Spatial and temporal variation in the health of an endemic Tasmanian tree, Eucalyptus gunnii Hook.f.
Calder , J (2006) Spatial and temporal variation in the health of an endemic Tasmanian tree, Eucalyptus gunnii Hook.f. Honours thesis, University of Tasmania.
Eucalyptus gunnii Hook.f. is a tree endemic to the subalpine regions of Tasmania. A subspecies, E. gunnii spp. divaricata (McAulay & Brett) B.M. Potts, has recently
been listed as endangered, due to extensive dieback over the last few decades. It has
been suggested that the dieback may be in part due to increased intensity and
frequency of droughts brought about by climate change. Examination of weather
records indicated that a prolonged dry period has occurred across in much of the
species' range. Mean annual temperatures have also risen. The timing of dieback,
observed through a time series of aerial photographs, coincided with the timing of
the worst droughts in some regions. However, field surveys of the health of E. gunnii
across its range indicated a stronger negative relationship between livestock grazing
and tree health than between rainfall and tree health. This may have been partly due
to the long term suppression of regeneration in these populations, and therefore the
predominantly old age of many of the trees, and their lower resilience to stress.
Possum defoliation was also implicated as a major agent of decline. Furthermore, the
possibility was raised that herbivorous insects are having a greater impact at higher
altitudes than previously, which could be due to warmer winter temperatures.
Although it was difficult to unravel the effects of climate and land management
changes, the results suggested that we may already be seeing the impacts of climate
change in Tasmania, especially in those environments which have been most heavily
modified by land use.
|Item Type:||Thesis (Honours)|
|Additional Information:||© 2006 the author|
|Deposited By:||Digital Archives Librarian|
|Deposited On:||31 Mar 2010 12:54|
|Last Modified:||31 Mar 2010 12:54|
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