Regeneration of Tasmanian Alpine Vegetation after Fire

1
Regeneration of Tasmanian Alpine Vegetation
after Fire
Mathew Irwin, Department of Biological and
Physical Sciences, University of Southern
Queensland, Australia
Introduction Alpine vegetation is very restricted
in Australia, covering only 0.15 of the land
surface. It occurs at an altitude of 2000-2200 m
on the mainland through to 700-1350 m in
Tasmania. Alpine vegetation in Tasmania is
globally unusual due to it largely being
dominated by small hard leaved-shrubs, rather
than the normal herbs and grasses of other alpine
areas.1 Fires are not common in Tasmanian alpine
environments, thus relatively few species are
tolerant to its effects when it does occur. Fires
in central Tasmania in 1961, caused local
extinctions of the endemic Pencil Pine,
Athrotaxis cupressoides, a species which is not
fire tolerant. It is estimated that with this
plants current seed dispersal rate, the
regeneration of this species will take thousands
of years.2 The aim of this study was to determine
the length of time it would take in order for an
area that has been devastated by fire to fully
regenerate.
Results From 1978 to 1998, bare ground and
exposed rock cover decreased substantially by an
average of 1.48 per year in the plots burned in
1962 1967 and by 1.05 per year in the plots
burned in 1947 (Figure 2). Upright-shrub cover
increased in both areas burned in 1947 and 1962,
while mat-shrub cover, herb cover and graminoid
(grass) cover decreased in both burnt sites
(Figure 2). In both 1978 and 1998, upright-shrub
cover and mat-shrub cover were greater in the
areas burnt in 1947 than in the areas burnt in
1962. It will take longer than 50 years for each
of the alpine sites to fully regenerate to the
levels of structure experienced before the fires
of 1947 and 1962.
Figure 2. Changes in cover of lifeform groups and
bare ground by time since last fire
Discussion The decrease in rock and ground cover
indicated that as time progressed from the
initial burning of a site, the lower the
percentage of cover became. This was due to the
colonisation of plant species in an area over
time. As the plants spread over an area, they
reduced the percentage of rock and ground cover
present. The first plants to colonise an area
after a fire are the herbs and grasses. As time
progresses, shrubs begin to populate the area. As
the shrub cover increases, it reduces the amount
of light filtering through to the lower levels
and thus causes a decline in herb and grass
cover. The increase in vegetation cover in the
1947 sites compared to 1962 sites, indicated that
large amounts of time were needed in order for a
site to fully regenerate after such a disturbance
as fire. When fire sensitive sites such as alpine
habitats experience a fire, it destroys all plant
life present in the area. The regeneration of the
site then takes time, and in habitats that are as
sensitive as alpine habitats, the time for total
regeneration to occur could take many, many years.
Methods In 1978 1998, replicate 15 5 x 5 metre
quadrats were placed at random distances from the
boundaries of areas both burnt and not burnt by
fires in 1962 or 1967. These quadrats were
situated on a plateau of Mount Wellington,
Tasmania (Figure 1). The frequencies, maximum
heights, maximum and minimum diameters of all
individual shrubs rooted in each quadrat, along
with the amount of exposed rock and bare ground
present, were measured in both 1978 1998. The
areas unburnt in 1962 and 1967 coincided with
shrubs burnt in the same area in 1947. This
separation in time between the 1947 and 1962
fires provided data on the regeneration of alpine
vegetation of Mount Wellington, Tasmania.
Conclusion Alpine habitats in Tasmania are
extremely sensitive to the effects of fire. If
burnt, it can be concluded that it would take in
excess of 50 years before the vegetation in the
area to fully regenerate to the levels
experienced before the fire.
References 1 Department of the Environment, Sport
and Territories. (1994). Australias
Biodiversity An overview of selected significant
components. National Capital Printing,
Canberra. 2 Department of the Environment, Sport
and Territories. (1996). Fire Biodiversity The
Effects and Effectiveness of Fire Management.
National Capital Printing, Canberra.
Acknowledgements Original article Kirkpatrick,
K., Bridle, K., and Wild, S. (2002). Succession
after fire in alpine vegetation on Mount
Wellington, Tasmania. Australian Journal of
Botany, 50, 145-154.
Figure 1. Map of study area showing location of
sample sites
Completed as part of BIO3314 Terrestrial Ecology
assessment - October, 2003