With all of the tall trees and bright colors around campus, it is easy to focus on the more prominent features of the Haverford College Arboretum. However, I encourage you to pause for a moment and take a look at the smaller things on campus, the organisms that contribute a lot to the ecosystem. Lichens and mosses are both incredibly important, and often overlooked, features of the Arboretum. 

Lichens form as a symbiotic relationship between an alga and a fungus, primarily taking characteristics from the fungus. Although lichen and moss can visually appear very similar, they are quite different. Lichen, unlike moss, is not a plant! They lack roots, stems, and leaves, and can only photosynthesize through the algal component. Mosses, on the other hand, are plants (they are likely the ancestors of our current trees, flowers, and ferns!), and have plant-like structures such as stems and leaves.

Although they are small, both lichens and mosses provide incredibly valuable environmental benefits. Lichens are great indicators of a healthy environment, as they typically can not survive in areas of significant air pollution. If you notice lichens on your walk, chances are you are witnessing a healthy ecosystem! In addition to being great indicators of environmental health, lichens also purify the surrounding area, detoxifying the air. Similarly, mosses are also a great indicator of ecosystem health, as they also require a clean and healthy environment to survive. Mosses can remove toxins from soil and air (including carbon dioxide!), making it healthier for other plants to grow. Mosses can also absorb significant amounts of water, preventing erosion. 

Mosses and lichens are particularly beneficial to our environment, so where can we go to see some? Common lichens in the Philadelphia area and on campus include Cladonia coniocraea (Common Powderhorn), Punctelia rudecta (Rough Speckled Shield Lichen), and Flavoparmelia caperata (Common Greenshield Lichen). Common mosses in Southeastern Pennsylvania include Entodon seductrix (Cord Glaze Moss), Dicranum scoparium (Broom Moss), and Thuidium delicatulum (Delicate Fern Moss). Check out the areas on and around trees, on rocks, and in moist environments to see what you can identify. Next time you are outside, take a look at these smaller, yet crucial, features of the Arboretum, and enjoy the finer details of campus!

Sources:

U.S. Department of Agriculture 

Arizona State University 

Reconnect with Nature

National Park Service