HR: 09:00h
AN: B41C-04    [Abstracts]
TI: Forest Canopy-Atmosphere Gas Exchange Rates in the Tapajos National Forest, Para, Brazil, Determined by Radon-222 Measurements
AU: * Martens, C S
EM: cmartens@email.unc.edu
AF: UNC-Chapel Hill, Dept of Marine Sciences, Chapel Hill, NC 27599-3300 United States
AU: Shay, T J
AF: UNC-Chapel Hill, Dept of Marine Sciences, Chapel Hill, NC 27599-3300 United States
AU: Mendlovitz, H P
AF: UNC-Chapel Hill, Dept of Marine Sciences, Chapel Hill, NC 27599-3300 United States
AU: Moura, J S
AF: USP, CENA, Piracicaba, - 1 Brazil
AU: Lima, R L
AF: LBA-ECO, Santarem Laboratory, Santarem, - 1 Brazil
AU: Sampaio, I G
AF: LBA-ECO, Santarem Laboratory, Santarem, - 1 Brazil
AU: Moraes, O L
AF: Universidade Federal de Santa Maria, Dept of Physics, Santa Maria, - 1 Brazil
AU: Woodward, w S
AF: UNC-Chapel Hill, Dept of Marine Sciences, Chapel Hill, NC 27599-3300 United States
AU: Crill, P M
AF: University of New Hampshire, Complex Systems Center, Durham, NH 03824 United States
AB: Continuous canopy air and soil-air flux measurements of radon-222 have been combined to quantify canopy-atmosphere gas exchange rates and canopy air residence times in Amazonian old growth and selectively logged forests in the Tapajos National Forest near Santar‚m, Par , Brazil, as part of the LBA project led by Brazil. Radon canopy air and soil flux measurements, when fully integrated with LBA studies led by other investigators including tower eddy covariance fluxes, forest canopy gas inventories and soil gas fluxes can provide independent quantification of gas production, consumption and within the canopy plus net canopy-atmosphere fluxes. Canopy and above-canopy air radon activities at up to ten tower elevations at forest sites decrease systematically with height above the soil surface. Diel radon activity variations in the Tapajos forest canopy at both sites are characterized by dual maxima peaking near approximately 0900 and 1730 local time that occur respectively as a result of nocturnal stratification and late afternoon stratification during the early evening transition. Radon inventories within the lower 10m of the forest canopy typically range by over 200 percent over a diel cycle. Soil-air radon fluxes were determined using portable radon fluxometers capable of repeated thirty-minute flux measurements on soil collars installed around the tower sites. Radon flux divergence within the forest canopy can be utilized to quantitatively determine the net rates and canopy vertical distribution of CO2 or methane and other trace gas production and consumption processes when combined with their soil flux and canopy profile measurements. The combined canopy and soil flux radon data also yields canopy air residence times throughout the diel cycle.
DE: 3322 Land/atmosphere interactions
DE: 1610 Atmosphere (0315, 0325)
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting