This is something I considered when hard pruning my JBP entry although I did push it very hard to try to get the results I was after in the one year time frame.From Bonsai4me https://www.bonsai4me.com/AdvTech/ATPine%20Pruning.html
It is better to be conservative when hard-pruning and reducing Pines. Severe reduction without allowing for recovery time can be fatal particularly with old or large trees. Reduce large trunks and/or branches gradually over a number of seasons so that the tree is able to adjust.
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So far so good. Infact the tree still looks vibrant. I figure the health and juvenility of the tree has worked in my favour.
I am in no way trying to debunk what seems to be sound advice but I do want to try and understand what reason there is that reducing a pine severely in one go is detrimental.
is it the possible sap loss? Does it have some detrimental affect on how the tree is able to function?
Any ideas?