Trees closing down for winter, with winterberries. Photo courtesy of Dana Wilde

The older you get, the more the cold takes the starch out of you. Every winter you have to work a little harder to get your mind right to survive. Not only do you have to break out the sweaters and boots, but you have to revise your whole way of thinking about the back steps, the car windshield, and how quickly you can get your bones to cooperate with climbing out of bed.

You even have to adjust your attitude to the scenery. In summer the birch, maple and ash trees are full-looking and green, the chickadees vanish in the leaves, and you get used to a feeling of abundance. But in winter, the trees look like skeletons, the nuthatches walk around weirdly upside down on the gray trunks, and you’re face to face with the fact that the world has given up the ghost. Even sounds die in the snow.

The deciduous trees like oak, maple and beech — the ones whose leaves fall off — have ceased gathering light for food and are as good as dead. Since the leaves are gone, no light is being absorbed by chlorophyll to provide energy for turning carbon dioxide and water into oxygen and carbohydrates. The sap has receded to the roots in the underworld, and the bark, trunk and branches seem lifeless. They’re said to be dormant, which literally means “sleeping” from French, and biologically means having suspended operations.

But even during the deepest sleep in nature, things are happening. The pines, spruces and hemlocks — the evergreens — still slowly photosynthesize food through their needles. And the deciduous trees look frozen, but aren’t. They protect themselves from the cold through a process called “supercooling.” In the fall, as the leaves begin to senesce, or grow old, the sugars the tree produces go unused and instead are stored. When winter descends, the sugars act like antifreeze and can prevent ice crystals from forming in temperatures as low minus 40.

North of us where it gets colder still, an invisible system called “intracellular dehydration” kicks in for some trees. Water freezes, not inside the living cells, but in the spaces between them; in the process, moisture is sucked from the cells, which, being dry, can’t freeze, and so the living tissue remains intact even in the dead of winter.

By about mid-March, when sunlight increases and the days get warmer, the sap returns from underground. The buds, which are prepared before winter comes, start to generate new leaves for collecting light and producing carbohydrates again.

The amazing thing about this cycle is its inevitability. It never fails. The maple by my driveway seems lifeless from December on, but then in March its buds redden and it lives again.

There’s no way to know how, or if, trees concern themselves with all this, although recent research suggest plants have some kind of sentience — altogether unlike ours, no doubt. Or maybe, not completely unlike. They seem to have a disposition in their bones, as it were, to cooperate with winter. They seem to gain from it. You’d swear that maple loves its appointed times.

 

Dana Wilde lives in Troy. You can contact him at [email protected]. His recent book is “Summer to Fall: Notes and Numina from the Maine Woods,” available from North Country Press. Backyard Naturalist appears the second and fourth Thursdays each month.


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