HR: 1340h
AN: B43A-0123    [Abstracts]
TI: Soil-Atmosphere Exchange of Nitrous Oxide, Nitric Oxide, Methane, and Carbon Dioxide in Logged and Undisturbed Forest in the Tapajos National Forest, Brazil
AU: * Keller, M
EM: michael.keller@unh.edu
AF: USDA Forest Service International Institute of Tropical Forestry, Jardin Botanico Sur 1201 Calle Ceiba, San Juan, PR 00926-1119 United States
AU: Varner, R K
EM: ruth.varner@unh.edu
AF: Complex Systems Research Center, University of New Hampshire, Durham, NH 03824 United States
AU: Dias, J D
AF: ESALQ, USP, Piracicaba, SP 1 Brazil
AU: Silva, H
EM: hsilva@kaos.sr.unh.edu
AF: Complex Systems Research Center, University of New Hampshire, Durham, NH 03824 United States
AU: Crill, P M
EM: patrick.crill@geo.su.se
AF: Department of Geology and Geochemistry, Stockholm University, Stockholm, 1 Sweden
AU: de Oliveira, R C
EM: cosme@cpatu.embrapa.br
AF: EMBRAPA, Amazonia Oriental, Belem, PA 1 Brazil
AU: Asner, G P
EM: gpa@stanford.edu
AF: Department of Global Ecology Carnegie Institution of Washington, Stanford University, Stanford, CA 94305 United States
AB: Selective logging is an extensive land use in the Brazilian Amazon region. We studied the soil-atmosphere fluxes of nitrous oxide (N$_{2}$O), nitric oxide (NO), methane (CH$_{4}$), and carbon dioxide (CO$_{2}$) on two soil types (clay Oxisol and sandy loam Ultisol) over two years (2000-2001) in both undisturbed forest and forest recently logged using reduced impact forest management in the Tapajos National Forest, near Santarem, Para, Brazil. In undisturbed forest, annual soil-atmosphere fluxes of N$_{2}$O (mean +/- standard error) were 7.9 +/- 0.7 and 7.0 +/- 0.6 ng N cm$^{-2}$ h$^{-1}$ for the Oxisol and 1.7 +/- 0.1 and 1.6 +/- 0.3 ng N cm$^{-2}$ h$^{-1}$ for the Ultisol for 2000 and 2001 respectively. The annual fluxes of NO from undisturbed forest soil in 2001 was 9.0 +/- 2.8 ng N cm$^{-2}$ h$^{-1}$ for the Oxisol and 8.8 +/- 5.0 ng N cm$^{-2}$ h$^{-1}$ for the Ultisol. Consumption of CH$_{4}$ from the atmosphere dominated over production on undisturbed forest soils. Fluxes averaged -0.3 +/- 0.2 and -0.1 +/- 0.9 mg CH$_{4}$ m$^{-2}$ d$^{-1}$ on the Oxisol and -1.0 +/- 0.2 and -0.9 +/- 0.3 mg CH$_{4}$ m$^{-2}$ d$^{-1}$ on the Ultisol for years 2000 and 2001. For CO$_{2}$ in 2001, the annual fluxes averaged 3.6 +/- 0.4 $\mu$mol m$^{-2}$ d$^{-1}$ on the Oxisol and 4.9 +/- 1.1 $\mu$mol m$^{-2}$ d$^{-1}$ on the Ultisol. We measured fluxes over one year each from two recently logged forests on the Oxisol in 2000 and on the Ultisol in 2001. Sampling in logged areas was stratified from greatest to least ground disturbance covering log decks, skid trails, tree-fall gaps, and forest matrix. Areas of strong soil compaction, especially the skid trails and logging decks were prone to significantly greater emissions of N$_{2}$O, NO, and especially CH$_{4}$. In the case of CH$_{4}$, estimated annual emissions from decks reached extremely high rates of 531 +/- 419 and 98 +/- 41 mg CH$_{4}$ m$^{-2}$ d$^{-1}$, for Oxisol and Ultisol respectively, comparable to wetland emissions in the region. We calculated excess fluxes from logged areas by subtraction of a background forest flux and adjusted these fluxes for the proportional area of ground disturbance. Our calculations suggest that selective logging increases emissions of N$_{2}$O and NO from 30$%$ to 350$%$ depending upon conditions. While undisturbed forest was a CH$_{4}$ sink, logged forest tended to emit methane at moderate rates. Soil-atmosphere CO$_{2}$ fluxes were only slightly affected by logging. The regional effects of logging cannot be simply extrapolated based upon one site. We studied sites where reduced impact harvest management was used while in typical conventional logging ground damage is twice as great. Our results indicate that for N$_{2}$O, NO, and CH$_{4}$, logging disturbance may be as important for regional budgets of these gases as other extensive land use changes in the Amazon such as the conversion of forest to cattle pasture.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting