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The Southern Hemisphere Westerlies (SHW) play a major role in the global climate system. The winds drive ocean circulation and affect the Southern Oceans’ ability to take up atmospheric CO2. Recently, the SHW core belt has strengthened and shifted south, but there is an insufficient understanding of its long-term behaviour. Palaeoclimatic records are key for capturing long-term variability through the SHW’s effect on surface temperature and moisture availability. However, terrestrial records are sparse in the Southern Hemisphere. We use a palynological record from Lake Diamond on sub-Antarctic South Georgia to provide reconstructions of vegetation and climate for the last ~10,000 years. Influx of long-distance transported pollen is used as a measure of surface wind strength. Changes in relative pollen abundance of native taxa occupying either upland (cold) or lowland (warm) environments indicate local climatic variability. On South Georgia, we find long-distance transported pollen from South American taxa, mainly Nothofagus and Ephedra. They show a general increase in abundance throughout the Holocene, with peak influxes between 5700–5400, 2800–1500 and 1000–500 cal yr BP. These intervals coincide with colder periods inferred from the palynological record, suggesting that SHW variation and temperature on South Georgia are highly connected. Agreement with palaeoecological records from eastern Patagonia show that climatic changes have been regionally consistent. The record from Lake Diamond further illustrates the importance of remote islands in contributing to a deeper understanding of atmospheric circulation and climatic variability in the sub-Antarctic.

As science, technology, engineering, and mathematics (STEM) classrooms in higher education transition from lecturing to active learning, the frequency of student interactions in class increases. Previous research documents a gender bias in participation, with women participating less than would be expected on the basis of their numeric proportions. In the present study, we asked which attributes of the learning environment contribute to decreased female participation: the abundance of in-class interactions, the diversity of interactions, the proportion of women in class, the instructor's gender, the class size, and whether the course targeted lower division (first and second year) or upper division (third or fourth year) students. We calculated likelihood ratios of female participation from over 5300 student–instructor interactions observed across multiple institutions. We falsified several alternative hypotheses and demonstrate that increasing class size has the largest negative effect. We also found that when the instructors used a diverse range of teaching strategies, the women were more likely to participate after small-group discussions.

The Southern Hemisphere Westerly Winds play a major role in the global climate system. By driving circulation in the Southern Ocean and its subsequent effect on the upwelling of carbon-rich deep water, the Westerlies affect the oceans ability to take up atmospheric CO2. Furthermore, by impacting temperature conditions and moisture availability, the Westerlies act as a first-order control on local environmental conditions. Uncovering long term natural climatic variability in the sub-Antarctic is therefore crucial to understand how the global system might react under future climate changes. Due to the lack of land mass on the Southern Hemisphere, sub-Antarctic islands are essential for studying climate variability in this region; terrestrial records provide valuable insights into both local and regional surface climate conditions. We use a pollen record from Lake Diamond to provide detailed reconstructions of vegetation and climate on sub-Antarctic South Georgia for the last ~9900 years. Westerly Wind strength and position is inferred from long-distance transport of pollen from South America, Africa, and New Zealand. Additionally, changes in relative pollen abundance of native taxa occupying either upland (cold) or lowland (warm) environments are used to infer local climatic variation, supported by additional sedimentological proxies. On South Georgia we find long-distance transported pollen from several South American taxa, mainly Nothofagus, Ephedra and Asteraceae. They show a general increase in abundance throughout the Holocene, with peak influx between 2800 and 1500 cal yr BP, most likely caused by changes in the strength of the Southern Hemisphere Westerly Winds. In both our record and others, this interval is seen as the end of the Neoglacial period.

A detailed, well-dated record of pollen and sedimentary ancient DNA (sedaDNA) for the period 15 000–9500 cal a bp describes changes at Lake Bolshoye Shchuchye in the Polar Ural Mountains, located far east of the classical Lateglacial sites in western Europe. Arctic tundra rapidly changed to lusher vegetation, possibly including both dwarf (Betula nana) and tree birch (B. pubescens), dated in our record to take place 14 565 cal a bp, coincident with the onset of the Bølling in western Europe; this was paralleled by increased summer temperatures. A striking feature is an early decline in Betula pollen and sedaDNA reads 300 years before the onset of the Younger Dryas (YD) in western Europe. Given the solid site chronology, this could indicate that the YD cooling started in Siberia and propagated westwards, or that the vegetation reacted to the inter-Allerød cooling at 13 100 cal a bp and did not recover during the late Allerød. During the YD, increases in steppe taxa such as Artemisia and Chenopodiaceae suggest drier conditions. At the onset of the Holocene, the vegetation around the lake reacted fast to the warmer conditions, as seen in the increase of arboreal taxa, especially Betula, and a decrease in herbs such as Artemisia and Cyperaceae. publishedVersion

A 24,000-year record of plant community dynamics, based on pollen and ancient DNA from the sediments (sedaDNA) of Lake Bolshoye Shchuchye in the Polar Ural Mountains, provides detailed information on the flora of the Last Glacial Maximum (LGM) and also changes in plant community composition and dominance. It greatly improves on incomplete records from short and fragmented stratigraphic sequences found in exposed sedimentary sections in the western Russian Arctic. In total, 162 plant taxa were detected by sedaDNA and 115 by pollen analysis. Several shifts in dominance between and within plant functional groups occurred over the studied period, but most taxa appear to have survived in situ. A diverse arctic-alpine herb flora characterised the interval ca. 24,000–17,000 cal years BP and persisted into the Holocene. Around 17,000 cal years BP, sedges (e.g. Carex) and bryophytes (e.g. Bryum, Aulacomnium) increased. The establishment of shrub-tundra communities of Dryas and Vaccinium sp., with potentially some Betula pubescens trees (influx ∼290 grains cm2 year−1), followed at ca. 15,000 cal years BP. Forest taxa such as Picea and ferns (e.g. Dryopteris fragrans, Gymnocarpium dryopteris) established near the lake from ca. 10,000 cal years BP, followed by the establishment of Larix trees from ca. 9000 cal years BP. Picea began to decline from ca. 7000 cal years BP. A complete withdrawal of forest tree taxa occurred by ca. 4000 cal years BP, presumably due to decreasing growing-season temperatures, allowing the expansion of dwarf-shrub tundra and a diverse herb community similar to the present-day vegetation mosaic. Contrary to some earlier comparative studies, sedaDNA and pollen from Lake Bolshoye Shchuchye showed high similarity in the timing of compositional changes and the occurrence of key plant taxa. The sedaDNA record revealed several features that the pollen stratigraphy and earlier palaeorecords in the region failed to detect; a sustained, long-term increase in floristic richness since the LGM until the early Holocene, turnover in grass and forb genera over the Pleistocene-Holocene transition, persistence of a diverse arctic-alpine flora over the late Quaternary, and a variable bryophyte flora through time. As pollen records are often limited by taxonomic resolution, differential productivity and dispersal, sedaDNA can provide improved estimates of floristic richness and is better able to distinguish between different plant assemblages. However, pollen remains superior at providing quantitative estimates of plant abundance changes and detecting several diverse groups (e.g. Poaceae, Cyperaceae, Asteraceae) which may be underreported in the sedaDNA. Joint use of the two proxies provided unprecedented floristic detail of past plant communities and helped to distinguish between long-distance transport of pollen and local presence, particularly for woody plant taxa.

Practical teaching can give authentic learning experiences and teach valuable skills for undergraduate students in the STEM disciplines. One of the main ways of giving students such experiences, laboratory teaching, is met with many challenges such as budget cuts, increased use of virtual learning, and currently the university lockdowns due to the COVID‐19 pandemic. We highlight how at‐home do‐it‐yourself (DIY) experiments can be a good way to include physical interaction with your study organism, system, or technique to give the students a practical, authentic learning experience. We hope that by outlining the benefits of a practical, at‐home, DIY experiment we can inspire more people to design these teaching activities in the current remote teaching situation and beyond. By contributing two examples in the field of plant biology we enrich the database on experiments to draw inspiration from for these teaching methods., Practical teaching is met with many challenges, like budget cuts, moving to virtual teaching, and the lockdowns of the COVID pandemic. We highlight at‐home do‐it‐yourself experiments as a good option for maintaining hands‐on, student active, inquiry‐based teaching options when we teach off‐campus. We present two examples of such experiments from an undergraduate biology education in Norway.

Early agriculture can be detected in palaeovegetation records, but quantification of the relative importance of climate and land use in influencing regional vegetation composition since the onset of agriculture is a topic that is rarely addressed. We present a novel approach that combines pollen-based REVEALS estimates of plant cover with climate, anthropogenic land-cover and dynamic vegetation modelling results. This is used to quantify the relative impacts of land use and climate on Holocene vegetation at a sub-continental scale, i.e. northern and western Europe north of the Alps. We use redundancy analysis and variation partitioning to quantify the percentage of variation in vegetation composition explained by the climate and land-use variables, and Monte Carlo permutation tests to assess the statistical significance of each variable. We further use a similarity index to combine pollen based REVEALS estimates with climate-driven dynamic vegetation modelling results. The overall results indicate that climate is the major driver of vegetation when the Holocene is considered as a whole and at the sub-continental scale, although land use is important regionally. Four critical phases of land-use effects on vegetation are identified. The first phase (from 7000 to 6500 BP) corresponds to the early impacts on vegetation of farming and Neolithic forest clearance and to the dominance of climate as a driver of vegetation change. During the second phase (from 4500 to 4000 BP), land use becomes a major control of vegetation. Climate is still the principal driver, although its influence decreases gradually. The third phase (from 2000 to 1500 BP) is characterised by the continued role of climate on vegetation as a consequence of late-Holocene climate shifts and specific climate events that influence vegetation as well as land use. The last phase (from 500 to 350 BP) shows an acceleration of vegetation changes, in particular during the last century, caused by new farming practices and forestry in response to population growth and industrialization. This is a unique signature of anthropogenic impact within the Holocene but European vegetation remains climatically sensitive and thus may continue to respond to ongoing climate change. (C) 2017 Elsevier Ltd. All rights reserved.

Current interest and debate on pollen-assemblage richness as a proxy for past plant richness have prompted us to review recent developments in assessing whether modern pollen-assemblage richness reflects contemporary floristic richness. We present basic definitions and outline key terminology. We summarise four basic needs in assessing pollen–plant richness relationships — modern pollen data, modern vegetation data, pollen–plant translation tables, and quantification of the co-variation between modern pollen and vegetation compositional data. We discuss three key estimates and one numerical tool — richness estimation, evenness estimation, diversity estimation, and statistical modelling. We consider the inherent problems and biases in assessing pollen–plant richness relationships — taxonomic precision, pollen-sample:pollen-population ratios, pollen-representation bias, and underlying concepts of evenness and diversity. We summarise alternative approaches to studying pollen–plant richness relationships. We show that almost all studies which have compared modern pollen richness with contemporary site-specific plant richness reveal good relationships between palynological richness and plant richness. We outline future challenges and research opportunities — interpreting past pollen-richness patterns, estimating richness from macrofossils, studying pollen richness at different scales, partitioning diversity and estimating beta diversity, estimating false, hidden, and dark richness, and considering past functional and phylogenetic diversity from pollen data. We conclude with an assessment of the current state-of-knowledge about whether pollen richness reflects floristic richness and explore what is known and unknown in our understanding of pollen–plant richness relationships. acceptedVersion

The relationships between modern pollen and floristic plant richness, diversity and evenness are assessed using pollen assemblages and associated vegetation data from 52 lakes along an elevational and vegetational gradient in the Setesdal valley of south-central Norway. Various data transformations were applied to minimise bias in the vegetation and pollen datasets. Plant species were transformed to their pollen or spore equivalents to reduce taxonomic biases. Pollen counts were transformed using Andersen’s general pollen-representation values for northern European trees and shrubs and the Regional Estimates of Vegetation Abundance from Large Sites (REVEALS) model with pollen-productivity estimates (PPEs) appropriate for Setesdal to minimise pollen-representation bias. Pollen count-size bias (before or after transformation) was eliminated by rarefaction analysis based on bootstrap resampling. Richness and diversity were quantified using Hill numbers ( N0, N1, N2), and evenness was estimated as the ratios of N0, N1 and N2. Diversity partitioning was used to estimate β diversity. The strongest correlations between pollen and plant richness and diversity are with pollen counts transformed using Andersen’s representation values and rarefied to a common count size and with plants transformed to their pollen equivalents. However, if sites from the low-alpine zone are excluded where there are high values of far-transported tree pollen, the richness and diversity relationships are also statistically significant for untransformed pollen data and plants transformed into their pollen equivalents. The effects of data transformation on diversity partitioning and estimates of β diversity are explored. We demonstrate that there are statistically significant positive relationships between pollen and plant richness and diversity along the entire elevational gradient after transforming the datasets to minimise biases due to taxonomic differences, differential pollen representation, and pollen-count size, and similar significant positive relationships along the forested parts of the gradient (nemoral, boreonemoral, southern boreal, middle boreal) after transforming the datasets to minimise biases due to taxonomic differences and pollen-count size.

Knowledge of the relationship between vegetation and modern pollen deposition is necessary to improve the interpretation of fossil pollen samples. We compared the cover of plant species and the modern pollen deposition in surface moss samples in 49 plots in rich-fen vegetation from the boreal vegetation zone in Norway in two areas (one oceanic and one more continental). These rich fens were used for traditional hay cutting until ca. 1950. Three management regimes are used: 1) biennial mowing, 2) quadrennial mowing and 3) unmown. The unmown areas were traditional hay fens, with no management since the 1950s. Of the 89 plant taxa and corresponding 65 taxa of pollen and spores, 29 and 22, respectively, were sufficiently represented in both vegetation and as pollen, to allow direct comparisons of the two data sets. Most of the plant and pollen taxa were found in the plots from both study areas and in plots with different mowing frequencies. Therefore, quantitative differences in vegetation cover and pollen percentages were the main focus in this investigation of plant–pollen relationships in mown and unmown vegetation. The relative difference in plant cover was largest between biennially and unmown plots. 12 species showed a significant positive correlation with difference in plant cover between mown and unmown areas (p < 0.05; Wilcoxon signed rank test), most pronounced for Molinia caerulea (most common in unmown plots), and Carex dioica and Thalictrum alpinum (most common in mown plots). A significant positive plant–pollen correlation (Spearman rank-correlation) was found for 10 pollen taxa. Thalictrum alpinum is a very good pollen indicator, and Cyperaceae, Eriophorum-type and Pedicularis-type are good pollen indicators of mowing. Poaceae/M. caerulea and Succisa pratensis are negatively correlated with mowing. The impact of mowing on species composition was similar in both study areas. Mown and unmown areas were differentiated in the vegetation data and could be identified by modern pollen data. These results will improve the interpretation of past land-use practices using pollen analysis of rich-fen vegetation. acceptedVersion

Palaeoecology and ecology have a lot in common. However, the two disciplines have evolved almost separately, leading to an ongoing debate on how to link them better, as both would undoubtedly benefit from a higher degree of cross-fertilisation of ideas, research insights and questions. In this paper, we explore similarities and differences in the two branches of ecology over the past 40 years by assessing the publication output from an unusually large cohort of ‘academic siblings’ – researchers in ecology and palaeoecology who all share one of the strongest career-shaping influences on researchers; their supervisor. This was made possible by John Birks’ long and active career within ecology and palaeoecology, and his supervision of a large number of students in both fields ( n = 12 and 21, respectively). Among them, John Birks’ academic progeny has published 934 papers in the international peer-reviewed literature. We collected information on the year, titles, keywords and journals of all these publications and used these data to assess the extent of, and find potential explanations for, the historical and present-day separation of ecology and palaeoecology. Despite considerable thematic overlap, there is a real and possibly widening division between the two branches that is visible both at the scale of individual research careers, journals and papers. We argue that rather than being unique to the relationship between palaeoecology and ecology, this reflects trends for thematic and methodological specialisation evident across the research landscape. We propose that both individual researchers and journals would benefit from, and can contribute to, closing the gaps developing between various ‘special branches’ in science. A good title, an informative abstract, a careful and thought-through selection of keywords and a focus on readability and avoidance of jargon will likely improve readership and impact both within one’s own ‘special branch’ and beyond.

In recent decades there has been a major development of numerical and statistical methods with considerable potential for the handling, analysis, and summarisation of complex multivariate pollen data. We compare ‘traditional’ ordination and hierarchical clustering methods with recently-developed methods such as principal curves, non-hierarchical agglomerative clustering, multivariate classification trees, and random forests by investigating modern pollen–vegetation relationships using the well-known surface pollen data-set of Lichti–Federovich and Ritchie (1968) from the Western Interior of Canada. Our results show that the modern pollen data display well the major vegetation–landform types from which the surface samples were collected independent of which numerical method is used. Ordination methods partly capture the geographical position of the lakes from which the samples were collected. Different ordination methods produce similar results. Principal curves are not superior to the results from conventional ordination methods. Ward's hierarchical clustering method performs as well as other agglomerative clustering techniques. Multivariate classification trees and random forests produce similar results, but the latter has smaller prediction errors. In general, the novel methods do not provide any new insights into the data, nor do they have any impact on previous conclusions. However, these novel methods have several advantages over traditional techniques because they make fewer assumptions about the underlying character or structure of the data, and they include effective ways of displaying the quantitative importance of different variables. As it is not possible to recommend one method over another, our conclusion is that there is now a large number of robust numerical methods that can be used to detect the underlying patterns within modern pollen assemblages.

Reconstructing and interpreting past vegetation composition can be enhanced by studying modern pollen samples and contemporary vegetation. Here, we compare pollen in surface sediments from 52 medium-sized lakes with the surrounding vegetation along an elevational gradient covering six major vegetation zones in south-central Norway. The aims are to detect how well the vegetational composition and terrestrial pollen assemblages distinguish the major vegetation zones, whether the pollen composition in surface-sediment samples reflects the composition of the surrounding vegetation and whether aquatic pollen and spores reflect the major vegetation zones. We use multivariate classification trees, ordination and co-correspondence analysis to address these questions. We show that it is possible to separate the major zones using terrestrial pollen assemblages and using plant species in the vegetation reasonably well, whereas aquatic pollen and spores poorly reflect the zones. Surprisingly, the terrestrial pollen assemblages separate the zones better than vegetational composition does. The compositional match between the pollen assemblages and surrounding vegetation is consistent for sites along the elevational gradient within the forested zones, but deteriorates in increasingly open vegetation zones. Our results are consistent with other investigations of modern pollen–vegetation relationships. Careful interpretation of past vegetation from pollen assemblages is needed when the vegetation is treeless because of a larger potential pollen-source area and hence a higher proportion of long-distance dispersed pollen in open areas.

We reconstruct mean July temperature (Tjul) from three sites on the island of Andoya, northern Norway for the period 15 000–9000 cal yr BP using three biotic proxies. A probabilistic indicator species approach (pdf method) was used for plant macrofossil data from all sites (M-Tjul). Reconstructions based on pollen (P-Tjul) (2 sites) and chironomids C-Tjul) (1 site) were done using weighted averaging and weighted-averaging partial least-squares, respectively. A sediment proxy for catchment glacier development was measured at the main site, Lusvatnet. The July temperature reconstructions from all the sites show a similar development through the deglaciation. An initial July temperature of 4 °C increased to a maximum of 7–8 °C during the Allerod at c.13 200 cal yr BP. There was no marked cooling at the start of the Younger Dryas (YD) chronozone, at Lusvatnet, C-Tjul decreased after 12 700 cal yr BP to a low of 6 °C at about 12 550 cal yr BP before increasing markedly around 12 400 cal yr BP. Conversely, P-Tjul rose slowly through the early YD. Both proxies exceeded the Allerod temperatures for around 300 years before decreasing towards a minimum of 6 °C at c. 12 000 cal yr BP. M-Tjul maintained a mean of c. 8 °C throughout the YD. Different sensitivities of proxies are discussed. Their different responses during the YD at the three sites, along with the glacial evidence, highlight the role of aridity. At c. 11 500 cal yr BP, July temperatures increased rapidly over Andoya to about 10 °C, and then rose gradually to maximum values of 12 °C at c. 9700 cal yr BP. The temperature reconstructions are consistent with the flow of Atlantic water into the Nordic Seas except during the YD, when variability in sea ice may have been more important. During the early Holocene there are some differences between sites, resulting from local site factors such as altitude and exposure, soil development, and catchment instability.

The modern pollen production of local sub-alpine and alpine vegetation has been monitored over 8 years by using pollen traps situated along an elevational transect crossing the Pinus sylvestris and Betula pubescens elevational limits and continuing into the mid- and high-alpine vegetation in western Norway. The aim of the study is to monitor annual variation in the pollen production and hence the representation of common taxa found at or near the tree-line. The results can be used to derive critical pollen values that can be used to infer the presence of these taxa in the past, and to reconstruct past changes in tree line positions. Nine modified Tauber pollen traps were critically positioned in the vegetation from 663 to 1,347 m a.s.l. Three sub-aquatic traps were located in a small lake at 800 m a.s.l. just above the present-day B. pubescens tree-line. The traps have been sampled from 2004 to 2012. The results display large variations in pollen percentages and pollen accumulation rates from year to year, as well as great differences between the traps placed in the vegetation and in the lake, suggesting that further pollen trapping is needed to get a solid long-term average. The vegetation traps follow the vegetation distribution better and, as expected, give a more local signal than the lake traps.

Sedimentary pollen offers excellent opportunities to reconstruct vegetation changes over past millennia. Number of different pollen taxa or pollen richness is used to characterise past plant richness. To improve the interpretation of sedimentary pollen richness, it is essential to understand the relationship between pollen and plant richness in contemporary landscapes. This study presents a regional-scale comparison of pollen and plant richness from northern Europe and evaluates the importance of environmental variables on pollen and plant richness. We use a pollen dataset of 511 lake-surface pollen samples ranging through temperate, boreal and tundra biomes. To characterise plant diversity, we use a dataset formulated from the two largest plant atlases available in Europe. We compare pollen and plant richness estimates in different groups of taxa (wind-pollinated vs. non-wind-pollinated, trees and shrubs vs. herbs and grasses) and test their relationships with climate and landscape variables. Pollen richness is significantly positively correlated with plant richness (r = 0.53). The pollen plant richness correlation improves (r = 0.63) when high pollen producers are downweighted prior to estimating richness minimising the influence of pollen production on the pollen richness estimate. This suggests that methods accommodating pollen-production differences in richness estimates deserve further attention and should become more widely used in Quaternary pollen diversity studies. The highest correlations are found between pollen and plant richness of trees and shrubs (r = 0.83) and of wind-pollinated taxa (r = 0.75) suggesting that these are the best measures of broad-scale plant richness over several thousands of square kilometres. Mean annual temperature is the strongest predictor of both pollen and plant richness. Landscape openness is positively associated with pollen richness but not with plant richness. Pollen richness values from extremely open and/or cold areas where pollen production is low should be interpreted with caution because low local pollen production increases the proportion of extra-regional pollen. Synthesis. Our results confirm that pollen data can provide insights into past plant richness changes in northern Europe, and with careful consideration of pollen-production differences and spatial scale represented, pollen data make it possible to investigate vegetation diversity trends over long time-scales and under changing climatic and habitat conditions.

Forest fires convert a proportion of the burning vegetation into charcoal that is stored in forest soils and lake sediments. In this paper we use a geostatistical approach to present a detailed analysis of the size of the charcoal pool and its spatial variation in a boreal forest watershed including its lake sediment. The amount of soil charcoal averaged 179 g/m2 and ranged from 0 to 3600 g/m2 in the watershed. There was an extreme variation in the size of the charcoal pool over fine (cm) spatial scales. For example, the amount of charcoal in the soil could range from 34 to 1646 g/m2 within a distance of 10 cm. Individually dated soil charcoal particles had radiocarbon ages that varied from 630 to 2930 cal yr BP. The lake sediment began accumulating at 10,600 cal yr BP and charcoal accumulation has been practically continuous ever since then, with the largest peak occurring at 6900 cal yr BP. The lake sediment contained more charcoal, 360 g/m2, than the average for forest soil. We interpret this as an indication of a relatively rapid degradation of charcoal in boreal forest soils.

The origin and developmental history of Fagus sylvatica forests in south-eastern Norway have been studied through pollen analysis and AMS radiocarbon-dating of peat from two small forest hollows. In this area F. sylvatica appears to have a long history, from the first occurrence of F. sylvatica pollen at ca. 9100 cal. b.p. to its local expansion ca. 1300–1200 cal. b.p. At this time a shift from a diverse landscape mosaic with many plant taxa present, including broad-leaved trees, to a less diverse landscape mosaic with Picea abies and F. sylvatica trees is interpreted from the pollen data. The long history of F. sylvatica suggests that the existing forests are not recent plantations, but implies that these forests are native. The presence of pollen indicative of anthropogenic activity combined with charcoal before the expansion of F. sylvatica, as well as comparison with data from nearby sites, suggest that the forest development was likely to be a result of human activity and climatic changes, particularly changes in moisture conditions.

We present a new pollen–climate calibration data-set from northern Europe consisting of 583 modern pollen samples and high-resolution, GIS-based modern climate data. The pollen data are characterised by high taxonomic resolution (167 taxa) and homogenous taphonomy (all samples are from small-to-medium-sized lakes). To assess the potential of this calibration set for the reconstruction of different climatic parameters, we use novel regression tree methods to analyse the effect on pollen composition and variability of four parameters: summer temperature, winter temperature, water balance, and continentality index. We use multivariate regression trees to analyse the variation in pollen assemblages in modern climate space, while boosted regression trees are used to analyse the relative influence of different climatic parameters on each taxon. We find taxon responses to be relatively individualistic. While most taxa (65%) are most responsive to summer temperature, other parameters are either primary determinants or significant secondary determinants for many taxa. At the assemblage level, significant variation is found in assemblages from similar summer temperature regimes, with distinct clusters of assemblages also identified along the continentality gradient. As a multivariate method, we consider boosted regression trees highly effective in describing and modelling modern climate–taxon relationships.

A new palaeoclimatic reconstruction of mid-summer (July) temperatures for the last 7.5 ka in northern Fennoscandia is presented. It is based on two botanical proxies: spectra of fossil pollen and tree rings of Scots pine logs recovered from lacustrine sediments in the Arctic tree-line region. A newly developed method of proxy fusion is used to integrate the proxy-specific reconstructions of past summer temperature variability based on the pollen-stratigraphic and dendroclimatic data. The rationale behind the method is that the two proxies are likely to be connected to climate variability in a timescale-dependent fashion and, accordingly, the new reconstruction makes use of the low- and high-frequencies from pollen-stratigraphic and tree-ring data, respectively. The most prominent features of the new reconstruction are: (1) the long-term decline of temperatures by 2.0 °C over the past 7.5 ka, (2) the mid-Holocene warmth culminating between 5 and 4 ka as a deviation from the cooling trend, (3) the Little Ice Age cool phase between 0.7 and 0.1 ka, and (4) the subsequent warming during the past century. These periods are superimposed on year-to-year variations in climate as dated to calendar-year accuracy by dendrochronology. Within the modern period, the years 1934 and 1937 are among the warmest, and the years 1903 and 1910 are among the coldest summers in the context of the past 7.5 ka. On average, the reconstructed Holocene climate was approximately 0.85 °C warmer than the twentieth century.

Kruger, L. C., Paus, A., Svendsen, J. I. & Bjune, A. E. 2011: Lateglacial vegetation and palaeoenvironment in W Norway, with new pollen data from the Sunnmore region. Boreas, 10.1111/j.1502-3885.2011.00213.x. ISSN 0300-9483. Two sediment sequences from Sunnmore, northern W Norway, were pollen-analytically studied to reconstruct the Lateglacial vegetation history and climate. The coastal Dimnamyra was deglaciated around 15.3 ka BP, whereas Lokjingsmyra, further inland, became ice-free around 14 ka BP. The pioneer vegetation dominated by snow-bed communities was gradually replaced by grassland and sparse heath vegetation. A pronounced peak in Poaceae around 12.9 ka BP may reflect warmer and/or drier conditions. The Younger Dryas (YD) cooling phase shows increasing snow-bed vegetation and the local establishment of Artemisia norvegica. A subsequent vegetation closure from grassland to heath signals the Holocene warming. Birch forests were established 500–600 years after the YD–Holocene transition. This development follows the pattern of the Sunnmore region, which is clearly different from the Empetrum dominance in the Lateglacial interstadial further south in W Norway. The Lateglacial oscillations GI-1d (Older Dryas) and GI-1b (Gerzensee) are hardly traceable in the north, in contrast to southern W Norway. The southern vegetation was probably closer to an ecotone and more susceptible to climate changes.

Climate change and variability assessments require an understanding of their long-term and period (low-frequency) and short-term and period (high-frequency) variations. Pollen data have conventionally been thought of as a proxy of low-frequency variation of past climates but of more limited applicability for studying high frequencies. Likewise, tree-rings are commonly supposed to reflect faithfully high-frequency variations, with additional uncertainties attributable to variations at lower frequencies. Here we challenge this view in the context of pollen and tree-ring based temperature reconstructions from high-latitude Europe. The two types of records are compared and it is shown that the pollen and tree-ring based reconstructions exhibit similar temperature variability on centennial and longer scales. These can be revealed using timescale-dependent filtering. The same method surmounts geochronological discrepancies, thus enabling reconciliation of the proxies. Resulting new reconstructions validate over the instrumental period. Over longer intervals, our new proxy-fusions cover the climatic reversals of the Medieval Climate Anomaly (during the 10th to 13th centuries), Little Ice Age (during the 14th to 19th centuries), and 20th century warming. The warmest spells occurred in association with the Medieval Climate Anomaly and during the 20th century. The coolest intervals occurred in relation to Little Ice Age conditions. The new reconstructions show that decadal temperature amplitude has been approximately 2.5 °C in the past and thus considerably larger than inferred from spatially large-scale estimates of temperature anomalies.

In the DOORMAT (Direct Observation of Recent Macrofossils Across Treeline) project, the modern representation of local vegetation by pollen and plant remains (plant macrofossils) across a west Norwegian tree line, composed of Betula pubescens and Pinus sylvestris, has been studied over 2 years. The aim was to discover if the modern tree line could be detected and therefore how precisely past tree-line movements could be reconstructed and related to Holocene climate changes by using one proxy or a combination of both. Traps were placed in the vegetation from 663 to 1,120 m a.s.l., spanning the pine altitudinal species limit, the birch tree-line ecotone, and the vegetation zones up to the mid-alpine zone. Three traps were also set in the small lake Trettetjorn close to the modern tree line at 800 m a.s.l. Traps were emptied twice a year to sample both summer and winter seasons. Macrofossils represent their local vegetation well. However, tree Betula remains were trapped above the tree line and Pinus and Picea remains were recorded 1.0–1.5 km away from their sources, demonstrating considerable dispersal capacity. This shows that rare macrofossil remains do not necessarily represent the local presence of these trees. Aerial tree pollen deposition in traps at the upper limit of pine woodland and in the subalpine birch woodland was unexpectedly low, whereas pollen accumulation rates (PAR) were orders of magnitude higher in the lake traps. We hypothesise that the lake receives regional pollen rain washed in from its catchment by snow meltwater and that high values in traps are due to continuous suspension of pollen in the lake water during summer. The interpretation of tree-line changes from existing Holocene pollen and plant macrofossil data from Trettetjorn was supported and refined by the DOORMAT macrofossil data, but the modern pollen data were anomalous.

Seppa,H.,Birks,H.J.B.,Bjune,A.E.N Birks & Seppa 2010 this issue).¨A second important factor is the glaciation history.Practically the whole Fennoscandian–Baltic region wascoveredbytheScandinavianIceSheetover10000yearsago, and the various geomorphological and geologicalindications of glaciations are easily observable all overthe region. They drew the attention of early geologistsand laymen alike, perhaps explaining why the ice agetheory was quickly adopted in the Nordic countriesafter it was first established in the Alps by Jean deCharpentier and Louis Agassiz in the 1830s (Imbrie &Palmer Imbrie 1979). The recognition of the history ofglaciation served to provide an important chron-ological framework, as it became clear that the palaeo-climatic records obtained from sedimentary deposits

Bjune, A. E., Birks, H. J. B., Peglar, S. M. & Odland, A. 2010: Developing a modern pollen–climate calibration data set for Norway. Boreas, Vol. 39, pp. 674–688. 10.1111/j.1502-3885.2010.00158.x. ISSN 0300-9483. Modern pollen–climate data sets consisting of modern pollen assemblages and modern climate data (mean July temperature and mean annual precipitation) have been developed for Norway based on 191 lakes and 321 lakes. The original 191-lake data set was designed to optimize the distribution of the lakes sampled along the mean July temperature gradient, thereby fulfilling one of the most critical assumptions of weighted-averaging regression and calibration and its relative, weighted-averaging partial least-squares regression. A further 130 surface samples of comparable taphonomy, taxonomic detail and analyst became available as a result of other projects. These 130 samples, all from new lakes, were added to the 191-lake data set to create the 321-lake data set. The collection and construction of these data sets are outlined. Numerical analyses involving generalized linear modelling, constrained ordination techniques, weighted-averaging partial least-squares regression, and two different cross-validation procedures are used to asses the effects of increasing the size of the calibration data set from 191 to 321 lakes. The two data sets are used to reconstruct mean July temperature and mean annual precipitation for a Holocene site in northwest Norway and a Lateglacial site in west-central Norway. Overall, little is to be gained by increasing the modern data set beyond about 200 lakes in terms of modern model performance statistics, but the down-core reconstructions show less between-sample variability and are thus potentially more plausible and realistic when based on the 321-lake data set.

The Holocene lake history, vegetation history and climate history of Brurskardstjorni, an alpine lake in the Jotunheimen Mountains of south-central Norway, are reconstructed. The reconstructions are based on fossil pollen, plant macrofossils, diatoms, chironomids and sediment characteristics. Subsequent to deglaciation, the lake was formed at about 11,000 cal years BP. A diverse chironomid assemblage quickly colonised the lake, whereas the first diatoms were found about 400 years later. At that time, the lake water was turbid with a high pH. The surrounding soils were immature and unstable and dominated by open pioneer vegetation. Compared to the present, summer temperatures were warmer and there was less winter precipitation. From about 10,000 cal years BP, local organic production increased rapidly and from about 9,500 cal years BP a few macrofossils and a high pollen influx of birch suggest that the tree-line was close to the lake. Pine most likely reached its highest tree-line altitude around 9,000 cal years BP and has receded since that time. From about 5,000 cal years BP, the total amount of trees and shrubs decreased and the landscape became more open, probably due to decreasing temperatures and increasing effective moisture lowering the birch tree-line. Coinciding with a cooling during the last 3,000 years, lake-water pH decreased. There is large incongruence between the Holocene July temperatures inferred from pollen and chironomids. The biological proxies responded to a combined effect of environmental change and biotic interactions. This response is interpreted with reference to taxon-environment relationships in the modern calibration data sets and with reference to the latent structure and ecological demands of the fossil assemblages.

Little is known about the relationships between fossil oribatid mite assemblages in lake and mire sediments and the composition, abundance, and richness of their living communities. Because oribatid mites are a relatively new area of palaeolimnological study, there is a great lack of knowledge about the taphonomic processes that might affect fossil mite assemblages. The DOORMAT (Direct Observation Of Recent Macrofossils Across Tree-line) project was designed to study the transport and deposition of oribatid mites and plant remains in the tree-line area of western Norway. The present study also compares modern oribatid assemblages with fossil oribatid assemblages in a Holocene lake-sediment sequence from the nearby Trettetjorn, and considers the optimal location for studying fossil oribatid mites within a lake basin. Seven novel terrestrial traps (50 × 80 cm Astroturf doormats) were placed at major vegetational transitions along an altitudinal transect crossing the tree-line ecotone from 633 to 1,120 m a.s.l. at Upsete, west Norway. Three sediment traps were placed in Trettetjorn (810 m a.sl.) at the inlet, the middle, and near the outlet. In each terrestrial trap, the oribatid assemblage was found to be characteristic of the surrounding habitat. The lake-trap analyses showed that aquatic or moist-habitat species had the highest chance of being incorporated into the lake sediments; the number of terrestrial species decreased considerably from both outlet and inlet traps to the central trap in the deepest water. The area adjacent to the inlet of Trettetjorn would therefore be the optimal location for a sediment core for oribatid analysis. However, this conclusion is not supported when the modern trap results are compared with the Trettetjorn sequence from the lake centre.

While macrofossil remains of herbs and flowers have disintegrated beyond identification, pollen survives the digestive process and can be identified, sometimes to species level, and is hence an important tool in determining and reconstructing animal diets. This study compares macroscopic plant parts and pollen remains in faeces from grouse. While macroscopic remains reflect the quantity of bark, twigs, berries and leaves in the birds' food, the pollen also reflects other food, such as catkins, flower buds with developed pollen, flowers and pollen attached to leaves. Both techniques reflect that Betula and Salix are the most important food for grouse in early Spring. Pollen analysis shows that later in Spring, after snow-melt, the birds are attracted to different plants, firstly, it is taxa within the Ericales and their fruits from the previous year. The nutrient value of food in periods with more or less snow cover is based on the environmental conditions of the previous year. Later on, different...

The local development and forest history have been studied based on pollen, plant macrofossil, stomata and charcoal analysis from a small forest hollow situated within an old-growth, closed Picea abies forest, rich in epiphytic lichens and wood-decaying fungi in southeastern Norway. The main aims of this study are to identify the natural development, the disturbance history and the role of human impact of this forest stand during the last 9650 years. Forest trees have always been dominant in the landscape around the forest hollow. The forest was first dominated by Betula and Pinus sylvestris, and later these were co-dominant with thermophilous deciduous trees such as Corylus, Fagus, Fraxinus excelsior , Quercus, Tilia cordata and Ulmus. During the last 1000 years, Picea abies (spruce) has become the dominant tree in this area, but its presence can be traced back about 9300 years. The establishment of spruce caused a major shift in the ecosystem. Human impact and fire seem to have been the driving factors to create openings for spruce to establish. Based on estimates of palynological richness, the most diverse pollen assemblages are found in periods with intermediate levels of disturbance.

Quantitative reconstructions of mean July temperatures (T jul) based on new and previously published pollen-stratigraphical data covering the last 2000 years from 11 lakes in northern Fennoscandia and the Kola Peninsula are presented. T jul values are based on a previously published pollen-climate transfer function for the region with a root-mean-square error of prediction (RMSEP) of 0.99°C. The most obvious trend in the inferred temperatures from all sites is the general decrease in T jul during the last 2000 years. Pollen-inferred T jul values on average 0.18 ± 0.56°C (n = 91) higher than present (where “present” refers to the last three decades based on pollen-inferred T jul in core-top samples) are indicated between 0 and 1100 AD (2000–850 cal year BP), and temperatures −0.2 ± 0.47°C (n = 78) below present are inferred between 1100 and 1900 AD (850–50 cal year BP). No consistent temperature peak is observed during the ‘Medieval Warm Period’, ca. 900–1200 AD (1100–750 cal year BP), but the cooler period between 1100 and 1900 AD (850–50 cal year BP) corresponds in general with the ‘Little Ice Age’ (LIA). Consistently with independent stable isotopic data, the composite pollen-based record suggests that the coldest periods of the LIA date to 1500–1600 AD (450–350 cal year BP) and 1800–1850 AD (150–100 cal year BP). An abrupt warming occurred at about 1900 AD and the twentieth century is the warmest century since about 1000 AD (950 cal year BP).

With global warming, the distribution of warmth through the year is likely to change in the future and comparable changes may have occurred over the course of the Holocene. Its effect on vegetation composition and species distribution can be compared to that of a continental versus an oceanic climate. The distribution of five major tree species along a continentality gradient was studied in Fennoscandia based on distribution maps and on their proportions of pollen in surface-sediment samples. Both analyses indicate that the five arboreal species show similar patterns of response to a continentality index in the order Ulmus glabra, Corylus avellana, Quercus robur, Tilia cordata, and Picea abies from the most oceanic to most continental. Continentality, growing degree days above 5 degrees C, and January temperature were reconstructed quantitatively from four pollen diagrams using transfer functions based on a combined Fennoscandian pollen surface-sample data-set. Quantitative reconstructions indicate that the climate in Fennoscandia has become increasingly more continental over the last 7000 years, and this is largely an effect of winter cooling. Early Holocene vegetation composition has poor analogues to the present vegetation in Fennoscandia, which hampers quantitative reconstructions. Qualitative reconstructions suggest that the early Holocene in Fennoscandia was the most oceanic period, but probably with a high variability in temperature. (C) 2008 Elsevier Ltd. All rights reserved.

Pollen and plant macrofossil analyses from Svanavatnet in northern Norway provide records of past vegetation and climate in this region from c. 8700 cal.yr BP until the present. Pollen accumulation rates and the presence of plant macrofossils indicate that Betula pubescens (birch) was present from c. 8600 cal.yr BP and Pinus sylvestris (pine) from c. 8200 cal.yr BP. Quantitative climate is reconstructed using modern pollen-climate transfer functions based on weighted-averaging partial least squares regression. A rapid increase in mean July temperature (T-jul) and mean annual precipitation (P-ann) is inferred for the early Holocene. At times when tree abundance is at its highest and most diverse, inferred Tjul indicates maximum temperatures during the mid-Holocene of about 2 degrees C warmer than at present. During the same time period, inferred Pann is 200 - 300mm above present-day conditions until c. 3000 cal.yr BP. Mean January temperatures (T-jan) are reconstructed to be about 2 degrees C warmer than today from 8000 to 3500 cal.yr BP. After 3500 cal.yr BP until today, a gradual decrease is seen in all the reconstructed climate parameters, together with a reduction in tree abundance and the development of a mosaic of open vegetation with grasses, dwarf shrubs and wet areas, and of woodland containing B. pubescens, P. sylvestris and Picea abies (spruce).

Two records of July temperature and two records of reconstructed winter precipitation along the western coast of Norway have been combined to examine regional patterns in glacier activity and winter precipitation during the Holocene. The maritime glaciers in western Norway are mainly controlled by winter precipitation. Hence, fluctuations in magnitude and equilibrium-line altitude (ELA) of these glaciers reflect variability in wintertime atmospheric circulation patterns in the northeast Atlantic region. By combining an independent proxy for summer temperature with reconstructed ELAs during the Holocene, it is possible to reconstruct former winter precipitation. We track the dominant position of the westerlies during the Holocene by comparing records of winter precipitation along a 2000 km south–north coastal transect in Norway. Analyses of modern data on the evolution of the polar vortex indicate that there is a strong relationship between polar vortex and storm-track variability over the North Atlantic. Periods with increased winter precipitation along the coast of Norway are associated with a stronger effect of the westerlies, where differences in the distribution of precipitation are assumed to reflect changes in the position of the westerlies. The largest precipitation anomalies caused by a dominant southerly position of the westerlies are found around 2.8, 1.2 and 0.4 ka yrs BP. However, a general humid phase prevailed between 2.3 and 0.9 ka yrs BP.

Holocene lake and catchment environmental history and regional climate are reconstructed from lake sediments at Trettetjørn, a small lake situated close to the present-day treeline in western Norway. Sediments began to accumulate in the lake ca. 8575 (± 115) cal yr BP. Pollen-inferred mean July temperatures (Tjul) fluctuated below 12°C with two cooler phases ca. 8400 and 8200 cal yr BP. The pollen-inferred annual precipitation (Pann) was lowest during the early Holocene and varied around 1600 mm yr−1. At the same time the highest diatom-inferred pH values (6.8) were reconstructed, probably due to input of base cations from the immature catchment soils. Betula pubescens became established around the lake ca. 8270 cal BP, soon followed by Pinus sylvestris. Maximum Tjul of ca. 12.5°C occurred from 7760 to 5200 cal yr BP. The oribatid mite assemblages confirm the vegetation development from semiopen grassland to forest. Inferred Tjul was variable after 5200 cal yr BP and declined markedly around 4175 cal yr BP. At the same time more oceanic conditions are inferred with changes in the vegetation and mite assemblages suggesting the expansion of mires. After ca. 5000 cal yr BP and towards the present, the diatom concentration in the core becomes low and variable, thickness of the valves within the same taxon varies, and sometimes diatom frustules are completely absent from the sediment column. The diatom valve dissolution has affected both the diatom assemblages and the diatom-inferred pH up to the present-day. All proxies suggest that human impact affected the catchment after ca. 2000 cal yr BP followed by more intensive impact after ca. 1555 cal yr BP. The enlargement of the settlement at Upsete during the construction of the Bergen–Oslo railway (1894–1909 AD) is reflected by a charcoal peak and the presence of spheroidal carbonaceous particles coincides with a change in the diatom assemblages. Published version

Analyses of organic content, magnetic susceptibility, grain size and pollen in sediments from the proglacial lake Vanndalsvatnet in western Norway provide a high-resolution terrestrial record and pollen-based quantitative estimates of mean July and January temperatures and annual precipitation across the ∼ 8200 cal. yr BP event. Glaciers in the catchment melted away at approximately 8600 cal. yr BP. Immediately following deglaciation, a series of thin minerogenic layers indicate several abrupt, short-lived glacial episodes peaking at ∼ 8550, 8450, 8350, 8250, 8200, 7900, 7300 and 7150 cal. yr BP. A single, mid-Holocene glacial episode occurred at 4900-4800 cal. yr BP. Between 2000 and 1400 cal. yr BP, six short-lived glacial episodes occurred ∼ 2000, 1900, 1800, 1700, 1600, and 1500 cal. yr BP. The part of Spørteggbreen that drains to Vanndalsvatnet has existed continuously since ∼ 1400 cal. yr BP. Just prior to a first loss-on-ignition minimum reflecting a glacial episode centred at 8200 cal. yr BP, pollen-inferred July temperatures were relatively high, January temperatures were low, and annual precipitation was relatively low. During the period 8200-7900 cal. yr BP, July temperatures showed a falling trend. Both January temperature and annual precipitation, however, were relatively high. After 7900 cal. yr BP, July temperatures increased, but both January temperatures and annual precipitation were lower than in the preceding period. The pollen analytical and sedimentary data suggest that the glacial advance during the Finse event seems not to have been a response to cooler summers, but to milder winters and increasing precipitation (similar to a positive North Atlantic Oscillation weather mode).

Long-term tree-line fluctuations have been studied using pollen and plant macrofossils preserved in lake sediments from three sites on an oceanic to continental transect in southern Norway. After deglaciation the early Holocene vegetation developed from an open pioneer herb-dominated vegetation into dwarf-shrub heath with shrubs, which was soon colonised by Betula and later also by Pinus sylvestris at the two lower sites. Maximum tree-line altitudes occurred in the early-to mid-Holocene. P. sylvestris reached 100–150 m higher than at present in continental areas, and 35–100 m higher on the west coast during the Holocene. Betula pubescens grew at altitudes that today reach 1300 m a.s.l. in Jotunheimen and 800 m a.s.l. in western Norway. The Pinus forest was at the two southwestern sites mixed with Betula and Alnus was closer to the sites between 8500 and 7500 cal years BP. A shift from mixed pine-birch woodland to birch woodland is seen from ca. 4300 cal years BP with the development of a sub-alpine birch belt followed by further recession of the birch forest. On the west coast, birch dominated only during the last 500–1000 years. Further decrease of woodland and opening of the landscape in the last 2000 years occurred due to climatic change and human impact such as sheep and cattle grazing.

Reconstructions of mean July temperature (Tjul) and winter precipitation (Pw) for the last 11/500 years on the Folgefonna peninsula are presented. Tjul was reconstructed using pollen-climate transfer functions and Pw was reconstructed based on the exponential relationship between mean solid winter precipitation and ablation-season temperature at the equilibrium-line altitude (ELA) with a reconstructed former ELA, using Tjul as the proxy for ablation-season temperature. The reconstructions from the Folgefonna peninsula suggest that the early Holocene was relatively cool and dry until c. 8000 cal. yr BP, followed by a warm and humid mid-Holocene until c. 4000 cal. yr BP with inferred Tjul above 12°C and Pw reaching as high as 225% of the present day. Subsequent to c. 4000 cal. yr BP a reduction is seen in both inferred Tjul and Pw with large fluctuations during the last 500 years. In addition, new calculations of Pw from two glaciers (Hardangerjøkulen and Jostedalsbreen) in southern Norway are presented. The results show that Pw varied in phase at all glaciers, probably as a response to the same climate forcing factor. During the early Holocene a major shift is suggested between winds from the west and the east.

Holocene variations of Bjornbreen, Smorstabbtinden massif, west-central Jotunheimen are reconstructed from the lithostratigraphy of two alpine stream-bank mires flooded episodically by meltwater. The approach uses multiple sedimentological indicators (weight loss-on-ignition, mean grain size, grain-size fractions, bulk density, moisture content and magnetic susceptibility), an a priori model of overbank deposition of suspended glaciofluvial sediments, a detailed chronology based on 56 radiocarbon dates, and a Little Ice Age sedimentological analogue. Rapid, late-Preboreal deglaciation was indicated by immigration of Betula pubescens by 9700 cal. BP. An interval of at least 3000 years in the early Holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the Finse Event, the first at ca 8270–7900 cal. BP (Bjornbreen I Event) and the second at ca 7770–7540 cal. BP (Bjornbreen II Event). Neoglaciation began shortly before ca 5730 cal. BP with gradual build-up to the maximum of the Bjornbreen III Event at ca 4420 cal. BP. Later maxima occurred at ca 2750 cal. BP (Bjornbreen IV Event) and at 1300, 1260, 1060 and 790 cal. BP (all within the Bjornbreen V Event). Glaciers were smaller than today and possibly melted away on several occasions in the late Holocene (ca 3950, 1410 and 750 cal. BP). Minor maxima also occurred at ca 660 and 540 cal. BP, within the late Mediaeval Warm Period and the early Little Ice Age, respectively. The Little Ice Age maximum was dated to 213±25 BP (ca 205 cal. BP). The relative magnitudes of the main glacier maxima were determined: Erdalen Event>Little Ice Age Event (Bjornbreen VI)>Bjornbreen I (Finse Event) ≈ Bjornbreen II>Bjornbreen V⩾Bjornbreen IV>Bjornbreen III. These episodic events of varying magnitude and abruptness were used in conjunction with an independent summer-temperature proxy to reconstruct variations in equilibrium-line altitude (ELA) and a Holocene record of winter precipitation. Since the Preboreal, ELA varied within a range of about 390 m, and winter precipitation ranged between 40 and 160% of modern values. Winter precipitation variations appear to have been the main cause of these century- to millennial-scale Holocene glacier variations.

Palaeoecological records provide a rich source of information to explore how plant distribution ranges respond to climate changes, but their use is complicated by the fact that, especially when based on pollen data, they are often spatially too inaccurate to reliably determine past range limits. To solve this problem, we focus on hazel ( Corylus avellana), a tree species with large and heavy fruits (nuts), which provide firm evidence of the local occurrence of species in the past. We combine the fossil nut records of hazel from Fennoscandia, map its maximum distribution range during the Holocene thermal maximum (HTM) and compare the fossil record with the Holocene hazel range shift as simulated by the LPJ-GUESS dynamic vegetation model. The results show that the current northern range limit of hazel in central and eastern Fennoscandia is constrained by too short growing seasons and too long and cold winters and demonstrate that the species responded to the HTM warming of about 2.5°C (relative to the present) by shifting its range limit up to 63–64°N, reached a rough equilibrium with the HTM climatic conditions and retreated from there to about 60°N during the last 4000 years in response to the late-Holocene cooling. Thus, the projected future warming of about 2.5°C would reverse the long-term southward retraction of species’ northern range limit in Europe and is likely to lead to hazel being a common, regeneratively reproductive species up to 63–64°N. In addition to the accuracy of the projected warming, the likelihood of this scenario will depend on inter-specific competition with other tree taxa and the potential of hazel to migrate and its population to grow in balance with the warming. In general, the range dynamics from the HTM to the present suggest a tight climatic control over hazel’s range limit in Fennoscandia.

A contribution to the PAGES Focus 4 Land Use and Cover Theme ABSTRACT: We present quantitative reconstructions of regional vegetation cover in north western Europe western Europe north of the Alps and eastern Europe for five time windows in the Holocene [around 6k 3k 0.5k 0.2k and 0.05k calendar years before present (bp)] at a 1° × 1° spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant functional types and three land cover types [evergreen trees summer green (deciduous) trees and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k 0.5k and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe in particular Britain and Ireland. Furthermore the relationship between summer green and evergreen trees and between individual tree taxa differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance when Pinus is dominant over Picea as pollen percentages Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover–climate interactions biodiversity and human resources.

This paper presents multi-proxy palaeolimnological analyses from recent sediments in the nine CASSARINA lakes in northernmost Africa, three from each of Morocco, Tunisia, and Egypt. The lakes are diverse, ranging from hypersaline to brackish lagoons and fresh-water lakes from high to low conductivity and pH. The macrofossils analysed include fruits, seeds, and vegetative remains of plants, lagoon and fresh-water Mollusca, a range of other aquatic animals, and from one site in each country, Ostracoda and Foraminifera. The diverse macrofossils are multi-proxy indicators of environmental change, and demonstrate changes in response to human activities in the catchments of all the lakes. The three Egyptian Nile Delta lakes have received massive inputs of fresh-water due to modifications of the flow of the R. Nile culminating in the Aswan High Dam built in 1964. Elsewhere, water withdrawal is frequently a serious threat. One lake with high biodiversity in Morocco has been drained and cultivated, and a rare acid-water lake in Tunisia is in danger of drying up. The internationally famous Garaet El Ichkeul in Tunisia, which was so important for birds, has become permanently saline with a loss of diversity. All the lakes are affected by agricultural and/or urban run-off and are experiencing changes as a result of human activities. Several are in a marginally sustainable condition, whereas others are permanently damaged.

International audience; This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, ∼ 6 and ∼ 0.2 k BP in Eu-rope. We apply the Rossby Centre regional climate model RCA3, a regional climate model with 50 km spatial resolution, for both time periods, considering three alternative descriptions of the past vegetation: (i) potential natural vegetation (V) simulated by the dynamic vegetation model LPJ-GUESS, (ii) potential vegetation with anthro-pogenic land use (deforestation) from the HYDE3.1 (History Database of the Global Environment) scenario (V + H3.1), and (iii) potential vegetation with anthropogenic land use Published by Copernicus Publications on behalf of the European Geosciences Union. 662 G. Strandberg et al.: Sensitivity to changes in anthropogenic deforestation from the KK10 scenario (V + KK10). The climate model results show that the simulated effects of deforestation depend on both local/regional climate and vegetation characteristics. At ∼ 6 k BP the extent of simulated deforestation in Europe is generally small, but there are areas where deforestation is large enough to produce significant differences in summer temperatures of 0.5–1 • C. At ∼ 0.2 k BP, extensive deforestation , particularly according to the KK10 model, leads to significant temperature differences in large parts of Europe in both winter and summer. In winter, deforestation leads to lower temperatures because of the differences in albedo between forested and unforested areas, particularly in the snow-covered regions. In summer, deforestation leads to higher temperatures in central and eastern Europe because evapotranspiration from unforested areas is lower than from forests. Summer evaporation is already limited in the south-ernmost parts of Europe under potential vegetation conditions and, therefore, cannot become much lower. Accordingly , the albedo effect dominates in southern Europe also in summer, which implies that deforestation causes a decrease in temperatures. Differences in summer temperature due to deforestation range from −1 • C in southwestern Europe to +1 • C in eastern Europe. The choice of anthropogenic land-cover scenario has a significant influence on the simulated climate, but uncertainties in palaeoclimate proxy data for the two time periods do not allow for a definitive discrimination among climate model results.

Reliable estimates of past land cover are critical for assessing potential effects of anthropogenic land-cover changes on past earth surface-climate feedbacks and landscape complexity. Fossil pollen records from lakes and bogs have provided important information on past natural and human-induced vegetation cover. However, those records provide only point estimates of past land cover, and not the spatially continuous maps at regional and sub-continental scales needed for climate modelling. We propose a set of statistical models that create spatially continuous maps of past land cover by combining two data sets: 1) pollen-based point estimates of past land cover (from the REVEALS model) and 2) spatially continuous estimates of past land cover, obtained by combining simulated potential vegetation (from LPJ-GUESS) with an anthropogenic land-cover change scenario (KK10). The proposed models rely on statistical methodology for compositional data and use Gaussian Markov Random Fields to model spatial dependencies in the data. Land-cover reconstructions are presented for three time windows in Europe: 0.05, 0.2, and 6 ka years before present (BP). The models are evaluated through cross-validation, deviance information criteria and by comparing the reconstruction of the 0.05 ka time window to the present-day land-cover data compiled by the European Forest Institute (EFI). For 0.05 ka, the proposed models provide reconstructions that are closer to the EFI data than either the REVEALS- or LPJ-GUESS/KK10-based estimates; thus the statistical combination of the two estimates improves the reconstruction. The reconstruction by the proposed models for 0.2 ka is also good. For 6 ka, however, the large differences between the REVEALS- and LPJ-GUESS/KK10-based estimates reduce the reliability of the proposed models. Possible reasons for the increased differences between REVEALS and LPJ-GUESS/KK10 for older time periods and further improvement of the proposed models are discussed.

We present pollen-based reconstructions of the spatio-temporal dynamics of northern European regional vegetation abundance through the Holocene. We apply the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model using fossil pollen records from eighteen sites within five modern biomes in the region. The eighteen sites are classified into four time-trajectory types on the basis of principal components analysis of both the REVEALS-based vegetation estimates (RVs) and the pollen percentage (PPs). The four trajectory types are more clearly separated for RVs than PPs. Further, the timing of major Holocene shifts, rates of compositional change, and diversity indices (turnover and evenness) differ between RVs and PPs. The differences are due to the reduction by REVEALS of biases in fossil pollen assemblages caused by different basin size, and inter-taxonomic differences in pollen productivity and dispersal properties. For example, in comparison to the PPs, the RVs show an earlier increase in Corylus and Ulmus in the early-Holocene and a more pronounced increase in grassland and deforested areas since the mid-Holocene. The results suggest that the influence of deforestation and agricultural activities on plant composition and abundance from Neolithic times was stronger than previously inferred from PPs. Relative to PPs, RVs show a more rapid compositional change, a largest decrease in turnover, and less variable evenness in most of northern Europe since 5200 cal yr BP. All these changes are primarily related to the strong impact of human activities on the vegetation. This study demonstrates that RV-based estimates of diversity indices, timing of shifts, and rates of change in reconstructed vegetation provide new insights into the timing and magnitude of major human distribution on Holocene regional, vegetation, feature that are critical in the assessment of human impact on vegetation, land-cover, biodiversity, and climate in the past. (C) Elsevier Ltd.All tights reserved.

Davis, B.A.S. et al., Modern pollen samples provide an invaluable research tool for helping to interpret the quaternary fossil pollen record, allowing investigation of the relationship between pollen as the proxy and the environmental parameters such as vegetation, land-use, and climate that the pollen proxy represents. The European Modern Pollen Database (EMPD) is a new initiative within the European Pollen Database (EPD) to establish a publicly accessible repository of modern (surface sample) pollen data. This new database will complement the EPD, which at present holds only fossil sedimentary pollen data. The EMPD is freely available online to the scientific community and currently has information on almost 5,000 pollen samples from throughout the Euro-Siberian and Mediterranean regions, contributed by over 40 individuals and research groups. Here we describe how the EMPD was constructed, the various tables and their fields, problems and errors, quality controls, and continuing efforts to improve the available data.