HR: 10:40h
AN: H22B-02    [Abstracts]
TI: CO2 dynamics in nested catchments: a longitudinal perspective from soil to 1st and 2nd order streams
AU: * Johnson, M S
EM: msj8@cornell.edu
AF: Cornell University Department of Crop and Soil Sciences, Bradfield Hall, Ithaca, NY 14853 United States
AU: Lehmann, J
EM: CL273@cornell.edu
AF: Cornell University Department of Crop and Soil Sciences, Bradfield Hall, Ithaca, NY 14853 United States
AU: Riha, S J
EM: sjr4@cornell.edu
AF: Cornell University Department of Earth and Atmospheric Sciences, Bradfield Hall, Ithaca, NY 14853 United States
AU: Couto, E G
EM: couto@ufmt.br
AF: Federal University of Mato Grosso Department of Soil Sciences, Av. Fernando Correa s/n, Cuiaba, MT 78060-900 Brazil
AB: Fluxes of CO2 from terrestrial to aquatic environments were investigated in a nested catchment study in the seasonally-dry southern Amazon. Dissolved CO2 concentrations in groundwater springs, four 1st order streams and one 2nd order stream were determined via routine sampling and in-situ monitoring. CO2 concentrations were monitored in the soil atmosphere to 8m. Belowground, the seasonal trend in soil CO2 concentrations at depth lagged that of seasonal water table dynamics, with peak concentrations (8.7% CO2 vol/vol at 4m) occurring one month after maximum water table height, indicating a shift in root respiration and plant water uptake to deeper soil layers during the dry season. Peak dissolved CO2 concentrations in springs and streams lagged the soil CO2 maximum by an additional month. During storm events, streamflow CO2 concentrations were found to decrease initially, reflecting the initial contribution of low-CO2 direct precipitation and surface runoff. Streamwater CO2 then increased as the contribution of pre-event water to storm flow increased. Dissolved CO2 in springs was also found to increase during storm events. Diurnal fluctuations in dissolved CO2 of springs were also observed, indicating the connectivity of the biosphere, pedosphere and hydrosphere for headwater catchments. The dissolved CO2 concentration within 1st order streams decreases rapidly downstream from stream sources, with spring CO2 concentration 3.3 times that at headwater catchment outlets. This initial outgassing of CO2 within 1st order streams was found to be accompanied by a corresponding increase in the pH of stream water. However, dissolved CO2 concentrations were not found to be significantly different between 1st and 2nd order streams. This suggests a discontinuity between some processes at the terrestrial-aquatic interface in headwater catchments and those of larger-order watersheds.
DE: 0428 Carbon cycling (4806)
DE: 0438 Diel, seasonal, and annual cycles (4227)
DE: 1813 Eco-hydrology
DE: 1875 Vadose zone
DE: 9360 South America
SC: Hydrology [H]
MN: Fall Meeting 2005