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A new invention that tells European farmers when their olive groves and wheat crops need water is being used for the first time to find out how Australian trees cope with drought and climate change.

Water is the ‘blue gold' of the future and likely to become an increasingly limiting resource, said Dr Martin Bader of The University of Western Australia's School of Plant Biology.  Trees are an excellent indicator of climate change.

The invention - the Zim probe - could revolutionise botanists' knowledge of water use and drought stress on native trees by sending continuous data from their leaves to researchers.

Each probe consists of two round magnets smaller than a five-cent piece.  Scientists used a cherry picker to attach about 90 clamps to leaves from jarrah, tuart and banksia trees in Kings Park.

The bottom magnet holds a sensor that records clamp pressure and sends data to the internet.  The magnetic force is weakened when the leaf holds a lot of water.  ‘It's similar to measuring blood pressure in humans," Dr Bader said.

"Plants feel subtle changes in humidity, light, wind and water availability.  This is the first big ecological project using the probe to enable us to record the effects of climate change."

Dr Bader said 2010 was the driest year on record in southwest WA, followed by one of the state's hottest summers.

"These extreme events have caused severe crown decline in jarrah and other important woody species of the jarrah forest," Dr Bader said.

"Until Professor Ulrich Zimmermann in Germany invented the probe, the only way we could measure leaf water in relation to the environment was destructive.  We had to pick leaves and put them in a pressurised vessel to measure plant moisture stress.  It was very time-consuming and gave us information only for one particular point in time," he said.

"Transpiration measurements using a different device revealed that on a 40-degree day, jarrah mostly closes its leaf pores (stomata) during the late morning to save water.  This is bad for photosynthesis, which uses the sun's energy to convert carbon dioxide into compounds including sugars.

"From about 10.30am, the leaves closed their pores to save water but it meant the tree did not get the benefits of photosynthesis.  Jarrah trees can send their roots down 60 metres to get water but depletion of Perth's groundwater means there is often no longer any water there or roots can't keep pace with the drawdown."

Professor Zimmermann is one of Dr Bader's collaborators, and Dr Bader's UWA supervisor is Professor Erik Veneklaas, of the Centre of Excellence for Climate Change, Woodland and Forest Health.  The project is a collaboration with Kings Park and Botanic Gardens, which also co-finance it.

The research will help the management of young trees on mine rehabilitation sites and allow predictions of tree responses to climate change.

Dr Bader's project was featured on the ABC Science Show , Catalyst, last night.

Media references

Dr Martin Bader (UWA School of Plant Biology)  (+61 8)  6488 3700
Michael Sinclair-Jones (UWA Public Affairs)  (+61 8)  6488 3229  /  (+61 4) 00 700 783