In that picture the Big Mountain Maple is flanked by two smaller Mountain Maples. Imagine if he was completely surrounded by them an other trees in a woods? How many lower branches would he have, Answer none. As the little ones surrounding him would spread out to grab sunshine. IF he grew any he'd drop them as they weren't producing food and where a waste of energy.
So what would he do to get sunshine? If sunshine were food?
How would he do that? Get to Sunshine? Grow tall fast.
What's the best way to do that? Single Stem and not fight over lower sunshine.
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Then when you get up above the ankle bitters sun steeling son's a bitches? Oh, I don't know grow a canopy and shade them out, and steel all their Sunshine food.
Point is the big ones are big, because they grow strait up and don't get wide, and win the race to the sun, and eventually kill everybody below them.
So...the bigger the tree you are going to model in Tane....loose the side branches, and put a sunshine gathering umbrella on their head. Because there are gonna kill everybody below them once they do.
SO the rule to building trees in Tane: The little guys are fat and wide, the big guys are strait and tall with no branches on the side, mankind has grown to call them lumber.