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Holocene carbon and nitrogen accumulation rates and contemporary carbon export in discharge

a study from a boreal fen catchment

Larsson, Anna (2016). Holocene carbon and nitrogen accumulation rates and contemporary carbon export in discharge. Uppsala : Sveriges lantbruksuniv.
ISBN 978-91-576-9372-3
eISBN 978-91-576-9373-0
[Licentiate thesis]

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Abstract

The contemporary role of mires in land-atmosphere exchange of carbon dioxide (CO₂) is the subject of intense scientific debate. Investigating patterns and mechanisms of variations in past carbon (C) accumulation rates as well as contemporary C fluxes of peatlands facilitates predictions of future mire C sink strength under a changing climate. Nitrogen (N) is an important macro-nutrient and thereby strongly coupled to the C accumulation rate. Thus, I have investigated Holocene C and N accumulation rates and their potential controls, and the annual and seasonal stream C export during the Holocene at the oligotrophic fen Degerö Stormyr in northern Sweden.

The mean (±SD) long-term apparent rates of C and N accumulation (LORCA and LORNA) were estimated to 13.7±5.5 g C m⁻² yr⁻¹ and 0.28±0.14 g N m⁻² yr⁻¹, respectively. These rates were relatively low compared to those of other northern peatlands. Variations in C and N accumulation rates exhibited similar temporal patterns largely coinciding with major changes in botanical remains, and mainly primary production controlled the accumulation rates. The botanical composition had a major impact on the degree of decomposition, with indications of enrichment of recalcitrant compounds in highly degraded peat, as well as differences in ¹³C-¹²C composition of litter at the onset of decomposition. There were also indications of preferential plant uptake of ¹⁴N at higher N availability.

Stream total C export was primarily driven by discharge, with average annual C export estimated to 12.2 g m⁻² yr⁻¹ over twelve years. This flux typically corresponded to 25-37% of the mean annual net uptake of CO₂ (NEE). However, during a year with a dry summer and wet autumn the discharge C export corresponded to as much as 90%, highlighting the importance of seasonality. The highest TOC export was exhibited during summer when accounting for differences in discharge, underlining the importance of timing of precipitation for the seasonal C export. Seasonal variations in C quality (SUVA₂₅₄) indicate different within mire sources of TOC during the year.

In this thesis I conclude the importance of primary production for C and N accumulation rates, and highlight the importance of seasonality for stream C export from mires.

Authors/Creators:Larsson, Anna
Title:Holocene carbon and nitrogen accumulation rates and contemporary carbon export in discharge
Subtitle:a study from a boreal fen catchment
Year of publishing :2016
Depositing date:14 January 2016
Number of Pages:48
Papers/manuscripts:
NumberReferences
ILarsson, A. Segerström, U. Laudon, H. and Nilsson, M.B. Holocene carbon and nitrogen accumulation rates in a boreal oligotrophic fen (submitted manuscript).
IILeach, J. Larsson, A. Nilsson, M.B. and Laudon, H. Twelve-year interannual and seasonal variability of stream carbon export from a boreal peatland catchment (manuscript).
Place of Publication:Uppsala
Publisher:Department of Forest Ecology and Management, Swedish University of Agricultural Sciences
ISBN for printed version:978-91-576-9372-3
ISBN for electronic version:978-91-576-9373-0
Language:English
Publication Type:Licentiate thesis
Full Text Status:Public
Agris subject categories.:F Plant production > F40 Plant ecology
P Natural resources > P34 Soil biology
Subjects:(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Climate Research
(A) Swedish standard research categories 2011 > 1 Natural sciences > 105 Earth and Related Environmental Sciences > Other Earth and Related Environmental Sciences
Agrovoc terms:bogs, peat, carbon dioxide enrichment, carbon cycle, nitrogen cycle, peatlands, rivers, organic matter, vegetation, botanical composition, nutrient availability (soil)
Keywords:peat, mire, carbon accumulation, nitrogen accumulation, δ¹³C, δ¹⁵N, TOC, DIC, CH₄, stream carbon export
URN:NBN:urn:nbn:se:slu:epsilon-e-3175
Permanent URL:
http://urn.kb.se/resolve?urn=urn:nbn:se:slu:epsilon-e-3175
ID Code:12949
Faculty:S - Faculty of Forest Sciences
Department:(S) > Dept. of Forest Ecology and Management
External funders:FORMAS and Swedish Infrastructure for Ecosystem Science
Deposited By: Anna Larsson
Deposited On:14 Jan 2016 14:32
Metadata Last Modified:06 Feb 2016 18:16

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