Australia's low rainfall areas could support a viable timber industry, according to researchers.

Four dry zone eucalypt species have been tested for their potential to produce high value solid-timber products, and there is cautious optimism about the results.

The two-year CSIRO low rainfall study is a joint investment with the Natural Heritage Trust managed by the Forest and Wood Products Research and Development Corporation (FWPRDC) through the Joint Venture Agroforestry Program (JVAP).

"We tested swamp yate, sugar gum, brown mallet and yellow gum," CSIRO's Philip Blakemore says. "They were harvested from existing dry area plantations, where they had grown large enough to evaluate - that is, with a diameter of more than thirty centimetres."

Mr Blakemore says that farmers in the low rainfall (less than 400-600mm/yr) regions of southern Australia will need to plant trees from improved genetic stock, and manage their plantations to produce higher value logs.

"Given the slow growth rates of these low rainfall species, the economics of plantations are still likely to be marginal," says Mr Blakemore. "But trees in the landscape can add value to the environment by combating dryland salinity, enhancing local biodiversity, and even improving the appearance of farms."

Mr Blakemore says that there is a marked difference in timber from trees harvested in only slightly wetter areas.

"We evaluated the wood products after sawing and drying the timber from the logs," he says.

"The amount of high-quality products recovered from logs was low compared to that recovered from trees in the 600-750mm/yr rainfall zone. Knots and decay in particular are significant problems in the drier areas.

"This is mostly related to the poor form and branching characteristics of the sample trees. Most of the trees had grown in unmanaged plantations on low productivity sites resulting in low and heavily branched crowns," he says.

According to Mr Blakemore if sawlogs with diameters over 40 cm could be produced in less than 40 years and significant improvements made in the volume of knot-free timber grown, then it is feasible that a viable solid wood industry could be established in the lower rainfall region.

Of the four species evaluated - swamp yate (Eucalyptus occidentalis), sugar gum (E. cladocalyx), brown mallet (E. astringens) and yellow gum (E. leucoxylon) - sugar gum showed the best potential for the drier regions followed closely by swamp yate and brown mallet. Despite having the least drying problems, yellow gum has little potential unless problems with extremely poor form can be overcome.

Work on genetically improving planting stock is currently focused through the Australian Low Rainfall Tree Improvement Group (ALRTIG). This group has identified additional species such as red gum (E. camaldulensis), spotted gum (Corymbia maculata) and red ironbark (E. sideroxylon) as being suitable for dry zone plantations.

A similar study done by CSIRO researchers in the 600-750 mm/yr rainfall showed promising amounts of 'appearance grade' products from spotted gum and red ironbark.

FWPRDC Executive Director, Dr Kwame Asumadu, applauded the results.

"This work will greatly assist growers and the forest products industry to identify which species have the greatest potential for the production of high-value wood products in low rainfall areas," he says.

"This research meets the NHT objective of using vegetation to repair degraded landscapes while generating commercial benefits.

"The wider environmental benefits provide added incentives for the establishment of agroforestry programs in low rainfall areas which provide an additional resource for Australia's forest and wood products industry," Dr Asumadu says.

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