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CO 2 efflux from Amazonian headwater streams represents a significant fate for deep soil respiration
Author(s) -
Johnson Mark S.,
Lehmann Johannes,
Riha Susan J.,
Krusche Alex V.,
Richey Jeffrey E.,
Ometto Jean Pierre H. B.,
Couto Eduardo Guimarães
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl034619
Subject(s) - streams , amazonian , soil water , groundwater , environmental science , soil gas , hydrology (agriculture) , dissolved organic carbon , atmosphere (unit) , soil respiration , environmental chemistry , carbon dioxide , surface water , carbon cycle , soil science , geology , ecology , chemistry , ecosystem , amazon rainforest , environmental engineering , computer network , geotechnical engineering , physics , computer science , biology , thermodynamics
Large Amazonian rivers are known to emit substantial amounts of CO 2 to the atmosphere, while the magnitude of CO 2 degassing from small streams remains a major unknown in regional carbon budgets. We found that 77% of carbon transported by water from the landscape was as terrestrially‐respired CO 2 dissolved within soils, over 90% of which evaded to the atmosphere within headwater reaches of streams. Hydrologic transport of dissolved CO 2 was equivalent to nearly half the gaseous CO 2 contributions from deep soil (>2 m) to respiration at the soil surface. Dissolved CO 2 in emergent groundwater was isotopically consistent with soil respiration, and demonstrated strong agreement with deep soil CO 2 concentrations and seasonal dynamics. During wet seasons, deep soil (2–8 m) CO 2 concentration profiles indicated gaseous diffusion to deeper layers, thereby enhancing CO 2 drainage to streams. Groundwater discharge of CO 2 and its subsequent evasion is a significant conduit for terrestrially‐respired carbon in tropical headwater catchments.