Life span of American Beech?

[Jenny]

I've been trying to get some information on the typical life span of an American Beech (Fagus grandifolia). I've read that it is anywhere from 150 - 300 years in more or less ideal conditions. Does this sound right?

Jenny

[Steve Galehouse]

Jenny-

I think 150 would be typical, while 300 would be possible but exceptional.

Steve

[edfrank]

Jenny,

I really don't like the entire concept of the average life span of trees.  The reasoning is a bit convoluted, but not really that complicated.  Say you start out with a tree species sprouting from seeds.  Initially there are thousands of them.  Over the first ten years these thin out and the total numbers of tree seedlings decreases dramatically.  As time passes the trees tend to continue to decrease in number at an ever decreasing rate.  so at what ever age you pick there are trees that are still alive and will continue to grow older, and a much larger majority of trees that did not reach this age.  There is no average age at which the trees reach and then start to die off.  The trees are dying off from the time they sprout and continue to die off ever more slowly as time passes.  They are not like people wit an average life span.  If for example 90% of the seedlings die off in the first twenty years, does that mean the average life span of the trees is less than twenty years?  I don't think so, but that is the kind of figure you would get if you look at the lifespan of trees in the same way as you do people.  You similarly can't say that the average lifespan is some percentage of the maximum known age of the tree, because the last surviving tree may live twice as long, than the second oldest tree.  The tail of the population age plot may trail off for a long and irregular length.  So there really is no good way to define the average age of a tree species. We can guess an average age for say beech, but mostly that is a false impression based upon the logging history of the area.  Because you don't see many beech older than 150 years is related to the fact that the forests were pretty much cut flat in the last 100 to 150 years, so you are seeing a false age distribution.

You could define average age by something like the age at which the percentage of trees older than X is some percentage of the number of trees alive at age Y where Y might be something like 100 years for most species.  Again the numbers would need to be determined by aging large numbers of trees at a site that had not been logged to screen out false distributions.

For your tree guide I would suggest listing the maximum know age for trees that have had a reasonable amount of sampling.  For American Beech the oldest cross-dates specimen is an 204 years old - this number is very misleading because the tree has only been lightly sampled.  An older document by Hough et.. al, reported a ring count age of 366 from the Tionesta River area of Pennsylvania.  Lee Frelich has suggested that the tree may reach 400 years in the Sylvania Wilderness of Michigan.  Those number seem reasonable to me.  There are two places you can look for maximum ages  One is Neil Pedersons' Eastern Old List  http://people.eku.edu/pedersonn/oldlisteast/ which has accurate ages, but with the caveat that many of the species listed have only a limited sampling and likely the max ages listed do not represent a realistic maximum age for the species, and the ENTS Old List http://www.nativetreesociety.org/dendro/ents_maximum_ages.htm  which as a limited selection of maximum ages that have been reported.  The ages here are older and I feel more realistic, but are not cross dated and could contain significant errors.  

In any case I don't think the idea of average life span has any merit unless defined similarly to my suggestions above, and I would not include it in your tree pages.

Ed

[Jenny]

Ed,

This makes a lot of sense to me. I kept thinking of all the ways a tree's life span could be affected that would skew an average one way or another.  I have reworded the entry. I thought it useful to include something about age because it is something that a person would definitely want to know/ask about. I can say something like an American Beech individual "has been known to live as long as ....."  Using those links you provided will help.

Thanks, Jenny

(I've been reading a lot of Haiku lately, so all my sentences want to sound like this:
The beech tree
would prefer not
to reveal its age.)

[edfrank]

Jenny,

You could say something like "The majority of mature beech trees do not grow more than 150 years old, but smaller numbers of indivduals may under the rgiht circumstances may live to be upwards of 400 years old."

This is somewhat better because it states "majority of mature trees" that gives an impression of the age distribution with some boundaries, but isn't very definitive.

Ed

[James Parton]

Jenny,

One thing is for certain, they can get old. I have seen old ones at Pearson's falls at the foot of the escarpment below Saluda NC. Many have that older look and have girths around 10 feet.

Yesterday I measured two in the old-growth forest of Joyce Kilmer. One was over 100 feet and the other barely broke 120. Both trees were just under 10 feet in girth. I also know of a  Beech ( European, I think ) at Grace Episcopal church that has the old gnarly rooted appearance. It probably dates back to when the church was built. About 150 years ago.

James.