Lichen Growth Curves for the Southern Flank of the Mont Blanc Massif, Western Italian Alps

Abstract

Growth curves spanning the last two and a half centuries have been constructed for Rhizocarpon geographicum s.l. and Aspicilia cinerea, two ubiquitous lichen species that grow on granitic substrates on the south side of the Mont Blanc massif. Ages derived from arithmetic and semilogarithmic plots of control data are nearly accordant over the past 275 yr, but beyond that point derived ages are increasingly discordant. The curves are suitable for dating granitic substrates of unknown age within upper Val d'Aosta between altitudes of approximately 1100 and 2000 m. Outside these geographic and altitudinal ranges the growth curves may not be applicable, as suggested by published growth curves for other parts of the Italian Alps.