Fern Glen Essays
Shiver Me Timber
by Judy Sullivan

I must confess to anthropomorphizing much of my environment. When I purchased a new Apple computer, I worried that my old one felt rejected. I vigorously defend my 1988 Toyota wagon against snide remarks regarding the generous freckling of warm russet that overlays its cool silver sheen, maintaining that its character is nothing if not assiduous. Therefore, it should be no surprise that last week's brutal, below zero temperatures prompted a spurt of almost painful empathy for the trees that I've left to shiver in the Fern Glen for the winter.

A quick assessment of our differences is in order. Trees acclimate to plummeting outdoor temperatures, whereas I retreat indoors, preferably to the comforts of an engaging book and a 60 lb. lap dog. Most trees divest themselves of their sartorial splendor prior to the onset of winter. I, on the other hand, significantly increase my girth by the addition of layer upon insulating layer of wool, silk and fat. Nevertheless, there are similarities between us. In winter, the greatest enemies of a tree are the cold and loss of moisture. As a heat-seeking human missile slathered with ineffective anti-wrinkle cream, I battle the same foes. Winter is still with us, ergo I can't declare victory. Yet, I can say that the trees, unlike me, have not retreated. How do they do it?

The first line of defense for most of our woody compatriots is the shedding of extraneous baggage. The broad leaves of oaks, maples and other deciduous denizens of the forest lose water through tiny structures shaped like collagen-inflated lips, called "stomata," much the way we lose water vapor when we exhale. Holding on to the leaves through a dry season would put the trees in a state of dehydration. Boughs would break and trees would fall from the weight of accumulated snow. Recall the October 4, 1987 storm so celebrated by schoolchildren of upstate NY and "Snowbud" in the spring of 1997.

Evergreen trees such as hemlocks and pines don't avail themselves of this option, although they do shed a significant number of needles in the fall. In general, they retain these for two to three years before dropping them. Flexible branches and a steep profile, rather like the roof of a Swiss chalet, help them to shed excess snow. In addition, everyone knows that being in the center of a group waiting for a bus on a windy day is preferable to being on the periphery, or worse, alone. The presence of extra bodies at the bus stop acts as both windbreak and insulation. Much the same can be said for evergreen trees growing in groups and for their layered branches of needle-shaped leaves, which create an insulating layer of air that reduces moisture loss. Nevertheless, a warm sunny day in winter actually causes more moisture loss than a cloudy windy one.

As a liberal application of Oil of Olay protects my skin (at least in wistful theory), a thick waxy coating of cutin reduces the rate of moisture lost by the needles. Their stomata subscribe to the popular World War II cautionary slogan "Loose lips sink ships." and remain tightly closed. In the event that these strategies are insufficient, the needles themselves acclimate at a cellular level.

If you drive to the Adirondacks, or up Mt. Greylock in northwestern Massachusetts, you'll notice the change in the composition of the forest. As you climb, (preferably in an ancient and assiduous Toyota wagon) you'll notice how the beeches, oaks, sugar maples and ashes begin to give way to hemlocks, spruces, balsam firs, and paperbark birches. This reflects their ability, or inability, to cope with the rigors of a boreal habitat.

All trees have a specific temperature at which ice crystals will form within their cells, causing death. Amazingly, this temperature actually varies not only between species of trees, but even between individuals within a species. When daylight hours shorten and available water is in short supply, the trees mobilize their defenses against the oncoming assault of winter. A hormone is produced that limits growth and makes the cell membranes porous, so that water can move outside of the individual cells before freezing. Complex chains of proteins unlink to make smaller units. Concentrations of sugars and fats increase inside the cells. The strategy is to adapt the cells to the environment by lowering the temperature at which they'll freeze. Also known as "change or be dead."

Meanwhile, there's the plumbing problem. We choose not to dwell on the sick feeling that we experience when we turn the kitchen faucet on a frigid night and wait in vain for the usual result. Instead, there is a different sort of outcome. "Outcome" the hair dryers. "Outcome" the heat tapes. Once the pipes are thawed the, hopefully working, water pump again forces any gas bubbles through the pipes.

Although books could, and have, been written on the subject of water movement in trees, the general idea is that trees in winter have plumbing challenges similar to our own. Water moves through tree trunks in pipes (xylem) that are comprised of sections. Water molecules, having a social nature, in essence latch on and follow each other through the pipes like a conga line, albeit with less animation. However, when ice crystals form in the columns, gases are expelled and form little bubbles. This breaks the line and disrupts the flow of water.

Without the need to support leaves during the winter, deciduous trees aren't as concerned about a small plumbing failure. In early spring before the buds open, the pipes in their roots and trunks fill with water and things begin to move again. In late spring, after buds open, the trees create new portions of pipe to serve growing twigs.

Conifers, however, with their evergreen needles, are proactive plumbers. Between each of their pipe sections is a little check valve, of sorts. We've all seen water take up more space when it changes to ice in our freezer trays. This principle is the same in the tree as it is in the Frigidaire. The resulting pressure in a section seals the valve, which can withstand up to 900 pounds per square inch! When the ice thaws and the gas is reabsorbed, the pressure returns to normal, the valve opens up, the little water molecules form another conga line, and away they go. Off to nourish and rehydrate.

I'm both fascinated and annoyed by things not visible to the nearly naked eye. Fascinated by that "Alice In Wonderland" feeling of expanding and shrinking through concentric worlds. Annoyed by the fact that such fascination requires such arduous access. Despite the traditional notion of the correlation between effort and reward, I purport that these are often inversely proportional. After all, look at how easy it is to consume a pound of Godiva chocolate. I know of no pleasures worth frostbite. Still, my annoyance can't defeat my awe.

I'm off to call my cosmetologist to recommend cutin, my doctor to ask about increasing my intake of sugar and fat, and my plumber to see about the possibility of bio-technology in the form of self-regenerating pipes. I'll keep you apprised.

Questions, comments, or other feedback to Judy Sullivan.