus sylvestris) and herbaceous species. Comparison with other proxies such as oxygen isotopes, residual A14C, glacier fluctuations, and alpine climatic cooling phases suggests climatic sensitivity of vegetation during the early Holocene.
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middle to late holocene vegetation history of the upper engadine swiss alps the role of man and fire
Vegetation History and Archaeobotany, 2003Co-Authors: Erika Gobet, Willy Tinner, Peter A Hochuli, J F N Van Leeuwen, Brigitta AmmannAbstract:To reconstruct the vegetation and fire history of the Upper Engadine, two continuous sediment cores from Lej da Champfer and Lej da San Murezzan (Upper Engadine Valley, southeastern Switzerland) were analysed for pollen, plant Macrofossils, charcoal and kerogen. The chronologies of the cores are based on 38 radiocarbon dates. Pollen and Macrofossil data suggest a rapid afforestation with Betula, Pinus sylvestris, Pinus cembra, and Larix decidua after the retreat of the glaciers from the lake catchments 11,000 cal years ago. This vegetation type persisted until ca. 7300 cal b.p. (5350 b.c.) when Picea replaced Pinus cembra. Pollen indicative of human impact suggests that in this high-mountain region of the central Alps strong anthropogenic activities began during the Early Bronze Age (3900 cal b.p., 1950 b.c.). Local human settlements led to vegetational changes, promoting the expansion of Larix decidua and Alnus viridis. In the case of Larix, continuing land use and especially grazing after fire led to the formation of Larix meadows. The expansion of Alnus viridis was directly induced by fire, as evidenced by time-series analysis. Subsequently, the process of forest conversion into open landscapes continued for millennia and reached its maximum at the end of the Middle Ages at around 500 cal b.p. (a.d. 1450).
Stephen T Jackson - One of the best experts on this subject based on the ideXlab platform.
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reliability of Macrofossils in woodrat neotoma middens for detecting low density tree populations
Paleobiology, 2011Co-Authors: Mark R Lesser, Stephen T JacksonAbstract:Abstract Macrofossils from woodrat (Neotoma) middens serve as an important proxy for reconstructing past vegetation in arid and semiarid regions of North America. The presence/absence of plant Macrofossils in middens can provide valuable information on temporal and spatial patterns of plant migration and range boundaries. The primary aim of this study was to determine how local plant abundance, distance of plant populations from midden sites, and species population density on the landscape affect the probability of occurrence of Macrofossils in middens. The study was designed with the primary intent of determining the reliability of middens in detecting scattered populations of Pinus ponderosa. We analyzed Macrofossil assemblages from 42 modern woodrat middens from West Carrizo Canyon in southeastern Colorado, near the current eastern range margin of Pinus ponderosa. We compared midden contents with composition of the surrounding vegetation, measuring distance from the midden to the nearest individual of ...
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mapped plant Macrofossil and pollen records of late quaternary vegetation change in eastern north america
Quaternary Science Reviews, 1997Co-Authors: Stephen T Jackson, Jonathan T Overpeck, Thompson Webb, Sharen E Keattch, Katherine H AndersonAbstract:Abstract Macrofossil presence/absence maps and isopoll maps in 3000-year intervals show how ranges and abundance maxima for 12 eastern North American tree and shrub taxa (Picea, P. glauca, P. mariana, Larix laricina, Abies balsamea, Tsuga canadensis, Pinus strobus, P. resinosa, P. banksiana, Betula papyrifera, B. alleghaniensis, B. Series Humiles) have changed from the last glacial maximum to the present. The Macrofossil maps corroborate patterns shown by the isopoll maps and provide spatial detail and taxonomic resolution. The Macrofossils confirm the inference from pollen data that unglaciated southeastern North America was cooler during the last glacial maximum (18 and 15 ka) than simulated by the COHMAP experiments with the NCAR CCM0 general circulation model. The geographic distribution of Macrofossil occurrences during the Late glacial (12 and 9 ka) indicate that migration lag of boreal species did not occur at regional to subcontinental scales, and that pollen assemblages lacking modern analogs resulted from climate gradients lacking modern analogs. Early Holocene (9 and 6 ka) Macrofossil maps show rapid northward expansion of tree species ranges into deglaciated regions. The data also show modest contractions of northern range limits of temperate species and expansions of southern range limits of boreal species in response to cooling trends during the late Holocene (3 and 0 ka). Comparison of modern Macrofossil maps of nine of these taxa with corresponding range maps confirm that the Macrofossils record the geographic ranges accurately. Comparison of the modern Macrofossil maps with maps of tree growing-stock volume shows that for some taxa (Abies, Tsuga) Macrofossil occurrences were most frequent in regions of maximum tree abundance. Comparison of modern isopoll maps with the modern range and growing-stock volume maps indicate that, in contrast to the Macrofossil data, the pollen data provide poorer resolution of range limits for most taxa, but better indications of abundance maxima and minima within the ranges.
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pollen and Macrofossils from wisconsinan interstadial sediments in northeastern georgia
Quaternary Research, 1993Co-Authors: Stephen T Jackson, Donald R. WhiteheadAbstract:Pollen and plant Macrofossil analyses and dating (both TAMS and conventional 14 C) of wetland sediments from the Nodoroc Site in the Piedmont region of northeastern Georgia identified two depositional episodes of interstadial (ca. 26,000-22,000 yr B.P.) and mid- to late Holocene (<3600 yr B.P.) age. Interstadial pollen assemblages were dominated by Pinus and Quercus, with Carya, Picea, and Abies also present in significant amounts. The interstadial assemblages had lower Pinus and higher Quercus pollen percentages than apparently contemporaneous assemblages from sites in the southern Appalachians and Coastal Plain. Interstadial Macrofossils included two needle morphotypes of Pinus subgenus Pinus, possibly indicating local occurrence of two Pinus species. One of the needle morphotypes is consistent with Pinus banksiana, but other species cannot be ruled out. Comparison of conventional and TAMS 14C dates illustrates problems in obtaining accurate age models from wetlands and ponds characterized by shallow or fluctuating water levels, low sedimentation rates, and vegetation growing on the depositional surface.
H. John B. Birks - One of the best experts on this subject based on the ideXlab platform.
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Challenges in the presentation and analysis of plant-Macrofossil stratigraphical data
Vegetation History and Archaeobotany, 2014Co-Authors: H. John B. BirksAbstract:Plant-Macrofossil analysis is being increasingly used in Quaternary science, particularly palaeoecology and vegetation history. Although the techniques of Macrofossil analysis are well-tried and relatively simple, the resulting data consisting of qualitative binary presences and absences, ordinal classes, and quantitative counts are not simple from the viewpoint of numerical data-analysis. This essay reviews the nature of Macrofossil data and discusses the problem of zero and non-zero values. Problems in the presentation of Macrofossil data are outlined and possible solutions are discussed. The handling of such data is discussed in terms of data summarisation, data analysis, and data interpretation. Newly developed numerical methods that take account of the mixed nature and the stratigraphical ordering of Macrofossil data are outlined, such as (distance-based) multivariate regression trees, canonical analysis of principal coordinates, principal curves, cascade multivariate regression trees, and RLQ analysis. These and other techniques outlined have the potential to help exploit the full potential of Macrofossil stratigraphical data in Quaternary palaeoecology.
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Holocene forest development along the Setesdal valley, southern Norway, reconstructed from Macrofossil and pollen evidence
Vegetation History and Archaeobotany, 2006Co-Authors: Wenche Eide, Hilary H Birks, Nancy H. Bigelow, Sylvia M. Peglar, H. John B. BirksAbstract:The Setesdal valley in South Norway runs north to south for 200 km, from alpine vegetation at 1200 m, passing the tree-line at around 1000 m, through Boreal forests, to Nemoral forest at sea level. The Holocene vegetation history and its altitudinal differentiation were reconstructed using pollen percentages and influx and plant Macrofossil concentration records from four lakes along an altitudinal transect. During the early Holocene (c. 10500–8000 cal b.p. ) Betula pubescens, Pinus sylvestris , Alnus , and Corylus expanded in the lowlands. Only Pinus and B. pubescens reached 1000 m asl (Lille Kjelavatn). Only B. pubescens reached Holebudalen (1144 m asl) at about the same time as it arrived in the lowlands. Between c. 8000–3000 cal b.p. mixed deciduous forest developed around Dalane (40 m asl) and to a lesser extent around Grostjørna (180 m asl), birch woodland with pine surrounded Lille Kjelavatn and birch woodland occurred at Holebudalen. From c. 3000 cal b.p. to present, the vegetation at Dalane hardly changed except for slight human impact and the immigration of Picea abies . At Grostjørna Pinus expanded. At Lille Kjelavatn Pinus disappeared and Betula became sparse as at the tree-line today. Betula retreated from Holebudalen thus leaving it above the tree-line in low-alpine vegetation. The strengths and weaknesses of pollen and plant Macrofossil data were assessed for forest reconstructions. Where local pollen production is low, as near the tree-line, percentages of long-distance tree pollen can be misleadingly high. Pollen influxes of Betula and Pinus were much smaller near their altitudinal limits than at lower altitudes, although their Macrofossils were equally abundant. The limited dispersal capacity of Macrofossils documents the local presence of species and the character of the local vegetation, although Macrofossils of some tree taxa are rarely found. Pollen and plant Macrofossil evidence complement each other to provide a more complete reconstruction of Holocene tree-limits and tree-lines and hence climate changes, than either form of evidence alone.
