Dinitrogen and nitrous oxide exchanges from an undrained monolith fen: short‐term responses following nitrate addition

Abstract

Gaseous nitrogen exchanges from undrained peat soils and the effect of external nitrate input are poorly understood. This paper reports net N-2, and N2O exchanges as well as the short-term responses to nitrate addition from contrasting tussock and hollow soil habitats in an undrained monolith fen ecosystem located in northeast Poland. Gaseous N exchange rates were quantified by means of a He substitution technique. The net N-2 production in hollows (2.53 mg N m(-2) hour(-1)) was significantly higher than in tussocks (1.04 mg N m(-2) hour(-1)). Hollows also constituted a marked N2O sink (-3.04 mu g N m(-2) hour(-1)), while tussocks were a source for atmospheric N2O (2.08 mu g N m(-2) hour(-1)). Following amendment by NO3-, at a rate similar to atmospheric NO3- deposition (wet + dry), hollows showed a drastic shift to net production of N2O but a non-significant increase in N-2 production. In tussocks only a minor increase of N-2 and N2O production was observed after NO3- addition. This study emphasizes the influence of physico-chemical conditions and biotic resource competition on the rates and responses of microbial denitrification in undrained fen ecosystems. Inferring a simple field-scale estimation of gaseous N emission suggests that undrained, monolith fen ecosystems constitute substantial sources of N-2 (1.79 mg N m(-2) hour(-1)) and considerable sinks for N2O (-0.96 mu g N m(-2) hour(-1)). These findings are of importance to further improve greenhouse gas budgeting and assess the impacts of global change on undrained fen ecosystems

Nitrogen mineralization and gaseous nitrogen losses from waterlogged and drained organic soils in a black alder (<i>Alnus glutinosa</i> (L.) Gaertn.) forest

“…However, N 2 O fluxes measured temporarily confirm our assumption that in periods of low water level net nitrification also occurs at the undrained site, albeit at a low level. Thus, we conclude that for most of the year denitrification activity is NO For N 2 fluxes no comparable values from the field are available in the literature, but N 2 fluxes observed in the incubation experiment are in the range of other studies from drained and undrained fen ecosystems (e.g., Teiter and Mander, 2005;Wray and Bayley, 2007;Mander et al, 2008;Roobroeck et al, 2010;Soosaar et al, 2011).…”

“…Due mainly to analytical difficulties in the determination of microbially produced N 2 , to date the denitrification potential from waterlogged peat soils has rarely been estimated (Watts and Seitzinger, 2000;Mander et al, 2003;Teiter and Mander, 2005;Wray and Bayley, 2007;Roobroeck et al, 2010;Soosaar et al, 2011;Uri et al, 2011). The substitution of ambient N 2 by Helium (He) in laboratory studies possibly represents the most reliable method for the direct and simultaneous determination of N 2 O and N 2 exchange rates (Butterbach-Bahl et al, 2002;Roobroeck et al, 2010;Butterbach-Bahl et al, 2013).…”

“…For measurements of N 2 , N 2 O, CO 2 and CH 4 fluxes, we applied the helium-oxygen (He-O) method (Butterbach-Bahl et al, 2002;Mander et al, 2003;Roobroeck et al, 2010;Uri et al, 2011) using four different incubation temperatures (0, 5, 15 and 25 • C). Five replications per site and moisture content were simultaneously placed in special gas-tight incubation vessels inside a climate chamber.…”

Nitrous oxide emissions from a peatbog after 13 years of experimental nitrogen deposition

“…Nykanen et al (2002) found no response of N 2 O emission to additions of up to 100 kg N ha −1 yr −1 (NH 4 NO 3 ) to a Sphagnum fuscum pine bog in Finland, over a 6-year study. Following nitrate addition to ex situ peat cores from Polish sedge fen, Roobroeck et al (2010) Some clearer positive responses have been observed where bogs have been drained, or where very high levels of nitrogen have been applied. Regina et al (1998) found that N 2 O emissions were increased by up to 0.8 nmol m −2 s −1 for around nine months after a single experimental N addition of 100 kg N ha −1 yr −1 on a drained and forested peatland in Finland; KNO 3 , NH 4 Cl, and urea gave a similar range of responses.…”

Effect of reed canary grass cultivation on greenhouse gas emission from peat soil at controlled rewetting

“…RCG may further increase the emissions of reduced soil gases as the aerenchyma tissues act as a conduit for the direct transport of, for example, CH 4 and N 2 O produced in soil (Joabsson et al, 1999;Jørgensen et al, 2012). Also, RCG can decrease N 2 O emissions by assimilation of mineral N, which reduces the availability of electron acceptors (nitrate) for denitrifying microorganisms (Roobroeck et al, 2010). In summary, the introduction of RCG at rewetted peatlands may cause a change in the patterns and underlying mechanisms of GHG emission, which are rather complex.…”