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Mila Bristow_What is the impact of land use change on greenhouse gas exchange in tropical savannas?
The document discusses using flux towers to measure greenhouse gas exchange from land use changes in northern Australia. It summarizes the findings from a flux tower study of a savanna clearing site. The clearing caused the site to switch from a carbon sink to a carbon source. Peak emissions occurred during the dry season and after a post-clearing fire. Overall, clearing resulted in emissions equivalent to 31.4 tons of carbon per hectare.
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Mila Bristow_What is the impact of land use change on greenhouse gas exchange in tropical savannas?
- 1. Using TERN infrastructure to answer land management ques8ons capturing near real 8me GHG exchange using flux towers Mila Bristow (CDU), Lindsay Hutley (CDU), Jason Beringer (Monash), Stephen Livesley (U Melb), Stefan Arndt (U Melb), MaMhew Northwood (CDU)
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- 4. Background February 14, 2013 12:26PM
- 5. North Australian water resources
- 6. Land use in Australia today
- 7. Landscapes of north Australia Tropical savanna woodland and open-‐forests dominate the north
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- 9. Landscapes of north Australia climate
- 10. North Australian landscapes Savanna burning – 2011 fire scars
- 11. North Australian Flux Network TERN OzFlux Facility Fogg Dam Howard Springs Adelaide River Daly River: Uncleared Rainfall gradient Dry River Sturt Plains SpaFal paGerns of mass and UTS managed arid energy exchange zone tower
- 12. North Australian Flux Network TERN OzFlux Facility Red Dirt Melons Flux Tower ARC-‐Linkage project Daly River: Uncleared Rainfall gradient Red Dirt Melons Farm
- 13. What is the impact of LUC on ecosystem GHG exchange?
- 14. Tools used: Eddy covariance (flux tower) system • Measures: • energy • ET • CO2 fluxes • calculate NEE • scale up to annual sink/source
- 15. Tools used: standing biomass • Need to know stocks as well as fluxes • How much biomass in the savanna?
- 16. Also non-‐CO2 fluxes, soil C & N stocks and process? • Temporal and spa8al sampling of fluxes CO2 and non-‐CO2 and drivers • Replicated cleared and uncleared plots • NO3, NH4 pool size and net nitrifica8on • Soil physico-‐chemical characteris8cs
- 17. How is forest converted to farm land?
- 19. Before ANer Source NEE Sink Day of year
- 20. Clearing site – flux data 60 50 40 NEE (gCO2 m-‐2 d-‐1) 30 20 10 Source 0 -‐10 Sink -‐20 Aug 11 Dec 11 Mar 12 Jun 12 Sep 12
- 21. Clearing site: source/sink dynamics 60 25 50 Wet season 20 40 NEE (gCO2 m-‐2 d-‐1) Rainfall (mm) 30 15 20 10 10 Source 0 5 -‐10 Sink -‐20 0 Aug 11 Dec 11 Mar 12 Jun 12 Sep 12
- 22. Clearing site: source/sink dynamics 60 25 Savanna clearing 50 20 40 NEE (gCO2 m-‐2 d-‐1) Rainfall (mm) 30 15 20 10 10 Source 0 5 -‐10 Sink -‐20 0 Aug 11 Dec 11 Mar 12 Jun 12 Sep 12
- 23. Clearing site: source/sink dynamics 60 25 Dry season 50 20 40 NEE (gCO2 m-‐2 d-‐1) Rainfall (mm) 30 15 20 10 10 Source 0 5 -‐10 Sink -‐20 0 Aug 11 Dec 11 Mar 12 Jun 12 Sep 12
- 24. Clearing site: source/sink dynamics 60 25 Fire 50 20 40 NEE (gCO2 m-‐2 d-‐1) Rainfall (mm) 30 15 20 10 10 Source 0 5 -‐10 Sink -‐20 0 Aug 11 Dec 11 Mar 12 Jun 12 Sep 12
- 25. Clearing site: source/sink dynamics 60 25 50 20 40 NEE (gCO2 m-‐2 d-‐1) Rainfall (mm) 30 15 20 10 10 Source 0 5 -‐10 Sink -‐20 0 Aug 11 Dec 11 Mar 12 Jun 12 Sep 12
- 26. Uncleared + Clearing site savanna clearing >4 tC ha-‐1 NEE (mg CO2 m-‐2 s-‐1) Cleared site Source Sink Uncleared site Fire Week of the year
- 27. GHG emissions from burning debris • Fuel curing over dry • Assump8ons season 2012 • all AGB consumed • Burning late dry season • 90% of BGB consumed to maximise • Fine roots ignored, no consump8on for site soil C loss, no CWD prepara8on to melons included, no decay of coarse roots • Emissions es8mated for fire event using NCAS default emissions factors
- 28. Post-‐clearing fire GHG emissions t CO2-‐e 92.3 3.8 1.2 Post clearing debris CO2 CH4 N2O
- 29. The site today Final stage: agricultural land
- 30. CO2 from clearing: comparing cleared and uncleared tower sites • Equivalent to 31.4 t C ha-‐1 (or 115.4 t CO2-‐e ha-‐1) • equivalent to 12 years of carbon sequestra8on
- 31. Soil CH4 and N2O fluxes Methane Flux 14 Cleared savanna 12 Savanna woodland 10 ug CH4-‐C m-‐2 h-‐1 8 6 4 2 0 -‐2 -‐4 -‐6 Oct 11 Dec 11 Feb 12 Mar 12 May 12 Jul 12
- 32. Soil CH4 and N2O fluxes Methane Flux + rainfall 14 Cleared savanna 25 12 Savanna woodland 10 rainfall 20 ug CH4-‐C m-‐2 h-‐1 8 6 15 4 2 10 0 -‐2 5 -‐4 -‐6 0 Oct 11 Dec 11 Feb 12 Mar 12 May 12 Jul 12
- 33. Soil CH4 and N2O fluxes Nitrous Oxide Flux 25 Cleared savanna N2O flux (ug N2O-‐N m-‐2 h-‐1) 20 Savanna woodland 15 10 5 0 -‐5 Oct 11 Dec 11 Feb 12 Mar 12 May 12 Jul 12
- 34. Soil CH4 and N2O fluxes Nitrous Oxide Flux + rainfall Cleared savanna 25 25 N2O flux (ug N2O-‐N m-‐2 h-‐1) Savanna woodland rainfall 20 20 15 15 10 10 5 0 5 -‐5 0 Oct 11 Dec 11 Feb 12 Mar 12 May 12 Jul 12
- 35. Savanna ecosystems are a major exchange of global GHG Flux towers cri8cal tool to understand ecosystem change....
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- 38. Thanks… ques8ons??? We would like to thank our research partners Red Dirt Melon Farm, this is an ARC-‐Linkage funded project Mila Bristow (CDU), Lindsay Hutley (CDU), Jason Beringer (Monash), Stephen Livesley (U Melb), Stefan Arndt (U Melb), MaMhew Northwood (CDU)