Winter is nearly upon us, and there is lots of work to be done. Today my family spent the day cutting, splitting, and storing firewood to keep the house warm through the coming cold. Plants and animals in the northern hemisphere are getting ready for winter too. None match the wood splitting ability of my husband, but each excels in winter preparation in its own way.
Deciduous trees, like oak and maple, prepare differently than do their evergreen brethren. Winter to a tree is not so much a time of cold as it is a time of drought. Water frozen in the soil becomes unavailable to the plant for use in photosynthesis. Using the diminishing sunlight as a clue, these trees grow a corky barrier where the leaf meets the twig, severing the leaf from the plant. If leaves stayed attached, water could escape through the leaves, into the dry winter air, desiccating and killing the plant.
Have you noticed that some deciduous trees cut off the leaves' water supply, but women's coats allow the leaves to hang on for the winter? Leaves of young beech and oak trees do this. We are not sure why, but it could be that old, dead, dried leaves, which are not so palatable to deer and moose, stay on to cover and protect the delicious bud underneath from these big browsers. Others theorize that these trees just haven't gotten the hang of true deciduousness yet.
Throughout winter our snowy landscape will be dotted with the greens of hemlock, pine, and rhododendron. Evergreens hang onto their leaves to save energy in the spring. Without having to re-grow lost leaves when the soil water thaws, they are ready to get going right away. They may also photosynthesize in the winter if conditions permit. This strategy makes sense too.
To protect themselves, evergreen trees and bushes have modified their leaves. Hemlocks, pines and others have needles with waxy coatings and small surface areas to reduce water loss. Rhododendrons also cover their leaves with wax. Notice a rhododendron on a particularly cold winter day. The leaf will curl under to protect the pores (called stomata) on their bottom surface from the drying effects of cold air. Stomata are the doors, if you will, to the moist leaf interior.
Plants are not the only organisms to adapt to the coming cold. White-tailed deer shed their red-brown summer coat for a dull grey winter coat. The thin summer hair protects well from bugs, but the hollow winter hair traps air and provides extra insulation. It insulates so well that a bedded deer could be covered by snow and not cause the snow to melt at all.
Hares and weasels loose their brown summer coloration and change to a white coat to better blend into the winter background. Some species of weasels maintain a small black tuft at the tip of their tails to confuse would-be predators. If the predator chooses poorly, it ends up with a mouthful of hair and not the weasel.
Some animals stay active all winter searching for food, while others stockpile supplies. Grey squirrels stash large piles of acorns and red squirrels stockpile evergreen cones. Throughout the winter they will brave a trip from the protection of their nests out to visit these stores to keep their fat levels up. Chipmunks have spent the fall storing nuts and seeds in underground coffers. They will wake up periodically, make an underground trip through its maze of tunnels, and have a bite to eat.
Throughout winter, fat is an important source of calories and insulation for hibernating mammals. A Black bear's fall quest is to fatten up as much as possible. An individual may gain as much as 3 to 5 pounds of fat per day just on acorns in the fall. Those sunflower seeds in your bird feeder are a high fat food source and quickly become a favorite of bears during their fall quest. Woodchucks likewise, gorge themselves on plants, seeds and roots in the fall until they are waddling bundles of fat, ready to curl up underground and hibernate for months on end.
People are not so different. You too are participating in this annual winter-preparation ritual when you stockpile firewood, dig out the scarves and mittens, purchase extra hot chocolate or freeze the garden bounty. Winter...bring it on!
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