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Die-back of the Amazon in DGVMs: climate drivers and mechanisms

Die-back of the Amazon in DGVMs: climate drivers and mechanisms. David Galbraith, Patrick Meir, Peter Levy, Daniel Metcalfe. What is the best use of Biosphere 2? March 06, 2009. Amazon Die-back Predictions: A Brief History. White and Friend (1999). Cox et al. (2000). Sitch et al. (2008).

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Die-back of the Amazon in DGVMs: climate drivers and mechanisms

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  1. Die-back of the Amazon in DGVMs: climate drivers and mechanisms David Galbraith, Patrick Meir, Peter Levy, Daniel Metcalfe What is the best use of Biosphere 2? March 06, 2009

  2. Amazon Die-back Predictions: A Brief History White and Friend (1999) Cox et al. (2000) Sitch et al. (2008)

  3. Uncertainty in Modelled Die-back EMISSIONS Carbon Cycle Feedbacks PARAMETERS CLIMATE RESPONSE ECOSYSTEM RESPONSE PROCESSES

  4. Aims 1) Separate the contributions of four environmental variables to Amazon dieback in 3 DGVMs: • precipitation • relative humidity • temperature • carbon dioxide 2) Identify which carbon cycle process responses most affect the simulated loss of Amazon vegetation carbon in different models? • Direct effect on Plant respiration • Direct effect on GPP • Indirect effect on GPP

  5. Modelling Protocol 3 DGVMS (HYLAND, LPJ, TRIFFID) IMOGEN GCM ANALOGUE + 4 IPCC SCENARIOS 16 Factorial Simulations per model/scenario combination

  6. HYLAND LPJ TRIFFID Predicted Change in Vegetation C in 2100 HYLAND LPJ TRIFFID A1FI Precipitation Only Simulations with CO2 held constant A1FI Temperature Only A1F1 except CO2

  7. HYLAND LPJ TRIFFID Predicted Change in Vegetation C to 2100 A1F1Precipitation + CO2 Simulations with varying CO2 A1F1 Temperature + CO2 A1F1 Scenario

  8. Contributions of Environmental Drivers to Dieback Contribution of environmental drivers to Amazon VegC loss in 4 IPCC scenarios

  9. Response Curves of Amazonian Veg C to Precipitation

  10. Temperature Mechanisms Lloyd and Farquhar 2008

  11. Temperature Mechanisms: Results Similar outcome, yet very different mechanisms

  12. Temperature Mechanisms: Results (2)

  13. How reliable are current DGVM processes? • Which photosynthesis temperature dependency is correct? • How plastic are temperature response curves to photosynthesis? • How important are direct vs. indirect effects of temperature on photosynthesis? • How should we represent plant respiration under changing climate? Metcalfe, Meir et al.

  14. Functional Diversity in Climate Change Responses in DGVMs - How much variability is there in rainforest species sensitivity to drought/temperature? - Which mechanisms dictate the outcome of plant competition under drought and increasing temperatures? • Below-ground adaptation strategies – which processes are the most important?

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