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Effects of rising CO2 concentration on water use efficiency of Eucalyptus saligna - Craig Barton


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Effects of rising CO2 concentration on water use efficiency of Eucalyptus saligna - Craig Barton

  1. 1. Effects of rising CO 2 concentration on water use efficiency of Eucalyptus saligna Craig Barton M. Adams , J. Conroy, R. Duursma, D. Eamus, D. Ellsworth, S. Linder, B. Medlyn, D. Tissue, R. McMurtrie CCRSPI Conference 2011, Melbourne
  2. 2. Hawkesbury Forest Experiment <ul><li>Established to investigate the impacts of climate change on Australian trees . </li></ul><ul><li>Integrated program of experimental research and modelling. </li></ul><ul><li>Little known about the response of Eucalypts to elevated CO 2 . </li></ul><ul><li>Many Australian forest and woodland systems characterised by poor soils and frequent droughts. </li></ul>
  3. 3. Stomatal conductance response to elevated [CO 2 ] Medlyn et al unpublished
  4. 4. Whole Tree Chambers <ul><li>Designed and first used in Northern Sweden. </li></ul><ul><li>They isolate trees in a controlled environment for CO 2 exposure and whole-tree measurements. </li></ul><ul><li>Chambers track outdoor conditions. </li></ul><ul><li>Allows us look at interactive effects of elevated CO 2 and drought. </li></ul><ul><li>Growing under local climate. </li></ul>
  5. 5. Eucalyptus saligna <ul><li>Sydney Blue Gum </li></ul><ul><li>Fast growing mainly coastal tree that has commercial plantation use. </li></ul><ul><li>Prefers warm humid climatic conditions </li></ul><ul><li>Mean precip 900-1800mm p.a. </li></ul><ul><li>Planted April 2007. </li></ul>
  6. 6. Experimental design <ul><li>12 whole tree chambers </li></ul><ul><li>6 run at ambient [CO 2 ] A (390 ppm) </li></ul><ul><li>6 run at elevated [CO 2 ] E (630 ppm) </li></ul><ul><li>Half of each set subjected to periodic drought. </li></ul>
  7. 7. One year old
  8. 8. 1.5 years old - Extended to 9m tall
  9. 9. 2 years old – Harvested trees
  10. 10. Whole tree chambers Described in Medhurst et al 2006 PC&E and Barton et al 2010 Ag.For. Met Fresh air inlet 1 air change per hour Root barrier Heat exchanger floor 6 m condensate CO 2 addition
  11. 11. Whole-tree fluxes The system can resolve responses to short term fluctuations in light. Afternoon depression of carbon uptake present. CO 2 fluxes are very similar Water loss is much lower in the elevated CO 2 tree. Barton et al 2010 Agricultural and Forest Meteorology 150 :941-951
  12. 12. Whole canopy CO 2 flux per unit leaf area
  13. 13. Whole canopy H 2 O flux per unit leaf area
  14. 14. VPD in chambers April 08 – March 09
  15. 15. Effect of CO 2 on Instantaneous Transpiration Efficiency <ul><li>ITE = instantaneous transpiration efficiency </li></ul><ul><li>= A / E (mmol CO 2 mol -1 H 2 O) </li></ul><ul><li>Carbon Assimilation / Water used </li></ul><ul><li>According to Ball-Berry model, A and E are related: </li></ul>
  16. 16. Implications <ul><li>If we assume that stomatal conductance does not acclimate to [CO 2 ] then the ratio of ITEelev / ITEamb will equal Ca-elev / Ca-amb </li></ul><ul><li>In our case 630/390 = 1.6 </li></ul><ul><li>ITE should increase by 60% </li></ul>
  17. 17. Leaf level ITE Data from D.Ellsworth
  18. 18. Transpiration Efficiency
  19. 19. Transpiration Efficiency
  20. 20. Assimilation
  21. 21. Transpiration
  22. 22. Conclusions <ul><li>Strong down-regulation of photosynthesis resulting in little if any “ fertilisation effect” of elevated CO 2 </li></ul><ul><li>Data supports Ball-Berry model at leaf and canopy scale. </li></ul><ul><li>No acclimation of stomatal response to CO 2 </li></ul><ul><li>Implications for models used to predict forest growth (3PG, GDAY, Cabala) </li></ul><ul><li>VPD is important to results. </li></ul>
  23. 23. Investigating the Impacts of Climate Change on Australia’s Forests Craig Barton The Hawkesbury Forest Experiment M.Adams, B. Amiji, J. Conroy, R. Duursma, D.Eamus, D. Ellsworth, S. Linder, M. Löw, B. Medlyn, J. Parsby, D. Tissue, R. McMurtrie, et al Thank You