1. On the Role of River Systems in the Global Carbon Cycle (with a Twist) J. Richey March 12

2. RIVERS IN THE GLOBAL CONTEXT Riverine C CycleThe River Continuum … a strategy for taking basic science information and translating it into water resource information and management at regional scales

3. GLOBAL RIVER C CYCLE VEGETATION SOILS (+) ATMOSPHERIC CO2 Active SOM,NP (1-2y) Int. SOM,NP (20-40y) Pass, SOM,NP (1000y) Litter COASTAL OCEAN SHELF SEDIMENTS ~.4 aw DOC UV Ox?.1 cw, ~.4aw.1 cw, ~.4aw.2 MCO3.2 S&S gigatons/y cw = conventional wisdom aw = alternate wisdom S&S = sensu Sarmiento & Sundquist (+) anthro. effect RIVERS ESTUARIE S ANTHROPOGENIC N,P, Toxics (+:1.8+1.1) (P Desorp) PPR PPT ->Q DAMS RIPARIAN (1)CO2+H20+M(C,Si)O3- >M+2HCO3 (2) SOM->CO2 erosion, PPr leaching DIC (pCO2,HCO3) POC (.5uM - 1mm) DOC (%s <.5uM) Q (N,P,Toxics).4 (+).2 cw.5aw(++).2 (~).1 cw, ~.4aw COASTAL OCEAN

4. POC Loading by Geographic Region (Tg/y) A SEAs Discharge 1.3 M m 3 /s Ocn Sediment Transport 31,000 MT/y A SEAs

5. Are the Humid Tropics a Source or Sink of C? Uptake (Towers) 3-8 Mg C ha -1 y -1 Biomass Accumulation (long-term plots).7 ±.4 Soil Accumulation (long-term plots).6 ±.3 Deforestation 1-2 Pg y -1 (?) “…that leaks out of the forest in forms that are not usually measured, … Although this C leakage is thought to be relatively small, surprises cannot be ruled out.” Malhi and Grace (2000) VOC (??) Dissolved C TOC Export (to the Sea) Global.4 -.8 Pg y -1 Amazon 36 Tg y -1 (.06 Mg C ha -1 y -1 ) CO 2 EVASION Amazon Mainstem 15 Tg y -1 River Corridors ?????

6. NPP Evasion (i,t) = km 2 * D(pCO 2 ‑ C eq )/z Richey et al. (in press). Nature.

8. Streams (< 100 m in width)

9. 15 0 5 10 20 25 JFMAMJJASOND Flooded Area (x 10 4 km 2 ) T (>100m) MC S (<100 m)MF Inundation in Amazon Rivers 10 15 20 25 % 1.77 x 10 6 km 2

10. JFMAMJJASOND 0 4 8 Man pCO 2 (x 10 3  atm) Dissolved Carbon Dioxide in Amazon Rivers 0 4 8 12 Man Jt Jr Sol Ic Md Pr Ng Jp atm

11. 15 0 5 10 20 25 30 JFMAMJJASOND CO 2 Evasion (Tg C mo -1 ) T (>100m) S (<100 m) MF MC  : 1.2 ±. 3 Mg C ha -1 y -1 (basin ~.5 Gt y -1 ) CO 2 Evasion from Waters of the Central Amazon

12. POTENTIAL CO 2 SOURCES ~ 1. 2 Mg C ha -1 y -1 0.0 0.4 0.6 Litterfall Plankton Macrophytes Soil DOC Soil CO 2 0.2

13. Extrapolation to Humid Tropics: ~0.9 Gt y -1 (3x > previous global)

14. Schimel et al. (2001) Gurney et al. (2002) Zonal distribution of terrestrial and oceanic C (deduced from inverse models using different techniques and sets of atmospheric data, corrected for anthropogenic emissions) “… A return flux from water to the atmosphere of this (0.9) magnitude comes closer to reconciling independent carbon budgets for the tropics.”