Article

Fossil stomata reveal early pine presence in Scotland: Implications for postglacial colonization analyses

Ecology

March 2005
86(3):579-586

DOI:10.1890/04-0546

Authors:

Cynthia A. Froyd

Swansea University

The analysis of fossil stomata reveals the early postglacial presence of Pinus sylvestris at two sites in the Scottish Highlands, 1600 and 600 years prior to the arrival times indicated by traditional palynological methods. Fossil stomata provide unambiguous evidence of past local presence. for Pinus sylvestris, which produces abundant and widely dispersed pollen, revealing its presence when pine pollen frequencies are as low as 0.4%, considerably below the commonly adopted minimum frequency threshold of 20%. Thus a species may,be present for hundreds to thousands of years before expansion of the local population is registered in the palynological record. This has significant implications, not only for the initial spread of pine throughout the British Isles, but more generally for analyses of the continental-scale migration of temperate and boreal forest taxa based on palynological data. Failure to differentiate effectively among the processes of arrival, establishment, and expansion in analyses of plant migration rates and patterns means that many existing reconstructions of postglacial colonization may, in actuality, represent the expansion of populations over time, rather than the initial spread of species.

‘Pine Decline or pine declines?’ Analysis and Interpretation of Bog-Pines from Wem Moss, Shropshire, UK

Article

Full-text available

Feb 2023

Jonathan G A Lageard

A dendrochronological investigation was undertaken on subfossil Scots pine (Pinus sylvestris L.) stumps following their discovery during conservation management at Wem Moss, a small (28 ha) former raised mire in Shropshire, UK. Two ring-width chronologies were constructed from 14 of the 17 trees sampled spanning 198 and 208 years, respectively. Whilst dendrochronological dating was not possible, radiocarbon assays provided an estimated age for this mire-rooting woodland of between 3015 and 2505 years cal. BCE, coinciding with the age traditionally associated with the widespread mortality of pine trees throughout much of the UK and Ireland, often referred to as the Pine Decline (ca. 4000 radiocarbon years BP). Placed in a wider geographical context, the Wem Moss pines are located within the lowland Meres and Mosses region, where previous studies on subfossil pine have demonstrated protracted declines in mire-rooting trees. These have included tree mortality significantly post-dating the Pine Decline, especially at larger peatland sites that exceed 5 km2. Such macrofossil evidence for the presence of Scots pine into the late Holocene is supported by continuous Pinus pollen representation at peatland sites in the Welsh Marches (English–Welsh border), suggesting the possible survival of native Scots pine trees in this area up to the present day. The investigation of Wem Moss bog pines and their wider geographical context highlights the incomplete and patchy nature of palaeo-vegetational records and also the need for future genetic research on living Scots pine in possible refugial areas in Britain and Ireland.

The interaction of fire, climate and vegetation in the boreal forest of Alaska-Yukon during the Holocene

Thesis

Jan 2006

Leanne Franklin-Smith

p>Using radiocarbon-dated sedimentary records with the temporal focus on two key vegetative transitions (deciduous- Picea and Picea-Pinus) and a climatic transition (cold and dry to moister), high resolution time series of charcoal-peak frequencies form lake sediments are used as a proxy of the local fire regime. The regional vegetation transition from deciduous- to coniferous-dominated forest at ~10ka BP displays a clear sequence where the climate shift precedes the alteration in vegetation composition, to which the fire regime responds. The deciduous vegetation experienced low levels of burning, with a lower fire frequency than when Picea became dominant on the landscape, suggesting that Picea was excluded from the landscape due to moisture limitations rather than high fire return frequencies. In the Yukon Territory, Pinus contorta (lodgepole pine) is migrating northwards and westwards towards Alaska, and is considered a potential invasive species to the northern boreal forest of Alaska under global warming. Lodgepole pine is a fire-dependent species that appears to thrive and spread when fires are intense and frequent. Analysis of stomata reveals lodgepole pine was present in the Southern Yukon forests, at least in low numbers, by ~6 ka BP, much earlier than conventional pollen records suggest. The main population expansion (represented by increased Pinus pollen from <5 to >15%) was regionally asynchronous, and occurred over 3 ka after the first appearance of Pinus. Contrary to expectations derived from flammability estimates and modern observations that pine stands burn particularly frequently, there is no clear, sustained increase in charcoal peak frequency in the late-Holocene Pinus zone; Pinus-Picea forests appear to have burned under a regime similar to that of the preceding Picea -dominated forests.</p

Identification of Conifer Stomata in Pollen samples from Western North America

Article

Jun 2016
REV PALAEOBOT PALYNO

Conifer stomata provide important paleoecological information for determining the composition of past plant communities, particularly at the local scale and when plant macrofossils are absent. To aid efforts to identify conifer stomata in fossil pollen samples from western North America, we describe the stomatal morphology of 19 conifer species that occur in the region, with emphasis on species that are present in the conifer-dominated forests along the northwest Pacific coast. We measured 10 morphological traits in a total of 315 stomata from these species. Morphological variability within species and the degree of morphological overlap among species precludes reliable identification to the species level; however, stomatal morphology is relatively consistent within genera and sufficiently unique to permit identification to genus. We used classification and regression trees to identify the critical morphological features for stomata identification and to build classification models. We then used these classification models as the basis for dichotomous identification keys for complete and incomplete conifer stomata. Identification of conifer stomata in fossil pollen samples from western North America should enhance paleoecological records from the region by providing evidence of local conifer presence and potentially clarifying their arrival times. Conifer stomata also provide a possible avenue for increasing taxonomic resolution in some paleoecological records: Pseudotsuga and Larix as well as members of the Cupressaceae family have indistinguishable pollen morphologies, but our results show that their stomata can be differentiated in most instances.

The relative importance of biotic and abiotic processes for structuring plant communities through time

Article

Dec 2014
J ECOL

The question of the relative importance of biotic interactions versus abiotic drivers for structuring plant communities is highly debated but largely unresolved. Here, we investigate the relative importance of mean July air temperature, nitrogen (N) availability and direct plant interactions in determining the millennial‐scale population dynamics through the Holocene (10 700–5200 cal. years bp ) for four temperate tree taxa in the Scottish Highlands. A variety of dynamic population models were fitted to our palaeoecological time‐series data to determine the mechanism(s) by which each driver affected the population biomass dynamics of Betula (birch), Pinus (pine), Alnus (alder) and Quercus (oak). Akaike information criterion weights identified the best model(s) for describing the relationship between each population and driver. The relative importance of these drivers was then assessed by the ability of each model to predict the observed population biomass dynamics. We also measured the change in goodness‐of‐fit of each model over time. We found that models of intra‐ and interspecific plant interactions described the plant population dynamics better than temperature‐ or N‐dependent population growth models over the 5000‐year study period. The best‐fitting models were constant over time for pine, alder and oak. However, the plant–N availability and plant–temperature models provided a progressively better fit to the birch data when temperatures rose and N availability declined, suggesting increasing importance of these abiotic factors coincident with changing conditions. Synthesis . Multiple mechanistic models were applied to palaeoecological data to infer the most likely processes driving millennial‐scale plant biomass dynamics in a woodland ecosystem. Direct plant interactions provided a better explanation for population biomass dynamics than growing season temperature or N availability over the full study period. The relative importance of all drivers we assessed here varied by species and – in the case of birch – over time in response to warming and reduced N availability.

Imprints of glacial refugia in the modern genetic diversity of Pinus sylvestris

Article

Jan 2006

Results The simulated distribution of P. sylvestris during the last glacial period is coherent with the observed fossil data, which showed a patchy distribution of the refugia between c. 40° N and 50° N. Several migrational fronts were detected within the Iberian and the Italian ...

Patterns in recent and Holocene pollen accumulation rates across Europe - The Pollen Monitoring Programme Database as a tool for vegetation reconstruction

Article

Full-text available

Aug 2021

The collection of modern, spatially extensive pollen data is important for the interpretation of fossil pollen assemblages and the reconstruction of past vegetation communities in space and time. Modern datasets are readily available for percentage data but lacking for pollen accumulation rates (PARs). Filling this gap has been the motivation of the pollen monitoring network, whose contributors monitored pollen deposition in modified Tauber traps for several years or decades across Europe. Here we present this monitoring dataset consisting of 351 trap locations with a total of 2742 annual samples covering the period from 1981 to 2017. This dataset shows that total PAR is influenced by forest cover and climate parameters, which determine pollen productivity and correlate with latitude. Treeless vegetation produced PAR values of at least 140 grains cm-2 yr-1. Tree PAR increased by at least 400 grains cm-2 yr-1 with each 10% increase in forest cover. Pollen traps situated beyond 200 km of the distribution of a given tree species still collect occasional pollen grains of that species. The threshold of this long-distance transport differs for individual species and is generally below 60 grains cm-2 yr-1. Comparisons between modern and fossil PAR from the same regions show similar values. For temperate taxa, modern analogues for fossil PARs are generally found downslope or southward of the fossil sites. While we do not find modern situations comparable to fossil PAR values of some taxa (e.g. Corylus), CO2 fertilization and land use may cause high modern PARs that are not documented in the fossil record. The modern data are now publicly available in the Neotoma Paleoecology Database and aid interpretations of fossil PAR data.

Re-defining the natural range of Scots Pine (Pinus sylvestris L.): A newly discovered microrefugium in western Ireland

Article

May 2016

Aim Native Pinus sylvestris became extirpated in Ireland, during a massive population decline experienced throughout Europe. It was extensively replanted in Ireland during the 18th century from Scottish stock. We test the hypothesis that P. sylvestris in Rockforest Co. Clare did not become extirpated during the P. sylvestris decline, and persisted to present day independent of 18th century plantations. Location Rockforest, Co. Clare in Ireland. Methods Fossil pollen was counted from a terrestrial core. Radiocarbon dates and age‐depth modelling was used to ascertain the core chronology. Loss‐on‐ignition was carried out to investigate sediment accumulation history. Pollen was also counted from moss polster pollen traps to explore the deposition of P. sylvestris pollen in the surrounding landscape. Historical maps were consulted to investigate the longevity of other nearby P. sylvestris populations. Results A continuous record of P. sylvestris is reported. The core extends through the last two millennia, and reports a clear decline of P. sylvestris at c . 1550 cal bp . The P. sylvestris pollen curve recovers quickly after the decline event and persists at high levels up until the present day. The loss‐on‐ignition data reveal a stable accumulation of sediment with no major erosion events. The moss polster pollen traps show the core site is a suitable location for collecting pollen from the Rockforest P. sylvestris population. Historical maps demonstrate that none of the other nearby P. sylvestris populations extends further back than plantations in the early 18th century. Main conclusions The population of P. sylvestris in Rockforest Co. Clare survived the regional P. sylvestris decline, recovered and persisted right up to the present day, independent of introduction by human agency. Hence, we identify this microrefugium population of native Irish stock outside of the current understanding of the native range for this tree species.

The role of fire in the mid-Holocene arrival and expansion of lodgepole pine (Pinus contorta var. latifolia Engelm. ex S. Watson) in Yukon, Canada

Article

Jan 2015

In north-west Canada, Pinus contorta (lodgepole pine) has been migrating northwards and westwards for millennia. Its regeneration is currently enhanced by fire, which may act as a trigger for local population expansion. Using Holocene charcoal records from four small (<10 ha) lakes in southern Yukon, we investigated the relationship between long-term Pinus population dynamics and fire. Fossil stomata extracted from dated lake sediments indicate pine was present at low densities in southern Yukon forests by ~6000 cal. yr BP. At each site, the main population expansion (indicated by an increase in Pinus pollen from <5% to values as high as 60%) occurred 2000–>4000 years after the first local appearance of Pinus, suggesting a long period of stasis at low densities. Population increases – based on pollen accumulation rates (PARs) – occurred at different times at the four sites. Estimated expansion periods were ~2500–800 years, and population doubling times were ~150–600 years, similar to previous estimates. Estimated fire return intervals (FRIs) fluctuated over time. At all sites, the Pinus expansion began during a phase with a relatively short FRI, but only one difference between the mean FRIs before and during the Pinus rise was statistically distinguishable. Nor was the subsequent higher abundance of pine associated with shorter FRIs. It is unlikely that regional pine expansion is primarily linked to changes in climate or a climate-mediated fire regime, although expansion may have been triggered at individual sites during a period of high fire frequency. The long period of stasis at low population densities suggests intrinsic control of population growth; possibly Pinus expansion was initially constrained by lowered reproductive fitness (Allee effect) and/or interaction with local site-based factors.

The potential of stomata analysis in conifers to estimate presence of conifer trees: Examples from the Alps

Article

May 2014

To estimate whether or not a plant taxon found in the fossil record was locally present may be difficult if only pollen is analyzed. Plant macrofossils, in contrast, provide a clear indication of a taxon’s local presence, although in some lake sediments or peats, macrofossils may be rare or degraded. For conifers, the stomata found on pollen slides are derived from needles and thus provide a valuable proxy for local presence and they can be identified to genus level. From previously published studies, a transect across the Alps based on 13 sites is presented. For basal samples in sandy silt above the till with high pollen values of Pinus, for example, we may distinguish pine pollen from distant sources (samples with no stomata), from reworked pollen (samples with stomata present). The first apparent local presence of most conifer genera based on stomata often but not always occurs together with the phase of rapid pollen increase (rational limit). An exception is Larix, with its annual deposition of needles and heavy poorly dispersed pollen, for it often shows the first stomata earlier, at the empirical pollen limit. The decline and potential local extinction of a conifer can sometimes be shown in the stomata record. The decline may have been caused by climatic change, competition, or human impact. In situations where conifers form the timberline, the stomata record may indicate timberline fluctuations. In the discussion of immigration or migration of taxa we advocate the use of the cautious term “apparent local presence” to include some uncertainties. Absence of a taxon is impossible to prove.

A 14,000 year vegetation history of a hypermaritime island on the outer Pacific coast of Canada based on fossil pollen, spores and conifer stomata

Article

Nov 2012

Pollen and conifer stomata analyses of lake sediments from Hippa Island on the north coast of British Columbia were used to reconstruct the vegetation history of this small hypermaritime island. Between 14,000 and 13,230 cal yr BP, the island supported diverse herb–shrub communities dominated by Cyperaceae, Artemisia and Salix. Pinus contorta and Picea sitchensis stomata indicate that these conifers were present among the herb–shrub communities, likely as scattered individuals. Transition to open P. contorta woodland by 13,000 cal yr BP was followed by increases in Alnus viridis, Alnus rubra and P. sitchensis. After 12,000 cal yr BP, Pinus-dominated communities were replaced by dense P. sitchensis and Tsuga heterophylla forest with Lysichiton americanus and fern understory. Thuja plicata stomata indicate that this species was present by 8700 cal yr BP, but the pollen record suggests that its populations did not expand to dominate regional rainforests, along with Tsuga and Picea, until after 6600 cal yr BP. Conifer stomata indicate that species may be locally present for hundreds to thousands of years before pollen exceed thresholds routinely used to infer local species arrival. When combined, pollen and conifer stomata can provide a more accurate record of paleovegetation than either when used alone.

Micromorphology of Pine Needle Primordia and Young Needles after Bud Dormancy Breaking

Article

Full-text available

Feb 2023

Using a scanning electron microscope, the micromorphologies of needle primordia and the young needles of seven pine species (Pinus cembra, P. mugo, P. nigra, P. rigida, P. sylvestris, P. strobus, and P. uncinata) were analyzed at phenological stages B2 and B3 (according to Debazac). In B2, needle tips were rounded or pointed, depending on the species. In P. cembra and P. strobus, teeth were noted on the tips. Teeth were also visible on the margins in P. mugo, P. cembra, and P. strobus. Stomata became visible in the late B2 phase (P. sylvestris, P. mugo, and P. nigra) near the needle tips and were arranged in rows. In the B3 phase, needle tips were pointed. Only in P. strobus was the needle tip slightly rounded. The teeth on the margin in all the species were pointed. In P. strobus, their size and density along the margin decreased basipetally. In B3 for all the species, numerous stomata were visible. In P. sylvestris, P. cembra, and P. strobus, Florin rings were also observed. These observations could be useful in pine systematics but also in palaeobotanical or physiological studies. To the best of our knowledge, this is the first study on the micromorphology of very young needles in representatives of the genus Pinus.

Early to Mid-Holocene Tree Immigration and Spread in the Isle of Man: The Roles of Climate and Other Factors

Article

Full-text available

Jan 2023

The Isle of Man is a large island which lies in the middle of the northern Irish Sea between Britain and Ireland and, because of its insularity and size, has an impoverished flora compared with the two main islands. This has been the case throughout the postglacial and warrants the island’s description as a separate phytogeographic province. We have considered Holocene tree pollen data from seventeen sites on the island which together preserve a vegetation history that spans the six thousand years of the early and mid-postglacial from the end of the Lateglacial at 11,700 cal. BP to the mid-Holocene Ulmus decline at ca. 5800 cal. BP. Radiocarbon dating of the rational limits of the pollen curves for the main tree taxa has allowed an appraisal of the timing of each one’s expansion to become a significant component of the island’s woodland, and comparison with the dates of their expansion on the adjacent regions of Britain and Ireland. The radiocarbon dates show that, although some variability exists probably due to local factors, there is considerable concordance between the timings of major pollen zone boundaries in Britain and Ireland around the northern Irish Sea. On the Isle of Man the expansions of both Juniperus and Betula were delayed by several centuries compared to the British/Irish data, however the timing of the expansions of Corylus, Ulmus, Quercus, Pinus and Alnus on the Isle of Man all appear closely comparable to the ages for these pollen stratigraphic events in north Wales, northwest England, southwest Scotland and eastern Ireland, as are those for the Ulmus decline. It is likely that local pedological and edaphic factors on the island account for the differences in the first Holocene millennium, while regional climatic factors governed the timings for the rest of the expansions of tree taxa across the wider region, including the Isle of Man. Disturbance, including by human agency, was important at the site scale and perhaps triggered early tree expansion in some places, including Quercus, Ulmus and Alnus. Insularity seems not to have been a significant factor in the expansion of the major forest trees.

Pine Decline or Pine Declines? Analysis and Interpretation Bog Pines from Wem Moss, Shropshire, UK

Preprint

Nov 2022

Jonathan G A Lageard

A dendrochronological investigation was undertaken on subfossil Scots pine (Pinus sylvestris L.) stumps following their discovered during conservation management activities at Wem Moss, a small (28ha) former raised mire in Shropshire, UK. Two ring-width chronologies were constructed from 14 of the 17 trees investigated spanning 198 and 208 years respectively. Whilst absolute dating was not possible, radiocarbon assays provided an estimated age for this mire-rooting woodland of between 3015 – 2505 years Cal BC, coinciding with the age traditionally associated with the widespread mortality of pine trees throughout much of the UK and Ireland, The Pine Decline (circa 4 ka radiocarbon years BP). Placed in a wider geographical context, the Wem Moss pines are located within the wider lowland area of the Meres and Mosses Region, where previous studies on subfossil pine have demonstrated protracted declines in mire-rooting trees. These have included tree mortality significantly post-dating The Pine Decline, notably at larger peatland sites exceeding 5.5 km2. This macrofossil evidence for the presence of Scots pine into the late Holocene is supported by continuous Pinus pollen representation at peatland sites in the Welsh Marches (English-Welsh border) suggesting the possible survival of native Scots pine trees in this area up to the present-day. This research highlights the incomplete and patchy nature of palaeo-vegetational records and also the potential for genetic research on living Scots pine in possible refugial areas in the UK and Ireland.

Holocene expansion of the Caledonian pinewoods: Spatial and temporal patterns at regional and landscape scales

Article

Sep 2021

Background : To facilitate climatic change adaptation, landscape and conservation managers require understanding of spatio-temporal patterns of expansion of potential dominant species. Studying past expansions of canopy-dominant trees can contribute such understanding. Aims : Test hypotheses about expansions of dominants using as a model the mid-Holocene expansion of forests dominated by Pinus sylvestris in the Scottish Highlands. Methods : Pollen analysis and radiocarbon dating of Holocene sediments of a larger basin and several small hollows were performed in three landscapes along a north–south transect. A larger basin records expansion timing at landscape scale, whilst small hollows evidence within-landscape spatio-temporal patterns. Results : Vegetation existing prior to the expansion of pinewoods influenced landscape-scale spatio-temporal expansion patterns of P. sylvestris. Open vegetation generally was invaded earlier and/or to a greater extent; invasion was often later, or did not occur, where woodland with a substantial temperate broadleaved tree and shrub component (e.g. Corylus avellana, Quercus spp.) was present. Most small hollows, not just those where pinewoods became locally established, recorded vegetation change during the expansion. Some present landscape-scale forest composition patterns were established at that time. Conclusions : Studying past expansions of dominants provides evidence relevant to planning conservation and landscape management to facilitate ecological adaptation as species adjust their distributions and abundances in response to climatic change.

Scots pine ( Pinus sylvestris ) dynamics in the Welsh Marches during the mid to late-Holocene

Article

Full-text available

Feb 2021

Around 4000 cal yr BP, Scots pine ( Pinus sylvestris) suffered a widespread demise across the British Isles. This paper presents new information about P. sylvestris populations found in the Welsh Marches (western central Britain), for which the long-term history and origins are poorly known. Two new pollen records were produced from the Lin Can Moss ombrotrophic bog (LM18) and the Breidden Hill pond (BH18). The LM18 peat core is supported by loss-on-ignition, humification analysis and radiocarbon dating. Lead concentrations were used to provide an estimated timeframe for the recent BH18 record. In contrast to many other Holocene pollen records from the British Isles, analysis of LM18 reveals that Scots pine grains were deposited continuously between c. 6900–300 cal yr BP, at frequencies of 0.3–5.4%. It is possible that individual Scots pine trees persisted through the wider demise on thin soils of steep drought-prone crags of hills or the fringes of lowland bogs in the Welsh Marches. At BH18, the record indicates a transition from broadleaved to mixed woodland, including conifer species introduced around AD 1850 including Picea and Pinus. The insights from BH18 suggest that the current populations may largely be the result of planting. Comparison of the LM18 findings with other regional pollen records highlights consistent patterns, including a Mid-Holocene maximum (ca. 7000 cal yr BP), long-term persistence at low pollen percentages and a Late-Holocene minimum (ca. 3000 cal yr BP). These distinctive trends encourage further studies on refugial areas for Scots pine in this region and elsewhere.

New insights into Late Devensian Lateglacial and early Holocene environmental change: Two high-resolution case studies from SE England

Article

Apr 2021
REV PALAEOBOT PALYNO

The Late Devensian Lateglacial to early Holocene transition across north-west Europe was characterized by a rapid shift in climate from the cold, harsh conditions of the Loch Lomond Stadial to the warmer climate of the early postglacial. However, our knowledge of this transition in south-east England has been hampered by the paucity of mires with sedimentary records spanning this period. We present two new high-resolution paleoenvironmental records from Langshot Bog and Elstead Bog B (Surrey, UK), which provide a clear signature of vegetation succession and fire history. Organic sedimentation at Langshot Bog commenced prior to 12,640–12,410 cal. BP (95% probability) and continued until 8430–8350 cal. BP (95% probability). Providing a robust chronology for Elstead Bog B proved to be problematic, although available dates suggest sediment accumulation commenced prior to 11,820–11,400 cal. BP (WM-168, 2σ). The sites are characterized by similar vegetation records, indicating a regional signal from locations over 20 km apart. Scrubby tundra-style vegetation is characteristic of cold conditions associated with the Lateglacial. The identification of Alnus and Corylus, taxa not normally associated with this period, indicates that microclimates may have permitted the survival of these species. Expansion of Betula followed by Pinus dates to the onset of the Holocene, forming mixed coniferous-deciduous woodland, during a period which is punctuated by short climatic events identified from stable isotope analysis. Subsequent expansion of thermophilous taxa Corylus, Ulmus and Quercus results in the formation of deciduous woodland. A rise in micro-charcoal, heathland and herbaceous taxa indicates development of heathy-scrubby clearings within this Holocene landscape.

Recent findings on the native status and vegetation ecology of Scots pine in Ireland and their implications for forestry policy and management

Article

Full-text available

Dec 2019

Jenni Roche

It has been generally accepted that Scots pine (Pinus sylvestris L.) became extinct in Ireland c. AD 400. The species was reintroduced in the mid-17 th century and has been widely planted. It has been included in the Native Woodland Scheme, which provides grants to establish or restore native woodlands. However, its native status in Ireland has been disputed and the vegetation ecology and conservation value of Irish pinewoods have been poorly understood. These knowledge gaps have been addressed using an approach combining vegetation ecology and palaeoecology. Vegetation surveys were conducted at eighteen pinewoods in Ireland and six in Scotland. Cluster analysis was used to evaluate the floristic similarity between plots and classify them into groups. One of the Irish pinewoods was of unknown origin (Rockforest, Co. Clare). To reconstruct its vegetation history, a sediment core was extracted from Rockforest Lough. Pollen, macrofossil and dating analyses were conducted. Cluster analysis identified four groups, representing distinct pinewood vegetation types. The vegetation of certain Irish groups and sites exhibited similarities with that of extant native pinewoods elsewhere in oceanic northwest Europe or fossil assemblages from ancient Irish pinewoods. While the vegetation of Irish pinewoods did not correspond to that of typical Scottish Caledonian forests, Coronation Plantation and the bog pinewoods at Clonfinane and All Saints Bog exhibited strong similarities with other native Scottish pinewoods of high conservation value. Natural regeneration of P. sylvestris was poor overall. The pollen diagram from Rockforest Lough showed a continuously high Pinus pollen frequency (38-51% of total terrestrial pollen) from c. AD 350 to the present. Macrofossil evidence demonstrated local presence of P. sylvestris around Rockforest Lough c. AD 840. The available historical sources indicated a long history of woodland cover at Rockforest. A separate analysis of a peat core from nearby Aughrim Swamp also showed a continuous Pinus signal from c. AD 350 to the present. The findings of the vegetation analysis suggest that P. sylvestris woodlands are an important resource for Irish biodiversity, particularly given the country's low native woodland cover. The palaeoecological data indicate that native P. sylvestris persisted at Rockforest from c. AD 350 to the present. The hypothesis that P. sylvestris became extinct in Ireland is rejected.

Resilience: nitrogen limitation, mycorrhiza and long-term palaeoecological plant–nutrient dynamics

Article

Full-text available

Jan 2020

Ecosystem dynamics are driven by both biotic and abiotic processes, and perturbations can push ecosystems into novel dynamical regimes. Plant-plant, plant-soil and mycorrhizal associations all affect plant ecosystem dynamics; however, the direction and magnitude of these effects vary by context and their contribution to ecosystem resilience over long time periods remains unknown. Here, using a mathematical framework, we investigate the effects of plant feedbacks and mycorrhiza on plant-nutrient interactions. We show evidence for strong nutrient controlled feedbacks, moderation by mycorrhiza and influence on ecological resilience. We use this model to investigate the resilience of a longitudinal palaeoecological birch-δ15N interaction to plant-soil feedbacks and mycorrhizal associations. The birch-δ15N system demonstrated high levels of resilience. Mycorrhiza were predicted to increase resilience by supporting plant-nitrogen uptake and immobilizing excess nitrogen; in contrast, long-term enrichment in available nitrogen by plant-soil feedbacks is expected to decrease ecological resilience.

New insights on stomata analysis of European conifers 65 years after the pioneering study of Werner Trautmann (1953)

Article

Full-text available

May 2020
VEG HIST ARCHAEOBOT

Conifer-stomata analysis is an essential part of the palaeoecological toolbox because it allows the determination of the local presence of plant populations with a lower degree of uncertainty than pollen analysis. Although the European postglacial pool of conifer taxa is broad, stomata morphologies for only few taxa have been investigated. Prior stomata morphology studies focused on taxa having wide distribution ranges in central and northern Europe, and stomata morphologies for taxa occurring in southern European and Northern African mountain regions have not yet been described. Here, we present a qualitative assessment of stomata morphologies for 40 taxa from eight genera (Cupressus, Juniperus, Abies, Cedrus, Larix, Picea, Pinus and Taxus) that are present on the European continent and the southern borderlands of the Mediterranean Basin, thereby broadening substantially both the regional and taxonomical coverage of this now 65-years old technique. We found that visual identification of conifer stomata does not allow species-level identifications, supporting the notion of genus-specific stomata morphologies found in prior studies. For each genus, we describe the stomata morphologies taking into account the varying shape of stomata features at different focusing levels. In addition, we provide stop-motion animations (publicly available at http://dx.doi.org/10.6084/m9.figshare.7165261) that may be useful tools for microscope analysts who wish to acquaint themselves with conifer-stomata analysis.

Post glacial migration of Scots pine from the refugium in eastern Ukraine

Article

Full-text available

Mar 2019

Post glacial migration of Scots pine

mtDNA in Scots pine

Article

Full-text available

Mar 2019

Darius Danusevicius

Abstract Several recent studies based on mitochondrial DNA markers suggested a northern refugium for Scots pine somewhere westwards of the southern part of the Ural Mountains. The objective of our study was to assess the mtDNA polymorphism of Scots pine at the Nad7-1 and Nad1-B/C loci with the aim of detecting the location of this northern glacial refugium and the associated post-glacial migration routes. We studied 54 populations densely covering the European part of Russia westwards of the Ural Mountains, but also populations from the Czech Republic, Poland, Sweden, Finland, Scotland, Georgia and eastern Siberia were included. For the Nad1-B/C locus, all our material was monomorphic. Of the total of 474 individuals tested at the Nad7-1 locus, 348 individuals (73 %) possessed the universal haplotype A of 300 bp and 126 individuals (27 %) - the northern haplotype B of 295 bp. Geographical distribution of the Nad7-1 northern B haplotype was not random (SAMOVA, BAPS) forming a consistent cline directed towards north-west of the south-eastern part of European Russia up to the Scandinavia in the north. This provides a stronger support for the south-eastern rather than the central European location of the northern glacial refugium. A possible location of the northern refugium could be at about 300 km south-east of Moscow, where the northern B haplotype occurs in high frequency and Scots pine could possible survive during the LGM. There also is a possibility for a more southern location of the northern refugium, assuming that such signature was lost during the northward migration or via genetic drift..

Palaeoecological Evidence for Survival of Scots Pine through the Late Holocene in Western Ireland: Implications for Ecological Management

Article

Full-text available

Jun 2018

The dynamics of Scots pine (Pinus sylvestris L.) in Europe during the Holocene have been spatially and temporally complex. The species underwent extirpation and reintroduction in several north-west European countries. This study investigated the late Holocene vegetation history of a present-day pinewood in western Ireland, to test the widely accepted hypothesis that P. sylvestris became extinct in Ireland c. AD 400. Palaeoecological, chronological and loss-on-ignition analyses were conducted on a sediment core extracted from an adjacent lake. The pollen profile showed no major Pinus decline and a Pinus macrofossil occurred c. AD 840, indicating localised survival of P. sylvestris from c. AD 350 to the present. The available archival maps and historical literature provide supporting evidence for continuity of forest cover. The hypothesis that P. sylvestris became extinct in Ireland is rejected. The implications for ecological management are significant. We argue that P. sylvestris should be considered native to Ireland, at least at this site. As Ireland's only putative native P. sylvestris population and the western limit of the species' native range, this site is of high conservation value and must be carefully managed and monitored. Seed-sourcing for ex-situ forest restoration must be compatible with the long-term viability of the population in-situ.

International Journal of Current Multidisciplinary Studies

Article

Full-text available

May 2018

Leif Kullman

Climate warming and associated post-Little Ice Age recession of glacier ice and permanent snow in high mountains of the Swedish Scandes have opened a new view for alpine palaeoecology. Receding glaciers and snow/ice patches, high above current tree-lines of all boreal tree species, have exposed forefields with a plethora of megafossil tree remnants, representing discrete multi-species tree groves. Radiocarbon-dating of associated wood debris offers new insight into the early Holocene structure and species composition of the tree-line ecotone. The emerging pattern deviates substantial from the conventional view, deduced from the pollen stratigraphical approach, which needs to be questioned in general, both with respect of tree-line reconstruction and in the context of more general biogeographic evolution. Boreal tree species were present in the concerned settings from late-glacial, 16 800 cal. yr BP to the late Holocene, about 4000 cal. yr BP. The frequency of megafossil tree remains peaked 9600-900 cal. yr BP, maximum 600-700 m above modern tree-lines. This implies (corrected for land uplift) that the summer temperatures may have been 3 °C warmer than current standards. The postglacial immigration history of Picea abies to the Scandes, a stumbling stock in Scandinavian palaeobiogeography, is at least 8000 years prior to traditional text book narrative. Discrete tree groves in empty glacier cirques and snow hollows may have played an important role as dispersal nodes for the postglacial afforestation of the mountain landscape. In addition, the results add to the increasingly recognized view that Larix sibirica, an eastern species, currently not native to Scandinavia, prevailed quite frequently at high elevations during the early Holocene. Further shortcomings of traditional methods of vegetation reconstruction are provided when viewed in perspective of megafossil analyses, which support a relatively firm framework on which the detailed vegetation history can be built.

Microclimate variability and long-term persistence of fragmented woodland

Article

Full-text available

Jul 2017
BIOL CONSERV

Favourable microclimates are predicted to buffer fragmented populations against the effects of environmental change, but ecological timeseries are often too short to establish the extent to which such microsites facilitate population persistence through multiple climate shifts. We investigate the effects of microclimatic heterogeneity on woodland resilience through millennial climate and disturbance shifts near northwest European woodland range limits. We use palaeoecological data from northern Scotland to study the effects of fragmentation on community composition and diversity in a potentially favourable microclimate, and compare palynological timeseries of tree abundance from five sites to assess the effects of favourable (low-lying sheltered) versus more marginal (higher altitude) settings on population persistence and stability. The sheltered site shows persistence of tree cover through Holocene climatic and anthropogenic shifts, including climatically-driven regional woodland contraction around 4400 cal BP (calendar years before present), when surviving woods became compositionally differentiated into upland pine and low-lying deciduous communities. A favourable microclimate can thus buffer woodlands against environmental shifts and increase continuity of canopy cover, but it does not generate stable communities. Compositional reorganisation is an essential stress response mechanism and should be accommodated by conservation managers. The replacement of deciduous taxa by Pinus sylvestris after 1060 cal BP represents the decoupling of pine distribution from climate drivers by management intervention. As a result, current microrefugial woodland composition reflects late Holocene human intervention. Alternative models of community composition and behaviour from palaeoecology provide a stronger foundation for managing microsite communities than relict woods in contrasting environmental settings.

Predicting Pleistocene climate from vegetation

Article

Full-text available

Oct 2006
CPD

Craig Loehle

Climates at the Last Glacial Maximum have been inferred from fossil pollen assemblages, but these inferred climates are colder than those produced by climate simulations. Biogeographic evidence also argues against these inferred cold climates. The recolonization of glaciated zones in eastern North America following the last ice age produced distinct biogeographic patterns. It has been assumed that a wide zone south of the ice was tundra or boreal parkland (Boreal-Parkland Zone or BPZ), which would have been recolonized from southern refugia as the ice melted, but the patterns in this zone differ from those in the glaciated zone, which creates a major biogeographic anomaly. In the glacial zone, there are few endemics but in the BPZ there are many across multiple taxa. In the glacial zone, there are the expected gradients of genetic diversity with distance from the ice-free zone, but no evidence of this is found in the BPZ. Many races and related species exist in the BPZ which would have merged or hybridized if confined to the same refugia. Evidence for distinct southern refugia for most temperate species is lacking. Extinctions of temperate flora were rare. The interpretation of spruce as a boreal climate indicator may be mistaken over much of the region if the spruce was actually an extinct temperate species. All of these anomalies call into question the concept that climates in the zone south of the ice were very cold or that temperate species had to migrate far to the south. Similar anomalies exist in Europe and on tropical mountains. An alternate hypothesis is that low CO2 levels gave an advantage to pine and spruce, which are the dominant trees in the BPZ, and to herbaceous species over trees, which also fits the observed pattern. Most temperate species could have survived across their current ranges at lower abundance by retreating to moist microsites. These would be microrefugia not easily detected by pollen records, especially if most species became rare. These results mean that climate reconstruction based on terrestrial plant indicators will not be valid for periods with markedly different CO2 levels.

Early- to mid-Holocene forest-line and climate dynamics in southern Scandes mountains inferred from contrasting megafossil and pollen data

Article

Full-text available

Aug 2016

The result of 344 radiocarbon-dated megafossils is here presented and discussed. This study aims at elucidating early- to mid-Holocene forest-line and climate dynamics in the southern Scandes along a present gradient of decreasing forest-line elevations. Around 9.5 calibrated ka before present (BP), pine suddenly established vertical belts of at least 200 m. These represent the highest pine-forests during the Holocene, ca. 210–170 m higher than today when corrected for land uplift. By this, summer temperatures at least 1–1.3°C warmer than today are indicated for the early Holocene thermal maximum around 8.5–9.5 cal. ka BP. The most pronounced warming occurred in Jotunheimen, the highest mountain range in Scandinavia, because of an amplified ‘Massenerhebung’ effect. Megafossils show the establishment of birch-forests above pine-forests already from the early Holocene. Pine-forests started their decline in the early Holocene and became replaced by the less warmth-demanding birch-forests. Pine megafossil results and pollen studies from the same areas show that cooling around 8.5 cal. ka BP caused a significant decrease in pine pollen production whereas pine-forest-lines were more or less unaffected. In the following period of about 2000 years, the high-altitudinal pine-forests could hardly be detected in pollen diagrams. This shows how strongly past temperatures influenced on the pollen production of individuals and how this might obscure pollen-based reconstructions of past vegetation. To be able to correct for this error, there is a need for establishing exact present-day relationships between temperature and pollen production of prolific pollen producers.

A key for the identification of conifer stomata from N.E. China based on fluorescence microscopy

Article

Jun 2016
REV PALAEOBOT PALYNO

Stomata analysis is an important tool for palaeoecological and palaeoenvironmental research. Coniferous stomata are lignified and similar in size to pollen grains. Detached from the epidermis, individual stomata can be preserved in Quaternary sediments and are often found in palynological preparations. Their identification is important for environmental and climatic interpretation. By using macrofossil remains of needle leaves and fresh needle leaves, in this study a regional identification key to the species level for coniferous stomata from Long Gang Volcanic Field (N.E. China, Jilin Province) is presented. For the microscopic investigations and the measurement of stomatal features, fluorescence techniques were applied. Three types of fluorescence filter sets using ultraviolet (UV), blue, and triple mixed excitation wavelengths were employed. To test the key and the fluorescence effect with fossil material, individual stomata from palynological slides were studied. Our results show that individual stomata have similar fluorescence to those in situ on macrofossil needles. For future stomata research, fluorescence microscopy using blue light excitation is strongly recommended.

The Location of the Northern Glacial Refugium of Scots Pine Based on Mitochondrial DNA Markers

Article

Full-text available

Jan 2013

Several recent studies based on mitochondrial DNA markers suggested a northern refugium for Scots pine somewhere westwards of the southern part of the Ural Mountains. The objective of our study was to assess the mtDNA polymorphism of Scots pine at the Nad7-1 and Nad1-B/C loci with the aim of detecting the location of this northern glacial refugium and the associated post-glacial migration routes. We studied 54 populations densely covering the European part of Russia westwards of the Ural Mountains, but also populations from the Czech Republic, Poland, Sweden, Finland, Scotland, Georgia and eastern Siberia were included. For the Nad1-B/C locus, all our material was monomorphic. Of the total of 474 individuals tested at the Nad7-1 locus, 348 individuals (73 %) possessed the universal haplotype A of 300 bp and 126 individuals (27 %) - the northern haplotype B of 295 bp. Geographical distribution of the Nad7-1 northern B haplotype was not random (SAMOVA, BAPS) forming a consistent cline directed towards north-west of the south-eastern part of European Russia up to the Scandinavia in the north. This provides a stronger support for the south-eastern rather than the central European location of the northern glacial refugium. A possible location of the northern refugium could be at about 300 km south-east of Moscow, where the northern B haplotype occurs in high frequency and Scots pine could possibly survive during the LGM. There also is a possibility for a more southern location of the northern refugium, assuming that such signature was lost during the northward migration or via genetic drift.

Pine stumps in Irish peats: Is their occurrence a valid proxy climate indicator?

Article

Jul 2015
J QUATERNARY SCI

We investigate the temporal and spatial distribution of pine (Pinus sylvestris) stumps preserved in peat deposits to test whether their occurrence can be used as an indicator of climatic shifts to drier conditions. Radiocarbon dates of sub-fossil stumps were collected from the literature, along with environmental data throughout the island of Ireland. Data were analysed using non-parametric statistical techniques. There was no distinct geographical pattern observed in the distribution of pine stumps on bog surfaces. Tree ages ranged from 66 to 500 years with 85.7 % of these <300 years. Pines occurred on bogs from ca. 8500 to 500 cal a BP. The temporal distribution during the Holocene was characterized as a mid-Holocene peak in sites supporting pine, with two gaps either side of this peak. Our current understanding of past climate dynamics failed to explain this temporal distribution. The onset, mid-Holocene peak and cessation of bog sites supporting the presence of bog pines appears to be driven by changes in pine seed and bog surface area availability during the Holocene rather than changes in climate. We conclude that variability in the occurrence of Irish bog pines is not a valid climate proxy as factors other than climate influence their presence and thereby disrupt the climate signals.

Ecology of Scots pine (Pinus sylvestris L.) in Ireland - preliminary results

Article

Jan 2008

Later prehistoric vegetation dynamics and Bronze Age agriculture at Hobbister, Orkney, Scotland

Article

Full-text available

Jul 2015

Michelle Farrell

The Bronze Age in Britain was a time of major social and cultural changes, reflected in the division of the landscape into field systems and the establishment of new belief systems and ritual practices. Several hypotheses have been advanced to explain these changes, and assessment of many of them is dependent on the availability of detailed palaeoenvironmental data from the sites concerned. This paper explores the development of a later prehistoric landscape in Orkney, where a Bronze Age field system and an apparently ritually-deposited late Bronze Age axehead are located in an area of deep blanket peat from which high-resolution palaeoenvironmental sequences have been recovered. There is no indication that the field system was constructed to facilitate agricultural intensification, and it more likely reflects a cultural response to social fragmentation associated with a more dispersed settlement pattern. There is evidence for wetter conditions during the later Bronze Age, and the apparent votive deposit may reflect the efforts of the local population to maintain community integrity during a time of perceptible environmental change leading to loss of farmland. The study emphasises the advantages of close integration of palaeoenvironmental and archaeological data for interpretation of prehistoric human activity. The palaeoenvironmental data also provide further evidence for the complexity of prehistoric woodland communities in Orkney, hinting at greater diversity than is often assumed. Additionally, differing dates for woodland decline in the two sequences highlight the dangers of over-extrapolation from trends observed in a single pollen profile, even at a very local scale.

Adaptive genetic variation in Scots pine (Pinus sylvestris L.) in Scotland

Article

Nov 2011

Matti J Salmela

Genetic differentiation in phenotypic traits among populations from heterogeneous environments is often observed in common-garden studies on forest trees, but data on adaptive variation in Scots pine (Pinus sylvestris L.) in Scotland are limited. As a result, current seed transfer guidelines are based on earlier molecular marker studies and do not take into account environmental or adaptive genetic variation. An analysis of spatial variation in climate showed substantial differences in temperature and precipitation among the native Scots pine sites in Scotland. To investigate whether differentiation in response to environmental variation has occurred in Scotland, a glasshouse-based common-garden trial of ~3,360 seedlings from 21 populations and 84 open-pollinated families was established in 2007. At the beginning of the 2nd growing season, timing of bud flush showed evidence of genetic differentiation among populations, with those from cooler origins generally flushing earlier. Variation was also found among families within populations, suggesting that the trait is genetically controlled. Populations and families showed different levels of variability in this trait which could be partly due to variable levels of temporal climate fluctuation in different parts of Scotland. Chlorophyll fluorescence was used to examine drought response in three-year old seedlings from five populations on sites that experience contrasting levels of annual rainfall. It was found that the response was not related to rainfall, but possibly to more complex moisture variables that also take into account additional factors such as evaporation. Also, photosynthetic capacity in response to cold winter temperatures varied significantly among eight populations that were kept outdoors, and the largest reduction was seen in seedlings from the mildest, most maritime coastal site. The following spring, height growth and needle flush started earlier in seedlings from cooler locations. Earlier studies on genetic diversity of native pinewoods have shown high levels of selectively neutral variation in this predominantly outcrossing conifer, and a mating system analysis with a limited number of microsatellite markers supported this pattern. Together, these data suggest that despite significant historic population size decrease, environmental gradients have resulted in genetic differentiation among native pinewoods. In order to minimise the risk of planting poorly-adapted stock and to maximise the success of replanting programmes, it is important that the origins of planting stock are carefully considered in management guidelines for the species.

The stability of the Pinus sylvestris treeline in the Cairngorms, Scotland over the last millennium

Article

Mar 2013

Background : Changes in climate and recent land use have been related to treeline advances in many alpine and arctic regions. Short-term (Pinus sylvestris treeline in the Cairngorms, Scotland, where a natural treeline at ca. 650 m is thought to exist at Creag Fhiaclach. Aim : We demonstrate that treeline position can be determined from an altitudinal sequence of quotients of treeline tree pollen and dwarf-shrub pollen and therefore past treeline dynamics can be deduced from quotients of the same pollen types determined from dated peat strata. Methods : Modern pollen was extracted from moss cushions and replicate peat cores were taken for pollen analysis at each of six elevations, from below the treeline at 606 m to about 100 m above the treeline at 758 m. Ratios of Pinus sylvestris to Calluna vulgaris pollen were calculated after complete pollen analysis of each of the cores and radiocarbon dating. Results : In the modern pollen most palynomorphs (96%) were either of Pinus or Calluna. The pollen analysis extracted and identified 26 palynomorphs from peat. The ratios of Pinus/(Pinus+Calluna) pollen in the sampled elevation belts suggested a relative stability of today's treeline for about the last 1000 years. Conclusions : The observed stability of treeline elevation is likely to have been caused by site conditions and land-use history (windiness, fire and grazing) that overruled a simple climate–elevation relationship. †Deceased

Rewilding – A New Paradigm for Nature Conservation in Scotland?

Article

Full-text available

Mar 2012

Rewilding is a strategy for the conservation of complete, self-sustaining ecosystems, primarily involving the protection and, where necessary, reintroduction, of populations of keystone species in large, connected reserve networks. A potential method of preserving ecosystem functions and biodiversity, it is now receiving a great deal of practical and political attention, particularly in North America. In Scotland, where many native species have been extirpated in the relatively recent past, rewilding has clear relevance and may provide an overarching set of objectives for current programmes of native woodland restoration and species reintroductions. Nevertheless, rewilding is not widely used as a term or strategy in Scottish conservation. This review considers the development of the concept and its possible application in Scotland, and identifies substantial scope for rewilding, in terms of the restoration and protection of large areas of wild land, and of the reintroduction of native species which have been driven to extinction by human activity. As the environmental, social and economic benefits which are likely to result from a programme of rewilding in Scotland outweigh the potential drawbacks, the adoption of rewilding is recommended as one aim of environmental policy.

Holocene distribution of woody taxa at the westernmost limit of the Circumboreal/Mediterranean boundary: Evidence from wood remains

Article

Feb 2012
QUATERNARY SCI REV

García-Amorena I, Morla C, Rubiales JM, Gómez-Manzaneque F.. Taxonomic composition of the Holocene forests or the northern coast of Spain, as determined from their macroremains. Holocene 18: 819-829

Article

Full-text available

Aug 2008

Eight sites distributed over a distance of some 400 km of the Cantabrian coast (northern Spain) provided 153 wood, 50 fruit and over 350 leaf remains belonging to the area's Holocene forests. The high taxonomic precision with which these macroremains were identified (in many cases at the species level), plus the accurate information available regarding the original growth locations of these plants, provide new geobotanical insights into the history of northern Spain's Atlantic forests. Radiocarbon dating of the wood samples showed the collected material to have lived between 8550 and 800 cal. BP. Analysis of the macroremains showed the deciduous mixed forests of the Holocene to contain a majority of Quercus robur and Corylus avellana, accompanied by Acer pseudoplatanus, Ulmus minor, Castanea sp., and hygro-thermophilous taxa (Arbutus, Laurus and Vitis vinifera). The remains of hygrophilous communities, dominated by Salix atrocinerea, Alnus glutinosa and Fraxinus sp., show these to have expanded during the Holocene. The absence of conifer macroremains is interpreted as reflecting the disappearance of Würmian conifer populations at the beginning of the Holocene. The different taxa (eg, Ilex spp. and V. vinifera) that survived the last glaciation in the refugia offered by Spain's northern coast persisted in the same areas during the Holocene. A leaf sample of Ulmus minor dating to 3950 ±120 cal. BP reveals for the first time the natural occurrence of this species on the northern coast of Spain.

Holocene transgression recorded by sand composition in the mesotidal Galician coastline (NW Spain)

Article

Full-text available

Apr 2010

This study confirms several inferences regarding Holocene coastal dynamics and climate through a petrographic modal analysis of 60 Holocene sand samples recovered in seven sites along the NW coast of the Iberian Peninsula. Fluvial sand can be discriminated from more mature intertidal and aeolian sand according to texture and composition. Fluvial sand contains soil products and coastal sand has significant bioclasts. Quartzofeldspathic sand appears in the western area (produced by the erosion of granite and granitoid), and quartzolithic sand occurs in the eastern area (produced by the erosion of metasediment). Changes in sand composition during Holocene deposition are manifested by an increase in modern carbonate clasts (MC) correlated with the Holocene transgression. Episodes of faster sea-level rise and subsequent erosion of surrounding cliffs are indicated by the preservation of high proportions of feldspar in intertidal sand. In contrast, fluvial sand is characterized by greater quartz enrichment. These inferences were confirmed by petrographic indices (carbonate clasts/total clasts, MC/T; total feldspars/monocrystalline quartz, F/Qm; and plagioclase/total feldspars, P/F). The different maturity of intertidal and aeolian sands is revealed by their variable quartz contents, despite similar proportions of plagioclase and K-feldspar. This suggests mechanical abrasion as the main factor controlling maturity. In contrast, fluvial sand shows depleted plagioclase contents as the result of inland weathering processes. Intertidal, beach and aeolian sands are essentially the products of the erosion of coastal cliffs and head deposits, with only the scarce contribution of fluvial drainages. The long-distance transport of Galician coastal sands is discarded based on the close relationship between their composition and that of local sand sources. Our findings indicate that short-distance transport of sediments from the west closed off coastal wetlands and occluded estuarine mouths during the Holocene transgression by deposition on sediment-trap zones along the irregularly shaped Galician coast.

Alpines, trees, and refugia in Europe

Article

Nov 2008

Katherine J Willis

Refugia were critically important for species survival in both glacial and interglacial stages of the Quaternary. The classical view of glacial stages is that alpine and arctic plants were widespread in the lowlands of central Europe and around the margins of the continental and alpine ice-sheets, whereas trees were restricted to localised refugial areas in southern Europe and the Mediterranean basin. New palaeobotanical evidence in Europe suggests, however, that this classical view is incomplete and that tree distributional ranges during the glacial stages were more extensive and included many local areas of small populations in central and eastern Europe growing in so-called ‘cryptic’ refugia. We argue that this concept of ‘cryptic’ refugia is also applicable to arctic and alpine plants during temperate interglacial stages where small localised populations grow in naturally open habitats that are not beyond or above the forest limit. Determination of the whereabouts of these cold- and warm-stage ‘cryptic’ refugia is very important in our understanding of the spatial patterns of present day genetic diversity and the possible rates of spread of trees in response to future climate change.

Negative responses of highland pines to anthropogenic activities in inland Spain: A palaeoecological perspective

Article

Aug 2012

Palaeoecological evidence indicates that highland pines were dominant in extensive areas of the mountains of Central and Northern Iberia during the first half of the Holocene. However, following several millennia of anthropogenic pressure, their natural ranges are now severely reduced. Although pines have been frequently viewed as first-stage successional species responding positively to human disturbance, some recent palaeobotanical work has proposed fire disturbance and human deforestation as the main drivers of this vegetation turnover. To assess the strength of the evidence for this hypothesis and to identify other possible explanations for this scenario, we review the available information on past vegetation change in the mountains of northern inland Iberia. We have chosen data from several sites that offer good chronological control, including palynological records with microscopic charcoal data and sites with plant macro- and megafossil occurrence. We conclude that although the available long-term data are still fragmentary and that new methods are needed for a better understanding of the ecological history of Iberia, fire events and human activities (probably modulated by climate) have triggered the pine demise at different locations and different temporal scales. In addition, all palaeoxylological, palynological and charcoal results obtained so far are fully compatible with a rapid human-induced ecological change that could have caused a range contraction of highland pines in western Iberia.

Macrofossil evidence of alder (Alnus sp.) in Britain early in the Late Glacial Interstadial: implications for the northern cryptic refugia debate

Article

Full-text available

Oct 2020
J QUATERNARY SCI

Wood macrofossil remains of alder and willow/poplar have been recovered from a sediment sequence in the valley of the Turker Beck in the Vale of Mowbray, North Yorkshire. These remains have yielded radiocarbon dates early in the Devensian Late Glacial (14.7-14k cal a BP), equivalent to the early part of the Greenland Interstadial (GI-1e) of the GRIP ice-core record. These are the earliest dates recorded for the presence of alder in the Late Glacial in the British Isles. Associated biological remains have provided a palaeoenvironmental record for this early part of the Greenland Interstadial, generally indicative of open environments dominated by herbaceous taxa on both the wetland and dryland surfaces. However, stands of alder, birch and willow woodland were also present, and indicate the possibility that such tree species survived in cryptic refugia in Britain as elsewhere in northern Europe during the Last Glacial Maximum. The absence of alder pollen at Turker Beck, in a sequence in which its macrofossil remains are relatively abundant, lends support to the view that pollen can be a poor indicator of the presence of tree species in Late Glacial sequences in northern and western Europe.

Evidence of wildfire in the British Isles during the Last Glacial-Interglacial Transition: Revealing spatiotemporal patterns and controls

Article

May 2020
P GEOLOGIST ASSOC

Charcoal records are now widely used to reconstruct past burning activity as there is an increasing global interest in understanding the complex interactions between fire, climate, vegetation and human activity. However, this topic has been relatively overlooked in the British Isles, as the region is generally thought to not support natural burning regimes. Here, for the first time, we present a synthesis of previously published charcoal data for 238 sites and demonstrate the widespread occurrence of charcoal in sediments that span the Last Glacial-Interglacial Transition (LGIT; c. 17-8.3 ka cal. BP) in the British Isles. Analysis is based upon a semi-quantitative analysis of the assembled dataset; the common patterns are identified and are considered in relation to independent reconstructions of climate, vegetation and anthropogenic activity. No causal relationships with vegetation are identified, while charcoal is also prominent during periods when archaeological evidence for human occupation of the British Isles is absent or scarce. Climate is very likely to have controlled the fire regimes during the LGIT. We conclude with ten research priorities to further advance our understanding palaeofire drivers during the Lateglacial-Early Holocene.

Contributions of Quaternary botany to modern ecology and biogeography

Article

Full-text available

May 2019

Harry John B Birks

Quaternary (last 2.6 million years) botany involves studying plant megafossils (e.g. tree stumps), macrofossils (e.g. seeds, leaves), and microfossils (e.g. pollen, spores) preserved in peat bogs and lake sediments. Although megafossils and macrofossils have been studied since the late eighteenth century, Quaternary botany today is largely dominated by pollen analysis. Quaternary pollen analysis is just over 100 years old. It started primarily as a geological tool for correlation, relative dating, and climate reconstruction. In 1950 a major advance occurred with the publication by Knut Fægri and Johs Iversen of their Text-book of Modern Pollen Analysis which provided the foundations for pollen analysis as a botanical and ecological tool for studying past dynamics of biota and biotic systems. The development of radiocarbon dating in the 1950s freed pollen analysis from being a tool for relative dating. As a result of these developments, pollen analysis became a valuable implement in long-term ecology and biogeography. Selected contributions that Quaternary botany has made to ecology and biogeography since 1950 are reviewed. They fall into four general parts: (1) ecological aspects of interglacial and glacial stages such as location and nature of glacial-stage tree refugia and long-term soil development in glaciated and unglaciated areas; (2) biotic responses to Quaternary environmental change (spreading, extinction, persistence, adaptation); (3) ecological topics such as potential niches, the nature of vegetation, and tree and forest dynamics; and (4) its application to ecological topics such as human impact in tropical systems, conservation in a changing world, island palaeoecology, plant–animal interactions, and biodiversity patterns in time. The future of Quaternary botany is briefly discussed and 10 suggestions are presented to help strengthen it and its links with ecology and biogeography. Quaternary botany has much to contribute to ecology and biogeography when used in conjunction with new approaches such as ancient-DNA, molecular biomarkers, and multi-proxy palaeoecology.

Plant controls on Late Quaternary whole ecosystem structure and function

Article

Full-text available

Mar 2018

Plants and animals influence biomass production and nutrient cycling in terrestrial ecosystems; however, their relative importance remains unclear. We assessed the extent to which mega‐herbivore species controlled plant community composition and nutrient cycling, relative to other factors during and after the Late Quaternary extinction event in Britain and Ireland, when two‐thirds of the region's mega‐herbivore species went extinct. Warmer temperatures, plant–soil and plant–plant interactions, and reduced burning contributed to the expansion of woody plants and declining nitrogen availability in our five study ecosystems. Shrub biomass was consistently one of the strongest predictors of ecosystem change, equalling or exceeding the effects of other biotic and abiotic factors. In contrast, there was relatively little evidence for mega‐herbivore control on plant community composition and nitrogen availability. The ability of plants to determine the fate of terrestrial ecosystems during periods of global environmental change may therefore be greater than previously thought.

La información taxonómica de caracteres epidérmicos en las acículas de los pinos ibéricos. Su aplicación al estudio de material fósil. [Taxonomic information of the epidermal features of the needles of Iberian pine trees. Application to fossil material.]

Thesis

Full-text available

Dec 2010

Salvia García Álvarez

Unlike pollen and wood remains, the cuticular analysis of leaf macroremains more commonly provides of specific taxonomic information. Although some leaf-based keys and descriptions are available to identify leaf remains (e.g. Fagaceae), needle fragments of Iberian pines cannot be identify to the species level due to the lack of detailed descriptions. Well preserved pine cuticles (and their stomata) are found in many Iberian palaeobotanical sites. This motivated our study to report the value of the epidermis of needles for taxonomic differentiation of the six species of Pinus that grow spontaneously in the Iberian Peninsula (P. uncinata Ramon ex DC., P. sylvestris L., P. nigra J.F. Arnold, P. pinaster Aiton, P. pinea L. and P. halepensis Mill). Based on the study of present pine populations, cuticular and stomatal analyses were performed. To ensure the applicability of the study on fossil leaves, the methodology was tested in Holocene material from two different Iberian sites. To define the sampling procedure, a pilot study was carried out on one population from each of the six taxa, where up to 17 variables were studied. A high variability was found within needles in comparison to the variability between needles from the same tree, or even between trees from the same population. Additionally, no significant differences were found between sun and shade needles from the same tree. Therefore, the final sample design was performed on three natural populations from each taxon across its worldwide distribution (including at least one Iberian locality). On each population, three trees were randomly sampled, studying three needles from each individual. Every leaf was macerated, cleaned, and mounted on slides for its study with the aid of the optical microscope. Epidermis and ten stomata were analyzed on every slide. Principal components analysis, cluster analyses and discriminant analyses were applied on every stomatal variable. Variance analyses were used for the study of the pore (epistomatal chamber opening) size. Additionally, the information provided by the scanning electron microscope improved the interpretation of the cuticular features. The number of subsidiary cells of the stomatal complex, their relative size, shapes and arrangements, and the size of the pore, allow five species/groups to be defined: P. sylvestris, P. pinaster, P. pinea, P. halepensis and P. gr. uncinata-nigra. The frequency of solitary lateral subsidiary cells and the pore size provide a means of distinguishing P. uncinata from P. nigra, although the results cannot be considered entirely reliable. Statistical analysis of the stomatal variables showed trends towards the taxonomic differentiation, but they provided modest likelihood results. The results of the cuticular analysis applied on needle remains from the two Holocene sites showed the suitability of our study for their taxonomic identification. Besides, cross section techniques were applied on needles with different preservation condition. The experiment showed the difficulty of obtaining un-deformed cross sections with degraded material. However, the information provided by the cross section is useful to distinguish between P. nigra and P. uncinata.

A taxonomic tool for identifying needle remains of south-western European Pinus species of the Late Quaternary

Article

Mar 2014
BOT J LINN SOC

This work provides a tool whereby the needle remains of native, south-western European Pinus spp. can be easily identified from species-specific epidermal features. To construct this tool, the needles of P. uncinata, P. sylvestris, P. nigra, P. pinaster, P. pinea and P. halepensis were gathered across the Northern Hemisphere range of each taxon and compared with non-indigenous trees growing in two South Australian Botanic Gardens. Three needles from each of these species were taken from three adult trees growing at three different localities. Light microscopy was used to observe the key epidermal and stomatal features of the needles. To improve interpretation, additional scanning electron microscopy samples were prepared. Epidermal features, including variation in the diameter of the epistomatal chamber aperture (pore), are described. A taxonomic key based on the size, shape and arrangement of the subsidiary cells of the stomatal complexes was constructed. This key enables the identification of pine needle fragments at the species level (except those belonging to the group P. gr. nigra-uncinata). Despite their overlapping range, pore size was helpful in distinguishing between P. nigra and P. uncinata and between three groups of species. Isolated stomata were also observed. Cluster and discriminant analyses of stomatal variables described in earlier studies were performed. Overlap in guard cell variables hampers species-level identification of isolated stomata. Species discrimination is improved if groups of ecological affinity are considered.

Holocene migration of lodgepole pine (Pinus contorta var. latifolia) in southern Yukon, Canada

Article

Sep 2013

A palynological reconstruction (n = 25 profiles) suggests that the northern extent of lodgepole pine (Pinus contorta var. latifolia Engelmann ex S. Watson) occurred between 59° and 60°N latitude in northwest North America from 10,000 to 7000 calendar years before present (cal. yr BP) prior to entering Yukon. Although specific migration pathways could not be resolved with the available palynological data, mountains along the southern edge of Yukon appear to have diverted lodgepole pine migration through the Carcross and Frances Lake areas in southwest and southeast Yukon, respectively. Migration in the southwest (70 m/yr) was likely confined to lower elevations of the Yukon and Teslin river valleys, with lodgepole pine reaching 61°N ~2000 cal. yr BP. Along the eastern route, migration was channeled through a 15–20 km wide pass in a 200 km mountainous front. After breaching the Liard drainage divide north of Frances Lake ~4000 cal. yr BP, migration progressed northwest (160–220 m/yr) along the Tintina Trench. Lodgepole pine was estimated to have reached its near present-day northern limit (~63°N) ~1790 cal. yr BP, which is ~1290 years earlier than previously thought. This difference in arrival dates is due the use of a >5% rather than a >15% pine pollen content threshold, which appears to correspond with >1% pine tree cover in the landscape. Climatic cooling after 1000 cal. yr BP that caused a population decline at higher elevations is hypothesized to explain the present-day sparse and disjunct distribution of pine across Yukon north of 61°N.

Relationships between vegetation and stomata, and between vegetation and pollen surface soil in Yunnan, Southwest China

Article

Full-text available

May 2013

Surface pollen and stomata of 61 samples collected in a study area ranging from tropical seasonal rainforest to oak forest (Quercus spinosa) in the Yulong Snow Mountain region in Yunnan, China, are used to distinguish vegetation communities. The results show that tropical seasonal rainforest (and mountain rainforest), south subtropical evergreen broad-leaved forest, and Quercus shrub are distinguished effectively from other vegetation types by analysis of surface pollen. The south subtropical evergreen broad-leaved forest, Pinus kesiya forest and evergreen broadleaf forest are distinguished effectively from other types of vegetation by pollen analysis. However, P. yunnanensis forest is not distinguished from other vegetation types, and P. armandii, P. densata forest and temperate deciduous conifer mixed forest are not distinguished. The over-representation of Pinus pollen is the main reason that these vegetation communities are not distinguished from each other. Conifer stomata analysis is an effective tool for identifying and distinguishing different types of coniferous forest, and this method performs well even with a small number of sampling points.

The pace of Holocene vegetation change – testing for synchronous developments

Article

Sep 2011

Comparison of pollen and stomata in late-glacial and early-holocene lake sediments from eastern Massachusetts

Article

Jun 2007

Conifer stomata analysis in paleoecological studies on the Loess Plateau: An example from Tianchi Lake, Liupan Mountains

Article

Nov 2011

The identification of fossil conifer stomata was conducted from a lake sedimentary sequence on the Liupan Mountains, southwestern Loess Plateau, in order to reconstruct detailed forest history and assess the potential of using stomata as a supplement to pollen analysis to determine the local presence of conifers over the last 3200 years. The pollen has already been analyzed in our previous study. Reference conifer stomata were prepared for the fossil stomata identification and demonstrate that the conifer stomata could be identified to at least genus level. Our stomata and pollen results reveal three clear stages of the forest recession during the late Holocene: mixed conifer-deciduous forest, steppe-forest and steppe. Combined stomata and pollen results confirm the local presence of conifer trees (Abies and Pinus) in the vicinity of the Tianchi Lake. Abundant Abies trees existed during 3200–2200 cal yr BP. Then it decreased and finally demised at ca.210 cal yr BP. Pinus trees have been continuously present with very low abundance throughout the late Holocene. Application of comprehensive studies comprising both stomata and pollen analyses allowed a detailed determination of the stages of conifer trees presence in the vicinity of the Tianchi Lake. Our study suggests that the analysis of fossil stomata is a valuable methodological tool for the provision of unambiguous evidence of the past local presence of the coniferous taxa in this region.

Discussion-Reporting of 14

Article

Full-text available

Jan 1977
RADIOCARBON

Count rates, representing the rate of 14 C decay, are the basic data obtained in a 14 C laboratory. The conversion of this information into an age or geochemical parameters appears a simple matter at first. However, the path between counting and suitable 14 C data reporting (table 1) causes headaches to many. Minor deflections in pathway, depending on personal interpretations, are possible and give end results that are not always useful for inter-laboratory comparisons. This discussion is an attempt to identify some of these problems and to recommend certain procedures by which reporting ambiguities can be avoided.

Comment on the post-glacial history of Pinus sylvestris in the British Isles

Article

Full-text available

Dec 1988
QUATERNARY SCI REV

Holocene changes in the vegetation of the Midwest

Article

Full-text available

Jan 1983

Documenting forest stand invasion: Fossil stomata and pollen in forest hollows

Article

Full-text available

Feb 2011
CAN J BOT

Tim Parshall

Stomata and pollen from forest hollow sediments in the Great Lakes were evaluated for their ability to document stand-scale forest invasion. In surface sediments of 19 forest hollows, stomate presence is related most closely to tree presence within 10-20 m for eastern hemlock (Tsuga canadensis (L.) Carr.), pine (Pinus spp. L.), balsam fir (Abies balsamea (L.) Mill.), and northern white cedar (Thuja occidentalis L.). Although the abundance of hemlock pollen in surface sediments is positively related to the abundance of hemlock trees within 100 m, it does not consistently reflect the presence of hemlock trees within this distance. Pollen and stomata preserved in forest hollow sediments from northwestern Wisconsin were used to document two stages of stand invasion by eastern hemlock. First, hemlock stomata initially appear approximately 2400 14C years BP, representing the initial colonization of the forest stand. Hemlock pollen also first appears at this time but in such low abundance that the presence of hemlock trees at the site cannot be known with certainty. Second, hemlock pollen percentages increase sharply around 350 14C years BP, approximately 2000 years following initial colonization, and represent an expansion of the local hemlock population not reflected by stomatal and needle abundance.

Late Glacial and Early Holocene Landscapes in Northern New England and Adjacent Areas of Canada

Article

Full-text available

May 1985

The landscapes of northern New England and adjacent areas of Canada changed greatly between 14,000 and 9000 yr B.P.: deglaciation occurred, sea levels and shorelines shifted, and a vegetational transition from tundra to closed forest took place. Data from 51 14C-dated sites from a range of elevations were used to map ice and sea positions, physiognomic vegetational zones, and the spread of individual tree taxa in the region. A continuum of tundra-woodland-forest passed northeastward and northward without major hesitation or reversal. An increased rate of progression from 11,000 to 10,000 yr B.P. suggests a more rapid warming than in the prior 2000–3000 yr. Elevational gradients controlled the patterns of deglaciation and vegetational change. The earliest spread of tree taxa was via the lowlands of southern Vermont and New Hampshire, and along a coastal corridor in Maine. Only after 12,000 yr B.P. did the taxa spread northward through the rest of the area. Different tree species entered the southern part of the area at different times and continued their spread at different rates. The approximate order of arrival follows: poplars (13,000–12,000 yr B.P. in the south), spruces, paper birch, and jack pine, followed by balsam fir and larch, and possibly ironwood, ash, and elm, and somewhat later by oak, maple, white pine, and finally hemlock (10,000–9000 yr B.P. in the south).

Holocene changes in the vegetation of the Midwest.

Article

Jan 1984

Only since 1960 has a data base accumulated that contains enough radiocarbon dates to permit study of the timing and spatial patterns of the changes. In the northern Midwest, the network of radiocarbon-dated pollen diagrams is now sufficiently dense that the pollen data can be mapped in a form that reveals the patterns of past vegetation. -from Authors

Holocene vegetational history of the eastern United States

Article

Jan 1983

M.B. Davis

Reporting of 14C data

Article

Jan 1977
RADIOCARBON

Analysis of fossil stomata of conifers as indicators of the Alpine tree line fluctuations during the Holocene

Article

Jan 1994

Late- and post-glacial macrophytic vegetation in the lochs of northern Scotland

Article

Jan 1968

Late-glacial and Holocene vegetation history of western Donegal, Ireland

Article

Jan 1994
BIOL ENVIRON

J. A. Fossitt

Zur Unterscheidung fossiler Spaltöffnungen der mitteleuropäischen Coniferen

Article

Dec 1953
FLORA

Werner Trautmann

Postglacial migration history of lodgepole pine near Yakutat, Alaska

Article

Jan 1991
CAN J BOT

Dorothy M. Peteet

Pollen stratigraphy from three peat sections near Yakutat suggests that lodgepole pine only recently arrived in SE Alaska. In contrast with this palynological interpretation, however, are Pinus contorta macrofossils that are present throughout one entire peat core. 14C dating by accelerator mass spectrometry confirms the establishment of lodgepole pine in this region of Alaska c10 000 BP. Results imply that the use of assigned pollen percentages to indicate the presence of a species within a region may not be valid, particularly where a species is at the edge of its geographic range. Data suggest either a late Wisconsin refugium for this pine in SE Alaska or extremely rapid late-glacial coastal migration northwestward following ice retreat. -from Author

Pollen evidence for the postglacial origins of Nova Scotia's forests.

Article

Jan 1987
CAN J BOT

David G. Green

Pollen diagrams from sites in SW Nova Scotia and close to the New Brunswick-Nova Scotia border show that after retreat of the Wisconsin ice sheets, most tree taxa arrived in the extreme SW of Nova Scotia earlier than anywhere else in the province. For most tree taxa, arrival times at sites in maritime Canada and in NE New England are consistent with very early dispersal of individuals along the coastal strip via the exposed coastal shelf and with their entering Nova Scotia from the SW. These scattered pioneer populations acted as centres for major population expansions, which followed much later in some cases. Local environments, fire, and interspecies competition appear to have been more important than propagule dispersal rates as factors limiting the spread of most taxa. -Author

Holocene vegetation history of the eastern United States

Article

Jan 1984

M.B. Davis

Reproduces and describes pollen diagrams and maps showing the migration of species. Spruce developed over quite large areas about 12 000 BP, no doubt as a result of climatic amelioration. 5000 BP vegetation throughout the south changed from oak forest to forest dominated by pine, and in the north vegetation changes suggested the peak of Holocene climatic warmth had passed. A useful stratigraphic marker is the hemlock decline at 4800 yr BP. -K.Clayton

Post-glacial dynamics of pine (Pinus sylvestris L.) and pinewoods in Scotland

Article

Jan 1995

Keith David Bennett

Scots pine populations in Scotland during the last 11 000 yr had at least two origins of which at least one may have been within the British Isles during the last glacial maximum. Populations increased in abundance early in the Holocene in southwest Scotland, but then decreased as a result of competition from broadleaved trees, especially oak (Quercus) and alder (Alnus glutinosa) Pine spread across most of Scotland by about 4400 yr ago, favoured by human activity after 5700 yr ago. It was, at that time, the only tree to increase its range as the overall extent of woodland in northern and western Scotland contracted. The "pine decline' at about 4400 yr ago was irregular and patchy in space and time, possibly a consequence of climatic variation, -from Author

An Atlas of Past and Present Pollen Maps for Europe: 0-13000 Years Ago, and The Overlay Maps.

Article

Nov 1984

Flandrian Alnus: Expansion or Immigration?

Article

Sep 1987

Whilst there is much evidence for the increasing abundance of Alnus in the pollen record of the Flandrian at c7500-5000 BP, there is little regarding the presence of the tree in the British Isles prior to that time. Thus it has been hard to determine whether the increase in Alnus represents an expansion of existing populations or an immigration from refugia. Evidence here suggests the existence of Alnus throughout the late-glacial and early Flandrian period at a site in N Humberside. -Authors

New and Firm Evidence for Mid-Holocene Appearance of Picea Abies in the Scandes Mountains, Sweden

Article

Jun 1995

Leif Kullman

1 A subalpine clonal population of Picea abies in the Scandes Mountains (Sweden) was analysed with respect to age structure, height and radial growth, foliage vigour and radiocarbon dates of subfossil wood fragments. 2 A tree-ring chronology yielded consistently low annual increments from AD 1600 to the mid-1800s. Subsequently, radial growth, initiation of new stems and height growth increased in accord with climate warming and possibly deeper snow cover. The growth form changed from krummholz to erect tree-size. During the past c. 50 years growth has declined and supra-nival stems have eroded. The reason is climate cooling mediated by the complex temperature/snow cover/ground frost, which appears as a critical determinant of the Holocene Picea spread. 3 Subfossil Picea wood was dated to c. 4800--4700 radiocarbon years BP (two dates), i.e. Picea grew here more than 2000 years prior to inferences from pollen data. Obviously, stray finds of pollen may represent local presence and it is hypothesized that Picea immigrated to specific microhabitats even earlier than the date established here, possibly soon after the regional deglaciation. Much later it could spread regionally as climate gradually became less seasonal, damper and more snow-rich, in response to orbital forcing of insolation. 4 Early immigration, well before local or regional dominance, precludes migrational lag and rather suggests that in a landscape perspective a dynamic equilibrium between Picea abundance and climate has existed for most of the Holocene. The elevational range-limit, however, may have been out-of-phase with climate for centuries or millennia, tuned to climate mainly by phenotypic responses.

The Spread of Fagus grandifolia Across Eastern North America During the Last 18 000 years

Article

Mar 1985

Keith David Bennett

Recognition of the distinction between population expansion and arrival of a species is crucial for interpreting pollen diagrams. F. grandifolia probably occurred during the Wisconsin full-glacial (18 000 BP) as a scarce tree over much of SE North America, and did not have a localized 'refugium'. By 14 000 BP it had begun spreading north, still at very low population densities. Between 14 000 and 10 000 BP it reached high densities locally in the southeast, probably as the result of population expansion while the climate was temporarily favourable. F. grandifolia had reached approximately to its present geographic limits by 7000 BP, but continued to spread, at a lower rate, in some areas until the present. The E Great Lakes region, where F. grandiflora is most abundant today, had the most rapid population expansions, at c7000 BP, attributed to locally favourable environmental conditions. The spread of F. grandifolia across the continent was achieved at very low population densities. The detection and tracking of such a spread is only marginally possible with current pollen-analytical techniques. -from Author

Extended 14C data base and revised CALIB 3.0 14C age calibration program

Article

Jan 1993
RADIOCARBON

The Age Calibration Program, CALIB, published in 1986 and amended in 1987 is here amended anew. The program is available on a floppy disk in this publication. The new calibration data set covers nearly 22 000 Cal yr (approx 18 400 14C yr) and represents a 6 yr timescale calibration effort by several laboratories. The data are described and the program outlined. -K.Clayton

Calculation of pollen and spore density in sediments by addition of exotic pollen in known quantities

Article

Jan 1962

W. S. Benninghoff

The Patterns of Post-Glacial Spread of White Spruce

Article

Nov 1986
J BIOGEOGR

Comparison of the pollen and macrofossil records from E, central and W Canada and adjacent United States reveals that while the post-glacial spread of Picea glauca was a more or less continuous, time-transgressive process in the first 2 regions, it was extremely rapid in the Western Interior. New data from N Alberta and the Northwest Territories show that white spruce spread across the 2000 km from S-central Alberta to the Mackenzie Delta area during c1000 yr. Analysis of fossil dunes in northwest Saskatchewan and a recent palaeoclimate simulation experiment provide a possible explanation, as both propose that surface winds in the Western Interior had a strong southern component at c9000 yr BP. These winds, and the flat, open terrain could have effected the rapid seed dispersal over large distances required to explain the apparent rate of spread.-from Authors

Forest succession. Concepts and application

Article

Dec 1983
BIOL CONSERV

E.D.

Conifer stomate analysis as a paleoecological tool: An example from the Hudson Bay Lowlands

Article

Feb 1995

Barbara C. S. Hansen

The identification of conifer stomata in fossil pollen preparations of peat cores from the Hudson Bay Lowlands is used to determine the local presence of conifers in lieu of macrofossil analyses. The differentiation of eight conifer stomate types (Picea type, Larix laricina, Pinus sp., Abies sp., Tsuga mertensiana, Tsuga heterophylla, Chamaecyparis nootkatensis, and Thuja type) is accomplished with a key, diagrammatic stomate illustrations, photographs, and measurements. Results of fossil conifer-stomate analyses indicate that both Picea and Larix arrived locally in the Albany River area of the Hudson Bay Lowlands about 4800 BP. In the Old Man Bog area, Larix arrived earlier, about 6000 BP, but Picea arrived more than 2000 years later (3700 BP). Fossil stomate and pollen results are compared. Key words: conifer stomata, local conifer presence, Hudson Bay Lowlands.

Scottish vegetation history: The Highlands

Article

Jan 1997

Pollen analytical, plant macrofossil and dendrochronological evidence together are used to reconstruct the late-glacial and Holocene vegetation history of the Highlands of Scotland. During the late-glacial period trees were almost, if not entirely, absent from the Highlands; vegetation analogous to that of Arctic regions of Europe today was present throughout the region. During the Holocene, in contrast, forest cover was extensive, with tree lines higher up the mountains and pine forests present even in the far northern Highlands during one millennium or so of especially favourable conditions with warmer, and sometimes drier, summers than today. During recent millennia the climate has been more similar to that of the present and the Highland vegetation was a mosaic of communities similar to that which we can find today in parts of western Scandinavia. During recent centuries extensive logging and deforestation, along with intensified grazing and management, have resulted in the present predominantly treeless landscapes. Appropriate conservation management, informed by palaeoecological record, may enable some areas to once again achieve their ecological potential, but only if allowed by other external human pressures.

Holocene Isochrone Maps and Patterns of Tree-Spreading in the British Isles

Article

Nov 1989

Harry John B Birks

Isochrone maps for Betula L., Corylus avellana L., Ulmus L., Pinus sylvestris L., Alnus glutinosa (L.) Gaertn., Tilia L., Fraxinus excelsior L. and Fagus sylvatica L. in the Holocene of the British Isles, constructed from 135 radiocarbon-dated pollen diagrams, provide a basis for studying the patterns of tree spread. They highlight the strongly individualistic behaviour of each taxon in its arrival areas, directions, timings, rates of spread, and attainment of broad-scale range limits. The biological processes that enable forest trees to spread at rates of 500 m yr-1 or more have implications for palaeoecological and palaeoclimatic reconstructions. -from Author

A square-rod piston sampler for lake sediments

Article

Sep 1967

H. E. Jr. Wright

Extended 14C database and revised CALIB radiocarbon calibration program

Article

Nov 1992
RADIOCARBON

Radiocarbon dates and forest history of the British Isles

Article

Jul 1973
NEW PHYTOL

Radiocarbon dates for a number of pollen analytic features marking important vegetational changes in the Post-glacial of the British Isles are plotted in two figures (Figs. 2 and 3, summarized in Fig. 4). Despite the limitations of the radiocarbon method it becomes clear, where sufficient dates are available, that most of the vegetational developments of the earlier part of the Post-glacial are diachronous. Some of these changes have been used as pollen zone boundaries. The elm decline appears synchronous, however, within the limits of the methods, and the final pine decline in Ireland, which is shown to be older than supposed by Jessen (1949), appears to be one of the least diachronous of the horizons examined. Marked differences in the dates of similar vegetational changes within a small area, and between upland and lowland, are pointed out.

Postglacial migration history of lodgepole pine near Yakutat, Alaska

Article

Feb 2011
CAN J BOT

Dorothy M. Peteet

Pollen stratigraphy from three peat sections near Yakutat, Alaska, suggests that lodgepole pine only recently arrived in southeastern Alaska. In contrast with this palynological interpretation, however, are lodgepole pine (Pinus contorta) macrofossils that are present throughout one entire peat core. 14C dating by accelerator mass spectrometry confirms the establishment of lodgepole pine in this region of Alaska about 10 000 BP. The surprising disparity between the pollen and macrofossil results has important implications for paleomigration research. These results imply that the use of assigned pollen percentages to indicate the presence of a species within a region may not be valid, particularly where a species is at the edge of its geographic range. Comparison of the timing of the first appearance of lodgepole pine pollen from a dozen sections along the north Pacific coast suggests either a late Wisconsin refugium for this pine in southeastern Alaska or extremely rapid late-glacial coastal migration northwestward following ice retreat. Key words: Alaska, pollen, macrofossils, lodgepole pine, phytogeography.

Pollen evidence for the postglacial origins of Nova Scotia's forests

Article

Jan 2011
CAN J BOT

David G. Green

Pollen diagrams from sites in southwest Nova Scotia and close to the New Brunswick – Nova Scotia border show that after retreat of the Wisconsin ice sheets, most tree taxa arrived in the extreme southwest of Nova Scotia earlier than anywhere else in the province. For most tree taxa, arrival times at sites in maritime Canada and in northeastern New England are consistent with very early dispersal of individuals along the coastal strip via the exposed coastal shelf and with their entering Nova Scotia from the southwest. These scattered pioneer populations acted as centres for major population expansions, which followed much later in some cases. Local environments, fire, and interspecies competition appear to have been more important than propagule dispersal rates as factors limiting the spread of most taxa.

Some applications in radiocarbon measurement at the Scottish Research Reactor Centre

Conference Paper

Jan 1972

Modern Pollen and Conifer Stomates from North-Central Siberian Lake Sediments: Their Use in Interpreting Late Quaternary Fossil Pollen Assemblages

Article

Feb 2001

To determine the modern relationship between pollen and stomate deposition and vegetation, surface sediments from 26 lakes along the Lena River in northeastern Siberia were analyzed for pollen and conifer stomate content. The lakes sampled, crossed a vegetation gradient from tundra, forest-tundra, to closed boreal forest. The pollen spectra of tundra lakes are dominated by Betula and Alnus. Cyperaceae and Poaceae are also abundant. Forest-tundra lakes are dominated by Betula and Alnus, but contain lower percentages of Artemisia than tundra lakes. Forest pollen spectra are also dominated by Betula and Alnus pollen, however, forest lakes contain greater percentages of Larix pollen. Principal components analysis indicates that forest and tundra sites were distinct from one another, but considerable overlap exists between forest-tundra and forest and tundra pollen assemblages. Larix stomates were abundant in all samples from regions where trees are currently present except for one lake. Small numbers of Larix stomates were found in tundra lakes, likely due to the redeposition of older material from eroding peat banks. It is likely that this process also contributed some older pollen to modern lake sediments as well. Principal components analysis was used to compare fossil samples from a lake-sediment core to the modern spectra. Early Holocene vegetation assemblages, dominated by herb and Betula shrub tundra and subsequent Larix forests, do not have modern pollen analogs in the lower Lena River region. Modem pollen analogs developed after 6 ka BP, when forest vegetation developed around the site. This was gradually replaced by modern tundra after 3.5 ka BP.

An Atlas of past and present pollen maps for Europe: 0?13,000 years ago By B. Huntley and H. J. B. Birks

Book

Jan 1983

IntCal98 radiocarbon age calibration

Article

Jan 1998
RADIOCARBON

The focus of this paper is the conversion of radiocarbon ages to calibrated (cal) ages for the interval 24,000–0 cal BP (Before Present, 0 cal BP = AD 1950), based upon a sample set of dendrochronologically dated tree rings, uranium-thorium dated corals, and varve-counted marine sediment. The 14 C age–cal age information, produced by many laboratories, is converted to Δ 14 C profiles and calibration curves, for the atmosphere as well as the oceans. We discuss offsets in measured l4 C ages and the errors therein, regional 14 C age differences, tree–coral 14 C age comparisons and the time dependence of marine reservoir ages, and evaluate decadal vs . single-year 14 C results. Changes in oceanic deepwater circulation, especially for the 16,000–11,000 cal BP interval, are reflected in the Δ 14 C values of INTCAL98.

The History of the British Flora. A Factual Basis for Phytogeography

Article

Nov 1956

H. Godwin

Prefaces Part I: Introduction Part II. Collection and Identification of Plant Remains: 1. General considerations 2. Seeds, fruits and leaves, etc. 3. Wood and charcoal 4. Pollen as an index of presence Part III. The Background Scale of Pleistocene Events: 1. Glacial and interglacial periods 2. Radiocarbon dating 3. The Weichselian 4. Flandrian geological events 5. Climatic changes 6. Mire stratigraphy 7. Biological evidence 8. Archaeology 9. Pollen analysis 10. Primary divisions of the last fifteen thousand years Part IV. Recorded Sites: 1. General comments 2. Scottish sites 3. Irish sites 4. Site record Part V. The Plant Record: 1. Introduction: explanation of conventions 2. Collected records Part VI. Pattern of Change in the British Flora: 1. Floristic chances in the Tertiary period 2. The Ice Age and the interglacial periods: climate, soil and vegetation 3. The early Pleistocene 4. The Cromer Forest bed series 5. The Corton interstadial and the Hocnian stage: middle Pleistocene 6. The Ipswichian interglacial 7. Galcial stages: early and middle Weichselian 8. Glacial stages: late Weichselian 9. Phytogeographic synopsis 10. Floristic history in the light of Weichselian records 11. The beginning of the Flandrian period: the pre-Boreal period 12. The early warm period: the Boreal period 13. The thermal maximum and the Atlantic period 14. Prehistoric husbandry and the sub-Boreal period 15. The sub-Atlantic period and climatic deterioration 16. Regional differentiation, migration and survival Part VII: Conclusion Bibliography Index.

Postglacial history of alder (Alnus glutinosa (L.) Gaertn.) in the British Isles

Article

Jan 1990
J QUATERNARY SCI

Data from 92 postglacial pollen sequences are used to map the spread and increase of alder (Alnus glutinosa) across the British Isles between 9000 and 5000 years ago. The spread is found to be patchy and erratic in space and time. Consideration of the habitat requirements and reproductive ecology of alder suggest that it spread within Britain and Ireland after about 10 000 yr BP, when suitable habitat for it was scarce. Alder spread across most of Britain and Ireland early in the postglacial but only increased in abundance as (i) suitable habitat became available through changing sea levels, hydroseral successions, and floodplain development, and as (ii) rare weather events produced the necessary conditions for reproduction. Alder is unique among British and Irish trees in its requirement for a suitable habitat isolated among expanses of unsuitable habitats. Because of this, maps of its postglacial population spread and increase do not show the spatial coherence of maps for other forest tree taxa.

A key for the identification of stomata of the native conifers of Scandinavia

Article

Feb 2004
REV PALAEOBOT PALYNO

Charlotte A Sweeney

In Scandinavia there are four extant native conifers (Pinus sylvestris, Picea abies, Juniperus communis and Taxus baccata). Larix sibirica has been found as a Holocene fossil in the mountains of central Scandinavia, and as an earlier interglacial fossil. Abies alba may have occurred earlier in the Quaternary. A key for identifying the stomata of these conifers has been prepared for both complete and incomplete stomata. This has been achieved through measurements of reference stomata from fresh needles prepared in the same way as fossil pollen and a canonical variate analysis on the resulting data.

The Selection of Sites for Paleovegetational Studies

Article

Jul 1981

The judicious selection of sites for paleovegetational and paleoclimatic studies permits paleoecologists to answer specific research questions that go beyond primary descriptions of past vegetation. We present a model that describes the relationship between basin size and pollen source area and predicts the proportions of local, extralocal, and regional pollen sampled by lake basins of different size. The distinctive sampling properties of lakes, peats, and small hollows can be exploited to provide details of pattern in paleovegetation so long as attention is given to the limitations and problems of these types of sites. Combinations of site types in a single study most fully exploit the information contained in sediments.

The Pest-Glacial history of Finns sylvestris in the British Isles

Article

Dec 1984
QUATERNARY SCI REV

Keith David Bennett

A consideration of all available macrofossil and pollen data suggests that Pinus sylvestris entered England from the southeast just after 10,000 BP, and spread across nearly the whole of the British Isles, reaching northernmost Scotland by 4000 BP. Populations in western Ireland and northern Scotland may have had an independent glacial refugium (or refugia). Competition from deciduous trees such as Corylus avellana, Ulmus and Quercus, restricted the habitats available to P. sylvestris at about 9000 BP. At about 7500 BP, expanding populations of Alnus glutinosa replaced some of the remaining P. sylvestris populations. By about 4000 BP, P. sylvestris occurred only in northern and mountainous areas, on raised bogs, and on the limestone of the Burren, western Ireland. P. sylvestris over much of its range was severely reduced by the spread of blanket bog at about 4000 BP. This event may have been initiated by widespread climatic change.

Pollen Accumulation Rates: Estimates from Late-Glacial Sediment of Rogers Lake

Article

Oct 1964

Absolute pollen deposition in a Connecticut lake over a 4000-year interval has been estimated from pollen frequencies in a core of late-glacial sediment dated by radiocarbon techniques. The rate of total sediment accumulation as measured after burial was statistically constant at 0.036 centimeter per year, but the rate of deposition of pollen grains onto the sediment increased from 600 to 900 grains 14,000 years ago to 9000 per square centimeter per year 10,000 years ago. A major increase in the deposition of tree pollen occurred about 11,500 years ago, at the beginning of the spruce pollen zone. Presentation of data in conventional (percentage) form masks the magnitude of this change and distorts many of the changes in accumulation rates for individual types of pollen; moreover it magnifies statistical variation in the herb zone where all pollen is scarce.

Kluwer Academic, Dordrecht, The Netherlands. Benninghoff, W. S. 1962. Calculation of pollen and spore density in sediments by addition of exotic pollen in known quantities

332-333

Terrestrial

Terrestrial, algal, and siliceous indicators. Kluwer Academic, Dordrecht, The Netherlands. Benninghoff, W. S. 1962. Calculation of pollen and spore density in sediments by addition of exotic pollen in known quantities. Pollen et Spores 4:332–333.

Quaternary history and the stability of forest communities. Pages 132–153 in

Jan 1981

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Fossil stomata reveal early pine presence in Scotland: Implications for postglacial colonization analyses

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