In February, I attended Community Nature Journaling at Shaver’s Creek. The day’s lessons focused on the biology and ecology of lichens. This event opened my eyes to lichenology and has been a source of many hours of study.
Lichens are the product of a symbiotic relationship between algae and fungi. The fungi is the dominant partner- dictating the lichen’s thallus to fruiting body. The algae is a type of cyanobacterium and provides food for the fungi. Lichens will grow on many substrates, and we will see them often on trees and rocks. Lichens are among the first colonizers of bare rocks. They aid in the development of better habitat for mosses and other plants.
Lichens grow on many different substrates in a vast array of environments. Lichens occur everywhere in Pennsylvania. Lichens are often accessible for study- my favorite place to find them are in parking lots! Even though lichens are common, they are very slow to grow and develop. It’s best to snap a picture and move on. Disturbing any lichen, especially a large one, will damage years or decades of growth.
My favorite lichen species is Flavoparmelia caperata – the Common Greenshield Lichen. This species is among the most common species of lichens in North America. On a tree, it has a bright, limey green foliose thallus. The edges of the leaves are smooth and feel tough and leathery to my touch. My second favorite is Parmotrema hypotropum – the Powdered Ruffle Lichen. This lichen reminds me of the tops of lettuce with their deep ruffled surface. The colors of the Powdered Ruffle Lichen aren’t as intense as my favorite, but are still beautiful to me.
Despite the variety of lichens, I’ve had a difficult time finding a definitive field guide. I’ve been relying on the Pennsylvania Bryophyte and Lichen Diversity Project on iNaturalist. I post my pictures and rough identifications, and a member of the project checks my work. I learn a lot from their corrections, and have become better at identification.
With the summer months coming, it will become more difficult for me to spot lichens. My favorite species’ preferred habitats are on trees. Once leaves emerge, I’m not sure if the lichens will be so easy to spot. Plus, any exposed rocks will soon cover with brush and vines. I’m hoping to spend the “off” months looking for a good field guide. One book exists, Urban Lichens by Jessica Allen and James Lendemer. There’s many websites that appear promising but are difficult to navigate.
The last few months have been full of lichen-related exploration and learning. I look forward to more en-lichen-ing discoveries as the seasons progress!
autumn's country diary 