“There is a low mist in the woods—
It is a good day to study lichens.”
― Henry David Thoreau
Most of the lichens in this blog will be those found on rocks and on the ground because right now they are the most interesting to me. Some are displaying interesting and colorful fruiting bodies now even though it is January, perhaps because of the warm weather an wet conditions.
Lichens are organisms whose general structure consists of layers of alga and a fungus. These symbiotic partners have different functions. The green alga (and sometimes a cyanobacteria as well) is the photosynthetic partner (photobiont) and is also the food factory of the lichen. The fungus provides an anchor to a substrate and provides reproductive capability through spore production. The composite body of the lichen is called the thallus.
Lichens have distinct color variations when wet or dry. The color when dry is the color of the particular fungal component of that lichen. When wet, the fungal cells become transparent and the color of the algae beneath them can be seen, usually in variations of green.
The three most common lichen types are fruticose, foliose and crustose. Each has a distinctive appearance and structure. Squamulose lichens combine both the foliose and crustose thallus forms.
Fruticose lichens have a lobed thallus and appear leaf-like. They have an upper and lower layer. They can look like small shrubs as they may have branching. Some have a podetial, which are stalks, and these will produce fruiting bodies on their tops. Examples of this type of lichen include the British soldier lichen, reindeer lichens and the pixie-cup lichen.
Foliose lichens have a three-dimensional thallus with upright structures or a pendulous habit. They often have a leafy appearance. Rock tripe is a good example of a foliose lichen.
Crustose lichens have a one- dimensional crust-like thallus. The lower surface adheres firmly to the substrate which is usually rocks or tree trunks and branches, so they are difficult to remove from whatever they are growing on. Some crustose lichens look like painted bands on tree trunks.
Spores are produced in a structure called an apotheciuim which may be a disk or cupped body with. asci on the exposed flat or concave surface. In pixie cup lichens, the apothecia appear on the edges of structures that look likelook like tiny goblets, Apothecia of other lichens resemble tiny balls on stalks. The most common forms are disks.
Spores from a lichen need to connect with the same cyanobacteria/algal partner of the original organism. Some lichens can replicate through breakage where both the fungal element and the photobiont element remain together. In many cases, mat-forming ground lichens can reproduce through breakage easier than lichens found on trees and rocks.
Rim lichens, genus Lecanora are crusticose lichens named from two Greek words for small bowl and beauty. They are found on rocks or trees and the body (thallus) is granular like sugar. Disks are variant in color. Before the disks open, they look like small blobs.
The best new lichen I found this January was the pink earth lichen Dibaeis baeomyces. They are found on disturbed soils like sand or clay with full sun, and can they cover the ground over time. The ones I found covered an area of 20 square feet on a power line right-of-way.
I also am enamored of the Cladonia pleurota red-fruited pixie cup lichens. They have splash cups that look like tiny goblets that will fill with rainwater to disperse the spores. The spore structures are red and arise along the edges of the cups. They occur on soils, bark, wood or rock in full sun to some shade. Often British soldier and wand lichens can be interspersed with pixie cups.
Reindeer lichens, Cladonia spp., resemble puffy, light green to gray foamy sage brushes. These prefer very sandy or thin soils or exposed bedrock, and they can easily be dislodged by foot traffic. In the right conditions, they can cover the ground with puffy mounds. A good consideration for a groundcover for areas with little to no traffic.
Common goldspeck, Candelariella vitellina, is found on granite( check old rock walls) in full sun. This lichen has a chemical called calycin that acts as a sunscreen which helps regulate sun intensity as needed by the algal layer.
Concentric boulder lichen, Porpidia crustulata, is a pale gray-green crustose lichen found on rocks in full sun or in the shade. The dark brown disks can appear black, and run in uneven concentric circles within the thallus edges.
While lichens may be found on tree trunks and branches, they do not harm plants. Thay have the ability to fix nitrogen from the air which benefits nearby plants. They are also a food source and sheltering site for animals, especially the foliose lichens. They are also a nest construction for many including blue-gray gnatcatchers, vireos and ruby-throated hummingbirds.
If you are inspired to discover the fascinating world of lichens, be sure to bring a good hand lens. The tiny reproductive disks of some lichens, especially the crustose ones found on rocks, can be easy to miss. Look up and down and all around for lichens- on the ground, trees, rocks and even on fences…
Pamm Cooper
Uconnladybug's Blog 