Greenhouse gas emissions from sub-tropical terrestrial systems

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The aim of this project is to

• Improve the knowledge base of soil-based greenhouse gas (GHG) emissions from Australia’s sub-tropical and tropical land management systems, and;



• Develop sustainable land use and adaptation strategies at a scale which will ultimately have a positive impact on productivity and the country’s GHG account.

Three greenhouse gases are intimately associated with terrestrial ecosystems – carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄). Although CH₄ and N₂O are at far lower atmospheric concentrations than CO₂, their respective Global Warming Potential (GWP) are sufficiently high that small changes have a disproportionate effect on radiative forcing and ultimately climate change.

The GWP of CH₄ is 23 and N₂O is 296, meaning that a molecule of contemporary N₂O released to the atmosphere will have 296 times the radiative impact of a molecule of CO₂ released at the same time. Thus, an activity that reduces N₂O emissions by 1 kg ha^-1 is equivalent to an activity that sequesters 296 kg CO₂ ha^-1 as soil carbon.

There has been no comprehensive greenhouse gas data collected over multiple years in the sub-tropics which incorporate the impacts of management and climate variability on soil-based emissions.

Reliable predictive modelling of the impacts of adaptation and mitigation strategies across regions on emissions is therefore only possible with local data stores which incorporate climate variability in both time and space.

The identification of synergistic adaptation and mitigation strategies for carbon sequestration in soils and biomass and GHG reductions will provide substantial economic and environmental benefit.

The notion of full greenhouse accounting to comprehensively assess the impact of land management strategies to offset climate change has continued to gain momentum in recent years (Grace et al., 2003).

The project has both an extensive (transect based) methodology using simple sampling chambers and an intensive sampling method using an automated system. Emissions of CO₂, CH₄ and N₂O are automatically collected and analysed in real-time using an SRI gas chromatograph and infra-red gas analyzer and sampling system housed in a portable trailer and attached to automated sampling chambers. The main sampling site has rainforest, pasture and tree crops and is situated in the Mooloolah Valley, approximately 100 kms north of Brisbane and 20 kms inland from Caloundra.

Collaborators include Drs Klaus Butterbach-Bahl and Ralf Kiese from the Institute for Meteorology and Climate Research, Forschungszentrum Karlsruhe (IMK-IFU), Garmisch-Partenkirchen.

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Mooloolah, Qld

Automated chambers

Trailer based
system

Sampling system

Gas chromatograph

Simple sampling chambers

Analysed in
real-time

Rainforest

Tree crop

Pasture

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