1. Export of organic carbon from Igarape Asu, Central Amazonia M.J. Waterloo A.D. Nobre W.W.P. Jans L.A. Cuartas T. Pimentel D.P. Drucker I. Langedijk S.M. Oliveira D.P. Drucker M.G. Hodnett J. Tomasella J.C. Munero A.C. de Araujo

2. Carboncycle-Ecocarbon projects To quantify the water and nutrient cycles of micro-scale rainforest catchment To quantify the amount of the carbon lost from this catchment via hydrological pathways To assess the sensitivity of the carbon cycle to changes in the soil moisture status, with emphasis on soil respiration

3. Asu catchment, Cuieiras Reserve INPA Area: 6.8 km 2 Elevation: 35-100 m a.s.l.

4. Measurements used Above canopy rainfall (4 locations) Stream water level and flow velocity (Doppler) Groundwater levels Electrical conductivity (EC), pH, UV-Vis spectra (DOC), fine particulate organic matter outflow and its carbon content Annual fluxes presented here calculated from daily averages and totals

5. UV-Vis spectra rainfall – stream water

6. DOC and sediment C concentrations Rainfall:1.3 mg l -1 Delayed flow:8-15 mg l -1 Quickflow:15-28 mg l -1 Shallow groundwater (spodosol):32 mg l -1 Deep groundwater (oxisol):<2.0 mg l -1 Percentage carbon in suspended sediment: 28%

7. Discharge versus DOC concentration

8. DOC export versus Discharge

9. DOC export in quick and delayed flow

10. Rainfall, stream runoff and C exports YearP (mm) Q (mm) C P (g m -2 ) C Q (g m -2 ) C net (g m -2 ) 2002297614553.929.425.5 200320538352.713.210.5 Average251511453.321.818.0 Maximum daily C export: 1.1 g m -2 Carbon export in quickflow: 56-68% of total Carbon export in suspended form: 10-13% of total

11. Conclusions Carbon export in stream mainly from the valley spodosols Exports are quite similar to those observed for the Rio Negro River Basin (Richey et al., 1990; Moreira-Turcq et al., 2003), combined estimate: 16.5 g m -2 at 1213 mm discharge Stream C export represents up to 20% of tower CO 2 flux estimates Export of inorganic carbon (pCO 2 ) not yet included