Summer is ending. Bees are busy in the goldenrod filling up on nectar to bring back to the hive, only to turn around and hurry back for more. Bears are in a similar mode, having feasted on a hefty blueberry crop, gleaning the waning blackberries, and getting to work on the apples found along power lines and in old fields. I recently set a game camera at an ancient oak where I filmed a bear rummaging for acorns and settling in for a nap. Fat bears are symbolic of the amazing abundance that we are so fortunate to have all around us.
Let’s face it, insects rule the earth. Their abundance and dominance are all too obvious in the warmth of summer. But what happens to them during the long, cold winter when we rarely see an insect? There are nearly as many answers to that question as there are species of insects, and that is a number we don’t even know. Insects are cold-blooded, their body temperatures varying according to the temperature in the environment. Theoretically, they literally cannot move if it gets too cold. But there are many strategies to keep up some level of activity in winter. Honeybees keep each other warm by gathering in a cluster within the hive. The colder it gets the tighter the cluster. Individual bees rotate from the inside of the cluster to the outside, allowing the coldest bees to move inside the cluster to get warm again. Ants also live in colonies, and some stay warm in clusters too, but most use other strategies. Some species happily move into any available warmth. That could be your house, or under a sunny rock, or the bark on the sunny side of a tree. Some species dig deeper into the soil and some even build themselves special tunnels that retain heat like a sleeping bag. And most ants in cold climates produce a sort of antifreeze that allows them to tolerate temperatures below freezing.
It’s not only animals that must prepare for winter. Plants must endure a long dormancy until they can resume an active lifestyle in the spring. The process of “hardening off” begins in September for many plants, from the grasses to the trees. Hardening is triggered by a combination of shorter day length and lower temperatures. The length of daylight shortens by about an hour and a half throughout September and the average temperature in St. Johnsbury drops from 64 degrees on Sept. 1 to 54 degrees by the end of the month. Many spots in Caledonia County normally see a frost in September, another strong trigger sending plants into dormancy. To harden off, plants need to stop growing, store food for the winter, and prepare their cells for frozen conditions.
During the growing season tree growth is concentrated in the cambium, the layer of living cells just beneath the bark. The cambium becomes a soft and slippery layer that is easily damaged. Even a minor rub on the bark can tear the bark from the cambium, causing an injury. A falling tree scraping along its neighbor as it goes down inflicts a lasting injury as the bark splits and separates. This is why I try to stay out of the woods with any equipment during the growing season from mid-May to mid-August. The damage we do to the trunks of trees is obvious, but the roots are also vulnerable, and skidder and tractor tires easily damage them.
By September a tree’s growth has slowed way down as it enters pre-dormancy. Twigs have stopped elongating and instead are forming the resting buds that will last through the winter and be ready to pop in the spring. A layer of cork is forming at the base of leaf petioles. When the cork completes its work, the leaf will fall, the small wound at its base already sealed off. Chlorophyll production is slowing as the leaves begin to lose their vibrant green. The tree is pulling any nutrients back out of the leaves and storing carbohydrates in the roots.
Several years ago Mike Snyder described tree roots in winter in one of his Woods Whys columns in Northern Woodlands magazine. He explained that tree roots grow intermittently, with a flush of growth in the spring and sometimes another flush in September. Roots become dormant but are light sleepers, ready to grow if soil temperatures warrant it, even while the above-ground parts of the tree are in a deep slumber. It is this quiescence that allows evergreen tree roots to send water up to the needles in winter, and for deciduous trees to expand their root systems to be ready for spring.
Northern tree roots are adapted to snow cover and are damaged when the snow is not there, allowing the soil to freeze a foot or more deep. Recent research at the US Forest Service Hubbard Brook Experiment Station in the White Mountains has demonstrated a 40 percent decline in sugar maple growth in plots with no snow (they actually shovel snow off plots to study this). Another study shows that snow is melting 5-10 ten days earlier in the Northeast Kingdom. What effects will this have?
As you put up food from your garden this month, start your fall wood cutting in the woods, or add insulation to your house, you are mimicking the processes of all living things as winter approaches. Enjoy the abundance and the last true warmth of summer, but make sure you’ve got the chimney clean and hat and gloves at the ready.
Tim McKay is a conservationist, tree farmer, and woodworker in Peacham.