By Sara Wright
The tree lichen stopped me in my tracks. Nature’s artistry. Imaginative clusters of pale green rosettes captivated me with lacy patterns engendering a sense of awe. The lichens and I leaned into that moment when relationship is born or deepened. Developing a friendship with lichens, fungi, plants, or creatures changes the way we experience them. Interconnection becomes reality through embodiment.
You would have thought I had never seen a lichen before, and this lichen was a common one that the experts call Physcia tenella, which tells me nothing besides ‘where it belongs.’ If we only focus on facts and information, how do we enter the experience of wonder that such beauty exists at all?
The iterating rosettes created intricate patterns as they wound themselves around the maple bark along with about five other lichens and a liverwort. I almost tripped over my snowshoes to follow the communal ‘tree story’ being written there in front of me. One of the joys of snowshoeing through my own forest is that year after year I can visit the same slow-growing lichens I love so well.
Happily, my tree lichen bears the common name ‘fringed rosette lichen,’ which describes some aspects of what I see. It grows throughout the world on nutrient-rich twigs and tree branches, occasionally making a home on stones. The ‘fringe’ indicates a high nitrogen content in the biome where it grows. The fact that it grows well in a nitrogen-rich environment means it can thrive in our increasingly polluted air.
What are lichens? A lichen is composed of two or more organisms that form a beneficial (symbiotic) relationship to produce a new body called a thallus. These life forms are composed of a fungus, a green alga and/or a cyanobacterium. The fungus makes up about 80 percent of the lichen’s body which provides support and protection, absorbs moisture, and collects minerals. But the fungus cannot produce its own food. Green alga/cyanobacteria photosynthesize; they provide nutrients for the fungus so the lichen can thrive. What a partnership!
Lichens are categorized in groups based on their body forms and features. The three main body groupings are crustose (crust-like), foliose (leaf-like), and fruticose (tube or beard-like strands). Unlike plants, lichens do not have leaves, stems, or roots. They attach themselves to trees, stones etc. by means of rhizines. Lichens grow during periods when dew, mist, and rain are plentiful, but a summer dry period can cause them to become dormant until the next rainfall. Sometimes I collect some lichens during the warmer months and let them dry out and then water them the following winter. It is amazing to watch them come back to life.
Lichens are categorized in groups based on their body forms and features. The three main groupings are crustose (crust-like), foliose (leaf-like), and fruticose (tube or beard-like strands).
For me, the importance of lichens lies in their ability to function in a symbiotic partnership. That is still true today, even in the face of five extinction events throughout our planet’s history.
There may be about 13,000 (or more) lichen species throughout the world, and most grow best where there is sufficient light and moisture, but some manage in the arctic and in deserts, too. However, lichens can also be extremely sensitive to air pollution which leads to shrinking numbers in some species.
Lichens provide important benefits both in nature and in human culture. They are eaten by many animals, such as deer, mountain goats and caribou. Also, some species of birds use lichen materials in constructing their nests. Certain lichens are used in producing antibiotics.
Lichens may reproduce in a sexual, asexual, or vegetative manner. Lichen sexual reproduction is quite complicated because two or more organisms are contained in the lichen. The algae or cyanobacteria do not have recognizable reproductive parts and do not reproduce sexually after they are in a lichen association. The sexual fruiting bodies of lichens are those of the fungi. Most fungi that form lichens are sac fungi (Ascomycetes) that produce microscopic spores in sacs. A fungus can produce millions of spores sexually. A new lichen association can be created only when fungal spores encounter the appropriate algae or cyanobacteria in the right habitat.
Lichen parts containing both algal and fungal cells may be dispersed and allow for asexual or vegetative reproduction. A fragment or shred of lichen containing both the algal and fungal components can break off the original and form a new lichen body. In some circumstances, the fragments must break down into undifferentiated fungal and algal cells before new lichens are created.
This is a perfect time of year to visit with our ancient relatives, the lichens. A discerning eye will see them stand out against the trunks of both conifers and deciduous trees. Once you find a cluster, count how many other lichens are growing alongside or around the tree mosses. If you take the time to pay attention, I promise that you will be amazed.
Comments