Lichen Growth Rates for the Northwest Coast of Spitsbergen, Svalbard

Abstract

Growth curves for Rhizocarpon subgenus Rhizocarpon and Pseudephebe minuscula have been developed for the northwest coast of Spitsbergen. The curves were constructed by measuring lichens on deposits of known age (natural and anthropogenic) spanning the last 350 yr. The Rhizocarpon curve is comprised of two growth segments: a fast-growing great growth period (21 mm 100 yr^-1) lasting ca. 100 yr and a slower-growing phase (4.5 mm 100 yr^-1) between 100 and 350 yr. Growth rates beyond 350 yr are not known, and the curves should be extrapolated with caution. Rhizocarpon growth rates on Spitsbergen are similar to those in the eastern Canadian Arctic, greater than those in the Brooks Range of Alaska, and less than those in adjacent areas. The P. minuscula curve is constrained for the last 80 yr but senescence and rejuvenation of P. minuscula thalli on whaling features of the 17th century preclude firm control beyond 80 yr.