Use of an aggregated Rhizocarpon'species' in lichenometry: an evaluation

A regular relationship exists between the growth of lichen species within the Section Rhizocarpon and Rhizocarpon alpicola. This can be quantified and used to adjust lichenometric dates to take into account differences in the growth rates of the two groups. R. alpicola colonises deposits later than Section Rhizocarpon species, although subsequent growth by R. alpicola is rapid. If the two groups arc not separated, important dating errors may arise.