by Donna Bollenbach
The tiny moss has been the theme of many a gifted poet; and even the despised mushroom has called forth classic works in its praise. But the Lichens, which stain every rock, and clothe every tree, which form:
Nature’s livery o’er the globe
Where’er her wonders range Have been almost universally neglected, nay despised.
|Christmas Lichen on a fallen tree, Florida. |
Imagine our continent after the last ice age: Glaciers cut deep gorges in the land and miles of granite boulders, silt and the bones cover the hills and plains of North America. Life has all but disappeared, but there is hope for new life in a simple living entity that is neither plant nor animal, the lichens.
|Lichens on a rock in Yellowstone National Park. |
Lichens, a partnership of a fungus and an alga, are able to survive in the most extreme temperatures. The lichens that partner with cyanobacteria, or blue-green algae, produce their own nitrogen, so they are able to grow on nitrogen-poor substrates. They form colonies on the surface of the rocks and bare soil. The chemicals in these lichens are capable of penetrating and breaking down the rock. As the lichens die the debris becomes thicker and nitrogen rich. Mosses began to grow. The decay of the mosses and lichens make the soil even richer, allowing other vegetation to take hold and a new habitat evolves.
For this reason, lichens and mosses are considered pioneers of succession. Today, they are still the primary plant-like species of the deserts and tundra where they thrive in conditions that are inhospitable to most other plants. They are also an important source of food for animals in those extreme climates where other vegetation is scarce.
|Fruiticose lichen in the Florida Scrub|
– from the Greek word tapis for carpet; a fabric with a woven design resembling tapestry, varied entwined and intricate (i.e. the tapestry of life).
Lichen, a living organism that is neither plant nor animal, is one of nature’s true tapestries. A fungus and a suitable green alga or cyanobacteria (blue-green alga), intricately woven together in a symbiotic union, lichens carpet trees, rocks, soil and other substrates with their rich colors and textures.
There are over 14,000 species of lichen living in nearly every habitat in the world. In addition to rocks, lichen grows on an array of natural and manmade substrates, including bark, stone, wood, soil, leaves, moss, bone, human artifacts and even some living creatures. Unlike the pioneer lichens that break down rocks, lichens found on living substrates are not parasitic, they simply use the host as a place to live.
FORM & BEAUTY
Yet lovely was its pleasant shade; Lovely the trunk will moss inlaid; Lovely the long-haired lichens grey; Lovely its pride and its decay.
|Crustose Lichen on a Palm Tree|The task of defining and classifying lichens is a daunting one for scientist. The international Association for Lichenology defines lichen as “an association of a fungus and photosynthetic symbiont resulting in a stable vegetative body having a specific structure.” Noted Lichenologist, Trevor Goward, went further to describe lichen as “fungi that have discovered agriculture.” Scientifically, lichens are classified by one of four general growth forms: Foliose (leafy, lobed and most often with an upper and lower cortex), Fruiticose (hairy, tubular, multi-branching strands or lacey balls with a single cortex), Crustose (crusty, flat patches that can be somewhat smooth or thick and bumpy) and Squamulose (an intermediate between the Crustose and Foliose, with thick, scaly shingles).
|A combination of lichen forms and mosses on tree bark.|
While these scientific terms do suggest the general shape of the lichen classes, they do little justice to the lichen’s true beauty.
The Foliose lichens have a leaf-like form. They have many lobes., often curling slightly inward and layered on top of each other.
|Foliose lichens on a tree. |
The Fruticose lichens are highly branched. They can be thin and stringy, or round, lacy and soft in appearance. Some of the Fruticose lichens found in the scrub look like puffy greenish gray clouds.
|Fruiticose lichens, or powder puff lichens in the Florida Scrub. |
The Crustose lichens are flat, often circular patches, tightly adhered to their substrate. Colorful fruiting bodies adorn their cortex.
|Crustose, or flame lichen growing on a rock. |While many lichens are white to greenish-grey to brown, many are bright red, yellow or orange. Even a green or gray lichen may be adorned with a bright red fruiting body. Some of the fruiting bodies are mere dots, while others are more like little mushrooms. The combination of color and texture in lichens are as varied as the substrates they live on, and have given many a painter or photographer a reason to pause and admire nature's finest fabric.
|Foliose lichen (British soldiers) with an Earth Star (fungus) in the center. |
And these are all the reasons I Love Lichens!
If you also love Lichens, check out this great book: "Lichens of North America" by Brodo, Sharnoff & Sharnoff.
It is rather expensive, but it is nearly 800 pages of fascinating information and beautiful color images.