Explaining the history of Australia's vegetation

May 17, 2018 by Robyn Mills, University of Adelaide
C4 dominated Australian landscape: Triodia pungens dominated hummock grassland with scattered Acacia and Eucalyptus, on Mittebah Station in the Northern Territory. Credit: Terrestrial Ecosystem Research Network (TERN)

University of Adelaide-led research has uncovered the history of when and why the native vegetation that today dominates much of Australia first expanded across the continent.

The new understanding will help researchers better predict the likely impact of climate change and rising CO2 levels on these critically important . Called 'C4 plants' after their alternative photosynthetic pathway, these plants include a wide variety of native tropical, subtropical and arid grasses as well as saltbushes. C4 crops include sugarcane and corn.

"C4 plants evolved to be able to photosynthesise under warm, dry, and low CO2 conditions, with a special ability to take advantage of summer rainfall," says lead author Jake Andrae, Ph.D. candidate in the University's School of Physical Sciences and Sprigg Geobiology Centre. "As a result, they dominate the vegetation of Australian tropical, subtropical, and arid regions today.

"But despite being the most C4 dominated continent today, little is known about the initial C4 expansion in Australia."

The researchers analysed fossilised leaf waxes and pollen preserved in marine sediments. They measured the chemical signatures from these remnants, to reconstruct how and when C4-dominated ecosystems first rose to prominence in Australia.

"In many regions around the globe, C4 plants became prevalent between six and eight million years ago, which is thought by some to be the result of falling global atmospheric CO2 concentrations during this time," says project leader Dr. Francesca McInerney, Australian Research Council Future Fellow at the University of Adelaide.

"Surprisingly, in north-west Australia C4 plants did not expand at this time in spite of regionally arid conditions and falling atmospheric CO2, both of which should have promoted C4 vegetation. Instead, C4 vegetation expanded across the landscape only 3.5 million years ago, several million years later."

The authors say that the rise of C4 plants in Australia was likely the result of a strong summer monsoon that developed around that time.

"The difference in the timing of the expansion of C4 plants in Australia from other parts of the globe demonstrates that regional climate changes are important in driving vegetation change," Dr. McInerney says.

"In the future, the interaction between global atmospheric CO2 and regional changes in seasonality of rainfall is likely to play an important role in the distribution of C4-dominated ecosystems. Rising CO2 will place C4 plants at a disadvantage, while rising temperatures, and changes in the season and amount of rainfall, could favour them.

"In Australia, C4 plants are critical to grazing, soil carbon storage and biodiversity. We need to understand the factors that are likely to influence their survival in the future, to provide a basis for future conservation of these important plants."

The research, in collaboration with Columbia University and University of Melbourne, has been published online in Geophysical Research Letters.

Explore further: Proposed benefits of rising carbon dioxide are more likely driven by water

More information: J. W. Andrae et al. Initial Expansion of C4 Vegetation in Australia During the Late Pliocene, Geophysical Research Letters (2018). DOI: 10.1029/2018GL077833

Related Stories

Recommended for you

Physicists discover new class of pentaquarks

March 26, 2019

Tomasz Skwarnicki, professor of physics in the College of Arts and Sciences at Syracuse University, has uncovered new information about a class of particles called pentaquarks. His findings could lead to a new understanding ...

Study finds people who feed birds impact conservation

March 26, 2019

People in many parts of the world feed birds in their backyards, often due to a desire to help wildlife or to connect with nature. In the United States alone, over 57 million households in the feed backyard birds, spending ...

Matter waves and quantum splinters

March 25, 2019

Physicists in the United States, Austria and Brazil have shown that shaking ultracold Bose-Einstein condensates (BECs) can cause them to either divide into uniform segments or shatter into unpredictable splinters, depending ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.