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. 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
- 3. Stomatal conductance response to elevated [CO 2 ] Medlyn et al unpublished
- 7. One year old
- 8. 1.5 years old - Extended to 9m tall
- 9. 2 years old – Harvested trees
- 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. 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. Whole canopy CO 2 flux per unit leaf area
- 13. Whole canopy H 2 O flux per unit leaf area
- 14. VPD in chambers April 08 – March 09
- 17. Leaf level ITE Data from D.Ellsworth
- 20. Assimilation
- 21. Transpiration
- 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
Hinweis der Redaktion
- Figure 1: A preliminary meta-analysis of the response of stomatal conductance to elevated [CO2] comparing responses among functional groups. A response of 1 indicates no change. Stomata of eucalypts appear to be more sensitive to high [CO2] than conifers or broadleaf deciduous species, indicating potentially larger water savings at high [CO2].
- The whole tree chambers serve two purposes. They allow us to grow relatively large trees in a controlled environment where we can regulate the temperature, humidly, water availability and CO2 concentration. They allow us to monitor whole tree CO2 and water fluxes as the trees grow. In this respect they are unique and are providing valuable information at a spatial scale that would otherwise be unobtainable.
- Not widely used in forestry due to its susceptibility to pests. However its wide natural distribution and rapid growth make it suitable as a research tool.
- The upper part of the chamber is sealed from the soil and roots so we can measure canopy and root/soil fluxes independently. Air is circulated through a large heat exchanger which serves two purposes it cools the air but also condenses out excess moisture resulting from tree transpiration. A small amount of fresh air is constantly added to the chamber into which pure CO2 is metered. The system acts as a null balance and co2 is added to compensate for photosynthesis by the tree. A root barrier to depth of 1m prevents lateral movement of shallow roots ensuring that soil properties are influenced by the target tree and not neighbours. Soil moisture is monitored with various instruments to a depth of 4 m.
- Similar sized trees at time of measurement (about 15 m2 leaf area).
- Daytime CO2 flux (PAR>100umol m-2 s-1) averaged over two week bins then averaged by treatment (n=6 then 3) to give the SEM (error bars)
- Due to the way that humidity was regulated by using a cold trap held at just below target chamber dew point to both remove excess heat and excess water from the air the actual equilibrium humidity in a chamber is dependant to some extent on the way the tree/chamber partitions incoming radiation load between latent and sensible heat. Large trees with high transpiration rates tend to self cool to some extent and so there is less demand for active cooling and the absolute humidity in the chamber is slightly higher. Elevated chambers had a VPD about 15% lower than ambient chambers the difference developed as the trees became large.
- Leaf level measurements made periodically throughout the experiment showed a ratio of ITE that matched expectations from the Ball–Berry model.
- PAR >300 umol m-2 s-1 with data in 2hr bins from sunrise. Each point is the mean of 3 chambers during that 2hr bin. Data cover the period