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Bradbury G.,University of Tasmania | Bradbury G.,Cooperative Research Center for Greenhouse Gas Technologies | Potts B.M.,University of Tasmania | Potts B.M.,Cooperative Research Center for Greenhouse Gas Technologies | And 5 more authors.
Holzforschung | Year: 2011

Australian blackwood (Acacia melanoxylon R.Br.) is a high-quality appearance-grade timber species native to eastern Australia. It is characterised by dark-coloured heartwood, with colour varying from pale straw to red-brown and walnut brown, and pale cream-coloured sapwood. This wide range in heartwood colour is expressed as between- and within-tree variation, and is regarded as a problem in markets where colour consistency is important. To understand the genetic and environmental control of heartwood colour, multiple colour measurements were taken from stem cores from 16 open-pollinated family collections of blackwood planted across three 19-year-old progeny trials. Data was analysed with a mixed model with within-tree variation modelled using a three-node cubic spline. Significant genetic, environmental and genetic-by-environment interactions were detected, not only in the variation in between-tree mean heartwood colour but also in the pattern of within-tree heartwood colour variation. In general, heartwood colour became darker, less yellow and more red towards the sapwood/heartwood boundary. To control the between- and within-tree heartwood colour variation in blackwood plantations, care is needed to not only select genotypes with the desired wood colour and colour variation but also site characteristics that allow expression of that colour. © 2011 by Walter de Gruyter Berlin New York.

Bradbury G.J.,University of Tasmania | Potts B.M.,University of Tasmania | Beadle C.L.,CSIRO | Beadle C.L.,Tasmanian Institute for Agricultural Research
Annals of Forest Science | Year: 2011

Context: Australian blackwood (Acacia melanoxylon), is a fast-growing, high-quality, appearance-grade timber species native to eastern Australia. Some of its key wood properties are percentage heartwood, heartwood colour, basic density, wood stiffness and green moisture content. Variation in these properties affects log value, processing and marketing. Aims: This study aims to understand how genetics and environment affect these wood properties. Methods:Stem cores were taken from 16 open-pollinated blackwood families from the island of Tasmania, Australia, which were planted across three 18-year-old progeny trials.Results: Significant effects of genetics, environment and their interaction (GxE) were found for many of the wood properties examined. Both broad-scale and local environmental effects were apparent, with local effects associated with competition and/or allelopathy from a Eucalyptus globulus nurse crop present in one trial. No significant correlation of growth rate (i.e. stem diameter) with wood properties was detected at the family level apart from a positive relationship with heartwood width. At the phenotypic level, there were many significant correlations including growth rate with heartwood width, but not with basic density, or wood stiffness measured as standing tree time of flight. Faster growing trees had yellower heartwood while trees with higher basic and green densities tended to have darker, redder and less yellow heartwood. Conclusion: Both genetic and environment factors affect key wood properties of Australian blackwood, but in most cases these effects were independent of growth rate. © 2011 INRA and Springer Science+Business Media B.V.

Bradbury G.J.,University of Tasmania | Potts B.M.,University of Tasmania | Beadle C.L.,CSIRO | Beadle C.L.,Tasmanian Institute for Agricultural Research
Forestry | Year: 2010

Australian blackwood (Acacia melanoxylon R.Br.) is a high-quality appearance-grade hardwood species native to eastern Australia. Heartwood colour varies from pale cream, straw, golden-brown, red-brown and walnut, with prominent annual growth rings; sapwood colour is generally pale cream. This wide colour range in heartwood is associated with both between- and within-tree variation. Colorimetry was used to quantify the phenotypic range and variation in heartwood and sapwood colour in stem cores taken from 19-year-old trees belonging to 16 open-pollinated families. The trees were located in three progeny trials in northern Tasmania, Australia. Cores were also visually classified into four colour and four colour variability classes. Both heartwood and sapwood had very wide colour ranges and high between- and within-tree colour variation. Analysis of variance showed that colorimetry can be successfully used to quantify heartwood colour and colour variability, with lightness and redness differing significantly between visual colour grades, while within-tree maximum colour difference (maximum ΔE76) was the best derived colour trait in discriminating grades of heartwood colour variation. Correlations between within-tree sapwood and heartwood colour were significant, but moderate to low, precluding the possibility of assessing heartwood colour in standing trees by measuring sapwood colour. © 2010 Institute of Chartered Foresters, All rights reserved.

Bradbury G.J.,University of Tasmania | Beadle C.L.,CSIRO | Beadle C.L.,Tasmanian Institute for Agricultural Research | Potts B.M.,University of Tasmania
New Forests | Year: 2010

Blackwood (Acacia melanoxylon R. Br.) is a high-quality appearance-grade timber species native to eastern Australia. Wide variation in its survival, growth and form, together with issues related to site selection and intensive silvicultural management, limit progress in its domestication and commercial development. To determine the effect of genetics on these traits, five blackwood progeny trials in northern Tasmania, Australia, aged between 15 and 19 years were assessed. All trials contained a variety of open-pollinated, single-tree, family collections from Tasmania, with one trial containing a selection of provenances from mainland Australia. Significant genetic variation in survival, growth and form were found. This variation was partly explained by broad scale adaptive differences across the wide geographic distribution of blackwood. Blackwood from the tropical northern range of the species had poor survival in cool temperate Tasmania. Significant differences in survival between Tasmanian seedlots were also observed. Among the Tasmanian seedlots, those from low altitudes grew better than those from high altitudes, while those from the north-east of Tasmania had significantly better growth rates than seedlots from the south-east. Seedlots from the north-west seed zone had intermediate growth rates. Significant genetic differences in the proportion of trees with single stems, and the number of large branches in the lower stem were found between Tasmanian seedlots. Early-age seedlot height was significantly positively correlated with mid-age diameter. Stem form was improved under nurse crops, but even open-grown blackwood had low percentages of trees of excellent form. These results indicate that at the broad scale, climatic matching of seed source with planting site is clearly important, however, within Tasmania there was no evidence that seedlots collected from the same region as the trials outperformed those from other regions. © 2009 Springer Science+Business Media B.V.

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