Direct Measurement of Lichen Growth in the Central Brooks Range, Alaska, U.S.A., and Its Application to Lichenometric Dating

Abstract

The growth of 92 Rhizocarpon geographicum s.l. and 57 Alectoria minuscula Nyl. lichens was measured over 4 to 6 yr in the Atigun Pass region of the central Brooks Range, Alaska. Absolute growth rates of R. geographicum s.l. were inversely related to thallus diameter and ranged from 0.35 to near 0 mm yr⁻¹. In contrast, A. minuscula growth rates were directly related to diameter and ranged from 0.14 to 2.01 mm yr⁻¹. A growth curve derived from mean rates of R. geographicum s.l. growth is similar to the indirectly controlled lichenometric dating curve for this region, but cannot yet be used to modify ages assigned to Holocene deposits. The derived growth curve for A. minuscula closely resembles those from the eastern Canadian Arctic.