Gum trees, encased in their special atmosphere-controlled chambers filled with higher concentrations of carbon-dioxide than the outside air.
Credit: Sally Tsoutas
SYDNEY, 23 August 2006: Looking like alien trees, garbed in plastic bubble-boy spacesuits, a new research project hopes to discover how trees will grow 100 years in the future, when scientists expect atmospheric concentrations of carbon-dioxide (CO2) to be significantly greater than they are today.
Increasing levels of CO2 in the atmosphere are changing the world's climate and fuelling global warming. The resulting rise in worldwide temperatures is predicted by scientists to have potentially devastating effects on the global ecosystem.
However, an increase in atmospheric CO2 could actually be a boon to plants, increasing vegetative growth in many areas around the world, including Australia.
"It is the first field-based carbon-dioxide enrichment study with trees in the Southern Hemisphere," said Jann Conroy researcher at the Hawkesbury Campus at the University of Western Sydney.
Although the researchers are mimicking the increasing carbon dioxide levels, they are unsure of how the trees will grow. Whether or not the water intake of the trees will increase in the accelerated climate change conditions are questionable.
"Theoretically, trees will grow bigger as the carbon dioxide rises because, unlike animals, plants get all of their carbon for growth from the atmosphere. The theory has been proven for crop plants, grasses and small trees growing in glasshouses and for forests, on fertile sites, in the Northern Hemisphere," she said.
Researchers predict the heightened carbon dioxide levels may reduce the amount of water need for trees to grow.
"Water and carbon dioxide are key factors in any plant's growth. The extra carbon dioxide could make the tree grow more efficiently - boosting fresh productivity with increased stem growth and more rapid production of wood, despite possibly less rain," said Conroy.
But none of the research on the increasing carbon dioxide's effect on plant growth has been done in Australia's trademark arid conditions.
"The evolution of Australian trees under conditions of poor soil fertility combined with frequent droughts makes extrapolation of results from Northern hemisphere species difficult," she said.
The researchers chose spotted gum (Corymbia maculata) to "predict the likely response of Australian forests and woodlands to future climatic conditions," she said.
The twelve chambers used in the current experiment were already used in similar experiments conducted by the Swedish University of Agricultural Sciences. The experiments used 40-year-old Norway spruce trees in Northern Sweden. And the results proved the trees growth depended on nutrient availability, regardless of carbon dioxide levels.
"Our continent is one of the driest on earth," she added. "And consequently Australia's soils - unlike those of the Northern Hemisphere - are nutrient-impoverished."
The atmosphere-controlled chambers will grow with the gum trees up to ten metres tall. Each tree is "covered with tough clear plastic sheeting that seals below ground level to create a mini ecosystem," she said.
Half of the chambers will be kept at a concentration of carbon dioxide currently in our air, but the other six will house 700 parts per million of carbon dioxide, which is twice the level of carbon dioxide today.
Each chamber is equipped with a large heat exchanger and irrigation system to ensure the temperatures and humidity to match outside conditions. But the carbon dioxide concentration and water availability will be tweaked to follow global climate change trends.
By 2100, Australia will hit a double whammy: carbon dioxide levels will increase and rainfall will decrease.
These climatic time machines, part of a multi million dollar experiment, might answer the uncertainty of "consequences of more carbon dioxide available to our bush ecosystems," she added.
