Australian trees and fire
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.
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.