Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes

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Vihermaa, Leena E.
Waldron, Susan
Domingues, Tomas
Grace, John
Cosio, Eric G.
Limonchi, Fabian
Hopkinson, Christopher
da Rocha, Humberto R.
Gloor, Emanuel
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AGU Publications
We constructed a whole carbon budget for a catchment in the Western Amazon Basin, combining drainage water analyses with eddy covariance (EC) measured terrestrial CO2 fluxes. As fluvial C export can represent permanent C export it must be included in assessments of whole site C balance, but it is rarely done. The footprint area of the flux tower is drained by two small streams (~5–7 km2 ) from which we measured the dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) export, and CO2 efflux. The EC measurements showed the site C balance to be +0.7 9.7 Mg C ha 1 yr 1 (a source to the atmosphere) and fluvial export was 0.3 0.04 Mg C ha 1 yr 1 . Of the total fluvial loss 34% was DIC, 37% DOC, and 29% POC. The wet season was most important for fluvial C export. There was a large uncertainty associated with the EC results and with previous biomass plot studies ( 0.5 4.1 Mg C ha 1 yr 1 ); hence, it cannot be concluded with certainty whether the site is C sink or source. The fluvial export corresponds to only 3–7% of the uncertainty related to the site C balance; thus, other factors need to be considered to reduce the uncertainty and refine the estimated C balance. However, stream C export is significant, especially for almost neutral sites where fluvial loss may determine the direction of the site C balance. The fate of C downstream then dictates the overall climate impact of fluvial export.
Open access article. Creative Commons Attribution 4.0 International License (CC BY 4.0) applies
Eddy covariance , CO2 efflux , DIC , DOC , POC , Fluvial C export , Dissolved inorganic carbon , Dissolved organic carbon , Particulate organic carbon , Western Amazon Basin
Vihermaa, L. E., Waldron, S., Domingues, T., Grace, J., Cosio, E. G., Limonchi, F., Hopkinson, C., da Rocha, H. R., & Gloor, E. (2016). Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes. Journal of Geophysical Research: Biogeosciences, 121(12), 3001-3018. https://doi.org/10.1002/2016JG003464