Predicting climate change response

The whole-tree chambers will help assess climate change effects on eucalypts
The whole-tree chambers will help assess climate change effects on eucalypts.

A unique experiment which aims to predict how Australian eucalypt forests will respond to greenhouse-induced climate change within the next 100 years is taking shape on the western Sydney skyline.

Twelve six-metre high “whole tree chambers” have been erected on the University of Western Sydney’s Richmond campus as part of a research collaboration known as the Hawkesbury Forest Experiment.

NSW Department of Primary Industries (DPI) research scientist, Dr Craig Barton, says the aim is to predict how eucalypt forests growing in typical Australian conditions will react to rising carbon dioxide (CO2) levels in the atmosphere.

Each of the controlled atmosphere chambers will contain a spotted gum (Corymbia maculata) sapling, and is designed to expand to up to 10 metres tall as the trees grow over the next three years.

The atmosphere inside half of the chambers will be altered so that it contains 700 parts per million of  carbon dioxide - double that currently found in the earth’s atmosphere.

Because water, as well as CO2, is a key factor in a plant’s growth, half the trees will have high quantities of available water, while the other half will have limited access to water.

Dr Barton said that extra CO2 could cause a tree to grow more efficiently, with less water.

“However, wood production and stem growth could increase, possibly leading to a denser canopy.

“One impact of this could be to stop rainfall reaching the soil and other parts of the ecosystem.”

During the experiment scientists will monitor such factors as tree growth rates, carbon storage potential and water use.

Dr Barton said that “one of the potential effects of increased CO2 in the atmosphere is to reduce the amount of water lost by plants for the same amount of carbon fixed into sugars for plant growth and maintenance.

“Any increase in water use efficiency has potential implications for species distribution, water yields in catchments, forest growth and carbon sequestration.”

Dr Barton said the data collected will be used to test and develop models that emulate the impact of higher CO2 on whole forests.

The Hawkesbury Forest Experiment is a collaboration between the University of Western Sydney, University of New South Wales, University of Technology (Sydney), NSW DPI and the Swedish University of Agricultural Sciences.

The Australian Greenhouse Office is contributing $1.2 million to the project.