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The ecology and biogeography of Athrotaxis D. Don.

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Cullen, Philip J.(Philip James) (1987) The ecology and biogeography of Athrotaxis D. Don. Coursework Master thesis, University of Tasmania.

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Abstract

The coniferous tree species Athrotaxis cupressoides
and Athrotaxis selaginoides and a probable hybrid, A.
laxifolia, form the genus Athrotaxis, which is endemic to
Tasmania. These species are found in a wide range of
cool temperate rainforest, subalpine scrub, and alpine
heath communities in central, western, and southern
Tasmania. Athrotaxis species are slow growing, extremely
long lived, and very fire sensitive.
The floristic composition, site characteristics, and
demographic structure of Athrotaxis populations were
investigated at 57 rainforest and subalpine scrub stands
dominated by either A. cupressoides or A. selaginoides.
The distribution of A. cupressoides largely coincides
with those areas occupied by trees where extreme frosts
are most common. In areas where both species occur, A.
cupressoides is more likely to be found at higher
altitudes or in cold valley bottoms. Subsequent trials
demonstrated that A. cupressoides seedlings are more
frost resistant than A. selaginoides seedlings. Field
observations and preliminary experimental investigations
indicated that neither differences in drought resistance
nor tolerance to waterlogging are important in
determining the relative distributions of these two
species.
For both species seed dispersal is restricted to
areas within a few tens of metres of parent trees, except
when seeds fall into flowing water. The demographic
structure of Athrotaxis populations is strongly related
to the floristic composition of the communities in which
they are found. A. selaginoides relies on gap formation
or catastrophic disturbance for regeneration
opportunities in forests dominated by evergreen species
(thamnic and callidendrous rainforests). However, in

forests containing a high proportion of the deciduous
tree, Nothofagus.gunnii, (implicate rainforests) and in
subalpine scrub communities A. selaginoides regenerates
continuously. A. cupressoides regenerates continuously
in open montane rainforests, often by producing root
suckers. This species is also capable of regeneration
following catastrophic disturbance. However, stands of
A. cupressoides on the Central Plateau of Tasmania have
no, or low, numbers of seedling sized individuals.
Trials suggest that this regeneration failure is due to
grazing by both introduced and native mammals. In
undisturbed thamnic and implicate rainforests the species
cannot regenerate successfully. Demographic structure
and floristic composition of these communities indicates
that they are seral stages in a succession from open
montane to thamnic and implicate communites without A.
cupressoides.
It is probable that the colder conditions and a
higher incidence of catastrophic disturbance during full
glacial and interstadial climates would have been
advantageous to Athrotaxis species. However, the loss of
Athrotaxis populations and lack of regeneration in many
cases must be attributed to the activites of Europeans in
Tasmania and not to an inability to survive under the
present climate.

Item Type: Thesis (Coursework Master)
Keywords: Taxodiaceae, Conifers
Copyright Holders: The Author
Copyright Information:

Copyright 1987 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.Sc.)--University of Tasmania, 1988. Bibliography: leaves 135-149

Date Deposited: 08 Dec 2014 23:58
Last Modified: 09 May 2016 06:47
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