Trees adapt to winter

Middlebury’s trees are far more interesting than you might think. Join the Middlebury Land Trust’s guided hike February 10 to learn from experts about winter tree identification and adaptations. (Janine Sullivan-Wiley photo)

By JANINE SULLIVAN-WILEY

Winter in Connecticut can be hard on everything that lives outdoors. There are many adaptations for animals (fur, burrow, hibernate), birds (some just go south, an adaptation shared by some humans) and plants (die back in winter.) Our native trees also must adapt, but they can’t move. The two biggest winter threats to trees are the cold and lack of liquid water. Trees have found ways to deal with both.

Deciduous trees (trees that lose their leaves in winter) adapt to the lack of liquid water by dropping those tender, moisture-losing leaves, thus protecting the tree from dehydration. Trees also send much of their sap underground, into the soil-protected roots. Their bark serves as an insulating layer that protects the living cells underneath from rapid changes in temperature.

To deal with the cold of winter, the cells of deciduous and conifer trees produce sugars and amino acids that act as antifreeze (a trick shared by some frogs). This is a remarkable process whereby the water is pushed out of the tree’s cell interiors – where it can kill the cell – to outside of the cell wall. Between the cells, that water is not only harmless but in freezing, it produces a bit of heat (fun chemistry fact) that helps the cell even further. Some northern species, like black spruce and trembling aspen, do this so well they can survive temperatures as low as -80 degrees Fahrenheit.

Snow can be an aid to trees as it insulates the ground and protects against wide temperature swings. However, its weight is a challenge. Deciduous trees spare themselves much of the weight by losing their leaves; bare branches don’t hold the snow as well. Conifers deal with snow through their conical shape, flexible branches and needles that shed the snow when it becomes too heavy. One fun fact about those conifer needles is that they are able to continue some photosynthesis through the winter when conditions are right.

Bill Giuditta, a Middlebury Land Trust (MLT) Board member and retired biology teacher with great expertise about trees noted we may just glance at trees and think they’re all the same. “But look closely and you see all the differences: patterns of furrows and colors. A beech tree for example, has bark that is usually smooth and light. Shagbark hickory bark is dark and peeling away in strips. Birch has bark that peels horizontally. A striped maple has bark that may have light vertical stripes or have dark bark,” he said. How those differences happen remains a mystery, despite all of our technology.

His description of how trees are built made my head spin. Trees are composed primarily of cellulose, and cellulose is a carbon compound. And where do trees get all of that carbon? From the air. They combine carbon dioxide from the air with water and sunlight to build their cells. In other words, all of those acres and acres of trees – have essentially been made out of air. In this amazing process, the trees also help combat global warming by binding up carbon dioxide and as a byproduct make oxygen, essential for us to breathe. They really are a “wow!”

You can learn more about trees, how to recognize several of our commonly found species, and how they manage in winter by joining Giuditta and fellow MLT Board member Alice Hallaran on the walk they are leading Saturday, February 10, starting at 10 a.m. at Lake Elise. Preregister at mlt@middleburylandtrust.org.

Contact this writer at jswspotlight@gmail.com. You can visit the Middlebury Land Trust on Facebook or the website at middleburylandtrust.org. Meanwhile, happy hiking!