The results of using trees depdnds on the tree. There is a huge difference between Carolina Pines and SEA Mohagony. I, as I am sure AM and others can attest to instances when someone got the bright idea of cutting down trees with claymores to clear an LZ. The result was singed bark and perhaps a few frag wounds of varying severity.

I got bored on a radio relay sight and fired an entire case of M-79 rounds at a large limb about 50 - 100 M away. Once I was zeroed in I hit it almost every shot. The result was again a little bark knocked off of the branch and a shoulder I couldn't move for a few days.
I have a film clip of a demo ambush I used in RVN. If I figure out how to cut out what I want I'll post it. We placed WP in fromt of the claymores. The film is beautiful showing the arc of the WP . We fired the mines, everyone emptied a magazine into the KZ and then we split. I did this several times and was never seriously pursued.