Subproject leader returns
After six months of
maternity leave, Julianne O'Reilly Wapstra has returned to work,
looking fit and healthy, and ready to get her "other" life
back.
Welcome back Julianne!
Anti-herbivore strategies in Eucalyptus globulus: the
effects of genetics and ontogeny on resistance and plant
compensation to browsing
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Christina Borzak will examine post-browsing
regrowth as an anti-herbivore strategy
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The browsing group has a new recruit - Christina
Borzak - who is embarking on a PhD into non-lethal methods of
mammalian browsing control in Tasmanian plantations. Her
project will examine aspects of how Eucalyptus globulus
defends itself against browsing by native mammals. While
chemical and physical properties provide important resistance
strategies, compensatory mechanisms are also considered to play a
significant role in recovery from browsing damage.
Past work by the integrated browsing management team has shown that
there is a genetic basis to chemical resistance in E.
globulus, and this has been linked to browsing by mammals. To
build on this previous knowledge, Christina will investigate
aspects of resistance across plants of various ages and will
examine plants' abilities to compensate for damage through regrowth
as an anti-herbivore strategy. To kick-start the project, she
is currently assessing plant recovery from damage in a
control-pollinated E. globulus progeny trial in Gladstone,
north east Tasmania. The eight month old trial was exposed to
varying degrees of mammalian browsing within three months of
planting. Using a paired sampling design, she will observe
plant responses to browsing and assess any ecological consequences,
such as increased plant susceptibility to insectivory or
disease.
Future work will use E. globulus seedling trials to assess
ontogenetic development of chemical and physical resistance to
mammalian browsing, as well as variation in compensatory regrowth
in response to damage. In addition to this, Christina will
look at trade-offs between resistance and post-browsing recovery
among E. globulus races, such as differences in resource
allocation to lignotuber development and defence. It sounds
like Christina is going to be very busy for the next three
years. Good luck and welcome, Christina!
Net stockings all the rage in fashionable
plantations
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Seedlings ready to be planted - note the red
fish-net stockings on the more fashion-conscious individuals
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Alison Miller has been hard at work assessing
results from eight field sites that were planted in spring 2007 as
part of the TCFA “Manipulating seedling palatability for
non-lethal browsing management” project (see Biobuzz #2,
4). These sites have been monitored regularly to assess browsing
damage, seedling height, characteristics of the surrounding
vegetation and herbivore presence (through scat counts).
Preliminary analysis of the first eight weeks of data show that the
four main characteristics investigated (nursery fertiliser,
naturally resistant seedling stock, chemical repellent and seedling
stockings) all had a significant effect on browsing. Browsing
was most reduced/delayed on seedlings with stockings. Chemical
repellent was also quite effective at reducing browsing, and its
effect was greatly enhanced when applied to seedlings which
received low nursery fertiliser. More detailed analyses will
be conducted once monitoring wraps up in May 2008. Industry
partners will visit one of the trial sites in April as part of a
TCFA field day. Planning is currently underway for a second
set of field trials, which will commence winter/spring 2008.
These will be conducted on coupes from a range of industry
partners, and will further explore the most effective combinations
of seedling manipulation strategies found in the current
trials.
Different possum populations have the same taste in
eucalypts
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Poss enjoys a tasty treat from Jeeralang North
...
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Natasha Wiggins has been working on the TCFA
(Tasmanian Community Forest Agreement: Research into Alternatives
to 1080 Program) funded project ‘Do all possums show the
same aversions for genetically resistant seedling
stock?’ A common question and concern raised by
tree growers is whether browser aversion for genetically sourced
seedling stock is consistent state-wide, or do different
populations of browsers show different preferences depending on
whether they have coexisted with particular populations of
eucalypts? Natasha has been investigating the seedling
preferences of two populations of the common brushtail possum
(Trichosurus vulpecula) from north-east and south-east
Tasmania. Possums were offered E. globulus seedlings
grown from seed sourced from four geographic and genetically
distinct localities (Blue Gum Hill, St Helens, Jeeralang North,
Parker Spur). Results indicate that both possum populations
demonstrated similar intake preferences across the seedling types
(Jeeralang North = Parker Spur = Blue Gum Hill < St Helens),
suggesting that the susceptibility ranking of germplasm should
remain stable across different possum browsing
populations.
Students
Christina
Borzak (PhD student at the University of Tasmania) is looking
at genetics, ontogeny and the ability of plants to compensate for
damage caused by browsing.
Affiliated students
Naomi
Glancy (PhD student at the University of Tasmania)
isinvestigating the genetic and chemical basis of browsing
resistance of Eucalyptus nitens.
Jon Humphreys
(PhD student at the University of Tasmania) is studying how to use
near-infrared reflectance spectroscopy (NIRS) to predict chemistry
and other attributes of eucalypt foliage.
