The Carlisle Mosquito Online

Friday, June 24, 2005

Features


Pink Earth

(Photo by Kay Fairweather)

As we approach the celebration of the bicentennial of the town on Old Home Day, it is appropriate to acknowledge one of nature's pioneers. Pink Earth is a lichen that is known as a soil colonizer. It arrives on bare soil and strongly and surely, starting from nothing, it makes a better place for those that follow. The fungal threads in the lichen wrap and bind the soil particles and stabilize them. The lichen eventually adds nitrogen and organic matter to the soil and improves its fertility. Other lichens, living on tree trunks for example, are just hanging out in their high-rise homes with a view, while down at ground level the pioneering Pink Earth is hard at work on ecological improvement.

Name: Pink Earth is a lichen with the scientific name of Dibaeis baeomyces — pronounced "duh-buy-us buy-o-my-sees." In older references it might show up as Baeomyces roseus. Lichens along with mosses, liverworts fungi, algae, and ferns are often grouped under the name "cryptogam," meaning "hidden marriage," which refers to their use of spores rather than seeds for reproduction.

Lichen Diversity: Lichens are composite organisms made up of fungi and algae. Many fungi exist as lichens but only a very few species of algae are ever lichenized. For that reason, the lichen always takes its scientific name from the fungal component. There are over 14,000 species of lichens in the world. During the state-wide program of Biodiversity Days this year (June 4 through June 12), two lichen experts, Doug Greene and Deb Lievens, identified 66 different species of lichen in the Green Cemetery. Some were growing on the stone walls, some on trees, some on the ground, some on gravestones, and some on the mortar holding the stones on the Church Street gate posts.

When and where seen: I first noticed a patch of Pink Earth fruiting in the Green Cemetery late in March. There are still large patches in the older part of the cemetery on the left side of the track if you enter through the Church Street gate. It is fitting that the gravestones shading some areas of Pink Earth are those of Phineas Blood and his daughter Sarah Ann, members of one of Carlisle's pioneer families.

Distinguishing characteristics: Pink Earth grows like a crust on the surface of bare ground, especially sandy or acidic soil. Despite its colorful name, the main body of the lichen (called a thallus) is pale greenish-gray or almost white. When it is wet it looks a little more green and is a bit slimy. When the lichen fruits, it produces a secondary thallus made up of sturdy grooved stalks about a quarter inch tall, each with a rounded pink head. At this stage it looks like a field of tiny pink mushrooms which are sometimes so abundant that the ground looks pink. The pink heads are the spore-generating parts of the fungus. It is hard to recognize this lichen when it is not fruiting but it is unmistakable when it is fruiting. The spore-bearing heads are decidedly pink. There is another crustose soil lichen of similar structure which has brown heads. Some of the older patches of Pink Earth that fruited in March (e.g. beside Benjamin Foster's obelisk ) have faded but you can still tell they were pink.

Xanthoria elegans, or the elegant sunburst lichen
Fireworks: Another lichen in the Green Cemetery called Xanthoria elegans, or the elegant sunburst lichen, does important waste disposal work converting nutrient-rich bird excrement (nutrients are relative) into vivid orange sunbursts — a cryptogamic version of fireworks that celebrates the balance of nature and honors the efforts of the humble Pink Earth.

References: Lichens of North America, by Brodo, Sharnoff and Sharnoff.

Submissions for the Biodiversity Corner are encouraged from everyone. Send your ideas, your nature photos, or the whole column to Kay Fairweather at 392 School Street, Carlisle MA 01741 or to kayfair@comcast.net.


2005 The Carlisle Mosquito