title: Tillage Management and Seasonal Effects on Denitrifier Community Abundance, Gene Expression and Structure over Winter.
abstract: Tillage effects on denitrifier communities and nitrous oxide (N2O) emissions were mainly studied during the growing season. There is limited information for the non-growing season, especially in northern countries where winter has prolonged periods with sub-zero temperatures. The abundance and structure of the denitrifier community, denitrification gene expression and N2O emissions in fields under long-term tillage regimes [no-tillage (NT) vs conventional tillage (CT)] were assessed during two consecutive winters. NT exerted a positive effect on nirK and nosZ denitrifier abundance in both winters compared to CT. Moreover, the two contrasting managements had an opposite influence on nirK and nirS RNA/DNA ratios. Tillage management resulted in different denitrifier community structures during both winters. Seasonal changes were observed in the abundance and the structure of denitrifiers. Interestingly, the RNA/DNA ratios were greater in the coldest months for nirK, nirS and nosZ. N2O emissions were not influenced by management but changed over time with two orders of magnitude increase in the coldest month of both winters. In winter of 2009-2010, emissions were mainly as N2O, whereas in 2010-2011, when soil temperatures were milder due to persistent snow cover, most emissions were as dinitrogen. Results indicated that tillage management during the growing season induced differences in denitrifier community structure that persisted during winter. However, management did not affect the active cold-adapted community structure.
authors: Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, NB, E3B 4Z7, Canada.
authors: Enrico
authors: E
authors: Tatti
authors: Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, NB, E3B 4Z7, Canada. claudia.goyer@agr.gc.ca.
authors: Claudia
authors: C
authors: Goyer
authors: Department of Environmental Sciences, Agricultural Campus, Dalhousie University, PO Box 550, Truro, B2N 5E3, Canada.
authors: David L
authors: DL
authors: Burton
authors: Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, NB, E3B 4Z7, Canada.
authors: Sophie
authors: S
authors: Wertz
authors: Potato Research Centre, Agriculture and Agri-Food Canada, Fredericton, NB, E3B 4Z7, Canada.
authors: Bernie J
authors: BJ
authors: Zebarth
authors: Soils and Crops Research and Development Centre, Agriculture and Agri-Food Canada, 2560 Hochelaga Blvd, Québec, QC, G1V 2J3, Canada.
authors: Martin
authors: M
authors: Chantigny
authors: Département de Biologie, Université de Moncton, Moncton, NB, E1A 3E9, Canada.
authors: Martin
authors: M
authors: Filion
mesh_terms: D000383:Agriculture / Q000379:methods*; D001419:Bacteria / Q000235:genetics* / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D058440:Denitrification; D015870:Gene Expression; D064307:Microbiota; D009609:Nitrous Oxide; D009674:Nova Scotia; D012621:Seasons; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology
chemical_list: D001426:Bacterial Proteins; D012987:Soil; D009609:Nitrous Oxide
keywords: Denitrifiers; Frozen versus unfrozen soils; Greenhouse gas emission; Tillage