Arid and semi-arid regions occupy 70% of the Australian land surface and climate driven changes to the functioning of these regions have huge impacts on the global carbon budget. During wet periods, vegetation expands and more CO2 is stored—creating a carbon sink—but during dry periods, plants dieback and regions switch to becoming carbon sources.
The implications of such pivots are astounding. For example, in 2011 la niña-driven higher than average rainfall in arid and semi-arid Australia significantly contributed to the southern hemisphere capturing more CO2 than it emitted and ‘the global carbon sink anomaly’ was coined.
The Mulga woodlands at TERN’s Alice Mulga SuperSite in the Northern Territory (image courtesy of Tonantzin Tarin)
Climate variability in central Australia is very large, ranging in rainfall from under 30 mm per year in the last couple years to over 950 mm per year in the mid-1970s. As IPCC projections for arid Australia indicate such extreme variation to continue, understanding these source to sink (and vice versa) tipping points, and being able to predict them, is of global importance.
To this end, a team of researchers from University of Technology Sydney has used long-term data collected at NCRIS-enabled TERN sites in two of arid and semi-arid Australia’s major biomes, Mulga woodlands and spinifex grasslands (Corymbia savanna). Research lead, Dr Tonantzin Tarin explains:
That means that over the seven-year period, the Mulga woodland was a carbon sink for five years and the spinifex grassland for just one year. Dr Tarin adds that there is also significant seasonal, inter-annual variability and that the tipping points are linked to different climatic drivers such as temperature, soil water content and solar radiation.
Over a seven-year period, the Mulga woodland was a carbon sink (positive Net Ecosystem Production (NEP) values) for five years and the spinifex grassland for just one year (graphic courtesy of Tonantzin Tarin)
The research relied heavily on data from TERN’s Alice Mulga SuperSite together with data from the nearby Ti Tree site which has TERN OzFlux and NCRIS-enabled Groundwater project infrastructure, says Dr Tarin’s fellow researcher, Dr James Cleverly.
Dr Tonantzin Tarin at TERN’s Alice Mulga SuperSite. Dr Tarin leads a team of researchers from University of Technology Sydney who have used TERN research infrastructure m data to better understand the climate and rainfall driven tipping points of two of arid Australia's most extensive ecosystem types (image courtesy of Tonantzin Tarin)
The data and knowledge generated by this research on current and future possible eco-physiological behaviours of 70% of Australia are essential in the development of climate change adaptation and mitigation programs, says Dr Tarin.
Flux monitoring equipment at TERN’s Alice Mulga SuperSite
Published in TERN newsletter December 2019