By Lawrence J. Winship
Gazette Contributing Writer
.Saturday, January 8, 2011
Even in our modern, instant-messaging, planned-obsolescence culture, something about really old trees still captures our imagination. If that tree could talk, we wonder, what might it tell us?
When we imagine a tree of great age we usually picture a stately, spreading oak, sugar maple or sycamore - but if we read stumps and tree rings they reveal a different image. Old trees are often the smaller, more gnarled specimens, challenged by time and storms, yet still intact. Those of us who seek out old-growth forests learn to look for "broccoli tops" - trees with clusters of very thick upper branches, trees that have ceased to put on height growth and are now, like so many of us older humans, growing out instead!
Great age for trees is a matter of geometry and luck, and rapid growth may not always be the best approach for individual survival. The tallest trees face the stiffest wind. As trees get bigger the proportion of light-gathering leaves to non-photosynthetic tissue - like roots and bark - gets smaller and smaller. Eventually there is precious little net carbon left each year for making new xylem, the water-conducting tissue. A tree out in the open shades itself, so each branch vies with others for essential sun. In the same way, a tree in a forest can be overtopped and lose the battle to a taller neighbor. Some trees solve the puzzle by waiting out bad times, adding very little wood to their trunk and branches, until water and warmth and sun return. Or they may wait for bad fortune to claim a nearby competitor before investing much energy in growth.
(continued http://www.gazettenet.com/2011/01/08/earth-matters )