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Deadly forest fire leads to resurrection of endangered tree

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In 2009 six weeks of wildfires in Victoria, Australia, killed 173 people and injured hundreds more, but the fires may have also led to the resurrection of a rare tree that was previously on a path to extinction.

Only about 670 Buxton silver gum trees (Eucalyptus crenulata) were left in the wild before the devastating Black Sunday bushfires, and they weren’t healthy. After several years of drought at the beginning of the century, a 2005 survey of the trees found no new seedlings. Officials worried that the fires could have put the final nail in the coffin for the endangered trees.

But a survey at the end of 2010 revealed a different story. “The intense fire burnt a significant amount of the topsoil in the Buxton gum’s swampy habitat,” Parks Victoria Ranger in Charge Julie Flack said in a prepared statement. The fires revealed underground lignotubers, nutrient-rich stems that some trees use as a backup system to help them grow new shoots after losing their leaves during a fire. The trees had never been studied below the surface, so the existence of these lignotubers was a pleasant surprise.

In the two years since the fire, the lignotubers have sprouted seedlings, giving the silver gum trees their first real growth in a decade.

The seedlings got another boost in September when the Buxton Silver Gum Reserve, with 600 of the trees, flooded. The silver gum thrives in swampy conditions.

Flack told the Australian Associated Press that the parks service now knows the tree needs both fire and flood in order to survive.

Beyond survival, Flack said, helping the Buxton silver gum to thrive remains a priority. “Fire management over the next decade will be important to allow the new regrowth to mature” and produce seeds, she said. Parks Victoria has also built fences to block out grazing wombats, wallabies and rabbits as well as cut back parasitic dodder laurels (Cassytha melantha), which threatened to choke some of the new growth.

The trees will be surveyed again next month, and again five years from now as part of the ongoing national recovery plan (pdf) for the species.

Photo: Eucalyptus crenulata, by “Melbournian” via Wikimedia Commons under Creative Commons license





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  1. 1. ceriops 1:16 pm 04/22/2011

    so, as so often, its not actually a "deadly" forest fire at all, its part of the cycle of renewal. Now that sounds heartless in view of human life lost, so please dont mistake the sentiment – but as always we have to evaluate all aspects of these "disasters" to see what is ecological reality and what is human perception..

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  2. 2. hoamingin 7:44 am 04/26/2011

    Ceriops,

    That fire was a disaster and it is not easy to say exactly what is "natural". The Australian bush was very different before the first humans arrived about 50,000ya. For many thousands of years aboriginal tribes have regularly burnt areas of country, probably to keep country clear for hunting. Regular burning prevented large buildups of fuel, so they were low intensity.

    Regular burning was "natural", but it made eucalypts the dominant tree species, adapted to fire with dense hardwood trunks, many with underground lignotubers from which new trunks grew when the main trunk was severely damaged. Thick seedpods which split open when burned, released seeds that lay on the ground until heavy rain saturated them with a chemical from ash that triggered germination.

    Aboriginal tribes have not regularly burned the bush for a very long time, so it has reverted to an unnatural state of naturalness. The ferocity of the fire mentioned in this report and other recent fires has been attributed to a lack of controlled burning, leaving massive buildup of fuel. The high intensity of fires is also changing what is "natural" in the Australian bush.

    I was surprised at the surprise by park authorities that these eucalypts have lignotubers, as well as the apparent belief that there is something unusual about many of the other circumstances mentioned in the article. Lignotubers do not send up seedlings. When the main trunk is damaged they send up multiple stems, a growing habit called a mallee. No-one should expect seeds to germinate when it is dry. They germinate after a fire and drenching rain. No doubt that combination evolved because seeds that germinated when there was insufficient water, or before a fire failed to survive the lack of water or a later fire.

    Many eucalypts will happily sit in swampy conditions for a long time, then survive extended drought. Park authorities are unlikely to have to do anything special about fire protection, because it will be some time before the fuel load will rebuild to a level sufficient to support an intense fire. Sounds to me like business as expected.

    David Bainbridge
    http://www.ideasintuitionandthinking.com

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  3. 3. wbarton 6:25 pm 04/26/2011

    Further to hoamingin’s comments, another sign that these fires were anything but natural was the enormous kill rate of advanced mature eucalypts. Many trees greater than 100 years in age were killed, suggesting that these fires were the most intense in at least that period. Many blame climatic conditions, but all else being equal, an increase in ambient temperature of only three or four degrees has no bearing on the temperature on the head of a bushfire. There is only one thing that can account for the intensity of these fires and that is the availability of fuel.

    Parks Victoria are actually a fair way ahead of other agencies in terms of their fire management. Here in NSW the philosophy of fire management seems to be to not let any fire at any time get away. This has led, during the quiet times, to vast tracts of bushland of a similar age, reducing the diversity that many animals require to prosper and during fires, it leads to near total incineration.

    Prior to man’s intervention, the sporadic nature of fires ignited by natural means resulted in a mosaic pattern of age. Not only did this improve habitat diversity, but it could also provide refuge for animals in times of more intense fires where an area that had burnt a year or two before either didn’t burn or didn’t burn with anywhere near the same intensity.

    Perhaps the best way to manage fires is to step back – where possible – and let nature take her course?

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