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Variations in the Concentrations of Nitrous Oxide in the Soil Pore Space at the Tapajos National Forest

Raimundo Cosme Oliveira Jr, Embrapa Amazonia Oriental, cosme@cpatu.embrapa.br (Presenting)
Michael Keller, University New Hampshire, michael@kaos.sr.unh.edu
Patrick Michael Crill, University of Stockolm, patrick.crill@geo.su.se
Plinio Camargo, Cena-USP, pcamargo@cena.usp.br
Hudson Silva, UFPA-STM, hudson@lbasantarem.com.br
Risonaldo Lima, IFT, risonaldo@lbasantarem.com.br
Cleuton Pereira, IFT, cleuton@lbasantarem.com.br
Kemeson Oliveira, IFT, kemeson@lbasantarem.com.br
Kadson Oliveira, FDB, kadson@lbasantarem.com.br
Augusto Maia, FDB, augusto@lbasantarem.com.br

Over the course of two years, we made weekly measurements of the concentrations of nitrous oxide, carbon dioxide and methane in the soil pore space at depths from 0.05 to 2.00 m in three replicated profiles. Near the end of the first year of observations, two large trees fell in the vicinity of one of the three profiles (03) resulting in a notable change in nitrous oxide mixing ratios within this profile. The mixing ratios of nitrous oxide in profile 03 varied from 650 to 2060 ppb at 0.05 m depth and from 1130 to 5990 ppb at 2.00 m; these mixing ratios were significantly greater (p<0.05) than the mixing ratios measured in profiles 01 and 02. Carbon dioxide concentrations also increased in profile 03 compared to profiles 01 and 02 although to a lesser extent. Results from previous studies in tropical forests have indicated that root mortality may result in increased soil-atmosphere emissions of nitrous oxide (Keller et al. 2000; Varner et al., 2003; Silver et al. 2005). Our observations support the hypothesis that root mortality increases the pool of available organic matter and the consumption of oxygen within the soil leading to conditions favorable for nitrous oxide production.

Science Theme:  TG (Trace Gases)

Presentation Type:  Poster

Abstract ID: 25

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