I recently took on a project to discern the age of some cedar trees. It use to be a hedge in the 1940's. The center has long since decayed. On the remaining wood, it is difficult to count the rings.

I looked under a microscope.There are distinct lines that are either compression rings from boring the increment or are they actual faint annual rings.

Anyone have this problem.

Reply to post by Andrew Wood-Gaines, on July 14, 2001 at 15:25:01:

Andy, there are a few things you can try.

1. There are various stains that make the rings stand out. Some can be quite tedious as well as dangerous to use. Look in the Forestry Suppliers catalog. If Russ is listening he has some experience with these.

2. The tree ring lab at Lamont Doherty Earth Observatory of Columbia U. tells me they prefer to staining carefully sanding the sample from say 200 grit on out to say 1200 grit! You'd have to securely mount the core too do that.

3. If you can shave a thin enough slice off the core you may see more with backligthing under the microscope.

4. To get rings back to an early age... where the tree center is decayed... you might try an old branch or even a root. But that starts to get destructive.

When I get home I have some dendrochronology links... or you could just do a seach on that.

Reply to post by Andrew Wood-Gaines, on July 14, 2001 at 15:25:01:

I'm listening.

I use several stains depending on the typ0e of wood. Toluidine blue is good for general use, and helps distinguish parenchyma tissue. I bought mine through a local science supply shop.

Another is Phloroglucinol. This is sold by Forestry Suppliers. The problem with this (other than the cost) is that you first bathe the sample in the stain, rinse, then bathe in strong hydrochloric acid (50%). Rather strong stuff, and it creates noxious fumes. I don't recommend this for general use. The result is a red stain that highlights the denser growth between annual rings.

A very simple (and cheap) method for some cases is simply to mix a concentrated batch of Cool-Aid drink mix. Use a small amount of water to get a dark stain, then try it on some samples you can discard. It may provide enough contrast in the cells to see what you need. Be sure to test this on samples similar to the ones you will work with, not your best cores if you need them later.

Whatever you do, start with fine sanding or shaving, as Scott suggests. Finish with at least 400 grit, finer if you can get the paper. Use some sort of suction or vacuum to clear the fine dust in the cells. Do this before any staining you attempt. I sometimes use a surgeon's scalpel or one-sided razor to shave the top side very smooth. Be sure you are working with a cross-section at the top of the core- not the radial side.

Use appropriate magnification for viewing. I find that between 20x and 40x works best, although sometimes less is better. I often use a 25x Macroscope, because it has a measuring reticle in it.

As to the missing rings (internal decay), sampling enough trees locally you might find a few that are not decayed, and can use those for comparison. Using a branch can be difficult, especially with something like cedar that grows slowly on the branches. You also have to estimate the age to get to the height of the branch, so it's not entirely accurate.

HTH
Russ Carlson

Reply to post by Andrew Wood-Gaines, on July 14, 2001 at 15:25:01:


Did you sample only the trunks and are there no other parts of the trees available? If there are and since you are apparently using an increment borer, I might suggest taking additional borings of other limbs--the larger and lower the better.

My thoughts include:

There should be similarities in patterns in all parts since each part of the tree grew during the same conditions. All can be understood to have a serial relationship in that every new branch will record from the point it started and not all will have lost their centers. (The center decays may be attributable to pruning since the trees were maintained as hedges and in that case I might expect all centers to be lost.)

Good fortune may supply some limbs that go back to very close to the beginning of the tree which is now lost in the trunk. This could give you a more accurate estimate since there will be common visual records in both the trunks and the limbs that can be dated. I can't advise you on the next techniques beyond some chemical indicators described earlier by Russ and Scott--at a certain point, your interpretions will be instinctive.

There may also be some old stubs that can be cut back a bit again without too much injury that will give you a full radial perspective in addition to the increment cores. (I'd paint those cuts afterwards.)

My suggestion is to let the trees teach you; if you think you know what you're looking for, you may very well miss it. Consider the various pieces of the same tree in the cumulative and let the back of your head find the patterns. After all, that's what you really want, just patterns that can relate to age. Then mull over the the patterns in the group of trees--thay all were probably planted about the same time--so one tree may help understand another.

If this seems too complicated, I don't know what to say. Finding truth, in tree rings or other things, is often determined by how much time is put in. No shortcuts or abbreviations here.

PS: For slices, Shigo used to insist we make no more than 1 or 2 cuts with each new razor blade. As I remember it, there were at least two yowls per class in spite of our best intentions.

Good Luck,

Bob Wulkowicz