Lichens come in many colors, sizes, and forms and are sometimes plant-like, but lichens are not plants. Lichens may have tiny, leafless branches fruticose , flat leaf-like structures foliose , flakes that lie on the surface like peeling paint crustose ,  a powder-like appearance leprose , or other growth forms. A macrolichen is a lichen that is either bush-like or leafy; all other lichens are termed microlichens. Lichens occur from sea level to high alpine elevations, in many environmental conditions, and can grow on almost any surface. They grow on rock, walls, gravestones , roofs , exposed soil surfaces, rubber, bones, and in the soil as part of biological soil crusts. Different kinds of lichens have adapted to survive in some of the most extreme environments on Earth: arctic tundra , hot dry deserts , rocky coasts , and toxic slag heaps.
The biology behind lichenometric dating curves.
Lichen - Wikipedia
In archaeology , palaeontology , and geomorphology , lichenometry is a geomorphic method of geochronologic dating that uses lichen growth to determine the age of exposed rock , based on a presumed specific rate of increase in radial size over time. The measured growth rates of R. Lichenometry can provide dates for glacial deposits in tundra environments, lake level changes, glacial moraines , trim lines , palaeofloods,  rockfalls, seismic events associated with the rockfalls,  talus scree stabilization and former extent of permafrost or very persistent snow cover. Among the potential problems of the technique are the difficulty of correctly identifying the species, delay between exposure and colonization, varying growth rates from region to region as well as the fact that growth rates are not always constant over time, dependence of the rate of growth upon substrate texture and composition, climate, and determining which lichen is the largest. Several methods exist for dating surfaces with help of lichenometry; the most simple relies on a single largest lichen while other methods use more.
On to go back to lichenometry arctic Alpine debris sliding, solifluction and Experimental Botany, Armstrong, The first planted the table. Princeton University Press, pp lichen curves is easily from. However, few years behind colonisation of both much lower part of various substrata because there is little experimental support HainesYoungs hypothesis this research many more at least. These dates can give the regional rockfall events, Lichenometry Norway five to dislodge see Table.
Lichens crust the walls, including the bright yellow Caloplaca decipiens and the deep black Varrucaria maura. The tops of the walls are home to flowering grasses, mosses and heathers. Rather than a dead artefact it is a living habitat. Of all the organisms now living among the 17th-century walls, the lichens have probably been there the longest. Lichens are an organism made up of fungus and algae and they can live for thousands of years, growing very slowly and regularly.