Bulletin

Issue: August 2004

Research in Action

What causes High Country change?

The old-time cattlemen told stories of horses sinking to their bellies in the deep wet peat bogs that dotted the high plains of the Australian Alps. Today on the site of many of these peat bogs there is barely 20 cm of dry peat soil - and no sign of any wetland vegetation.

What caused the change and exactly when did it happen? And how significant to the welfare of the alpine ecosystem are peat bogs?

La Trobe University soil scientist, Ms Samantha Grover, is contributing to the debate with research for her PhD thesis on the hydrology and characteristics of peat soils in the Australian Alps.

While there is anecdotal evidence that the bogs have become smaller and drier and that stock grazing has caused or contributed to this degradation, Ms Grover is confident that by early 2005, she will have amassed sufficient data to be able to determine when the onset of the degradation began and its causes.

Ms Grover has recently been awarded a Postgraduate Research Award from the Australian Institute of Nuclear Science and Engineering to use carbon dating, and lead dating techniques for more recent times, to determine whether the onset of damage began before or after the introduction of summer stock grazing in the high country in the 19th century.

She explains that peat bogs in the Australian Alps comprise a layer of live growing moss on the surface of the bog, on top of successive layers of dead and decomposing plant material. The cold and wet conditions in the Alps inhibit the decomposition of the dead plant material, which builds up to form peat soils typically one to two metres deep.

'Because the Sphagnum moss grows vertically, the decaying plant material in a peat bog provides a vertical time sequence and we can date each layer using the isotopic composition of various elements that each layer contains,' Ms Grover said. Peat from the base of the bogs has been dated at almost 9,000 years old, in initial studies completed by Ms Grover at the Australian Nuclear Science and Technology Organisation in Lucas Heights, Sydney earlier this year.

Supervised by La Trobe lecturer in Viticultural Sciences, Dr Judy Tisdall, and researchers from the La Trobe Research Centre for Applied Alpine Ecology, Dr Ken Rowe and Mr Warwick Papst, Ms Grover's work is also characterising the present hydrology of peat bogs and the adjacent dried peat soils.

The Alps are an important water catchment, providing up to eighty per cent of stream flow in the Murray-Murrumbidgee catchment in drought years, and all of this water passes through bogs. While bogs have long been considered important in catchment hydrology, the mechanisms of this valuable ecosystem service have been subject to much hypothesis but little scientific investigation.

Detailed field and laboratory measure-ments of environmental properties, water movement and water holding capacity of bogs and dried peats are revealing how these wetlands affect catchment hydrology.

'The central factor affecting peat hydrology is how decomposed the plant material is,' Ms Grover said. 'This has led to a valuable link between La Trobe University and the Cooperative Research Centre for Greenhouse Accounting, which is interested in the carbon chemistry and carbon dioxide emissions of peat.' Ms Grover's work regularly takes her to bogs on the Wellington Plains, in the Victorian Alpine National Park, to take samples and measurements and to monitor equipment, and occasionally to CSIRO Land and Water, Adelaide, to work with Dr Jeffery Baldock, who supervises the carbon aspect of the research.

'Ultimately, I am confident that this collaborative project will provide data which will enable us to manage the alpine ecosystems in a more sustainable way,' Ms Grover said.

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