Natural History of the Pacific Northwest Mountains: Timber Press Field Guide (A Timber Press Field Guide) by Daniel Mathews

Author:Daniel Mathews [Mathews, Daniel]
Language: eng
Format: azw3
Publisher: Timber Press
Published: 2017-03-21T04:00:00+00:00

crust lichens

Map Lichen

Rhizocarpon geographicum (rye-zo-car-pon: root fruit). Chartreuse yellow patches broken by fine black lines and surrounded by a wider black margin. On rocks; abundant in exposed situations.

Rhizocarpon geographicum and a less-colorful relative, R. macrocarpon.

Crust lichens grow at slow but steady rates. Especially steady, and ubiquitous on arctic and alpine rocks, map lichen dominates the science of lichenometry, which uses lichen growth to measure time—for example, the time since glaciers retreated from rocks that now bear lichens. Radial growth rates of 3 and 3⅓ mm per century, after a slightly faster initial growth spurt (ha ha) typify map lichens in the US Rockies: 3000-year-old lichens are 4–4½ inches in diameter.

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