A pollen record of the last 450 years from a lowland peat bog on Tristan da Cunha,South Atlantic,implying early anthropogenic influence

A pollen diagram from a small peat bog on the island of Tristan da Cunha in the central South Atlantic (37°05'S,12°17'W) is presented. The pollen diagram contains data from both introduced and native plant taxa. The earliest pollen grains from introduced Plantago lanceolata are dated to around AD 1570, and probably represent unintentional introductions of weeds by the earliest Portuguese explorers visiting the islands. After AD 1600, a greater abundance of pollen from introduced plants and declining tree pollen values indicate opening of the lowland vegetation and more intense land use, probably attributable to the effect of seasonal seal and whale hunters. After AD 1800, evidence of increased erosion and more intense land use are inferred from the pollen diagram, reflecting permanent settlement. Copyright © 2011 John Wiley & Sons, Ltd.     

An 11 000-year record of vegetation and environment from Lago di Martignano,Latium, Italy

A pollen diagram from Lago di Martignano, a maar lake in central Italy, provides an 11000-year record of vegetation and environment change. The earliest pollen spectra are dominated by Artemisia and Gramineae, representing late glacial steppe vegetation typical of the Mediterranean region. Broad-leaved forests were established by ca. 11 000 yr BP. Although Quercus initially dominated their canopy, a wide range of other mesophyllous trees were also present. Pollen values for sclerophyllous tree and shrub taxa characteristic of Mediterranean woodlands and scrub are initially low (<10%). After ca. 7000 yr BP, however, they begin to increase and rise to a peak of >40% of total land pollen at ca. 6700 yr BP, with Olea europaea the single most abundant taxon. Human influence upon the vegetation only becomes significant somewhat after this peak, with progressive clearance of woodland and expansion of herbaceous communities. Castanea sativa and luglans regia pollen is recorded consistently from the beginning of the rise in pollen values for taxa characteristic of Mediterranean scrub communities. Pollen values for arable crops increase progressively after ca. 5500 yr BP, following the peak pollen values for taxa characteristic of Mediterranean scrub vegetation. Late glacial and Holocene climate changes have been complex in this region, with the present character of the climate developing only during the last millennium. Rates of change of pollen spectra peak during this period.     

Late Holocene vegetational history,human impact and pollen representativity variations in northern Cumbria,England

The comparison of pollen diagrams and their inferred vegetational histories are an important component of palaeoecological research. Radiocarbon-dated pollen profiles from three cores taken from two adjacent mires located in northern Cumbria, Bolton Fell Moss and Walton Moss, have been used to reconstruct the Late Holocene vegetation history between the Bronze Age and the present day. The profiles have been interpreted in the light of available archaeological and historical records and, although the pollen records are broadly similar, there are some notable differences between them, particularly during Iron Age and medieval times. Dissimilarities between the diagrams are explored numerically, and the statistical and palynological results are discussed in relation to pollen representativity. The results suggest that it may be advantageous to construct more than one pollen diagram from a mire, or even adjacent mires, as extra-local pollen may be a more important part of the pollen rain than previously envisaged. © 1998 John Wiley & Sons, Ltd.     

Palynology,sedimentology and palaeoecology of the late Holocene Dead Sea

Palynological and sedimentological studies were performed at two Holocene profiles in erosion gullies (Ze’elim and Ein Feshkha) which dissect the retreating western shore of the Dead Sea. The aim of the project was to analyse possible links between climate, lithology, and vegetation development. The section in Ze’elim shows both lacustrine and fluvial sediments, whereas sedimentation at Ein Feshkha is predominantly lacustrine. The Ze’elim profile, previously used for paleo-lake reconstruction provides an opportunity to compare climate triggered lake levels as paleo-hydrological indicators and vegetation history by use of palynology. The vegetation development in Ze’elim and Ein Feshkha is influenced by both climate and human impact. The pollen record of Ze’elim begins in the Pottery Neolithic, the section of Ein Feshkha in the Late Bronze Age, both records end in the Middle Ages. The Ze’elim section is characterized by sedimentary hiati between the beginning of the Chalcolithic Period until the Middle Bronze Age and within the Late Bronze Age. Settlement periods during the Middle Bronze Age, Iron Age and Hellenistic–Roman–Byzantine Period are indicated by high values of anthropogenic indicators and/or Mediterranean trees. Collapses of agriculture, which can be related to climate effects, are evident during the Late Bronze Age, during the Iron Age and at the end of the Byzantine Period when the lake level curve indicates arid conditions. A comparison of the two pollen records, from different environments, illustrates a more prominent influence of Mediterranean vegetation and cultivated plants in the pollen diagram of Ein Feshkha. The southern Dead Sea region (at the desert fringe) is more vulnerable to regional climate change.     

A full-glacial biota from southeastern Iowa,USA

Wisconsinan full-glacial silts filling a swale exposed in Conklin Quarry, Johnson Co., Iowa, contain a large and diverse biota that includes pollen, bryophytes, vascular-plant macrofossils, small mammals, molluscs, and insects. Radiocarbon dates on wood from the top, middle and bottom of the swale fill respectively were 16710 ± 270, 17 170 ± 205, and 18090 ± 190 yr BP. The pollen diagram is dominated by Picea (spruce), Pinus (pine), and Cyperaceae (sedge), and it records low pollen accumulation rates. Plant macrofossils include a number of tundra species along with Picea and Larix (larch) needles and small pieces of wood. The insect fauna contains many species now confined to the forest-tundra transition zone of northwestern Yukon and Alaska. Small mammals include the tundra indicators Dicrostonyx (collared lemming), and probably Microtus miurus (singing vole) together with boreal forest taxa. The molluscs include extinct and relict species and show the widest range in present geographic distribution, but Rocky Mountain and especially northern elements predominate in the swale fill. All these lines of evidence lead to consistent palaeoclimato-logical interpretation and palaeoecological reconstruction. The dominant habitats represented by the biota and sedimentary environment collectively included open calcareous silty to sandy or gravelly upland sites, minerotrophic fens (wetlands), pond- or stream-side clayey to sandy shores, and shallow (possibly ephemeral), cold, clear-water ponds. Mean July temperatures were probably 11° to 13°C cooler than at present. The biota indicates that a Picea-Larix krummholz with extensive tundra openings was present in southeastern Iowa between 18090 and 16710 yr BP.     

Environmental changes during the past 2000 years in north-central Wisconsin: Analysis of pollen,charcoal, and seeds from varved lake sediments

A 2000-year accumulation of varved sediments from Hell's Kitchen Lake in north-central Wisconsin was analyzed for pollen, charcoal, and seeds. The varves provided an accurate time scale for the study. The pollen record indicates changes on two different time scales. Short-term changes lasting several decades appear to be superimposed on long-term changes lasting several centuries. The short-term changes are related to individual fires, and the long-term changes result from increases or decreases in the frequency of these perturbations. From 2000 to 1150 years ago the average interval between fires was about 100 years, and from 1150 to 120 years ago the interval increased to about 140 years. Evidence from pollen, seeds, and charcoal at Hell's Kitchen Lake suggests that at least two “moist” intervals occurred during the past 2000 years, one between 2000 and 1700 years ago and the other between 600 and 100 years ago. A third but minor “moist” period occurred about 1150 to 850 years ago. A pollen and seed diagram shows that these intervals are characterized by increased percentages of white pine pollen, hemlock pollen, and yellow birch seeds, and by decreased levels of charcoal. The “dry” interval of 1700 to 1150 years ago is characterized by increased percentages of paper birch seeds, oak pollen, and aspen pollen, along with high levels of charcoal. The times of climatic change indicated at Hell's Kitchen Lake are nearly synchronous with those based on studies of tree rings, soils, glacial activity, and other pollen studies from various regions of North America, but the direction of these inferred changes is not always the same. This result suggests that the long-wave pattern of the general circulation has been variable during the past 2000 years.     

Post-Glacial climatic change on Boothia Peninsula, Nunavut, Canada

A high temporal resolution pollen diagram from a lake in the mid-Arctic region of the Boothia Peninsula, Nunavut, Canada, documents the history of the regional vegetation and climate for the past 7200 yr. Major tundra pollen taxa in the core include Cyperaceae and Salix, with Cyperaceae comprising over 50% of the pollen in the early and late Holocene. Tree pollen, transported from far to the south, comprised a large percentage of the pollen sum, with Pinus accounting for 30% of the pollen in some levels of the core. Pollen percentages and concentrations of taxa typical of the mid-Arctic were highest in the mid-Holocene, corresponding to warm conditions. Decreasing pollen concentrations indicate cooling temperatures, with more rapid decreases occurring around 4200, 3800-3400, and 2500 cal yr BP. Pollen percentages of Salix, Cyperaceae, and Artemisia increased in the past 35 yr in response to global warming. Reconstructions of July temperature using the modern analog technique showed that the mid-Holocene (5800-2800 cal yr BP) was approximately 1 °C higher than during the past 1000 yr.     

Palynology in a polar desert, eastern North Greenland

A pollen diagram from a lake in a polar desert in eastern North Greenland records the regional vegetation history back to c. 7,000 years calBP (6,000 years convBP) in this extreme environment, which presents the coldest thermal regime where vascular plants can grow. The diagram shows that polar desert developed from sparse high arctic tundra at c. 4,300 years calBP (3,900 years convBP), owing to reduced summer heat. Also adjacent parts of high arctic Greenland, Canada and Svalbard suffered environmental decline, and polar deserts - presently restricted to a narrow fringe of land at the shores of the Arctic Ocean - were even more restricted before this time. Like other arctic vegetation types, polar desert is highly sensitive to summer temperatures, and its southern limit coincides with the isotherm for mean July temperatures of 3.5C. A comparison with the Northwest European ice-age pollen record shows no evidence of summers as cold as those now prevailing in the extreme north, and the results support the contention that the present Arctic and the ice-age mid-latitude environments are not identical.     

Paleoclimatic Changes During the Last 2.5 Ma Recorded in the Kathmandu Basin, Central Nepal Himalayas

PALEOCLIMATIC CHANGES DURING THE LAST 2.5Ma RECORDED IN THE KATHMANDU BASIN, CENTRAL NEPAL HIMALAYAS     

Assessing the use of mangrove pollen as a quantitative sea-level indicator on Mahé, Seychelles

We investigated the potential of mangrove pollen from Mahé, Seychelles, to improve existing metre-scale Late Holocene sediment-based sea-level reconstructions. Mangrove species at two mangrove sites are broadly zoned according to elevation within the tidal frame. Modern pollen rain from traps deployed for 1 year generally have a poor relationship with modern vegetation, and relatively low pollen production rates. Pollen from mangrove species that live in narrow elevation zones (e.g. Avicennia marina) are poorly represented in modern pollen rain, while pollen from mangrove species that live across a larger elevational range (e.g. Rhizophora mucronata) are relatively well represented. Pollen was found in extremely low concentrations in mangrove surface and core sediments, which inhibited further study into pollen transport and preservation. The results from this modern study demonstrate that utilizing mangrove pollen would not decrease existing metre-scale vertical uncertainties in Late Holocene sea-level reconstructions in the Seychelles. We suggest that this approach may still be successful in other locations if mangrove vegetation is (i) zoned at a more extensive lateral scale and (ii) is closely associated with modern pollen rain and surface sediments, and (iii) sedimentological conditions promote the preservation of pollen in fossil sequences.     

Comparative 210Pb, 137Cs,and pollen geochronologies of sediments from Lakes Ontario and Erie

The distribution of ²¹⁰Pb, ¹³⁷Cs, and Ambrosia (ragweed) pollen in two sediment cores from Lake Ontario and in three cores from Lake Erie provides independent estimates of sediment accumulation rates. Geochronology with ²¹⁰Pb is based on radioactive decay of the isotope following burial in sediments. The method can reveal with precision changes in sedimentation occurring over the past 100 yr or so. Geochronologies with ¹³⁷Cs and Ambrosia are based on the occurrence of a horizon corresponding, respectively, to the onset of nuclear testing 25 yr ago and to regional forest clearance in the middle 1800s. These methods provide estimates of long-term average sediment accumulation rates. In all but one core, the distributions of ¹³⁷Cs and ²¹⁰Pb indicate no physical mixing of near-surface sediments. In two cores, including one from central Lake Erie collected by diver, all three estimates of sedimentation rates are in excellent agreement. In two other cores, rates based on ²¹⁰Pb are significantly higher than those inferred from Ambrosia pollen profiles. Lower average rates appear to result from occasional massive losses of sediments. Such events, apparent in the distribution of ²¹⁰Pb but not in pollen records, correlate with the occurrence of major storm surges on the lakes during this century. In one core from western Lake Erie, exponential distributions of both ²¹⁰Pb and Ambrosia appear to be artifacts which may result from extensive biological or physical reworking of sediments in shallow water (11 m). Previous indications of increased sedimentation in Lake Erie since about 1935 based on Castanea (chestnut) pollen data are not substantiated.     

Development of pollen assemblage zones in soil profiles in southeastern England

Four soil profiles within c. 4 ha of dry heathland on lping Common, southeastern England were studied. Two were podzols, one was a buried profile from beneath a Bronze-age barrow and one was a profile buried beneath sediment in a small pond. Loss on ignition, particle size analysis, iron concentration and pollen concentration were determined and a pollen diagram prepared for each profile. It is suggested that discrete soil pollen assemblage zones arise from their incorporation by successively shallower-burrowing earthworm populations as the soils and vegetation change from mull to mor types. The implications of this mode of incorporation to the interpretation of soil pollen diagrams are discussed. A sequence of vegetation and soils for this area is suggested as follows:(1) mixed deciduous woodland of Quercus. Tilia and Corylus with a fern-rich understorey growing in a mull soil, (2) scrub woodland of Betula and Corylus with Pteridium and some Callunu, (3) Calluna heathland on podzolised soils. ¹⁴C dates obtained from podzol Bh horizons and the buried soil beneath the pond were inconclusive.     

Pollen analytical biostratigraphy of the last five climatic cycles from a long continental sequence from the Velay region (Massif Central,France)

In the volcanic region of Velay (Massif Central, France), lake sediment sequences derived from maar craters situated close to one another (Ribains, Praclaux and Lac du Bouchet) have been correlated on the basis of tephrostratigraphical analyses. This has enabled the construction of a sequence (2980 pollen spectra) that begins during the glaciation preceding the Holsteinian and ends in the present. This sequence covers the period from 450 ka, i.e. from the end of marine oxygen isotope stage 12, to the present time, and includes five climatic cycles. The study of a second core from the Praclaux site completed the long Velay sequence. The biostratigraphy of the whole sequence is described in detail and illustrated by a synthetic and simplified pollen diagram. Thirteen temperate forest episodes (interglacials or interstadials) and as many cold periods (glacials or stadials) are defined. Each temperate episode is characterised by particular forest development and vegetation dynamics, and all of them, with the exception of the Holocene, begin and end with a Pinus forest. The vegetation dynamics observed during the Holocene resemble more closely those recorded during the interstadials than during the interglacials. Copyright © 2000 John Wiley & Sons, Ltd.     

Pollen- and oxygen-isotope analyses of late- and postglacial sediments from the Schwemm raised bog near Walchsee in Tirol, Austria

Oxygen-isotope and pollen analyses were carried out on late- and postglacial (Late Weichselian and Holo-cene) sediment samples of the raised bog. The ¹⁸O/¹⁶O-ratio results provide the first unequivocal proof for the Eastern Alps of the climatic deterioration of the Younger Dryas period. High NAP-values in the pollen diagram and a strong negative deviation in the oxygen-isotope curve characterize this period. The earlier Gerzensee fluctuation is also indicated by small changes in the oxygen-isotope curve. During the postglacial the Frosnitz climatic deterioration (6,000–6,500 B.P.) is evidenced as a fluctuation in the lake-level. The oxygen-isotope values indicate that the air temperature conditions remained unchanged at that time.     

Pollen stratigraphy of the Late Pleistocene sediments at Mommark, Als, South Denmark

Past environmental changes in the Baltic area are discussed on the basis of pollen and spores recovered from marine sediments in a series of cliff sections at Mommark, in southern Denmark. The sediment succession represents Jessen & Milthers' (1928) Eemian pollen zones c-h, or Andersen's (1961 1975) zones E1/2-E7, as well as the earliest Weichselian pollen zone i, or EW-1, the Herning Stadial. A correlation with annually laminated German sequences (e.g. Bispingen) indicates that the sequence spans approximately 11 000 years. Marine deposition began c. 300 years after the beginning of the Eemian Interglacial Stage and continued to shortly before the end of pollen zone E7, at c. 10 600 years after the beginning of the Eemian. Sedimentation rates varied through the time period represented by the sequence, with initial deposition relatively rapid at c. 0.35 cm yr^-1 for the first c. 300 years. Rates then decreased to 0.029 cm yr^-1 for the next 2700 years and remained low, though varying, throughout the rest of the sequence. Overall, the rates indicate that sediment supply was highly restricted throughout the interglacial, possibly reflecting the dense forest vegetation that colonized the hinterland.     

Paleoecology of mangroves along the Sibun River, Belize

This study examines a sediment core (SR-63) from a mangrove ecosystem along the Sibun River in Belize, which is subject to both changes in sea-level and in the characteristics of the river's drainage basin. Radiocarbon dates from the core show a decreased sedimentation rate from ~ 6 ka to 1 cal ka BP and a marked change in lithology from primarily mangrove peat to fluvial-derived material at ~ 2.5 cal ka BP. Changes in the sedimentation rates observed in mangrove ecosystems offshore have previously been attributed to changes in relative sea-level and the rate of sea-level rise. Pollen analyses show a decreased abundance of Rhizophora (red mangrove) pollen and an increased abundance of Avicennia (black mangrove) pollen and non-mangrove pollen coeval with the decreased sedimentation rates. Elemental ratios ([N:C]_a) and stable isotope analyses (δ¹⁵N and δ¹³C) show that changes in the composition of the organic material are also coeval with the change in lithology. The decrease in sedimentation rate at the site of core SR-63 and at offshore sites supports the idea that regional changes in hydrology occurred during the Holocene in Belize, influencing both mainland and offshore mangrove ecosystems.     

Modern pollen assemblages and vegetational history of the moraines of the Klutlan Glacier and its surroundings,Yukon Territory,Canada

Modern pollen assemblages have been studied from surficial lake muds and moss polsters collected from five vegetated ice-cored moraines of the Klutlan Glacier. The youngest vegetated moraine (K-II) is characterized by high pollen values for Salix and Hedysarum, K-III by high Salix and Shepherdia canadensis and low Hedysarum and Picea, K-IV by high Betula, Salix, and Shepherdia, and K-V and the Harris Creek moraine (HCM) by high Picea. Variations are summarized by canonical variates analysis. A percentage pollen diagram from Gull Lake on the upland east of the glacier records vegetational development since the deposition of the White River volcanic ash 1220 ¹⁴C yr ago. An initial species-rich treeless vegetation was replaced by birch-alder-willow shrub-tundra, and this by open Picea glauca forest similar to present vegetation around the lake. Sites on HCM show two basic stratigraphies. Triangle Lake reflects vegetational succession from Salix-Shepherdia canadensis scrub similar to that on K-III today, through open Picea woodland of K-IV type, to closed Picea forests of K-V and HCM. Heart Lake and Cotton Pond reflect vegetational development following melting of ice underlying the spruce forests of HCM. These two types are summarized by positioning the fossil spectra on the first two canonical variate axes of the modern surface spectra.     

Evidence from coleopteran assemblages for a short but intense cold interlude during the latter part of the MIS11 Interglacial from Quinton, West Midlands, UK

A sequence of fossiliferous organic sediments spanning the whole of an interglacial has been investigated from Quinton, near Birmingham, United Kingdom This interglacial can be correlated on palynological grounds with the Hoxnian Interglacial of England; equivalent to the Holsteinian Interglacial of central Europe and to Marine Isotope Stage 11. A pollen diagram and coleopteran spectrum were obtained from the same series of samples. By using the mutual climatic range method on the coleopteran assemblages, it has been possible to quantify the thermal climatic conditions at this time. They show clear evidence for a sudden and intense climatic oscillation during the late temperate stage of the interglacial—named the Quinton Cold Interlude. At this time mean temperatures of the warmest month (July) declined suddenly by at least 5 °C and mean temperatures of the coldest months (January and February) by more than 10 °C. Subsequently cool-temperate conditions returned. The pollen diagram through this interval shows little or no response to this climatic event. It is too early yet to generalise about the regional significance of the Quinton Cold Interlude but a similar climatic oscillation also occurs towards the closing stage of the MIS11 Interglacial at Hoxne, Norfolk, UK, suggesting that the cold interlude was at least regional in extent. A short climatic oscillation of similar intensity has also been interpreted from coleopteran evidence towards the end of the MIS13 Interglacial at Waverley Wood Farm Pit, Warwickshire, UK, indicating that such events may characterise the later stages of other interglacials. These severe climatic oscillations towards the end of interglacials may have relevance to our understanding of the closing phase of the present interglacial.     

The importance of plant macrofossils in the reconstruction of Lateglacial vegetation and climate: examples from Scotland,western Norway,and Minnesota,USA

Lateglacial and early Holocene (ca 14–9000 ¹⁴C yr BP; 15–10,000 cal yr BP) pollen records are used to make vegetation and climate reconstructions that are the basis for inferring mechanisms of past climate change and for validating palaeoclimate model simulations. Therefore, it is important that reconstructions from pollen data are realistic and reliable. Two examples of the need for independent validation of pollen interpretations are considered here. First, Lateglacial-interstadial Betula pollen records in northern Scotland and western Norway have been interpreted frequently as reflecting the presence of tree-birch that has strongly influenced the resulting climate reconstructions. However, no associated tree-birch macrofossils have been found so far, and the local dwarf-shrub or open vegetation reconstructed from macrofossil evidence indicates climates too cold for tree-birch establishment. The low local pollen production resulted in the misleadingly high percentage representation of long-distance tree-birch pollen. Second, in the Minnesotan Lateglacial Picea zone, low pollen percentages from thermophilous deciduous trees could derive either from local occurrences of the tree taxa in the Picea/Larix forest or from long-distance dispersal from areas further south. The regionally consistent occurrence of low pollen percentages, even in sites with local tundra vegetation, and the lack of any corresponding macrofossil records support the hypothesis that the trees were not locally present. Macrofossils in the Picea zone represent tundra vegetation or Picea/Larix forest associated with typically boreal taxa, suggesting it was too cold for most thermophilous deciduous trees to grow. Any long-distance tree pollen is not masked by the low pollen production of tundra and Picea and Larix and therefore it is registered relatively strongly in the percentage pollen spectra.Many Lateglacial pollen assemblages have no recognisable modern analogues and contain high representations of well-dispersed ‘indicator’ taxa such as Betula or Artemisia. The spectra could have been derived from vegetation types that do not occur today, perhaps responding to the different climate that resulted from the different balance of climate forcing functions then. However, the available contemporaneous plant-macrofossil assemblages can be readily interpreted in terms of modern vegetation communities, suggesting that the pollen assemblages could have been influenced by mixing of locally produced pollen with long-distance pollen from remote vegetation types that are then over-represented in situations with low local pollen production. In such situations, it is important to validate the climate reconstructions made from the pollen data with a macrofossil record.     

Taphonomy or signal sensitivity in palaeoecological investigations of Norse landnám in Vatnahverfi,southern Greenland?

Anthrosols (cf. plaggen soils) are commonly found across the homefields of Norse farms, yet the extent to which these taphonomically complex and heterogeneous deposits provide reliable archives of environmental change and vegetation history has rarely been investigated. This paper compares the palynological signature contained within an anthrosol located beside Norse farm ruins in the Eastern Settlement of Greenland, with that from a mire situated ～400 m from the nearest archaeological remains. The investigation covers a period of ～1000 years leading into, through, and beyond the Greenlandic landnám of AD 985. The results demonstrate that, as anticipated, the anthrosol contains a strong signal for human impact associated with settlement and occupation, although changes in both pollen percentages and accumulation rates (influx) through the profile appear smooth, not erratic, and radiocarbon dates are conformable. Thus the palynological signature contained in the anthrosol is broadly comparable to the patterns characteristic of stratified natural contexts (e.g. mires) with small pollen source areas that are located in close proximity to former Norse structures. Nevertheless, it is also demonstrated that secondary microfossils are a major component of the pollen assemblages within the anthrosol, and pollen influx is notably an order of magnitude higher when compared against the peat core taken from the mire. It is suggested that this may result from the addition of pollen contained in animal dung, augmenting that accumulating through the natural accretion of pollen derived from the surrounding vegetation and landing on the surface of the anthrosol. Although this complicates any palynological interpretation, by adopting a cautious approach we argue that anthrosols can be used to extract useful information about vegetation history at a local scale, as well as providing indirect evidence of landscape impacts and resource use around farmsteads.