white pine snagThanks to Ron Kilby, who was hiking near Howard Prairie recently and brought in this photo and a question about what in the heck caused those odd patterns. Honestly, I was stumped. And thanks to Ellen Goheen, who circulated it to her USFS colleagues, one of whom, Eric Watrud, compiled this list of intriguing possibilities:

-wire or chain link fence
-Christmas tree
-Coriolis Effect
-multiple lightning strikes
-plantation netting
-popular bear marking spot
-crazy tree that couldn’t decide if it was xylem or phloem
-rare and elusive Scottish argyle barkless fir
-muscular tree that went to the gym regularly
-scoring from boundary marking
-no rational explanation
-sasquatch using nunchucks
*ribbing/reinforcing to address wind shear – please see below for further explanation.

Eventually, a plausible explanation emerged from Barb Lachenbruch, professor of Wood Science, at OSU:

“Western white pine, especially near treeline, does that. We call them ‘argyle pines’. The best guess is that they are ribbing/reinforcing that help the tree in sheer in the wind.

If you stand with your arms out and twist them but keep your feet in place, you’ll feel the angle where the tension is. These ribs are at the right angle to help deal with the extra force. Another way would be to make spiral grain, which does the same thing–spiral grain puts the highest strength (which is in the axial direction of the cells) at an angle to the stem, but helps with the torsion when the tree twists from the wind.

This is all arm waving (ha-ha) but it make sense. Bob Leichti was the first to explain it to me and now I tell people his explanation.”
Apparently this pattern is not uncommon in white pine. Thanks, Barb, and I am once again amazed by those products of evolutionary bioengineering called trees.

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