A researcher at The University of Western Australia aims to understand the structure and function of the deep roots of WA's karri and tuart trees by monitoring their roots from caves.
Dr Tim Bleby of the School of Plant Biology, the son of a forester who grew up on a South Australian pine plantation, said the aim of his work was to learn more about the role of tall, deep-rooted trees in the water cycle of South-West WA, and to understand how these tall trees might react to water shortages brought about by climate change.
Dr Bleby said a 20m-tall tree would have a 20m-deep root system and that a good way to understand the roots was to monitor them in action, using ready-made underground access points - caves - to do so.
He plans to visit a series of caves of the Gnangara Mound near Yanchep and in the Leeuwin-Naturaliste Ridge near Margaret River. In some of these caves, it is possible to reach live tree roots at 20m depth that can be as thick as the handle of a cricket bat.
The work is not new to Dr Bleby, who studied the roots of evergreen oak trees on a cattle ranch near Austin, Texas, using a cave system where he had to contend with Mexican free-tail bats, toxic fungus from their droppings, cold underground streams, ticks, spiders and rattlesnakes. Dr Bleby majored in Botany at the University of Adelaide before undertaking a PhD at UWA, studying the water use of young jarrah trees in mine-site rehabilitation.
Part of his research into root-systems involves placing heat sensors on the roots to measure the sap flow and the amount of underground water taken up by the trees.
"When it comes to growing roots, trees are expert engineers," Dr Bleby said. "They appear to adjust their root anatomy depending on depth, which permits them to transport water over long distances and against gravity with remarkable efficiency. Deep roots are poorly understood and notoriously difficult to work with, but I hope to show that they are just as important as aboveground stems and leaves for regulating how much water tall trees such as karri and tuart are able to use.
"In the bigger picture, understanding the role of deep-rooted trees in the water cycle is critically important for managing the amount and quality of water that reaches our catchments, rivers and groundwater reservoirs," Dr Bleby said. "Catchments in turn supply freshwater for cities, towns, industries, agriculture and forestry. Our ability to predict the role of vegetation in water and carbon cycling is directly linked to how well we understand the physiological and ecological controls on plant water-use. In WA, we have ecologically important and globally significant tall forest and woodland species facing threats from groundwater loss, changes to fire regimes and declining winter rainfall."