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A young plantation of Eucalyptus nitens
(shining gum) at Surrey Hills in north-west Tasmania.
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Eucalyptus nitens (shining gum) is widely planted in
temperate regions of the southern hemisphere, principally for
pulpwood production. It is the
second most widely planted hardwood species in
Australia and the main species currently planted in
Tasmania. The species is distributed in Victoria and NSW
with various races identified on the basis of geography and
genetic differences (
Hamilton et al. 2008). A
meta-analysis summarising the performance of these
E.
nitens races and the closely related
E.
denticulata in 85 field trials across the world was
published recently (
Hamilton et al. 2011).
The meta-analysis used published and unpublished data from
nursery and field trials. The field trials were in Chile,
China, Italy, Lesotho, New Zealand, South Africa and Zimbabwe, and
were planted in both summer- and winter-rainfall
environments. Data were available from a considerable number
of trials for growth traits (73 for diameter), but information was
also available on wood-properties, tree-architecture, fitness and
morphological/developmental traits. Meta-analyses were undertaken
on these data to gauge the significance of differences among races
across trials as well as the race × rainfall zone
interaction.
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The juvenile foliage of E. nitens
(shining gum) has closed apical buds (shown). This is a key
trait that differentiates this species from E. globulus
(blue gum) which has an open apical bud at this stage.
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The meta-analysis only detected a significant race × rainfall
zone interaction for growth traits. In general, Central Victorian
E. nitens populations outperformed New South Wales
E.
nitens populations in winter-rainfall zones, but this ranking
was reversed in summer-rainfall zones. On average,
E.
denticulata grew less rapidly than the best-performing
E.
nitens races, particularly in winter-rainfall zones.
Differences among the
E. nitens races were detected in
basic density, a commercially important trait, but these
differences were small in magnitude. Significant differences among
races were also evident in branch size and stem form
(straightness).
Eucalyptus denticulata races had
significantly thinner branches than all
E. nitens races
except the Southern Central Victorian race, and Central Victorian
E. nitens races generally had the straightest stems. The
small number of trials represented for most traits limited the
power of meta-analyses but where significant differences among
races were detected these are likely to represent consistent and
robust differences across a broad range of environments.
This meta-analysis of genetic-based trait differences between
the E. nitens races completes our review of the genetic
resources and breeding (Hamilton et al. 2008), and
quantitative genetic diversity both within (Hamilton and
Potts 2008) and between (
Hamilton et al. 2011) races of this important forestry
species.
References
Hamilton MG, Potts BM (2008) Review of Eucalyptus nitens
genetic parameters. New Zealand Journal of Forestry
Science 38, 102-119.
Hamilton M, Joyce K, Williams D, Dutkowski G, Potts B (2008)
Achievements in forest tree improvement in Australia and New
Zealand - 9. Genetic improvement of Eucalyptus nitens in
Australia. Australian Forestry 71,
82-93.
Hamilton M, Dutkowski G, Joyce K, Potts B (2011) Meta-analysis of
racial variation in Eucalyptus nitens and E.
denticulata. New Zealand Journal of Forestry Science
41, 217-230.
BIOBUZZ ISSUE FIFTEEN, DECEMBER 2011