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© copyright 2003 Michael P.
Hamilton, Ph.D.
A walk in Methuselah's garden
September 26, 1996:
The line of sixty or so people gingerly worked their
way in darkness up the old road toward a summit that was just now
coming into view. The stillness of the cold, paper thin atmosphere
at 12,000 feet, combined with the proximity of the violet-rimmed silhouettes
of ancient Bristlecone Pines gave the climb a most surrealistic feeling.
Our goal was even more remarkable, to view the last total lunar eclipse
of 20th century...and of this Millennium.
The eclipse was a fortuitous event, as the gathering
place and date of the annual meeting of the Organization of Biological
Field Stations was determined nearly three years in advance. There
are about two hundred biological field stations in the United States,
and every year the directors get together in the fall for four days
of sharing ideas and failures, and reinforcing our decisions to be
part of perhaps the most obscure group of scientific professions.
This year's meeting was held at the White Mountain Research Station,
located at the 12,250 foot elevation in the arid mountain range that
straddles the border of California and Nevada. Established by the
US Navy to test infrared missile tracking devices during the 1950's,
the station was later purchased by the University of California and
has become a world-class center for many studies including geology,
high altitude physiology, and dendrochronology -- the science of tree
rings.
The oldest trees in the world are the Bristlecone Pines
(Pinus longaeva). This species is limited to subalpine elevations of
the White Mountains, and in several other great basin desert ranges
between eastern California, Nevada and Utah. The most ancient individuals
occur within a few miles of the Research Station. How old are these
oldest trees? Many have been dated using techniques for counting the
annual rings produced by the contrasting colors of fast growing spring
and early summer wood with the slower growing wood of late summer and
fall. Over the life of an individual tree, portions of its trunk may
be damaged or partially die, but other branches continue to grow, laying
down a discernible ring year after year. When the Egyptian culture was
piecing together their great pyramids four thousand years ago, several
of the trees I examined would have already been older than any living
tree in Idyllwild! The Methuselah Tree, the oldest known tree, has more
than 4,700 rings! In contrast, the oldest Ponderosa Pine on record is
a mere 600 years.
The thickness of a tree ring varies from one year to the
next depending upon the years precipitation and the average spring air
temperature. In this way annual environmental conditions are correlated
to the relative size of the concentric tree rings of these slow growing
long-lived trees. Even the logs of long dead Bristlecone Pine decompose
so slowly in the dry cold climate that their rings can be used to extend
the record of the climate thousands of years earlier than the rings
of any living trees. By dating the rings of living and dead Bristlecone
Pines, scientists now have a nearly continuous record of the prehistoric
environment of our southwest region from 10,000 years ago, findings
that are helping to figure out how much our climate varies as a natural
process in contrast to changes artificially induced by atmospheric pollution
and greenhouse gases.
Using an instrument called an increment corer, a thin core sample
from a tree trunk is removed to non-destructively examine
tree rings. By finding overlapping rings from three different
trees and logs, a continuous record of 100 years of growth
is shown in this drawing.
By now the lunar eclipse has reached its peak, and with
my back against the sturdy trunk of a Bristlecone Pine, I'm pondering
the unfathomable time scales and endless cycles of Sun, Earth and
Moon...and of a life force that has allowed the trees in Methuselah's
garden to survive for a thousand lunar eclipses...and perhaps a thousand
more.
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