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This paper presents an event stratigraphy based on data documenting lake-level changes as well as volcanic eruptions over the period 4500-3500 cal. BP from sediment sequences of Lakes Accesa in Tuscany (north-central Italy) and Maliq (Albania) in the central Mediterranean. The available data make it possible to recognise a tripartite climatic oscillation between c. 4300-3800 cal. BP. A phase characterised by drier conditions at c. 4100-3950 cal. BP appears to have been bracketed by two phases marked by wetter conditions and dated to c. 4300-4100 and 3950-3850 cal. BP, respectively. The deposition of theAvellino tephra occurred during the first humid phase, slightly before 4300 cal. BP, and that of an interplinian tephra AP2-AP4 (or Pr1) around 4050 cal. BP during the dry intermediate phase. This dry median episode may be related to the so-called '4.2 ka event' observed in tropical areas as well as in northwestern Italy. A comparison of the Accesa lake-level record with palaeoclimatic terrestrial and marine records suggests that this complex climatic oscillation around 4300-3800 cal. BP affected the central and western Mediterranean area. The key position of the 4300-3800 cal. BP climatic oscillation at a crucial transition from mid to late Holocene in the Mediterranean and tropical areas, deserves major consideration in further investigations. [ABSTRACT FROM AUTHOR]

In highly anthropogenic plant communities, environmental conditions and human practices play a significant role in the composition, structure and diversity of the flora. This paper presents a study of current and past floras of two anthropogenic habitats (cultivated and ruderal) in eastern France that have been the subject of numerous palaeo-environmental studies (pollen and seed analysis). To understand the different components that constitute the biodiversity of these floras, it is necessary to develop a transdisciplinary method combining ecology, phytogeography and palaeoenvironmental sciences. As a first step, a distinction has been made between native and alien plants as well as between two categories of the latter: archaeophytes (alien taxa introduced into a study area before Ad 1500) and neophytes (alien taxa which became established after Ad 1500). Second, the study of ecological characteristics of these species and the knowledge of human and climatic history of the region allow the elaboration of a synthesis of biodiversity evolution in these environments from the Neolithic to the present day. The results of this analysis show that there has been a constant enrichment of the anthropogenic flora by alien species through time. Two main periods can be emphasized: the first began in the late Neolithic and reached a peak in the late BronzeAge, the second began with the advent of Modern times. This kind of study has a double implication: first, by distinguishing between native and alien species (archaeophytes and neophytes) and by refining their ecological characteristics, the method allows a critical evaluation of the modern phytosociological units which are traditionally used to interpret fossil assemblages and to discriminate species that are 'strong' indicators of human activities. Second, the recognition of native and alien species also has implications for species invasion studies and for species conservation and vegetation management in anthropogenic habitats. [ABSTRACT FROM AUTHOR]

This paper describes the application of a hydrogeomorphological numerical model (CAESAR) to simulate, at hourly time steps, changes in the hydrological and sediment regime of the Petit lac d'Annecy catchment. The outputs of the model were validated in three ways. In the short term (∼5 years), water discharge outputs were compared against observed instrumental data. Over the longer term, modelled sediment discharge (AD 1825-2005) was compared with proxies for detrital sediment influx (environmental magnetism) and accumulation rates discerned from a 210Pb chronology for the lake sediments. Finally, spatial validation of the modelled erosion and deposition of sediment was undertaken by comparison with a field and remotely sensed survey of catchment geomorphology. The results suggest that while minor perturbations in forest cover during the last 180 years have partially conditioned the response of the sediment system, the bulk of modelled sediment discharge and particularly the peaks in sediment discharge were controlled by flood duration and magnitude, which in turn is driven by precipitation (storms/floods) and snowmelt. Basin geometry and geomorphology of each subcatchment (Ire and Tamie) were also important in producing differences in the modelled sediment discharge. In essence, these differences were a function of sediment accommodation space and the ability of each system to store and release sediments. Modelled sediment discharge and χpara (lake sediments) display similar histories, and thus are both interpreted as reflecting variations in detrital sediment supply. Intriguingly the style of modelled sediment discharge from the Ire, a confined mountain torrent, displays a greater similarity to and perhaps dominates the lake sediment record. These results provide partial validation of the CAESAR model and indicate that perhaps in the future it may be used as an exploratory and predictive tool in determining the impact of changes in climate, meteorology and land use on lake-catchment systems. [ABSTRACT FROM AUTHOR]

The long-term goal of pollen analysis has always been the reconstruction of past vegetation mosaics. However, the pollen signal is spatially integrated, and ecologically distinct vegetation structures can produce identical pollen signals. This paper proposes an iterative approach to reconstruction, the Multiple Scenario Approach, which involves creating a large number of hypothetical landscapes using a combination of deterministic and probabilistic 'rules' for plant placement coupled with environmental parameters such as topography, simulating the pollen assemblage produced by each, and comparing them statistically with a sedimentary pollen signal to identify possible reconstructions. The method expressly aims to find multiple possible reconstructions, and also gives some insight into the spatial aspects of the vegetation being reconstructed in addition to its composition. [ABSTRACT FROM AUTHOR]

This paper presents the anthracological results of Cova de la Guineu. This cave, which is located at the NE of the Iberian Peninsula, has provided charcoal samples from the early Neolithic to the Iberian period enabling the identification of different phases on the basis of flora assemblage interpretation. The results show how Mediterranean forests have been present since the early Holocene stages. At the early phases of the sequence the assemblage records dominant meso-screrophyllous taxa (deciduous Quercus, Taxus baccata), then thermophilous taxa (evergreen Quercus) spread, and finally a late phase of transformation dominated by thermophilous and heliophilous taxa (Mediterranean Pinus). The interpretation and discussion deals with the development and transformation of primary and secondary forests due to human disturbances and climatic variations. The anthracological record from Cova de la Guineu suggests that both elements were important and define the evolution of vegetation during the Holocene in the region. [ABSTRACT FROM AUTHOR]

The steep outlet glaciers of Jostedalsbreen, western Norway, are good examples of sensitively reacting maritime mountain glaciers. Their changes in length, frontal position and lower tongue's morphology during the past 20 years have been well documented. At first they experienced a strong frontal advance. After AD 2000 glacier behaviour was dominated by a strong frontal retreat, in some cases causing a separation of the lowermost glacier tongue. In this paper, the glacier length changes are presented both visually and numerically, supplemented by mass balance and meteorological data. The glacier behaviour is interpreted and its causes are discussed. Whereas the factors controlling the advance during the 1990s seem clear, the interpretation of the most recent retreat still leaves some uncertainties. The actual glacier front behaviour cannot fully be related to the mass balance data. Terminus response times and relations between individual mass balance and meteorological parameters have changed. Some hypotheses are given, including disturbance of the 'normal' mass transfer and dynamical response of the glacier front because of excessive ablation on the lowermost glacier tongues and summer back melting. These findings underline the sensitivity of maritime glaciers to climate changes. The empirical findings need to be taken into account in the interpretation of recent glacier length changes and their future modelling. [ABSTRACT FROM AUTHOR]

Abductive reasoning is the central form of explanation in environmental reconstruction. This paper outlines the nature of the abductive method restating it in Bayesian terms, ie, in terms of a priori belief based on context and the relations between multiple proxies. A key role within this working method is played by evidence and, in particular, proxies of the past in the explanatory framework. Proxies, whether singularly or as groups, are interpreted within the context of the event, and the derived hypothesis, for which they have evidential claim. They are not considered as independent entities but rather as inter-related pieces of information concerning the likelihood of specific events. The degree of belief in an individual proxy is based on the interplay between the belief in the hypothesis before the proxy is considered and the relations and belief in the cluster of proxies of which the individual proxy is usually a part. [ABSTRACT FROM AUTHOR]

This paper presents the results of simulated pollen counts from the central Scandes Mountains in Sweden which are used to examine the application of a pollen-based modelling approach to treeline fluctuations. Treelines are considered sensitive indicators of climate variability, and greater consideration of the palynological signal of treeline fluctuations is important in critical and rigorous use of pollen analysis to reconstruct variations in treelines. The approach presented here is to construct GIS-based models of the landscape (based on topographic and land cover attributes) onto which placement of different vegetation communities can represent changes in treelines in space (by adjusting the altitudinal positioning of treelines) and time (by using five time slices through the Holocene). The application of the POLLSCAPE model of pollen dispersal and deposition is then applied to generate simulated pollen counts for a large number (121) of sites placed across an altitudinal range in the simulated landscape. Comparison of simulated data to empirical pollen data from the region validates the approach through reasonable matching of the main trends in the pollen data sets. The success of the modelling approach is that it has helped to refine the process by which variations in fossil pollen assemblages are constructed, and also provides a tool by which the optimum sampling locations can be determined for treeline-focused work. [ABSTRACT FROM AUTHOR]

This paper reconstructs the evolutionary history of the Pearl River delta over the last 9000 years and investigates land-sea interaction in a large deltaic complex which formed under the influence of Asian monsoon climate. Specifically, this research examines the delta evolution in the context of three driving mechanisms: (1) rising sea level that influences the available accommodation space, (2) fluvial discharge as influenced by monsoon climate and (3) human activities that alter sedimentation within the deltaic system. Results reveal that the formation of deltaic sequences was initiated as a consequence of rapid sea-level rise between 9000 and 7000 cal. yr BP. The rate of sea-level rise slowed down markedly around 7000 cal. yr BP and sedimentation switched from transgressive to regressive. Initially, both the progradation of the delta plains near the apex and aggradation of delta front sedimentation in the central and lower parts of the receiving basin were fast owing to strong monsoonal-driven runoff. The progradation rate gradually slowed down between 6800 and 2000 cal. yr BP as monsoonal-driven runoff weakened. Rapid shoreline advances during the last 2000 years were the result of significantly increased human activities, a practice that trapped sediments in the encircled tidal flats along the front of delta plains. The evolutionary history of the Pearl River delta demonstrates the interplay between the three driving mechanisms. [ABSTRACT FROM AUTHOR]

The mixed semi-evergreen forests in lowland central equatorial Africa can contain many elements of secondary vegetation. This raises the question of what factors have determined the current forest composition in this region. Is this forest in the process of succession after natural climatic variation and/or anthropogenic disturbances in the past, or is it a stable forest type? This paper presents a multiproxy palaeoecological analysis of a sedimentary sequence taken from a small sedimentary basin located in logged semi-evergreen lowland forest in northern Congo-Brazzaville which addresses these questions. Analyses undertaken included fossil pollen, geochemical and microscopic charcoal. Geochemical results were interpreted as a proxy for rainfall, and showed that northern Congo has experienced changes in rainfall during the past 2580 years, while microscopic charcoal concentrations indicated increased burning from approximately 1240 cal. yr BP to the present. Analysis of the fossil pollen assemblages showed that although light-demanding taxa were a major constituent of this forest throughout the sequence, shade-tolerant taxa were more abundant in the forest prior to 1345 cal. yr BP. Increases in aridity and/or droughts after 1345 cal. yr BP, and an increase in fire after 1240 cal. yr BP resulted in a semievergreen forest with abundant pioneers that persisted with minor changes in composition during the last 900 years, even during a period of increased rainfall from 400 to 100 cal. yr BP. These data may guide conservation policy by predicting potential consequences of future climate change and the impact of logging. [ABSTRACT FROM AUTHOR]

In the coastal lowlands of Mozambique, an expansion of savannas at the cost of forests has been attributed to anthropogenic influence. There are few investigations that have studied vegetation dynamics over the long term. Pollen analysis from two sedimentary cores in the Chibuene area, 7 km south of Vilanculos presented in this paper show that the coastal area 1600 years ago consisted of a mosaic of forests, Miombo woodlands and grasslands. The data also show that the area supported extensive forests in the past until AD 1400-1600 when the forests declined dramatically. Changing settlement patterns, as suggested from archaeological excavations, cannot be correlated with the forest decline and the charcoal abundance, in the sedimentary cores does not suggest an intensification of farming. Instead the decline of forests appears to be temporally correlated with a prolonged period of repeated dry spells associated with the 'Little Ice Age', which caused a shift in vegetation whereby typical forest species as Trema, Celtis and Moraceae were outcompeted on account of the droughts. This study challenges rooted assumptions about the cause of decline of forests in the coastal region. It also suggests that the forest fragments present on the Mozambique coast today are naturally subject to threat from climatic stress and as such are highly sensitive areas to future climate change. [ABSTRACT FROM AUTHOR]

The late-Holocene deposits of the coastal lowlands bordering the southern North Sea were formed by a renewed expansion of the tidal environment replacing freshwater peats. The sea-level history during the last 2500 years inferred from the post-peat deposits, containing little to no datable organic material, is characterized by two conflicting schools of thought. The first one supports a smooth sea-level curve. The second approach underpins fluctuating sea-level changes. The 'fluctuating' approach also uses facies variations recorded in the post-peat deposits to provide a chronostratigraphical subdivision linked to transgressions and regressions. This paper examines the controlling factors responsible for the facies variations in the post-peat deposits in order to test the approach of the fluctuating sea level. The results of sedimentological investigation coupled with radiocarbon dates of intertidal shells from four shallow outcrops located in nearby sand-filled late- Holocene tidal channels in the Belgian coastal plain are reported. The integration with results from previous work has allowed the reconstruction of the mechanisms and processes of coastal evolution during the late Holocene. The changes in the coastal landscape reflected in the facies variations are caused by multiple factors. The major one is the dynamic nature of the tidal channels responding to changes in accommodation space and sediment budget, and finally, to storm incidence and human impact. The processes of the tidal channel networks, ie, their initiation and evolution, are similar, but the changes happened at different times in different places. The facies variations do not involve rises and falls of sea level, and therefore a fluctuating sea-level rise can not be considered as realistic. [ABSTRACT FROM AUTHOR]

This paper describes our recent attempt to isolate and analyse DNA from old plant remains of the common peatmoss Sphagnum fuscum retrieved from a peat core collected in the mire Fuglmyra, in central Norway. DNA was recoverable and usable from subfossilized (10-450 years old) plant remains of the peatmoss. A chloroplast (trnL) and two nuclear (ITS2 and RAPDf) regions were co-amplified from 80 samples of different ages. The RAPDf region was the only variable one with three different haplotypes found among five samples. Comparison of the ancient sequences with modern sequences found in the extant population occurring at the same site ascertained a genetic link between modern and fossil samples of this species. This retrieval of ancient DNA from subfossilized moss remains isolated from peat cores has important implications for the palaeoecology of peatmosses by allowing direct estimates of plant population dynamics in space and time. [ABSTRACT FROM AUTHOR]

Archaeological models of regional occupation for culture change in and the arrival of trade goods into, the Gulf Province of Papua New Guinea have largely relied on pioneering research undertaken in the 1970s, prior to the advent of AMS radiocarbon dating and from a time when excavation methods were relatively coarse-grained. These early chronologies were based on bulk radiocarbon samples potentially incorporating materials from multiple periods of occupation, and freshwater shells 'contaminated' by old carbon from regional Miocene limestones necessitating the application of correction factors of uncertain local applicability. This paper revises chronological aspects of pre-European contact history for the mid-Kikori River region of the Gulf Province. It presents a suite of 100 new AMS radiocarbon dates on individual pieces of charcoal, human teeth and a fish bone from 16 sites, in order to re-assess previous chronologies and understandings of the region's history, and to provide a new foundation for future modelling of site and regional land use. Past settlement systems in this region were guided by processes of social interaction and thus need to be interrogated through notions of social landscape in historical perspective. [ABSTRACT FROM AUTHOR]

This paper reviews the late Holocene archaeology of Central Australia. The last 1500 years saw significant changes in the archaeological record in this part of the Australian arid zone, with shifts in settlement pattern, site histories, resource use, tool inventories and rock art. Much of the evidence points to regional population growth, beginning 1500-1000 cal. BP and coinciding with expansion of summer-rainfall grassland and more frequent palaeoflood events. Hunter-gatherer groups appear to have increased their use of marginal or outlying areas as these became seasonally accessible. Responses to the demographic changes, especially in the better-watered ranges, include more extended occupation of existing sites, more processing of acacia and grass seeds, and an increase in territoriality reflected in the greater differentiation of rock art complexes after 1500 cal. BP. The archaeological changes are not scaled commensurately with the modest environmental shifts at this time, indicating that human-environment interactions were not linear. A human-environment threshold may have been breached 1500-1000 years ago, with existing socio-economic or historical factors acting to amplify the effects of small environmental changes. However, it remains difficult to fully characterize the nature of these human-environment interactions, despite the fine-grained archaeological record now available. An unresolved problem for this emerging picture of climatic amelioration and population growth is that Aboriginal settlement in Central Australia was expanding at a time when ENSO-driven variability appears to have been at its highest. [ABSTRACT FROM AUTHOR]

The Gunditjmara people developed a socio-economic system based on the modification of wetland ecosystems associated with the Mt Eccles lava flow primarily for sustainable production and management of the highly nutritious shortfin eel (Anguilla australis). This paper examines the environmental history of these landscapes since their inception about 30 000 years ago, through palaeoecological analysis of sediment cores from associated lakes and swamps, in order to contribute to an understanding of the causes and timing of cultural transformation. Two records cover the whole of the 30 000 year history of the landscape while two others provide evidence of change within the Holocene. A great deal of variation within the landscape is revealed, both temporally and spatially, with opportunities for human exploitation through the whole recorded period. Although most features of the records can be explained by natural landscape development and climate change, some human modification can be suggested from around the Pleistocene-Holocene transition while more obvious indications of management relating to eel aquaculture are evident from about 4000 cal. yr BP that appear to include adaptations to the onset of a drier and more variable climate. The study has implications for the explanation of intensification of settlement in Australia more generally within the mid to late Holocene. [ABSTRACT FROM AUTHOR]

This paper interprets macroscopic charcoal (>250 μm), humification and loss-on-ignition over the last ∼14 200 cal. BP from Goochs Swamp, located to the west of Sydney in the Greater Blue Mountains World Heritage Area. This study aimed to investigate relationships between humans, climate and fire through time, primarily by comparison of these palaeoenvironmental indices with archaeological evidence from the region. Climatic forcing can explain all periods of change in the history of fire at Goochs Swamp: fire activity was variable during the Lateglacial-Holocene transition, low during the relatively stable climate of the early Holocene, and high but variable after the onset of modern El Niño from the mid Holocene. Although the dominant control on fire in this environment during the Holocene appears to be climate, fluctuations in the late Holocene may reflect anthropogenic fire or human responses to climate change. The archaeological record of the Blue Mountains and other parts of the Sydney Basin illustrates that Aboriginal people altered subsistence, resource and land-use patterns in the late Holocene. We propose that these cultural measures were adopted to overcome new risks as the frequency of ENSO events increased, and the natural fire regime and resource reliability changed. These strategies perhaps included a more systematic use of fire. The most parsimonious interpretation of the evidence for changes in fire activity at Goochs Swamp in the light of nearby archaeological evidence is that Aboriginal people used fire within a changing climatic framework. [ABSTRACT FROM AUTHOR]

Successful reconstruction of vegetation from fossil pollen data in the arctic and alpine tundra, and at the forest-tundra ecotone, is hampered by low pollen production of the major taxa in these environments and the likely dominance of the background pollen component. New approaches to the quantification of vegetation from pollen data (the REVEALS and LOVE models) rely on quantification of background and local pollen by applying models of pollen dispersal and deposition to modern pollen-vegetation survey work. To date, research within this emerging area has focused on lowland environments. This paper presents pollen productivity estimates (PPEs) from the forest-tundra ecotone derived from west central Sweden, discusses the relevant source area of pollen (RSAP) in this environment and estimates the background pollen contribution. The results suggest that the RSAP for moss polsters at the forest-tundra ecotone is c. 500 m, and that PPEs for the major forest tundra ecotone taxa show significant differences compared with previous studies from southern Sweden. Proximity to range limits (controlled by climatic factors) appears to be the main factor causing generally lower pollen production; however, individual taxa respond in different ways, depending on differences in growth behaviour, reproductive strategy and the species and subspecies that represent the pollen taxa. The background pollen component was dominated by arboreal taxa, and contributed c. 60% of the total pollen loading. Graminoids dominated the local component. The PPEs presented here are to date the most appropriate parameters to use for quantification of vegetation at the tundra treeline; however, the data demonstrate that caution needs to be exercised with regards to selection of appropriate PPEs for accurate quantification of taxa at their ecological range. [ABSTRACT FROM AUTHOR]

On the basis of sediment and pollen analyses of a radiocarbon-dated sediment sequence from Lake Joux in the Swiss Jura Mountains (west-central Europe), this paper presents a high-resolution record of lake-level and vegetation changes for the last millennium. The lake-level record makes it possible to determine that lowstands of the water-table dominated at c. AD 1200-1400, and from 1720 onward, with interruptions by short-lived rise events at c. AD 1340 and 1840. Highstands prevailed at c. AD 1100, and around AD 1450, 1550 and 1700. The comparison of the Joux lake-level record with a solar irradiance record based on cosmogenic nucleides supports the hypothesis of a major solar forcing of climate variations in west-central Europe over the last millennium. In agreement with other palaeohydrological records established in Western Europe and in the central North Atlantic Ocean, the Joux lake-level record suggests that, on a multicentennial scale, the period of the 'Little Ice Age' coincided in the European mid-latitudes with wetter climatic conditions, and probably with an increase in summer precipitation. Variations in the hydrological cycle appear to have been associated with changes in the general atmospheric circulation pattern, probably coupled with variations in oceanic circulation and solar activity. The Joux record also points to changes in water resources expected to result from ongoing global warming. Finally, despite the severe climatic conditions which prevail in the Joux Valley, the human impact history at Lake Joux over the last millennium seems to reflect political choices and economic context more than climatic changes. [ABSTRACT FROM AUTHOR]

Frank Oldfield's immense contribution to palaeoenvironmental science is summarized in relation to: pollen analysis, vegetation history and peat stratigraphy; palaeolimnology and 210Pb dating; environmental magnetism, catchment-lake relationships and soil erosional history; multiproxy approaches; PAGES; and editing The Holocene. The tribute includes an introduction to the 14 other papers in this Special Issue, which were inspired in diverse ways by this remarkable scientist. [ABSTRACT FROM AUTHOR]

This paper reviews the 210Pb dating programme carried out at the University of Liverpool over a period of three decades since its inception by Frank Oldfield in the mid-1970s. The work at Liverpool has included studies of the basic processes controlling the supply of 210Pb to the various natural archives, as well as the development of a detailed and systematic methodology for dating the environmental records in these archives. The assumption that 210Pb fallout at any given location is constant when measured on timescales of a year or more has been tested using data on 210Pb concentrations in UK rainwater spanning more than 40 years, and a simple atmospheric model developed to account for observed spatial variations in the flux over large land masses. The basic assumptions of the CRS dating model have been tested in detail using mass balance studies of fallout radionuclides in catchment/lake systems, and in general using data from a large number of separate studies. The Liverpool data base is used to illustrate the wide ranging applicability of the 210Pb dating method. Results are shown from lakes varying in size from the very small to the very large, and with sedimentation rates ranging from the very fast to the very slow. The particular difficulties of dating sediment records from Desert Lakes and Polar Regions with very low atmospheric fluxes are discussed, with unexpected results in some cases. [ABSTRACT FROM AUTHOR]

The paper explores the use of Resilience Theory to provide an improved theoretical framework for the analysis of socio-ecological interactions over decadal—millennial timescales. It identifies landscape system behaviour through analysis of proxy records for land use, erosion and monsoon intensity over the past 3000 years in the Erhai lake-catchment system, Yunnan, SW China. Analysis of the records shows the possibility of alternative steady states in the landscape, as expressed by the relationship between land use and erosion. In particular, a period of agricultural expansion ~1400 cal. yr BP triggered rapid gully erosion that led to the formation of an eroded landscape state that has existed since ~800 cal. yr BP to the present day. Comparison of detrended time-series data suggests that over 3000 years erosion and land use should be considered 'slow' processes relative to the 'faster' monsoon intensity and flooding. In the past, the effects of high monsoon variance on flooding have been suppressed by paddy farming and the maintenance of terraced field systems. Mapping the Adaptive Cycle on to the millennial record of land use and erosion suggests that the modern landscape may be approaching a 'conservation' phase characterized by minimum resilience. Such 'historical profiling' of modern landscapes offers a new dimension for hypothesis testing, for the development and testing of simulation models and for the creation of appropriate management strategies. [ABSTRACT FROM AUTHOR]

A key concern in the assessment of the recovery of acidified lakes from the effect of acid deposition is the reference pH of acidified lakes and how reference values can be used to establish targets for restoration. In this paper we evaluated the accuracy of three different, although overlapping, diatom-pH transfer functions using UK Acid Waters Monitoring Network (AWMN) data to compare inferred pH from diatoms collected in annually exposed sediment traps with measured water column pH for 11 acid-sensitive lakes. We then used these transfer functions to infer lake-water pH from approximately AD 1850 (taken as the reference date) to AD 1990 (the core-top date) for radiometrically dated sediment cores from each site. When applied to the sedimenttrap samples all three models tended to underpredict measured pH in the less acidic sites, with the SWAP model being the most biased. All three models were in good agreement in reconstructing pH for the AD 1850 reference period. Reference pH varied between sites from approximately 4.9 to 6.4, and was correlated with modern basecation status. In the acidification phases of the cores discrepancies in pH inference between models appear to be linked to differences in pH optima for a minority of taxa. Current (2006) diatom-inferred pH values from the most recent sediment traps, when compared with sediment core tops, provide evidence of recovery at most sites but its extent, so far, is slight when compared with the reference period. The substantial difference between sites in their reference conditions indicates clearly that recovery success can not be measured against a single target pH or, by inference, ANC value and must be assessed on a site-specific basis. [ABSTRACT FROM AUTHOR]

This paper is a response, both to Fuller et al.'s recent criticism of Chinese research on rice domestication, as lacking evidence, and to their argument for the beginning of rice domestication around 4000 BC in the lower Yangzi River. We first survey previous publications that discuss the process from wild rice collection to rice domestication in China, and then examine early rice remains from the perspectives of rice morphology and archaeological context. We focus on three aspects: the timing of the initial rice domestication in the Yangzi River region; the earliest presence of domesticated rice in the Lower Yangzi and Huai River regions; and the implications of changes in rice grain sizes in archaeological assemblages. We also discuss problems relating to the presence of immature rice remains in the archaeological record, grain size increase and overall grain shape, which are three of the criteria used by Fuller et al. for distinguishing domesticated from wild rice. Based on published data and our research on rice, we demonstrate that by the early Holocene (9000 cal. BP), Neolithic people in both north and south China may have been harvesting wild rice and initiating rice cultivation that eventually led to domestication. [ABSTRACT FROM AUTHOR]

Abstract: A total of 237 surface soil pollen samples were collected from less disturbed zonal communities, and a new surface pollen data set has been established in northern China. Pollen-climate parameter transfer functions using weighted-averaging regression and calibration partial least squares (WA-PLS) model as a tool to reconstruct past climate changes from pollen data, were tested with this new surface pollen data set. The results of cross validation showed that the method worked very well with precipitation (R = 0.94, R2 jack = 0.89, RMSEPjack = 69 mm, the safe dynamic range of the reconstruction was 40 mm~800 mm) and worked well with temperature (Tann: R = 0.84, R2 jack = 0.71, RMSEPjack = 2.0°C, the safe dynamic range of the reconstruction was -4°C~13°C; MTwa: R = 0.79, R2 jack = 0.63, RMSEPjack = 2.5°C, and the safe dynamic range of the reconstruction was 8°C~26°C), indicating that the surface pollen data set and WA-PLS reconstruction technique in this paper have strong potential for palaeoclimatic reconstruction. [ABSTRACT FROM AUTHOR]

The lower Yangtze, eastern China, was colonized by several Neolithic and Bronze Age cultures giving rise to possibly the highest concentration of prehistoric sites in the world. Early Neolithic cultures in the delta region cultivated rice (Oryza sativa) and agricultural developments appear to have occurred throughout the Neolithic with abrupt socio-economic changes possibly associated with the terminal Neolithic. Given the extensive history of environmental exploitation and well-preserved archaeological sites, the Yangtze delta is an ideal setting to explore the complex interactions between humans and their environment. Multiproxies of environmental changes, namely pollen, charcoal and phytoliths, in a 14C AMS-dated sequence of sediments from an exposed profile at Qingpu, Yangtze delta, were investigated. 14C AMS dating indicates that the age range of the sedimentary sequence analysed is from c. 1800 to 6000 BP, and therefore encompasses the terminal Neolithic and subsequent Bronze Age in the region. This paper reviews this sediment-based evidence in the light of current understanding of human-environment interactions during a critical phase of the development of the Yangtze delta and associated human cultures. [ABSTRACT FROM AUTHOR]

The modern floristic composition of the principal raised bogs of Wales is significantly altered compared with their histories of development from the early to mid Holocene. This paper uses pollen and plant macrofossil records from two raised bogs together with previously published data from a further two sites to explore the key factors contributing to the present condition of Welsh ombrotrophic plant communities. Results show Betula and Molinia invasion is a recent feature of bog development in Wales. Previous Holocene ‘dry-phases’ were characterized by Ericaceae and Pinus establishment, supporting recent experimental evidence that Betula and Molinia encroachment is primarily a response to nitrogen (N) loading rather than desiccation on intact bogs. Several of the bogs featured in this study also show severe signs of structural damage, not only from peat cutting but, in the case of Cors Caron, from channel processes in the adjacent River Teifi. Radiocarbon dating and inter-site comparisons of peat accumulation rates show that Rhos Goch Common in particular has been heavily impacted by peripheral peat cutting, leading to dewatering, significant subsidence of its peat dome and the spread of hummock and high dry ridge communities. Finally, the decline and local extinction of Sphagnum austinii in bogs across Europe represents one of the most significant changes in ombrotrophic community composition in the late Holocene. Co-registered pollen and macrofossil evidence from Cors Caron demonstrates that increases in landuse intensity over the last 2000 years are temporally associated with reductions in the abundance of S. austinii and ultimately its local disappearance from the palaeoecological record. [ABSTRACT FROM AUTHOR]

Pollen analysis of a 48 m AMS radiocarbon-dated sediment sequence from the Guadiana estuary provides the first record of Lateglacial and Holocene vegetation history in the Algarve province of Portugal. This paper focuses on the record of terrestrial pollen taxa, which document a series of forest expansions and declines during the period 13 000 cal. BP to 1600 cal. BP and provide insights into climate evolution in southwestern Iberia. The main vegetation phases identified in the Guadiana valley are (1) Lateglacial interstadial (Allerød) forest with Quercus and Pinus under a temperate, moist, continental climate; (2) a Younger Dryas forest decline (Quercus) and expansion of pinewoods, xeric scrub and open ground habitats (with Juniperus, Artemisia, Ephedra distachya type, Centaurea scabiosa type) under arid and cold conditions; (3) an early Holocene forest/scrub/open-ground vegetation mosaic developing under a warm, dry and continental climate; (4) a maximum of Quercus forest and thermomediterranean evergreen taxa (Olea, Phillyrea, Pistacia) reflecting a warm, moist oceanic climate between c. 9000 cal. BP and c. 5000 cal. BP; and (5) the expansion of shrublands with Cistaceae and Ericaceae under a drier climatic regime and increasing anthropogenic activity since c. 5000 cal. BP. Holocene episodes of maximum climatic aridity are identified in the record of xerophytic taxa (Juniperus, Artemisia, Ephedra distachya type) centred around 10 200 cal. BP, 7800 cal. BP, 4800 cal. BP, 3100 cal. BP and 1700 cal. BP. Regional comparisons suggest a correlation of arid phases across southern Iberia and northwest Africa, which can be related to abrupt North Atlantic coolings (Bond events). [ABSTRACT FROM AUTHOR]

The paper uses Greenland GISP2 ice core data together with historical documentary information to investigate the nature of climate changes that took place between AD 1270 and 1450 across the North Atlantic region. Detailed Deuterium and deuterium excess time series resolved to c. 8–10 samples per year are used to reconstruct relative changes in Greenland air temperature and past changes in sea surface temperature across the western North Atlantic. The data show that sea surface temperatures during the late thirteenth century and the majority of the fourteenth century were characterized by relatively high-amplitude warming and cooling ‘events’. These changes preceded a marked reduction in the amplitude of the sea surface temperature changes c. 30–40 years before the well-known change in Northern Hemisphere tropospheric circulation characterized by a marked increase in regional storminess that started between c. AD 1400 and 1420. The time interval between AD 1270 and 1450 also appears over Greenland to have featured several short-lived phases of marked air temperature lowering that were rarely ever equalled during succeeding centuries. We believe that the climate changes described here are of considerable importance in understanding climate dynamics of the North Atlantic region since they took place at a time when the North Atlantic Oscillation (NAO) may have been weak. The results also show that the marked change in atmospheric circulation coincident with a significant increase in North Atlantic storminess at c. AD 1400–1420, possibly the biggest such change in the Holocene, took place after the strong perturbations in North Atlantic sea surface temperature (both warming and cooling) described here as well as after several episodes of air temperature lowering over Greenland. [ABSTRACT FROM AUTHOR]

This paper reports the first detailed palaeogeographical analysis of the environmental context of late Mesolithic shell midden sites in the lower Tagus area and focuses on the lower Muge valley, which contains an internationally significant Mesolithic record. The lower Muge valley fill comprises buried estuarine and fluvial environments contemporary with Mesolithic settlement. Holocene environmental and palaeogeographic changes influenced Mesolithic settlement-subsistence and midden accumulation. The sudden appearance of large late Mesolithic shell middens throughout Portugal represents a process of increased visibility and preferential preservation of the archaeological record. Prior to ∼6100 cal. BC, aggrading valley floor environments did not occupy the entire width of the present lower Tagus floodplain and any sites located in the early Holocene valley are currently deeply buried. Shell midden occupation on terrace levels followed the establishment of aggrading estuarine environments, containing productive shell beds, near the mouth of the lower Muge valley at ∼6100 cal. BC. The critical factors in site choice appear to have been the nearby presence of (i) rich shell resources and (ii) freshwater environments. Long-term site occupation and (semi-)sedentary behaviour was favoured by the local presence, for over 2000 years, of rich resources from estuarine, freshwater and open woodland environments. Site abandonment (∼5300–4800 cal. BC) coincided with the regional establishment of an open landscape (∼5000 cal. BC) and the contraction of local estuarine environments (∼5555–3800 cal. BC). The associated gradual decrease in resources and cultural interaction with the expanding early Neolithic communities may have influenced Mesolithic site abandonment. [ABSTRACT FROM AUTHOR]

Quantitative reconstruction of past vegetation is one of the primary goals in Quaternary palynology and palaeoecology but still remains difficult. This paper proposes a model, REVEALS, that estimates regional vegetation composition using pollen from ‘large lakes’ that have small site-to-site variations of pollen assemblages even if vegetation is highly heterogeneous. Once these data have been used to quantify regional vegetation composition within 104-105 km², background pollen, one of the parameters crucial for vegetation reconstruction, can be estimated for smaller-sized sites, and incorporated into the Landscape Reconstruction Algorithm (LRA), a multistep framework for quantitative reconstruction of vegetation in smaller areas (≤/104 ha). Simulations using the POLLSCAPE modelling show that REVEALS can provide accurate estimates of regional vegetation composition in various landscapes and under different atmospheric conditions. If pollen assemblages from lakes that are much smaller than ‘large lakes’ are used, estimates of regional vegetation at individual sites could be significantly different from the expected values, and their site-to-site variation could be large. However, when pollen data from multiple lakes ≥100-500 ha in size are available, REVEALS can provide accurate estimates of the regional vegetation with relatively small standard errors. Quantitative reconstruction of regional landscape and vegetation change will be critical for testing some of the controversial hypotheses and concepts in global change and conservation research, such as the impacts of agricultural activities on global climate over the last 8000 years and the open-woodland hypothesis in northern Europe in the early Holocene. [ABSTRACT FROM AUTHOR]

This paper presents two early Holocene (9.6-5.9 ka BP) high-resolution stable isotope records of stalagmites from two caves in northwestern Sweden (Korallgrottan and Labyrintgrottan). Close similarities between the Swedish records and a previously presented Norwegian stalagmite oxygen isotope record emphasize the potential of Scandinavian stalagmites to provide high-resolution regional palaeoclimatic information. The stable oxygen isotope records are interpreted to reflect the temperature evolution during the early Holocene with a gradual warming from c. 9.6 ka BP, interrupted by cooler conditions at 8.5-8.0 ka BP. The results indicate that the cooler conditions were driven by two to three abrupt cold events rather than one ‘8.2 event’ only. Except for these cold events the stalagmite oxygen isotope records show that temperatures in northwestern Sweden were warmer than today between 9.6 and 5.9 ka BP and that during this period the interval between 7.8 and 5.9 ka BP seems to have been the warmest. The high-amplitude changes in the stable carbon isotope record of Labyrintgrottan are proposed to reflect changes in local vegetation. The area above Labyrintgrottan was most likely covered by much denser vegetation than today at the time of stalagmite growth (9.5-7.5 ka BP) and was — unlike today — probably situated below the local tree limit between 9.0 and 8.0 ka BP. [ABSTRACT FROM AUTHOR]

This paper describes the LOVE (LOcal Vegetation Estimates) model for estimating local vegetation composition within the relevant source area of pollen. This model quantifies and then subtracts background pollen (ie, pollen coming from beyond the relevant source area) in order to arrive at a quantitative reconstruction of local vegetation. Parameters required for LOVE applications are pollen counts from target sites, the relevant source area of pollen of these sites, pollen productivity estimates and regional vegetation composition within 104-105 km². Regional vegetation composition is obtained using fossil pollen from large sites (≥/10² ha) with the REVEALS (Regional Estimates of VEgetation Abundance from Large Sites) model, the first step of the Landscape Reconstruction Algorithm (LRA) specifically designed for LOVE applications. POLLSCAPE simulations demonstrate that (1) regional vegetation composition can be used to predict background pollen at and beyond the relevant source area of pollen for given-sized basins, (2) LOVE with the LRA framework provides a robust and accurate estimate of local vegetation composition much better than vegetation reconstruction using pollen percentages alone and (3) although the relevant source area of pollen is difficult to estimate particularly in past landscapes, a proposed method using backward modelling of LOVE is effective to estimate the relevant source area in landscapes of unknown vegetation patchiness and heterogeneity. Thus, the LRA will also be useful to estimate indirectly changes in spatial structure of past vegetation and landscape caused by natural and anthropogenic forcing. [ABSTRACT FROM AUTHOR]

Interpretation of proxy-climate records depends on a thorough understanding of the proxy—climate relationship. Peatland surface wetness records have been interpreted as reflecting changes between cool and/or wet conditions and warm and/or dry conditions. This paper analyses a high-resolution record of reconstructed water-table changes based on testate amoebae analysis in relation to instrumental weather records since AD 1775. Replicate peat records are reconciled by multiple chronological techniques and tuning, and demonstrate that the reconstructions preserve many replicable high-frequency changes. Watertable variability is highly correlated with the total seasonal moisture deficit (precipitation — evapotranspiration, P-E) expressed as the sum of all months with negative P-E. The reconstructed water-table record reflects antecedent periods of 5 or 10 years (maximum r² = 52.4%) and proxy bog surface wetness records can therefore be interpreted as reflecting the length and intensity of the summer water deficit period. Response surfaces of the summer deficit in relation to temperature and precipitation variability support the hypothesis that the summer deficit is determined by summer precipitation in mid-latitude oceanic peatlands and that summer temperature plays a greater but still subsidiary role in higher latitude, continental settings. These relationships apply for all plausible past Holocene climate changes and future twenty-first century climate scenarios. Non-linear responses to longer-term climate states prevent the direct application of a calibration of the reconstructed water-table records to infer quantitative estimates of climate variables. Models that combine peat accumulation, mire growth and hydrological processes are required to undertake this task. [ABSTRACT FROM AUTHOR]

This paper describes the potential of correcting the 14C age shift resulting from the contamination of primary aragonites by detrital carbonates using online sequential extraction of CO2. The experiments were carried out on laminated lacustrine aragonites collected from Holocene Dead Sea sediment sections. X-ray diffraction analysis revealed the presence of detrital calcite interpreted to originate from the watershed and transported to the lake with runoff. The contamination could not be separated physically from the sample, potentially contributing decayed 14C (‘dead carbon’) and increasing the age of the aragonite. Sequential extraction of successive fractions of CO2 unveiled the effect of detrital material on the 14C ages, and showed that the first CO2 extract represents the least contaminated 14C fraction that provides the best approximation for the true 14C age (which includes the lake's reservoir age). We calculated the age offset contributed by the contamination range encountered in this study (1–21%) to be about 900 years per 10% contamination. The sequential extraction procedure is recommended for 14C dating of Holocene age lacustrine carbonates suspected to be contaminated with extraneous carbon-bearing materials. [ABSTRACT FROM AUTHOR]

This paper describes an approach that gives an estimate of the reconstructive skill of a proxy-based palaeoclimatological reconstruction. Uncertainties in proxy data are likely to be reflected in variations in reconstructive skill of the proxy-based climatic reconstructions. The method is based on making an ensemble of reconstructions, providing a probability distribution of each reconstruction estimate. The relative breadth of the distribution for a particular reconstructed value should give an indication of the reconstructive skill. The ensemble reconstruction approach draws on the ensemble prediction system as used for operational weather forecasting. The ensemble reconstruction approach is tested using a recent multiproxy reconstruction of the winter North Atlantic Oscillation (NAO) index. It is shown that the ensemble approach provides a representation of the degree of certainty associated with the reconstructed NAO-index values. [ABSTRACT FROM AUTHOR]

This paper describes our recent extraction of ancient DNA (aDNA) from Holocene pollen and discusses the potential of the technique for elucidating timescales of evolutionary change. We show that plastid DNA is recoverable and usable from pollen grains of Scots pine Pinus sylvestris from 10 ka and 100 years ago. Comparison of the ancient sequences with modern sequences, obtained from an extant population, establish a first genetic link between modern and fossil samples of Scots pine, providing a genetic continuity through time. One common haplotype is present in each of the three periods investigated, suggesting that it persisted near the lake throughout the postglacial. The retrieval of aDNA from pollen has major implications for palaeoecology by allowing (i) investigation of population-level dynamics in time and space, and (ii) tracing ancestry of populations and developing phylogenetic trees that include extinct as well as extant taxa. The method should work over the last glacial oscillation, thus giving access to ancestry of populations over a crucial period of time for the understanding of the relationship between speciation and climate change. [ABSTRACT FROM AUTHOR]

The Western Liaohe River Basin in northeastern China is one of the cradles of ancient Chinese civilization. Archaeological records from this region indicate that human occupation began about 8000 years ago and that agriculture and pastoralism were important activities from an early stage. Very little is known, however, about the effects that these activities had upon the landscape. This paper presents the results of a palaeoecological study from a 3.6 m sedimentary sequence in a relict oxbow lake in the Western Liaohe River Basin of southeast Inner Mongolia. The 5400-yr sequence indicates that human activities had a noticeable impact on an apparently open landscape. Buckwheat cultivation began as early as 5400 cal. yr BP with intensification of agricultural activities from approximately 4700 cal. yr BP. Nitrophilous plants such as Solanum and Cerastium, and also Artemisia were growing in the region at certain times, linked with fluctuations in the δ15N record and probably indicative of increased pastoralism and unintentional/intentional manuring. Burning was probably used for clearance of the steppe vegetation for agriculture with a close relationship apparent between increased influx of microfossil charcoal and the presence of buckwheat. Superimposed upon this record of human impact is also clear indication of three significant intervals of climate change between 2900 and 2600, 1200 and 600 and 600 and 30 cal. yr BP. The latter two are discussed in relation to the 'Mediaeval Warm Period' and 'Little Ice Age' apparent in sedimentary sequences across the Northern Hemisphere. Discussions are therefore made in terms of the impact that both climate change and ancient Chinese civilizations had upon shaping the present day landscape and vegetation. [ABSTRACT FROM AUTHOR]

Relative sea-level changes in southwest Britain are poorly constrained because of limitations in the quality and quantity of existing geological data. As a consequence, in contrast to most other regions in the UK, it is not possible to reliably infer rates of land and sea-level change during the last few thousand years. Furthermore, geologically based sea-level reconstructions from this area display significant misfits with relative sea-level predictions based on a recent global model of the glacio-isostatic adjustment process. This paper presents a new record of relative sea-level change for the last 4000 years derived from radiocarbon-dated sea-level index points. In addition to providing information concerning the pattern and rates of late Holocene sea-level change, these data are used to evaluate the suggestion that the apparent misfits between model predictions and geological reconstructions can be satisfactorily explained as a consequence of the lowering of sea-level index points by sediment compaction. The results indicate that a simple, first-order method of decompaction based on the stratigraphic position of sea-level index points, can eliminate much of the misfit between reconstructions and predictions, and substantially reduce vertical scatter in geological data. They also suggest that the influence of compaction on sea-level data from this region may be larger than previously thought. The simple addition of reliable stratigraphic data, in combination with targeted sampling, has the potential to improve our understanding of the compaction process, and increase the utility of existing data. This is increasingly important as the partnership between geophysical modelling and geological investigation becomes more commonplace in sea-level studies around the world. [ABSTRACT FROM AUTHOR]

Long tree-ring chronologies have been constructed in the Northern Hemisphere for dendroclimatology and palaeoenvironmental studies, radiocarbon calibration and archaeological dating. Numerous tree-ring chronologies have also been built in the Southern Hemisphere, primarily for dendroclimatology, but multimillennial chronologies are rare. Development of long chronologies from the Southern Hemisphere is therefore important to provide a long-term perspective on environmental change at local, regional and global scales. This paper describes the extension of the New Zealand Agathis australis (kauri) chronology from AD 911 to 1724 BC. Subfossil (swamp) kauri was collected from 17 swamp sites in the upper North Island. Kauri timbers were also obtained from an early twentieth century house on the University of Auckland campus. Twelve site chronologies and 11 independent tree-sequences were constructed and crossmatched to produce a 3631-yr record, which was calendar dated to 1724 BC–AD 1907 against the modern kauri master chronology. A new long chronology, AGAUc04a, was built by combining the modern kauri data with house timbers and subfossil kauri. This new chronology spans 1724 BC–AD 1998. It is of similar length to chronologies from Tasmania and South America and is the longest tree-ring chronology yet built in New Zealand. The greatest significance of the long kauri chronology lies in its potential as a high–quality palaeoclimate proxy, especially with regard to investigation of the El Niño–Southern Oscillation phenomenon. The chronology also has application to investigation of extreme environmental events, dendroecology, archaeology and radiocarbon calibration. [ABSTRACT FROM AUTHOR]

This paper draws on a newly developed source of data in the form of ships' logbooks to cast a detailed light on the weather and climate of a critical period in recent climatic history: the decades of the 1680s and 1690s, possibly the coldest of the last 1000 years. Logbooks of the period provide daily data for wind force, direction, precipitation and general weather conditions. These were abstracted and aggregated into monthly statistics. These data indicate the highly episodic character of air flow patterns at this time, with marked changes of phase between high and low zonality in the westerlies. The data also provide evidence of the stormy character of the period, particularly with respect to summer conditions. Comparisons are made with contemporary and independently derived instrumental and proxy series. The data source is confirmed as providing a valuable addition to climatic sources, and is additionally important because it is based on regular daily observations and made at sea – an area very poorly represented for this time period. [ABSTRACT FROM AUTHOR]

This paper reviews recently published literature, most of which was published in Chinese, and searches for regional patterns of Holocene changes useful in depicting global patterns. The Holocene in the Xinjiang region can be divided into three stages: a warming and dry early stage (from 11 ∼ 10 to 8 ∼ 7 ka BP), a warm and wet middle stage (from 8 ∼ 7 to 4.5 ∼ 3 ka BP) and a fluctuating cool and dry late stage (since 4.5 ∼ 3 ka BP). The Holocene in the northern Tibetan Plateau can also be divided into three stages: a warming and wet stage (from 10.5 ∼ 10 to 5 ∼ 4 ka BP), followed by a variable drying and probably warm stage (5 ∼ 4 to 3 ka BP) and ending with a cool and dry stage (since 3 ka BP). In the Inner Mongolian Plateau, the early Holocene (from 10.5 ∼ 9.5 to 8 ∼ 7.5 ka BP) was warming and dry, and a warm and wet climate occurred from 7.5 to 3.5, during which the best time was 6.3–3.8 ka BP; the climate has been variably drying and probably cooling since 3.5 ka BP. In the northwestern part of the Loess Plateau, several Holocene palaeosols have been identified (10–9, 7.5–5, 4–3 and 2.7–2 ka BP) with the 7.5–5 ka BP palaeosol being most strongly expressed. The best-developed palaeosol-equivalent in major valleys is a swamp-wetland facies deposited between 8885 and 3805 14C yr BP under an extremely wet regime. The climate has fluctuated significantly at least three times around a dry and probably cool regime after the swamp-wetland facies-depositional period. Our summary shows that the Holocene Climatic Optimum occurred nearly contemporaneously (8–5 ka BP) at all sites in the Xinjiang region, in the Inner Mongolian Plateau and in the northwestern part of the Loess Plateau. A warming and wet early Holocene (10–8 ka BP) in the northern Tibetan Plateau is most likely related to high effective soil moisture resulting from snow and ice melting. We propose here that the middle Holocene Climatic Optimum (8–5 ka BP) in arid to semi-arid China was primarily a delayed response of the low latitude oceans to high latitude peak insolation (9–8 ka BP). [ABSTRACT FROM AUTHOR]

This paper presents the first probability-based record of flooding in Europe that spans the entire Holocene. An analysis of 506 14C dated fluvial units collected across the whole of Great Britain provides a novel and robust methodology for improving flood risk assessment by geographically and temporally extending the record of extreme flood events. Sixteen episodes of increased flooding occurrence are identified, 12 of which (at c. 11 160, 5730, 4840, 4520, 3540, 2730, 2550, 2280, 1950, 1290, 660, 570, cal. BP) are recorded in most regions, whereas four phases (at c. 6820, 5540, 1650, 860 cal. BP) affected some parts of Great Britain more than others. In all regions large variations in flood frequency and magnitude occurred before forest clearance and indicate an underlying climatic control. During the mid-Holocene there is evidence for a hydroclimatic 'system switch', which in terms of catchment hydrology in Great Britain was marked by two sudden increases in both the frequency and severity of floods at c. 5000 cal. BP and, most notably, at c. 3000 cal. BP. The marked non-stationary behaviour of the British flood series at these times reflects a regional hydrologic response to large-scale ocean–atmospheric circulation changes superimposed on a pattern reflecting both long-term land-use change and the preferential preservation of later fluvial units. Centennial-scale variations in the occurrence of extreme flood events in Great Britain appear to be a sensitive indicator of past and present climate change in the North Atlantic region. [ABSTRACT FROM AUTHOR]

On the basis of glacier and lake-level records, this paper attempts, for the first time, a comparison between high-resolution palaeohydrological and palaeoglaciological data in west-central Europe over the past 3500 years. A data set of tree-ring width, radiocarbon and archaeological data, in addition to historical sources, were used to reconstruct fluctuations of the Great Aletsch, the Gorner and the Lower Grindelwald glaciers in the Swiss Alps. The three ice-streams experienced nearly synchronous advances at c. 1000–600 BC and AD 500–600, 800–900; 1100–1200 and 1300–1860. These glacier fluctuations show strong correspondence with lake-level variations reconstructed in eastern France (Jura mountains and Pre-Alps) and on the Swiss Plateau. This supports the hypothesis of elimatically driven fluctuations. Historical date available for the period since AD 1550 reveal, in detail, various meteorological conditions behind the succesive glacier advances. Howere, in agreement with the general trend shown by the historical data, the synchroneity between glacier advances and periods of higher lake level suggests the impact of general winter cooling and an increase in summer moistur as responsible for reinforced feeding of both glaciers and lakes in west-central Europe ;over the past 3500 years. Finally, comparison between the Great Aletsech glacier and the residual 14C records supports the hypothesis that variations in solar activity were a major forcing factor of climatic oscillations in west-central Europe during the last Holocence. [ABSTRACT FROM AUTHOR]

Interactions between Holocene environmental changes and human subsistence strategies in semi-arid parts of eastern Africa are relatively poorly understood because of a paucity of sites where contemporaneous archaeological and palaeoenvironmental records are preserved. This paper presents new AMS 14C-dated palaeoenvironmental evidence of mid- to late-Holocene vegetation changes, in the form of pollen, charcoal, mineralogical and δ13Cbulk data, from a floodplain location on the Laikipia Plateau, Kenya, and in the context of information on modern plant–environment relationships, existing and new archaeological and historical data, and published palaeoclimatic records. Although relatively poorly resolved, the evidence indicates more wooded and relatively humid conditions compared with the present from before c. 6600 BP to c. 1900 BP. Evidence for vegetation changes over the last two millennia is more finely resolved and indicates increased burning and the expansion of fire-modified Acacia bushland c. 1900 BP and grassland c. 1700 BP. Burning to improve and extend pasture, and possibly to eradicate disease-prone habitats, may have been facilitated by prolonged periods of moisture deficits that might also have facilitated the spread of food production technologies. Vegetation changes c. 700 BP are associated with evidence for the occurrence of fires locally and could represent the activities of people and their animals close to the study site. [ABSTRACT FROM AUTHOR]

Ice cores from the relatively low-lying ice caps in Svalbard have not been widely exploited in climatic studies owing to uncertainties about the effect of meltwater percolation. However, results from two new Svalbard ice cores, at Lomonosovfonna and Austfonna, have shown that with careful site selection, high-resolution sampling and multiple chemical analyses it is possible to recover ice cores from which part of the annual signals are preserved, despite the considerable meltwater percolation. The new Svalbard ice cores are positioned in different parts of Svalbard and cover the past 800 years. In this paper we focus on the last 400 years. The δ18O signals from the cores are qualitatively similar over most of the twentieth century, suggesting that they record the same atmospheric signal. Prior to AD 1920, the Austfonna ice core exhibits more negative δ18O values than Lomonosovfonna, although there are intermittent decadal-scale periods throughout the record with similar values. We suggest that the differences reflect the effect of the inversion layer during the winter. The pattern in the δ18O records is similar to the Longyearbyen air-temperature record, but on an annual level the correlation is low. The Austfonna record correlates well with the temperature record from the more distant and southwesterly located Jan Mayen. A comparison of the ice-core and sea-ice records from this period suggests that sea-ice extent and Austfonna δ18O are related over the past 400 years. This may reflect the position of the storm tracks and their direct influence on the relatively low-altitude Austfonna. Lomonosovfonna may be less sensitive to such changes and primarily record free atmospheric changes instead of variations in sea-ice extent, the latter is probably a result of its higher elevation. [ABSTRACT FROM AUTHOR]

In the sedimentary record of the permanently anoxic Drammensfjord, a suite of lipid biomarkers that are derived from the alga Botryococcus braunii (Kützing), botryococcenes, is present in varying amounts, but absent in sediments deposited after AD 1850. The disappearance is concurrent with the industrialization of sawmills and the introduction of paper and pulp mills along the river Drammen and upstream water bodies, and the related increase of anthropogenic eutrophication. Because of the sensitivity of this alga for environmental change, a direct correlation between these two events is inferred. This implies that the disappearance of the botryococcenes can serve as a palaeoenvironmental indicator for early eutrophication or environmental change in general. This may be a useful tool in the ongoing research to unravel the response of natural systems to climatic, geophysical or anthropogenic changes. [ABSTRACT FROM AUTHOR]

The focus of this paper is on the reconstruction of the mid-Holocene climatic changes based on the pollen records contained in a 6.2 m thick section in the southern part of the Tengger Desert, northwestern China. To understand the modern analogues of the mid-Holocene changes, modern pollen spectra across different vegetation zones from the Qilian Mountains to the lowland Tengger Desert were studied first. Four pollen combinations were identified, corresponding to four different modern ecological environments: (1) a Picea-Artemisia combination in a spruce forest and its vicinity; (2) an Artemisia-Chenopodiaceae-Gramineae-Salix combination in a mixture belt of montane grassland and poplar woodland; (3) a Chenopodiaceae-Artemisia-Nitraria combination in a desert steppe belt; and (4) an Elaeagnus-Artemisia-Chenopodiaceae-Nitraria combination in a desert riparian forest. Our study also shows that a relatively low percentage of Picea pollen (30–10%) seems to be associated with water transportation (alluvial deposits) and a very low percentage of Picea pollen (10–5%) appears to be related to long-distance air transportation. With references to the modern relationships between pollen assemblages and associated bioclimates, the pollen sequence covering the period between 8500 and 3000 cal. BP was used to infer the climatic change history. The results show that a warmer and drier climate dominated between 8500 and 7950 cal. BP. Subsequent decreases in Artemisia and warm desert forbs/shrubs taxa and contemporaneous fluctuating increases in montane coniferous and aquatics elements from 7950 to 7400 cal. BP reflect a fluctuating increase in humidity and/or a fluctuating decrease in temperature. The following period from 7400 to 5650 cal. BP was generally warm with the Holocene Climate Optimum occurring between 7400 and 6500 cal. BP. A remarkably cool spell followed between 6500 and 6300 cal. BP that was then succeeded by a warmer and more humid period between 6300 and 5650 cal. BP. The period between 5650 and 4450 cal. BP was characterized by drastic oscillations in climatic conditions with three humid and probably cold spells intervened by three relatively dry and warm spells. The period between 4450 and 3500 cal. BP was cold and humid, followed by a wet spell as indicated by a very high percentage of Typha pollen. [ABSTRACT FROM AUTHOR]

In this paper we use a simulation approach to explore the effect of variation in taxon parameters and landscape patterning on relevant source area of pollen. We use the Prentice-Sugita model, assume constant atmospheric conditions and basin morphology, and take a reductionist approach to explore the behaviour of pollen dispersal and deposition in a simple landscape scenario. Individual factors within the scenario (pollen fall speed, relative pollen productivity, size of basic unit in the landscape mosaic, patch size, rarity of individual taxa and overall number of taxa present in the landscape) are varied while all other parameters are kept constant, thus permitting exploration of the role of different components of the system. These simulations suggest that, for basins of given size under fixed atmospheric conditions, the relevant source area of pollen is primarily an expression of the patterning of the different vegetation elements within the landscape. This has important implications for the interpretation of palaeoecological records and reconstruction of past environments. Reconstruction, especially quantitative reconstruction, requires some estimate of past relevant source area of pollen. If, as our results suggest, vegetation patterning is an important determinant of this, then it must also be taken into account when attempting to reconstruct past vegetation communities. [ABSTRACT FROM AUTHOR]

The result of long-term environmental and human interaction is a variety of potential human responses to major natural crises: population aggregation or dispersal, changes in economic strategies and landuse patterns, restructuring of social organization, increase in the incidence of conflict and warfare, and, in some instances, urban abandonment and cultural collapse. In the context of pre-industrial societies, two social processes with the greatest potential impact on the environment and on changing human-environmental interaction are urbanization and the development of diversified, regional-scale production systems such as intensive agriculture, pastoralism and exploitation of maritime resources. This paper employs archaeological and geological data from the Jequetepeque and Zana valleys on the north coast desert of Peru to study: (1) the specific responses of Moche, Chimu and Inca societies (c. AD 250-1553) to major episodes of drought, El Nin~o flooding, and desertification; (2) the social processes of urban-rural relations and economic diversification; and (3) how these processes interacted within the dynamic arid north coast. Our research focuses on changing palaeoenvironmental regimes, agricultural infrastructures and domestic occupations to explore the complex interplay of cultural and natural forces that shaped the variable human responses and the history of urban-rural systems. Understanding the problem of how pre-industrial systems were sustained or failed in the context of interrelated social and environmental crises is an interdisciplinary objective, one that requires the integration of analytical techniques and theoretical frameworks of both the natural and social sciences as delineated in this study. [ABSTRACT FROM AUTHOR]