HR: 1340h
AN: B53A-0936    [Abstracts]
TI: Quasi-continuous Measurements of Methane Fluxes Over a Managed Peatland in the Sacramento-San Joaquin Delta
AU: * Detto, M
EM: mdetto@nature.berkeley.edu
AF: University California Berkeley, 40 Hilgard Hall, Berkeley, CA 94720, United States
AU: Teh, Y A
EM: yit@nature.berkeley.edu
AF: University California Berkeley, 40 Hilgard Hall, Berkeley, CA 94720, United States
AU: Silver, W
EM: wsilver@nature.berkeley.edu
AF: University California Berkeley, 40 Hilgard Hall, Berkeley, CA 94720, United States
AU: Baldocchi, D
EM: Baldocchi@nature.berkeley.edu
AF: University California Berkeley, 40 Hilgard Hall, Berkeley, CA 94720, United States
AU: Hehn, T j
EM: thehn@nature.berkeley.edu
AF: University California Berkeley, 40 Hilgard Hall, Berkeley, CA 94720, United States
AB: Peatlands are composed of vegetation growing in water-logged, wetland environments and, in general, they are effective sinks of carbon because their saturated soils inhibit the decomposition of detritus. Because peatlands store so much carbon they have played a critical role in maintaining regulating and moderating climate and, consequently, they are expected to play a critical role in our future climate, especially if their water table drops and the organic peat is oxidized and released to the atmosphere as carbon dioxide. Fresh-water peatlands, with saturated soils and high carbon content, are also significant sources of carbon, in the form of methane, an important greenhouse gas. Most methane emission datasets and derived source-functions have been generated using chambers placed over wetlands, plants and soils. This methodology is useful and appropriate for studying mechanisms and spatial variability at small scales. However, it is less well suited for estimating annual fluxes or patterns over large areas. The eddy covariance method is capable of measuring methane efflux directly and for extended periods in a quasi-continuous manner. Unfortunately, this method has been under utilized, in part because of the reliance on expensive and labor-intensive tunable diode laser spectrometers. A new generation of infrared laser absorption spectrometers, which uses off-axis integrated cavity output spectroscopy, has recently become available (Los Gatos Research). The instrument can measure methane fluctuation at 10 Hz, hence it is suitable for continuous eddy covariance measurements of methane. Starting from April 2007, an eddy-covariance system, which measures CO2, CH4 and H2O directly and simultaneously, was installed to better estimate temporal and spatial patterns in methane efflux across the soil- plant-atmosphere interfaces of a managed peatland. The measurements were conducted at Sherman Island which is on the west side of the Sacramento-San Joaquin Delta and is on land managed by the California Department of Water Resources. Preliminary results show that the co-spectra of methane and vertical wind fluctuations are similar with the co- spectra of H2O, temperature and CO2. The fluxes were comparable with independent observations from chamber measurements. During the summer period, water table depth was 60 cm and CH4 fluxes were observed mainly during the night when the footprint was larger (due to increasing stability of the air) and advection from near wet fields were registered.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0490 Trace gases
DE: 3322 Land/atmosphere interactions (1218, 1631, 1843)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting