Monday, February 9, 2009

Not the hemlock way (?)

Check out the funky shadows.

In Paulik Park there is a western hemlock snag, broken off neatly about seventeen feet above the ground. It's one of many large conifers that make up an acre or so of forest. It's in a relatively sheltered recess at the southern edge of the forest, partially surrounded by similarly-sized hemlock, Douglas fir, Sitka spruce and western red cedar. The ground is low-lying, frequently wet, and the soil is modified from what historically had been the top stratum of a peat bog. The DBH (diameter at breast height) is 23 inches (58 cm). I wonder, how the heck did the top snap off? Wind would seem an obvious answer, but the tree is far from exposed, and trunk failure in response to wind is not the hemlock way.

Different conifers behave differently in the wind (N.B.: these are my untested observations, so don't include any of this in your school reports, kids).

Rigid, straight-armed spruces twist and sway like sky-scrapers.

Wind-damaged Douglas fir.

Douglas firs sacrifice boughs, which go flying. They fall like eighty-pound shuttlecocks, butt-end first, and can land with an impact sufficient to puncture a roof or shatter a flagstone. Straight down onto soil they become instant trees. You don’t want to stand near Douglas firs during high winds.

Western hemlock windthrow.

Hemlocks, with their shallow root systems adapted for drawing water from surface soil, tend to fall over, roots and all. This is the hemock way. Much of the blow-down during the great Stanley Park windstorm of December 2006, especially where there were large areas of windthrow, was second-growth western hemlock.

Back to the Paulik Park mystery snag. Most of the snapped-off trunk was hauled away, but the foot or two immediately beyond the break was left behind. I suppose someone wanted a log with a cleanly cut end. In any case, a ring-count of the remaining bit reveals that when its top snapped off, the tree was 49 +/- 2 years old. A large, mature, but still youthful tree. Could wind have broken its bole?

A tidbit from Wikipedia:"In forestry, windthrow refers to trees uprooted or broken by wind. Breakage of the tree bole instead of uprooting is sometimes called windsnap."

Whimsy: Ha, but is it windsnap if no one hears it?

Ow.



5 comments:

jodi (bloomingwriter) said...

What a neat post! I had never thought so much about how trees do fall or break. We see evidence of this windsnap in some of our softwoods (spruce, generally, I think) but I will have to ask my husband to be sure. He works in his woodlot (by hand, I hasten to add, no clearcutting or anything like that and there's a lot of wind on that ridge. I'll be curious to find out what he says. Thanks for writing about this. It makes a great topic.

Anonymous said...

I'm examining a similar Hemlock break, it happened recently to an Eastern Hemlock on conservation land in central MA. A 85 footer (20" Diam.) snapped off completely, leaving a shattered 6' stub. I'm not convinced a 12/11/08 ice storm here was capable of taking down such strong and healthy Hemlock, I wish I could come up with an answer though. Jim

Hugh said...

Yes, it sounds like a similar mystery.

Anonymous said...

Hello Hugh, I'd like to follow up my 3/5 post: I did find some punky wood near the fracture of the 85' Eastern Hemlock that snapped off here in MA. Case closed on that one!
During investigation with a friend, we came upon another Eastern Hemlock snapped clean leaving a 18' - 20' stub standing..., just like the one in your photo. The rest of it was laying nearby. The broken end looked like 100's of toothpick ends sticking out, hard & pointy, no punk wood on this one.
It had stood among other tall trees. Chock up another. Thanks, Jim

Hugh said...

Jim,

Thanks for the follow-up. It would be interesting to see whatever happened, happen. Something powerful occurred.

Curious indeed.