In the wake of fuel reduction burning last Autumn, we asked “Can a low intensity, planned burn be too hot?“. Early indications suggested that at least some of last season’s planned burns had a devastating impact on high conservation value, old-growth trees in the forest. Those observations, though concerning, were only anecdotal; no-one had gone into the forest after the burn to systematically assess it’s impact. So, last Sunday, 22nd November 2015, our Citizen Science project got underway. Our goal was to survey 50 m wide transects through the Tames Rd planned burn, count the number of trees greater than 70 cm in diameter and assess how the fire had impacted them. In particular, we wanted to know these things about each tree:
- Was it dead or alive before the fire,
- Was it burnt by the planned burn,
- If it was alive before the burn, was it now still alive, or dead,
- was it still standing, or had it been felled by the fire?
We split into two groups of about six, armed with tape-measures, gps, data-sheets, camera, picnic lunch and First Aid kit. The going was pretty slow, as the forest contained about 20 trees/ha greater than 70 cm dbh. Much of this forest had been heavily logged, perhaps 40-50 years ago, and regeneration from that disturbance has created a dense stand of poles. We had planned to survey at least two 1 km transects, but it took each group about 3 hours to walk a 550 m transect – there were lots of trees to measure!
So, what did we find? Here are some images, with captions, to give you a visual sense of the survey and the planned burn’s impact (eight months on). Click an image to view the slide-show.
Overall, there seemed to be very many trees either killed or severely burnt by the planned burn. In total, we measured 122 trees along 1.1 km of transect, 50 m wide; equivalent to 5.5 ha of forest. Three tree species were present: Victorian Blue Gum (Eucalyptus bicostata), Manna Gum (E. viminalis) and Narrow-leaf Peppermint (E. radiata). We also encountered quite a number of stags (dead, standing trees).
The two largest trees encountered along the transect were both Manna Gums (1.3 and 1.4 m dbh). Trees of such size are key ecological elements of our forest and their presence is significant to the overall health of the forest. Conversely, their loss is disastrous! Both of these Manna Gums were killed by the planned burn.
Moreover, seven of the 16 biggest trees along the transect (all over 1 m dbh) that were burnt by the planned burn, were killed by the planned burn. Does this sound like good forest management?
To be fair, we’ve only surveyed a 1.1 km transect, so we’ll be going back to collect more data soon. Let us know if you’d like to join in.
To be continued….