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Effects of freeze-thaw cycles on low temperature carbon mineralisation in peat
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
Linköping University, The Tema Institute, Department of Water and Environmental Studies. Linköping University, Faculty of Arts and Sciences.
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Recent investigations indicate that winter carbon emission from peatlands and low temperature carbon mineralisation processes conld have the potential to affect annual carbon budgets. Special emphasis has been put on periods of freeze-thaw events during spring and autumn. The aim of this study was to investigate the impact of freeze-thaw cycles on peat carbon mineralisation. This was addressed by following production rates and total amounts of CO,- and CH4-formation in surface (0-5 cm) and deep (45-50 cm) peat samples incubated at 4°C and comparing controls with replicate samples subjected to three consecutive freeze-thaw cyclesprior to incubation. Accumulation of fermentation products (H2, VF A and ethanol) were measured in order to gain further insight to the biogeochemical processes and transformation pathways involved. We conclude that freeze-thaw cycles affect both short and long term formation and exchange of C02 by altering the availability and amount of peat carbon substrates. Freeze-thaw events also resulted in an inhibition of methanogenesis with a concomitant accumulation in H2 and butyrate. We conclude that freezethaw cycling events can be of large importance for the carbon budgets of northern peatland ecosystems, although they are of a limited temporal duration.

National Category
Social Sciences Interdisciplinary
Identifiers
URN: urn:nbn:se:liu:diva-79155OAI: oai:DiVA.org:liu-79155DiVA: diva2:538487
Available from: 2012-06-29 Created: 2012-06-29 Last updated: 2012-06-29Bibliographically approved
In thesis
1. Northern peatland carbon biogeochemistry: the influence of vascular plants and edaphic factors on carbon dioxide and methane exchange
Open this publication in new window or tab >>Northern peatland carbon biogeochemistry: the influence of vascular plants and edaphic factors on carbon dioxide and methane exchange
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The interest in carbon dynamics and the interactions between ecosystems and the atmosphere has increased during the last decade due to the postulated threat of anthropgenically induced global and climate change. Northern peatlands, with their large stores of organic carbon and long-term net accumulation of atmospheric carbon dioxide are key ecosystems in these interactions. Furthermore, peatlands transform organic carbon to methane, which also is an important greenhouse gas.

The findings reported in this thesis and in the accompanying papers are based on both laboratory and field investigations of carbon transformation dynamics on the process scale and at the resolution of individual peatland plant communities. The data from one of the studies also is extrapolated in an attempt to identify environmental controls on regional scales in order to predict the response of northern pcatlands to climate warming.

The laboratory experiments focus on how climate variations, inducing fluctuations in groundwater level and also soil freeze-thaw cycles, influences organic matter mineralisation to carbon dioxide and methane. The field studies investigate year-to-year variations and interdecadal differences in carbon gas exchange at a subarctic peatland, and also how the physiological activities of vascular plants control methane emission rates.

The main conclusions presented include:

Soil freeze-thaw events may be very important for the annual carbon balance in northern peatlands, because they have the potential to increase mineralisation rates and alter biogeochemical degradation pathways.

Vascular plants exert a strong influence on methane flux dynamics during the growing season, both by mediating methane transport and through substrate-based interactions with the soil microbial community. However, there are important species-related factors that govern the nature and extent of this influence.

Caution has to be taken when extrapolating field data to estimate regional carbon exchange because the relevance of the specific environmental parameters that control this exchange varies depending on resolution. On broad spatial and temporal scales the best predictor of peatland methane emissions is mean soil temperature, but also microbial substrate availability (expressed as the organic acid concentration in peat water) is of importance. This temperature sensitivity represents a strong potential feedback mechanism on climate change.

Place, publisher, year, edition, pages
Linköping: Linköpings Universitet, 2001. 44 p.
Series
Linköping Studies in Arts and Science, ISSN 0282-9800 ; 245Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 729
Keyword
Biogeokemi, Biologi, Autekologi, Klimatologi
National Category
Social Sciences Interdisciplinary
Identifiers
urn:nbn:se:liu:diva-29578 (URN)14954 (Local ID)91-7373-233-8 (ISBN)14954 (Archive number)14954 (OAI)
Public defence
2001-12-14, Sal Elysion, Hus-T, Universitetsområdet Valla, Linköping, 10:00 (English)
Opponent
Supervisors
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2014-08-28Bibliographically approved

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Berg, AndersSvensson, Bo

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