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Surface wetness and mire development during the late Holocene in central Sweden
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi och kvartärgeologi (INK).
(engelsk)Inngår i: Boreas, ISSN 0300-9483, E-ISSN 1502-3885Artikkel i tidsskrift (Fagfellevurdert) Accepted
Abstract [en]

Late Holocene mire development and surface wetness changes have been studied in a small mixed mire located in central Sweden. Today the mire is characterised by a mainly ombrotrophic centre dominated by Sphagnum mosses whereas Carex content increase towards the more minerotrophic mire margins. Two peat sequences extracted from the central ombrotrophic part were investigated for stratigraphy, humification, testate amoebae analysis, C/N ratio and 13C and 15N stable isotopes. Three main stages of mire development are identified with a first stage between ca 4200-2600 cal yr BP, characterised by water-logged conditions suggesting a minerotrophic fen stage. The second stage between ca 2600-1000 cal yr BP is characterised by more ombrotrophic conditions and Sphagnum dominated vegetation. The onset of the prominent change at ca 2600 cal yr BP could have been initiated by by climate change coincident with a change in solar activity. The last stage, between ca 1000-50 cal yr BP, is dominated by more ombrotrophic conditions suggesting increased precipitation. This study shows that the response of hydrological proxies in a mixed mire during its development towards more ombrotrophic conditions might result in conflicting results, which has to be considered in palaeoenvironmental reconstructions from mires that changes between ombrotrophic and minerotrophic settings.

Emneord [en]
mire development, testate amoebae, surface wetness, C/N ratio, humification, late Holocene, central Sweden
HSV kategori
Forskningsprogram
kvartärgeologi
Identifikatorer
URN: urn:nbn:se:su:diva-36881OAI: oai:DiVA.org:su-36881DiVA, id: diva2:290875
Tilgjengelig fra: 2010-01-28 Laget: 2010-01-28 Sist oppdatert: 2017-12-12bibliografisk kontrollert
Inngår i avhandling
1. Late Holocene humidity variability in central Sweden
Åpne denne publikasjonen i ny fane eller vindu >>Late Holocene humidity variability in central Sweden
2010 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

The aim of this thesis was to reconstruct humidity variability in central Sweden during the late Holocene. A multi-proxy approach was used to infer humidity changes as recorded in a lake and a mire. Age-models were constructed based on radiocarbon dating and the Askja-1875 tephra. Stable isotopes (δ18O and δ13C) on Chara spp encrustations and Pisidium spp mollusc shells and carbon content were analysed in the lake record, whereas peat stratigraphy, humification, testate amoebae assemblages, C/N ratio and stable isotopes (δ13C and δ15N) were analysed in the mire record. Stable isotopes (δ2H and δ18O) on lake water showed that Lake Blektjärnen responded to changes in the balance between evaporation and input water (E/I ratio). A high E/I ratio results from a dry and probably warmer climate during which evaporation and atmospheric equilibration likely enrich lake water in 18O and 13C, respectively, and vice versa for a low E/I ratio. The relatively high Chara δ18O and δ13C values between ca 4400 and 4000 cal yr BP thus suggest relatively dry and likely warm conditions, whereas depleted values suggest wetter and probably cooler conditions between ca 4000 and 3000 cal yr BP. Again, drier and probably warmer conditions were inferred from the relatively enriched δ18O values between ca 2500 and 1000 cal yr BP, and depleted δ18O values were recorded between ca 1000 and 50 cal yr BP indicating wetter and likely cooler conditions. The results from the mire mainly indicated vegetation succession, however, the changes inferred at ca 2600 and 1000 cal yr BP could have been triggered by climate change. This study shows that the proxies responded sensitively to humidity changes in the investigated archives allowing for reconstruction of climate change in central Sweden during late Holocene.

sted, utgiver, år, opplag, sider
Stockholm: Department of Physical Geography and Quaternary Geology, Stockholm University, 2010. s. 60
Serie
Dissertations from the Department of Physical Geography and Quaternary Geology, ISSN 1653-7211 ; 20
Emneord
humidity change, stable isotopes, Chara spp, Pisidium spp, testate amoebae assemblages, humification, C/N ratio, late Holocene, central Sweden
HSV kategori
Forskningsprogram
kvartärgeologi
Identifikatorer
urn:nbn:se:su:diva-36884 (URN)978-91-7155-929-6 (ISBN)
Disputas
2010-03-05, De Geersalen, Geovetenskapens hus, Svante Arrhenius väg 14, Stockholm, 13:00 (engelsk)
Opponent
Veileder
Merknad
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 3: Accepted. Paper 5: In progress.Tilgjengelig fra: 2010-02-11 Laget: 2010-01-28 Sist oppdatert: 2010-10-07bibliografisk kontrollert

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