Monday, July 30, 2012

but there s life in the old dame yet

There is an awesome beauty in old age, in the broken and twisted forms that record a long tough time on earth, and in the life that goes on in spite of it all.
Great Basin bristlecone pine, Pinus longaeva; White Mountains, California.  
This tree started its life around four thousand years ago, when fortuitous circumstances allowed a tiny seed to germinate and become established amid calcareous rock fragments, little moisture, and scant nutrient-poor soil.

Young bristlecones on harsh sites grow slowly, adding an inch or less of girth each century.  After five hundred years, the tree would have been in the prime of life, like the one to the left, sporting abundant green branches and fertile cones, and growing with the graceful symmetry of youth.

But of course youth doesn't last.  Over the next several thousand years, the trials of life left their mark.  The top of the tree was broken off, and a side branch took over.  Then the replacement crown itself was lost and replaced, creating a wooden pitchfork. Youthful symmetry was gone.
Great Basin bristlecone pines, with distinctive pitchfork growth forms.
Roots were exposed and killed by erosion, forcing parts of the tree to give up the ghost -- no more bark, no more needles, no more cones.  Eventually there were only a couple of narrow winding strips of bark left to carry nutrients and water from the soil skyward, and to transport photosynthesized sugars from the remaining needles.  By the time Edmund Schulman arrived in the White Mountains sixty years ago, this tree was pretty much as it is today -- mostly dead.
This bristlecone is down to two strips of bark, one on each side of the tree.
Edmund Schulman called them "life lines".
It was Schulman who discovered the longevity of bristlecones in the White Mountains.  In 1958, he reported there were 17 over the age of 4000, and the eldest, the Methuselah, was dated at 4600 years.  This set off a flurry of research that continues today.  The long-lived bristlecones have provided records of times and climates past, and insight into tree growth, reproduction and adaption to harsh environments.  Perhaps the biggest attraction is their promise of the Secret of Long Life, for even though these trees are ancient, they still enjoy the vigor of youth.
there s a dance in the old dame yet
toujours gai toujours gai

Like Mehitabel the old alley cat, down to just a single life, the ancient bristlecones still live it up.  If you follow a winding narrow bark strip skyward to the remaining green branches, you will find not only needles but cones as well -- healthy cones with abundant pollen and viable seed, produced at rates suggestive of the heady days of youth.  Yes, there’s life in the old dame yet!
Cone of a bristlecone, 3" long; note the eponymous bristles.
Even more impressive -- the oldest trees are the stunted ones on the harshest sites, growing just enough each year to keep a slender strip of bark or two alive, and to produce seed, which with luck the wind will carry to some equally inhospitable site.
Great Basin bristlecone seems able to thrive on very little.
What's the bristlecone’s secret to a long life?  The harsh environment in which it lives is part of the answer.  A bristlecone pine can grow quite well on more hospitable sites, but would be out-competed by other plants.  There is little competition on dry rocky nutrient-poor soils at 10,000 feet elevation.  The cold dry climate provides other benefits.  Microbial growth is slow, and agents of rot and decay that plague trees elsewhere pose few threats to most bristlecones.  Because plants are scarce and grow slowly, there is little litter on the ground to carry fire between the widely-spaced trees.

But there must be something about the bristlecones themselves that allows them to survive for many centuries where few other plants can grow.  They have quite a few tricks up their sleeve, actually.  Here are some of them.

Bristlecone needles stay on the tree 30 to 40 years!  New ones are added each growing season, but if there’s a particularly bad year when needle growth isn’t possible, older ones supply carbohydrates 'til things get better.

Bristlecone wood is dense and resinous, and highly resistant to rot, especially in a cold dry climate.  But it is not entirely immune.  The wonderful colors of dead wood are due in part to invading wood fungi, and chemical interaction between fungi and resin.

Even a fallen tree takes a very long time to decay.  In the meantime, the wood is sculpted and polished by wind, water and ice.

A bristlecone pine is composed of sectors.  If the roots of a sector are destroyed, only the tissue of that sector dies.  The rest of the tree lives on.

Left: sectored architecture and dieback.

Finally, bristlecones don’t senesce.  The small portion of an ancient tree that is still alive continues to grow with youthful vigor, producing healthy bark, needles and cones.  Even its DNA shows no sign of deterioration.  The seeds are viable, with no increase in mutation rate.  Shortening of chromosomes, seen with aging in so many organisms, doesn’t happen in bristlecones.  Can we really call these trees "old"?
This ancient tree may be mostly dead, but what remains is still young!
there s a dance or two
before i m through
you get me pet
there s a dance or two
in the old dame yet

Notes and Information Sources

toujours gai -- Fr.; always gay, happy, light-hearted

mehitabel the alley cat and her cockroach friend archy were reincarnated by don marquis in 1916, illustrations by george herriman

Discovery of the ancient bristlecones:
Schulman, Edmund.  1958.  Bristlecone pine, oldest known living thing.  National Geographic 113:354-372.

I am grateful to Ronald Lanner for sharing the details of bristlecone life, and for wonderful reading during my evenings in the White Mountains.  His Bristlecone Book is highly-recommended:
Lanner, Ronald M.  2007.  The bristlecone book; a natural history of the world’s oldest trees.  Missoula, MT:  Mountain Press Publishing Co.

The Ancient Bristlecone Pine Forest, in the White Mountains of California, is managed by Inyo National Forest and the Eastern Sierra Interpretive Association.

I wrote about the Great Basin bristlecone and other members of the Foxtail Pine group in an earlier post, Ancient Plants on Ancient Rocks.

1 comment:

  1. I found this really fascinating, knowing nothing about the bristlecone pine- lovely photos too...thanks for visiting my blog and for your kind comment.