| 1. |
- Barnekow, Lena, et al.
(författare)
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Strong correlation between summer temperature and pollen accumulation rates for Pinus sylvestris, Picea abies and Betula spp. in a high resolution record from northern Sweden
- 2007
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Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 22:7, s. 653-658
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Tidskriftsartikel (refereegranskat)abstract
- Highly resolved pollen spectra analysed from a 47cm peat monolith recovered from a mire in northern Sweden exhibit climatic sensitivity in the pollen accumulation rates (PAR) of boreal treeline species. Robust temporal control, afforded through multiple AMS radiocarbon dating of the post atomic bomb-test period (AD1961-AD2002), provides a unique opportunity to compare pollen accumulation rates with the instrumental meteorological record. A series of strong correlations are observed between summer temperature and PAR for Pinus sylvestris, Picea abies and Betula spp. (excluding B. nana). Despite well constrained, contiguous (“annual”) sampling, the temporal resolution of the pollen signal preserved within each sample appears to be degraded to ca. 3-5 year resolution. This is likely to reflect processes occurring during peat accumulation and pollen deposition, as well as dating uncertainties and the effects of sub-sampling. These findings identify limitations to the maximum resolution that may realistically be recovered from the peat archive using high resolution sampling protocols and AMS 14C dating. We also identify the need for additional work to quantify the role of climate on peat accumulation and the resultant impact on assemblage based palaeoenvironmental reconstructions within mire sequences. The strongest climate association observed for Picea abies (r2adjusted = 0.53; n=36), was extended through the monolith beyond the 42 year period of “annual” sampling and the response successfully correlated with the Bottenviken historical instrumental record to AD1860. Although only presenting data from a single site, and requiring wider replication, we conclude that for sites close to the ecological limits of tree species, where levels of anthropogenic/non-climatic forcing on pollen production are low, well-dated records of PAR may potentially provide a proxy for reconstructing past summer temperature variability.
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| 2. |
- Bouton, Anthony, et al.
(författare)
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Linking the distribution of microbial deposits from the Great Salt Lake (Utah, USA) to tectonic and climatic processes
- 2016
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 13:19, s. 5511-5526
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Tidskriftsartikel (refereegranskat)abstract
- The Great Salt Lake is a modern hypersaline lake, in which an extended modern and ancient microbial sedimentary system has developed. Detailed mapping based on aerial images and field observations can be used to identify non-random distribution patterns of microbial deposits, such as paleoshorelines associated with extensive polygons or fault-parallel alignments. Although it has been inferred that climatic changes controlling the lake level fluctuations explain the distribution of paleoshorelines and polygons, straight microbial deposit alignments may underline a normal fault system parallel to the Wasatch Front. This study is based on observations over a decimetre to kilometre spatial range, resulting in an integrated conceptual model for the controls on the distribution of the microbial deposits. The morphology, size and distribution of these deposits result mainly from environmental changes (i.e. seasonal to long-term water level fluctuations, particular geomorphological heritage, fault-induced processes, groundwater seepage) and have the potential to bring further insights into the reconstruction of paleoenvironments and paleoclimatic changes through time. New ra-diocarbon ages obtained on each microbial macrofabric described in this study improve the chronological framework and question the lake level variations that are commonly assumed.
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| 3. |
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| 4. |
- Rijal, Dilli P., et al.
(författare)
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Sedimentary ancient DNA shows terrestrial plant richness continuously increased over the Holocene in northern Fennoscandia
- 2021
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Ingår i: Science Advances. - : American Association for the Advancement of Science (AAAS). - 2375-2548. ; 7:31
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Tidskriftsartikel (refereegranskat)abstract
- The effects of climate change on species richness are debated but can be informed by the past. Here, we generated a sedimentary ancient DNA dataset covering 10 lakes and applied novel methods for data harmonization. We assessed the impact of Holocene climate changes and nutrients on terrestrial plant richness in northern Fennoscandia. We find that richness increased steeply during the rapidly warming Early Holocene. In contrast to findings from most pollen studies, we show that richness continued to increase thereafter, although the climate was stable, with richness and the regional species pool only stabilizing during the past three millennia. Furthermore, overall increases in richness were greater in catchments with higher soil nutrient availability. We suggest that richness will increase with ongoing warming, especially at localities with high nutrient availability and assuming that human activity remains low in the region, although lags of millennia may be expected.
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| 5. |
- Risberg, Jan, et al.
(författare)
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Variable isostatic uplift patterns during the Holocene in southeast Sweden, based on high-resolution AMS radiocarbon dates of lake isolations - a preliminary interpretation
- 2008
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Ingår i: Polish Geological Institute Special Papers. - 1507-9791. ; 23, s. 77-80
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Tidskriftsartikel (refereegranskat)abstract
- To describe changes in shoreline configuration in northern Uppland, south-east Sweden, the isolations of 17 present and overgrown lakes have been interpreted from diatom analysis and AMS radiocarbon dates on terrestrial macrofossils. The sites studied are spread c. 60 km in east-west and c. 70 km in north-south direction. The oldest isobase direction, representing the “Neolithic Sea”, extends in more or less north-south direction. The present day isobase system shows a clear east-west trend. The results indicate a complicated pattern of isostatic uplift during the late Holocene. We have defined five different shore displacement curves denoted A – E. It is obvious that the present day east-western isobase system is not valid for the investigated sites. Instead, the north-south isobases for the “Neolithic Sea“ should to a relatively high degree explain the geographic distribution of sites. It is suggested that a re-direction of the isostatic uplift pattern has occurred sometime during the last c. 5000 years. This shift could have taken place as a slow deformation of the bedrock and/or as neotectonic movements along existing fault lines.
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| 6. |
- Rosqvist, Gunhild C., et al.
(författare)
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Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records
- 2013
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 66, s. 22-34
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Tidskriftsartikel (refereegranskat)abstract
- Here we present delta P-18(diatom) data from two high-latitude lakes; one has short residence time and a water isotopic composition (delta O-18(lake)) that fluctuate due to seasonal variations in precipitation and temperature, and the other has delta O-18(lake) that is influenced by longer lake water residence times and evaporation. The delta O-18(diatom) records reveal common responses to precipitation forcing over the past millennium. Relatively wet summers are inferred from delta O-18(diatom) between 1000 and 1080 AD, 1300 and 1440 AD, and during the early 19th century, coincided with periods of high cloud cover inferred from tree-ring carbon isotopes, and other data for high Arctic Oscillation index. While relatively dry summers with increasing influence of winter snow are indicated between 1600 and 1750 AD. The co-response between carbon isotopes in trees and oxygen isotopes in diatoms strengthens the relationship between cloud cover and precipitation and the hypothesis that these changes were the result of significant regional shifts in atmospheric circulation.
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| 7. |
- Wacnik, Agnieszka, et al.
(författare)
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Determining the responses of vegetation to natural processes and human impacts in north-eastern Poland during the last millennium : combined pollen, geochemical and historical data
- 2016
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Ingår i: Vegetation History and Archaeobotany. - : Springer Science and Business Media LLC. - 0939-6314 .- 1617-6278. ; 25:5, s. 479-498
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Tidskriftsartikel (refereegranskat)abstract
- Pollen, charcoal and geochemical investigations were carried out on annually laminated sediments of Lake Zabinskie (54 degrees 07'54.5 '' N; 21 degrees 59'01.1 '' E) and the results were combined with historical and climate data to better understand the mechanism behind plant cover transformations. A millennium-long record of environmental history at 6-years time resolution permitted an assessment of vegetation responses to past human impact and climate fluctuations. Our results show that the history of the region with repeated periods of warfare, epidemics, famine and crop failures is well reflected by environmental proxies. Before the Teutonic Order crusade (AD 1230-1283), agricultural activities of the Prussian tribes were conducted at a distance from the studied lake and caused slight disturbances of local forests. A stronger human impact was registered after ca AD 1460. We confirm that co-domination of pine forests with spruce and oakhornbeam forests on drier habitats as well as the presence of birch and alder woods on wet surfaces near the lake lasted until AD 1610. We identified a transition period of 20 years between AD 1590 and 1610, when forest cover was significantly reduced and the area was partly transformed into open land used for farming activities. The comparison of our data with other pollen datasets from the region confirms significant spatio-temporal differences in the initiation of large-scale woodland clearings in the Great Masurian Lake District. A strong increase in local cultivation was noted after AD 1750 and became even stronger in the period AD 1810-1940. The last 60 years experienced a succession from arable fields and open grasslands to more tree-covered habitats overgrown by birch and alder.
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