Winter walks in northern forests yield quiet thoughts. During the summer I find my mind racing from one subject to another. My mind is on overload; dozens if not scores of plants to investigate, so much wildlife sign, and so many secrets locked up in all of the geologic features around me that I cannot get my mind to a quiet place. Now, when all of this forested world is frozen and much of it covered with snow (and even my physical pace is reduced by the snow shoes I wear), I find that the solitude of these winter woods suits me. I see an ecosystem free of clutter and for some unknown reason it puts my mind at ease.
I stand here on top of the snow and I can see between the trees for long distances. Sounds, far away, float through forests without summer vegetation. The air smells fresh and I can feel the cold north wind on the exposed skin on my bearded face. There is nothing too complicated about that.
Winter is also a time when I notice some of the most invisible parts of the forest. The part of the forest that is so common, so much a part of the whole system, that I seldom focus on it. I lean against a large red oak in attempt to rest an arthritic knee. The bark on this furrowed tree is mottled with lichen; a wonderful example of something of which I am aware but spend little time thinking about. This particular lichen is vaguely foliose, meaning leaf-like, and is a gray-green color that never found its way into a Crayola color chart. This eastern side of the tree is covered with lichen; so much that it appears to change the very texture of the bark.
Lichens are a composite organism comprised of fungi and a photosynthetic partner such as green algae of cyanbacterium. This symbiotic relationship defines an important part of forest life that frequently goes completely unnoticed. Typically the fungus surrounds and penetrates the algal cell wall. Lichens are tolerant of very dry conditions. During periods of dehydration this complex life form creates a nutrient rich leachate that both the fungus and algae can use to survive. Both members of this alliance utilize dust in the air and rain water for sustenance. The fungal element in this relationship protects the algae by retaining water; the algae uses photosynthesis to reduce carbon dioxide to carbon sugars-valuable food for both members of this cooperative.
Lichen have a unique niche in the forest. They occupy a space that generally goes unused by other organisms. They are found on bark and rocky outcrops that do not have soil. Their ability to intercept and create resources out of almost nothing is truly unique in the forested landscape; bark, stone, and barren earth become fertile for this organism that knows few boundaries. Even the reproduction of the mutually dependent fungi and algae are adaptations to this lean environment. Lichen of different species produce over 500 chemicals that control light exposure, repel herbivores, attach invading microbes, and control the environment to reduce competition from plants. Trevor Goward, a lichen expert, mused that “Lichen are fungi that have discovered agriculture.”
A boulder in front of me has soldier moss resting on top of the rock. This “moss” is actually a lichen that chemically alters the composites of the rock, in effect, weathering the minerals to create loose pockets of dirt on which more lichen can grow. This slow process is difficult to appreciate, but suffice it to say that a large soldier moss colony represents the processes set forth by this mutualistic organism that can often be measured in hundreds of years.
Far to the north, where tundra dominates the world and lichen is a primary form of life, caribou have adapted to foraging on particular lichen species as do mountain goats in the higher elevations of Alaska. More locally, northern flying squirrels gather foliose lichen to line their nests creating soft bedding for offspring.
As I survey the trees in the foreground I realize that nearly all of them have significant lichen coverage on the side that faces the rising sun. This lichen cover is so dominant that it makes the trees blend together. Each tree has a trunk that that is a unique color, but the gray-green lichen that is found on the many different tree species blends all of these different citizens of the forest together; true camouflage in a world of plants.
The blending of the landscape, aided by the lichen covered bark, creates a three dimensional montage in the winter woods; snow, trees, lichen. Each layer has its own dimension, its own depth, and yet each tier cannot be visually separated. Put simply, a vision of complete harmony. I picture the instruments of an orchestra without the musicians or conductor.
The symphony will start when snows melt, the ground unfreezes, and Spring peaks her sweet head up from under the melting snow.
Written for www.wildramblings.com in January of 2010.