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1.
  • Bakumenko, Varvara, et al. (författare)
  • Chironomidae-based inference model for mean July air temperature reconstructions in the eastern Baltic area
  • 2024
  • Ingår i: Boreas. - 0300-9483.
  • Tidskriftsartikel (refereegranskat)abstract
    • Here we present a new eastern Baltic Chironomidae training set (TS) containing 35 sites that was collected and merged with neighbouring published Finnish (82 lakes) and northern part of the Polish (nine lakes) TSs. Chironomidae, non-biting midges, are known to be strongly responsive to the July air temperature and are widely used to infer palaeotemperature. Several modern analogue-based TSs necessary for calibrating the relationships between mean July air temperature (MJAT) and chironomids are available for Europe. However, none of these is representative of the transitional climate typical for eastern Baltic (Estonia, Latvia, Lithuania). The Finno–Baltic–Polish TS contains 121 sites and covers a geographically continuous 70–50°N latitudinal and 7 °C (12.1–19.2 °C) MJAT gradient. Canonical correspondence analysis revealed that, among the tested environmental variables (pH, water depth, dissolved oxygen, MJAT), the MJAT explains the highest amount of variation, both for the eastern Baltic separately and the Finno–Baltic–Polish TSs. The weighted averaging–partial least squares-based cross-validation test reveals that the Finno–Baltic–Polish TS has a low root mean square error of prediction (0.7 °C) confirming the high reliability of the TS. The temperature optima of the taxa included in the new Finno–Baltic–Polish TS and widely used Swiss–Norwegian TS were examined. The observed dissimilarities can be attributed to the differences in the temperature ranges represented by the TS, the taxonomic identification level, the general cosmopolitan taxa distribution patterns and the influence of TS-specific geographic position, climatic or environmental conditions. The new Finno–Baltic–Polish TS adds to the knowledge on the modern distribution of Chironomidae taxa and widens the geographical area of reliable Chironomid-based MJAT reconstructions into the eastern European lowland.
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2.
  • Broström, Anna, et al. (författare)
  • Pollen productivity estimates of key European plant taxa for quantitative reconstruction of past vegetation : a review
  • 2008
  • Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 17:5, s. 461-478
  • Tidskriftsartikel (refereegranskat)abstract
    • Information on the spatial distribution of past vegetation on local, regional and global scales is increasingly used within climate modelling, nature conservancy and archaeology. It is possible to obtain such information from fossil pollen records in lakes and bogs using the landscape reconstruction algorithm (LRA) and its two models, REVEALS and LOVE. These models assume that reliable pollen productivity estimates (PPEs) are available for the plant taxa involved in the quantitative reconstructions of past vegetation, and that PPEs are constant through time. This paper presents and discusses the PPEs for 15 tree and 18 herb taxa obtained in nine study areas of Europe. Observed differences in PPEs between regions may be explained by methodological issues and environmental variables, of which climate and related factors such as reproduction strategies and growth forms appear to be the most important. An evaluation of the PPEs at hand so far suggests that they can be used in modelling applications and quantitative reconstructions of past vegetation, provided that consideration of past environmental variability within the region is used to inform selection of PPEs, and bearing in mind that PPEs might have changed through time as a response to climate change. Application of a range of possible PPEs will allow a better evaluation of the results.
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3.
  • Dallmeyer, Anne, et al. (författare)
  • Holocene forest-cover changes in Europe - a comparison of dynamic vegetation model results and pollen-based REVEALS reconstructions
  • 2023
  • Ingår i: EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11206. - : European Geosciences Union (EGU).
  • Konferensbidrag (refereegranskat)abstract
    • We compare Holocene forest-cover changes in Europe derived from a transient MPI-ESM1.2 simulation with high spatial resolution time-slice simulations conducted in LPJ-GUESS and pollen-based quantitative reconstructions of forest cover based on the REVEALS model (pol-RVs). The dynamic vegetation models and pol-RVs agree with respect to the general temporal trends in forest cover for most parts of Europe, with a large forest cover during the mid-Holocene and substantially smaller forest cover closer to the present time. However, the age of the start of decrease in forest cover varies between regions, and is much older in the pol-RVs than in the models. The pol-RVs suggest much earlier anthropogenic deforestation than the prescribed land-use in the models starting 2000 years ago. While LPJ-GUESS generally overestimates forest cover compared to pol-RVs, MPI-ESM indicates lower percentages of forest cover than pol-RVs, particularly in Central Europe. A comparison of the simulated climate with chironomid-based climate reconstructions reveal that model-data mismatches in forest cover are in most cases not driven by biases in the climate. Instead, sensitivity experiments show that the model results strongly depend on the models tuning regarding natural disturbance regimes (e.g. fire and wind throw). The frequency and strength of disturbances are – like most of the parameters in the vegetation models – static and calibrated to modern conditions. However, these parameter values may not be valid during climate and vegetation states totally different from today’s. In particular, the mid-Holocene natural forests were probably more stable and less sensitive to disturbances than present day forests that are heavily altered by human interventions. Our analysis highlights the fact that such model settings are inappropriate for paleo-simulations and complicate model-data comparisons with additional challenges. Moreover, our study suggests that land-use is the main driver of forest decline in Europe during the mid- and late-Holocene.
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4.
  • Dallmeyer, Anne, et al. (författare)
  • The challenge of comparing pollen-based quantitative vegetation reconstructions with outputs from vegetation models - a European perspective
  • 2023
  • Ingår i: Climate of the Past. - : Copernicus Publications. - 1814-9324 .- 1814-9332. ; 19:7, s. 1531-1557
  • Tidskriftsartikel (refereegranskat)abstract
    • We compare Holocene tree cover changes in Europe derived from a transient Earth system model simulation (Max Planck Institute Earth System Model - MPI-ESM1.2, including the land surface and dynamic vegetation model JSBACH) with high-spatial-resolution time slice simulations performed in the dynamic vegetation model LPJ-GUESS (Lund-Potsdam-Jena General Ecosystem Simulator) and pollen-based quantitative reconstructions of tree cover based on the REVEALS (Regional Estimates of Vegetation Abundance from Large Sites) model. The dynamic vegetation models and REVEALS agree with respect to the general temporal trends in tree cover for most parts of Europe, with a large tree cover during the mid-Holocene and a substantially smaller tree cover closer to the present time. However, the decrease in tree cover in REVEALS starts much earlier than in the models, indicating much earlier anthropogenic deforestation than the prescribed land use in the models. While LPJ-GUESS generally overestimates tree cover compared to the reconstructions, MPI-ESM indicates lower percentages of tree cover than REVEALS, particularly in central Europe and the British Isles. A comparison of the simulated climate with chironomid-based climate reconstructions reveals that model-data mismatches in tree cover are in most cases not driven by biases in the climate. Instead, sensitivity experiments indicate that the model results strongly depend on the tuning of the models regarding natural disturbance regimes (e.g. fire and wind throw). The frequency and strength of disturbances are - like most of the parameters in the vegetation models - static and calibrated to modern conditions. However, these parameter values may not be valid for past climate and vegetation states totally different from today's. In particular, the mid-Holocene natural forests were probably more stable and less sensitive to disturbances than present-day forests that are heavily altered by human interventions. Our analysis highlights the fact that such model settings are inappropriate for paleo-simulations and complicate model-data comparisons with additional challenges. Moreover, our study suggests that land use is the main driver of forest decline in Europe during the mid-Holocene and late Holocene.
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5.
  • Edvardsson, Johannes, et al. (författare)
  • Late-Holocene expansion of a south Swedish peatland and its impact on marginal ecosystems: Evidence from dendrochronology, peat stratigraphy and palaeobotanical data
  • 2014
  • Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 24:4, s. 466-476
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, a reconstruction of the long-term development and lateral expansion of a south Swedish peat bog was performed using a multi-proxy approach, including dendrochronology, peat stratigraphy and macrofossil and pollen analyses. By combining mapping of cross-dated subfossil trees with radiocarbon-dated peat sequences, an improved approach to reconstruction of lateral peat expansion was applied. Apart from providing approximate ages of tree burial episodes, the ring-width records offer information on hydrological variations prior to the bog expansion. New bog oak, pine and alder chronologies are presented and their potential as a dating tool for peatland expansion as well as for local to regional environmental interpretations is examined. Our tree-replication records show that increased amounts of bog trees in the central parts can be linked to drier bog-surface conditions, whereas an increase in wood remains in the marginal zone is related to enhanced preservation due to lateral bog expansion. Our reconstructions of the development of the peat deposit and associated changes in the distribution of vegetation communities provide new insight into peatland responses to climate change at the end of the 'Holocene Thermal Maximum' (5000-4000 cal. yr BP).
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6.
  • Feurdean, Angelica, et al. (författare)
  • Fire hazard modulation by long-term dynamics in land cover and dominant forest type in eastern and central Europe
  • 2020
  • Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 17:5, s. 1213-1230
  • Tidskriftsartikel (refereegranskat)abstract
    • Wildfire occurrence is influenced by climate, vegetation and human activities. A key challenge for understanding the risk of fires is quantifying the mediating effect of vegetation on fire regimes. Here, we explore the relative importance of Holocene land cover, land use, dominant functional forest type, and climate dynamics on biomass burning in temperate and boreo-nemoral regions of central and eastern Europe over the past 12 kyr. We used an extensive data set of Holocene pollen and sedimentary charcoal records, in combination with climate simulations and statistical modelling. Biomass burning was highest during the early Holocene and lowest during the mid-Holocene in all three ecoregions (Atlantic, continental and boreo-nemoral) but was more spatially variable over the past 3-4 kyr. Although climate explained a significant variance in biomass burning during the early Holocene, tree cover was consistently the highest predictor of past biomass burning over the past 8 kyr. In temperate forests, biomass burning was high at ∼ 45% tree cover and decreased to a minimum at between 60% and 70% tree cover. In needleleaf-dominated forests, biomass burning was highest at ∼60 %-65%tree cover and steeply declined at > 65% tree cover. Biomass burning also increased when arable lands and grasslands reached ∼15 %-20 %, although this relationship was variable depending on land use practice via ignition sources, fuel type and quantities. Higher tree cover reduced the amount of solar radiation reaching the forest floor and could provide moister, more wind-protected microclimates underneath canopies, thereby decreasing fuel flammability. Tree cover at which biomass burning increased appears to be driven by warmer and drier summer conditions during the early Holocene and by increasing human influence on land cover during the late Holocene. We suggest that longterm fire hazard may be effectively reduced through land cover management, given that land cover has controlled fire regimes under the dynamic climates of the Holocene.
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8.
  • Gaillard, Marie-José, et al. (författare)
  • Causes of Regional Change : Land Cover
  • 2015
  • Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160054 - 9783319160061 ; , s. 453-477
  • Bokkapitel (refereegranskat)abstract
    • Anthropogenic land-cover change (ALCC) is one of the few climate forcings for which the net direction of the climate response over the last two centuries is still not known. The uncertainty is due to the often counteracting temperature responses to the many biogeophysical effects and to the biogeochemical versus biogeophysical effects. Palaeoecological studies show that the major transformation of the landscape by anthropogenic activities in the southern zone of the Baltic Sea basin occurred between 6000 and 3000/2500 cal year BP. The only modelling study of the biogeophysical effects of past ALCCs on regional climate in north-western Europe suggests that deforestation between 6000 and 200 cal year BP may have caused significant change in winter and summer temperature. There is no indication that deforestation in the Baltic Sea area since AD 1850 would have been a major cause of the recent climate warming in the region through a positive biogeochemical feedback. Several model studies suggest that boreal reforestation might not be an effective climate warming mitigation tool as it might lead to increased warming through biogeophysical processes.
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9.
  • Gaillard, Marie-José, et al. (författare)
  • From land cover-climate relationships at the subcontinental scale to land cover-environment relationships at the regional and local spatial scale – the contribution of pollen-based quantitative reconstructions of vegetation cover using the Landscape Reconstruction Algorithm approach
  • 2014
  • Ingår i: Towards a more accurate quantification of human-environment interactions in the past. ; , s. 25-26
  • Konferensbidrag (refereegranskat)abstract
    • The Landscape Reconstruction Algorithm (Sugita 2007a,b) includes two models, REVEALS (Regional Estimates of VEgetation Abundance from Large Sites) that estimates vegetation abundance (% cover) within an area of ca. 100 km x 100 km, and LOVE (LOcal Vegetation Estimates) that estimates vegetation abundance at the local spatial scale, i.e. within the Relevant Source Area of Pollen (RSAP sensu Sugita, 2004) that is the smallest area around the study site for which the reconstruction is valid. The RSAP is estimated by the LOVE model and varies between sites and vegetation settings; so far, it was estimated to vary between < 1 - < 10 km in most ecological settings of the Holocene in NW Europe. We used the REVEALS model and over 600 pollen records from pollen data bases and individual researchers to reconstruct land-cover in NW Europe N of the Alps for key time windows of the Holocene in order to assess model-based reconstructions of anthropogenic land-cover change (ALCC) (e.g. Kaplan et al., 2009) and model (LPJ-GUESS) simulations of past potential (climate-induced vegetation), and to study past land cover – climate interactions using a regional climate model (RCA3). We used the REVEALS model and the complete LRA approach (REVEALS + LOVE models) along with two pollen records from large lakes and three pollen records from small bogs to reconstruct the local-scale land-cover in central Småland, southern Sweden, to study the relationship between vegetation composition, fire, climate and human impact at the regional and local spatial scales with the objective to discuss biodiversity issues. Our results suggest that i) past subcontinental to regional ALCC did influence regional climate through biogeophysical processes at the landatmosphere interface (Strandberg et al., submitted), and ii) local land-cover change, both natural and anthropogenic, govern environmental changes such as fire and biodiversity (Cui et al., 2013; Cui et al., submitted).
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10.
  • Gaillard, Marie-José, et al. (författare)
  • Has anthropogenic land-cover change been a significant climate forcing in the past? : An assessment for the Baltic Sea catchment area based on a literature review
  • 2015
  • Ingår i: Geophysical Research Abstracts.
  • Konferensbidrag (refereegranskat)abstract
    • We reviewed the recent published scientific literature on land cover-climate interactions at the global and regional spatial scales with the aim to assess whether it is convincingly demonstrated that anthropogenic land-cover change (ALCC) has been (over the last centuries and millennia) a significant climate forcing at the global scale, and more specifically at the scale of the Baltic Sea catchment area. The conclusions from this review are as follows: i) anthropogenic land-cover change (ALCC) is one of the few climate forcings for which the net direction of the climate response in the past is still not known. The uncertainty is due to the often counteracting temperature responses to the many biogeophysical effects, and to the biogeochemical vs biogeophysical effects; ii) there is no indication that deforestation in the Baltic Sea area since AD 1850 would have been a major cause of the recent climate warming in the region through a positive biogeochemical feedback; iii) several model studies suggest that boreal reforestation might not be an effective climate warming mitigation tool as it might lead to increased warming through biogeophysical processes; iv) palaeoecological studies indicate a major transformation of the landscape by anthropogenic activities in the southern zone of the study region occurring between 6000 and 3000/2500 calendar years before present (cal. BP) (1) ; v) the only modelling study so far of the biogeophysical effects of past ALCCs on regional climate in Europe suggests that a deforestation of the magnitude of that reconstructed for the past (between 6000 and 200 cal BP) can produce changes in winter and summer temperatures of +/- 1, the sign of the change depending on the season and the region (2). Thus, if ALCC and their biogeophysical effects did matter in the past, they should matter today and in the future. A still prevailing idea is that planting trees will mitigate climate warming through biogeochemical effects. Therefore, there is still an urgent need to better understand the biogeophysical effects on regional and continental climate of afforestation in the hemiboreal and boreal regions, and their significance in relation to the biogeochemical effects.
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11.
  • Gaillard, Marie-José, 1953-, et al. (författare)
  • Holocene land-cover reconstructions for studies on land cover-climate feedbacks
  • 2010
  • Ingår i: Climate of the Past. - : Copernicus GmbH. - 1814-9324 .- 1814-9332. ; 6, s. 483-499
  • Tidskriftsartikel (refereegranskat)abstract
    • The major objectives of this paper are: (1) to review the pros and cons of the scenarios of past anthropogenic land cover change (ALCC) developed during the last ten years, (2) to discuss issues related to pollen-based reconstruction of the past land-cover and introduce a new method, REVEALS (Regional Estimates of VEgetation Abundance from Large Sites), to infer long-term records of past land-cover from pollen data, (3) to present a new project (LANDCLIM: LAND cover – CLIMate interactions in NW Europe during the Holocene) currently underway, and show preliminary results of REVEALS reconstructions of the regional land-cover in the Czech Republic for five selected time windows of the Holocene, and (4) to discuss the implications and future directions in climate and vegetation/land-cover modeling, and in the assessment of the effects of human-induced changes in land-cover on the regional climate through altered feedbacks. The existing ALCC scenarios show large discrepancies between them, and few cover time periods older than AD 800. When these scenarios are used to assess the impact of human land-use on climate, contrasting results are obtained. It emphasizes the need for methods such as the REVEALS model-based land-cover reconstructions. They might help to fine-tune descriptions of past land-cover and lead to a better understanding of how long-term changes in ALCC might have influenced climate. The REVEALS model is demonstrated to provide better estimates of the regional vegetation/landcover changes than the traditional use of pollen percentages. This will achieve a robust assessment of land cover at regional- to continental-spatial scale throughout the Holocene. We present maps of REVEALS estimates for the percentage cover of 10 plant functional types (PFTs) at 200 BP and 6000 BP, and of the two open-land PFTs “grassland” and “agricultural land” at five time-windows from 6000 BP to recent time. The LANDCLIM results are expected to provide crucial data to reassess ALCC estimates for a better understanding of the land suface-atmosphere interactions.
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12.
  • Gaillard, Marie-José, 1953-, et al. (författare)
  • Land cover-climate interactions in the past for the understanding of current and future climate change : the LANDCLIM project
  • 2014
  • Ingår i: Proceedings of the Global Land Project 2nd Open Science Meeting, Berlin,<em> </em>March 19<sup>th</sup> – 21<sup>st</sup>, 2014. - Amsterdam/Berlin/Sao Paulo : Global Land Project. ; , s. 229-230
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • The LANDCLIM (LAND cover – CLIMate interactions in NW Europe during the Holocene) project has the overall aim to quantify human-induced changes in regional vegetation/land-cover in northwestern and western Europe North of the Alps during the Holocene (the last 11 500 years) with the purpose to evaluate and further refine the dynamic vegetation model LPJGUESS and the regional climate model RCA3, and to assess the possible effects on the climate development of two historical processes, i.e. climate-driven changes in vegetation and human-induced changes in land cover, via the influence of forested versus non-forested land cover on shortwave albedo, energy and water fluxes. Accounting for land surface changes may be particularly important for regional climate modeling, as the biophysical feedbacks operate at this scale. The aims of the LANDCLIM project are achieved by applying a model-data comparison scheme. The REVEALS model is used to estimate land cover from pollen data for 10 plant functional types (PFTs) and 5 time windows of the Holocene - modern time, 200 BP, 500 BP, 3000 BP and 6000 BP. The REVEALS estimates are then compared to the LPJGUESS simulations of potential vegetation and with the ALCC scenarios of Kaplan et al. (KK10) and Klein-Goldewijk et al. (HYDE). The alternative descriptions of past land-cover are then used in the regional climate model RCA3 to study the effect of anthropogenic land-cover on climate. The model-simulated climate is finally compared to palaeoclimate proxies other than pollen. The REVEALS estimates demonstrate that the study region was characterized by larger areas of human-induced openland than pollen percentages suggest, and that these areas were already very large by 3000 BP. The KK10 scenarios were found to be closer to the REVEALS estimates than the HYDE scenarios. LPJGUESS simulates potential climate-induced vegetation. The results from the RCA3 runs at 200 BP and 6000 BP using the LPJGUESS and KK10 land-cover descriptions indicate that past human-induced deforestation did produce a decrease in summer temperatures of >0 - 1.5°C due to biogeophysical processes, and that the degree of decrease differed between regions; the effect of human-induced deforestation on winter temperatures was shown to be more complex. The positive property of forests as CO2 sinks is well known. But afforestation (i.e. planting forest) may also have the opposite effect of warming the climate through biogeophysical processes. Careful studies on land cover-climate interactions are essential to understand the net result of all possible processes related to anthropogenic land-cover change so that relevant landscape management can be implemented for mitigation of climate warming.
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13.
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14.
  • Gaillard, Marie-Jose, et al. (författare)
  • The use of modelling and simulation approach in reconstructing past landscapes from fossil pollen data: a review and results from the POLLANDCAL network
  • 2008
  • Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 17:5, s. 419-443
  • Tidskriftsartikel (refereegranskat)abstract
    • Information on past land cover in terms of absolute areas of different landscape units (forest, open land, pasture land, cultivated land, etc.) at local to regional scales is needed to test hypotheses and answer questions related to climate change (e.g. feedbacks effects of land-cover change), archaeological research, and nature conservancy (e.g. management strategy). The palaeoecological technique best suited to achieve quantitative reconstruction of past vegetation is pollen analysis. A simulation approach developed by Sugita (the computer model POLLSCAPE) which uses models based on the theory of pollen analysis is presented together with examples of application. POLLSCAPE has been adopted as the central tool for POLLANDCAL (POLlen/LANdscape CALibration), an international research network focusing on this topic. The theory behind models of the pollen-vegetation relationship and POLLSCAPE is reviewed. The two model outputs which receive greatest attention in this paper are the relevant source area of pollen (RSAP) and pollen loading in mires and lakes. Six examples of application of POLLSCAPE are presented, each of which explores a possible use of the POLLANDCAL tools and a means of validating or evaluating the models with empirical data. The landscape and vegetation factors influencing the size of the RSAP, the importance of pollen productivity estimates (PPEs) for the model outputs, the detection of small and rare patches of plant taxa in pollen records, and quantitative reconstructions of past vegetation and landscapes are discussed on the basis of these examples. The simulation approach is seen to be useful both for exploring different vegetation/landscape scenarios and for refuting hypotheses.
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16.
  • Githumbi, Esther, et al. (författare)
  • European pollen-based REVEALS land-cover reconstructions for the Holocene : Methodology, mapping and potentials
  • 2022
  • Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3508 .- 1866-3516. ; 14:4, s. 1581-1619
  • Tidskriftsartikel (refereegranskat)abstract
    • Quantitative reconstructions of past land cover are necessary to determine the processes involved in climate-human-land-cover interactions. We present the first temporally continuous and most spatially extensive pollen-based land-cover reconstruction for Europe over the Holocene (last 11g€¯700g€¯calg€¯yrg€¯BP). We describe how vegetation cover has been quantified from pollen records at a 11 spatial scale using the "Regional Estimates of VEgetation Abundance from Large Sites"(REVEALS) model. REVEALS calculates estimates of past regional vegetation cover in proportions or percentages. REVEALS has been applied to 1128 pollen records across Europe and part of the eastern Mediterranean-Black Sea-Caspian corridor (30-75° N, 25° W-50° E) to reconstruct the percentage cover of 31 plant taxa assigned to 12 plant functional types (PFTs) and 3 land-cover types (LCTs). A new synthesis of relative pollen productivities (RPPs) for European plant taxa was performed for this reconstruction. It includes multiple RPP values (≥2 values) for 39 taxa and single values for 15 taxa (total of 54 taxa). To illustrate this, we present distribution maps for five taxa (Calluna vulgaris, Cerealia type (t)., Picea abies, deciduous Quercus t. and evergreen Quercus t.) and three land-cover types (open land, OL; evergreen trees, ETs; and summer-green trees, STs) for eight selected time windows. The reliability of the REVEALS reconstructions and issues related to the interpretation of the results in terms of landscape openness and human-induced vegetation change are discussed. This is followed by a review of the current use of this reconstruction and its future potential utility and development. REVEALS data quality are primarily determined by pollen count data (pollen count and sample, pollen identification, and chronology) and site type and number (lake or bog, large or small, one site vs. multiple sites) used for REVEALS analysis (for each grid cell). A large number of sites with high-quality pollen count data will produce more reliable land-cover estimates with lower standard errors compared to a low number of sites with lower-quality pollen count data. The REVEALS data presented here can be downloaded from https://doi.org/10.1594/PANGAEA.937075 (Fyfe et al., 2022).
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17.
  • Githumbi, Esther, et al. (författare)
  • Holocene quantitative pollen-based vegetation reconstructions in Europe for climate modelling: LandClim II
  • 2019
  • Konferensbidrag (refereegranskat)abstract
    • Understanding land use and land cover (LULC) change through time is an important aspect when attempting to interpret human-environment interactions through time. Palaeoenvironmental techniques have been crucial in bridging this gap by providing information that has been used to estimate climate change, vegetation change, sea level change etc. through time using a variety of proxies. Producing quantitative land-cover reconstructions has been an aim and a challenge with several methods attempted during the decades. In this project, we use the REVEALS model has been tested and validated in several regions of the world.We use REVEALS-based quantitative reconstructions of vegetation change to investigate the biogeochemical and biogeophysical forcings of land-cover change on climate. In the first phase of this project, LandClim I, quantitative vegetation reconstructions were produced for Europe (Mediterranean area excluded) focusing on five time windows of the Holocene between 6ka BP and present. The results from a regional climate model showed that the impact of the reconstructed LULC between 6 ka and 0.2 ka BP via biogeophysical forcing varied geographically and seasonally. We present the REVEALS quantitative pollen-based vegetation reconstruction from the ongoing second phase of the project LandClim II “Quantification of the biogeophysical and biogeochemical forcings from anthropogenic deforestation on regional Holocene climate in Europe”. This reconstruction covers entire Europe and is transient over the Holocene with a time resolution of 500 years between 11.2 and 0.7ka BP, and 100 to 300 years from 0.7ka BP to modern time.
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18.
  • Githumbi, Esther, et al. (författare)
  • Pollen-Based Maps of Past Regional Vegetation Cover in Europe Over 12 Millennia-Evaluation and Potential
  • 2022
  • Ingår i: Frontiers in Ecology and Evolution. - : Frontiers Media S.A.. - 2296-701X. ; 10
  • Tidskriftsartikel (refereegranskat)abstract
    • Realistic and accurate reconstructions of past vegetation cover are necessary to study past environmental changes. This is important since the effects of human land-use changes (e.g. agriculture, deforestation and afforestation/reforestation) on biodiversity and climate are still under debate. Over the last decade, development, validation, and application of pollen-vegetation relationship models have made it possible to estimate plant abundance from fossil pollen data at both local and regional scales. In particular, the REVEALS model has been applied to produce datasets of past regional plant cover at 1 degrees spatial resolution at large subcontinental scales (North America, Europe, and China). However, such reconstructions are spatially discontinuous due to the discrete and irregular geographical distribution of sites (lakes and peat bogs) from which fossil pollen records have been produced. Therefore, spatial statistical models have been developed to create continuous maps of past plant cover using the REVEALS-based land cover estimates. In this paper, we present the first continuous time series of spatially complete maps of past plant cover across Europe during the Holocene (25 time windows covering the period from 11.7 k BP to present). We use a spatial-statistical model for compositional data to interpolate REVEALS-based estimates of three major land-cover types (LCTs), i.e., evergreen trees, summer-green trees and open land (grasses, herbs and low shrubs); producing spatially complete maps of the past coverage of these three LCTs. The spatial model uses four auxiliary data sets-latitude, longitude, elevation, and independent scenarios of past anthropogenic land-cover change based on per-capita land-use estimates ("standard" KK10 scenarios)-to improve model performance for areas with complex topography or few observations. We evaluate the resulting reconstructions for selected time windows using present day maps from the European Forest Institute, cross validate, and compare the results with earlier pollen-based spatially-continuous estimates for five selected time windows, i.e., 100 BP-present, 350-100 BP, 700-350 BP, 3.2-2.7 k BP, and 6.2-5.7 k BP. The evaluations suggest that the statistical model provides robust spatial reconstructions. From the maps we observe the broad change in the land-cover of Europe from dominance of naturally open land and persisting remnants of continental ice in the Early Holocene to a high fraction of forest cover in the Mid Holocene, and anthropogenic deforestation in the Late Holocene. The temporal and spatial continuity is relevant for land-use, land-cover, and climate research.
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19.
  • Hensgens, Geert, et al. (författare)
  • High variability in the decay of dissolved organic carbon from different boreal litter sources; a challenge to land-water carbon flux modeling
  • 2016
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Dynamic ecosystem modelling offers potentially groundbreaking possibilities to reconstruct and project exports of Dissolved Organic Carbon (DOC) from land to surface water. However, the balance between production, degradation and export of soil DOC remains a challenge to model in boreal forests, partly because variability in soil DOC turnover is poorly understood. Here we determined the heterogeneity in decay potentials for DOC leached from main litter sources in boreal forest. We measured 48h leaching potentials (20°C in pure water) of fresh and pre-degraded leaf and wood litter, and subsequently performed short- and long-term standardized bioassays. Leaching and decay potentials of DOC varied more than tenfold between species. Broadleaf trees and shrubs generally showed highest magnitudes and variability in both DOC leaching and subsequent decay, compared to coniferous materials. However, it appears impossible to predict differences in decay potentials without considering both the physical structure and chemical composition of source materials. We suggest that a thorough inventory of soil DOC sources with regard to decay potentials is needed to adequately model the response in DOC export to changes in climate and vegetation.
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20.
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21.
  • Marquer, Laurent, et al. (författare)
  • Holocene changes in vegetation composition in northern Europe: why quantitative pollen-based vegetation reconstructions matter
  • 2014
  • Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 90, s. 199-216
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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22.
  • Marquer, Laurent, et al. (författare)
  • Quantifying the effects of land use and climate on Holocene vegetation in Europe
  • 2017
  • Ingår i: Quaternary Science Reviews. - : Pergamon Press. - 0277-3791 .- 1873-457X. ; 171, s. 20-37
  • Tidskriftsartikel (refereegranskat)abstract
    • 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.
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23.
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24.
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25.
  • Meltsov, Vivika, et al. (författare)
  • Palynological richness and pollen sample evenness in relation to local floristic diversity in southern Estonia
  • 2011
  • Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 166:3-4, s. 344-351
  • Tidskriftsartikel (refereegranskat)abstract
    • The relationship between palynological diversity and floristic diversity was studied on the basis of sediment surface sample pollen data from nine small lakes and vegetation data within a 250 m radius from the lake shore of each. The nine study areas are situated in the patchy cultural landscape of Southern Estonia and were chosen to represent landscape changes along a gradient from closed forest to open vegetation. Two diversity measures - richness and evenness - were used to compare the palynological and floristic data. A total of 307 plant species were recorded in the vegetation representing 127 pollen types. Only 52 pollen types were recorded in the sediment surface samples of which 43 had parent plants in the vegetation. Significantly lower floristic richness was found in closed surroundings than in more open surroundings. Study sites with open vegetation also had significantly higher palynological richness (number of pollen types recorded in surface sediments). The additional pollen types recorded in surface sediments from open vegetation were widespread types mostly of insect-pollinated taxa such as Ranunculus, Rubiaceae, Melampyrum, Filipendula, Potentilla or Vaccinium. The parent plants of these pollen types were frequent in the landscape. This suggests that the main mechanism governing palynological richness in this study was not floristic diversity but rather variance in pollen productivity. Since woodland has a higher pollen production than open areas (grassland and fields) per unit land surface, open areas tend to show a better representation of slightly rarer but widespread herb pollen types. No relationship was found between palynological and floristic diversity of wind-pollinated taxa and tree taxa partly because the pollen source area for these pollen types is much larger than 250 m. (C) 2011 Elsevier B.V. All rights reserved.
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26.
  • Meltsov, Vivika, et al. (författare)
  • The role of landscape structure in determining palynological and floristic richness
  • 2013
  • Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 22:1, s. 39-49
  • Tidskriftsartikel (refereegranskat)abstract
    • The associations between floristic and palynological richness and landscape structure were studied based on modern pollen-vegetation data from a patchy cultural landscape in southern Estonia (northern temperate vegetation zone). Nine study sites (small lakes and their surrounding vegetation) represent land cover gradient from closed forest to semi-open vegetation. Floristic richness (number of species) and floristic richness of pollen types (number of pollen-equivalent taxa) were used to describe the vegetation within the radius of 250 m from the pollen sampling sites. Palynological richness was calculated to describe the modern pollen samples diversity. Landscape structure was estimated on the basis of landscape openness and three landscape diversity measures: richness of community patches, Simpson evenness of community patches and Simpson diversity of community patches. To study the effect of the spatial scale of landscapes on the vegetation-landscape and pollen-landscape associations, landscape structure was estimated within eight radii (250-2,000 m) around each lake. The results showed that landscape openness was the most important determinant of both floristic richness and palynological richness in southern Estonia and that landscape diversity estimated by Simpson diversity index was also significantly associated with the richness estimates. Floristic and palynological richness were significantly positively correlated with landscape structure within the radii greater than 1,000 m from the pollen sampling sites, which is similar to the estimated Relevant Source Area of Pollen in southern Estonia. We conclude that within one floristic or climatic region, palynological richness gives reliable estimates about the variation in floristic richness and landscape structure; however, caution must be taken when comparing pollen-inferred vegetation diversities from different regions or when interpreting fossil pollen records from times with highly different vegetation associations.
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27.
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28.
  • Pidek, Irena Agnieszka, et al. (författare)
  • Pollen based quantitative climate reconstructions from the Middle Pleistocene sequences in Lukow and Zdany (E Poland): Species and modern analogues based approach
  • 2013
  • Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 192, s. 65-78
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the study was to estimate the range of climate variability during the Ferdynandovian climatostratigraphic unit (MIS 13-15). The studied pollen sequences encompass two interglacials (Ferdynandovian I and II - FI and F II), the glaciation separating them (FI/II), the late glacial of the Sanian I (= Elsterian 1) and the early glacial of the Sanian II (=Elsterian 2) and are correlated with the Cromerian Complex in Western Europe. The modem analogue technique and plant indicator taxa method are applied to two high resolution pollen records (Zdany and Lukow-3a) from E Poland to infer total annual precipitation, mean annual temperature and temperatures of the warmest and the coldest months. The results of the two methods create a coherent picture of climate changes. The succession starts with steppe-tundra and boreal forests, reflecting a cool, late glacial continental climate and develops into widespread Ulmus and Quercus dominated communities, followed by Corylus expansion in warm (at least 18 degrees C in July), oceanic conditions (similar to 800-900 mm annual precipitation) during the first interglacial optimum (F I). The cold, continental climate of the glaciation (FI/II) with annual precipitation of similar to 420 mm and mean January temperature less than -12 degrees C separated the two interglacials. The second interglacial (F II) characterized by Carpinus dominated forests was found to be warm (mean July temperature up to 19 degrees C) but slightly less oceanic, which is consistent with the scarcity of indicators of a warm and humid climate. Principal components analysis (PCA) confirmed the distinctive climatic features of the two interglacials and showed that the cooling F I/II has palynological characteristics Similar to the stadial/interstadial changes within the Sanian I and Sanian II glaciations. (C) 2013 Elsevier B.V. All rights reserved.
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30.
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31.
  • Pidek, Irena Agnieszka, et al. (författare)
  • Taxon-specific pollen deposition dynamics in a temperate forest zone, SE Poland: the impact of physiological rhythmicity and weather controls
  • 2015
  • Ingår i: Aerobiologia. - : Springer Science and Business Media LLC. - 0393-5965 .- 1573-3025. ; 31:2, s. 219-238
  • Tidskriftsartikel (refereegranskat)abstract
    • High and low pollen deposition years in the period 1998-2010 were recorded for ten forest-forming trees in Roztocze (SE Poland) using Tauber-style traps. The coincidence of very high/low pollen deposition years recorded in Tauber traps and aerobiological data obtained by volumetric samplers shows that these phenomena occur simultaneously in different places across vast areas of a tree's distribution range. The natural physiological rhythms displayed in abundance of flowering were considered on the basis of the observed data and published sources. The results obtained from applying Spearman's correlation to pollen accumulation rates from Roztocze and the meteorological parameters confirmed several statistically significant correlations between temperature and summer precipitation prior to pollen emission and a negative correlation with the winter temperature before pollen emission. Air temperature, precipitation, growing season duration (its start and end), winter length and the number of winter days with a daily mean temperature below 0 A degrees C were all considered. The best correlation coefficient results were obtained for the trees most abundant in the vegetation, namely Abies alba, Fagus sylvatica and Pinus sylvestris. Earlier findings on the controlling role of temperature and precipitation during the summer prior to pollen emission were confirmed, and a long period of winter dormancy was stressed as a factor favouring high pollen production. The examples from Roztocze reflected situations when a strong weather signal overrode the natural flowering rhythm. This was observable in the case of P. sylvestris, where pollen production reflected the air temperature of the previous summer or in the case of a mast year, which occurred across the whole distribution range of F. sylvatica in 2006.
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32.
  • Pidek, Irena Agnieszka, et al. (författare)
  • Two pollen-based methods of Eemian climate reconstruction employed in the study of the Żabieniec-Jagodne palaeolakes in central Poland
  • 2022
  • Ingår i: Quaternary International. - : Elsevier BV. - 1040-6182. ; 632, s. 21-35
  • Tidskriftsartikel (refereegranskat)abstract
    • The aim of the present study was to estimate the range of climate variability in Central Poland during the Eemian Interglacial (MIS 5e). High resolution pollen records are available for all seven RPAZs typical of this interglacial in Central Europe. These pollen records were used to estimate total annual precipitation and mean annual temperature, as well as the mean temperatures of the warmest and the coldest months based on the plant indicator method and the modern analogue technique. The reconstructions indicate that the combination of these two methods provides a much clearer insight into the climate changes of the Eemian optimum. The results confirmed no drastic drop in temperature in the Middle Eemian, with high total precipitation in the hazel phase, and that this was followed by a decrease in temperature in the Late Eemian (fir-spruce and pine phases). A drop in precipitation occurred during the youngest part of the Carpinus phase, while coincided with a marked lowering of the water level in lakes and their transformation into peatbogs. The last part of the Eemian is characterized by decreasing temperature, particularly during the coldest month, rising water levels due to a combination of lower evaporation and higher air humidity, and a transition to glacial conditions. Principal Component Analysis found all investigated sites to follow the same pattern of changes. Mean winter temperature, annual temperature and precipitation were found to have a strong positive correlation with the occurrence of thermophilus temperate broadleaved trees (hazel, linden, and ash) typical for the mid-Eemian optimum. These three factors also have a negative correlation with the presence of cold tolerant boreal trees (birch and pine) and open land taxa characteristic of the beginning and end of the interglacial. Mean July temperature was found to be positively correlated with the occurrence of temperate broadleaved trees (oak, ash and elm) typical for early stages of the Eemian and negatively with that of coniferous trees (fir and spruce) characteristic for later stages of the interglacial.
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33.
  • Pirzamanbein, Behnaz, et al. (författare)
  • Bayesian Reconstruction of Past Land Cover From Pollen Data : Model Robustness and Sensitivity to Auxiliary Variables
  • 2020
  • Ingår i: Earth and Space Science. - 2333-5084. ; 7:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Realistic depictions of past land cover are needed to investigate prehistoric environmental changes, effects of anthropogenic deforestation, and long-term land cover-climate feedbacks. Observation-based reconstructions of past land cover are rare, and commonly used model-based reconstructions exhibit considerable differences. Recently, Pirzamanbein et al. (2018, 10.1016/j.spasta.2018.03.005, Spatial Statistics, 24:14–31) developed a statistical interpolation method that produces spatially complete reconstructions of past land cover from pollen assemblage. These reconstructions incorporate a number of auxiliary data sets raising questions regarding the method's sensitivity to different auxiliary data sets. Here the sensitivity of the method is examined by performing spatial reconstructions for northern Europe during three time periods (1900 CE, 1725 CE, and 4000 BCE). The auxiliary data sets considered include the most commonly utilized sources of past land cover data—for example, estimates produced by a dynamic vegetation model and anthropogenic land cover change models. Five different auxiliary data sets were considered, including different climate data driving the dynamic vegetation model and different anthropogenic land cover change models. The resulting reconstructions were evaluated using cross validation for all the time periods. For the recent time period, 1900 CE, the different land cover reconstructions were also compared against a present day forest map. The validation confirms that the statistical model provides a robust spatial interpolation tool with low sensitivity to differences in auxiliary data and high capacity to capture information in the pollen-based proxy data. Further auxiliary data with high spatial detail improves model performance for areas with complex topography or few observations.
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34.
  • Pirzamanbein, Behnaz, et al. (författare)
  • Creating spatially continuous maps of past land cover from point estimates : A new statistical approach applied to pollen data
  • 2014
  • Ingår i: Ecological Complexity. - : Elsevier BV. - 1476-945X .- 1476-9840. ; 20, s. 127-141
  • Tidskriftsartikel (refereegranskat)abstract
    • 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. (C) 2014 Elsevier B.V. All rights reserved.
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35.
  • Pirzamanbein, Behnaz, et al. (författare)
  • Modelling Spatial Compositional Data : Reconstructions of past land cover and uncertainties
  • 2018
  • Ingår i: Spatial Statistics. - : Elsevier. - 2211-6753. ; 24, s. 14-31
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper we construct a hierarchical model for spatial compositional data which is used to reconstruct past land-cover compositions (in terms of coniferous forest, broadleaved forest, and unforested/open land) for five time periods during the past 6000 years over Europe. The model consists of a Gaussian Markov Random Field (GMRF) with Dirichlet observations. A block updated Markov chain Monte Carlo (MCMC), including an adaptive Metropolis adjusted Langevin step, is used to estimate model parameters. The sparse precision matrix in the GMRF provides computational advantages leading to a fast MCMC algorithm. Reconstructions are obtained by combining pollen-based estimates of vegetation cover at a limited number of locations with scenarios of past deforestation and output from a dynamic vegetation model. To evaluate uncertainties in the predictions a novel way of constructing joint confidence regions for the entire composition at each prediction location is proposed. The hierarchical model's ability to reconstruct past land cover is evaluated through cross validation for all time periods, and by comparing reconstructions for the recent past to a present day European forest map. The evaluation results are promising, and the model is able to capture known structures in past land-cover compositions. (C) 2018 Elsevier B.V. All rights reserved.
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36.
  • Poska, Anneli (författare)
  • Human Impact on Vegetation of Coastal Estonia during the Stone Age
  • 2001
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • This thesis presents the dynamics of vegetation and human impact on the environment in coastal Estonia during the Holocene. The sediments of five mires and two lakes from the mainland and from Saaremaa island, and a cultural layer of an Early Mesolithic settlement at Pärnu River were investigated by means of pollen analysis (modern and fossil pollen spectra), 14C dating (AMS and conventional dating) and numerical analysis of pollen data (rarefaction analysis, zonation and principal components analysis). Additional palaeogeographical and archaeological evidence was used to aid interpretation. The integration of bio- and chronostratigraphical results with archaeological evidence has proved to be a powerful tool for the evaluation of the role of people in landscape history and the reconstruction of the introduction of farming to coastal areas of Estonia. Determining pollen zones separately for tree taxa and taxa associated with human impact proved to be an effective basis for describing landscape and anthropogenic changes, respectively. The impact of Mesolithic (9000 - 4900 cal. BC) hunter-gatherers on vegetation in the boreal-nemoral forest zone is detectable by means of pollen analysis, but was restricted in space and time and did not have long-lasting effects on the environment or increase landscape openness. The introduction of crop farming into coastal Estonia was similar to that in southern Sweden, at 4000 cal. BC, and more than 1000 years earlier than it is known from Finland. However, the adoption of crop cultivation took place much later than in southern Sweden. Because of a lack of reliable palynological indicators, the timing of the introduction and adoption of pastoral farming is difficult to pinpoint. The extent and length of vegetation disturbances caused by Neolithic tribes shows that pastoral farming must have been known and was probably more frequent than crop cultivation during the Neolithic (4900 - 1800 cal. BC) in coastal Estonia. The Ulmus decline and the expansion of Picea abies were probably initiated or at least promoted by the introduction of farming in Coastal Estonia.
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37.
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38.
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39.
  • Poska, Anneli, et al. (författare)
  • Reading past landscapes : combining modern and historical records, maps, pollen-based vegetation reconstructions, and the socioeconomic background
  • 2018
  • Ingår i: Landscape Ecology. - : Springer Science and Business Media LLC. - 0921-2973 .- 1572-9761. ; 33:4, s. 529-546
  • Tidskriftsartikel (refereegranskat)abstract
    • Context: Anthropogenic and environmental changes are reshaping landscapes across the globe. In this context, understanding the patterns, drivers, and consequences of these changes is one of the central challenges of humankind. Purpose: We aim to test the possibilities of combining modern multidisciplinary approaches to reconstruct the land-cover and linking the changes in land-cover to socioeconomic shifts in southern Estonia over the last 200 years. Methods: The historical records from five, and maps from six time periods and 79 pollen-based land-cover reconstructions from four lakes are used to determine the land-cover structure and composition and are thereafter combined with the literature based analyses of socioeconomic changes. Results: All information sources recorded similar changes in the land-cover. The anthropogenic deforestation was comparable to today’s (approximately 50%) during the nineteenth century. Major political and socioeconomic changes led to the intensification of agriculture and maximal deforestation (60–85%) at the beginning of the twentieth century. The land nationalisation following the Soviet occupation led to the reforestation of the less productive agricultural lands. This trend continued until the implementation of European Union agrarian subsidies at the beginning of the twenty first century. Conclusions: Pollen-based reconstructions provide a trustworthy alternative to historical records and maps. Accounting for source specific biases is essential when dealing with any data source. The landscape’s response to socioeconomic changes was considerable in Estonia over the last 200 years. Changes in land ownership and the global agricultural market are major drivers in determining the strength and direction of the land-cover change.
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40.
  • Poska, Anneli, et al. (författare)
  • Relative pollen productivity estimates of major anemophilous taxa and relevant source area of pollen in a cultural landscape of the hemi-boreal forest zone (Estonia)
  • 2011
  • Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 167:1-2, s. 30-39
  • Tidskriftsartikel (refereegranskat)abstract
    • Estimates of relevant source area of pollen (RSAP) and relative pollen productivity (PPE) are critical parameters for quantitative reconstructions of past vegetation and land cover. This study provides estimates for PPE relative to Poaceae for ten taxa, characterizing the cultural landscape of south Estonia and the RSAP for 40 lakes with an average radius of approximately 100 m (22-274 m, average 101 m) in the region. We evaluate the effects on those estimates of various combinations of factors, such as the analytical methods (i.e. three Extended R value (ERV) sub-models), the distance-weighting methods used to determine plant abundance, and alternative classification schemes of vegetation and land cover data around study sites. Different combinations of ERV sub-models and distance-weighting methods lead to estimates of RSAP varying between 1500 m and 2000 m. The differences in the estimated RSAP are strongly related to the patch size of the vegetation data. According to ERV sub-model 1, which shows the highest log-likelihood among the three sub-models, most of the taxa have PPE that are higher (Picea, Pin us, Quercus), slightly higher (Salix, Artemisia, Filipendula) or similar (Betula, Cerealia, Cypreraceae) to that of Poaceae. The three ERV sub-models produce only slightly different PPE. However, the selection of distance-weighting method for vegetation has considerable influence on the PPE values. The inverse distance-weighting methods, which do not consider inter-taxonomic differences in pollen dispersal, tend to underestimate PPE for taxa with heavy pollen grains and overestimate PPE for taxa with light pollen grains, compared to the results obtained using other methods that consider taxon specific pollen-dispersal. General land-cover data, based on the classification scheme similar to the CORINE (COoRdination of Information on the Environment) database, could be used for estimating the RSAP and PPE, although some potential problems remain when the classification is too simplified and consolidated. (C) 2011 Elsevier B.V. All rights reserved.
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41.
  • Poska, Anneli, et al. (författare)
  • The Verijarv area, South Estonia over the last millennium: A high resolution quantitative land-cover reconstruction based on pollen and historical data
  • 2014
  • Ingår i: Review of Palaeobotany and Palynology. - : Elsevier BV. - 0034-6667. ; 207, s. 5-17
  • Tidskriftsartikel (refereegranskat)abstract
    • Integration of palynological proxies with annual lamina counting, C-14, Pb-210, Cs-137 and Am-241 radiometric dating, historical documents and old cadastral maps enabled reconstruction of changes in the cultural landscape resulting from extensive forest clearance, arable farming and slash-and-burn practices in South Estonia over the last millennium. Changes in land-cover were quantitatively reconstructed using Landscape Reconstruction Algorithm (LRA) models. These reconstructions are in accordance with historical data from the last century, while reconstructions for the late 19th century time-slice exhibit a considerably more open landscape with a higher portion of cultivated land than that recorded on maps, and possible reasons for this discrepancy are discussed. Taxa represented in the pollen spectrum with values <1% cannot be recommended in reconstructions, as standard deviations are usually larger than the mean cover estimates of the taxon in question. Pollen data and historical evidence suggest that the forest structure changed from fairly open wooded meadow type grazed forests during early periods to closed boreal forest communities typical of the area today. Maximum landscape openness was reached in the 1700s and 1800s, when almost all of the available land was cultivated or used for cattle rearing. Four different periods of landscape development have been differentiated: AD 1000 to 1600, semi-open (20-70%) landscape with increasing intensity of agriculture and openness; AD 1600 to 1870, open (>70%) landscape resulting from extensive agrarian activities including slash-and-burn agriculture; AD 1870 to 1950, cultural landscape with variable openness (70-80%) and AD 1950 to 2000, modern overgrowing semi-open (<70%) landscape. (C) 2014 Elsevier B.V. All rights reserved.
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42.
  • Poska, Anneli, et al. (författare)
  • Timing and drivers of local to regional scale land-cover changes in the hemiboreal forest zone during the Holocene : A pollen-based study from South Estonia
  • 2022
  • Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 277
  • Tidskriftsartikel (refereegranskat)abstract
    • Current land use and climate change pose a threat to the continued provision of ecosystem services expected from terrestrial land cover. Studies on past land-cover responses to such changes provide valuable information for future decisions. The hemiboreal zone, situated between temperate and boreal biomes, is a natural sensitivity hotspot for land cover change: it contains a continuous distribution limit of several temperate (Quercus robur, Tilia cordata, Fraxinus excelsior, Ulmus glabra, etc.) and some boreal (e.g. Picea abies) tree species. High resolution pollen data from three lakes in South Estonia, a hemiboreal zone in Northern Europe, was used to reconstruct the climate-driven dynamics of vegetation composition, anthropogenic deforestation, species-specific responses to climate cycles, and plant related environmental variables during the Holocene at a local and regional scale. The Landscape Reconstruction Algorithm (LRA) was used to reconstruct the vegetation composition, the Ellenberg Indicator Values for environmental reconstructions, and the Wavelet analysis for detecting cyclic patterns. The major land cover and environmental changes are in good accordance with the climate-based formal tripartite subdivision of the Holocene: a quick succession of tundra, boreal, and nemoral biomes during the Early Holocene, a dominance of temperate, broad-leaved forests during the Middle Holocene, and an expansion of mixed boreal forests and anthropogenic deforestation during the Late Holocene. Several episodes of compositional turnover ranging from a century (e.g., the transition from wet to dry tundra) to several millennia (e.g., the replacement of the temperate deciduous forests with boreal mixed forests) were identified. Our results show that local community changes have a shorter duration than the regional ones. The introduction of slash-and-burn agriculture caused abrupt forest composition changes at a local scale, promoting early successional tree species, even prior to the establishment of a permanently open cultural landscape. The only late successional tree species favoured by slash-and-burn cultivation was Picea abies. However, the application of more permanent cultivation strategies reduced its representation considerably. The determined cyclic changes in the proportions of tree taxa show, that most late successional trees exhibit high frequency (ca 200–400 year) cyclicity, probably reflecting the stand scale regeneration processes. The observed 1600 ± 200 and 1200 ± 200 year cycle changes in the occurrences of Quercus robur, Ulmus glabra and U. laevis, and Picea abies have a possible connection with a 1500 ± 500 year Bond cycle. Most of the tested tree taxa also had a statistically significant correlation with the ca 2200–2500 year Bray solar forcing cycle.
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43.
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44.
  • Reckermann, M., et al. (författare)
  • Human impacts and their interactions in the Baltic Sea region
  • 2022
  • Ingår i: Earth Syst. Dynam.. - : Copernicus GmbH. - 2190-4987 .- 2190-4979. ; 13:1, s. 1-80
  • Forskningsöversikt (refereegranskat)abstract
    • Coastal environments, in particular heavily populated semi-enclosed marginal seas and coasts like the Baltic Sea region, are strongly affected by human activities. A multitude of human impacts, including climate change, affect the different compartments of the environment, and these effects interact with each other. As part of the Baltic Earth Assessment Reports (BEAR), we present an inventory and discussion of different human-induced factors and processes affecting the environment of the Baltic Sea region, and their interrelations. Some are naturally occurring and modified by human activities (i.e. climate change, coastal processes, hypoxia, acidification, submarine groundwater discharges, marine ecosystems, non-indigenous species, land use and land cover), some are completely human-induced (i.e. agriculture, aquaculture, fisheries, river regulations, offshore wind farms, shipping, chemical contamination, dumped warfare agents, marine litter and microplastics, tourism, and coastal management), and they are all interrelated to different degrees. We present a general description and analysis of the state of knowledge on these interrelations. Our main insight is that climate change has an overarching, integrating impact on all of the other factors and can be interpreted as a background effect, which has different implications for the other factors. Impacts on the environment and the human sphere can be roughly allocated to anthropogenic drivers such as food production, energy production, transport, industry and economy. The findings from this inventory of available information and analysis of the different factors and their interactions in the Baltic Sea region can largely be transferred to other comparable marginal and coastal seas in the world.
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45.
  • Reitalu, Triin, et al. (författare)
  • Long-term drivers of forest composition in a boreonemoral region: the relative importance of climate and human impact
  • 2013
  • Ingår i: Journal of Biogeography. - : Wiley. - 1365-2699 .- 0305-0270. ; 40:8, s. 1524-1534
  • Tidskriftsartikel (refereegranskat)abstract
    • Aim To assess statistically the relative importance of climate and human impact on forest composition in the late Holocene. Location Estonia, boreonemoral Europe. Methods Data on forest composition (10 most abundant tree and shrub taxa) for the late Holocene (5100-50 calibrated years before 1950) were derived from 18 pollen records and then transformed into land-cover estimates using the REVEALS vegetation reconstruction model. Human impact was quantified with palaeoecological estimates of openness, frequencies of hemerophilous pollen types (taxa growing in habitats influenced by human activities) and microscopic charcoal particles. Climate data generated with the ECBilt-CLIO-VECODE climate model provided summer and winter temperature data. The modelled data were supported by sedimentary stable oxygen isotope (O-18) records. Redundancy analysis (RDA), variation partitioning and linear mixed effects (LME) models were applied for statistical analyses. Results Both climate and human impact were statistically significant predictors of forest compositional change during the late Holocene. While climate exerted a dominant influence on forest composition in the beginning of the study period, human impact was the strongest driver of forest composition change in the middle of the study period, c.4000-2000years ago, when permanent agriculture became established and expanded. The late Holocene cooling negatively affected populations of nemoral deciduous taxa (Tilia, Corylus, Ulmus, Quercus, Alnus and Fraxinus), allowing boreal taxa (Betula, Salix, Picea and Pinus) to succeed. Whereas human impact has favoured populations of early-successional taxa that colonize abandoned agricultural fields (Betula, Salix, Alnus) or that can grow on less fertile soils (Pinus), it has limited taxa such as Picea that tend to grow on more mesic and fertile soils. Main conclusions Combining palaeoecological and palaeoclimatological data from multiple sources facilitates quantitative characterization of factors driving forest composition dynamics on millennial time-scales. Our results suggest that in addition to the climatic influence on forest composition, the relative abundance of individual forest taxa has been significantly influenced by human impact over the last four millennia.
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46.
  • Reitalu, Triin, et al. (författare)
  • Novel insights into post-glacial vegetation change: functional and phylogenetic diversity in pollen records
  • 2015
  • Ingår i: Journal of Vegetation Science. - : Wiley. - 1654-1103 .- 1100-9233. ; 26:5, s. 911-922
  • Tidskriftsartikel (refereegranskat)abstract
    • QuestionHow do pollen-based functional and phylogenetic diversity help to explain post-glacial vegetation change in relation to climate and human influence? LocationEstonia and Latvia, NE Europe. MethodsWe used a data set of 1062 pollen samples from 20 sites covering the last 14500yrs to estimate plant richness, evenness, functional and phylogenetic diversity (community-weighted mean and mean pair-wise distance). We adjusted existing functional and phylogenetic diversity measures for the pollen data and tested the methods with a simulation study. The simulations showed that species-based and pollen-based diversity estimates were all significantly positively correlated. ResultsThe Late Glacial (14500-11650cal. yr BP) and the mid-Holocene (8000-4000cal. yr BP) periods showed contrasting values for most of the diversity components, and several diversity estimates were strongly associated with climate. The cold climate during the Late Glacial led to high phylogenetic diversity, and relatively low functional diversity. Climate warming during the transition from the Late Glacial to the Holocene was followed by a decrease in phylogenetic diversity but an increase in functional diversity based on plant height and seed weight. Increasing human impact in the late Holocene was associated with an increase in plant richness and decreases in functional diversity based on plant height and seed weight and in phylogenetic diversity of herbs. ConclusionsPollen-based functional and phylogenetic diversity provide novel insights into post-glacial vegetation change and its drivers. Both functional and phylogenetic diversity were closely related to climatic conditions, suggesting that trait differences play an important role in long-term community response to climate change. Our results indicate that human impact during the last two millennia has influenced functional and phylogenetic diversity negatively by suppressing plants with certain traits (functional convergence) and giving advantage to plants from certain phylogenetic lineages. We see great potential in the further development of functional and phylogenetic diversity methods for pollen data.
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47.
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48.
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49.
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50.
  • Strandberg, Gustav, 1977-, et al. (författare)
  • Did the Bronze Age deforestation of Europe affect its climate? : A regional climate model study using pollen-based land cover reconstructions
  • 2023
  • Ingår i: Climate of the Past. - : Copernicus Publications. - 1814-9324 .- 1814-9332. ; 19:7, s. 1507-1530
  • Tidskriftsartikel (refereegranskat)abstract
    • This paper studies the impact of land use and land cover change (LULCC) on the climate around 2500 years ago (2.5 ka), a period of rapid transitions across the European landscape. One global climate model was used to force two regional climate models (RCMs). The RCMs used two land cover descriptions. The first was from a dynamical vegetation model representing potential land cover, and the second was from a land cover description reconstructed from pollen data by statistical interpolation. The two different land covers enable us to study the impact of land cover on climate conditions. Since the difference in landscape openness between potential and reconstructed land cover is mostly due to LULCC, this can be taken as a measure of early anthropogenic effects on climate. Since the sensitivity to LULCC is dependent on the choice of climate model, we also use two RCMs. The results show that the simulated 2.5 ka climate was warmer than the simulated pre-industrial (PI, 1850 CE) climate. The largest differences are seen in northern Europe, where the 2.5 ka climate is 2-4 degrees C warmer than the PI period. In summer, the difference between the simulated 2.5 ka and PI climates is smaller (0-3 degrees C), with the smallest differences in southern Europe. Differences in seasonal precipitation are mostly within +/- 10 %. In parts of northern Europe, the 2.5 ka climate is up to 30% wetter in winter than that of the PI climate. In summer there is a tendency for the 2.5 ka climate to be drier than the PI climate in the Mediterranean region. The results also suggest that LULCC at 2.5 ka impacted the climate in parts of Europe. Simulations including reconstructed LULCC (i.e. those using pollen-derived land cover descriptions) give up to 1 degrees C higher temperature in parts of northern Europe in winter and up to 1.5 degrees C warmer in southern Europe in summer than simulations with potential land cover. Although the results are model dependent, the relatively strong response implies that anthropogenic land cover changes that had occurred during the Neolithic and Bronze Age could have affected the European climate by 2.5 ka.
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