The Lilliputian World
of Lichens

The following article was printed in the Fall 2005 Wolf Ridge Almanac.

Lichens are all around us. Take a look! They grow on trees, rocks, and soil. Of the approximately 13,500 species worldwide, more than 3,600 have been identified in North America. There are perhaps 500-600 species in northern Minnesota.

Regardless of your activity, you will likely encounter lichens. Cross-country skiing through a black spruce swamp cloaked in Beard Lichen (Usnea sp); scrambling along the shoreline of Lake Superior painted with Elegant Sunburst Lichen (Xanthoria sp); canoeing an historic Voyageur route alongside boulders draped with Rock Tripe (Umbilicaria sp); drilling past grey and green Sheild Lichens (Parmelia sp) while tapping sugar maples; or stepping softly among the crunchy Reindeer Lichens (Cladina sp) while picking blueberries.

Regardless of the season, lichens thrive. When the last fall flowers have faded away, lichens remain. As flocks of birds migrate south, lichens remain. While winter snows blanket our landscape, lichens on trees and cliffs remain visible. And, when the warm spring and summer sun provides energy for an explosion of life, those same lichens remain.

Lichens are a composite organism of three kingdoms: Fungi, Protista (algae), and Monera (cyanobacteria). The relationship is a partnership, or symbiosis, which includes a fungi in association with another organism from one of the other kingdoms. This symbiosis benefits the fungal partner most. You might consider that a lichen “is a fungi that has discovered agriculture.” Taxonomically, they are included in Fungi and nearly all lichens are members of the Ascomycetes which includes such other organisms as cup fungi, lobster fungus, and morels.

Unlike flowering plants, lichens do not produce seeds for reproduction. Instead they reproduce by spores produced by the fungal partner. Because the likelihood is small that a spore of the lichen fungus will land next to the correct algae or cyanobacteria on the right surface, reproduction by fragmentation is quite common. A broken bit of lichen lands on a proper substrate and begins to grow.

Lichens receive almost all their needs from precipitation and the air. For the most part, they receive nothing from their substrate except a place to live. They will grow on almost anything including the ground, rocks, trees, steel cans, bits of cloth, abandoned cars, and even old shoes. They absorb moisture from rain, dew, and the atmosphere. Even when the humidity is as low as 60%, some species of lichens are able to gain enough moisture to grow. They can grow in all seasons provided that the temperature and moisture are acceptable to the particular species.

Because lichens are highly efficient collectors of airborn substances, they fill the role of recycling airborn chemicals into the soil. Unfortunately, they can also direct heavy metals and radiation into the food chain. During the 1940’s, atmospheric testing of atomic bombs introduced into the air massive amounts of radioactive nucleotides. Reindeer lichens were efficient accumulators of these substances. As a result, caribou ingesting the lichens concentrated radiocative materials in their bones and tissues. Indigenous people who relied on the caribou as a foodsource then had an increased likelihood of bone cancer and leukemia. The Chernobyl nuclear plant meltdown in Ukraine in the 1980s produced a similar effect.

In several places around the world, lichens are being used as bio-indicators of air quality. They serve as inexpensive filtering systems to monitor the spread of dirty air from factories, power plants, and urban areas. In one instance in Ireland, school children were organized as citizen scientists collecting data regarding air quality around their homes. They simply identified those lichens living around them and plotted the information on a map. Lichen diversity was low in some areas and higher in others. The resulting maps provided compelling evidence of poor air quality closer to power plants and better air quality further from the center of urbanization. The maps even provided evidence of prevailing winds and the spread of dirty air.

Many animals utilize lichens at some point in their lives. Ruby-throated Hummingbirds and Northern Parula Warblers use lichens for nesting materials. Spruce Grouse, moose, white-tailed deer, and flying squirrels dine on lichens as a winter food supplement. As pioneers in a young landscape, lichens degrade rock surfaces and prepare areas for mosses, grasses, and trees that follow. Species with cyanobacteria (which can fix nitrogen gas into biologically useable compounds) can make major contributions to soil fertility.

Most of us have a minor awareness of lichens around us. Few resources exist for the common person to begin a study of their local lichen flora. Those that do exist, require a complex series of chemical tests in order to arrive at a reliable identification. Although this is an unavoidable fact, there are many groups and species that can be reliably identified using such characteristics as growth form, substrate, and color.

For identification purposes, there exist between three and seven categories of growth forms. The three most commonly referenced growth forms are crustose, foliose, and fruiticose. Crustose lichens look as though they were spray painted on their substrate. Foliose lichens are leaflike in appearance. Fruiticose lichens are bushy and attached at the base.

Positive identification of lichens to species can only be accomplished with the aid of microchemical tests. As early as the 1860s, color tests were being used and are still used today. As an adaptation for life in marginal habitats, lichens produce unique biochemical compounds that serve to control light exposure, repel herbivores, kill attacking microbes, and discourage competition from other plants. Identification of these compounds aids in identification of the lichen. Lichenologists have several tests, among them are the C test, K test, and P test. Calcium hypochlorite (C test) can be replaced by ordinary bleach. Potassium hydrochloride (K test) can be replaced by Liquid Plumber drain cleaner. Steiner’s solution (P test) is difficult to purchase and must be used carefully to avoid contact with skin.

Lichens are perhaps the most overlooked "obvious" organism around. In some areas lichens are so thick that they are considered the dominant vegetation. Recently, I was teaching a group of Minnesota naturalists about lichens. We were identifying several of the varied species on the bark of a sugar maple, when one of them had an interesting question, "So what does the bark look like?"

Once you've opened your eyes to the lilliputian world of lichens, you'll have a hard time seeing past them.

By Joe Walewski, Wolf Ridge Naturalist and Director of Naturalist Training

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