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Responses of N 2 O fluxes to temperature, water table and N deposition in a northern boreal fen
Author(s) -
Lohila A.,
Aurela M.,
Hatakka J.,
Pihlatie M.,
Minkkinen K.,
Penttilä T.,
Laurila T.
Publication year - 2010
Publication title -
european journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 1351-0754
DOI - 10.1111/j.1365-2389.2010.01265.x
Subject(s) - snow , flux (metallurgy) , peat , atmospheric sciences , environmental science , nitrogen , nitrous oxide , deposition (geology) , hydrology (agriculture) , water table , growing season , atmosphere (unit) , table (database) , boreal , chemistry , ecology , geography , geology , meteorology , biology , geotechnical engineering , organic chemistry , sediment , groundwater , paleontology , computer science , data mining
Nitrous oxide (N 2 O) fluxes were measured fortnightly to monthly with manual chambers in 2004–2008 and hourly with automatic chambers during the snow‐free seasons of 2007 and 2008 in a sedge fen in northern Finland. The fluxes were generally low, varying from −45 to 37 µg N 2 O–N m −2 hour −1 (negative fluxes indicating uptake of N 2 O from the atmosphere into the soil) and showing large spatial and temporal variation. Slightly higher emissions were observed in winter than in summer. On an annual scale, the fen acted as a N 2 O source. The annual balances showed a clear decreasing trend from 1.1 kg N ha −1 year −1 (= 12.2 µg N m −2 hour −1 ) in 2004 to zero balances in 2007 and 2008. Two potential reasons for the decreasing mean flux were (i) a decreasing atmospheric N deposition during the snow‐free season, and (ii) a rising water‐table level (WTL), which restricts the availability of oxygen in the peat and therefore favours the formation of molecular nitrogen (N 2 ) instead of N 2 O by the denitrifying microbes. The measurements conducted with the automatic chambers during the snow‐free season showed a positive exponential relationship between the N 2 O flux and the temperature in 2008, but not in 2007. Similarly, a unimodal relationship with the WTL was found in 2008, with maximum fluxes observed when the WTL was about 4 cm above the fen surface. No diurnal variation in N 2 O fluxes measured by automatic chambers was found. The fluxes measured by the manual or automatic chambers were similar in magnitude, but different in their temporal pattern. The daily N 2 O concentration at a depth of 0.15 m in the peat was always lower than the ambient atmospheric concentration, indicating that at this depth the atmospheric N 2 O was consumed. Together with the observed negative flux rates this suggests that microbial N 2 production is a significant part of the N cycle in this fen.