What is a Lichen?
Wandering through the backyard I noticed quite a few areas of stuff growing on rocks, trees, and wooden posts. I just had to go take a closer look!
Wow! Amazing! What is this stuff!
The amazing stuff I found is called lichen. So, what is lichen anyway? Is it a plant? Is it an alga? Is it a fungus? Is it even alive? What does it do? What makes lichen so amazing and special?
What is Lichen?
Scientifically, a lichen is a type of fungus and a type of algae that live together in a mutual relationship that benefits both the fungi and the alga. That really sounds like a mouthful. What it all comes down to is that the fungus and the algae combine into one organism to help each other survive.
The fungus forms a protective layer around the algae. It provides a safe place for the algae to live. It also provides a moist environment so that the algae can survive in areas it normally would not be able to live. In return, the alga uses sunlight and carbon dioxide from the air to photosynthesize and produce food for both itself and the fungus.
Where are Lichens Found?
Lichens can be found worldwide even in Antarctica! There are more than 13,500 species of lichen in the world. You can find them growing on bare rock, on fence posts, on tree bark, on bare soil and sand, and even in desert environments!
The unique partnership formed between the fungus and algae that make up the lichen means they can survive in some of the hottest and coldest of environments. They can survive temperatures as hot as 420 F and as cold as -450 F. They can live off of wind-borne water, dew, and minute bits of wind-borne debris. During times of drought or dry spells, lichens can dry up and go into a dormant state. Then when enough moisture reaches them, they absorb the water and start growing again.
Why are Lichens so Special?
Lichens are very long lived. In Northern areas, there are lichens that may have been around when the glaciers of the last ice age were in retreat! They are also very slow growing.
Lichens are also very susceptible to air pollution. Toxins in the air can kill the lichen over time. Because of this, Lichens are considered an indicator species for the environmental health of an area. By measuring the rate of growth or decline of the lichen in an area, scientists can get a pretty good idea of the air pollution levels in that area.
What Do Lichens Do?
Lichens are considered pioneer organisms. They are often the very first organisms to live on barren surfaces such as rock or in barren environments such as in desserts. As liches grow, they produce an acid excretion that breaks up rock or other hard surfaces. Over time, this produces a shallow indent that the lichen happily lives in. The broken-up materials from the surface the lichen lives on builds up slowly over time. It combines with tiny wind-borne particles to form tiny pockets of soil.
Given more time, moss, plants, and other species also start living in the soil. The decaying matter from the plants over the year build up and eventually a little habitat is formed that may even one day grow into an entire forest. Pretty cool, right?
There is so much more to explore about lichens!
For instance:
How many types of lichens are there?
Do animals eat lichens or use them in any other way?
Do people use lichens for anything?
There are lichens growing on my tree. Are they going to hurt it?
So many question and not enough room here to answer them. It just means I get to explore more about lichens on another page of my Backyard Journal! And I get to go out and take more photographs of lichens!
References:
1. Mauseth, James D. Botany - An Introduction to Plant Biology. Saunder’s College Publishing, USA. 2nd edition. 1995
2. Kochanoff, Peggy. A Field Guide to Nearby Nature - Field and Woods of the Midwest and East Coast. Mountain Press Publishing Company, Montana, USA. 2nd printing. 1994.
3. Bennet, Doug and Tim Tiner. The Wild Woods Guide. Harper Collins Publishers Inc, New York, USA. 1st edition. 2003
4. Alden, Peter et al. National Audubon Society Field Guide to New England. Alfred A Knopf Inc, New York, USA 1st edition. 1998
