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Fire

Periodic fire is a natural part of many Australian environments, and plays an important part in the ecology of Sydney’s bushland generally. Cumberland Plain Woodland plants have been exposed to fire during their past, and are adapted to survive and respond in different ways.

Aboriginal people would have set fires in the woodland to burn through prickly shrubs and dry grass, and to flush out kangaroos or wallabies. After the fire, it’s easier to walk through the woodland, with shrubby obstacles removed. Later, after some rain, grasses resprout, attracting kangaroos and wallabies to graze on the new growth and concentrate in the burnt area. Fire made hunting easier.

Our work on the fire responses of individual native species has shown that the majority of species survive fire as adults - 90% - by resprouting either from epicormic shoots, or from persistent rootstocks or tubers. The only species that are killed outright are some annual and short-lived species and a couple of shrub species, particularly the shrub Dodonaea viscosa. Many of the exotic species also resprout, but a higher proportion of them are likely to be killed.

However the main issue is fire frequency, and the time interval between successive fires. Too frequent fires may kill off fire resistant species in their juvenile stage before they have developed fire resistance and fire-sensitive species before they mature and produce more seed. Two of our experimental burns have been 10 years apart, and this does not appear to have caused any loss of native species. (See our research results in Monitoring Impacting events - some effects of fire)

Periodic fire may be used to help control some perennial exotic species particularly *Olea europaea subsp. cuspidata, by killing juvenile plants before they become fire resistant.

On the other hand, in some areas unburned for at least 20 years there has been some decrease in above-ground native species richness in the absence of fire, but it is likely these species remain in the soil seedbank. But fire is not a major driver of floristic change

We earlier thought that fire played the major role in determining recruitment and floristic patterns in the woodland but while it clearly contributes to structural features in the woodland, fire does not appear to lead to extensive floristic turnover or change. Our recent observations are now leading us to the view that periodic drought and drought-breaking rains are major factors in determining recruitment and floristic change in the woodland.

Fire may create suitable open space, reduced canopy cover, and may promote vigorous flowering and seeding of pre-existing plants, thus contributing to subsequent soil seedbanks, but is not a major driver of seedling recruitment.

To see some of the species that resprout after fire, view the seedling picture gallery.

Asterisk * indicates exotic species naturalised at the Australian Botanic Garden.

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