1. 1 UIUC ATMOS 397G Biogeochemical Cycles and Global Change Lecture 10: Carbon Cycle Don Wuebbles Department of Atmospheric Sciences University of Illinois, Urbana, IL February 4, 2003

2. 2 UIUC Per capita Honduras – CO 2 Emissions

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8. 8 UIUC Why are plants green? Absorption spectrum of isolated chlorophyll and carotenoid species.

9. 9 UIUC Photosynthesis Photosynthesis occurs in organelles called CHLOROPLASTS 2 Stage Process Water vapor split  high energy molecules formed — 2H 2 O  4H + + O 2 (note production of O 2 ) — NADP  NADPH and ADP  ATP Reduction of CO 2 by H atoms — The Calvin Cycle Net: 6 CO 2 + 6H 2 O --------> C 6 H 12 O 6 + 6 O 2 (glucose)

10. 10 UIUC Photosynthesis: The Calvin cycle

11. 11 UIUC Photosynthesis Overview of photosynthetic processes as they occur in plants, algae, and cyanobacteria.

12. 12 UIUC Flow Chart for Photosynthesis Photosynthesis (Flow Chart)

13. 13 UIUC At night The light reactions of photosynthesis stop when the sun goes down. However, CO 2 fixation can continue as long as ATP and NADPH is available. In cacti and other succulents CO 2 uptake by the plant occurs primarily at night.

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15. 15 UIUC Respiration Respiration: oxidation of carbohydrate to CO 2 and H 2 0 in living cells is generally termed respiration Reverse reaction mechanism Approx. half of the gross carbon fixation by photosynthesis is used by the plants. As a result, actual rate of photosynthesis is about twice that which is measured by plant growth Respiration Photosynthesis Energy Released Stored Reactants Glucose CO2 and H2O Products CO2 and H2O Glucose

16. 16 UIUC Gross Primary Productivity – Europe (Jan 25 – Feb 1, 2001 From MODIS satellite instrument

17. 17 UIUC Net Primary Production NPP = Uptake of carbon by photolysis – autotrophic respiration losses by vegetation NPP = Gross Primary Production – plant respiration or NPP = GPP - R p Annual accumulation of organic matter per unit of land is a measure of NPP

18. 18 UIUC Net Ecosystem Productivity NEP = NPP – Respiration losses from soil NEP is an estimate of the carbon fluxes between the ecosystem and the atmosphere. The soil respiration losses are caused by the heterotrophic decomposition of soil organic litter.

19. 19 UIUC Major Terrestrial Biomes Savannah –Cabazo, Venezuala Desert – New Mexico Boreal Forest - Finland <> Tropical Forest - Malaysia

20. 20 UIUC Average annual Net Primary Productivity of the Earth's major biomes Ecosystem Type Net Primary Productivity (kilocalories/meter -2 /year) Tropical Rain Forest 9000 Estuary 9000 Swamps and Marshes 9000 Savanna 3000 Deciduous Temperate Forest 6000 Boreal Forest 3500 Temperate Grassland 2000 Polar Tundra 600 Desert < 200

21. 21 UIUC Factors Limiting NPP All plants require sunlight, carbon dioxide, and water for photosynthesis. Photosynthesis is also dependent on temperature and soil nutrients. Temperature (heat) controls the rate of plant metabolism which in turn determines the amount of photosynthesis that can take place. Most biological metabolic activity takes place within the range 0 to 50 degrees Celsius. There is little activity above or below this range. The optimal temperatures for productivity coincide with 15 to 25 degrees Celsius optimal range of photosynthesis. Shown is the relationship between the net primary productivity of forests with annual air temperature and precipiatation.

22. 22 UIUC IBIS Model – from Jon Foley

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