Friday, March 17, 2017

Life on the Watershed: The Inimitable Lichen

Freddy Fungus met Annie Alga, and they took a lichen to one another.    
They made their home in a nearby native oak,
and were always there to support their woodland community neighbors.

There’s nothing else quite like it. Two separate organisms (a fungus and an alga) combine into a totally different life form—lichen. The two original parties coexist in mutual dependence: the fungus is on the outside to capture water and minerals from the atmosphere for the alga within,while the alga produces food for both of them by photosynthesis. Together, they are a ready friend to other oak woodland community dwellers. 

We see different species of lichen  in various colors on rocks, trees and other surfaces—but  only where the air is clean enough for it to survive, like the Peninsula Watershed. Always especially noticeable is the pale greenish lace lichen, drooping in thick long strands from nearby native oaks.

Lace lichen may look like a parasite that’s weakening or killing the tree. But it’s actually a source of extra nourishment because its broad surface area captures nutrient-rich dusts blowing in from the ocean. Rains then wash the accumulated oceanic dust into the ground, where soil bacteria break down the nitrogen for the tree roots to take in. (Trees with lace lichen are healthier and grow faster.) Lichen photos by Shelly Benson  

Along the tree’s branches, lace lichen harbors spiders and insects,which are food for various birds. Some bird species, like house finches, tuck their nests inside lichen clumps, where eggs and checks are protected from predators. 

Others, like hummingbirds, will line their nests with lace lichen, or weave its strands along the outside. Voles and other rodents use it to line their nests, and fallen lichen pieces are food for deer, rabbits and other woodland animals.

For us, the presence of lichen is an indicator of clean, healthy air. Pollution will kill it off.  


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