Amateur Naturalist: A Study In Lichen

The vertical canyon walls and a stream in Hidden Valley in the Valles Caldera together provide and hold water vapor, which can then support plants that are different than in more open areas. Photo by Robert Dryja

By ROBERT DRYJA
Los Alamos

Think about a pot of boiling water on a stove. Bubbles of water vapor can be easily seen rising in the pot to surface. Vapor then cools just enough to appear as steam saturating the adjacent clear air.

Temperatures are in the range of 200 degrees at this point. Now observe a cup of warm coffee or tea. The cup may feel warm when held and steam may not be visible. However, the air just above the surface of the coffee or tea also may feel warm it you hold your finger close to it. Temperatures now are in the range of 100 degrees with water now in a form of invisible vapor.

Now consider plants. Plants need water to live. Do you suppose plants can benefit when water vapor is cool enough? Can a plant somehow drink water vapor? How could we observe such a thing?” There are places where it is possible to see this. This involves going to a canyon with a particular shape. The canyon may be shaped somewhat like an elongated pot. It should have openings at two ends and a small stream flowing through it. The walls of the canyon on each side of the stream ideally will be from fifty to one hundred feet apart. The walls also should rise vertically for sixty or more feet while the stream bubbles along in between.

A canyon like this exists in the Valles Caldera. In effect it is like a huge pot that is stretched out for half a mile. The stream flowing through it provides cool vapor but the vapor only can escape at the ends of the canyon. The air in the canyon is cool for most of day and so does not raise up over the tops of the canyon walls.

The plants in the canyon are different from elsewhere and the change is immediately apparent when entering the canyon. Whereas ponderosa pine trees are the more common tree outside of the entrance of the canyon, other kinds of conifer trees become common inside. The conifer trees can live comfortably where there is more shade and cooler compared to the ponderosa. This difference also can be seen when going up the side of a mountain. Ponderosa are the dominant tree at lower, warmer elevations while conifer replace them at cooler, higher elevations.

Something startling happens with other plants in the canyon. What looks like Spanish moss appears everywhere, hanging from the trees. But where does Spanish moss normally grow? It is found in the southern states closer to the ocean. But this canyon is high the mountains and far from the ocean. Are we really looking at Spanish moss or at something else? (Spanish moss is not from Spain and is not a moss by the way.)

It is easy to look closely at these mystery plants. It is hanging everywhere from the conifer tree branches. The plants are like batches of string hanging down and the strings have small threads growing out of their sides. These whitish, stringy plants may remind a person of an old man’s beard. They are not at all like a plant with leaves.

The shape provides a clue. There is a type of lichen called old man’s beard. The trees are covered with lichens, not a regular type of plant. A lichen is composed of a fungus and algae living together. The  fungus provides the structure to hold the algae and the algae grows food for the fungus. These lichens do not have any roots growing into the branches of the trees. The trees only provide support for the lichens to hang on.

All of the lichen is growing on trees close to the stream. They stop growing on the trees that are toward the top of the canyon walls. The lichens at the stream side are receiving needed moisture from the water evaporating from the stream. This moisture becomes disbursed at the top of the canyon walls and no longer available.

The canyon therefore is like a very large pot that provides air moisture from the stream flowing through. The more commonly seen lichen grows like a small piece of flat paper on a boulder or other large rocks. Even when shaded there is not as much water vapor present. The stringy type of lichen in in the canyon in contrast lives successfully by hanging from trees where it is moister, shadier and cooler.

‘Old Man’s Beard’ is a type of lichen hanging from tree branches in a Valles Caldera canyon. Photo by Robert Dryja

Flat, paper-like, colorful lichen on a boulder away from stream water in the Valles Caldera. Photo by Robert Dryja

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