AusBonsai

Just looked at SteveW's thread on "Utah Junipers"...great photo's...These trees are growing thru meer cracks...can the restriction of tap roots increase base girth ? Instead of removal of tap root, can the use of a tube/ring be used to choke the root to help swell the trees base, I've noticed on young trees that this happens, maybe utilising the tap roots growing factor helps. The trees base is about the same as the tap root, but if the tap root is restricted, the girth goes to the base and it swells. The root can be removed anytime

Good observations.

I guess this is what happens when people do air layers with the tourniquet method.

but the swelling you would get would be better don't you think from restricting the tap root, lateral roots are still there. The overall vigour of the tree would be enhanced? Is the tap root of any significance to the strength/core of the tree?

The tap root drives down into the eart and helps secure he tree to the ground.

The fine hair roots are what gives the tree it's nutrients.

but the swelling you would get would be better don't you think from restricting the tap root, lateral roots are still there. The overall vigour of the tree would be enhanced

This does not seem to hold true. After a couple of years there is no real difference whether you restrict above or below the roots. As long as new roots can form above the restriction the tree will still grow just as well and the stronger lateral roots seems to thicken the base of the trunk more than if it has vertical roots.

The tap root drives down into the eart and helps secure he tree to the ground.

I'm pretty sure the whole concept of 'tap root' is a myth for most trees. Sure we see a radicle start to grow downward from a seed but that seems to rapidly be converted into lateral roots that go wherever they are needed. Most stay quite close to the surface where most of the nutrients are. Some may go deeper if the plant needs to get to water down deeper.
I have dug up many trees, large and small. I've also inspected lots that have been blown down in storms. I don't seem to find 'tap roots' on any of these trees. Strongest roots seem to be shallow laterals with a few going down up to a metre. I'm pretty sure it is the strong lateral spread of roots that helps balance the tree and hold it into the ground.

yeah I've seen a lot of trees blown/knocked over and wondered what had happened to the tap root, if the tree reaches a certain age then foregoes the tap for the laterals or it's just rotted or got eaten...anyway I'll experiment on some tube stock from the nursery