With more than 600 species of lichens in Maine photographing and gathering a few, some for wreaths, one for a tincture, is one of my favorite winter pass times. During the cold months I am increasingly starved for color depending upon occasional sunrises, alpine glow, and sunsets for intensity. Once we had deep green evergreen mountains but all that is changing. Drab brown fuzz and skidder marks now cover the stripped mountains around my house. Lichens are an endless source for inspiration during these months because they glow green brown and gold with winter precipitation regardless of whether it is rain, ice, or snow.
In this article I am going to discuss a couple of different lichens that are favorites of mine. We have so many and seeking out these complex organisms can become a passion for others as it has for me! Some lichens are tolerant of pollution, others are disappearing, a result of decreasing air purity in Maine.
What follows is some general information about lichens that are reputed by some to be the first organisms to colonize land roughly 400 – 450 million years ago (the timeline keeps changing). The point is that lichens are ancient living beings who developed incredible strategies for moving from the sea to inhabit the rocks they found on land. Lichens are responsible for creating the first soil because they break down stone.
Lichens are composed of two or more dissimilar organisms that form a mutually beneficial (symbiotic) relationship. Together they produce a new vegetative body that is called a thallus. The life forms are composed of fungi and green algae and/or a cyanobacteria. Fungal filaments make up about 80% of the lichen body. The fungus forms the outer surface to provide support and protection, absorb moisture, and collect minerals from the air. Since the fungus cannot produce its own food, it is dependent upon algae to provide this essential function. Green algae and cyanobacteria possess the green pigment chlorophyll that is essential for photosynthesis. When surrounded by the fungi, algae/cyanobacteria provide the nourishment necessary to enable the lichens to exist and sustain themselves. Neither can survive without the other (s).
Unlike plants, lichens do not have leaves, stems, or roots, or a waxy outer cuticle to control body water content. Lichens continue to grow during periods when dew, mist, and rain water are present but during a summer dry period they often become dormant (photosynthesis ceases) until the next rainfall. Miniscule mineral particles that are carried by the wind during wet conditions are dissolved and absorbed by the lichen. They are able to photosynthesize in the winter as long as temperatures aren’t frigid.
Lichens produce their own food using sunlight, water, and air and do not feed on tree bark. The lichen bodies are attached to the outer bark and remain on the surface. Their rhizines (not roots) typically do not penetrate deep enough into the inner bark to cause harm to the trees they inhabit. This latter information is particularly important because many people associate lichen with dying trees and cut them down. I know I once did…
When I first came to this area I felI in love with a large ‘dying spruce’ that dripped Usnea lichen from every branch. Because I only remove trees that threaten the house, I left that one alone. I had no idea then, that almost forty years later, that this same tree would still be standing photosynthesizing away with Usnea hugging its branches, or wearing beards, casting threadlike tendrils in every direction. It is true that the lower branches of the spruce are bare, (allowing the lichen to absorb more sunlight) but above the limbs and tall spires are covered with needles. My point is that even if a tree is dying, the lichen inhabiting lower branches is not killing the tree. Instead, lichens keep the tree photosynthesizing for many years, so maybe it is best to simply leave the tree alone as I have continued to do. Most lichens like some mosses grow prolifically on trees. I find Usnea extraordinarily beautiful; clumps of silky hair or delicate reindeer -like branches sway in light winds…Often, while gazing up into my spruce’s branches, acclaimed author Terry Tempest Williams words will materialize out of thin air. “Beauty is not a luxury. It is a strategy for survival”.
However, it’s important to note that there are certain fungi that operate independently outside a lichen body that will penetrate tree wounds or dead wood and feed on a host plant. The filaments of the fungal body will reside inside the tree tissue with only the fruiting bodies visible on the surface.
There are at least 13,000 – 20, 000 species of lichens living throughout the world. Lichen species are so numerous and diverse that there are individual exceptions to most general statements made about them. Scientific knowledge about lichens has expanded significantly during the past few decades, and new discoveries continue.
Lichens can be divided into three types. Crustose lichens lie flat on the substrate and are the most tolerant of pollution. Look on any young maple or beech tree and you will see this lichen. Foliose lichens have a flat but leaf-like structure. Fruticose lichens are free standing like Usnea or ‘wrinkled lettuce’ (my name) lichen. The latter two are most sensitive to air pollution and are often found at the tops of trees, the limbs falling to the ground in high winds. Lichens can be seen in various colors -yellow, orange, red, purple, brown, etc. These colors are due to the presence of special pigment containing usnic acid. Most lichen species grow best where there is sufficient light and moisture within a moderate temperature zone. However, some lichen species are very adaptable and hardy.
When left undisturbed, lichens live in many varying climates and altitudes throughout the world. Some species can survive the most unfavorable climatic extremes of arctic, alpine, and desert regions by reducing metabolic activity for extended periods of time. Yet individual species may only exist within a restricted habitat or geographic range. Most lichens are sensitive to air pollution in varying degrees, and like canaries in coal mines, may serve as indicators of air quality.
Most fungi that form lichens produce microscopic spores in sacs. A fungus can produce millions of spores sexually. A new lichen association can be created only when fungal spores come in contact with the appropriate algae or cyanobacteria in the right habitat.
Lichen reproductive parts containing both algal and fungal cells may also occur asexually for dispersal. In vegetative reproduction, any fragment or shred of lichen containing both the algal and fungal components that breaks off the original can form a new lichen body.
This winter, though just beginning, has been hard on trees because all have been weakened by logging, insect damage, extreme temperature changes, and other effects of global warming. With so many broken and severed limbs on the ground it is easy to see that many are covered with lichens. I have already collected enough Usnea for this year’s medicinal tincture, something I normally don’t do until spring. My balsam wreaths are festooned with two species of Usnea and Fringed (‘wrinkled lettuce’) lichen. Every few days I soak these in warm water, so they don’t dry out (I love the shades when they are wet). In the spring I return them to the wild. My terrarium has a few Fringed lichen, tangles of Usnea, and a bit of Lungwort I found on the ground in my favorite forest after an animal had eaten most of what had been a large, rounded lichen.
As a fruticose lichen, Usnea appears as a shrub-like growth on host trees. Unlike other similar-looking fruticose lichens, species in this genus have an elastic chord or axis running through the middle of the thallus that can be revealed by gently pulling a filament apart from either end. In a healthy forest this lichen often cascades in clumps from bare branches, a beautiful sight. Based on a fossil found in amber, Usnea was present about 34 million years ago. Many animals love to eat this lichen (as well as others), so it is an important food source for wildlife.
The only place I have found Lungwort (Lobaria pulmonaria) is in my favorite forest; one that has been left to rewild itself. Lungwort likes humid forested areas with both maturing or old conifers and hardwood trees. It used to be quite common in its ideal habitat, a shady environment, quite literally ‘flowering’ from trees and rocks. Finding this lichen indicates rich, healthy ecosystems with very clean air. Lungwort is large, bright green, and leaf -like. The green algae gives it its startling, almost emerald appearance… attached pockets of cyanobacteria (blue green algae) are darker in color – a drab gray – and appear in sharp contrast to the green. In this forest I have found a number of healthy specimens some quite large and round, but sadly, in general, this lichen is becoming scarce, an indication of too much air pollution in Maine.
Green Shield, a foliose lichen is easy to spot on trees, especially on a cloudy day. This lichen is more tolerant of air pollution. Just this morning I was looking out my window towards the brook and could barely see any lichen because the sun was shining. A few days ago, it was cloudy, and lichens were visible everywhere I looked. I took a photo of Green Shield lichen on a healthy maple tree about 20 feet up and was amazed to discover that in addition to the one I photographed there were about 8 -9 other lichens I hadn’t seen previously! Some I have not yet identified. All were growing in a roughly 12x by 12 area. When I counted all the lichens and the sheet moss growing together a new question popped into my head. Why do different species of lichens grow together and why include mosses? Lichens apparently choose community living. And because lichens and mosses were the first organisms/plants to inhabit dry land maybe they like growing together? Pure speculation. I have no idea, but I want an answer to this question! Of course, needing a similar habitat would be one reason for clustering, but I have sense that there is more to it than that.
The last lichen I will mention is one that grows on top of a rounded stone that looks like mountain top. It could be Peppered Rock Shield, because this cluster likes sun. What I love about this lichen is the way it is slowly spreading over the ‘mountain’. Until the summer heat strikes it is a beautiful luminous sage green with nubbly skin. This lack of certainty on my part brings up an important point. Lichen hunting takes discernment, time, patience, and a willingness to revisit lichens frequently, and at different times of the year, always with a critical eye. I think it’s fitting that I should end this lichen saga with one I am unsure of, because with lichens one is always a beginner! I will be watching this one more critically this spring and summer when I am once again roaming through my favorite forest…
Before closing I am listing some other benefits of these ancient and complex organisms:
- Lichens that contain cyanobacteria can fix nitrogen
- Lichens cover eight percent of the earth’s terrestrial surface
- Lichens provide food for mule deer, whitetails, mountain goats, pronghorn antelope, northern flying squirrels and other squirrels, voles, wild turkeys, slugs, snails, mites, springtails, certain caterpillars to mention just a few animals.
- Lichens provide nesting material for 50 species of birds especially hummingbirds
- Lichens provide protection and background camouflage for lizards, certain moths, tree frogs. Lacewing larvae cover their wings with lichens
- Lichens are sand and soil stabilizers (especially in deserts – I witnessed this with a dark brown crustose lichen in NM)
I hope I have captivated a few peoples’ imagination and encouraged them to meander through our winter forests…
Happy Lichen Hunting to those that do!
2 thoughts on “Winter Foraging: Refuge”
Lichens are fascinating and the symbiosis between plants and fungi does get way more complicated and wonderful! 🙂
hmm not sure what you mean Tom about symbiosis between vascular plants and fungi – could you be more specific?