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The Black Summer bushfires (2019-2020) cost the Australian economy over 100 billion dollars and burnt a total of 18 million hectares. In just one season, around 20% of Australia's Eucalyptus forests burnt down and billions of animals perished. Recent catastrophic fires in Australia and North America have made scientists and policymakers question how the disruption of First Nations' burning practices has impacted fuel loads. For instance, we have learnt from modern Australian Indigenous communities, historical literature, and art works that Indigenous peoples have used cultural burning to rejuvenate patches of land and preserve open vegetation for hunting and cultural purposes. The advent of British invasion brought a change in the type of fire regimes and landscape management across much of the continent, which may have led to an increase in flammable fuels in forest settings. However, the actual degree of land-cover modification by early settlers has only been often debated in the academic literature and within management stakeholders.The quantification of past land cover is needed to address such debates. Pollen is the key proxy to track past vegetation changes, but pollen spectra suffer from some important biases e.g. taphonomy, pollen productivity, dispersal capability. Estimating past vegetation cover from sedimentary pollen composition requires to correct for productivity and dispersal biases using empirical-based models of the pollen-vegetation relationship. Such models for quantitative vegetation reconstruction (e.g. REVEALS) have yet been mostly applied in the Northern Hemisphere in the last 15 years - here we present recent applications of this methodology from Australia. We show the quantification of land cover changes through pre- and post- British invasion on multiple records (n=51) across the southeastern Australian region. This represents the first regional application of REVEALS within the Australian continent.We provide the first empirical evidence that the regional landscape before British invasion was a cultural landscape with limited tree cover as it was maintained by Indigenous Australians through cultural burning. Our findings suggest that the removal of Indigenous vegetation management has altered woodland fuel structure and that much of the region was predominantly open before colonial invasion. The post-colonial land modification has resonance in wildfire occurrence and management under the pressing challenges posed by climate change.

Lake‐level reconstructions are a key tool in hydro‐climate reconstructions, based on the assumption that lake‐level changes primarily reflect climatic changes. Although it is known that land cover changes can affect evapotranspiration and groundwater formation, this factor commonly receives little attention in the interpretation of past lake‐level changes. To address this issue in more detail, we explore the effects of land cover change on Holocene lake‐level fluctuations in Lake Tiefer See in the lowlands of northeastern Germany. We reconstruct lake‐level changes based on the analysis of 28 sediment records from different water depths and from the shore. We compare the results with land cover changes inferred from pollen data. We also apply hydrological modelling to quantify effects of land cover change on evapotranspiration and the lake level. Our reconstruction shows an overall lake‐level amplitude of about 10 m during the Holocene, with the highest fluctuations during the Early and Late Holocene. Only smaller fluctuations during the Middle Holocene can unambiguously be attributed to climatic fluctuations because the land cover was stable during that period. Fluctuations during the Early and Late Holocene are at least partly related to changes in natural and anthropogenic land cover. For several intervals the reconstructed lake‐level changes agree well with variations in modelled groundwater recharge inferred from land cover changes. In general, the observed amplitudes of lake‐level fluctuations are larger than expected from climatic changes alone and thus underline that land cover changes in lake catchments must be considered in climatic interpretations of past lake‐level fluctuations., Helmholtz Association http://dx.doi.org/10.13039/501100001656, Leibniz‐Gemeinschaft http://dx.doi.org/10.13039/501100001664

Connecting pathways are essential for cultural and economic exchange. Commonly, historians investigate the role of routes for cultural development, whereas the environmental impacts of historical routes attract less attention. Here, we present a high-resolution reconstruction of the impact of the major trade route via Marchionis in the southern Baltic lowlands on landscape evolution since more than 800 years. We combine precisely dated annually laminated sediments from Lake Czechowskie alongside via Marchionis and pollen data at 5-year resolution together with historical data. The transformation from a quasi-natural to a cultural landscape occurred in three phases (1) an early phase until the mid-fourteenth century with slowly increasing human impact. (2) an intensification of environmental disturbance until (3) the mid-nineteenth century when via Marchionis became a modern traffic route with strong environmental impacts. Superimposed on the long-term development were repeated interruptions by short-term downturns related to societal crisis and political decisions.

Pollen productivity estimates (PPEs) are a key parameter for quantitative land-cover reconstructions from pollen data. PPEs are commonly estimated using modern pollen-vegetation data sets and the extended R-value (ERV) model. Prominent discrepancies in the existing studies question the reliability of the approach. We here propose an implementation of the ERV model in the R environment for statistical computing, which allows for simplified application and testing. Using simulated pollen-vegetation data sets, we explore sensitivity of ERV application to (1) number of sites, (2) vegetation structure, (3) basin size, (4) noise in the data, and (5) dispersal model selection. The simulations show that noise in the (pollen) data and dispersal model selection are critical factors in ERV application. Pollen count errors imply prominent PPE errors mainly for taxa with low counts, usually low pollen producers. Applied with an unsuited dispersal model, ERV tends to produce wrong PPEs for additional taxa. In a comparison of the still widely applied Prentice model and a Lagrangian stochastic model (LSM), errors are highest for taxa with high and low fall speed of pollen. The errors reflect the too high influence of fall speed in the Prentice model. ERV studies often use local scale pollen data from for example, moss polsters. Describing pollen dispersal on his local scale is particularly complex due to a range of disturbing factors, including differential release height. Considering the importance of the dispersal model in the approach, and the very large uncertainties in dispersal on short distance, we advise to carry out ERV studies with pollen data from open areas or basins that lack local pollen deposition of the taxa of interest.

To understand the resilience of African savannas to global change, quantitative information on the long-term dynamics of vegetation is required. Past dynamics can be reconstructed with the REVEALS model, which requires pollen productivity estimates (PPE) that are calibrated using surface pollen and vegetation data. Here we calculated PPE values for five savanna taxa using the extended R-value (ERV) model and two pollen dispersal options: the Gaussian plume model (GPM) and the Lagrangian stochastic model (LSM). The ERV calculations failed to produce a reliable PPE for Poaceae. We therefore used Combretaceae as the reference taxon – although values obtained with Poaceae as the reference taxon are presented in the supplement. Our results indicate that Combretaceae is the taxon with the highest pollen productivity and Grewia the taxon with the lowest productivity. Acacia and Dichrostachys are intermediate pollen producers. We find no clear indication of whether the GPM PPEs or the LSM PPEs are more realistic, but the differences between these values confirmed that the pollen fall speed has a greater effect in the modelling of GPM than in the LSM. We also applied REVEALS to the pollen record of Lake Otjikoto (northern Namibia) and obtained the first quantitative reconstruction of the last 130 years of vegetation history in the region. Cover estimates for Poaceae indicate the predominance of a semi-open landscape throughout the 20th century, while cover values below 50% since the 21st century correspond to a thick savanna. This change in grass cover is associated with the spread of Vachellia, Senegalia and Grewia reflecting an encroached state.

Knowledge about the timing, amplitude and spatial gradients of Holocene environmental variability in the circum-Baltic region is key to understanding its responses to ongoing climate change. Based on a multi-dating and proxy approach, we reconstruct changes in productivity using total organic carbon (TOC) contents in sediments of Lake Kälksjön (KKJ) from west–central Sweden spanning the last 9612 (+255/-114) years. An exception is the period from 1878 CE until today, in which sedimentation was dominated by anthropogenic lake level lowering and land use. In-lake productivity was higher during periods of warmer winters with shortened ice cover and prolonged growing seasons. A multi-millennial increase in productivity throughout the last ∼ 9600 years is associated with progressively warmer winters in northwestern Europe, likely triggered by the coinciding increase in Northern Hemisphere winter insolation. Decadal to centennial periods of higher productivity in KKJ tend to correspond to warmer winters during a more positive North Atlantic Oscillation (NAO) polarity, as reconstructed for the last 8000 years. In consequence, we assume our decadal to centennial productivity record from KKJ sediments for the complete ∼ 9600 years to provide a qualitative record of NAO polarity. A shift towards higher productivity variability at ∼ 5450 cal a BP is hypothesized to reflect a reinforcement of NAO-like atmospheric circulation variability, possibly driven by more vigorous changes in North Atlantic deep-water formation.

The Arctic is experiencing substantial warming with possibly large consequences for global climate when its large soil carbon stocks are mobilized. Yet the functioning of permafrost peatlands, which contain considerable amounts of carbon, is still not fully understood. Palaeoecological studies may contribute to unravelling this functioning but require actuo-ecological calibration of the environmental proxies used. Testate amoebae may be valuable proxies for palaeoecological reconstruction, but indeed still large gaps exist regarding their present-day distribution in Arctic peatlands. This study presents the distribution of testate amoebae taxa with high (1 m) spatial resolution along a transect crossing an Arctic ice-wedge polygon mire. Whereas the polygon ridges are characterised by taxa that are known to be typical of dry environments or hydrologically indifferent, the low-lying wet settings show a mixture of wet- and dry-living taxa, indicating seasonally rapidly changing conditions. High testate amoebae concentrations were only found on the dry polygon ridges. Archerella flavum occurs in various moss species in drier polygon settings, in contrast to temperate regions where the species is exclusively known from wet sites with Sphagnum, which probably relates to the special moisture conditions associated with permafrost. To compare the results of full testate amoebae analysis with those of palynology, each surface sample was split into two parts and prepared and analysed following standard testate amoebae analysis and palynological methods, respectively. Clear differences in qualitative content were found and can be attributed to the different preparation methods and to possible small (a few cm) differences in sample location. Nevertheless, the indicative value of testate amoebae found in pollen samples adds importantly to the ecological inference of palynological studies. Overall testate amoebae research is very valuable for the recognition of past ecological settings and the accurate reconstruction of past hydrological regimes in Arctic mires. Considerably more research is, however, necessary to cover the total (ecological) diversity of testate amoebae populations in NE Siberia.

Summary The ongoing spread of forest fires in the Siberian Arctic raises concerns on how far increasing temperatures and fire occurrence lead to biome shifts from tundra to summergreen or evergreen boreal forest. Here, we investigate vegetation and fire regime shifts during late MIS 12 and MIS 11 c. 390–430 kyrs ago using sedimentary charcoal, anhydrosugars and pollen from Lake El'gygytgyn, NE Siberia. We find different types of centennial-to-millennial-scale biome shifts, partly accompanied by fire regime shifts. We assess the role of fire in driving and/or responding to biome changes, especially periods of abrupt warming, to gain understanding of what we can expect during the ongoing warming of the high-northern latitudes.

Since the twelfth century, forest areas in the upper reaches of the low mountain ranges of central Europe provided an important source of wood and charcoal especially for mining and smelting as well as glass production. In this case study from a site in the upper Erzgebirge region (Ore Mountains), results from archeological, geophysical, pedo-sedimentological, geochemical, anthracological, and palynological analyses have been closely linked to allow for a diachronic reconstruction of changing land use and varying intensities of human impact with a special focus on the fourteenth to the twentieth century. While human presence during the thirteenth century can only be assumed from archeological material, the establishment of glass kilns together with quartz mining shafts during the fourteenth century has left behind more prominent traces in the landscape. However, although glass production is generally assumed to have caused intensive deforestation, the impact on this site appears rather weak compared to the sixteenth century onwards, when charcoal production, probably associated with emerging mining activities in the region, became important. Local deforestation and soil erosion has been associated mainly with this later phase of charcoal production and may indicate that the human impact of glass production is sometimes overestimated.

Vegetation distribution and pollen deposition were studied in a complex of degraded ice-wedge polygon mires near Pokhodsk (NE Siberia) in order to obtain insight in the relation between actual vegetation and pollen deposition in microtopographic landscape elements. Pollen surface samples with 1 m spacing were collected along a transect and compared with the vegetation at the sample quadrats, with the vegetation in the adjacent quadrats, and with the vegetation at larger distances. A clear regional pollen signal of plants growing outside the study plot was found in the large central depression for pollen types attributable to Comarum palustre , Betula , and Ericales. Local pollen values (i.e. exceeding the regional background deposition values) are restricted to quadrats where the associated taxa are present within 1 m distance (e.g. Comarum palustre , Betula and Rubus chamaemorus ). Several plant taxa (e.g. Cyperaceae, Ericales, Pedicularis and Sphagnum ) show both high and low pollen deposition values in quadrats where the taxa actually occur, indicating differential pollen production/deposition among specimens of the same taxon. A local signal of grasses and Salix is not noticeable and the pollen signal of these taxa is mainly attributable to plant specimens growing in a larger area. The non-pollen palynomorphs include principally testate amoebae, which dominate on the polygon ridges. Size-frequency analyses show that pollen attributable to dwarf Betula has in the NE Siberian Arctic a large morphological variation.

Knowledge of the distribution, types and properties of buried soils, i.e. palaeosols, is essential in understanding how lowlands in northern central Europe have changed over past millennia. This is an indispensable requirement for evaluating long-term human impact including soil erosion and land-cover dynamics. In the Serrahn area (62 km2), a young glacial landscape representative for northeastern Germany and part of the Muritz National Park, 26 pedosedimentary sections were documented and analysed. To this end, a multiproxy-approach was applied using pedology, micromorphology, geochronology, and palaeoecology. Statistical and spatial analyses of c. 5200 soil profiles, of which 10% contain palaeosols, show that buried soils cover an area of 5.7 km2, i.e. 9% of the area studied. Most palaeosols are Cambisols, Arenosols and Gleysols. Palaeosols are mainly covered by aeolian and colluvial sands, as well as by lacustrine sands and peat. Radiocarbon and luminescence dating together with palynological and anthracological data reveal that former land surfaces were dominantly buried through erosion triggered by human activity in the late Holocene. In addition, but to a clearly smaller extent, Lateglacial/early Holocene palaeosols and cover sediments occur. Following Medieval clear-cutting and intensive land use, the study area is today again widely forested. The high share of buried land surfaces detected here is expected to be representative for the hilly glacial landscapes even in the wider region, i.e. in northern central Europe, and should be considered in soil mapping, soil carbon budgeting and assessments of past human impact.

Reconstructing past vegetation abundance and land-cover changes through time has important implications in land management and climate modelling. To date palaeovegetation reconstructions in Australia have been limited to qualitative or semi-quantitative inferences from pollen data. Testing pollen dispersal models constitutes a crucial step in developing quantitative past vegetation and land cover reconstructions. Thus far, the application of quantitative pollen dispersal models has been restricted to regions dominated by wind-pollinated plants (e.g. Europe) and their performance in a landscape dominated by animal-pollinated plant taxa is still unexplored. Here we test, for the first time in Australia, two well-known pollen dispersal models to assess their performance in the wind- and animal-pollinated vegetation mosaics of western Tasmania. We focus on a mix of wind- (6 taxa) and animal- (7 taxa) pollinated species that comprise the most common pollen types and key representatives of the dominant vegetation formations. Pollen Productivity Estimates and Relevant Source Area of Pollen obtained using Lagrangian Stochastic turbulent simulations appear to be more realistic when compared to the results from the widely used Gaussian Plume Model.

The extended downscaling approach (EDA) is a quantitative method in palynology that aims to detect past vegetation patterns and communities in the landscape. The EDA uses iterative forward modelling to fit vegetation composition to robust landscape patterns by comparing simulated with actually observed pollen deposition. The approach employs a set of pollen records, preferably from medium sized to large lakes or peatlands, as well as maps of robust landscape patterns, such as soils and relief. So far, the EDA has been applied in simple settings with only few taxa. To be able to apply the model also in more complex situations, we have implemented the EDA in the R environment for statistical computing. We here test the performance of the EDAinR function in five synthetic scenarios of increasing complexity. In all cases, the EDA is well able to reconstruct vegetation composition, also on rare landscape units. If uncertainty is added both to the pollen data and pollen productivity estimates, the EDA still correctly reconstructs species composition on more than 90% of the total landscape in all scenarios, underlining that the EDA performs well also in complex settings. The EDAinR function will be available within the R package DISQOVER.

Hitherto, the Landscape Reconstruction Algorithm (LRA) has been the only truly quantitative approach to stand-scale palynology. However, the LRA requires information on pollen productivity and dispersal, which is not always available. The alternative approach MARCO POLO (MAnipulating pollen sums to ReCOnstruct POllen of Local Origin) presented here is solely based on pollen values and does not rely on a pollen dispersal function. In a stepwise fashion, MARCO POLO removes those pollen types from the pollen sum whose values are significantly higher than in a neighbouring large basin. The resulting regional pollen sum is free of the disturbing factor of (extra-)local pollen. Based on this sum, comparison with the pollen record from the large basin allows calculating sharp (extra-)local signals. Treating the (extra-)local pollen portion with representation factors ( R-values) then produces a quantitative reconstruction of the stand-scale vegetation composition. We tested MARCO POLO and the LRA on a dataset of pollen surface samples and forest vegetation relevés from northern Central Europe. Both approaches reconstruct the presence or absence of taxa at the stand scale within a small margin of error. Where observed cover was ⩾2%, both models always reconstructed presence, where modelled cover was ⩾2% the taxon was always present. Overall, both approaches perform well in reconstructing the cover of taxa within a 100-m radius. In our tests, MARCO POLO is slightly better at reconstructing cover values for more taxa. Although some model parameters evidently need revision, the simple correlative approach of MARCO POLO appears to perform at least as well as the complex LRA model.

In this paper the concept of resilience is discussed on the base of 13 case studies from the German branch of the International Long-Term Ecological Research Program. In the introduction the resilience approach is presented as one possibility to describe ecosystem dynamics. The relations with the concepts of adaptability and ecological integrity are discussed and the research questions are formulated. The focal research objectives are related to the conditions of resilient behaviour of ecosystems, the role of spatio-temporal scales, the differences between short- or long-term dynamics, the basic methodological requirements to exactly define resilience, the role of the reference state and indicators and the suitability of resilience as a management concept. The main part of the paper consists of 13 small case study descriptions, which demonstrate phase transitions and resilient dynamics of several terrestrial and aquatic ecosystems at different time scales. In the discussion, some problems arising from the interpretation of the time series are highlighted and discussed. The topics of discussion are the conceptual challenges of the resilience approach, methodological problems, the role of indicator selection, the complex interactions between different disturbances, the significance of time scales and a comparison of the case studies. The article ends with a conclusion which focuses on the demand to link resilience with adaptability, in order to support the long-term dynamics of ecosystem development. published

The REVEALS model is applied in quantitative vegetation reconstruction to translate pollen percentage data from large lakes and peatlands into regional vegetation composition. The model was first presented in 2007 and has gained increasing attention. It is a core element of the Landcover 6k initiative within the PAGES project. The REVEALS model has two critical components: the pollen dispersal model and pollen productivity estimates (PPEs). To study the consequences of model settings, we implemented REVEALS in R. We use a state-of-the-art Lagrangian stochastic dispersal model (LSM) and compare model outcomes with calculations based on a conventional Gaussian plume dispersal model (GPM). In the LSM turbulence causes pollen fall speed to have little effect on the dispersal pattern whereas fall speed is a major factor in the GPM. Dispersal models are also used to derive PPEs. The unrealistic GPM produces PPEs that do not describe actual pollen productivity, but rather serve as a basin specific correction factor. A test with pollen and vegetation data from NE Germany shows that REVEALS performs best when applied with the LSM. REVEALS applications with the GPM can produce realistic results, but only if unrealistic PPEs are used. We discuss the derivation of PPEs and further REVEALS applications. Our REVEALS implementation is freely available as the ‘REVEALSinR’ function within the R package DISQOVER. REVEALSinR offers an environment for experimentation and analysing model sensitivities. We encourage further experiments and welcome comments on our tool.

Fossil wood and varved lake sediments allow proxy analysis with exceptionally high, (sub-)annual resolution. Both archives provide dating through ring and layer counting, yet with different accuracy. In wood, counting errors are small and can be eliminated through cross-dating because tree-rings show regionally synchronous patterns. In varved sediments, counting errors are larger and cross-dating is hampered by missing regional patterns in varve parameters. Here, we test whether annual pollen analysis is suited to synchronize varve records. To that end, annual pollen deposition was estimated in three short cores from two lakes in north-eastern Germany for the period 1980−2017 CE. Analysis has focused on Fagus sylvatica and Picea abies, which show the strongest annual variations in flowering (mast). For both tree taxa, annual flowering variations recorded by forest and pollen monitoring are well represented in varved lake sediments, hence indeed allow us to synchronize the records. Some pollen mast events were not recognized, which may relate to sampling uncertainties, redeposition or regional variations in flowering. In Fagus sylvatica, intense flowering limits wood growth in the same year. Peaks in pollen deposition hence correlate with minima in tree-ring width, which provides a link between varved lake sediments and fossil wood.

Wildfire occurrence is influenced by climate, vegetation and human activities. A key challenge for understanding fire-climate-vegetation interactions is to quantify the effect vegetation has in mediating fire regime. Here, we explore the relative importance of Holocene land cover and dominant functional forest type, and climate dynamics on biomass burned in temperate and boreo-nemoral regions of Central and Eastern Europe over the past 12 ka BP years. We used an extensive data set of Holocene pollen and sedimentary charcoal records, in combination with climate simulations and novel statistical modelling. Biomass burned was highest during the early Holocene and lowest during the mid Holocene in all three ecoregions, but diverged more markedly over the past 3–4 ka BP. Although the climate was an important driver of fire hazard during the warm and dry early Holocene, tree cover was consistently the strongest predictor of past biomass burning. In temperate forests, biomass burned was high at ~ 45 % tree cover and decreased strongly towards 60 % tree cover. In needleleaf dominated forests, biomass burned was highest at ~ 60–65 % tree cover and abruptly declined at > 65 % tree cover. Biomass burned also increased when arable lands and grasslands reached ~ 15–20 %, although this relationship was highly dynamic depending on land use intensity throughout ignition and fuel type and availability. Our observations cover the full range of Holocene climate variability and land cover changes and illustrates that percentages of land cover is a key predictor of the probability of fire occurrence over timescales of centuries to millennia. We suggest that long-term fire risk may be effectively reduced through land cover management, given that land cover has controlled fire regimes under the dynamic climates of the Holocene.

Fire is a natural component of global biogeochemical cycles and closely related to changes in human land use. Whereas climate-fuel relationships seem to drive both global and subcontinental fire regimes, human-induced fires are prominent mainly on a local scale. Furthermore, the basic assumption that relates humans and fire regimes in terms of population densities, suggesting that few human-induced fires should occur in periods and areas of low population density, is currently debated. Here, we analyze human-fire relationships throughout the Holocene and discuss how and to what extent human-driven fires affected the landscape transformation in the Central European Lowlands (CEL). We present sedimentary charcoal composites on three spatial scales and compare them with climate model output and land cover reconstructions from pollen records. Our findings indicate that widespread natural fires only occurred during the early Holocene. Natural conditions (climate and vegetation) limited the extent of wildfires beginning 8500 cal. BP, and diverging subregional charcoal composites suggest that Mesolithic hunter-gatherers maintained a culturally diverse use of fire. Divergence in regional charcoal composites marks the spread of sedentary cultures in the western and eastern CEL. The intensification of human land use during the last millennium drove an increase in fire activity to early-Holocene levels across the CEL. Hence, humans have significantly affected natural fire regimes beyond the local scale – even in periods of low population densities – depending on diverse cultural land-use strategies. We find that humans have strongly affected land-cover- and biogeochemical cycles since Mesolithic times.

Aim: To test competing hypotheses about the timing and extent of Holocene landscape opening using pollen-based quantitative land-cover estimates. Location: Dove Lake, Tasmanian Wilderness World Heritage Area, Australia. Methods: Fossil pollen data were incorporated into pollen dispersal models and corrected for differences in pollen productivity among key plant taxa. Mechanistic models (REVEALS-Regional Estimates of VEgetation Abundance from Large Sites) employing different models for pollen dispersal (Gaussian plume and Lagrangian stochastic models) were evaluated and applied in the Southern Hemisphere for the first time. Results: Validation of the REVEALS model with vegetation cover data suggests an overall better performance of the Lagrangian stochastic model. Regional land-cover estimates for forest and non-forest plant taxa show persistent landscape openness throughout the Holocene (average landscape openness similar to 50%). Gymnoschoenus sphaerocephalus, an indicator of moorland vegetation, shows higher values during the early Holocene (11.7-9 ka) and declines slightly through the mid-Holocene (9-4.5 ka) during a phase of partial landscape afforestation. Rain forest cover reduced (from similar to 40% to similar to 20%) during the period between 4.2-3.5 ka. Main conclusions: Pollen percentages severely under-represent landscape openness in western Tasmania and this bias has fostered an over-estimation of Holocene forest cover from pollen data. Treeless vegetation dominated Holocene landscapes of the Dove Lake area, allowing us to reject models of landscape evolution that invoke late-Holocene replacement of a rain forest-dominated landscape by moorland. Instead, we confirm a model of Late Pleistocene inheritance of open vegetation. Rapid forest decline occurred after c.4 ka, likely in response to regional moisture decline. Australian Research Council; AINSE AWARD [ALNGRA16024]; AINSE PGRA scholarship [12039] info:eu-repo/semantics/publishedVersion

The warming at the Younger Dryas–Holocene transition (∼11,600 cal. BP) triggered the rearrangement of vegetation across Europe. To better understand that response, we analysed both an extended fossil pollen data set and robust present-day site parameters from NE Germany in a data model comparison approach. This approach allowed to quantify past plant abundances in sub-regional landscape patterns, as defined by soil types and relief. Betula was the first tree taxon to expand from scattered stands that already existed during the Younger Dryas. The major tree taxa Betula and Pinus fully established after 200–400 years as largely separated stands of Pinus on well drained sandy and Betula on fertile morainic soils. Corylus started to spread after 11,200 cal. BP, yet the final expansion was delayed until ∼10,800 cal. BP. Corylus established on gleyic soils, from which it largely expelled Betula . Throughout the first two millennia of the Holocene, open grasslands existed on fine grained soils, where seasonal dryness prevented the establishment of deciduous trees.

The Saksunarvatn Ash is an important tephra layer for the correlation of Early Holocene environmental records in northern Europe, the North Atlantic and Greenland. The Saksunarvatn Ash is believed to have been produced by eruptions of the Grimsvotn volcanic system 10.3 ka BP, which had two axes of dispersal, one plume in a north-west direction over northern Iceland and into Greenland, and a second southerly plume covering the Faroe Isles, Shetland Isles, western Norway and northern Germany. Here we present data from Potremser Moor, north-east Germany, extending the easterly margin of the ash fallout zone. We also present single grain trace element data from the type site at Saksunarvatn as well as from Potremser Moor. The Saksunarvatn Ash is indistinguishable between Potremser Moor and Saksunarvatn, suggesting the two tephras were produced by the same eruption. Trace element compositions from both sites are similar to data from the North Atlantic marine core (LINK 14:185), but different from the GRIP ice core (GRIP 1528.61 m), indicating that the south-east and north- west plumes may have arisen from separate eruption events. Copyright # 2013 John Wiley & Sons, Ltd.

The Holocene sediment record of Lake Tiefer See exhibits striking alternations between well-varved and non-varved intervals. Here, we present a high-resolution multi-proxy record for the past ~6000 years and discuss possible causes for the observed sediment variability. This approach comprises microfacies, geochemical and microfossil analyses and a multiple dating concept including varve counting, tephrochronology and radiocarbon dating. Four periods of predominantly well-varved sediment were identified at 6000–3950, 3100–2850 and 2100–750 cal. a BP and AD 1924–present. Except of sub- recent varve formation, these periods are considered to reflect reduced lake circulation and consequently, stronger anoxic bottom water conditions. In contrast, intercalated intervals of poor varve preservation or even extensively mixed non-varved sediments indicate strengthened lake circulation. Sub-recent varve formation since AD 1924 is, in addition to natural forcing, influenced by enhanced lake productivity due to modern anthropogenic eutrophication. The general increase in periods of intensified lake circulation in Lake Tiefer See since ~4000 cal. a BP presumably is caused by gradual changes in the northern hemisphere orbital forcing, leading to cooler and windier conditions in Central Europe. Superimposed decadal- to centennial- scale variability of the lake circulation regime is likely the result of additional human-induced changes of the catchment vegetation. The coincidence of major non-varved periods at Lake Tiefer See and intervals of bioturbated sediments in the Baltic Sea implies a broader regional significance of our findings.

We studied pollen–vegetation relationships along an altitudinal transect in the Caspian (Hyrcanian) forests of northern Iran. We collected surface samples from 20 plots of 400 or 625 m 2 in the major forest communities and compared pollen percentages of the most abundant plant taxa with the vegetation abundances (cover and basal areas) in the pollen plots and in areas of different radii (100, 250, 500 and 1000 m) around the pollen plots using both linear regression and qualitative methods. The results show that anemophilous taxa (i.e. Quercus , Fagus , and Carpinus ) in general produce more pollen relative to entomophilous taxa (i.e. Acer , Parrotia , Diospyros , and Hedera ). Taxa with light pollen grains, such as Quercus and Carpinus , show large positive intercepts in linear regression analysis, while heavier pollen grains or those possessing a patterned exine, such as Diospyros , Parrotia , Acer , and Hedera show small or even negative intercepts. Larger intercepts indicate that a higher proportion of pollen in the samples arrives from outside the area covered by the vegetation analysis. Our findings indicate that light pollen grains are deposited more slowly than heavy pollen grains. Dissimilarity matrices using the Bray–Curtis index showed that the overall relationship between species composition of vegetation plots and pollen assemblages is better for the areas with 100 m radius than for the pollen plots.

Alnus glutinosa-dominated peatlands are widespread in central Europe, but the generally bad preservation of micro- and macrofossils has hampered palaeoecological research of their peats. Because of its large carbon sequestration rate, however, peat accumulation in forested peatlands is of special interest for climate change research. This study identifies indicator groups for various types of alder (A. glutinosa) carr and sedge (Carex) fen vegetation, elaborated by analysis of non-pollen palynomorphs (NPPs) from peat and surface samples. The indicator value of fungal spores and decomposition products of wood was tested by correlation with pollen (especially alnus ) and macrofossils. Only few indicators of alder carr also occurred with low and constant values during distinct open sedge fen phases, which indicates that small and plane shaped NPPs can be dispersed extra-locally. The diversity and abundance of NPPs appeared to depend on vegetation type and resulting nutrient supply and to water regime and resulting decomposition intensity during peat development.

Past plant abundance may be reconstructed from pollen data if dispersal distances of pollen and pollen productivities of each taxon are known. Using surface sediment samples from small and medium sized, closed and near circular lakes from lowland Central Europe, we tested the validity of three pollen dispersal models by comparing empirical pollen data from each lake with simulated pollen data derived from applying various pollen dispersal models to vegetation data from rings situated up to 100 km from each site. Pollen assemblages simulated with a Lagrangian stochastic (LS) model best fit real pollen assemblages, simulations with the commonly used Prentice model on pollen dispersal underestimated the amount of pollen arriving from distances larger than 10 km and overestimated the differences in dispersal distances between lighter ( Pinus) and heavier ( Fagus, Picea) pollen grains. The LS model appeared to provide more appropriate simulations. Pollen productivity estimates (PPEs) calculated for the data set showed that the choice of the dispersal model has great impact on the results. If derived with the Prentice model, PPEs for Fagus and Picea are three times higher than with the LS model. Studies on pollen productivities thus need to consider the apparent limitations of the Prentice model. We suggest an alternative approach, which uses simulations instead of the extended R-value model, to calculate PPEs. The approach is flexible in the use of dispersal functions and produced consistent results for two independent data sets from small and medium sized lakes.

By applying the recently developed model REVEALS (Regional Estimates of VEgetation Abundance from Large Sites) ( Sugita, 2007 ) to pollen data from a large number of sites across Northern Germany and Denmark, we construct maps of regional patterns in landscape openness and in cover abundance of key plant taxa in the cultural landscape of north-central Europe for selected time slices in the Holocene. The results indicate that the pattern of landscape openness across the regions of northern Germany and Denmark prior to the introduction of agriculture was affected by soil conditions and degree of continentality. The 8.2 ka climate event did not lead to a general decrease in tree cover, although some changes in species composition were observed. The early phases of agriculture also had little effect on landscape openness at the regional scale, but later human impact lead to large scale deforestation and development of arable areas, grasslands and of heathlands in the north-western part of the region. The timing and degree of deforestation, and the weight between arable and grazing areas varied in space, partly due to differences in natural conditions, partly due to differences in cultural impact.

In the north Atlantic region the final period of the last ice age saw abrupt shifts between near present-day warm and near ice age cold conditions, ending with the cold Younger Dryas. The effects of the cold periods may have been more severe in the vicinity of the Atlantic Ocean than in continental Europe. We use pollen percentage and influx data combined with data on substrate and relief to reconstruct spatially explicit vegetation composition, patterns and development during the Younger Dryas, with special focus on to the forest/non-forest transition across NE Germany. Opposing trends, such as birch pollen percentages sharply increasing but accumulation rates sharply decreasing northwards, underline pitfalls in the interpretation of pollen percentage data in tree-line situations. The combined approach reveals a sharp ecotone. Pine declined on northern sites, possibly because of permafrost formation, but was hardly affected in the south. Birch also declined in the south, possibly because of the severe winter cold. Cold-adapted trees did not enter forest gaps. The cooling had little impact on herbal vegetation. Steppe elements (grasses, Artemisia) were largely restricted to south-exposed slopes and did not benefit from the cooling – patches of steppe vegetation were even less abundant than during the preceding warm periods. The approach of combining fossil pollen data, including accumulation rates, with data on the contemporary distribution of substrate and relief allowed unprecedented spatial resolution to be reached in the reconstruction of Younger Dryas vegetation patterns.

Aim Palynology has revealed that during the Lateglacial Allerod period, Pinus and Betula dominated the forests of north-east Germany. Because of implicit restrictions, however, palynology fails to reconstruct in detail the distributional patterns and whether monospecific or mixed forests prevailed. Here we test the hypothesis that the distributional patterns of Pinus and Betula were largely determined by substrate. Location Fifteen sites in north-east Germany. Methods As pollen data reflect the abundance of taxa around a sample site, our hypothesis implies that the abundance of e.g. Pinus pollen should reflect the abundance of substrate types that are favoured by Pinus. (In order to differentiate clearly between taxa and pollen types, the latter are displayed in small capitals.) We analysed the percentage of Pinus and Betula pollen from an interval in the Allerod, and their relationship to the present-day proportion of the two dominant substrate types (sand and boulder clay). The substrate proportion was determined in rings from 1 to 50 km around all sites, using four distance-weighting functions. Results Pollen percentages of Pinus are linearly related to the proportion of sand, and Betula percentages to the proportion of boulder clay. The highest coefficients of determination (r2 = 0.89 and 0.91, respectively) were observed for radii of c. 30 km, with distance weighting by 1 and 1/d. Main conclusions The present-day distributional pattern of substrate types strongly indicates the distributional pattern of Pinus and Betula in north-east Germany in the Allerod. Assuming that the pattern of substrates remained broadly constant, Pinus dominated on sand and Betula on boulder clay. Our new method thus enables us to refine significantly the reconstruction of habitat characteristics and distributional patterns of taxa in the Lateglacial and Holocene, independent of their present-day ecological amplitudes. The good performance of the distance-weighting functions 1 and 1/d indicates that the pollen source area of a site has rather discrete boundaries determined by convective air movements during daytime. Within these boundaries, pollen is evenly distributed over various distances. This implies that light pollen types are transported further than predicted by Sutton’s equation on particle dispersal.

Fine-scaled distribution patterns of vegetation and palynomorphs in a polygon mire in NE Siberia were studied in 31 × 31 plots of 1 m2 (vegetation) and along a transect at intervals of 1 m (palynomorphs). Pollen and non-pollen-palynomorph contents clearly reflect differences between polygon ridges and centres. For most single pollen types, however, no unambiguous relation with actual plant abundances and distribution exists. High pollen values are restricted to the immediate vicinity of the pollen sources, which is attributed to the low height of the vegetation. For several plant taxa, high pollen values were found to be restricted to particular plant specimens in the population. High values of pollen ascribed to taxa currently absent at the relevant plot show that the sampled mosses contain a pollen signal of several years. Betula exilis produces two morphologically clearly distinct pollen types. The distribution of selected non-pollen palynomorphs correlates to microrelief, moisture regime and/or trophic conditions. The study shows that single palaeo-sections from arctic peatlands should not be over-interpreted with respect to their palaeoecological value. Local vegetation types and site conditions, however, can be accurately reconstructed from the total assemblages and from combined occurrences of specific palynomorph types.

In order to investigate the environmental impacts of the Laacher See eruption (12,900 calendar years B.P.) and the deposition of the Laacher See tephra at a large distance from the volcano, fine-resolution micromorphological, diatomological, and palynological investigations were carried out on closely spaced areas in the Reinberg basin (Vorpommern, NE Germany). The lower part of the LST originates from atmospheric input, whereas the upper part was washed-in from the surrounding basin slopes. Diatom populations expanded as a consequence of the input of silica, while simultaneously dissolution of dead diatoms decreased. The tephra provided a favourable habitat for many epilithic and epipelic diatom taxa. The diatoms show a slight acidification and an increase in specific conductivity of the water, whereas no eutrophication is indicated. These effects disappeared after lake sediments covered the tephra. The pollen diagrams from the Reinberg basin as well as many other pollen diagrams from NE Germany indicate that the vegetation reacted to rising temperatures after the cooler Gerzensee fluctuation, to a short-lived water-level rise connected with higher precipitation after the volcanic eruption, and to minor openings in the forest vegetation due to increased fire probably connected with severe thunderstorms.

Alder ( Alnus ) carr peats have only rarely been subject of palaeoecological research because their mostly bad preservation prevents successful reconstruction of local and regional vegetation development by means of macrofossil and pollen analysis. To test the potential of non-pollen palynomorphs as an additional source of information, surface samples from five different types of substrates and three different Alder forest types were analysed on microfossils with special focus on non-pollen palynomorphs (NPPs). Forty-six new types of NPPs, mostly fungal spores and remains of decomposed wood, were described and illustrated. Ordination of the more common NPPs revealed a good differentiation between substrate groups and — to a lesser extent — site types. Comparison with microfossil data from Alder carr peat showed that the ecological information derived from the modern samples is consistent with the environmental conditions reconstructed from palaeoecological data (pollen, macrofossils, degree of decomposition) from the peat core. The analysis of NPPs in surface samples is a promising tool to assess the indicator value of NPPs, allowing an improved interpretation of fossil data. The fact that 2.6 times more NPP types than pollen types were found in the fossil samples illustrates the importance and potential of NPPs for palaeo-palynological research.

Pollen productivity is a key parameter to quantify past plant abundances and vegetation openness. In this study we explore how changes in land management influence pollen productivity. We study pollen deposition in largely annually laminated sediments from Lake Tiefer See in the Northeastern German lowlands deposited between AD 1880 and 2010. During this period, land use intensity has increased predominantly through the widespread introduction of artificial fertilizers, herbicides and heavy machinery mainly since the 1950s. Although land use statistics show that overall vegetation openness remained largely constant, non-arboreal pollen deposition (from herbs and grasses) sharply declined over the study period. This decline can be partly explained by a shift towards crops that emit little pollen such as wheat and oilseed rape. Furthermore, intensified grassland management, including drainage, also contributed to lower pollen deposition because of the decline of Plantago lanceolata and Rumex from grassland communities. However, the most important effect is a decline in pollen productivity of grasses of about 60%, which most likely is a response to earlier and more frequent mowing, although changes in grass species composition may also have played a role. Our results show that the type and intensity of land use have a strong effect on pollen productivity of grasses (and smaller effects on further crops). Since grass pollen deposition is a main proxy for vegetation openness and grasses are the common reference taxon in most PPE studies, variations in the pollen productivity of grasses introduce so far neglected errors in the reconstruction of the past vegetation cover. Our study provides a first estimate about the magnitude of this effect.

A multidisciplinary study was carried out at Lake Groser Furstenseer See (LFS) in order to explore the potential of littoral sediments, palaeosols and landforms as indicators of historical lake-level changes. This research was initiated to investigate the extent to which lakes in northern central Europe responded hydrologically to climatic and land-use changes in the last millennium. Specific landforms investigated comprise lake terraces, beach ridges, local basins/peatlands and dunes, revealing a wealth of sedimentary sub-environments at the lakeshore. Eleven sections were recorded with subsequent sedimentological–pedological, geochronological (OSL, 14C) and palaeobotanical (pollen, macro remains) analyses. Most of the pedosedimentary littoral sequences show a succession of basal glacial sand, intermediate palaeosols and lacustrine sand on top. A broader number of (semi-)terrestrial buried palaeosols along the lakeshore were systematically identified and analysed, providing evidence for changing hydrological conditions during the late Holocene. Additional historical data from the last centuries (e.g. maps, aerial photos, public records) allow the lake-levels reconstructed from geoarchives to be connected with modern gauging data. All local data sources available enable a tracing of lake level changes of the LFS during the last millennium, comprising periods of relatively low (c. 1200 AD, 2000s AD) and relatively high water levels (c. 1250–1450 AD, c. 1780 AD, 1980s AD). The amplitude of lake-level changes during the last c. 1000 years amounts to c. 3 m, so that the fluctuations of the last 30 years recorded by lake-level monitoring only reflect a small amount of the potential variability. Regional climate and local land-use history suggest that the Medieval lake-level dynamics of LFS were primarily governed by climate and secondarily influenced by human impact on the drainage system. At present the lake level is additionally influenced by the impact of highly water-consuming pine plantations in the catchment area. The regional significance of the local development at LFS can be demonstrated by comparison with other regional and supra-regional lake-level data. The present study underlines the potential of a closer examination of the littoral zone for lake-level reconstructions with high altitudinal precision.

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.

Unfortunately, the list of authors contains a number of duplications, omissions and other errors in the original publication of the article. The correct list appears in this erratum.

A new site with Lateglacial palaeosols covered by 0.8 - 2.4 m thick aeolian sands is presented. The buried soils were subjected to multidisciplinary analyses (pedology, micromorphology, geochronology, dendrology, palynology, macrofossils). The buried soil cover comprises a catena from relatively dry (’Nano’-Podzol, Arenosol) via moist (Histic Gleysol, Gleysol) to wet conditions (Histosol). Dry soils are similar to the so-called Usselo soil, as described from sites in NW Europe and central Poland. The buried soil surface covers ca. 3.4 km2. Pollen analyses date this surface into the late Allerød. Due to a possible contamination by younger carbon, radiocarbon dates are too young. OSL dates indicate that the covering by aeolian sands most probably occurred during the Younger Dryas. Botanical analyses enables the reconstruction of a vegetation pattern typical for the late Allerød. Large wooden remains of pine and birch were recorded.