Colorful lichens on Valencia County rock

Walking around the hills in Valencia County you will have noticed the small patches of wildly colored vegetation covering old boulders. These lichens (pronounced like the verb “liken”) are slow-growing interesting organisms, and are a composite life form consisting of two, and sometimes even three, completely different species which live in a symbiotic, mutually beneficial relationship.

Most lichens consist of a species of fungus, with a species of plant green algae or a species photosynthesizing bacterium. The fungus consists of a dense matrix of filaments completely enclosing the photosynthesizing algal or cyanobacterium components thereby protecting them from intense sunlight and preventing them from drying out. In turn, the algae or cyanobacteria are able to use the sunlight’s energy and by photosynthesis provide food and nutrients for the fungus.

Lichens are classified based on the shape of the fungus: crustose (flat, crust- and paint-like coatings that are very firmly attached to the rock), foliose (leaf-like that can be easily picked off), and fruticose (looking like a tiny bush). Lichens are very slow-growing, spreading laterally outward from their point of inception in most species at rates typically less than 0.1 inch per year.

Growth rates within certain species, particularly the crustose species, tend to be very constant through time, and this can be used to estimate the minimum time that the surface has been exposed. This has been measured on old gravestones and used on glacier deposits to date past glaciations events.

Because moisture is critical for the growth of lichens, they are typically more widespread on the northern side of the rocks in the northern hemisphere where there is less sunlight. This can be readily confirmed on the outcrops of the rocks on the El Cerro de Los Lunas Preserve.

In New Mexico lichen has been reported as a forage for antelope, but human use of lichens as a food in North America’s Southwest was apparently never significant. However, lichens have long been used as medicine and as a natural dye for yarn, textiles and basketry.