Getting to know the red tingle
Red tingles are among the tallest eucalypts, growing up to 70 metres. They grow only in a 6,000-hectare stretch along the high-rainfall south coast of Western Australia.
Red tingles can live for more than 400 years. They regenerate well after fire – even an intense fire – and form naturally mixed aged forests dominated by large old trees.
But red tingles are sensitive to frequent fires, no matter how mild. Flames can enter the tree and hollow it out, eventually causing its collapse.
The understorey of red tingle forest consists of tall, long-lived shrubs that germinate prolifically after fire. These understoreys thin and open as they age.
The goal of our research was to understand how these changes in red tingle forests affect fire behaviour. To do this, we used an advanced fire modelling tool developed by the lead author of this article, Phillip Zylstra, and his colleagues.
The tool doesn’t use a simple number to characterise a forest’s fuel load. Instead, it uses hundreds of thousands of calculations to determine which plants will ignite – and importantly, which plants won’t ignite but will instead calm the flames.
So what did we find? As the understorey of red tingle forest ages and thins, the lower branches of taller plants “self-prune” – in other words, they shed dead leaves and twigs.
When this litter is on the ground, it begins to decay and poses a lower fire risk than if it were still suspended.
The lower branches of taller plants, once self-pruned, are then less likely to ignite as fuel. Instead, they act as “overstorey shelter” that reduces wind speed and fire severity. In this way, mature forests control fire rather than drive it.
Our study showed that, due to this calming effect, fires in mature red tingle forests could be extinguished by firefighters most of the time.
By contrast, our study showed that prescribed burning in red tingle forests creates dense regrowth, which burns severely during bushfires. In such cases, our study showed
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