Just Thinkin - Pith Centers

[tim1234]

I was looking at a slice-o-tree today and was wondering why some trees have the pith dead in the middle and some have the pith center way to one side.

Is that because the tree was leaning as it was growing

Just wondering

Tim

[LeeB]

Yup.

[Chuck White]

Could be a leaner, but also, could be caused by the prevailing winds.

That is, the rings on the side that the wind comes from will be closer together than on the opposite side. 

Chuck

[WDH]

There is a chemical called auxin that controls the growth of a tree.  Auxin stimulates growth, especially diameter and shoot growth.  If a tree gets pushed out of vertical, then auxin accumulates on the low side, stimulates more rapid growth on the lower side, thereby causing the tree to straighten back to vertical.  Of course, this results in sweep in the bole.  If the tree is vertical, the auxin concentration is even all the way around the bole, causing even growth rings.  Leaners have wider growth rings on the lower side because the auxin has pooled there via gravity, causing wider rings so the tree can realign itself vertical again.  The orientation of a trees growth ring around the pith are a function of the trees orientation to the vertical and the effect of auxin since tree buds are phototrophic (they seek sunlight).

[LeeB]

 I knew one of them smart guys would come along sooner or later an esplain it all.

[WDH]

Lee,

Your answer was much simpler and just as correct .

[Fla._Deadheader]

 SOooooooo, I've got several young trees that we planted. They are growing very fast, and some are leaning, to the point I have had to pull them back, vertical. Many are 15-20 feet tall, and 2½-3" dia. Place is starting to look like a giant spiderweb.

  How will this affect the Properties of the lumber, when we eventually get to harvest the trees   Will there be a lot of tension-compression wood   The trunks will be a zig-zag shape for the first 4-6 feet, IF I can keep the rest pretty well vertical. Growth rings don't mean much, down here.

  When we were pulling sinkers, we would find pith very near one side of the log, sometimes. Didn't seem to affect the lumber very much, in Cypress

[Gary_C]

Well I have another question along this line. Do different species not get along with each other when placed close together?

I have an apple tree in my yard with a spruce next to it and of course the spruce has grown much taller but it appears like the apple is reaching out it's branches abnormally far towards the spruce while the spruce appears to be trying to get away from the apple tree. The result is the spruce is no longer straight, it's leaning away from the apple.

Perhaps there are other factors involved, but it sure looks like that spruce does not like that apple tree nearby. 

[tim1234]

Thanks LeeB, WDH!

There is a chemical called auxin that controls the growth of a tree. 

Does that mean when there is a lot of Auxin on one side you should start Axe-in

Does this cause reaction wood or is it simply one side of a leaner is under compression and the other is under tension and those forces are stored in the wood after it is cut?  I think this is in line with the question by Gary_C

Tim

[Clark]

Leaning, as WDH explained, and the physiological results of growing on a lean can account for off-center pith.  The other reason that I have seen and it is very common in basswood, is trees growing in clumps.  Most often the side of the trees away from the clump will grow more, leaving the pith farther and farther off-center each year. 

Clark

[WDH]

Thanks LeeB, WDH!

Does this cause reaction wood or is it simply one side of a leaner is under compression and the other is under tension and those forces are stored in the wood after it is cut?  I think this is in line with the question by Gary_C

Tim

The compression and tension wood is formed as you point out, and it does negatively affect the properties of the lumber because of the stresses that are released when sawing the logs.  Sometimes a board will rise up off the cant as you saw along the log, and it will slap you on the back of the head if you don't keep an eye on it .  Reaction wood (tension and compression) also causes fuzzy grain, and it also has a different sheen after it has been planed. 

[BrandonTN]

Hey WDH, what is the name of the chemical that promotes grow of lateral buds....gibberlinns?  Or something like that? Can't remember my tree bio...

[WDH]

Without looking up the spelling, I think that gibberillin is the hormone.  Just think, a year ago, you had no idea that there was such a thing as gibberillin I bet . 

A lot of people, though, probably don't give a basal area about gibberillin .