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An 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.

Dr Martin Bader from the School of Plant Biology said water was the ‘blue gold' of the future and likely to become an increasingly limited resource, and the instrument, the Zim probe, could revolutionise botanists' knowledge of water use and drought stress on native trees.

Trees are an excellent indicator of climate change, and the probe sends continuous data from their leaves to researchers.

Each probe has two round magnets smaller than a five-cent piece. Scientists recently 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.

The Zim probe was released a little over a year ago by Zim Plant Technology in Germany and is already used across Europe on crops such as olives, wheat and wine grapes.

"It is also used in Australia mainly on wheat and other grains," Dr Bader said. "However, the use on eucalypts in our research project is its first major application in the field of plant ecology, which is a pioneering role for Australia.

"We are also testing a prototype Zim probe for needle-like leaves on Allocasuarina which seems to work extremely well so far.

"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, from 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-finances it.

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

Published in UWA News , 14 May 2012