Dean M. Chriss
Bristlecone Pines, Sculptures of Time
(Click image to enlarge)
The trees in this photograph have died, perhaps thousands of years ago. This
specie of bristlecone pine, the Pinus longaeva, is among the longest living life
forms on Earth. Some are known to live nearly 5,000 years, having sprouted
before the Egyptian pyramids were built and just as the stone age was ending.
When these trees die they often remain standing on their roots for many
centuries. Fallen trees and dead wood, like that in the foreground, lasts thousands of years longer. That's long enough
for wind blown abrasive materials and weather to erode the surface of
the wood, polishing it into smooth and fantastically sculpted forms. They are
truly sculptures of time.
Although the trees in this photograph are dead, many living trees look nearly the
same. They might have only one small living branch with green needles and
a thin strip of bark on one side bringing moisture and nutrients to it.
Bristlecone pines have the unique ability to survive harsh conditions by
allowing parts of the themselves to die so other parts can survive. The older a
tree gets, and the more adversity it endures, the more of it is dead wood. So far it
seems to be a successful strategy, though climate change and disease is
now taking a toll on these ancient trees. Specifically, White pine blister
rust is a lethal, nonnative disease of white pines that also infects the
ancient bristlecone pines. It was introduced to North America from Asia, via
Europe, in the early 20th century. It was first discovered in Colorado in
1998 and has since slowly spread through the continent. This 20th century
human phenomena will end the story of these millennia old trees in what,
relatively speaking, is the blink of an eye.
Tree rings from both living and dead trees give us a tree ring history that
goes back nearly 10,000 years. By radioactive carbon dating the ring
samples, which have definitely known ages, it was found that the amount of
radioactive carbon in the atmosphere varied over time. That in turn allowed
calibration of the radioactive carbon dating process, making it much more
accurate. All living things absorb radioactive carbon while they are alive
and stop doing so after death. At that point the radioactive carbon decays
at a very exact rate, allowing us to determine how long ago the once living
material died. In order for that process to be precise, the initial amount
of radioactive carbon must be known. We used to think it was constant over
large spans of time, but these trees taught us that it was not.
Because these bristlecone pines do not compete well with other plants and
trees, they are typically found in conditions that are too harsh for most
other plants to survive. High altitudes, poor soils, and little moisture
make the ideal environment for these trees. The trees in this photograph
were found at an altitude of about 11,200 feet (3413 M) in soil composed
mostly of rocks, in an area that receives almost no rain.