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Fire kills Victoria's forest giants

e.obliqua seedlings from ashes

Figure 1. Eucalyptus obliqua seedlings dutifully rising from the ashes.  (Image: Des Stackpole)

Before and after - Wallaby creek

Figure 2.  Before and after the fire at Wallaby Creek. The view from 50 m above the ground in what was the tallest forest in Victoria (Wallaby Creek catchment, Kinglake National Park).  (Images: Steve Sillett)

Watts River burnt one week prior

Figure 3. A rare view of the Watts River from the Maroondah Highway at Fernshaw.  This was burnt in the week following Black Saturday under very mild conditions allowing the fire sensitive E. viminalis and E. regnans forest to survive. The fire origin was a lightning strike near Healesville that occurred on the evening of Black Saturday. (Image: Des Stackpole)

­ While the Royal Commission enquiry into the Victorian bushfires (February 2009) continues, forest researchers and managers are in the field, assessing the damage to Victoria’s forests. Michael Ryan (VicForests) is one such manager who is assessing the impact of the fires on Victoria’s public forests.  He remains optimistic that, despite the large areas of mature and regrowth forests that have been killed, recruitment of new seedlings will be good.  The 2009 fires coincided with excellent seed crops in most of the forests, so only the youngest forests will require active intervention in the form of supplementary seed.  Already, with a small amount of follow-up rain, forest floors are covered with tiny seedlings (Fig. 1).

It is estimated that the fires on 7th February killed 100% of the mature and old growth ash forests within the Wallaby Creek catchment and 50% of the mature and old growth ash forests within the O’Shannassy catchment, including the Australian mainland’s top ten tallest trees.  Brett Mifsud, one of Australia’s tall tree experts, reports that there are no trees taller than 90 metres remaining in Victoria.  At Wallaby Creek, an area renowned for it’s spectacularly tall and lush old growth forests, there are possibly over 100 trees that survived: one 87.5 m tall tree that is just alive and 2 others over 85 m are the tallest (Fig. 2).  In the days after 7th February, much of the regrowth in the Armstrong Creek catchment was killed, half of Tarago catchment and 75% of Maroondah catchment was burnt, but at a lower intensity.  The fires have caused a patchwork effect of forest survival in the landscape.  Generally, stands burnt on the Black Saturday itself destroyed stands completely (ie, 100% dead trees).  Stands burnt after Black Saturday when conditions had moderated received a respectable “reduction burn” in the understorey, allowing close to 100% survival of the trees (Fig. 3).  Sometimes very young regrowth stands did survive on the Black Saturday due to a lack of fuel while the nearby mature and old growth forests were devastated.

Biobuzz issue nine, august 2009