It is that time of year. Warming weather accelerates vascular activity, which makes foliage heavier. If evapotranspiration is inhibited by humidity and a lack of wind, the foliage can get too heavy to be supported by the trees that produce it. All that increasing weight can bring down big limbs or entire trees at the most unexpected times. The process is spontaneous limb failure.
By ‘unexpected’, I mean that it happens when there is no wind. It is startling because broken limbs and fallen trees are typically associated with wind rather than a lack of it. Gentle wind actually accelerates evapotranspiration, which relives affected vegetation of some of its weight and susceptibility to spontaneous limb failure. Aridity helps too, by absorbing more moisture.
Of course, even a gentle breeze at the wrong time can have disastrous results for vegetation that is already about to succumb to spontaneous limb failure. I suspect that is what happened here, since the air was not completely still at the time. It was just a bit warmer than it had been, and slightly more humid than typical. It is too late and pointless to analyze the situation now.
At about noon on Thursday, someone who works nearby alerted me to the sound a a big tree falling. I was in the same neighborhood, but was driving by with the radio on. The tree is precisely where I was told it would be. No one was nearby when it fell. Damage was originally minimal, with a portion of trail displaced by roots, and a rail on a bridge crushed by the trunk.
By ‘originally’, I mean that this was not the extent of the damage. After barricading the trails and road leading to the site, and leaving, we heard another loud crash from the same location as a bay tree that had been leaning against the already fallen fir tree collapsed in pieces on top of the whole mess. Fortunately, the damage to the bridge, although worse, is not too terribly bad.
Tony Tomeo 
You’ve assessed it as not too bad, but it doesn’t look great, even to one used to understatement.
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Well, it only broke a section of rail off of the bridge. The rest of the bridge is fine. Most of the rest of the tree fell into the forest. Only a bit of it needs to be removed from another part of the trail. It will be difficult to remove it without causing more damage, but we will figure it out. I used to inspect fallen trees regularly, and was more often than not impressed by how trees seemed to find the best spot to land where they would cause the least damage. There were a few that seemed intend to cause as much damage as possible. I wrote an article about it a while ago, after observing that trees hate Porsche, but have never hurt a Buick. They really seem to dislike certain cars, but not others.
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That idea made me smile.
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Do you mean this?
https://tonytomeo.com/2018/11/04/trees-hate-cars/
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That is a big tree that came down. It happened at our neighbor’s house once. A tree just fell without bad weather or wind.
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It is more common than most realize. As an arborist, I can sort of sense the sort of weather that will likely cause some of it. Right now, I expect broken limbs in some of the deciduous riparian trees, but for different reasons. They are heavy with new foliage, and are now getting wet with a slight bit of late rain.
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Reblogged this on Tony Tomeo and commented:
As bad as this was three years ago, it is not as extreme as what came down this last winter.
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