Understanding Photosynthesis and Carbon Cycling in Terrestrial Ecosystems

1. Photosynthesis

2. The TerrestrialCarbonCycle

3. Photosynthesis (GPP) Dark Respiration in Leaves Net Photosynthesis Storage as Carbohydrates Plant Biomass Growth Respiration Maintenance Respiration

4. PSN (Photosynthesis) GPP= PSN – Raleaf (Gross Primary Production) NPP = GPP – Ra(Net Primary Production) NEP =NPP – Rh (Net Ecosystem Production) Raleaf NBP = NEP - disturbance (Net Biosphere Production) Ra = R growth + R maintenance (Autotrophic Respiration) Rh = R microbe + R herbivore (HeterotrophicRespiration) Harvest/Fire Carbon Budget Components

5. O2 CO2 CO2 O2 SUGARS AND OTHER ORGANIC MOLECULES H2O H2O PHOTOSYNTHESIS CO2 + H2O  O2 + SUGARS RESPIRATION SUGARS + O2 H2O + CO2 PLANTS ALGAE SOME BACTERIA MOST LIVING ORGANISMS ENERGY OF SUNLIGHT USEFUL CHEMICAL BOND ENERGY

6. CO2 + H2O + (e) CH2O + ½ O2 • Basic Components of Photosynthesis • PAR Interception • ATP • Biochemistry (Rubisco) • Ribulose bisphosphate (RuBP) • Absorption of CO2 • CO2 diffuses at 0.625 * H2O because of difference in molecular mass 6CO2 + 12H2O + (e) C6H12O6 + 6O2 + 6H2O

7. Electro-Magnetic Spectrum

8. CO2 Compensation Point (Γ) • The point at which the rate of photosynthesis equals the rate of respiration of a leaf is the CO2 compensation point. • The CO2 compensation point is affected by: • Temperature • O2 • Water stress

9. Light Saturated Rates 150 Aspen – sun leaf 100 Oak – sun leaf Net Photosynthesis (nmol g-1 s-1) Aspen – shade leaf 50 Oak – shade leaf 0 Compensation Points -50 0 0.25 0.50 0.75 1.0 Fraction of full sunlight CO2 Compensation Point (Γ) Fig. 18.1 p. 490

10. Sun and Shade Leaves – American beech sun leaf shade leaf Fig. 6-12 p. 105

11. 100% 50% 25% 12.5% 6.25% Leaf Area Index (LAI)

12. Beer’s Law IRad = Io e-k(LAI) k = 0.5 About half of the remaining light is absorbed by each layer of leaves

13. Corticularand WoodPhotosynthesisPfanz et al. (2002)

14. Water Potential and Carbon Uptake Fig. 18.4 p. 493

15. Gross Photosynthesis Photosynthesis  Respiration  Cold Limit Heat Limit -10 0 10 20 30 40 50 60 Temperature (C) Effects of Temperature Leaf Respiration Topt Similar to Fig. 18.3 p. 492

16. Leaf Nitrogen Fig. 18.5 p. 494

17. Redrawn from Kolke et al. 1991

18. 1000 1000 100 100 Net photosynthesis (mmol g-1 s-1) 10 10 1 7 21 63 10 70 490 1 10 100 Leaf nitrogen (mg g-1) Specific leaf area (cm2 g-1) Leaf life-span (months) 1

19. Potential vs. Actual GPP

21. Month Month Month J J J J J J J J J F F F F F F F F F M M M M M M M M M A A A A A A A A A M M M M M M M M M J J J J J J J J J J J J J J J J J J A A A A A A A A A S S S S S S S S S O O O O O O O O O N N N N N N N N N D D D D D D D D D 100 100 100 100 100 100 100 100 Alaska Colorado Oregon 80 80 80 80 80 80 80 80 60 60 60 60 60 60 60 60 40 40 40 40 40 40 40 40 Growing Season 20 20 20 20 20 20 20 20 Growing Season Growing Season 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 60 60 60 60 60 60 60 60 60 120 120 120 120 120 120 120 120 120 180 180 180 180 180 180 180 180 180 240 240 240 240 240 240 240 240 240 300 300 300 300 300 300 300 300 300 360 360 360 360 360 360 360 360 360 100 Utah Idaho Oregon 80 Simulated Photosynthesis (mg CO2 dm-2 day-1) 60 40 20 Growing Season Growing Season Growing Season 0 Arizona Montana Oregon Growing Season Growing Season Growing Season

23. MODIS GPP at regional level Missoula

24. The Keeling Curve – CO2