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With Western Australia a water limited environment, at least for much of every year, a better understanding of water balance and how plants affect it should improve land use productivity.

For his PhD project at The University of Western Australia (UWA), Craig Scanlan focused on how plants changed the way water stored and flowed in soils and assessed how this affected growth.

At the recent 2010 World Congress of Soil Science in Brisbane, Dr Scanlan was awarded the Australian Soil Science Society CG Stephens PhD Award in Soil Science, for the best PhD thesis in soil science granted by an Australian university in 2009.

His thesis, ‘Processes and effects of root-induced changes to soil hydraulic properties’, was described by the judges as “an innovative thesis that makes a significant contribution to the theoretical framework of soil science and which developed a new theory that can have a wider application in managing soil structure, effluent disposal, pasture and crop management and natural resource modelling.”

Its take-home message was that root-induced changes to soil hydraulic properties were dynamic and depended on the combination of soil texture, connectivity of root modified pores and the ratio of root radius to pore radius.

His PhD Supervisor at UWA, Professor Christoph Hinz, said that to assess how plant roots affected soils and water balance, Dr Scanlan devised a new quantitative model to account for the effects and estimate water balance and associated changes.

To develop the model, he completed detailed studies of soils and reviewed and synthesised data of plant root sizes and distribution.

Professor Hinz explained that when plants grew into soil with little biological activity, plant roots changed the structure and often the fabric of soils.

“This can then result in dramatic changes to the soil’s water holding capacity and its ability to transmit water,” he said.

WA environments, with highly weathered ancient soils that were often sodic and prone to hard setting and crust formation, were often very vulnerable to land degradation.

Professor Hinz regarded Dr Scanlan’s thesis as an important contribution to greater understanding and the predicting of major land use involving changes in vegetation.

“Significantly for WA, where resources and agriculture drive the economy, his  PhD has potentially significant ramifications for ecosystem restoration in mine-site rehabilitation, on-farm changes to cropping systems, or other environmental impacts involving changes to plant communities and plant types,” Professor Hinz said.

Led by Professor Hinz, a research group in the UWA School of Earth and Environment and the UWA Institute of Agriculture is improving understanding of the feedback processes between soil and vegetation and aiming to better predict hydrological processes at the landscape scale.

Dr Scanlan, who received a GRDC postgraduate scholarship to complete his PhD at UWA, works at Northam for the WA Department of Agriculture and Food, which also supported his UWA studies.

Media references

Authorised by ‘The UWA Institute of Agriculture’ and issued on its behalf by
Brendon Cant & Associates (+61) 8 9384 1122

Professor Christoph Hinz (+61) 8 6488 3466
Winthrop Professor Kadambot Siddique, Director, UWA Institute of Agriculture
(+61) 0411 155 396