The sounds of drought stressed trees.

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Rand
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The sounds of drought stressed trees.

Post by Rand » Thu Apr 18, 2013 10:04 am

When drought hits, trees can suffer—a process that makes sounds. Now, scientists may have found the key to understanding these cries for help.

In the lab, a team of French scientists has captured the ultrasonic noise made by bubbles forming inside water-stressed trees. Because trees also make noises that aren't related to drought impacts, scientists hadn't before been able to discern which sounds are most worrisome. (Watch a video: Drought 101.)

...

According to Ponomarenko, the findings could lead to the design of a handheld device that allows people to diagnose stressed trees using only microphones.
http://news.nationalgeographic.com/news ... ng-sounds/

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edfrank
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Re: The sounds of drought stressed trees.

Post by edfrank » Tue Apr 30, 2013 1:11 pm

Very cool Rand. I posted this on the Facebook page and it got many likes and shares.
"I love science and it pains me to think that so many are terrified of the subject or feel that choosing science means you cannot also choose compassion, or the arts, or be awe by nature. Science is not meant to cure us of mystery, but to reinvent and revigorate it." by Robert M. Sapolsky

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Don
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Re: The sounds of drought stressed trees.

Post by Don » Wed May 01, 2013 1:36 am

Rand-
If we can hear them crying out for water when vapor pressure deficits mount, surely we can measure their wilting and that effect on tree height? I haven't found any research that verifies this, but I suspect it is measureable, and a potential issue for those measuring tree heights with "purported" tenths of a foot accuracy. I suggest that trees' heights change in tenths of a foot diurnally.
Have you thoughts on this?
-Don
Don Bertolette - President/Moderator, WNTS BBS
Restoration Forester (Retired)
Science Center
Grand Canyon National Park

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View my Alaska Big Tree List Webpage at:
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Joe

Re: The sounds of drought stressed trees.

Post by Joe » Wed May 01, 2013 6:57 am

This thread raises an old issue with me- can trees actually "feel" anything? After all, they don't have nerves- but in some way, they still must "feel" something. I'd presume if it's a drought, and it finally rains, their roots feel some sort of joy. And, if it's been a cloudy day, and the sun finally comes out- there must be some sense of that- beyond just the biological activities in the leaves. I recall that day back in '68 when I had a sort of conversation with some trees--- but I didn't think to ask them that question.
Joe

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Rand
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Re: The sounds of drought stressed trees.

Post by Rand » Wed May 01, 2013 7:15 pm

Don wrote:Rand-
If we can hear them crying out for water when vapor pressure deficits mount, surely we can measure their wilting and that effect on tree height? I haven't found any research that verifies this, but I suspect it is measureable, and a potential issue for those measuring tree heights with "purported" tenths of a foot accuracy. I suggest that trees' heights change in tenths of a foot diurnally.
Have you thoughts on this?
-Don
I read a rambling hikers account somewhere, where he noted that the tops of tuliptrees growing from the bottom of a ravine would start to visibly sag when it got dry so I suppose it makes a difference. I imagine it would be most significant in trees would soft light wood, than trees with dense wood like oaks. A fast growing young tree vs a slow growing old tree would probably matter also. Finally if you are talking about a 370' redwood you could probably get tenth of an inch at that size simply out of thermal expansion/contraction.

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dbhguru
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Re: The sounds of drought stressed trees.

Post by dbhguru » Thu May 02, 2013 3:51 pm

Don,

I realize that you understand what is a credible versus non-credible claim on obtaining tree height accuracy, and your use of the word '"purported" is appropriate. For the benefit of others who may read our numerous posts and wonder, some explanations and qualifications are in order. I would admit that we can be a little too loose with our accuracy claims. Explanations are called for.

Hi All,

Do we actually achieve tree height accuracies to a few tenths of a foot as we (me) often claim? Well, we have the methods to attain that accuracy, but they are more labor intensive than just pointing and shooting and proclaiming a result. Have we demonstrated accuracies to these levels in actual field tests shooting into the crowns of trees? Yes, if we accept tape drops as the gold standard. We should emphasize that while under highly controlled tests, we achieve accuracies to within 0.2 to 0.3 feet, it is not clear that this level of accuracy commonly translates to most field measurements. Here is an explanation of the measurement of a very challenging tree where I feel quite confident that I'm within the +/-0.3 foot accuracy range.

First, let me set the stage. Monica's property has 4 white pines, 5 tuliptrees, 9 N. red oaks, 1 red maple, and 1 white ash over 100 feet all within an area of not more than a quarter of an acre. This is the area with the tall trees, so the canopy is dense and only the tops of the white pines can be fairly readily seen. But all individual tree measurements are challenging.

One N. red oak sits within a cluster with the limbs of other oaks and two tuliptrees encroaching into its canopy space. I've shot the tree over the years and have been satisfied with an accuracy within +/- 1.5 feet. But I decided to try to reduce the error range. So, I went out on our deck and set myself up a measuring station. The TruPulses won't penetrate the crown clutter, so I would have to rely on the other units to get distances to the crown point. With a Bushnell and three Nikons I could narrow the distance to the range 139.5 - 141.0 feet. My very best with the TruPulses was one shot of 136 feet.

For the 4 instruments used, the crown distance shots favored the high end of the range, i.e. 141 feet. In addition, my Nikon 440 has been repeatedly tested and for distances such as involved. It shoots long by an average of one foot about 3/4th of the time. I reasoned that if I settled on a distance of 141 - 1 = 140 feet, I'd probably be extremely close. I'd likely have a better than 90% probability of being with inches. The angle shots ranged from 36.9 to 37.4 degrees just pointing and shooting. I had to really steady the units. I got 37.2 degrees consistently. The height works out to 84.6 feet with a probability over 90%.

Because of visibility issues, I had to use the tangent method to the base. A bright lichen patch on the trunk near eye level afforded a good target. Using the Bosch GLR825, I was able to get a distance of 103.31 feet at an angle of 2.4 degrees. Accuracy for the Bosch in this environment is around 2 millimeters. The angle to the base, shot repeated using 4 instruments (TruPulse 200, TruPulse 360, Forestry 550, and Suunto Clinometer) averages 17.2 degrees. I settled on that.

So, let's see, the level distance to the trunk becomes cos(2.4)*103.31 = 103.22 feet and the height below eye level becomes 31.95 feet. The total height becomes 116.6 feet. But we have one more correction to make. Allowing for head or tripod swivel, we must reduce the height by 0.5*(cos(37.2)-cos(17.2))= 0.08 feet. The result is 116.52 feet by pure calculation.

A height range of 116.2 to 116.8 feet carries a probability of greater than 90%. If we want to expand the range to 116 - 117 feet, the probability is above 95%. In many shootings I took without taking a lot of care, just pointed and shot, my range of readings was 115.8 to 117.6. Most fell between 116.2 and 116.8. BTW, I reported a 116.2-foot reading in another post to stay on the conservative side. I frequently do that.

In analyzing readings, I do discard obviously bad readings. For example, If I hit a twig 100 feet away, when most ifk my readings are near 140 feet, I obviously would not include such a reading in an average. The pattern of readings matter. After taking a shot at a target, it is good to shoot of in another direction to reset the instrument. A succession of repeats right on target may not mean as much as one might think. I'll discuss this point in a future post, but it has to do with internal calculation algorithms used in an instruments design.

The TruPulse 360 gave distances to the trunk point of 103.0 or 103.5 feet, sometimes one reading, sometimes the other. So, given the Bosch GLR825 distance of 103.3, the most I would have been off for trunk distance using just the TruPulse would have been 0.3 feet. Apropos to the discussion is the fact that all laser rangefinders mentioned above are periodically checked for accuracy. Over time one gets to know his/her instrument and makes the necessary adjustments for known areas of weakness. I'll soon go through another calibration exercise to discover any diminishment in performance in any of the instruments.

I am certainly not advocating that people go to such lengths in measuring a tree to claim accuracy to within say five-tenths of a foot. I just wanted to explain what is behind my claims for being able to achieve levels to within 0.2 or 0.3 tenths of a foot on trees that are considered very important such as the Jake Swamp pine. More generally, I am satisfied claiming accuracy within +/- 1.0 feet for my Nikons and +/- 0.5 for my TruPulses.

Bob
Robert T. Leverett
Co-founder, Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest
Co-founder, National Cadre

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