In The Natural Interest
Fire in the Bush
by Greg Stone
Amongst the numerous
news reports broadcast during the fire crisis of late
December and early January were statements to the effect that
bushland - more specifically a national park - had '
been totally destroyed by fire'.
the National Parks and Wildlife Service were quick to remind
journalists that fire is a part of the natural life-cycle of
much of our local bushland and is in fact necessary
for the long-term health and vitality of communities
of native vegetation. Fire can bring about a dramatic increase
in the population of new plants which replace the older
members of the community, thus extending its life.
Most of the remaining bushland
communities in the Tallong -Wingello - Penrose - Canyonleigh
area occur on dry, well-drained and infertile soils based on
Hawkesbury Sandstone, and most of the plant
species growing in these fire-prone (hard-leaved) communities
have been especially designed with 'bushfire
In the December edition of the
Southern Highland Way we considered how plants survive and
recover after a bushfire. In response to a fire, plants can be
placed in either of the two basic groups - 'sprouters
' and 'seeders'. The 'sprouters
' are those plants that send out new vegetative growth
after the fire, whereas the 'seeders' obviously survive by
preserving seeds in a variety of ways which allow germination
to occur following fire damage. So in relation to fire in the
bush the word 'destroyed' is probably not quite correct.
'Modified' or 'rejuvenated' may be more
However, this is not to say that
fire is always beneficial to the bush, because under certain
conditions it is possible that fire may damage or even destroy
a community of natural vegetation. Factors to be considered by
those responsible for fire management in the bush are the
frequency of fires, the intensity of the fire and the timing of
Frequency of Fire
A plant must first reach reproductive maturity if it is to
regenerate itself following a fire i.e. it must be old enough
to have produced seed or 'sprouting' mechanisms such as
epicormic buds or rhizomes. This
age of reproductive maturity differs between species found in
typical vegetation in this region may vary from two years
(Acacia sp.) up to fifteen years (Banksia
serrata). This means that all the species in
a patch of bush burnt this year will begin to regenerate almost
immediately - but what will happen if a similar fire occurs in
three years time?
Those species which have matured quickly will
again be able to respond and regenerate, but those still
reproductively immature will not. So although the bush will
grow back, there will be a number of species missing. As
ecologists put it, the vegetation community will move from
complexity (many species of plants) to
simplicity (fewer species of plants). Therefore
both the frequency of fires - whether wildfire or for hazard
reduction - and the lifecycle of plants need to be considered
by the managers of bushland areas.
Intensity of the Fire
Low intensity fires are often regularly applied to the bush
during Autumn or Spring for the purpose of hazzard
reduction i.e. reducing the amount of fuel present so
as to keep potential bushfire intensities low and manageable.
These frequent low-intensity fires may significantly
modify the plant community in several ways. The
fires may destroy shrubs yet not be hot enough to
stimulate seedlings to germinate, but will still allow
regeneration from rhizomes and other underground rootstocks.
After several such low-intensity burns the bush may
consequently become dominated by grasses and ferns. Shrub and
tree which regenerate from epicormic buds, lignotubers and
rootstocks may become exhausted after frequent fires and
therefore also be lost to the community. Again, the bush moves
from complexity to simplicity.
Timing of the Fire
Spring is critically reproductive time for many plant species -
bearing flowers or producing immature fruit. Regular hazard
reduction burning during this season can obviously have a
adverse effect upon a bushland community as some species
will be prevented from reproducing.
Fire Planning and Management
Nobody can accurately foresee the occurrence of fires and
conditions such as those recently experienced, but in the
meantime we do have the opportunity to carefully develop plans
and then implement fire management strategies in areas of
natural vegetation that will serve to both minimize the risk to
life and property whilst also preserving our bushland.
C/- P. O. Wingello
Wingello N.S.W. 2579