Elm Decline Research Articles

Applying palaeoecological analogues to contemporary challenges: community-level effects of canopy gaps caused by systematic decline of a prevalent tree species

Temperate woodland vegetation is initially determined by spatiotemporal and historical factors, mediated by complex biotic interactions. However, catastrophic events such as disease outbreaks (e.g., sweet chestnut blight, ash dieback), infestations of insect pests, and human-accelerated climate change can create canopy gaps due to systematic decline in, or loss of, tree species that was once an important part of the canopy. Resultant cascade effects have the potential to alter the composition of woodland ecosystems quickly and radically, but inherent lag times make primary research into these effects challenging. Here, we explore change in woodland vegetation at 10 sites in response to canopy opening using the Elm Decline, a rapid loss of Ulmus in woodlands across northwestern Europe ~ 5800 years ago that coexisted alongside other stressors such as increasing human activity, as a palaeoecological analogue. For arboreal taxa, community evenness significantly decreased, within-site turnover significantly increased, and richness remained unchanged. Changes in arboreal taxa were highly site-specific but there was a substantial decline in woody climbing taxa, especially Hedera (ivy), across the majority of sites. For shrub taxa, richness significantly increased but evenness and turnover remained consistent. Interestingly, however, there was a significant increase in abundance of shrubs at 70% of sites, including Calluna (heather), Ilex (holly) and Corylus (hazel), suggesting structural change. Surprisingly, there was no change in richness, evenness or turnover for herb taxa, possibly because change was highly variable spatially. However, there was a marked uptick in the disturbance indicator Plantago (plantain). Overall, these findings suggest that woodlands with sustained reduction in, or loss of, a tree species that once formed an important part of the canopy has profound, but often spatially idiosyncratic, impacts on vegetation diversity (richness), composition (evenness), stability (turnover), and on abundance of specific taxa, especially within the shrub layer. Use of this palaeoecological analogue, which was itself complicated by cooccurring changes in human activity, provides a valuable empirical insight into possible cascade effects of similar change in canopy opening in contemporary settings, including Ash Dieback.

The age structure of Ulmus L. stands in the eastern regions of Ukraine

The aim of the research was to determine the features of the age structure for natural and artificial elm stands depending on species, origin, and region. The proportion of the stand area of natural and artificial stands of each elm species by 10-year age classes was evaluated for the forest fund of the Donetsk, Kharkiv, and Sumy Regional Forest and Hunting Management Administrations (RFHMA). Four main forest-forming elm species are represented in the forest fund of the Donetsk and Kharkiv RFHMA (U. minor, U. laevis, U. glabra, and U. pumila). In the Sumy RFHMA, there are three forest-forming elm species: U. minor, U. laevis, and U. glabra. The maximum age of U. minor is 120, 117, and 91 years in the Donetsk, Kharkiv, and Sumy RFHMA, respectively. The mean and the maximum age of U. minor and U. glabra tends to decrease in the Donetsk – Kharkiv – Sumy RFHMA row. The proportion of U. laevis is larger in man-made plantations than in natural stands, however, in natural stands, it also increases in the Donetsk – Kharkiv – Sumy RFHMA row. U. glabra prevails in natural stands. U. pumila in the Donetsk RFHMA grows mainly in man-made plantations. A decrease in the area of newly formed U. minor stands in the Donetsk RFHMA occurred after the 1950s, and in the Kharkiv RFHMA after the 1960s in both artificial and natural stands. In the Sumy RFHMA, this also happened in the 1960s in man-made plantations. A decrease in the area of U. glabra natural and artificial stands occurred also after the 1960s. We suppose that an epiphytoty of the Dutch elm disease, well-known in Europe in the 1960s, could also be the cause of elm decline in the eastern part of Ukraine. The proportion of the stands’ area preserved up to a certain age, depends on particular elm species, region, and stand origin. However, in order to clarify the survival rate, it is necessary to consider the type of forest site conditions, the proportion of elms in the stand composition, and some other features that are to be analyzed in future research.

A multi-proxy Holocene palaeoenvironmental record of climate change and prehistoric human activity from Lough Cullin, southeast Ireland

A multiproxy (pollen, microcharcoal, loss-on-ignition, magnetic susceptibility and geochemistry) sequence from Lough Cullin, southeast Ireland, supported by a high-resolution radiocarbon chronology, modelled using Bayesian approaches, provides a record of environmental change for much of the Holocene. Following the establishment of mixed deciduous woodland, climatic deterioration was likely responsible for pronounced vegetation change and erosion, 7615–6500 cal. BC to 6245–5575 cal. BC, evidence for the ‘8.2 Kyr’ BP climate event. The so-called ‘elm decline’ is dated to 4220–3980 cal. BC and whilst there are possible indications of an anthropogenic cause, clear evidence of woodland clearance with cereal pollen is recorded at 3900–3700 cal. BC, 3790–3580 cal. BC and 3760–3650 cal. BC, during a period of clearance and farming of 320–450 years duration. A reduction in farming/settlement and woodland regeneration during the Middle Neolithic parallels the archaeological record, with low levels of activity during the Late Neolithic/Chalcolithic after 2960–2525 cal. BC, prior to increases during the Bronze Age then woodland clearance and agriculture between 1500–1410 and 1275–1000 cal. BC, corresponding with the archaeological evidence. A subsequent ‘step-wise’ reduction in human activity follows, from the latter date to 815–685 cal. BC, and a brief but pronounced cessation at 690–535 cal. BC. Renewed woodland clearance and agriculture commenced until 415–250 cal. BC. From the latter date until cal. AD 390–540, the Late Iron Age/Early Medieval period, a phase of woodland recovery is attested, followed by renewed landscape disturbance and arable agriculture in particular, continuing to the close of the record at cal. AD 780–1035.

Modelling Prehistoric Topography and Vegetation in the Lower Thames Valley, UK: Palaeoenvironmental Context for Wetland Archaeology and Evidence for Neolithic Landnám from North Woolwich

ABSTRACT Multi-proxy investigations at 2 Pier Road, North Woolwich, London, UK, have revealed deposits spanning the Middle-Late Holocene from the late Mesolithic (c. 4360 cal BC) onwards. Pollen data show an Elm Decline at c. 4210–3950 cal BC followed by landnám clearances at c. 4210–3910 cal BC and c. 3710–3030 cal BC and the first appearance of cereal at c. 3540–3030 cal BC. These events are potentially contemporary with the construction of nearby Neolithic trackways, providing indirect evidence for agriculture and settlement. REVEALS modelling shows the first significant reduction in woodland cover is coincident with the Neolithic Elm decline, but the main step-change to open conditions occurred in the Early Bronze Age, following a decline in lime at c. 2110–1630 cal BC. Palaeo-topographic modelling of the region shows that although the trend towards increasing openness coincides with gradual wetland expansion, the shift to open vegetation cover cannot be explained by this and is probably the result of human activity. This study highlights the value of combining deposit and vegetation cover modelling to contextualise wetland archaeology and shows that together these provide useful proxies for landscape-scale human activity that can identify ephemeral signals of prehistoric activity.

Post-glacial vegetation and landscape change in upland Ireland with particular reference to Mám Éan, Connemara

Holocene vegetation dynamics of mid-western Ireland are discussed with particular reference to the Galway and Mayo uplands, the development of upland blanket bog and the history of pine and yew. A detailed pollen profile from Mám Éan (Maumeen), a corrie lake, provides insights into environmental change in upland Connemara where, in recent decades, overgrazing and peat erosion have given rise to serious environmental concerns. Vegetation dynamics are broadly comparable to those in lowland Connemara and also upland sites in the Nephin Begs, Co. Mayo. The available evidence suggests corrie glaciation in the Younger Dryas. The oldest sediments show the usual early Holocene progression from open herbaceous communities to woody vegetation dominated by juniper, tree birch, and finally hazel. Tall canopy trees then spread, including pine, and elm and oak, and later alder (at ca. 7.7 ka). In the interval 10.2–4.8 ka, pine was dominant and for much of this time fires were frequent. There is a distinct mid-Holocene Elm Decline and a short Neolithic Landnam phase that is followed by woodland regeneration involving, at first, mainly pine and later yew. 14C dating of bog-pine from upland sites sheds new light on pine and upland blanket bog development in the mid-Holocene. It is shown that while blanket bog was initiated at Mám Éan by ca. 10.8 ka, the present-day treeless landscape has come about within the last 1000 years as a result of sustained human impact, that has also resulted in severe erosion of minerogenic and, more recently, peaty soils.

Multi-profile fine-resolution palynology of Late Mesolithic to Bronze Age peat at Cat Stones, Rishworth Moor, Central Pennines, UK

Palynological data from three radiocarbon dated peat profiles at Rishworth Moor in the Pennine hills of northern England provide a record of vegetation change and human impacts in the Late Mesolithic, Neolithic and Bronze Age periods. All three cultures have archaeological sites present in the vicinity, with Late Mesolithic sites by far the most abundant, comprising mainly very late assemblages dominated by ‘rod’-shaped microliths. Pollen evidence of vegetation disturbance occurs during all three archaeological periods, and is attributed to the results of human activity. Microscopic charcoal and non-pollen palynomorph analyses support the pollen evidence. Sites at Cat Stones 2 and Cat Stones 3 record evidence of Neolithic and Bronze Age date only. Cat Stones 1 extends into the Late Mesolithic period, and fine-resolution pollen analyses have been applied in this profile to the Mesolithic–Neolithic transition leading up to the mid-Holocene Elm ( Ulmus) Decline, which starts here at c. 494014C BP (5670 cal. BP), a typical date for it in the central Pennines. Bayesian age-depth modelling provides precise ages for the vegetation changes and their spatial correlation. The plateau was dominated by scrub and grassy Calluna heath from the Late Mesolithic onwards. Elevated microscopic charcoal levels and ruderal herb pollen record phases of fire disturbance below the Elm Decline, including a grain of Hordeum cereal-type. Whether this grain represents early cultivation requires further research. Bronze Age impacts are of greater intensity, but disturbances of all three cultural periods are low scale, agreeing with the results of previous research in the Pennines.

Neolithic land-use dynamics in northwest Ireland: multi-proxy evidence from Lough Arrow, County Sligo

A high-resolution multi-proxy study of lake sediments from Loughbrick Bay in Lough Arrow, County Sligo, Ireland provides a detailed record of Neolithic vegetation history and land-use change. The high concentration of megalithic monuments around Lough Arrow suggests that the region was a centre of settlement and ritual activity during the Irish Neolithic. The pollen record indicates that human activities, including farming, intensified ca. 100 years after the mid-Holocene elm decline, which is dated to 3820 bc. Pastoral and arable farming formed part of the Neolithic subsistence economy, in particular during the first half of the Neolithic. Although levels of human impact were low during most of the later Neolithic, allowing woodland recovery, short periods of arable farming recurred during that time. Human pressure on the landscape increased again at the end of the Neolithic and during the Chalcolithic period. Interruption of farming and settlement activities often coincided with wetter climate. Comparison of this study with records from nearby lakes shows that the type of farming varied at a local scale. While pastoral farming was widespread, cereal cultivation was spatially and temporally restricted. The pollen evidence suggests that wheat was the predominant crop during the earlier Neolithic, whereas barley became more important during the later Neolithic.

The Elm Decline is Dead! Long Live Declines in Elm: Revisiting the Chronology of the Elm Decline in Ireland and its Association with the Mesolithic/Neolithic Transition

ABSTRACT The Elm Decline (ED), is a marked reduction in Ulmus recognised in pollen diagrams from across north/northwest Europe c. 5-6000 cal BP, the causes of which have been much discussed for over half a century, partly because of its broad chronological correspondence with the Mesolithic-Neolithic transition. We present a formal statistical analysis of the ED chronology in Ireland, analysing its association with early Neolithic anthropogenic activity as indicated indirectly by palynological evidence and directly through radiocarbon dated cereal macrofossils. The results derived from pollen records regarded as sufficiently robust for Bayesian modelling indicate the date for the ED ranges from the later Mesolithic to middle Neolithic. Different palynological ‘expressions’ of the ED are identified, and comparison of the ED date range and increases in Plantago lanceolata indicate that although correlation between anthropogenic activity and the onset of the ‘Elm Decline’ can be identified at several sites, this is not consistent. Comparison with the cereal macrofossil record demonstrates that generally the ED occurred prior to the onset of Neolithic cereal cultivation as defined by these data. We discuss implications for understanding the patterns and processes that may underlie the ED and question whether the ‘Elm Decline’ continues to merit the definite article.

Vegetation impacts and early Neolithic monumentality: A palaeoenvironmental case study from south-west Ireland

New insights into prehistoric vegetation and human activities around a megalithic monument were inferred from a palaeoecological study at Arderrawinny, south-west Ireland. An early Neolithic portal tomb located c.500 m north-east of a small mire was investigated for pollen and loss on ignition analyses. This investigation provides a detailed reconstruction of the local vegetation development for the area surrounding the megalithic tomb, supported by 12 AMS 14C measurements and Bayesian modelling of palaeoecological and archaeological data. The palaeoecological record indicates a degree of ‘openness’ which was unusual in pre-Neolithic contexts in Ireland. Bayesian modelling of palaeoecological and archaeological chronologies intimates that evidence for woodland clearings preceded the construction of the megalith and suggests spatial separation between settlement, cultivation and ‘ritual’ activity in the early Neolithic. Despite low evidence for Neolithic agricultural, a potential correlation between human activity, as indicated by the presence of the nearby early Neolithic portal tomb, and the onset of the mid-Holocene ‘Elm Decline’ in the region is suggested.

Comparison of a recent elm decline with the mid-Holocene Elm Decline

The threat of devastating pathogens on a range of tree species has increased recently, which justifies the investigation of the temporal dynamics of tree declines caused by disease. The mid-Holocene Elm Decline was a widespread and synchronous event recorded in pollen diagrams across northwest Europe. The probable drivers of this event have been debated for over 80 years but the role of disease has gathered greatest support in recent decades. Here we report pollen data at sub-decadal resolution from a closely sampled sediment core from eastern Ireland covering the last 160 years. This provides data on the structure and dynamics of the surrounding woodland before, during and after the outbreak of Dutch elm disease in the 1970s. A decline in elm was also recorded in the 1940s associated with an earlier, less virulent, outbreak of elm disease. The elm population recovered from the 1940s outbreak after 20 years but did not recover from the 1970s pandemic. The pollen data also facilitate the comparison of this disease-mediated decline with the mid-Holocene Elm Decline; the impact of human disturbance and disease resulted in different woodland compositions and the adjustment of the woodland in response to these factors was rapid. The impact of Dutch elm disease on this elm 1970s population was very similar to that recorded in the mid-Holocene Elm Decline in Britain and Ireland.

First Report of ‘Candidatus Phytoplasma trifolii’-Related Strain of 16SrVI-A Phytoplasma Subgroup, Associated with Elm Yellows Disease in American Elm (Ulmus americana L.) in Ohio, U.S.A

During the investigation of the sudden and early onset of yellowing, followed by mortality of American elm (Ulmus americana L.) trees at the USDA Forest Service Northern Research Station in Delaware, Ohio, a phytoplasma of the clover proliferation group (16SrVI) was detected as the putative causal agent of the disease outbreak. Onset of symptoms was rapid and widespread, occurring in late July 2016 and affecting ∼60 trees across two elm research plantations. Symptoms included a general yellowing of individual tree canopies, epinasty of foliage throughout the canopy, phloem discoloration, and on a subset of trees, a strong odor of methyl salicylate (observed in phloem tissue extracted from the lower stem). Similar symptoms in elms have been attributed to the classic elm yellows ‘Candidatus Phytoplasma ulmi’ (16SrV-A) (Lee et al. 2004) and the Illinois elm yellows phytoplasma (16SrVI-C) (Jacobs et al. 2003). In July 2016, samples were collected from 12 symptomatic and 8 asymptomatic American elm trees. DNA from the leaf midrib and branch phloem was isolated and analyzed for phytoplasma via seminested polymerase chain reactions (PCR). PCRs were first primed by phytoplasma universal primer pair P5/P7 (Jomantiene et al. 1998), followed by P7 and the reverse complement of the universal phytoplasma primer R16R2 for amplification of the phytoplasma 16S-23 ribosomal (r) DNA (16S-23 rRNA gene) sequences as per Gundersen and Lee (1996). The predicted band size of the second PCR product is 487 base pair (bp). The product bands were isolated, purified, and sequenced using primer P7. Sequencing results of the PCR products indicated that nine of the symptomatic and one of the asymptomatic American elm trees tested were infected by a phytoplasma. A BLAST search of the DNA sequences indicated high similarities to members of the ‘Ca. P. trifolii’ group 16SrVI-A. The sequences of all 10 phytoplasma-infected trees were identical to each other. To further confirm that a strain of ‘Ca. P. trifolii’ was infecting the elms, a PCR product was cloned and sequenced. The 1,557 bp band was the product of primers P1a/P7, followed by PCR primers designed from the sequence of ‘Ca. P. trifolii’. This band was cloned into the pMiniT 2.0 vector. Plasmid sequencing used standard sequencing primers (SP6 and T7 promoters), the primers included with the vector, and finally, custom designed phytoplasma primers that eliminate other bacterial DNA from getting amplified. The entire plasmid clone was sequenced in both directions with four to six times of coverage per base. Determination of the phytoplasma classification group was based on the nucleotide sequence within the phytoplasma universal primers F2n/R2 PCR fragment within the 16Sr gene. Using iPhyClassifier, the online tool for phytoplasma classification and taxonomic assignment (https://plantpathology.ba.ars.usda.gov/cgi-bin/resource/iphyclassifier.cgi), the sequence similarity between the Delaware elm phytoplasma and ‘Ca. P. trifolii’ (GenBank accession no. AB279597.1) is 99.9% in the 16Sr region, which places the Delaware elm phytoplasma in the 16SrVI-A group. The sequence of the plasmid was deposited in GenBank under accession number MF385584. Elm decline and yellows diseases in North America have been associated with the Illinois elm yellows phytoplasma (16SrVI-C, GenBank accession no. AF268893.1) (Jacobs et al. 2003), ‘Ca. Phytoplasma ulmi’ (16SrV-A) (Lee et al. 2004), and phytoplasma in the aster yellows group (16SrI-C) (Lee et al. 1995).

The Mesolithic-Neolithic Transition and the Chronology of the “elm decline”: A Case Study from Yorkshire and Humberside, United Kingdom

ABSTRACTThe Neolithic in Britain saw the first appearance of domestic plant and animal resources, pottery, polished stone axes, monuments, and new house structures. With the introduction of domesticates and associated subsistence strategies, the Neolithic represents a significant change in human–environment interaction. Other changes have been observed in the palynological record of Britain in the early fourth millennium cal BC, including the elm decline, and archaeologists and paleobotanists have long discussed the degree of human involvement in this. This paper presents the first Bayesian statistical analysis of the elm decline using the case study of the east of Yorkshire and Humberside and key sites in west Yorkshire, and evidence for the last hunter-gatherer Mesolithic material culture and the first Neolithic material culture record. This region is critical because it is the only area of Britain and Ireland where we have robust and accurate published estimates for the timing of the latest Mesolithic activity and timing for the earliest Neolithic activity. Unpacking this perceived chronological correlation between the elm decline and the start of the Neolithic is critical to understanding the scale of human–environment modification at this time, and the nature of the first Neolithic societies in Britain.

Human activity was a major driver of the mid‐Holocene vegetation change in southern Cumbria: implications for the elm decline in the British Isles

ABSTRACTThe dramatic decline in elm (Ulmus) across a large swathe of north‐west Europe in the mid‐Holocene has been ascribed to a number of possible factors, including climate change, human activity and/or pathogens. A major limitation for identifying the underlying cause(s) has been the limited number of high‐resolution records with robust geochronological frameworks. Here, we report a multiproxy study of an upland (Blea Tarn) and lowland (Urswick Tarn) landscape in southern Cumbria (British Isles) to reconstruct vegetation change across the elm decline in an area with a rich and well‐dated archaeological record to disentangle different possible controls. Here we find a two‐stage decline in Ulmus taking place between 6350–6150 and 6050–5850 cal a BP, with the second phase coinciding with an intensification of human activity. The scale of the decline and associated human impact is more abrupt in the upland landscape. We consider it likely that a combination of human impact and disease drove the Ulmus decline within southern Cumbria.

Multi-profile fine-resolution palynological and micro-charcoal analyses at Esklets, North York Moors, UK, with special reference to the Mesolithic-Neolithic transition

Multi-proxy palaeoecological data from two peat profiles at Esklets on the North York Moors upland provide a record of vegetation changes for much of the Holocene. Possible vegetation disturbance in the late Mesolithic and activity in the Neolithic and Bronze Age are recognised. In both profiles fine resolution analyses have been applied to the period leading up to the mid-Holocene Elm Decline which in this upland has been dated to ca. 4,800 bp (uncalibrated 14C years). Disturbance impacts at the Esklets Elm Decline are low scale, but phases of woodland disturbance, which include cereal (Hordeum)-type pollen, occur in both profiles ca. 5,200 bp, some centuries before the Elm Decline on the North York Moors, but similar to dates for this key palynological horizon in nearby lowland areas. A protocol is presented for the separation of Hordeum (cultivated species) and Glyceria (wild grass) pollen. The Esklets sites record disturbances during the late Mesolithic-Neolithic transition. These pre-Elm Decline disturbance phases represent either early penetration of neolithic cultivator-pastoralists into this upland or the activities of final mesolithic foragers. No neolithic archaeological sites occur nearby, but a ‘Terminal Mesolithic’ flint site dominated by microlith ‘rod’ forms occurs close to the palaeoecological sites. Such rod sites are dated in northern England to the centuries leading up to 5,000 bp and so are contemporary with the disturbance phases that included Hordeum-type pollen at Esklets. The cultural context of these disturbance phases and the role of ‘rod’ microlith sites during the Mesolithic-Neolithic transition require further focused research to clarify all issues relating to this important period.

The timing and causes of the Neolithic elm decline: New evidence from the Lower Thames Valley (London, UK)

Two new multi-proxy records of environmental change are provided from Horton Kirby Paper Mill and Old Seager Distillery in the Lower Thames Valley. Each site has evidence for a decline in elm woodland, which at Horton Kirby Paper Mill is recorded earlier than any other published record from the British Isles: sometime between 7320 and 7240 cal BP. Scolytus scolytus/S. multistriatus (the vectors for Dutch elm disease) are recorded after the decline in both sequences, adding to the number of sites with such evidence in the British Isles. Evidence of paludification and human activity are also recorded at the time of the elm decline reinforcing the multi-causal hypothesis. Integration of these results with 21 palaeoenvironmental records has produced a large number of well-dated, multiproxy records of the elm decline in this part of the UK. On the basis of this dataset, a classification system for categorising the relationships between the causal factors of the elm decline is proposed and recommended for future studies.

Neolithic agriculture on the European western frontier: the boom and bust of early farming in Ireland

A multi-disciplinary study assessing the evidence for agriculture in Neolithic Ireland is presented, examining the timing, extent and nature of settlement and farming. Bayesian analyses of palaeoenvironmental and archaeological 14C data have allowed us to re-examine evidential strands within a strong chronological framework. While the nature and timing of the very beginning of the Neolithic in Ireland is still debated, our results – based on new Bayesian chronologies of plant macro-remains – are consistent with a rapid and abrupt transition to agriculture from c. 3750 cal BC, though there are hints of earlier Neolithic presence at a number of sites. We have emphatically confirmed the start of extensive Neolithic settlement in Ireland with the existence of a distinct ‘house horizon’, dating to 3720–3620 cal BC, lasting for up to a century. Cereals were being consumed at many sites during this period, with emmer wheat dominant, but also barley (naked and hulled), as well as occasional evidence for einkorn wheat, naked wheat and flax. The earliest farmers in Ireland, like farmers elsewhere across NW Europe, were not engaged in shifting cultivation, but practised longer-term fixed-plot agriculture. The association between early agriculture and the Elm Decline seen in many pollen diagrams shows that this latter event was not synchronous across all sites investigated, starting earlier in the north compared with the west, but that there is a strong coincidence with early agriculture at many sites. After this early boom, there are changes in the nature of settlement records; aside from passage tombs, the evidence for activity between 3400 and 3100 cal BC is limited. From 3400 cal BC, we see a decrease in the frequency of cereal evidence and an increase in some wild resources (e.g. fruits, but not nuts, in the records), alongside evidence for re-afforestation in pollen diagrams (3500–3000 cal BC). Changes occur at a time of worsening climatic conditions, as shown in Irish bog oak and reconstructed bog surface wetness records, although the links between the various records, and assessment of causes and effects, will require further investigation and may prove complex. This period seems to have been one of environmental, landscape, settlement and economic change. The later 4th millennium BC emerges as a period that would benefit from focused research attention, particularly as the observed changes in Ireland seem to have parallels in Britain and further afield.

Evidence for climatic variability and its impact on human development during the Neolithic from Loughmeenaghan, County Sligo, Ireland

AbstractHigh‐resolution pollen and geochemical analyses conducted on a sediment profile from a small lake in County Sligo, Ireland, revealed that human development during the Neolithic was influenced by pronounced climatic oscillations. The primeval woodland around the lake experienced a considerable transformation coinciding with the elm decline at 3810 BC. The subsequent increase in summer temperatures and decrease in precipitation favoured wheat cultivation in the lake's catchment area, which was practised for approximately 140 years. A shift towards pastoral farming took place with the establishment of exceptionally dry conditions between 3650 and 3560 BC, when lake level and influx of allochthonous material were notably low. The onset of cool and wet conditions at the transition from the Early to Middle Neolithic possibly caused the initial decline of human activity in the area. Periods of particularly high precipitation during the Middle and early Late Neolithic contributed to the abandonment of the area by the first farmers. Comparison of the proxy record from the study site with other palynological and archaeological records from Ireland suggests that climatic variability on the decadal to centennial scale represented a primary control on the nature and duration of farming practices during the Neolithic. Copyright © 2012 John Wiley & Sons, Ltd.

Vegetation and settlement history of the past 9000 years as recorded by lake deposits from Großer Eutiner See (Northern Germany)

Pollen analyses of a 24m long sediment core from Großer Eutiner See, a lake located in the lakeland area of the young moraine landscape of Ostholstein, Northern Germany, reveals over 9000years of vegetation and settlement history. The record is time controlled by 12AMS 14C dates of terrestrial plant remains. First human impact is evident already in the late Mesolithic between 5120 and 4900BC (7070–6850cal. yr BP). Simultaneously with the elm decline at about 3940BC (5890cal. yr BP), first agricultural activity is registered in the early Neolithic. The strongest Neolithic opening of the landscape occurred during the Single Grave culture at around 2450BC (4400calyr BP). The early Bronze Age (3770–3060cal. yr BP) is characterized by low settlement activity. During the late Bronze Age large scale expansion of arable farming and pasture land is documented from c. 990 to 490BC (2940–2440cal. yr BP). Between 350BC and AD 170 (2300–1780cal. yr BP), massive increase of heather indicates advanced deterioration of soils by continuous exploitation during the pre-Roman and to a somewhat lesser extent during the late Roman Iron Age. About AD 530 to 670 (1420–1280cal. yr BP) a distinctive settlement gap occurred, followed by three phases of intensive Slavic settlement until AD 1140 (810cal. yr BP). In the further course of the Middle Ages areas under cultivation increased strongly at the expanse of woodland. At this time new crops were introduced like hemp, buckwheat and walnut. The area of Großer Eutiner See largely remains untouched by the late medieval crisis in the 14th century. Forest degeneration continued during the Modern Period. During the 18th and 19th centuries agricultural impact reached its maximum. A gradual recovery of the forest is observed only in the recent decades.

Litorina Sea shore displacement and pollen analytical indications of forest succession during the Mid-Holocene in Gästrikland, east central Sweden

This paper deals with the mid-Holocene shore level history and vegetation development in Gästrikland, east-central Sweden. This is investigated using sediment and microfossil records and 14C datings. The time span covered is c. 8000–5000 cal yr BP. Vegetation history during this time includes an increase in Tilia pollen 6500–6300 cal yr BP and a decrease in Ulmus and Corylus c. 5500 cal yr BP. The former change coincides with a sharp drop in relative sea level (RSL) of some 5 m; this RSL drop can be correlated to the regression from the L3 transgression of the Litorina Sea, identified in other areas around the Baltic Sea. The possible connections between RSL and climate (in particular changes on a maritime-continental continuum), as indicated by new pollen data and other records, are investigated. The new material shows, in comparison to other pollen records from southern and central Scandinavia, unusually high percentages of Tilia, Ulmus and Corylus pollen, but less Quercus. The change in pollen spectra around 5500 cal yr BP can be correlated to the northern European “elm decline”. A regional cooling is recorded in widespread data for this time, but observations suggest that other factors must be considered here, including disease and change in the physical landscape due to the ongoing land uplift.

Environmental changes during early-middle Holocene from the sediment record of the Chaohu Lake, Anhui Province

A typical lake sediment core is obtained from the Chaohu Lake in the lower reaches of the Yangtze River, Anhui Province, China. The timing scale is constrained by AMS 14C dating method. Climate proxies such as pollen and grain size in the core are analyzed to reconstruct the environment changes at this site approximately between 9870 and 2170 cal. a BP. The results indicate that at the research area, the climate in the early-middle Holocene had evolved through 3 stages. From 9870 to 6040 cal. a BP, proxy records show a warm and dry climate with low water levels after the late-glacial period. During this stage, cool and dry events occurred at about 8910 and 6060–6030 cal. a BP. Then, between 6040 and 4860 cal. a BP, the climate was humid and vegtation was more flourishing in the Chaohu Lake Valley. The Holocene Optimum occurred at 5840–5500 cal. a BP in the Chaohu Lake, showing the best condition of water and heat. Elm Decline occurred at the period of 5380–4930 cal. a BP. Since 4860 cal. a BP, the climate was warm and dry through 2170 cal. a BP as shown in both pollen spectrum and grain-size histories. Two obvious dry events occurred in 3760 and 2170 cal. a BP, respectively. At 2170 cal. a BP, the water level of the Chaohu Lake reached the lowest as the lakebed possibly exposed. Such lake sediment observations are consistent with the historical records in this area.