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

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

5. Streamwater pH- Seasonal Dynamics As dry season progresses, streamflow pH rises. Hypothesis: High GPP during rainy- season leads to higher soil CO 2, and lower ground- water and stream water pH. n=4 watersheds 100 mm d -1

6. Electrical Conductivity- Seasonal Dynamics 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. Mean ± SE, n=4 watersheds DOC concentrations in surface runoff (enchurrada) 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 )

9. Surface ponding- late in wet season

10. Rainfall-discharge-DOC flux relationship DOC flux Discharge Rainfall (mm d - 1 ) 01-Sep-0301-Nov-0301-Jan-0401-Mar-0401-May-04 0 100 200 0 100 200 300 Discharge (x 10 3 L day -1 ) and DOC flux (g day -1 ) Rainfall (mm d -1 ) DOC stream export Discharge (vazão) 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 DOC (mg/L) BaseflowStorm flowRatio Oct-035.710.0 1.7 Nov-033.19.9 3.2 Dec-032.47.5 3.1 Jan-042.17.3 3.5 Feb-041.95.8 3.1 Mar-041.13.6 3.3 Apr-040.73.8 5.3

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

14. 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 pH Dissolved Oxygen Electrical Conductivity

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

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

17. Large losses of CO2 from emergent groundwater Forested Ultisol-Oxisol Southern Amazon, Juruena, MT N=30 (from 4 watersheds) Distance from spring (m) 0204060801001201401602500 0 5000 10000 15000 20000 25000 30000 35000 y=24489.9/(1+0.1189X) r=0.79 pCO 2 (ppm) Johnson et al. (unpublished data)

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

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

21. Large losses of CO2 from emergent groundwater Forested Ultisol-Oxisol Southern Amazon, Juruena, MT N=30 (from 4 watersheds)