Top:E. dunnii seed capsules are collected to assist in the research. Above: A 34 year old E. dunnii is marked as a ‘research’ tree to examine the wood quality and processing in either a plywood or sawmill. Photos by Howard Spencer.

An emerging Forests NSW plantation timber, Eucalyptus dunnii, is going under the microscope as well as the saw in a number of trials which will help determine the future growth regime for the species.
Forests NSW timber improvement researchers, Michael Henson and Dane Thomas, have been spearheading the study into various plantings of the timber and its characteristics in native stands.

“This species is becoming increasingly important to eucalypt hardwood producers worldwide,” Michael said. “It occurs naturally in only a few small disjunct populations in north eastern New South Wales and south eastern Queensland, yet it is one of the dominant cold tolerant planta-tion eucalypt species in parts of South America and China, as well as South Africa where it is used predominantly as pulpwood.”

Dane said that in NSW, Eucalyptus dunnii (more commonly known as Dunn’s white gum) had recently gained favour as an alternative planta-tion species to E. grandis, or flooded gum, because it is more suited to drier and more frost prone sites.

“Forests NSW has established more than 8500 hectares, with the vast majority of these plantations being established since 1994 for the solid wood market,” he said.

E. dunnii achieved acceptable growth performance measured as diameter, height or volume, but growth is only one important attribute of plantation grown timber.

“The end use of the timber also has to be considered,” Michael Henson said.

Historic data from stands aged from three to 34 years were assessed for growth and wood quality using a range of non-destructive and destructive measurements. These measurements were analysed to determine wood properties that may influence grade recovery.

Dane Thomas said that Eucalyptus dunnii, like other species, was becoming more desirable as it aged. The improved characteristics of the wood were related to increased wood density as the tree became older.

“This has implications for the timber industry as it is intended that plantation trees will be harvested at younger ages than native forest trees,” he said. “The predictive ability of these models will be tested with the harvesting of E. dunnii of three different ages – 12, 16 and 34 years and pulp, sawlog and veneer recovery assessed.

“A trial at Boambee near Coffs Harbour will be used to assess solid, veneer and pulp wood properties of this high performing younger stand at age 12 years.

“Two other sites aged 16 and 34 years have been harvested and similar end uses are being evaluated. Non-destructive measurements associated with wood quality traits have been evaluated on these trials at earlier ages.

“We hope these measurements will allow us to determine how to best manage plantations economically, which usually means shorter rotation lengths, while also achieving the higher quality wood usually seen in more mature trees,” Dane said.

“Can we speed up the processes that give us high quality wood?

“Well, we can’t alter the time frame, but we can select tree families for higher density which will give us a stronger wood at an earlier age, and perhaps improvements in other attributes can also be achieved.”

This article appears in the Summer 2007 edition of Bush Telegraph Magazine.