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Carbon balance – overview Bio 164/264 January 25, 2007 Chris Field

Carbon balance – overview Bio 164/264 January 25, 2007 Chris Field. How do plants fix atmospheric CO 2 into organic compounds? What happens to the carbon after it is fixed in photosynthesis? How is the CO 2 fixed in photosynthesis returned to the atmosphere?

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Carbon balance – overview Bio 164/264 January 25, 2007 Chris Field

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  1. Carbon balance – overviewBio 164/264January 25, 2007Chris Field • How do plants fix atmospheric CO2 into organic compounds? • What happens to the carbon after it is fixed in photosynthesis? • How is the CO2 fixed in photosynthesis returned to the atmosphere? • What controls the storage of carbon in plants and soils? Behrenfeld et al. Science 2001

  2. Sabine et al. 2004 SCOPE 62

  3. Carbon cycle (big picture perspective) • What explains carbon sources and sinks? • How important are ecosystem versus anthropogenic fluxes? • How will carbon sources and sinks change in the future? • How will these changes influence the trajectory of climate change?

  4. Components of the carbon cycle • GPP = photosynthesis by autotrophs • measure with gas exchange • Ra = respiration by autotrophs • Measure with gas exchange • NPP = net growth by autotrophs = GPP – Ra • food available for consumers • Measure with harvest or harvest surrogate • Rh = respiration by heterotrophs • Measure with gas exchange • NEP = net change in local carbon storage (land) • Often conceived as including little or no influence from disturbance, especially combustion (NPP- Rh) • Measure with repeated inventories or whole system gas exchange • NBP = regional change in carbon storage • NEP minus losses to fire, harvest, and other disturbance • Measure with repeated inventories • Export production = transfer of NPP to deep waters (ocean) • NPP minus heterotrophic respiration • Biological pump, Bicarbonate pump, Alkalinity Pump • Facilitate the movement of carbon from surface to deeper waters

  5. Why so much interest in the carbon cycle? • Climate change: • Food: • Understanding the world we live in:

  6. Global carbon budgets for the decades of 1980s and 1990s Schimel et al. 2001

  7. Localizing the sink: Ocean vs. LandTraditional approach: deconvolution/reconstruction Reconstruction : emissions from historical record of human activities Deconvolution : land uptake = emissions - atm increase - ocean uptake Combination: “Missing” sink = reconstruction - deconvolution

  8. Localizing the land sink: N-S CO2 gradient • The observed gradient is shallower than expected from the distribution of fossil fuel and land use. • Tans et al. 1990 • W-E mixing is so rapid that meridional gradients are very difficult to detect.

  9. Annual uptake by the land is highly variable Canadell et al. 2007 ms

  10. GPP • 6 CO2 + 12 H2O + light → C6H12O6 + 6 O2 + 6 H2O • carbon dioxide + water + light energy → glucose + oxygen + water • n CO2 + 2n H2O + ATP + NADPH → (CH2O)n + n H2O + n O2

  11. Ra • What is respiration? • Consumption of carbohydrate to release CO2 and generate reducing equivalents • Glycolysis and Krebs cycle • In mitochondria • Consumption of O2 and reducing equivalents to produce ATP • In mitochondria • 2 different oxidases with very different efficiencies • Fundamentally different from photorespiration • Provides the energy for biosynthesis, turnover, ion pumping --- life • Provides carbon skeletons for biosynthesis • Can occur in light or dark • May be suppressed in light

  12. McCree – de Wit – Penning de Vries – Thornley Paradigm • Respiration powers growth and maintenance • Growth component should be proportional to growth rate • With a growth efficiency that depends on the cost of the tissues • Maintenance component proportional to demands for: • Protein turnover • Maintenance of ion gradients • R = RG + RM = gRG + mRM where G and M refer to growth and maintenance • G = YG(P-RM) =YGP – YGmRW (Thornley 1970) • Some models add a wastage term for futile cycles and other inefficiencies

  13. Complementary approaches • McCree: Measure growth and respiration under conditions that allow an empirical separation • Penning de Vries: Trace known biochemical pathways to calculate potential costs dR/dG = growth coef Specific respiration rate (g g-1) Maintenance resp Specific growth rate (g g-1)

  14. Penning de Vries • Construction costs • Component processes • NO3- & SO42- reduction • Active uptake • Monomer synthesis • Polymerization • Tool maintenance • Active mineral uptake • Phloem loading • starch 1.1 g glucose/g product (YG =0.91) • Protein: 1.5 g glucose/g product (YG = 0.67) • Lipid: 3 g glucose/g product (YG = 0.33) • Maintenance costs • Protein breakdown: 0.13-2 ATP/amino acid • Protein synthesis: 4.5-5.9 ATP/amino acid • Can be related to tissue N: R = gRG + mR,NN

  15. Alternative oxidase • 1st observed in thermogenic plants • Tissues warm as a result of high respiration • Pollinator attraction: usually foul-smelling • Insensitive to cyanide • A powerful inhibitor of cytochrome c oxidase • Energy coupling efficiency only 1/3 of cytochrome c pathway • Gene in all angiosperms, many algae, and some fungi

  16. Thermogenic respiration Seymour, R. S., Gibernau, M. & Ito, K. Thermogenesis and respiration of inflorescences of the dead horse arum Helicodiceros muscivorus, a pseudo-thermoregulatory aroid associated with fly pollination.Functional Ecology17 (6), 886-894.doi: 10.1111/j.1365-2435.2003.00802.x

  17. NPP • Major controls from • Growing season length • Water • Temperature • Nutrients

  18. Baldocchi and Valentini 2004 SCOPE 62

  19. NPP • A simple model for large scale estimates • NPP = APAR•e = FPAR•PAR•e • Where APAR = absorbed photosynthetically active radiation • e = light us efficiency • FPAR = fraction of PAR absorbed • Monteith demonstrated that for many crops grown under ideal conditions, e is close to 1.4 g biomass per mJ absorbed solar radiation • Wide range of e under naturalconditions Joel et al 1997

  20. Mean annual terrestrial NPP from 16 models: ~ 55 Pg C yr-1 NPP g C m-2 yr-1 Cramer et al. GCB 1999

  21. Global Primary Production: 9/97 – 8/00

  22. Rh • Dominated by microorganisms – bacteria and fungi • Can be aerobic or anaerobic

  23. Rh • Usually modeled as proportional to soil organic matter • Soil organic matter often conceptualized as pools with distinct turnover times • Metabolic C: a few days to weeks • Active C: a few months to years • Slow C: several years to decades • Passive C: many centuries • Influence of temperature, moisture, & “quality” • Quality increases with amount of good stuff (e.g. N) and decreases with amount of bad stuff (e.g. lignin)

  24. Parton et al. Science 2007

  25. NEP/NBP and carbon sinks • In general, an increase in NPP will produce net C storage • Amount of storage increases with amount of NPP increase • Amount of storage increases with turnover time of recipient pools • Allocation to wood leads to substantial storage • Allocation to exudate leads to little

  26. In the US:Forests may not dominate land sinks • Apparent sink: 0.4 –0.7 Pg/yr • “Real” sink: 0.3-0.6 Pg/yr • Forest fraction: 30% • Aquatic fraction 13% • Pacala et al. Science 2001

  27. For your reading pleasure • Field, C. B., M. J. Behrenfeld, J. T. Randerson, and P. Falkowski, 1998: Primary production of the biosphere: Integrating terrestrial and oceanic components. Science, 281, 237-240. • Behrenfeld, M. J., J. T. Randerson, C. R. McClain, G. C. Feldman, S. O. Los, C. J. Tucker, P. G. Falkowski, C. B. Field, R. Frouin, W. E. Esaias, D. D. Kolber, and N. H. Pollack, 2001: Biospheric primary production during an ENSO transition. Science, 291, 2594-2597. • Pacala, S. W., G. C. Hurtt, D. Baker, P. Peylin, R. A. Houghton, R. A. Birdsey, L. Heath, E. T. Sundquist, R. F. Stallard, P. Ciais, P. Moorcroft, J. P. Caspersen, E. Shevliakova, B. Moore, G. Kohlmaier, E. Holland, M. Gloor, M. E. Harmon, S. M. Fan, J. L. Sarmiento, C. L. Goodale, D. Schimel, and C. B. Field, 2001: Consistent land- and atmosphere-based US carbon sink estimates. Science, 292, 2316-2319. • Schimel, D. S., J. I. House, K. A. Hibbard, P. Bousquet, P. Ciais, P. Peylin, B. H. Braswell, M. J. Apps, D. Baker, A. Bondeau, J. Canadell, G. Churkina, W. Cramer, A. S. Denning, C. B. Field, P. Friedlingstein, C. Goodale, M. Heimann, R. A. Houghton, J. M. Melillo, B. Moore, D. Murdiyarso, I. Noble, S. W. Pacala, I. C. Prentice, M. R. Raupach, P. J. Rayner, R. J. Scholes, W. L. Steffen, and C. Wirth, 2001: Recent patterns and mechanisms of carbon exchange by terrestrial ecosystems. Nature, 414, 169-172. • Gruber, N., P. Friedlingstein, C. B. Field, R. Valentini, M. Heimann, J. E. Richey, P. Romero-Lankao, E.-D. Schulze, and C.-T. A. Chen. 2004: The vulnerability of the carbon cycle in the 21st century: An assessment of carbon-climate-human interactions. in The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World, C. B. Field and M. R. Raupach, Eds. Island Press, Washington. 45-76. • Sabine, C. L., M. Heiman, P. Artaxo, D. C. E. Bakker, C.-T. A. Chen, C. B. Field, N. Gruber, C. LeQuéré, R. G. Prinn, J. E.Richey, P. Romero-Lankao, J. A. Sathaye, and R. Valentini. 2004: Current status and past trends of the carbon cycle. in The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World, C. B. Field and M. R. Raupach, Eds. Island Press, Washington. 17-44. • Prentice, I. C. 2001: The carbon cycle and atmospheric carbon dioxide. in Climate Change 2001: The Scientific Basis (Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change). • Tans, P. P., I. Y. Fung, and T. Takahashi, 1990: Observational constraints on the global CO2 budget. Science, 247, 1431-1438.

  28. More readings • Baldocchi, D., and R. Valentini. 2004: Geographic and temporal variation of carbon exchange by ecosystems and their sensitivity to environmental perturbations. in The Global Carbon Cycle: Integrating Humans, Climate, and the Natural World, C. B. Field and M. R. Raupach, Eds. Island Press, Washington. 295-316. • Cramer, W., D. W. Kicklighter, A. Bondeau, B. M. III, G. Churkina, B. Nemry, A. Ruimy, A. L. Schloss, J. Kaduk, and participants of the Potsdam NPP Model Intercomparison, 1999: Comparing global models of terrestrial net primary productivity (NPP): overview and key results. Global Change Biology, 5 supplement, 1-15. • Parton, W., W. L. Silver, I. C. Burke, L. Grassens, M. E. Harmon, W. S. Currie, J. Y. King, E. C. Adair, L. A. Brandt, S. C. Hart, and B. Fasth, 2007: Global-Scale Similarities in Nitrogen Release Patterns During Long-Term Decomposition. Science %R 10.1126/science.1134853, 315, 361-364.

  29. http://www.epa.gov/globalwarming/ What is our contribution to greenhouse gases? U.S.: 6.6 metric tons carbon per person per year Range of US uptake 5.3 metric tons C from CO2 per person per year = 19.6 metric tons CO2 per person per year

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