Real tough guys - lichens

Having dodged the worst parts of an ice storm, a few days of warmer weather are predicted where the daytime temps will be above freezing. Along with this comes rain, but with the ground still frozen, a lot of runoff is expected.  Here and there a few sprouts of early bulbs are peeking out.  However if you want to see some happily green organisms, start looking at tree bark and branches.  Without the crown of leaves, more sunlight will fall on tree trunks than you might expect, and lichens take advantage of this. These are really tough organisms. Tree bark, stones, cement, these are really hard substrates; organisms growing there are highly exposed, subject to desiccation and temperature extremes, and yet in places the lichens are almost luxuriant.  Locally common lichens grow as a crust and so don't look as lush as the larger, more branched or leafier types (fruticose or foliose).  Although TPP is not adept at identifying lichens, he loves the Lichens of North America; a wonderfully illustrated atlas of lichens (just the ID keys and other field guides are also available).  Should you decide to give it a go, you'll run into a bit of a terminological learning curve and the need of come magnification.  Maybe a kind reader will offer some suggestions about the lichens shown here.

If you don't already know this, lichens are symbiotic organisms, basically a fungal body housing symbiotic algae. The algae can still be free-living, and so to the fungus, but neither one alone looks like the lichen.



Birth of a lichen

Lichens are symbiotic organisms consisting of a highly organized fungal mycelium enclosing algal cells. What's strange about lichens is that without the algae, the fungus just looks like a fungus. Without the fungus, the algae is just algae. They only take on the form recognized as a lichen when the two organisms are in that symbiotic association, and of course, the term itself means "living together". This presents some interesting aspects of reproduction. This illustration is from the November 2014 issue of the American Journal of Botany.  The sexual reproduction of the lichen is fungal in nature, so to form a new lichen, the fungus must capture a compatible algal cell anew.  This illustration shows this very early stage where fungal hyphae (filaments) have found and encircled an algae cell. The proliferation of the hyphae and the division of the algal cell is a demonstration that the symbiotic interaction, the lichenization, has begun. The accompanying article by William Sanders provides illustrated diagrams of the sexual and asexual reproductive cycles of lichens, all very nicely done.

lichen-covered picture frames

Rob asks TPP: I like to make picture frames from old barn wood. I recently acquired some wood that has lichen on it and thought it would be cool to have some on the frame but do not know whether or not it would be harmful to humans in a household environment. Also if it isn't I would assume it would maybe dry up and just crumble off or disintegrate or would not last. Any ideas on this. I do not know the name of this lichen, I live in West Central Minnesota and see it all over the granite outcrops, roofs of house, on trees and wood. Thanks for any help.
In answer to your questions: Lichens are not harmful to humans in a household environment.  However humans can be quite harmful to lichens; in urban areas they can be the canaries in the coal mine type of indicators of air quality (they don't like pollution).  Depending upon the lichen, they would just desiccate and could last on the wood for a considerable period of time, especially crusty lichens.  They actually make "living walls" of lichen-covered bark or wood, but your living picture frames would require some occasional moisture (not good for the pictures) and some light, although not necessarily much of either.  TPP doesn't know the name of your lichen either having never seen it.  On the diverse substrates you mention, there would be multiple kinds of lichens.  There is a nice book called Lichens of North America, it has an identification key, but it's rather technical; all the wonderful pictures might prove more useful.  Maybe a local university library will have a copy.  It's a big book. The image shows several lichens on an old birdfeeder in the Smokey Mountains of North Carolina, so yours would be different.