tree age   Larry Winship
  May 08, 2002 17:42 PDT 
The recent emails about "ancient" trees and clones brings to mind a
favorite question I like to ask students in my Ecology of New England Old
Growth class - "What part of a 300 year old tree is 300 years old?" The
following discussion usually leads to a discussion of the fact that the
living part of a tree, where cells are dividing and expanding, isn't in the
middle, it's on the margins! Like our own faces, the part presented to the
world is pretty young. The old stuff is hidden down pretty deep.

So what actually does tree age really mean? Certainly tree age means that
what we recognize as a single organism (is it?) has persisted in that one
spot for a long time, recording in its rings a record of growth and perhaps
chemical and other (?) signatures of past events. The cellular descendants
of the meristems in the original seedling continue to fix carbon dioxide,
accumulate biomass and grow. Branch structure and bark form change with
age, too, so perhaps those dividing cells aren't doing the same thing their
elders did or they are responding to a different environment. And the soil
under that tree IS truly old, having been more or less undisturbed for as
long as the tree has occupied the air space above.

So what we are impressed by (or at least I am) is not the AGE of the tree
per se, but the timespan of a continuous unbroken record of living - and
dying - of a single plant genotype in one place - I seem to venerate a
process, not a product. Whew. Too much something in dinner tonight.

So I guess we will continue to search for and wrangle over the "oldest"
tree --- which is of course more than just old wood!

Really enjoy your posts.


Re: tree age   Dennis E Hayman
  May 09, 2002 04:48 PDT 
Well said Larry! We know that our human bodies change completely every
couple of years too. Still looks like the same person, but different
material. Yet, the silent observer within, the one who keeps creating it
anew all the time, is always there, unchanged. I suggest that this is
true of all beings. Perhaps some of those same particles that were once
part of those old Trees are now part of us, and vice versa. Perhaps that
cellular memory explains some of our kinship with the great old ones of
the Forest? Seeing Bob do his little dance when he finds one leaves me
with no doubt!