This last week we were on the troop summer week long scout camp up in the High Uintas of Utah. As we were hiking along between Trident and Beth Lake, I noticed that there was a ton of lichen on all the rocks. I realized that I did not know anything about lichen, except that it is usually found growing on the rocks. So, here is a few thing that I have found from my research.
Because lichens do not have a waxy cuticle like plants, they cannot conserve water during drought periods. On the other hand, lichens can absorb everything through their cortex, including water and water vapor. Many lichens are found in foggy areas like the coast, but not farther inland simply because there is not enough water in the air to support them.
When lichens are wet, they "turn on" and start photosynthesizing and growing. When lichens are dry, they "turn off", become brittle and go dormant. This process is known as "poikilohydry", and other organisms such as mosses and liverworts operate in the same way.
The simplest way to tell if lichen is dormant or growing is by looking at its color. The darker black or brighter green lichen is, chances are that it is photosynthesizing. Of course, if it is wet and pliable, that is a good indication too.
If lichen looks pale and is dry and brittle, then it is dormant and waiting for the next rain or fog event before it starts photosynthesizing.
Lichens need clean, fresh air to survive. They absorb everything through their cortex. From beneficial nutrients to harmful toxins, lichens absorb it all. They also absorb water in the air, which is why so many are found in fog belts along oceans and big lakes.
Just like all living things, lichens need nutrients to survive and grow. The main nutrients include nitrogen, carbon, and oxygen.
Similar to plants, all lichens photosynthesize. They need light to provide energy to make their own food. More specifically, the algae in the lichen produce carbohydrates and the fungi take those carbohydrates to grow and reproduce.
Lichens need homes too! Every lichen lives on top of something else. The surface of that "something else" is called a substrate. Just about anything that holds still long enough for a lichen to attach to and grow is a suitable substrate. Trees, rocks, soil, houses, tombstones, cars, old farm equipment and more can be substrates. The most common natural substrates are trees, rocks, and soil.