| 1. |
- Bakumenko, Varvara, et al.
(författare)
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Chironomidae-based inference model for mean July air temperature reconstructions in the eastern Baltic area
- 2024
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Ingår i: Boreas. - 0300-9483.
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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)
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Pollen productivity estimates of key European plant taxa for quantitative reconstruction of past vegetation : a review
- 2008
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Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 17:5, s. 461-478
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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)
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Holocene forest-cover changes in Europe - a comparison of dynamic vegetation model results and pollen-based REVEALS reconstructions
- 2023
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Ingår i: EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11206. - : European Geosciences Union (EGU).
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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)
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The challenge of comparing pollen-based quantitative vegetation reconstructions with outputs from vegetation models - a European perspective
- 2023
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Ingår i: Climate of the Past. - : Copernicus Publications. - 1814-9324 .- 1814-9332. ; 19:7, s. 1531-1557
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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)
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Late-Holocene expansion of a south Swedish peatland and its impact on marginal ecosystems: Evidence from dendrochronology, peat stratigraphy and palaeobotanical data
- 2014
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Ingår i: The Holocene. - : SAGE Publications. - 0959-6836 .- 1477-0911. ; 24:4, s. 466-476
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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)
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Fire hazard modulation by long-term dynamics in land cover and dominant forest type in eastern and central Europe
- 2020
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4189. ; 17:5, s. 1213-1230
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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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| 7. |
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| 8. |
- Gaillard, Marie-José, et al.
(författare)
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Causes of Regional Change : Land Cover
- 2015
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Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160054 - 9783319160061 ; , s. 453-477
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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)
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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
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Ingår i: Towards a more accurate quantification of human-environment interactions in the past. ; , s. 25-26
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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)
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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
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Ingår i: Geophysical Research Abstracts.
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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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