High N2O consumption potential of weakly disturbed fen mires with dissimilar denitrifier community structure. (March 2019)

• Record Type: Journal Article
• Authors: Buchen, C.; Roobroeck, D.; Augustin, J.; Behrendt, U.; Boeckx, P.; Ulrich, A.
• Is Part Of: Soil biology and biochemistry. Volume 130(2019)
• Page Start: 63
• Page End: 72
• Publication Date: 2019-03
• Subjects: Nitrous oxide -- Dinitrogen -- Fen mires -- He incubation -- Denitrifier functional genes; Soil biochemistry -- Periodicals; Soil biology -- Periodicals; Sols -- Biochimie -- Périodiques; Sols -- Biologie -- Périodiques; Sols -- Microbiologie -- Périodiques; Bodembiologie; Biochemie; 631.46
• DOI: 10.1016/j.soilbio.2018.12.001
• Languages: English
• ISSNs: 0038-0717

Abstract

Abstract: Peat soils can be strong sources of atmospheric nitrous oxide (N2 O), but at the same time act as sinks for the greenhouse gas N2 O. However, the role of N2 O reduction to dinitrogen (N2 ) here is still not fully understood. In particular, this applies to pristine or weakly disturbed fen mires. These types of peatland ecosystems are characterised by anoxic soil conditions and special N dynamics restricted to ammonium (NH4 + ) turnover and very low nitrate (NO3 − ) availability. N2 O and N2 fluxes from intact soil cores from three weakly disturbed fen mire types and two soil habitats (tussocks and hollows) were investigated using the helium (He) incubation approach. Ambient air in headspaces were first substituted with a He-O2 trace gas mixture to quantify N2 O and N2 exchanges under prevailing soil oxygen (O2 ) conditions, and then with an anoxic He trace gas mixture (99.9% He) for establishing the maximum possible denitrification rate. Changing from the He-O2 mixture to a pure He trace gas mixture led to strong increase of N2 fluxes (up to 2916 μg N m −2 h −1 ) and negative N2 O fluxes of up to −72 μg N m −2 h −1 . Whilst small differences in N gas fluxes were found between all types of fen mires, an analysis of the denitrifier abundance based on nirK, nirS and nosZ genes indicated respectively more pronounced variation. The structure of denitrifier communities exhibited a strong plot specificity driven by water-filled pore space, soil organic matter and soil pH. This short-term He incubation experiment revealed that weakly disturbed fen mires act as considerable N2 O sinks under anoxic conditions and improved our knowledge of the original N dynamics in this peatland ecosystem. Highlights: Quantification of maximum denitrification rate of peat soils by anoxic He incubation. Strong N2 O sink capacity under anoxic conditions in N-limited fen mires. Differences of bacterial denitrifier community structure between fen types are driven by soil properties.