If you like to keep track of milestones, today is Botany Photo of the Day's six month anniversary. I suppose I should celebrate the milestone with a showy flower, or at least some colour other than green (the dominant colour in many recent photos), but I'm going to sneak in one more “green thing” before sharing some autumn colours over the next few days.
Lobaria pulmonaria, or lungwort, is a lichen found widely around the world. I've not been able to track down a complete distribution for the species yet, but I've so far found references to: western North America, eastern North America, central and northern Europe, boreal forests of temperate Asia, and an interesting outlier, India (with its subtropical / tropical climates).
This species is highly sensitive to sulfur dioxide. An increase in atmospheric pollution is partly responsible for a noticeable decline in the species over the past century (habitat loss is another), so much so that it is often listed as endangered or rare in countries of Europe.
Although this lichen commonly grows on trees, mossy rocks and wood in shady mature forests, I found it on the side of a path, apparently fallen from a tree. Sad perhaps (for the lichen), but essential as part of a nutrient input process in old-growth forests. Lobaria pulmonaria hosts a nitrogen-fixing cyanobacteria, which pulls in atmospheric nitrogen into the body of the lichen. Eventually, when the lichen falls to the forest floor and decays, the nitrogen is then added to the soil, providing a necessary nutrient for a suite of plants. Marie Antoine, in “An Ecophysiological Approach to Quantifying Nitrogen Fixation by Lobaria oregana” (The Bryologist Vol. 107(1)) found that the related species, Lobaria oregana, could add over 15kg of nitrogen / hectare to the soil every year in some of the studied sites!
Photography resource link: May the Art Be With You, an article by Donna Bollenbach for Nature Photographers Online Magazine, reminds that the artistic quality of the photograph should be considered before pressing the shutter button.