I have noticed, like many others, the counter-clockwise twist of many trees here in Virginia. No one (at least per Google) seems to know exactly why. There are lots of theories and speculation regarding whether trees in the southern hemisphere grow with a clockwise twist.
So does anyone know, from experience or observation, if trees in the southern hemisphere actually grow in this manner?
Thanks,
Tim Henshaw
Roanoke, Virginia
Replies
I'm planning a trip to South Africa next year, so I'll try to remember to take notes on any twisted trees that I see. In the meantime, perhaps some of our Oz and Kiwi members might be able to tell us which way their trees twist.
There may be an external effect that causes the twist, and trees may twist the opposite way in the Southern Hemisphere, but it's almost certainly not the Coriolis effect acting directly on the trees. The Coriolis force is utterly miniscule on something the size of a tree. Except under laboratory conditions, it can only be observed with large-scale phenomenon, like ocean currents, hurricanes, etc.
However, one of the hypotheses regarding tree twisting is that it's caused by a combination of the prevailing wind direction (from the west in mid-latitudes) and the fact that trees in the Northern Hemisphere have more growth on their southern sides, because that's the side that gets the most sun. The west wind and the denser growth on the south side of the tree combine to produce a net torque that tends to twist the tree in a counterclockwise direction (when viewed from above). Since trees in the Southern Hemisphere have denser growth on their north sides, the torque would be in the opposite direction.
The Coriolis effect is part of what determines the direction of the winds, so it's possible that the Coriolis effect indirectly causes the twisting in this way.
Another thought occurs to me: Many of the molecules that participate in the basic biochemistry of life have a handedness: The molecules exist in two mirror-image forms, but living organisms make use of only one of the two. So, in a sense, life itself has a handedness. If that were the cause of the twist, then trees in the Southern Hemisphere would twist in the same direction as trees in the Northern Hemisphere.
-Steve
Edited 9/14/2007 11:07 pm ET by saschafer
Edited 9/14/2007 11:10 pm ET by saschafer
"Except under laboratory conditions, it can only be observed with large-scale phenomenon, like ocean currents, hurricanes, etc."
What about my bathroom sink?------------------------------------
It would indeed be a tragedy if the history of the human race proved to be nothing more than the story of an ape playing with a box of matches on a petrol dump. ~David Ormsby Gore
<What about my bathroom sink?>Hey, Be careful, and don't get your head caught in it, It will twist you right up like a Christmas ribbon. HaEven worse is that flushy thing. I hate it when I have to get my head down close to it. You know you are having a bad day when................
"Wheres the money Lebowski!"
"What about my bathroom sink?"
That's an urban legend. If you work through the numbers, you find that the presence of even tiny irregularities in the surface, etc. completely swamp the Coriolis force.
(And, just in case anyone is wondering, it's no easier to balance an egg on its end during the equinoxes as it is at any other time of year.)
-Steve
"What about my bathroom sink?"I believe the poster you were responding to explained your bathroom sink phenomenon -- "except under lavatory conditions"
Clockwise is like right and left terms on a boat are better referred to as port or starboard. Maybe a right or left helix, as in thread of a screw or drill would work better.
I have also wondered about this for quite some time, and can only speculate from what I have observed, and I have not completely come to any conclusions, but will be happy to share some of my thoughts.
First, lets think small, and look at some flowering plants. Have you ever driven down the highway, and noticed that all of those yellow wild-flowers are facing the rising or setting Sun? They will point their face to the Sun, and follow it across the sky. OK, I know they don't have eyes, but, how do dey know? I am sure that mother-nature has done this to attract more pollinating insects to those flowers. The insects can see the bright color if it is reflecting back more light from the Sun.
But what drives this action? I have speculated that the heat from the Sun dries the stem just below the blossom, causing some moisture loss / shrinkage on that side, which would tilt the heads toward the Sun. I think a good easy test would be to set up an experiment where you shaded the stem below the blossom, then set a mirror up behind it which reflected the light back onto the stem from the back side, and see which way the flower head faced.
On a larger level, If trees also had some miniscule daily force pulling them around on a daily cycle, this might give some impetus to what you are asking.
On the other-hand, I find that forest trees seem to grow straighter up, with grain that stays straight up the bole longitudinally, while edge, or open area trees tend to be more likely to twist, but the worst twisted trees are the ones which grow in really windy locations.
Here are my thoughts on the wind connection. Trees growing in a forest surrounded by other trees will sway back and fourth in the direction relative to the way the wind blows, relative to the gust, but without much rotational force.
However, If a tree is near the corner of a house, it will get a lot of rotational force due to the wind being deflected off of buildings etc. The same is true for trees growing along the edge of clearings. Edge of clearing trees put off more limbs as they reach out for the abundant light toward the opening, so when the wind blows, there is likely to be a lot of rotational forces.
When you consider those twisting forces down the length of a straight grain stem, this is likely to cause separation down the grain. Consequently, I think nature has found a way to cope with this by inducing spiraling grain. This would make the tree more flexible up and down the trunk, as well as less prone to split, by virtually growing a plywood tree, because it usually is a dynamic thing, changing directions every year, growing in cross-banding. It would at the same time, make the tree a little more flexible up and down the trunk, because the wood can flex more across the grain, than it would from the huge bending force at the base of a large tree, with a big canopy in a hard wind. More flex could be a good thing in windy conditions.
There are a number of other things going on which can contribute to the wild or changing grain thing, when you look at different locations of a tree. Take for instance, when a tree is a sapling. It may have a trunk the size of your wrist, straight up from the earth, and roots that radiate straight out just below the ground. I am sure you know how trees grow, by adding cells in the cambium layer just under the bark, so it grows larger just by adding to the outside of what is already there.
Hardwood trees tend to be stronger in compression, while soft are better in tension, so they will grow different when it comes to leaning or limbs / roots etc.
So back to the sapling. Say it is a hardwood, and something like a walnut or maple that we all love to find good figure in. When the trees is small, there may be say 100 cells per inch along the grain, so out along the roots, for say 24" there would be 2400 cells, then up the tree for another two feet there is the same thing. So as the tree grows over the next 100 years maybe it has grown to say 4' diameter. That would mean that the trunk is now out that 24" on the radius, so those 2400 cells along that root line are really getting crowded, while those same roots are growing faster on top, because that is where they are strongest, so the ones up the trunk are getting scrunched up also.
If there is not something in nature that tells certain cells not to divide each time that they normally would, they have no choice but to start deviating away from the longitudinal direction, so this will cause a lot of figure in wood.
The same is true for the under-side of large limbs which grow straight out on hardwoods. So all of you fellows who collect your own turning woods, start looking for the really large trees which have made it to the end of their natural life span, and learn to choose the best of what nature has to offer.
So in conclusion, if you only remember one thing about what I have written. When you come across a really twisted tree, just take note of its location and what is around it, and think about weather / wind patterns, or other factors that could induce a challenge to straight up growth. For really old trees, you have to take in consideration what the situation was like maybe several hundred years ago.
You know, trees record lots of data each year that they grow. I have a couple of friends that are dendrochronologist. That is a scientist who studies tree-rings, mainly for their wether data. I really like talking to these guys, and sharing thoughts.
By the way, if you cut wood as in trees, and live anywhere in the mid-south. That early warm spell, and Easter Freeze this year should have induced a feature called a frost ring. This would be a light or small ring or double terminal parenchyma that might look like a major drought year to someone a hundred years from now, if there was no written weather record to refer to. So take note if it shows up in your area. I have not harvested any trees lately to see if they are here in AR,.
Sorry it got so long with this, but actually, this might actually be the abbreviated version of my thoughts. I have never written this down before, and I am not a scientist, only a close observer of Nature.
However, I must also say that I love to read any scientific articles related to wood, and I think there are some which should be questioned and need to be challenged. Many of them were written by people / students who may have been trained in science, but just had limited life experience, and wanted to prove what they believed, and made the conclusions match their expectations.
If anyone knows someone needing a doctorate thesis and would like a subject for research, please link us up.
So rather than coriolis, which would be induced by the
earth rotating under the atmosphere somewhat like the tides in the oceans, only now pulling the equatorial winds Easterly, then reversing through the sub-tropics. It likely has more to do with closeness of isobars. The closer the isobars, the greater the gradient, or ~ stronger the wind.
"...I find that forest trees seem to grow straighter up, with grain that stays straight up the bole longitudinally, while edge, or open area trees tend to be more likely to twist..."Certain varieties of eucalyptus trees, even when growing in dense forests, grow twisted. It has nothing to do with wind, proximity to clearings or north/south sunlight, it's just their nature to grow that way.BruceT
"Have you ever driven down the highway, and noticed that all of those yellow wild-flowers are facing the rising or setting Sun? They will point their face to the Sun, and follow it across the sky. OK, I know they don't have eyes, but, how do dey know?"
This phenomenon is known as "phototropism," and is an active area of research in plant biology (if you're interested in the details, look up "phototropism" at Wikipedia as a starting point). While the plants don't have eyes, they do have photoreceptors, so they can sense the direction of incoming light. On a daily basis, they "move" towards the light by means of chemical changes in the cell wall structure that causes the cells on the dark side of a stem to expand, so the stem as a whole bends towards the light. Other, different factors are involved in longer-term growth towards the light.
-Steve
I TALKED TO THE TREES,
THEY CAME AND TOOK ME AWAY.
GOOD BYeeeeeeeeeeeee
Regds. Boysie Slan Leat.I'm never always right but i'm always never wrong. Boysiere
Thanks Steve. I will have to spend some more time checking that out. It is good to have a word for it. I had also wondered about the negative aspect as in the vine tendency toward shade as well. I figured it probably senced a static charge from something nearby. I wonder if there are studies going related to that.
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