laboratory tree ring counts   Neil
  Dec 13, 2003 07:22 PST 

  What can go wrong with laboratory counts?

There are several things that could go wrong. Most of the problems come in the preparation phase.

1 - Probably the most important things to do is to mount the core correctly. You want to mount it so the cells are vertical, like they were when they were in the tree [though a core mounted upside down from its original position in the tree would work, too]. When a core is mounted on its side [horizontal], it is difficult to see the terminal parenchyma. The terminal parenchyma is the last line of cells in the annual ring and signifies the end of a true ring.

2 - Sanding - it is a difficult lesson to learn, but you can never sand a core too much so long as you move to progressively finer grits. The rings become more distinct moving from 120 to 220 to 320 grit. However, depending on the species as well as the condition of your sandpaper, sanding up to 320 grit might not cut it. To be able to discern whether the ring you see is a true ring or false ring, you need to be able to see the terminal parenchyma. You need a well-surfaced and very clean core to best study the annual ring.

It took me a while to learn that sanding and as I train new people, this is the one aspect of tree-ring analysis that we come back to most often. Almost ever year someone new comes onto the tree-ring forum and says they can't see the rings in either birch or beech. They want to use stains to bring out the rings. The common reply from the veterans is that sanding will do the trick. It could also be that the cores are not correctly mounted, too.

Different species have different issues. #1 and 2 are important for all species, but even more so for diffuse porous species. Birch, Nyssa [tupelo or gum], sycamore, maple, tulippoplar, magnolia, Nothofagus [southern hemisphere beech] and sweetgum are the most difficult species I've worked with because of their ring structure. I hear beech is tough, too.

Baldcypress and pond cypress, especially in the deep south, are notorious for their false rings. Dave Stahle and his crew should be congratulated for first breaking that code. It nearly borders on heroic. I believe no one successfully crossdated pond cypress until the early 1990s.

Larson, in his excellent text the Vascular Cambium, has this unbelievable picture of some rings from a slash pine in south Florida. It shows a ridiculous number of rings "fade" into one ring. The number that sticks into my mind is 13 latewoods blending into one. Rings merge into each other due to the growth form of the stem or where seasonality is muted. I saw this often with longleaf pine in south GA. I've seen some nasty looking longleaf pine from south Florida - brutal!

I've not worked with hemlock yet, but some problems with it and others species like larch, is that the core can break into tiny pieces when coming out of the tree. Putting the pieces back together, in the correct direction and in the right order is another laboratory problem. Not getting the order and direction correct can alter the cores final age.

A problem I've had with oaks is keeping track of the rings as I cross a ray. The rings on either side of a ray can be shifted. Sometimes the shift is only 1/2 of the width of the latewood. Occasionally the shift can be 1-2 rings. It can drive one crazy sometimes when trying to crossdate.

Suppression: highly suppressed trees form very narrow rings. Sometimes this causes partial ring. Like the slash pine example above, one ring can fade into the prior year's ring moving across the core or just show its "face" on one edge of the core. I've seen partial rings that are only one or two cells wide. They are easy to miss. Highly suppressed oaks make me queasy. We've seen a few oak trees that have averaged 1 inch of radial growth over 100 years. Pulling out distinct rings when the early wood vessels are stacked upon each other or when the rings look like a pile of worms is next to impossible.

Finally, problems are caused by missing or locally absent rings. Pitch pine in the northeast or in a frequently burned forest [Pine Barrens] drops a good number of rings.

Without crossdating, all of these issues may only add up to an error of1 to a few years per century [larger errors might occur more often with pitch pine, baldcypress, hemlock, suppressed anything]. For rough age structures, this error is likely acceptable. For people doing some kind of climatic analysis, this is not acceptable.

However, last year I had a spruce [black or red, I'm not sure yet - likely red] that had 17 missing rings between the mid-1960s and early 1990s [during the red spruce decline]. That induces an error of nearly 2 decades. Several other spruce trees in that population had several missing rings. I have a couple of other spruce collections sitting on shelves that likely have a similar issue, so I don’t think the missing ring problem is specific to the first population. I've heard stories of other individual trees being off by nearly that much [if anyone is sampling at the boreal treeline or on an extremely dry site in the American SW, missing rings are frequent, sometimes too frequent to accurately crossdate].

So, the main problems in the lab are: putting the core in the proper order, mounting it vertically and preparing a clean surface. They all contribute to the difficulty of seeing true rings from false rings. These difficulties put larger errors on ring counts

Hope this helps,


Re: 10,000 year old tree?????????? (that's 10 question marks)   Neil
  Dec 12, 2003 06:24 PST 

Dear ENTS,

10,000 years for Huon pine seems highly doubtful.

Ed Cook has been studying this species for more than a decade and has a
nice collection of living and relict huon pine. The current chronology, using living
and relict wood, goes back neary 4000 year continuously.

He has several floating chronologies that go back to nearly the beginning of the
Holocene and other that are floating earlier in time. Floating chronologies are time
series of tree growth that do not overlap with a crossdated time series. Floating
chronologies are only dated with radiocarbon methods. As such, they have no exact
calendar dates assigned to each year's growth ring. For example, a floating
chronology can not say that there was a frost event in the year 8663 B.C.

But, I've digressed. Ed has hundreds of samples of living and relict pieces of
huon pine scattered through at least the last 15,000 years and perhaps farther
back. The oldest piece I've seen at our open house has more than 2000 rings on it.
I'm not sure of the age of the oldest known huon pine. If there was one documented
anywhere close to 10,000 years, it would be well known.

The oldest known tree is a crossdated bristlecone pine that was 4844 years old.

Here is the tree-ring data base of the old known trees for many species:

This list is far from complete.

Hope this helps,
Huon Pine
  Dec 12, 2003 11:00 PST 

The 10,000 number refers to the age of a clone. In a remote part of the Huon Pine's range (which is mostly riparian) there is a high-elevation male clone all by itself. This clone has been guestimated at 10K. The oldest recorded age for a single stem is slightly over 2,500. It is touted as the world's best boat-building wood and I must admit I have not worked with a finer wood. All living trees are protected, although logs are occiasionaly harvested through a very hard to get permit process. Logs that have been on the ground for centuries are still completely sound.

Once again, conifers rule!