The bark of a Bear Oak is dark gray, think, smooth and becomes fissured and scaley over time. The tree also invites lichens. In the picture below the furrowing has begun and the light green spots are lichens.






November May 9, 2017

If you frequent nature trails, (click here) you have likely passed by stones or trees with some kind of crusty material on the surface.  Is it a moss?  No, moss is a plant.  Is it a fungus?  Well, yes and no.  This crust is actually a partnership between at least two different organisms, making a composite organism called lichen (pronounced “LIKE-en”).

Lichens are made of multiple fungi – a diverse group of organisms including mushrooms, molds, yeasts, and others – living with algae and/or algae-like bacteria called cyanobacteria.  The fungi provide a pleasant, hydrated shelter to live in, while their partner provides food through photosynthesis.  Photosynthesis means using sunlight, water, and CO2 to create sugar (and the oxygen that we breathe, no big deal).  Cyanobacteria can also “fix” or make use of nutrients from the air, further helping the fungi to grow.  This mutual relationship between different species is what biologists call symbiosis.

Thanks to the many possible fungi-algae-bacteria combinations, lichens take on many different forms and colors.  In New York State alone, there are over 800 types of lichens!  Lichens can look like small flaky crusts (“crustose”), flat leaf-like growths (“foliose”), or even branched (“fruticose”) like miniature shrubs.   Many take on a greenish-grey hue, but other colors include brown, black, white, yellow, bright orange, red, and blue.  You might see these unique fungal partnerships on all kinds of surfaces along nature trails – adding a nice flair to wooden sign posts, historic stone walls, boulders, tree bark, the forest floor, and decaying logs....