TY - JOUR

T1 - Contrasting denitrifier communities relate to contrasting N 2O emission patterns from acidic peat soils in arctic tundra

AU - Palmer, Katharina

AU - Biasi, Christina

AU - Horn, Marcus A.

N1 - Funding Information: Support for this work was provided by the Suomen Akatemia, the Deutsche Forschungsgemeinschaft (DFG HO 4020/2-2) and the University of Bayreuth. We are grateful to Christian Hofmann for help with gas measurements, Chistine Stöcker for analysis of nitrate and nitrite, Rolf Daniel and Andrea Thürmer for pyrosequencing, Steffen Kolb, Markus Nebel and Sebastian Wild for support with JAguc2, as well as Mirjam Selzer and Peter Dörsch for helpful discussions. Copyright: Copyright 2012 Elsevier B.V., All rights reserved.

PY - 2012/5

Y1 - 2012/5

N2 - Cryoturbated peat circles (that is, bare surface soil mixed by frost action; pH 3-4) in the Russian discontinuous permafrost tundra are nitrate-rich 'hotspots' of nitrous oxide (N 2O) emissions in arctic ecosystems, whereas adjacent unturbated peat areas are not. N 2O was produced and subsequently consumed at pH 4 in unsupplemented anoxic microcosms with cryoturbated but not in those with unturbated peat soil. Nitrate, nitrite and acetylene stimulated net N 2O production of both soils in anoxic microcosms, indicating denitrification as the source of N 2O. Up to 500 and 10 M nitrate stimulated denitrification in cryoturbated and unturbated peat soils, respectively. Apparent maximal reaction velocities of nitrite-dependent denitrification were 28 and 18 nmol N 2Og DW -1h -1, for cryoturbated and unturbated peat soils, respectively. Barcoded amplicon pyrosequencing of narG, nirK/nirS and nosZ (encoding nitrate, nitrite and N 2O reductases, respectively) yielded ≈49 000 quality-filtered sequences with an average sequence length of 444 bp. Up to 19 species-level operational taxonomic units were detected per soil and gene, many of which were distantly related to cultured denitrifiers or environmental sequences. Denitrification-associated gene diversity in cryoturbated and in unturbated peat soils differed. Quantitative PCR (inhibition-corrected per DNA extract) revealed higher copy numbers of narG in cryoturbated than in unturbated peat soil. Copy numbers of nirS were up to 1000 × higher than those of nirK in both soils, and nirS nirK -1 copy number ratios in cryoturbated and unturbated peat soils differed. The collective data indicate that the contrasting N 2O emission patterns of cryoturbated and unturbated peat soils are associated with contrasting denitrifier communities.

AB - Cryoturbated peat circles (that is, bare surface soil mixed by frost action; pH 3-4) in the Russian discontinuous permafrost tundra are nitrate-rich 'hotspots' of nitrous oxide (N 2O) emissions in arctic ecosystems, whereas adjacent unturbated peat areas are not. N 2O was produced and subsequently consumed at pH 4 in unsupplemented anoxic microcosms with cryoturbated but not in those with unturbated peat soil. Nitrate, nitrite and acetylene stimulated net N 2O production of both soils in anoxic microcosms, indicating denitrification as the source of N 2O. Up to 500 and 10 M nitrate stimulated denitrification in cryoturbated and unturbated peat soils, respectively. Apparent maximal reaction velocities of nitrite-dependent denitrification were 28 and 18 nmol N 2Og DW -1h -1, for cryoturbated and unturbated peat soils, respectively. Barcoded amplicon pyrosequencing of narG, nirK/nirS and nosZ (encoding nitrate, nitrite and N 2O reductases, respectively) yielded ≈49 000 quality-filtered sequences with an average sequence length of 444 bp. Up to 19 species-level operational taxonomic units were detected per soil and gene, many of which were distantly related to cultured denitrifiers or environmental sequences. Denitrification-associated gene diversity in cryoturbated and in unturbated peat soils differed. Quantitative PCR (inhibition-corrected per DNA extract) revealed higher copy numbers of narG in cryoturbated than in unturbated peat soil. Copy numbers of nirS were up to 1000 × higher than those of nirK in both soils, and nirS nirK -1 copy number ratios in cryoturbated and unturbated peat soils differed. The collective data indicate that the contrasting N 2O emission patterns of cryoturbated and unturbated peat soils are associated with contrasting denitrifier communities.

KW - barcoded amplicon pyrosequencing

KW - global change

KW - permafrost-affected soil

KW - quantitative PCR

KW - wetland

UR - http://www.scopus.com/inward/record.url?scp=84859905060&partnerID=8YFLogxK

U2 - 10.1038/ismej.2011.172

DO - 10.1038/ismej.2011.172

M3 - Article

C2 - 22134649

AN - SCOPUS:84859905060

VL - 6

SP - 1058

EP - 1077

JO - ISME Journal

JF - ISME Journal

SN - 1751-7362

IS - 5

ER -