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The role of Amazonian fluvial systems in regional and global carbon cycles: CO2 evasion and land-water interactions


The humid tropics play an important but ambiguous role in the global carbon cycle. While deforestation has been estimated to release about 1.6 Gt C y-¹ (HOUGHTON, 2000), mature Amazon rainforests appear to sequester carbon (act as a sink), but of an uncertain magnitude. Current estimates of sequestration have wide variation between different types of measurements, ~1,3 Mg C.ha-¹ yr-¹ based on the accumulation of biomass and soils (PHILLIPS et aI., 1998; CHAMBERS et aI., 2001; TRUMBORE, 2000) to 1.0 to > 5.9 Mg C ha-¹ y-¹ based on eddy covariance measurements (FAN et al. 1990; GRACE et al. 1995; MALHI et al. 1998). However, recent calculations from global atmospheric inverse modeling imply that the net carbon exchange of the tropics with the atmosphere is about zero (SCHIMEL et al.; 2001). Discrepancies between these estimates of carbon sequestration rates may be due in part to methodological issues and integration times of methods. However, it is also possible that at least part of the carbon fixed in the upland could be "exported” in fluxes not yet quantified. In fact, preliminary results (RICHEY et al., 2002) show that evasive fluxes of C02 from aquatic systems of the Amazon can account for as much as the lower estimate of carbon sequestration by "terra firme" forests in the central part of the basin. In this project we hypothesize that "CO2 evasion returns as much carbon to the atmosphere as is sequestered in upland forests on an interannual basis and the export of organic material from upland forests to fluvial environments is the primary source of carbon that is eventually respired in rivers and evaded as CO2”. To test it, we intend to: 1) conduct fieldwork in characteristic sub basins to obtain an extensive suite of pC02 distribution measurements over the hydrologic regime; 2) use proven geochemical techniques (gas flux measurements, isotopic tracers, demineralization rates) to quantify the rates of the lateral transfer and cycling of water and bioactive organic matter from the land, through riparian environments and to the river system and; 3) use a terrestrial source/river transport and reaction model to synthesize and extrapolate the site-specific C02 evasion rate measurements to a basin-wide estimate of C02 evasion rate. This project consolidates and extends the scientific and educational activities of this group in fluvial systems of the Amazon, started 20 years ago with a successful cooperation between Centro de Energia Nuclear na Agricultura, Instituto Nacional de Pesquisas da Amazônia and University of Washington, Seattle, USA, and which was followed by the thematic project "Changes in organic matter dynamics in micro and meso-scale rivers of Rondônia, as a function of changes in land cover" Its feasibility is also assured by various cooperation within LBA (NASA), with the University of Washington and the Marine Biological Laboratory (Woods Hole, MA, USA) and within the Millennium Institute (CNPq), with several research institutions in the Amazon. (AU)

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Scientific publications (17)
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
REMINGTON‚ S.M.; STRAHM‚ B.D.; NEU‚ V.; RICHEY‚ J.E.; DA CUNHA‚ H.B.. The role of sorption in control of riverine dissolved organic carbon concentrations by riparian zone soils in the Amazon basin. SOIL SCIENCE, v. 172, n. 4, p. 279-291, . (03/13172-2)
RICHEY, JEFFREY E.; BALLESTER, MARIA VICTORIA; DAVIDSON, ERIC A.; JOHNSON, MARK S.; KRUSCHE, ALEX V.. Land-Water interactions in the amazon. BIOGEOCHEMISTRY, v. 105, n. 1-3, p. 1-5, . (03/13172-2, 08/58089-9)
NEILL, CHRISTOPHER; CHAVES, JOAQUIN E.; BIGGS, TRENT; DEEGAN, LINDA A.; ELSENBEER, HELMUT; FIGUEIREDO, RICARDO O.; GERMER, SONJA; JOHNSON, MARK S.; LEHMANN, JOHANNES; MARKEWITZ, DANIEL; et al. Runoff sources and land cover change in the Amazon: an end-member mixing analysis from small watersheds. BIOGEOCHEMISTRY, v. 105, n. 1-3, p. 7-18, . (03/13172-2)
NEU, VANIA; NEILL, CHRISTOPHER; KRUSCHE, ALEX V.. Gaseous and fluvial carbon export from an Amazon forest watershed. BIOGEOCHEMISTRY, v. 105, n. 1-3, p. 133-147, . (03/13172-2)
HAYHOE, SHELBY J.; NEILL, CHRISTOPHER; PORDER, STEPHEN; MCHORNEY, RICHARD; LEFEBVRE, PAUL; COE, MICHAEL T.; ELSENBEER, HELMUT; KRUSCHE, ALEX V.. Conversion to soy on the Amazonian agricultural frontier increases streamflow without affecting stormflow dynamics. GLOBAL CHANGE BIOLOGY, v. 17, n. 5, p. 1821-1833, . (03/13172-2)
GARCIA, ANDREA S.; SAWAKUCHI, HENRIQUE O.; FERREIRA, MANUEL EDUARDO; BALLESTER, MARIA VICTORIA R.. Landscape changes in a neotropical forest-savanna ecotone zone in central Brazil: The role of protected areas in the maintenance of native vegetation. Journal of Environmental Management, v. 187, p. 16-23, . (03/13172-2)
NEU, VANIA; WARD, NICHOLAS D.; KRUSCHE, V, ALEX; NEILL, CHRISTOPHER. Dissolved Organic and Inorganic Carbon Flow Paths in an Amazonian Transitional Forest. FRONTIERS IN MARINE SCIENCE, v. 3, . (03/13172-2)
LEITE, NEI K.; KRUSCHE, ALEX V.; BALLESTER, MARIA V. R.; VICTORIA, REYNALDO L.; RICHEY, JEFFREY E.; GOMES, BEATRIZ M.. Intra and interannual variability in the Madeira River water chemistry and sediment load. BIOGEOCHEMISTRY, v. 105, n. 1-3, p. 37-51, . (03/13172-2)
ALIN, SIMONE R.; RASERA, MARIA DE FATIMA F. L.; SALIMON, CLEBER I.; RICHEY, JEFFREY E.; HOLTGRIEVE, GORDON W.; KRUSCHE, ALEX V.; SNIDVONGS, ANOND. Physical controls on carbon dioxide transfer velocity and flux in low-gradient river systems and implications for regional carbon budgets. JOURNAL OF GEOPHYSICAL RESEARCH, v. 116, . (03/13172-2, 03/07778-5)
GERMER, SONJA; NEILL, CHRISTOPHER; KRUSCHE, ALEX V.; ELSENBEER, HELMUT. Influence of land-use change on near-surface hydrological processes: Undisturbed forest to pasture. Journal of Hydrology, v. 380, n. 3-4, p. 473-480, . (03/13172-2)
CHAVES, JOAQUIN; NEILL, CHRISTOPHER; GERMER, SONJA; NETO, SERGIO GOUVEIA; KRUSCHE, ALEX V.; BONILLA, ADRIANA CASTELLANOS; ELSENBEER, HELMUT. Nitrogen Transformations in Flowpaths Leading from Soils to Streams in Amazon Forest and Pasture. ECOSYSTEMS, v. 12, n. 6, p. 961-972, . (03/13172-2)
GERMER, SONJA; ZIMMERMANN, ALEXANDER; NEILL, CHRISTOPHER; KRUSCHE, ALEX V.; ELSENBEER, HELMUT. Disproportionate single-species contribution to canopy-soil nutrient flux in an Amazonian rainforest. FOREST ECOLOGY AND MANAGEMENT, v. 267, p. 40-49, . (03/13172-2)
GERMER, SONJA; NEILL, CHRISTOPHER; VETTER, TOBIAS; CHAVES, JOAQUIN; KRUSCHE, ALEX V.; ELSENBEER, HELMUT. Implications of long-term land-use change for the hydrology and solute budgets of small catchments in Amazonia. Journal of Hydrology, v. 364, n. 3-4, p. 349-363, . (03/13172-2)
DE FÁTIMA FL RASERA‚ M.; BALLESTER‚ M.V.R.; KRUSCHE‚ A.V.; SALIMON‚ C.; MONTEBELO‚ L.A.; ALIN‚ S.R.; VICTORIA‚ R.L.; RICHEY‚ J.E.. Estimating the surface area of small rivers in the southwestern Amazon and their role in CO2 outgassing. Earth Interactions, v. 12, n. 6, p. 1-16, . (99/01159-4, 03/13172-2)
CHAVES‚ J.; NEILL‚ C.; GERMER‚ S.; NETO‚ S.G.; KRUSCHE‚ A.; ELSENBEER‚ H.. Land management impacts on runoff sources in small Amazon watersheds. Hydrological Processes, v. 22, n. 12, p. 1766-1775, . (03/13172-2)
RISKIN, SHELBY H.; NEILL, CHRISTOPHER; JANKOWSKI, KATHIJO; KRUSCHE, ALEX V.; MCHORNEY, RICHARD; ELSENBEER, HELMUT; MACEDO, MARCIA N.; NUNES, DARLISSON; PORDER, STEPHEN. Solute and sediment export from Amazon forest and soybean headwater streams. Ecological Applications, v. 27, n. 1, p. 193-207, . (03/13172-2)

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