Returning to Lichens

January 17, 2024

Once again, I want to talk about lichens. January is the best time to see these unusual organisms because the leaves are gone from the trees, and the rain brings them to life as they spread on the trunks and branches.

California is home to over 2000 species of lichen. Lichens are a group of organisms – fungi, alga, and cyanobacteria, living together in a community. This relationship is being studied and is seen as mutualistic, symbiotic, and even potentially parasitic. Questions arise when these relationships are investigated because it is not easy to separate whether the algae and the fungi are helping each other equally or if the fungi are using the algae to do their bidding. Some literature describes the fungi tending or harnessing the algae like a farmer does a crop. Then there are the different cyanobacteria, which are found to be essential in the organism, but their actual role is not totally understood. They make food from sunlight and CO2 for the fungi, as do the algae that live in the lichen.  In most lichen species, the fungi cannot survive without the photobionts (algae and cyanobacteria). If the photobionts and the fungi are separated into their constituent parts in a lab, they can’t be reunited to create the original lichen. One theory is that the process of lichenization (the binding of fungal spores and photobionts to create a lichen) may depend on bacteria. In other words, how lichens function and create different and specific life forms is still a mystery.

In 2016, the first official state lichen was announced by Governor Jerry Brown. It is the lace lichen, Ramalina menziesii. Some might refer to this lichen as ‘net lichen,’ due to the flat net-like pattern it forms when hanging from large valley oaks. Lace lichen droops down in clumps and long tresses up to three feet long, and its yellow-green color stands out against a darker background. It can be found in Southern Alaska to Baja. It is an important food source for elk and deer and is used by many birds for nesting material. Lace lichen can be confused with another lichen commonly found in the valley called Old Man’s Beard, Usnea spp. This is a pale-green lichen that can be shrubby-looking or pendulous. It is identified by the rubber-band cord within the stem-like branches. This can be observed when a branch is pulled apart. 

Lichens are known for their sensitivity to pollution and climate and are being used across California to monitor air quality and climate change. Stephen Sharnoff, co-author of the book “A Field Guide to California Lichens,” states in an article for the California Oaks Society that lichens are part of the diversity of California oak habitats. “Everywhere that oaks live, a varied lichen community grows on them.”

Lichens have evolved with our native trees and do not harm them. They do not have roots that invade the bark of the trees. A substantial lichen population is not a sign of a sick or dying tree. They will colonize a dead tree because there is more sunlight for them to use, but they are not the cause of the tree dying. When lichens fall from branches during storm conditions or from animal activity, their decomposition provides many nutrients for the tree and other surrounding vegetation.

Lichens are fantastic and mysterious ecosystems of organisms that are living all around us. When I look out at the trees in the Willits area and see not only the number of lichens but the variety of them, it tells me we have excellent air quality. That is something to celebrate.