Overview

Lichen are a fascinating mutualistic complex composed of two organisms, which are fungus and green alga/cyanobacteria, with green alga being most prevalent. The green algae or cyanobacteria are the two principle photobionts and are considered to be subordinate to the fungi, with the fungi composing the majority of the observable form and its characteristics.  The most common type of fungus present in Lichen is ascomycetes, referred to as ” sac fungi”. The photobionts function as the energy producers via photosynthesis and the fungi, in turn, feed on that created energy to then propagate themselves. 

https://www.fs.fed.us/wildflowers/beauty/lichens/about.shtml

LICHEN BIOLOGY

Anatomy

Lichen can be broken down broadly by the illustration below. The overall body of the lichen is referred to as the thallus. Within the cross-section, the top layer is the upper cortex, which acts as a skin-like barrier and is made up of firmly compressed cells. Below that is the algal layer seen as a green section that receives and utilizes sunlight and moisture to produce energy through the upper cortex. Below this follows the medulla, which is a more loosely put-together layer of hyphae that resemble cotton. Lastly, the cortex sandwich is capped off with the lowest layer: the lower cortex. This needs little explanation, as it is functionally the same as the upper cortex. The below-labeled apothecium is the cup-like spore-producing organ that is also made up of hyphae. And finally, the layer which adheres is the Rhizine. They are responsible for anchoring the lichen to its surface.

LICHEN BIOLOGY

Morphology

Lichen most frequently take the morphological forms as follows: crustose, foliose, and fruticose. Crustose can be differentially by a few factors, the first being its thickness. They are very thin, hugging tightly to their substrates. They are frequently seen in circular form and are described as being no thicker than a coat of paint. Crustose lichen also lack lower cortex and rhizine and instead frequently opts for a more aggressive approach by penetrating into their substrate to settle themselves. This may work for them, however, they are more difficult to detach from their substrates without their more solidified lower cortex and rhizines. Foliose lichen are more raised from their substrates, with their growth, likewise, occurring at the outer margins in a circular fashion. Foliose lichen are the template for describing lichen, as nearly all of them possess all the anatomy depicted in the above section. Lastly, fruticose lichen resemble miniature trees with leafy protrusions that can come up from the ground or hang down like a pendant from their tree branch. They lack circular growth patterns, instead appearing more voluminous and shapely. They also lack a definite top and bottom like foliose, and can even have a hollow center.

LICHEN BIOLOGY

Uses

Lichen have many uses for both humans and their surrounding wildlife. For humans, they have been used for dyes, with lichen such as Lobaria pulmonaria being frequently mixed with pine sap or water, among many other additives, to create dyes for their clothing. Some Indigenous peoples of America would consume lichen. For instance, the lichen genus Bryoria was consumed when food was a bit more scarce. Among wildlife, they have been used by some insects as a form of camouflage to avoid predators or as building materials for birds looking to make their nests.

https://www.fs.fed.us/wildflowers/beauty/lichens/didyouknow.shtml#:~:text=Lichens%20have%20been%20used%20for,large%20part%20of%20their%20habitat.

Documented Lichens

This is a Plitt’s Rock Shield lichen  (Xanthoparmelia plittii), a sandstone-loving species found in the surrounding area of Duranceau Park. It is a foliose lichen and possesses an upper portion that is yellow-green and a lower surface that is tan to light brown. They are found on sloped or horizontal surfaces facing the sun. They commonly possess apothecia and grow to be around several inches with the ability to coalesce into larger-sized structures. Lastly, their lobes are more narrow in appearance.

Next is the lemon lichen or Candelaria concolor, a smaller species with lobes too small to see without a hand lens. They are considered foliose, but their lobes are too small and this lichen can often be mistaken for crustose. Its color is greenish-yellow or lemon yellow and its undersurface is white. They rarely, if ever, have apothecia, instead, having soredia. These are propagules that can be scattered to allow asexual reproduction. They grow on bark in the full sun most often and prefer their bark to be softer, like ash trees.

Following the lemon lichen, I spotted a hooded sunburst lichen (Xanthomendoza fallax). They are foliose lichen with a golden yellow thallus. They frequently grow on the bark of mature trees, specifically in open areas to get high doses of sunlight. Their color can closely resemble lemon lichen, and one way to distinguish the two is by use of KOH, as the sunburst lichen turns a lovely shade of deep purple.

Finally, we have the frost lichen (Physconia) are a genus of lichen that, as its name suggests, all appear frosty in color. They are foliose, with a brownish-gray to brown thallus, and have elongated lobes. Ohio has four species within this genus but two are the most common:  P. detersa and P. leucoleiptes.

LICHENS TO KNOW

Bryophytes

The plant shown below is a liverwort species known as Porella platyphylla. They are a leafy liverwort found frequently in temperate regions. They are a dull yellow-green and their branches are pinnate.

https://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=1240&context=bryo-ecol-subchapters

https://fieldguide.mt.gov/speciesDetail.aspx?elcode=NBHEP2Q0H0#:~:text=Porella%20platyphylla,-*%20Plants%20may%20catch&text=Their%20dull%20yellow%2Dgreen%20color,lobule%20margins%20are%20slightly%20revolute.

The moss I was able to find is known as poodle moss, or Anomodon attenuatus. This species looks mat-like and is a dull green in appearance. They can be found most frequently at the bases of trees. They possess overlapping leaves along the entirety of the stem’s length with leaf tips that are acute but can also be narrowly rounded as well. Their midribs also do not reach the tip of the stem.

Chinquapin oak

The Chinquapin oak, or Quercus muehlenbergii, is a common species of oak that grows in the greater Midwest. It grows in soil ranging from average moisture content to moderately dry, and can also live in soils that are mildly acidic (sandstone) to a more alkaline pH (limestone). They can reach heights of ~60 feet with light gray flaky to platy bark integrity. It can best be characterized by its leaves, as they are alternate in arrangement but have an instantly recognizable leaf shape of a flint arrowhead with its serrations facing away from the tree.

Chinquapin Oak, Chinkapin Oak, Rock Oak, Yellow Chestnut Oak

https://ohiodnr.gov/discover-and-learn/plants-trees/broad-leaf-trees/chinquapin-oak-Quercus-muehlenbergii