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Cornell University Universidade Federal do Mato Grosso

Significant seasonal and event-driven changes of carbon and nutrient fluxes to first-order streams of an Amazon forest. Mark S. Johnson, Johannes Lehmann, Evandro Carlos Selva, Eduardo Guimarães Couto, Mara Abdo, Erick C.M. Fernandes, Susan Riha. Cornell University

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Cornell University Universidade Federal do Mato Grosso

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  1. Significant seasonal and event-driven changes of carbon and nutrient fluxes to first-order streams of an Amazon forest Mark S. Johnson, Johannes Lehmann, Evandro Carlos Selva, Eduardo Guimarães Couto, Mara Abdo, Erick C.M. Fernandes, Susan Riha Cornell University Universidade Federal do Mato Grosso

  2. Why study tiny catchments? • Clearly reflect land surface processes • Important measurements for determining C balances and fluxes across interfaces • Once you get a bit (~50 m) downstream, instream processes begin to strongly influence the aquatic picture

  3. Juruena, MT Site Description • Four perennial headwater catchments • Small streams originating as seeps (minas d’agua ou nacentes)

  4. 0 100 mm d-1 throughfall 200 Jun-03 Aug-03 Oct-03 Dec-03 Feb-04 Apr-04 Jun-04 Juruena, MT Site Description • Four perennial headwater catchments • Small streams originating as seeps (minas d’agua ou nacentes)

  5. Streamwater pH- Seasonal Dynamics • As dry season progresses, streamflow pH rises. • Hypothesis: High GPP during rainy-season leads to higher soil CO2, and lower ground-water and stream water pH. mm d-1 100 n=4 watersheds

  6. Electrical Conductivity- Seasonal Dynamics 0 100 • As dry season progresses, streamflow becomes more concentrated • Streamflow becomes more dilute as rainy season progresses. n=4 watersheds

  7. Carbon fluxes to forest floor • For period presented, 23X more C fell as litter than as DOC in throughfall • Selva et al., 2004 LBA poster 27.7-P for C in litterfall fractions

  8. DOC concentrations in surface runoff (enchurrada) 70 0 60 100 50 200 40 30 20 10 0 01-Sep-03 01-Nov-03 01-Jan-04 01-Mar-04 01-May-04 • Litter build up during dry season leads to very large DOC values for surface runoff • Throughfall-DOC followed a similar pattern DOC (mg L-1) Mean ± SE, n=4 watersheds

  9. Surface ponding- late in wet season

  10. 0 100 DOC stream export Rainfall (mm d-1) Discharge (vazão) Rainfall (mm d-1) 200 300 Discharge (x 103 L day-1) and DOC flux (g day-1) 200 100 0 01-Sep-03 01-Nov-03 01-Jan-04 01-Mar-04 01-May-04 DOC flux Discharge Rainfall-discharge-DOC flux relationship • High surface DOC concentrations during dry to wet transition leads to high DOC export • Lower surface DOC concentrations during late rainy season leads to lower DOC export

  11. Baseflow and storm flow DOC

  12. Baseflow and storm flow CPOC • Intact leaves transported during baseflow • Fragmented material transported during storm flow Evandro Selva et al., 2004, LBA poster 27.7-P

  13. Rapid surface runoff, rapid stream response 0 rainfall 10 20 Rainfall (mm) per 5 minutes Discharge (L s-1) 20 Discharge 0 13:00 14:00 15:00 16:00 Time of Day, 28 April 2004 Overland flow present Percolation present at 10 cm

  14. Electrical Conductivity Dissolved Oxygen pH Storm dynamics- pH, DO, EC • Storm water shows initial surficial contribution • Then, increasing contribution of subsurface lateral flow • More anoxic • More acidic • More dilute • Groundwater seeps • pH = 4.56 • EC = 7 µS cm-1 28 April 2004, Watershed 2

  15. Lateral flow delivering CO2 pulse • Initial CO2 decrease due to surface contributions • Storm water pulse of free CO2 flushed out of soil profile with interflow (rapid subsurface flow) 8000 Discharge CO (aq) 2 6000 CO2(aq) ppm ) -1 4000 CO2(aq) ppm 20 2000 Discharge (L s-1) 10 0 0 12:00 13:00 14:00 15:00 16:00 17:00 28 April 2004, Watershed 2

  16. Terrestrial-aquatic organic C flux DOC 84.6% POC 12.1% CPOC 3.3% Dissolved C exports are 5.5X solid C exports Jan - May 2004

  17. Large losses of CO2 from emergent groundwater Johnson et al. (unpublished data) 35000 30000 25000 20000 Forested Ultisol-Oxisol Southern Amazon, Juruena, MT N=30 (from 4 watersheds) pCO2 (ppm) 15000 10000 y=24489.9/(1+0.1189X) 5000 r=0.79 0 0 20 40 60 80 100 120 140 160 2500 Distance from spring (m)

  18. Solid Phase CO2-C outgas evasion 1.2% 66.0% POC 0.9% DOC 6.6% CPOC 0.3% HCO3- C CO2-C(aq) 15.7% 10.5% Terrestrial-aquatic C flux components Jan - May 2004

  19. Conclusions • Solid inputs >> dissolved inputs • Gaseous outputs >> dissolved outputs >> solid outputs • Aboveground DOC fluxes become more dilute over the course of the wet season • If soil DOC are in equilibrium, aboveground fluxes are important driver of variability within DOC system • Nested temporal scales are an important feature of the terrestrial-aquatic interface

  20. Agradecimentos • LBA and organizing committee • Rohden Indústria Lígnea Ltda. for site access and support (parabens pela sua certificação!) • Jeff Richey, Alex Krusche and Paulo Nunes for conceptual and logistical support • Benedito Silveira de Andrade and Elielton Anterio da Souza for field assistance • Ao povo Brasileiro e Juruenense

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