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

• Published in: Biogeosciences
• Main Authors: Alekseychik, Pavel, Korrensalo, Aino, Mammarella, Ivan, Launiainen, Samuli, Tuittila, Eeva-Stiina, Korpela, Ilkka, Vesala, Timo
• Other Authors: Institute for Atmospheric and Earth System Research (INAR), Micrometeorology and biogeochemical cycles, Biosciences, Department of Forest Sciences, Ilkka Korpela / Principal Investigator, Forest Ecology and Management, Viikki Plant Science Centre (ViPS), Ecosystem processes (INAR Forest Sciences)
• Format: Article in Journal/Newspaper
• Language: English
• Published: COPERNICUS GESELLSCHAFT MBH 2021
• Subjects: NET ECOSYSTEM EXCHANGE; CO2 EXCHANGE; NORTHERN PEATLANDS; METHANE EBULLITION; FLUX MEASUREMENTS; BOREAL FEN; CH4; EMISSION; TEMPERATURE; DYNAMICS; 1172 Environmental sciences; 1171 Geosciences; Tower The; taiga
• Online Access: http://hdl.handle.net/10138/333910

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 ...