Australian trees and fire

Cathedral Ranges 10 years after the Black Saturday fires. Photo by author

Hiking through the Cathedral ranges, you can see the devastation the Black Saturday fires caused. Homes have been rebuilt and communities are recovering. What recovered fastest, however, is the vegetation once burnt by the fire.

Fire plays in important role in shaping the Australian landscape. If Australian native trees weren’t adapted, they would have been wiped out many millions of years ago. But what is it about our native species that makes them so well adapted to such rage?

Eucalyptus trees are the one of the most adapted native species to fire. They are specialists at surviving and recovering from fire.

At the base of most Eucalyptus species (and some species of Banksia), buried beneath the ground, are organs called lignotubers. If the above canopy of the tree is damaged by fire, these lignotubers will sprout. This gives Eucalypts a competitive advantage after fire as there will be less competition for light.

Many Eucalyptus species growing in fire prone areas have thick insulating bark. The bark protects the tree from moderate fires. These trees, along with most other Eucalypt species, also have dormant buds beneath the bark called epicormic shoots. These shoots are protected by the bark and quickly sprout if the crown of the tree is damaged.

Unlike other species that drop their fruit for their seed to be absorbed by the soil, species of Banksia, Hakea, and some species Eucalyptus have thick woody fruit/capsules which are retained in the canopy of the tree. The seeds of these trees are protected from fire within the woody capsules. The seeds are released after the fire on the forest floor which is high in nutrients, giving these species an advantage over other trees.

The leaf bases of Grass trees contain resin that doesn’t burn. The ends of leaves will be burnt off and the stem survives the fire. The fire initiates flowering which is to the trees advantage as there will be less competition on the forest floor for light and nutrients.

Grass tree. Photo by author

Acacia trees are pioneer species. They are the first species to rise from the ash. Acacia’s are a nitrogen fixing species that improve the soil fertility. The species is relatively short-lived compared to Eucalypts, which are faster growing and eventually take over once the Wattles have done their job.

Fire stimulates fungal fruiting bodies of many species of native fungi. These fungi release their spores back into the nutrient rich forest floor and begin to spread.

It will be a different story in the Amazon rainforest though. It is estimated that there has been over 76,000 fires in the Amazon in 2019 alone. This is may have devastating consequences for the rainforest.  Plants and trees in the humid forest of the Amazon have no such adaptions fire and it will take much longer for the forest to recover compared to Australian forests.


5 Responses to “Australian trees and fire”

  1. Maria Venn says:

    Thankyou Matt for your article so well written with direct explanations how our Eucalypts & Native species can survive fires. With the abject evidence of changing climate, higher temperatures & more “fire weather”, we need to change our way of managing the bush & forests, both dry & wet because this is going to be our ‘normal’.

  2. Maurice says:

    From the looks of it a deliberate strategy applied by Eucalyptus to ’use’ fire to wipe out competition from other plant species not adapted to survive fires. Each eucalyptus tree essentially a rag dipped in petrol on a bed of kindle waiting for a spark. Very clever, but dangerous.

  3. IAN BENNETT says:

    If the fire is super intense do the trees survive? At what temperature would a tree be so badly affected it would not recover.
    And do the recent massive fires hit that temperature?
    Let me know your answer please
    thank you
    Ian

  4. Matt James says:

    Thanks, Gabriela!

  5. Gabriela Eder says:

    A really nice article. Since I don’t come from Australia, I have asked myself this several times. How can there still be trees here at all? But now I know. It is impressive what Mother Nature is capable of.