Mosses and lichens

Cladonia lichen and Polytrichum piliferum, Bristly Haircap moss  Photo courtesy Sonia Allen

If it can be said that mosses are the carpet and upholstery of nature, then perhaps we can extend the metaphor to say that lichens are nature’s paint, wallpaper, fringe and frills.  Dr. Trevor Goward, a lichenologist at the University of British Columbia, goes further to describe lichens as fungal greenhouses, algal farmsteads, ecosystems, organisms, and emergent property.

Peltigera aphthosa

Lichens, of which there are more than 13,000 species (3,600 in the US and Canada), are found in every climate but can grow at much higher altitudes and under harsher conditions than mosses. According to Dr. Irwin Brodo, author of Lichens of North America, “Lichens grow in the leftover spots of the natural world that are too harsh or limited for most other organisms. They are pioneers on bare rock, desert sand, cleared soil , dead wood, animal bones, rusty metal, and living bark. Able to shut down metabolically during periods of unfavorable conditions, they can survive extremes of heat, cold, and drought.” Like mosses, which respond to stressful conditions by going dormant (also recall poikilohydry!), lichens are highly adapted to survival.

Caloplaca ignea

Symbiotic in more ways than one
The world of lichens offers wonderfully technical mouthfuls of terms such as squamulose, crustose, foliose and fruticose, which describe growth forms that the novice observer might simply call scaly, crusty, leafy or shrubby. Whether a frilly-edged fan adorning a log, or a powdery etching coating the face of a rock, lichens are a beautifully symbiotic coupling, or composite, of fungus and a photosynthetic partner — either algae or cyanobacteria. The fungus contributes carbon to the relationship and the photobiont contributes moisture.

In her 1907 book, Mosses and Lichens, Nina L. Marshall describes part of the relationship between these companion plants. Of lichens she notes initially, “...these little plants...lie upon the rocks, secrete an acid which dissolves the hard minerals...They have the power to condense moisture from the air...for they must have water as...food and as a medium by which mineral-salts dissolved from the rocks may enter the interior of the plant and may pass from cell to cell to those parts where they are to be worked up into plant food.”

Cladonia cristatella

Human use of lichens
Like mosses, lichens are used by birds to line or form their nests. Humans, too, have found myriad ways — some traditional, some modern — to use lichen: food and feed, brewing, medicine, dye, perfume, cosmetics, herbal tinctures, antibiotics, salves, deodorant, poison, decoration, fiber and tanning (hides).  Thanks to Sylvia Sharnoff, a list of uses is compiled on lichen.com.

Teloschistes exilis

Lichens as bioindicators

Lichens and mosses are sponges and can take in particulates and pollution, just as they do moisture and other nutrients.  Lichens are particularly vulnerable to air pollution, and are often used as bioindicators of increasing levels of pollution.  “When lichens disappear, they give early warning of harmful conditions,”  according to Dr. Brodo.  He explains that “the association between high diversity of lichens and pristine habitats is so clear that scientists use lichens as indicators of ecosystem continuity — to help them identify areas that should be protected.”

Ulongissimalg

Also, lichens, mosses, and cyanobacteria together form a microbiotic crust, which stabilizes soil and is a major source of nitrogen in certain ecosystems, all of which are threatened by overgrazing and development. Tread lightly!

To learn more and see gorgeous photos of lichens (and some mosses...), visit:

• Ways of Enlichenment
• Lichens of North America
• Mosses and Lichens (Google Book)

All images courtesy Sylvia and Stephen Sharnoff unless indicated otherwise.