Nature’s clock
Before it’s too late, we’re giving two of Tasmania’s lesser-known species the opportunity to thrive - the Tasmanian Bertya (Bertya tasmanica subsp. tasmanica) and the South Esk Pine (Callitris oblonga subsp. oblonga)
The twisting trunks of the York Gums form a record of their resilience; some of these trees have seen hundreds of mid-west Western Australia’s hot, dry summers. The species are endemic to the state. However, land clearing for agriculture has greatly reduced their populations, and they’re now part of a nationally protected ecological community.
Thankfully, pockets of York Gum woodlands remain, some of which can be found at Charles Darwin Reserve, Badimia Country.
Since 2003, we've been managing the 68,600-hectare reserve, which is located within one of only two Global Biodiversity Hotspots in Australia. It's home to a diverse mix of vegetation communities, over 230 mammals, reptiles, birds and amphibians, and 680 plant species.
“When I retired, a volunteering opportunity came up at Charles Darwin in 2009. I did that, and I was awestruck by the experience,” says Dr Richard Thomas, who began caretaking at the reserve shortly after volunteering.
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Ecologist Fiamma Riviera with volunteers John Koch (measuring York Gum trunk) and Richard Thomas (recording results on clipboard). By Fiamma Riviera.
While looking after the reserve, Richard’s curiosity was sparked by surveys completed on the reserve’s York Gums. In 2007, university student Marcel Hollenbach meticulously surveyed the trees along 10 transects for a thesis. This research complemented the earlier work of volunteer Dr Len Warren, who, in 2005, studied the woodlands to monitor the impact of our early management.
“I was caretaking and thought, ‘I’ll just see what one of Marcel’s transects looks like.’ It turned out that the death rates of the trees followed an interesting and predictable relationship,” says Richard.
In 2017, Richard completed a comprehensive repeat of Marcel’s survey, building knowledge of how York Gums survive, regenerate and grow. This year, the monitoring was completed again.
“We’re now able to get ideas of how the trees are actually performing,” explains Richard. Approximately 1000 trees have been studied, which has led to many insights, including the natural process of forest thinning – the younger trees competed and died off more frequently, while only 3% of the older trees appeared to die over the 10-year monitoring period.
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Canopy of a mature York Gum tree at Charles Darwin Reserve. By Fiamma Riviera.
Trees operate on longer time scales than humans; even the lowest estimates place some of the trees on the reserve at over 250 years old. We can only begin to understand the impact of processes, such as fire, with long-term monitoring.
In a climate changed world, where we're experiencing increased fire frequency and intensity, this knowledge is vital.
“York Gums are killed by fire, but they also need it to recruit the next generation of trees, which is important for the ongoing existence of the woodlands,” says restoration ecologist Dr Fiamma Riviera, who has been involved in the recent surveys.
“By monitoring the growth of the trees and matching this with known fire histories, we can better infer the age of the woodlands and the appropriate burning frequency. We'll then use this information to adapt our fire management,” adds Fiamma.
After this year’s survey, Richard and Len plan to publish the findings of their work. We, and the natural values we protect across our reserve network, are indebted to our volunteers. Their generosity helps to give nature the time to heal and thrive.
What does Richard think about volunteering? “It’s a terrific growth opportunity,” he says. Both for the volunteers, and the woodlands themselves.
Bushtracks spring 2024
