I have recently moved to the arid centre of Australia, where I'm dealing with issues related to sacred trees of native australian aboriginals. One issue I would like to address to my collegues: what fill material can one use in hollow trees, leaving the first 2 metres above ground open, and creating a seal to the hollow trunk higher up in the tree, which is fire resistant? Are there any options other than concrete and foam, which are not my preferred methods of filling? I would appreciate advice from collegues who dealt with similar issues. Thanks.

Reply to post by Astrid Hamm, on June 09, 2000 at 21:56:45:

Currently, the accepted practice is to not fill hollow trees with any material.

You ask about fire resistance so I am giong to make a jump and wonder if you are concerned that the hollow tree will act like a chimney and burn out if a grounc fire starts. This would probably happen. In this case, I might consider installing a heavy steel plate inside the tree to "plug the chimney".

Why are you wondering about filling the cavity?

Tom

Reply to post by Tom Dunlap, on June 09, 2000 at 21:56:45:

Tom,
the issue is as follows: sacred trees in the northern territory in Australia are used by Aboriginals for storage, but also to make fires inside hollow trees. In the past months we had a lot of rain, which lead to an increased fuel load in the area (an unusual abundance of grasses are present this year, which are slowly drying out). I was asked the question about fire resistant materials not to preserve the tree, but to minimise the risk of bushfires, as the fire travels upwards in the tree, and sparks can spread around very easily, due to strong winds we have here in winter. We can't stop the Aboriginals to have fires in the trees, and we are not allowed to close the hollows in sacred trees, as they are used for shelter and storage as well. Now you've got the whole story.
Astrid

Reply to post by Astrid Hamm, on June 10, 2000 at 10:44:42:

There is anecdotal information that when cavity filling was regularly practiced long term performanc of the installation was enhanced if the tree surgeon charred the interior wood surface with a blow torch before filling. It might well be that the periodic burning actually serves to preserve these sacred trees. The "ecology" inherent in ancient practices might be much more complex than readily apparent.

I'd be inclined to research some sort of spark arrestor at the top end IF you really want to stop the fires. Is there an unrecognized function in the periodic brush burns? Can you get the aboriginals on board with preventing the fires?

Reply to post by Scott Cullen, on June 13, 2000 at 02:09:07:

Scott,

the problem is, that it is a cultural issue, aboringinals have made fires in hollow tree trunks for a long time, never mind the ecological issues we're dealing with now, which, especially this year, are bush fires (accidental!)due to the high fuel load after the heavy rains we had. Now (our winter) all grasses are dried out, it's fairly cold here, and that's why they make fires in trees, using it as shelter from the cold. All trees are surrounded by lots of grasses this year, so the bushfire danger is very high. But because sacred sites/ sacred trees are such a political issue, nobody will tell the aboriginals not to do it. I initially suggested to fence the holes off, but that is a no no! I thought somebody over your way might have had similar dealings with north-american indians.

Reply to post by Astrid Hamm, on June 10, 2000 at 10:44:42:

REading this, the first thought was some sort of spark arrester, as Scott suggested. They are used to cap fireplace chimneys, and I would imagine that a device could be made of some material to funnel the air flow through the spark arrester without significantly affecting the chimney effect.

As to fire potential, preventing the fires is NOT the answer. 12 years ago Yellowstone Park burned because of a supression plan that allowed huge amounts of fuel to develop. Grass fires are quick and not terribly hot, if there isn't much wood. Clearing a small area immediately around the trees will reduce the risk of them catching and burning. That would seem do-able (but then I'm not there!) and in the best interest of the aboriginals, since it protects their sacred trees.

Reply to post by Scott Cullen, on June 13, 2000 at 02:09:07:

Charring of the wood inside a cavity- cauterizing- goes back a long way, and was often used by the early surgeons who filled cavities. They thought it 'hardened' the wood. It worked! If you didn't ignite the tree.

The charring does several things. It breaks some of the chemical bonds releasing water and some nitrogen, leaving the carbon behind. It also kills the fungi that are rotting the wood. With less fungus left behind and a surface that new fungal spores can't grow on or in, there would be less decay after treatment. The problem was mostly one of uniform application. Tough to get it right and even. Also depended on getting most of the decayed wood out first. (source: personal discourse with George Maurer, deceased, Arborist)

Reply to post by Russ Carlson, on June 13, 2000 at 06:34:55:

Russ,

Your talents never cease to amaze me. Tell us your secret of having a discourse with a deceased arborist,

lew

Reply to post by lewbloch, on June 14, 2000 at 23:24:38:

Sorry, Lew. That's off topic here. You'll have to visit my other site, www.psychicarborist.com.

Reply to post by Russ Carlson, on June 13, 2000 at 02:09:07:

Thanks guys for your advice - I'll have a chat about this to the people responsible. But I think I have to clarify one thing which seems to be misunderstood: the bushfires developing here are not for fuelload-reduction, they are accidental(see: human impact in ecology). The issue is to raise the awareness of people, but find some 'pracical' solution to help with the problem.Not sure whether I could ask for the aboriginals not to make fires inside trees - that is a political issue here!