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Carden Alvar Lichens By Bob Bowles (Reprinted from Prairie Smoke) Index Lichens are classified as cryptogams, a class of lower plants along with algae and mosses. However, lichens are very special plants which are really two different organisms living together in a harmonious association referred to as symbiosis. The lichen thallus is formed by a green or blue-green algae and colourless fungal threads called hyphae. The new composite organism acts as a single independent plant with the green alga manufacturing sugars by photosynthesis and the fungus making up the plant body and living off these manufactured foodstuffs. Lichens most often grow in open, exposed sunny places and grow on a substrate which are trees, dead wood, rocks, tombstones, mosses, soil, and other substrates. Each species of lichen usually grows best on only one substrate so a species that grows on rocks is usually not found on trees. When you think of how lichens are made up it makes sense that a perfect habitat for this organism would be on the Carden Alvar. The limestone substrate is everywhere in exposed sunny locations. Harsh conditions like spring flooding and then dry, hot summer conditions are too extreme for many plants which would crowd out and shade the lichen. The wet conditions for the algae in the spring then the dry conditions favoured by most lichens make the alvar a perfect lichen habitat.
Sometimes the species can be identified in the field using growth form and colour but in many cases a microscope and chemical tests are needed to confirm the species. There are four major growth forms for lichens. They are foliose (leaf-like), fruticose (shrubby or hair-like), crustose (crust-like), and squamulose (small lobelike structures). Colours vary from orange, lemon or sulphur yellow, yellowish-green, whitish mineral gray, greenish mineral gray, brown, slate blue, to black. The colour should be judged after the thallus is air-died and can be matched with a colour chart in good light and chemicals can be used to determine the pigment involved. Lichens on the Cameron Ranch Bob Bowles photo Many of us recognize some widespread, common lichens. Reindeer moss, Cladina rangiferina, which is not really a moss but a lichen, is found growing on soil and humus in open areas sometimes in extensive colonies. The body is branching and whitish to ashy or brownish gray. Similar speices C. subtenuis and arbuscula are more pale yellowish gray. C. stellaris has more compact heads and C. mitis has finer branching. All species are similar so a chemical test may be needed for final confirmation. Cladonia cristatella or British Soldiers is another lichen that is common on humus, soil, and rotting logs in open areas. The mineral gray branches are tipped with flaring cups that are red. False Pixie Cups, Cladonia chlorophaea is another common lichen usually growing nearby which have greenish mineral gray cups but there are other similar cup lichens. Rock Tripe, Umbilicaria vellea growing on exposed cliffs and boulders and Old Man’s Beard, Usnes hirta which hangs down from the branches of hardwoods and conifers in open areas are two more examples of common lichens. Three species of lichens common on the Carden Alvar are Golden or Sunburst Lichen, Xanthoria elegans which grows commonly on exposed cliffs and boulders in rock cribs. Placynthium nigrum is brownish black and closely appressed on exposed limestone in open areas and very common. Dog Lichen, Peltigera canina has a light brown leaf-like thallus that grows in abundance in the thin layer of soil over the limestone. Many more species of lichens can be found on the alvar but these three are abundant and easy to identify but there are other similar species. When you start looking for and studying lichens a walk over the alvar takes on a whole new world of discovery.
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