Making rings....

[mrcaptainbob]

So just how does a growth ring come bout? I see the bark, then a rather large ring of soft, white wood on this old oak, but then the next rings are really thin. And, of coarse, there's a dark side to every light side of growth ring. Is the dark side what used to be bark? Does the outer bark, or whatever eventually becomes a growth ring get compressed with age?

[Ljohnsaw]

From waaaaaayyyy back, high school biology.  There is a layer under the bark called the cambium layer.  It produces a layer of cells in both directions (toward the center and toward the outside).  Toward the center, IIRC, is the phloem (sp) and the outside is the xylem.  The xylem take the water up to the leaves and the phloem takes the food (produced by the chloroplast) down to the roots.  Every year, a new set is produced - the old xylem becomes the inner bark, the old phloem becomes the heart wood (which is dead).

Did I get that right, professor?

[beenthere]

To add to ljohnsaw:
Here is a pic of red oak, showing the annual rings and the visible rays radiating from the pith outward.
You can see the lighter cells that actually are open early wood vessels that for red oak form a distinctive band, and later in the growing cycle they are smaller and tighter together.
The following spring, the tree begins growth again and those large earlywood cells grow first. So a growth ring will be visible by counting these bands of earlywood and latewood vessels.
The radiating rays are typical identifiers of oak.  As well, the earlywood vessels are open and you can blow through them. White oak you cannot, as these vessels are closed up with "tyloses".
Most every wood has a demarcation from one year to the next that can be used to count the growth years.


 

[WmFritz]

Good explanations.

If  I could take it a step further... the variances in the widths in of the rings I assume, are based on things like rainfall that year and maybe sunshine the tree received? Or stress due to draught?

P.s.    BT,  you sure get a very detailed image with your scanner.     

[Piston]

Excellent question MrCaptainBob!  I'm learning a lot from this thread. 


I remember reading in one of my tree books, I believe it was "Reading the Forested Landscape" or something to that effect, that if you count the rings to get the age of the tree, and actually date them, you can figure out a lot of history.  For instance, if there is evidence of old logging in the area, and you notice that 18 growth rings in, all the rings went from really tight spacing, to really wide spacing, then you could most likely derive that the area was logged 18 years ago, and the canopy opened up to allow more sunlight and faster/greater growth from that tree. 

[SwampDonkey]

Excellent question MrCaptainBob!  I'm learning a lot from this thread. 


I remember reading in one of my tree books, I believe it was "Reading the Forested Landscape" or something to that effect, that if you count the rings to get the age of the tree, and actually date them, you can figure out a lot of history.  For instance, if there is evidence of old logging in the area, and you notice that 18 growth rings in, all the rings went from really tight spacing, to really wide spacing, then you could most likely derive that the area was logged 18 years ago, and the canopy opened up to allow more sunlight and faster/greater growth from that tree.

Dendrochronology. Awhile back, a very old red spruce was discovered to be nearly 450 years old and not very big, set a record. The study was looking at changes in climate. I think there is as much art involved there as science, to tell ya the truth. An awfully lot of guesses, inferences and postulation. In that particular tree, many false rings were identified. A false ring will not be entire in circumference, it will run out. That can't be counted as a new year. But often indicates a weather induced second bud break in a year. Remember, climate is just 'average' weather. Give someone some money and they can write all kinds of reports. For some this is their job, to spend public money churning out reports. ;D

[WDH]

Every year, a new set is produced - the old xylem becomes the inner bark, the old phloem becomes the heart wood (which is dead).

Did I get that right, professor?

I am no Professor, but your xylem is the phloem and your phloem is your xylem  .  Xylem is the wood and phloem is the bark.

[thecfarm]

Nothing to judge for size in your picture beenthere,but guessing some rings are an inch wide? Good growth if I'm right.

[beenthere]

 ;)
The thickness of this piece was scanned from a slice of board (an old 1 x 6" fence board that was green cut 1" thick) so the rings are roughly 16 to the inch.

"Xylem up" and "Phloem down" was the saying, if I recall.

[ashes]

WDH has this correct.

Xylem is wood and ultimately heartwood. Phloem is created and pushed outward creating bark.

Early wood is the lighter wood that is produced when the most water is being transported leading to larger vessels or less wood density. Late wood is the wood that is laid down when less water is moving through the xylem. This wood is denser.

[Al_Smith]

A few years ago because of wind damage I was forced to drop the largest oak on my property .A midwestern giant with a 4 foot girth 117 feet tall ,red oak .

I could count 273 rings but I'm sure I missed some .If a person only knew what the weather was like I'm certain it could be verified from those rings .It was all there if a person only knew how to read it .

[Cedar Savage]

Also they look at the pattern of rings, 10 wide, 2 thin, 3 wide, 1 thin, etc. Then you find that same pattern in other trees, or buried logs, or wood from a ship, or buildings. From there you can put an accurate date on how old the wood is.