Carbon balance of a Finnish bog : temporal variability and limiting factors based on 6 years of eddy-covariance data

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Alekseychik , P , Korrensalo , A , Mammarella , I , Launiainen , S , Tuittila , E-S , Korpela , I & Vesala , T 2021 , ' Carbon balance of a Finnish bog : temporal variability and limiting factors based on 6 years of eddy-covariance data ' , Biogeosciences , vol. 18 , no. 16 , pp. 4681-4704 . https://doi.org/10.5194/bg-18-4681-2021

Title: Carbon balance of a Finnish bog : temporal variability and limiting factors based on 6 years of eddy-covariance data
Author: Alekseychik, Pavel; Korrensalo, Aino; Mammarella, Ivan; Launiainen, Samuli; Tuittila, Eeva-Stiina; Korpela, Ilkka; Vesala, Timo
Contributor: University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
University of Helsinki, Institute for Atmospheric and Earth System Research (INAR)
University of Helsinki, Biosciences
University of Helsinki, Department of Forest Sciences
University of Helsinki, Viikki Plant Science Centre (ViPS)
Date: 2021-08-17
Language: eng
Number of pages: 24
Belongs to series: Biogeosciences
ISSN: 1726-4170
URI: http://hdl.handle.net/10138/333910
Abstract: Pristine boreal mires are known as substantial sinks of carbon dioxide (CO2) and net emitters of methane (CH4). Bogs constitute a major fraction of pristine boreal mires. However, the bog CO2 and CH4 balances are poorly known, having been largely estimated based on discrete and short-term measurements by manual chambers and seldom using the eddy-covariance (EC) technique. Eddy-covariance (EC) measurements of CO2 and CH4 exchange were conducted in the Siikaneva mire complex in southern Finland in 2011-2016. The site is a patterned bog having a moss-sedge-shrub vegetation typical of southern Eurasian taiga, with several ponds near the EC tower. The study presents a complete series of CO2 and CH4 EC flux (F-CH4) measurements and identifies the environmental factors controlling the ecosystem-atmosphere CO2 and CH4 exchange. A 6-year average growing season (May-September) cumulative CO2 exchange of -61 +/- 24 g Cm-2 was observed, which partitions into mean total respiration (Re) of 167 +/- 33 (interannual range 146-197) g Cm-2 and mean gross primary production (GPP) of 228 +/- 46 (interannual range 193-257) g Cm-2, while the corresponding F-CH4 amounts to 7.1 +/- 0.7 (interannual range 6.4-8.4) g Cm-2. The contribution of October-December CO2 and CH4 fluxes to the cumulative sums was not negligible based on the measurements during one winter. GPP, Re and F-CH4 increased with temperature. GPP and F-CH4 did not show any significant decline even after a substantial water table drawdown in 2011. Instead, GPP, Re and F-CH4 were limited in the cool, cloudy and wet growing season of 2012. May-September cumulative net ecosystem exchange (NEE) of 2013-2016 averaged at about 73 g Cm-2, in contrast with the hot and dry year 2011 and the wet and cool year 2012. Suboptimal weather likely reduced the net sink by about 25 g Cm-2 in 2011 due to elevated Re, and by about 40 g Cm-2 in 2012 due to limited GPP. The cumulative growing season sums of GPP and CH4 emission showed a strong positive relationship. The EC source area was found to be comprised of eight distinct surface types. However, footprint analyses revealed that contributions of different surface types varied only within 10 %-20% with respect to wind direction and stability conditions. Consequently, no clear link between CO2 and CH4 fluxes and the EC footprint composition was found despite the apparent variation in fluxes with wind direction.
Subject: NET ECOSYSTEM EXCHANGE
CO2 EXCHANGE
NORTHERN PEATLANDS
METHANE EBULLITION
FLUX MEASUREMENTS
BOREAL FEN
CH4
EMISSION
TEMPERATURE
DYNAMICS
1172 Environmental sciences
1171 Geosciences
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