Document: DIA-3-59-57
Seasonal patterns of NO and N2O emissions in forest and pastures in the southwestern Brazilian Amazon.
GARCIA-MONTIEL, D.C.* 1, P.A.STEUDLER 1, J.MELILLO 1, C.NEILL 1, M.PICCOLO 2 and C.CERRI 2
Marine Biological Laboratory, Woods Hole, MA 02543 USA 1
Centro de Energia Nuclear na Agricultura, Caixa Postal 96, Piracicaba, SP CEP 134160, Brazil 2
Abstract:
Short-term dynamics associated with soil drying and wetting in seasonal humid tropical forests and pastures of the Amazon Basin may be especially important for N oxide emissions because soils in this region experience prolonged dry periods when there is little rain. We investigated the effect of wet and dry season and the transition period on the dynamics of NO and N2O fluxes in the southwestern Brazilian Amazon State of Rondonia. We used chronosequences of forests and pastures of different ages to document seasonal patterns on trace gas emissions. We conducted field moisture manipulation experiments to examine the short-term releases of these gases that can result after the onset of precipitation following the dry season. Moisture manipulation trials were conducted at the end of the dry season in a mature moist forest and 12- and 27-year-old pastures and trace gas measurements were conducted before, immediately following and for 24 hours after a simulated 30-mm/m2-rain event. Measurements were made employing a re-circulating chamber and luminol chemiluminescence for NO and electron capture gas chromatography for N2O. Changes in soil pools of NH4 and NO3, N cycling rates, soil moisture and temperature were also measured. We found that NO and N2O emissions were partitioned between the dry and wet season, however, we did not find a direct relationship between soil moisture content and N gas fluxes. We concluded that although soil moisture is an important factor controlling the seasonal emission of N oxide fluxes in this region, it is soil N availability that appears to control the absolute release of N oxide emissions.
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This abstract is being presented at: 3:30 PM in session:
Poster Session #15: Nutrient Cycling.