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Fluvial carbon export from a lowland Amazonian rainforest in relation to atmospheric fluxes
Author(s) -
Vihermaa Leena E.,
Waldron Susan,
Domingues Tomas,
Grace John,
Cosio Eric G.,
Limonchi Fabian,
Hopkinson Chris,
Rocha Humberto Ribeiro,
Gloor Emanuel
Publication year - 2016
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1002/2016jg003464
Subject(s) - fluvial , environmental science , drainage basin , hydrology (agriculture) , eddy covariance , total organic carbon , tributary , particulates , carbon sink , dissolved organic carbon , carbon cycle , ecosystem , environmental chemistry , atmospheric sciences , geology , chemistry , climate change , ecology , structural basin , geomorphology , oceanography , geography , biology , cartography , geotechnical engineering
We constructed a whole carbon budget for a catchment in the Western Amazon Basin, combining drainage water analyses with eddy covariance (EC) measured terrestrial CO 2 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 km 2 ) from which we measured the dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), particulate organic carbon (POC) export, and CO 2 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.