DOC and DIC in Flowpaths of Amazonian Headwater Catchments with Hydrologically Contrasting Soils
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Organic and inorganic carbon (C) fluxes transported by water were evaluated for dominant hydrologic flowpaths on two adjacent headwater catchments in the Brazilian Amazon with distinct soils and hydrologic responses from September 2003 through April 2005. The Ultisol-dominated catchment produced 30% greater volume of storm-related quickflow (overland flow and shallow subsurface flow) compared to the Oxisol-dominated catchment. Quickflow fluxes were equivalent to 3.2 ± 0.2% of event precipitation for the Ultisol catchment, compared to 2.5 ± 0.3% for the Oxisol-dominated watershed (mean response ±1 SE, n = 27 storms for each watershed). Hydrologic responses were also faster on the Ultisol watershed, with time to peak flow occurring 10 min earlier on average as compared to the runoff response on the Oxisol watershed. These different hydrologic responses are attributed primarily to large differences in saturated hydraulic conductivity (K s). Overland flow was found to be an important feature on both watersheds. This was evidenced by the response rates of overland flow detectors (OFDs) during the rainy season, with overland flow intercepted by 54 ± 0.5% and 65 ± 0.5% of OFDs for the Oxisol and Ultisol watersheds respectively during biweekly periods. Small volumes of quickflow correspond to large fluxes of dissolved organic C (DOC); DOC concentrations of the hydrologic flowpaths that comprise quickflow are an order of magnitude higher than groundwater flowpaths fueling base flow (19.6 ± 1.7 mg l−1 DOC for overland flow and 8.8 ± 0.7 mg l−1 DOC for shallow subsurface flow versus 0.50 ± 0.04,mg l−1 DOC in emergent groundwater). Concentrations of dissolved inorganic C (DIC, as dissolved CO2–C plus HCO 3 − –C) in groundwater were found to be an order of magnitude greater than quickflow DIC concentrations (21.5 mg l−1 DIC in emergent groundwater versus 1.1 mg l−1 DIC in overland flow). The importance of deeper flowpaths in the transport of inorganic C to streams is indicated by the 40:1 ratio of DIC:DOC for emergent groundwater. Dissolved CO2–C represented 92% of DIC in emergent groundwater. Results from this study illustrate a highly dynamic and tightly coupled linkage between the C cycle and the hydrologic cycle for both Ultisol and Oxisol landscapes: organic C fluxes strongly tied to flowpaths associated with quickflow, and inorganic C (particularly dissolved CO2) transported via deeper flowpaths.
KeywordsDissolved carbon dioxide Dissolved organic carbon Groundwater Overland flow Quickflow Stormflow
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The study was supported by NASA LBA-ECO grant to project group ND-11 and research grants from the Cornell University Program on Biogeochemistry and Center for the Environment to MSJ. The authors greatly appreciate the collaborations of field site hosts Rohden Indústria Lígnea Ltda. and Apolinário Stuhler. We thank Jeffrey Richey, Alex Krusche and Paulo Nunes for conceptual and logistical support, Mara Abdo for laboratory assistance, and Benedito Silveira de Andrade and Elielton Anterio da Souza for field assistance. Comments received from Todd Walter, Vishal Mehta and the anonymous reviewers were very helpful in the preparation of the manuscript.
- Butler J (1982) Carbon dioxide equilibria and their applications. Addison-Wesley, Reading, MassGoogle Scholar
- FAO-UNESCO (1987) Soils of the World. Elsevier Science Publishing Co. Inc, New YorkGoogle Scholar
- Gao B, Walter MT, Steenhuis TS, Parlange JY, Richards BK, Hogarth WL, Rose CW, Sander G (2005) Investigating raindrop effects on the transport of sediment and non-sorbed chemicals from soil to surface runoff. J Hydrol 308: 313–320Google Scholar
- Hewlett JD, Hibbert AR (1967) Factors affecting the response of small watersheds to precipitation in humid areas. In: Sopper WE, Lull HW (eds) International symposium on forest hydrology. Pergamon Press, New YorkGoogle Scholar
- Kirkby M, Callan J, Weyman D, Wood J (1976) Measurement and modeling of dynamic contributing areas in very small catchments, Working Paper No. 167. School of Geography University of Leeds, LeedsGoogle Scholar
- Mackereth F, Heron J, Talling J (1978) Water analysis: some revised methods for Limnologists. Freshwater Biological Association, Ambleside, UKGoogle Scholar
- McClain ME, Elsenbeer H (2001) Terrestrial inputs to Amazon streams and internal biogeochemical processing. In: McClain ME, Victoria RL, Richey JE (eds) The biogeochemistry of the Amazon Basin. Oxford University Press, Oxford, pp 185–208Google Scholar
- Ministry of Mines and Energy (Brazil) (1980) Projeto RADAMBRASIL. Folha SC. 21 - Juruena, Levantamento de Recursos Naturais, 20, Rio de JaneiroGoogle Scholar
- National Research Council (2004) Groundwater fluxes across interfaces. National Academies Press, Washington, DCGoogle Scholar
- Novães Filho JP (2005) Variabilidade espacial de atributos de solo em microbacias sob vegetação de floresta na Amazônia meridional. Universidade Federal de Mato Grosso, Cuiabá, Brazil, 120 ppGoogle Scholar
- Nunes PC (2003) Influência do efluxo de CO2 do solo na produção de forragem numa pastagem extensiva e num sistema agrosilvipastoril. MSc. Thesis, Universidade Federal de Mato Grosso, Cuiabá, 67 pp.Google Scholar
- Saxton K (2005) Soil water characteristic estimates by texture and organic matter for hydrologic solutions. USDA Agricultural Research Service, Pullman, WashingtonGoogle Scholar
- Soil Survey Staff (1999) Soil taxonomy: a basic system of soil classification for making and interpreting soil surveys. Agriculture Handbook # 436, USDA Natural Resource Conservation Service, Washington, DCGoogle Scholar
- Stumm W, Morgan JJ (1981) Aquatic chemistry. John Wiley & Sons, New YorkGoogle Scholar
- Turpin HW (1920) The carbon dioxide of the soil air. Cornell Univ Agric Exp Station Memoir 32:319–362Google Scholar
- Walter MT, Gerard-Marchant P, Steenhuis TS, Walter MF (2005) Closure to “Simple Estimation of Prevalence of Hortonian Flow in New York City Watersheds” by M. Todd Walter, Vishal K. Mehta, Alexis M. Marrone, Jan Boll, Pierre Gérard-Marchant, Tammo S. Steenhuis, and Michael F. Walter. J Hydrol Eng 10:169–170Google Scholar
- Wilks DS (1995) Statistical methods in the atmospheric sciences. Academic Press, San DiegoGoogle Scholar