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Trondman, A.-K., Gaillard, M.-J., Mazier, F., Sugita, S., Fyfe, R., Nielsen, A. B., . . . Wick, L. (2015). Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling. Global Change Biology, 21(2), 676-697
Open this publication in new window or tab >>Pollen-based quantitative reconstructions of Holocene regional vegetation cover (plant-functional types and land-cover types) in Europe suitable for climate modelling
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2015 (English)In: Global Change Biology, ISSN 1354-1013, E-ISSN 1365-2486, Vol. 21, no 2, p. 676-697Article in journal (Refereed) Published
Abstract [en]

We present quantitative reconstructions of regional vegetation cover in north-western Europe, western Europe north of the Alps, and eastern Europe for five time windows in the Holocene [around 6k, 3k, 0.5k, 0.2k, and 0.05k calendar years before present (bp)] at a 1 degrees x1 degrees spatial scale with the objective of producing vegetation descriptions suitable for climate modelling. The REVEALS model was applied on 636 pollen records from lakes and bogs to reconstruct the past cover of 25 plant taxa grouped into 10 plant-functional types and three land-cover types [evergreen trees, summer-green (deciduous) trees, and open land]. The model corrects for some of the biases in pollen percentages by using pollen productivity estimates and fall speeds of pollen, and by applying simple but robust models of pollen dispersal and deposition. The emerging patterns of tree migration and deforestation between 6k bp and modern time in the REVEALS estimates agree with our general understanding of the vegetation history of Europe based on pollen percentages. However, the degree of anthropogenic deforestation (i.e. cover of cultivated and grazing land) at 3k, 0.5k, and 0.2k bp is significantly higher than deduced from pollen percentages. This is also the case at 6k in some parts of Europe, in particular Britain and Ireland. Furthermore, the relationship between summer-green and evergreen trees, and between individual tree taxa, differs significantly when expressed as pollen percentages or as REVEALS estimates of tree cover. For instance, when Pinus is dominant over Picea as pollen percentages, Picea is dominant over Pinus as REVEALS estimates. These differences play a major role in the reconstruction of European landscapes and for the study of land cover-climate interactions, biodiversity and human resources.

Keywords
Europe, Holocene, plant-functional types, pollen data, quantitative past land cover, REVEALS model
National Category
Environmental Sciences
Research subject
Environmental Science, Paleoecology
Identifiers
urn:nbn:se:lnu:diva-40897 (URN)10.1111/gcb.12737 (DOI)000348652400016 ()25204435 (PubMedID)2-s2.0-84923209714 (Scopus ID)
Available from: 2015-03-17 Created: 2015-03-17 Last updated: 2019-01-23Bibliographically approved
Pirzamanbein, B., Lindstrom, J., Poska, A., Sugita, S., Trondman, A.-K., Fyfe, R., . . . Gaillard, M.-J. (2014). Creating spatially continuous maps of past land cover from point estimates: A new statistical approach applied to pollen data. Ecological Complexity: An International Journal on Biocomplexity in the Environment and Theoretical Ecology, 20, 127-141
Open this publication in new window or tab >>Creating spatially continuous maps of past land cover from point estimates: A new statistical approach applied to pollen data
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2014 (English)In: Ecological Complexity: An International Journal on Biocomplexity in the Environment and Theoretical Ecology, ISSN 1476-945X, E-ISSN 1476-9840, Vol. 20, p. 127-141Article in journal (Refereed) Published
Abstract [en]

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.

Keywords
Land cover, Spatial modeling, Paleoecology, Pollen, Compositional data, Gaussian Markov random fields
National Category
Earth and Related Environmental Sciences
Research subject
Environmental Science, Paleoecology
Identifiers
urn:nbn:se:lnu:diva-40090 (URN)10.1016/j.ecocom.2014.09.005 (DOI)000348010800013 ()2-s2.0-84907948370 (Scopus ID)
Available from: 2015-02-12 Created: 2015-02-12 Last updated: 2019-01-23Bibliographically approved
Marquer, L., Gaillard, M.-J., Sugita, S., Trondman, A.-K., Mazier, F., Nielsen, A. B., . . . Seppä, H. (2014). Holocene changes in vegetation composition in northern Europe: why quantitative pollen-based vegetation reconstructions matter. Quaternary Science Reviews (90), 199-216
Open this publication in new window or tab >>Holocene changes in vegetation composition in northern Europe: why quantitative pollen-based vegetation reconstructions matter
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2014 (English)In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, no 90, p. 199-216Article in journal (Refereed) Published
Abstract [en]

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.

National Category
Ecology Other Earth and Related Environmental Sciences
Research subject
Environmental Science, Paleoecology
Identifiers
urn:nbn:se:lnu:diva-33551 (URN)10.1016/j.quascirev.2014.02.013 (DOI)000336466800014 ()2-s2.0-84897853043 (Scopus ID)
Available from: 2014-04-02 Created: 2014-04-02 Last updated: 2019-01-23Bibliographically approved
Strandberg, G., Kjellström, E., Poska, A., Wagner, S., Gaillard, M.-J., Trondman, A.-K., . . . Sugita, S. (2014). Regional climate model simulations for Europe at 6 and 0.2 k BP: sensitivity to changes in anthropogenic deforestation. Climate of the Past, 10(2), 661-680
Open this publication in new window or tab >>Regional climate model simulations for Europe at 6 and 0.2 k BP: sensitivity to changes in anthropogenic deforestation
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2014 (English)In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 10, no 2, p. 661-680Article in journal (Refereed) Published
Abstract [en]

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

National Category
Earth and Related Environmental Sciences
Research subject
Environmental Science, Paleoecology
Identifiers
urn:nbn:se:lnu:diva-33547 (URN)10.5194/cp-10-661-2014 (DOI)000335374600016 ()2-s2.0-84897427235 (Scopus ID)
Available from: 2014-04-02 Created: 2014-04-02 Last updated: 2019-01-23Bibliographically approved
Strandberg, G., Kjellström, E., Poska, A., Wagner, S., Gaillard, M.-J., Trondman, A.-K., . . . Sugita, S. (2013). Regional climate model simulations for Europe at 6 k and 0.2 k yr BP: sensitivity to changes in anthropogenic deforestation.. Climate of the Past Discussions, 9(5), 5785-5836
Open this publication in new window or tab >>Regional climate model simulations for Europe at 6 k and 0.2 k yr BP: sensitivity to changes in anthropogenic deforestation.
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2013 (English)In: Climate of the Past Discussions, ISSN 1814-9340, E-ISSN 1814-9359, Vol. 9, no 5, p. 5785-5836Article in journal (Refereed) Published
Abstract [en]

This study aims to evaluate the direct effects of anthropogenic deforestation on simulated climate at two contrasting periods in the Holocene, ~6 k BP and ~0.2 k BP in Europe. We apply RCA3, a regional climate model with 50 km spatial resolution, for both time periods, considering three alternative descriptions of the past vegetation: (i) potential natural vegetation (V) simulated by the dynamic vegetation model LPJ-GUESS, (ii) potential vegetation with anthropogenic land cover (deforestation) as simulated by the HYDE model (V + H), and (iii) potential vegetation with anthropogenic land cover as simulated by the KK model (V + K). The KK model estimates are closer to a set of pollen-based reconstructions of vegetation cover than the HYDE model estimates. The climate-model results show that the simulated effects of deforestation depend on both local/regional climate and vegetation characteristics. At ~6 k BP the extent of simulated deforestation in Europe is generally small, but there are areas where deforestation is large enough to produce significant differences in summer temperatures of 0.5–1 °C. At ~0.2 k BP, simulated deforestation is much more extensive than previously assumed, in particular according to the KK model. This leads to significant temperature differences in large parts of Europe in both winter and summer. In winter, deforestation leads to lower temperatures because of the differences in albedo between forested and unforested areas, particularly in the snow-covered regions. In summer, deforestation leads to higher temperatures in central and eastern Europe since evapotranspiration from unforested areas is lower than from forests. Summer evaporation is already limited in the southernmost parts of Europe under potential vegetation conditions and, therefore, cannot become much lower. Accordingly, the albedo effect dominates also in summer, which implies that deforestation causes a decrease in temperatures. Differences in summer temperature due to deforestation range from −1 °C in south-western Europe to +1 °C in eastern Europe. The choice of anthropogenic land cover estimate has a significant influence on the simulated climate, but uncertainties in palaeoclimate proxy data for the two time periods do not allow for a thorough comparison with climate model results.

National Category
Ecology
Research subject
Environmental Science, Paleoecology
Identifiers
urn:nbn:se:lnu:diva-31259 (URN)10.5194/cpd-9-5785-2013 (DOI)
Available from: 2013-12-13 Created: 2013-12-13 Last updated: 2018-05-17Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5772-3782

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