Soil-Atmosphere Flux of Nitrous Oxide and Methane Measured on Sandy Loam and Clay Soils in Undisturbed Forest at the FLONA Tapajos, Brazil
Eráclito
Rodrigues de
Sousa Neto, Fundação Floresta Tropical, Santarem, Para, Brazil,, eraclito@lbaeco.com.br
(Presenting)
Jadson
Dizencourt
Dias, Tropical, Santarem, Para, Brazil,, jadson@lbaeco.com.br
Hudson
Silva, University of New Hampshire, Complex Systems Research Center, Morse Hall, NH., USA, hsilva@kaos.sr.unh
Sérgio
N. da Silva
Albuquerque, Fundação Floresta Tropical, sergio@lbaeco.com.br
Kêmeson
Oliveira, Fundação Floresta Tropical, kemeson@lbaeco.com.br
Michael
M.
Keller, USDA, Forest Servics, michael.keller@unh.edu
Patrick
Michael
Crill, University of New Hampshire, Complex Systems Research Center, Morse Hall, NH., USA, patrick.crill@unh.edu
Raimundo
Cosme de
Oliveira Jr., EMBRAPA - Amazonia Oriental, Santarem, Para, Brazil, cosme@cpatu.embrapa.br
Nitrous oxide (N2O) and methane (CH4) are important greenhouse gases. Tropical forest soils account for the largest natural source of N2O. Most upland tropical forest soils studied so far consume CH4. We measured soil-atmosphere flux of N2O and CH4 using static chambers during 30 minute long emplacements. Four samples were removed at equal time intervals in nylon syringes and transported to our laboratory in Santarem for analysis within about 24 hours of collection. We analyzed N2O and CH4 using gas electron capture and flame ionization gas chromatography. To determine concentrations, integrated sample peak areas were compared to peak areas for commercially prepared standards that had been calibrated against the LBA-ECO standards. We calculated fluxes by linear regression of 3-4 concentration-time pairs. Our sampling points were randomly selected at intervals of 2-4 weeks at mature undisturbed forest sites near the km 83 IBAMA base in the Tapajos National Forest (FLONA Tapajos). Approximately 8 chamber measurements were made during each sampling period on both sandy Ultisols and clayey Oxisols. Soil and air temperature and soil moisture were measured at the same time as gas fluxes.
N2O emissions from clay greatly exceeded the emissions from sand. Over 2 years of measurement, N2O emissions from clay soils averaged 7.09 (+ 5.14) ng-N cm-2 h-1 while emissions from sand soils averaged only 1.67 (+ 1.44) ng-N cm-2 h-1. Sand soils generally consumed more CH4 than clay soils (-1.24 (+ 4.16) mg-CH4 m-2 d-1 vs. 0.11 (+ 4.23) mg-CH4 m-2 d-1). Seasonal variation of both N2O and CH4 fluxes appeared to be controlled primarily by soil moisture. For N2O, wet season (January-June) emissions greatly exceeded dry season (July – December) emissions. In the case of CH4, fluxes were near zero during the wet season but notably negative (indicating consumption of methane in the soil) during the dry season.
Submetido por Lorena Cordeiro Brewster em 31-MAR-2004