If you’re interested, could you show/name some of the main lichen that grow on open rock in the Canadian Shield? I grew up seeing them during canoeing trips and fishing lodge jobs, and got really disappointed when I realized that I don’t know enough about lichen to recognize when you’re posting about one I’ve seen! (I keep thinking one is, and then finding out it only grows in Australia or South America.) :(
That is a rather large area that encompasses a lot of different habitats with a lot of lichen diversity, but I will do my best!
Found this nice picture on iNaturalist from the Berens River in Manitoba that might be similar to the habitat you are describing:
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The bright red/orange lichen is Rusavskia elegans, a really common colonizer of sun-exposed rock. I also see a few species of Rhizocarpon, aka map lichens. They have that thick, black prothallus visible around the margin of the lichen and between the angualr thallus sections. The leafy pale yellow-green lichens are likely species of Xanthoparmelia, maybe X. cumberlandia or X. conspera, which are both fairly common in that part of the world.
Looking around at other pictures on iNaturalist, I am seeing quite a bit of Physcia caesia:
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Aspicilia cinarea:
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Dimelaena oreina:
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and Umbilicaria muhlenbergii:
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If the lichens you are remembering aren't here, I highly recommend poking around on iNaturalist in the specific area you are thinking of and seeing what you can find!
