AusBonsai

Like Jarrod said, most has been said above...and very useful information-- thanks. I've noted that another factor in survival/recovery rate has to do with (as tinto suggested) the roots as well. It seems to me that the different varieties have varying threshholds: a mugo which has had its roots pruned recently has a far less chance of surviving than a jbp undergoing a branch prune of similar severity with a parallel recent root disturbance. In a slate of most to least sensitive to branch prune with respect to root disturbance would be: WP, mugo, radiata, jbp..... but I'm FAR from a pine expert....it's just based on observation and (alas) post-mortems. ( I have a wp on its own roots and am so paranoid about it I'll probably never prune a branch!) So I guess all I'm adding here is that in addition to age, overall tree health, and location of branch to be pruned, I'd add the criterion of looking at where the tree is roots-wise. Has it been root pruned in the last two years? Is it in desperate need of repot? Those factors can be added to the DO OR DON'T mix.

The balancing of supply and demand as one does when removing a similar percentage of top growth when pruning the roots of deciduous trees, doesn't seem to work with Pinus. It's been said but I can only reiterate - Prune nearly back to some healthy foliage and only in small amounts at that. A scientific explanation eludes me to account for this dying back but we know that it does happen. Therefore, time the pruning correctly to the semi-dormant period, remove little, leave foliage and only do it infrequently.

Hey Guys
I asked this question over various forums and found that most just excepted that Pines could not be cut back hard and had never considered why. But Eventually I did get a very interesting and colaborated explination.
Apparently after cutting back a pine hard the roots are able to suck up more water than the foliage can handle and the tree drowns. This results in the death of the tree.
Two solutions where offered as tried and true methods. Prune the roots back hard as well as you can see Leong has done in his video or keep the soil dry after hard pruning the pine. Obviously the aim of both methods is to stop the tree sucking up so much water and stop it drowning.

Now who is game to try it