The Blustery Storm of January 1, 1986
|I think the January 1, 1986 storm was particularly memorable because of the genral lack of weather throughout much of December. Below is what I noted in my journal from this timeframe. Note the enthusiasm for the possibility of an incoming storm at the end of the second paragraph:|
Examination of the January 1, 1986 Tree Damage
It is noteworthy that "meager" 35 mph gusts broke at least one living tree in The Forest, took out a large, dead birch, and snapped at least one fairly large branch from an alder tree. In the Southern Woodlot, an alder lost 16 or so feet of its top (4.5" diameter at base, 16.5" circumference); this top was dead, abscessed from a living base. By Beaufort Sale standards, one might estimate wind speeds of 47 mph or greater from these damage results. There is no reason to think that my anemometers were reading low, as the peak gust of 35 mph falls well within the range of what was typical out of this storm in the Puget Lowlands of Washington State [see Appendix, below]. One might be inclined to eliminate the dead birch from the estimations because the wood was probably beginning to rot, and thus weaken. But the living birch--that's a different story.
If the winds were strong enough to break that one tree, then what reasons prevented other birches in the vicinity from also falling? It's been too long for me to recall all the specific details about that one birch tree, but maybe the living Betula was diseased, or happened to be more exposed than others. These kinds of details about trees, which are living, dynamic organisms, prone to much variation, make it very difficult to estimate wind speeds from dendrological data alone. Indeed, from my studies, I've noticed that trees of various species have different levels of tolerance to wind, and those tolerances change with the seasons. For example, springtime black cottonwoods, Populus trichocarpa, can lose large branches to 25 mph gusts, and entire tops in 30-35 mph gusts, though in winter, when they've been denuded by the autumn foliage drop, they're loath to break a large branch even in a 40 mph gale. Alder trees, generally Alnus rubra, and A. sinuata, appear to be among the trees more susceptable to lower wind speeds, and I've seen bigleaf maples, Acer macrophyllum, drop big branches, say up to 20' long and potentially damaging, in 30-35 mph springtime winds. On the more tolerant side of things appears to be the western red cedar, Thuja plicata, which seems to weather even 50 mph gales without too much loss.
Here's the specimen catalog for some of the January 1, 1986 tree damage (woodlots not listed escaped heavy damage from this windstorm):
Specimen #: 01JAN1986001
Field Description: The length of tree on the ground is 45' 6". This specimen landed on the main trail through The Forest. The tip is 5" from the chain-link fence on the east border. The base landed right by the remaining trunk. Tree appears healthy.
Conclusion: No clear reason for this tree to have been singled out for breakage.
Specimen #: 01JAN1986002
Field Description: The length this tree is about 40'. This specimen landed on another birch, bending the victim. There is a lot of heartwood rot in the broken specimen. A ground sucker tree from the same root mass, and about 30' tall, is still standing.
Conclusion: Tree broke due to being mostly dead and rotting.
The Forest Notes: An old rotting birch (Betula papyrifera) branch, 19" in circumference, fell from a long-dead tree and broke into three sections upon hitting the ground. The bigleaf maple (Acer macrophyllum) on the eastern extreme (south-central) lost a branch 1.5" in diameter and about 9' long.
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Specimen #: 01JAN1986003
Field Description: The top that came off of this alder is dead, though the lower portion of the tree is still alive.
Conclusion: Tree most likely broke due to having a dead portion.
Last Modified: February 26, 2003