Nice try! But no chicken dinnerI'm with Oso here and I think this is key here.
I also think that the reason why many defoliate the escape branches/leader is to reduce shading on the main tree. Not to reduce (or maximize) the growth/thickening of the branch/trunk.
And mature bonsai (life Adair's pine) may act differently because they are pot bound. That's why we plant trees in tiny pots right? reduce/constrain/minimize their growth...
Now, I'm no expert. Far from it. But I do have a brain and a background in Biology... It seems illogical that reducing the branches on the leader will increase its thickening, since we are essentially removing lots of terminal buds, all contributing for the growth of that brach.
Also, before we even think about competition, we need to show that resources are limiting (which is seldom the case with our bonsai I'd assume). Otherwise there is no competition. What would they be competing for?
my two pence
My tree is not pot bound. Sure, it’s in a bonsai pot, but it’s been regularly repotted over the past three or four years. It’s been moved from it’s “everyday” pot, to a show pot, then back to the “everyday”, and back into the current show pot. The growth of the foliage over those years has been pretty much the same, actually increasing in twig count, and needle density. There is more “leaf surface” now than there ever has been during my time of ownership. Yet the trunk hasn’t fattened, nor have most of the branches. How do I know? I wired most of the larger branches over 4 years ago. I’m just now removing that wire. But, it hasn’t cut in! Some of the smaller branches showed some wire scars, but none of the larger ones.
How can this be?
Decandling. I fertilizer heavily in the seypring. The tree grows vigorous new spring candles, and strong candles. Then, in early July, I cut them all off.
You see, the tree expended a lot of energy producing new solar receptors to make food for future growth. While new needles are growing, they use more energy than they produce. It’s during the second half of the summer and fall when they produce more food than they consume. That’s when the wood is put on the trunk. If you watch wired branches carefully, you will see that they get wire scars faster in the fall that other seasons.
Now, by decandling, I’ve just removed all those expensive new shoots and needles! The tree has no choice but to try and replace them as quickly as possible! Summer’s running out! And so it does. By October, it has produced new shoots there the old ones had been. Just in time to go dormant! The tree spent what energy it had to make that second set of shoots and needles. And just as they started to mature, it’s time to shut down for the winter. They never got a chance to collect and store excess energy on the form of wood!
So, little if any trunk thickening. Little if any old wound callous formation. The tree simply had more important this to do. Build photoreceptors!