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Organic carbon fluxes within and streamwater exports from headwater catchments in the southern Amazon
Author(s) -
Johnson Mark S.,
Lehmann Johannes,
Selva Evandro Carlos,
Abdo Mara,
Riha Susan,
Couto Eduardo Guimarães
Publication year - 2006
Publication title -
hydrological processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.222
H-Index - 161
eISSN - 1099-1085
pISSN - 0885-6087
DOI - 10.1002/hyp.6218
Subject(s) - throughfall , total organic carbon , dry season , wet season , environmental science , hydrology (agriculture) , dissolved organic carbon , plant litter , streamflow , flux (metallurgy) , surface runoff , amazon rainforest , ecosystem , environmental chemistry , soil water , drainage basin , chemistry , ecology , geology , soil science , geography , geotechnical engineering , biology , cartography , organic chemistry
Forms and quantities of organic carbon (C) fluxes at the soil surface, and organic C exports from four small (1–2 ha) headwater catchments were quantified and contrasted in the seasonally dry southern Amazon for 1 year to compare C fluxes within the terrestrial ecosystem with exports to the aquatic ecosystem. At the soil surface, the flux of litterfall C was 43 times greater than the dissolved organic carbon (DOC) flux in throughfall, with the highest rates of C deposition during the dry season. The form and timing of organic C was reversed for watershed exports, where DOC comprised 59% of the annual total organic C export, and exports were greatest during the 4‐month rainy season (63% of total annual exports). Fine particulate organic carbon (FPOC) in streamwater was a substantially larger flux than coarse particulate organic carbon (CPOC), representing 37 and 4% of total annual organic C exports, respectively. Particulate organic C exports exhibited substantial seasonal variability, with FPOC and CPOC mobilized primarily in the rainy season and strongly connected to storm events. Storm flow comprised 6% of total streamflow for the year studied, and 10% of streamflow during the rainy season. In the rainy season, over 90% of FPOC exports were transported by storm flow, while only 32% of DOC exports were exported by storm flow during this period. Streamwater DOC concentrations were found to increase linearly with increasing terrestrial litterfall during the dry season ( r 2 = 0·92, p < 0·001), indicating that in‐stream processing of allochthonous litterfall is an important source of DOC during the dry season. Copyright © 2006 John Wiley & Sons, Ltd.