Lichens live on the edge. They are not really plants, and they are not really fungi. They live hanging from the branches of trees or crusting along rocks.
Yet they represent teamwork, both within the lichens themselves and in their contribution to the surrounding ecosystem.
Lichens are an example of symbiosis, when two organisms come together to create a whole greater than the sum of the parts. The first organism is a fungus, and its contribution to the partnership is forming a structure. The second organism is an alga or cyanobacterium. Algae are simple plants without stems. Cyanobacteria, sometimes called blue-green algae, can produce food from sunlight. Some lichens contain both algae and cyanobacteria. The fungus is the building, and the alga is the garden.
The lichen lives by collecting rainfall and other moisture from the atmosphere. The lichen takes in carbon dioxide, minerals, and water.
Lichens living in coastal oak forests are able to collect ocean bubbles. Small bits of spray leap off of the ocean into the air. These bubbles contain salt and organic material. As the bubbles float through the lacy net of oak tree lichens, the lichens absorb them.
Just by the way a lichen lives, it contributes benefits to the ecosystem it inhabits. A study described here proves that California Spanish moss lichens enrich the soil underneath the trees where they live. Scientists placed buckets under oak trees festooned with lichens and under oak trees devoid of lichens. The lichened tree buckets collected dark and rich water full of nitrogen necessary for the tree. The plain tree buckets collected almost clear water.
Lichens provide food for rabbits and deer. Rabbits eat lichen pieces that have fallen to the ground. Deer graze round and round the oak trees so much that lichens grow only above where deer can reach.
Orioles and hummingbirds use soft lichen pieces to build their nests. In return the birds help to spread lichens from tree to tree.
The shapes of lichens remind me of fairy tales. There are three main types of lichen shapes. The first type, fruticose, reminds me of the beard of a troll. These lichens hang down off trees or even sometimes stand upright like shrubs. The second type, foliose, reminds me of an odd flower garden. These lichens look like colored and crinkled leaves. The third type, crustose, reminds me of jewels embedded in rock. Crustose lichens spread across rocks or other surfaces in a rough, bubbly pattern. They become one with the surface and cannot be removed without being broken.
The colors of lichens remind me of fall leaves. Lichens can be red, green, orange, grayish blue, golden yellow, brown, or even black. Lichens get their color from two sources: the color of the algae or cyanobacteria that live within them and the color of acids that the lichens produce. Green algae give the lichen a green or yellow green color. Cyanobacteria give the lichen a bluish gray color. The acid produced by lichens adds even more color.
Color may even be related to habitat. One hypothesis is that lichens in harsh desert environments are more colorful because they need to be to protect themselves against the strong rays of the sun. Deep reds and oranges of desert lichens block the sun's rays.
If you are visiting a beautiful, natural place, you can usually find lichens. In California alone, they live in a wide variety of habitats. In the oak forest, they hang from oak branches. On the rocky shore, they form thin black crusts on rocks just above the water line where they are landing places for wind-borne ocean bubbles. In the desert, they form thin crusts on boulders.
To find lichens, look on tree trunks, the branches of trees (especially dead, well-lit branches), and exposed boulders. Sometimes I have seen what look to be 4 species of lichens on a single boulder.
The misnamed California Spanish moss is a fruticose, troll beard-like lichen. If you look closely, you will that it looks like a loosely knitted scarf. There are holes throughout the lichen.
Finding and enjoying lichens is easy, but identifying them is difficult. Expert lichen identifiers carry magnifying glasses and even chemical solutions. They apply the solutions to part of the lichen to see how the acid in the lichen will react. The type of reaction provides a key clue to identifying the lichen.
Right now, I am just trying to learn how to classify them into the 3 main shapes: fruticose, crustose, and foliose (see above for the description). Or how about just keeping a diary of lichen colors observed in nature?