Hollow Trees

[Larry]

I’m logging a stand of mixed oak in the 20" dbh range and up.  High percentage are hollow...even the white oak.  What causes the tree to be hollow?  Anyway to tell if a tree is hollow before it gets whacked off?

[SwampDonkey]

Signs can be stress cracks, deep furrow in the but and maybe some spiral twist to the right on old trees. Causes can be mechanical damage, fungal infection and insect damage all the regular abuse a growing tree has to endure. The chipmunks sure like those old hollow trees, they build sub-terrainean tunnels that usually lead into the hollowed but, were they make their nest and store their caches. Used to see them a lot in the old hollowed out apple orchard trees. One would go into the ground and all the sudden he is poking his head out of the trunk where an old branch died and broke off. My brother sees them a lot in his old yard apple trees he tells me.

[Texas Ranger]

In Arkansas the probability is it is fire related, burn the mountain, injure the tree, and the rot takes over.

To tell the difference, we used a thing call The Missouri Butt Pat.  Put your ear against the trunk, and tap with knife or ax as far on the other side of the tree as possible.  Solid wood gives a sort of "chunk" hard sound, hollow has a, well, hollow sound.  Try it a couple of times and you can tell the difference.

[SwampDonkey]

Wouldn't there be a fire scar?

[Ron Wenrich]

Not necessarily.  What generally happens is the uphill side burns hot enough to kill the cambial layer, which allows for the rot to start.  That eventually heals and the bark looks pretty much like it should. 

If you're in a stand with a lot of hollow trees, I vote for fire damage.

The best way to tell if a tree is hollow is to sound it out.  Take an ax and hammer on the tree.  You'll be able to hear the difference.  I always carry an axe when marking timber. 

Another thing to look for is swelled knots.  That's always an indicator for rot. 

[SwampDonkey]

Guess I'd have to see it to know what to look for. Unless the bark is thick enough I wouldn't think a tree could conceal the evidence of fire damage too well. White pine is a 'fire' tree and I always find a scar and some big enough to stand inside the living tree. Probably a hardwood forest wouldn't have as intense fire. Probably the inner bark is what's being killed otherwise a dead cambium can't grow new wood except maybe if it's not too severe it can callus and compartmentalize around it.

[Fla._Deadheader]

no value in hollowlogs, Larry 

[Larry]

That really purty...looks expensive also.

[Texas Ranger]

Fire scar in small trees will heal over, rot is compartmentalised, bigger trees can heal over as well, but there will be a bark "show" for a while.  Can be particularly insidious when the roots near or on the surface get burned, allowing rot in as well.  This one will pretty well infect most of the existing stem.  Tight bark species are more obvious than the rough barked ones.

[stonebroke]

 to improve your woodlot wouldn't you want to cut all the hollow trees down. I don't think they are going to get any better.

Stonebroke

[customsawyer]

If it is just one here and there you can look up to see if there is a place where an old limb was broken off and let the water get in it will make it rot most times if it is a old wound.

[farmerdoug]

The small woodlots around here often have hollow trees.  The loggers in this area also contribute the cause to graising cattle and horses in the woods.  Farmers often did it to make use of the feed they thought the cattle would get there.  From what I understand the crushing of the the smaller roots of the trees let the rot into the tree.  I beleive equipment in the woods does the same thing too.

Farmerdoug

[Tom]

Hollow trees was common in the south when cypress logging was taking place.   The trees were hughe and only harvested from the butt swell to the first limbs, usually.  The logger would strike the tree with the butt of his axe to determine if it was hollow.  Most of the big cypress that we have standing today were those that were determined to be hollow.

[SwampDonkey]

You can go into stands of old fir here and they will most all be rotten because of declining vigor and then fungal attack. You'll have a lot of old snags. If it is mixed with white birch they will die after the fir begins to break up, similar to taking too much out of a birch stand and have it sun scald. If you see a main stem or two up in a white birch that is dead or declining the but will have advanced rot, sometimes in pockets though. Dominant birch will sometimes be ok, but usually yellow birch, not white. They left a few scattered white birch in my cedar stand/softwoods which were harvested. they later died or are a pretty poor mess. My huge yellow birch was bigger than the cedar and not a dead branch on it.

[Clark]

I'll second the vote for grazing damage.  I saw it a lot in the midwest and often in smaller woodlots but certainly not limited to small woodlots only.  I think the soil compaction does a number on smaller trees and probably kills a major branch or two of the root system on bigger trees that survive.  The dead root then rots and it continues up into the tree.  Then throw a horse in there and they start chewing the bark off trees.  What a mess!  It disgusts me to see farmers grazing their woods.

Clark

[OneWithWood]

Grazing, maybe.  Fire, probably.  Fire was used to clear fields and much of it would run up a ridge and get into the trees.  All the hollow trees on my property show signs of fire.
Fun trees to fall 

[SwampDonkey]

I also agree that root damage by cattle or harvest machinery can be a contributing factor. I agree fire is a cause to, not so sure fire damage is so easily concealed. Call me the skeptic.  Of course it depends to on the type of forest floor. Most hardwood ground have very thin forest floor and mixed or softwood have deeper forest floor which could allow a fire to burn longer and deeper to kill the roots. On a thin forest floor, any fire than will kill main lateral roots will likely do a number on the trunk. The thinner the floor however, the faster the fire passes by I think. Just my thoughts.

[Ron Scott]

Hollow trees result from a tree injury of any sort and then the spread of decay. Fungi will cause wood decay and insects will assist with wood removal.

[jim king]

We have several species in the Amazon that the vast majority are hollow.  Nobody has come up with the answer yet.

[rebocardo]

>  insects will assist with wood removal.

That is what I usually see with hollow white oak where I live. I think the prolonged drought weakens the oaks, then maybe a disease, and then the carpentar ants move in. I rarely see termites in white oak. Though the red oaks seem to get the ants the worse.

What I have noticed is the majority of the nest in the hollow trees seems to be in the upper trunk and branches and I would think it would be in the bottom closer to the ground. But, it is not. 

[SwampDonkey]

Their nest is nearer the ground here because of the cold weather in winter. Snow pack helps insulate them, but wood is a good insulator in itself. Their galleries can go a ways up the trunk though. I've seen exit holes 4 feet off the ground in live spruce. Piles of sawdust below.