The biogeographical status of Alnus crispa (Ait.) Pursch in sub-Arctic southern Greenland: Do pollen records indicate local populations during the past 1500 years?

Phytogeographical studies of southwestern Greenland suggest that Alnus crispa is not native to the far south of the island. Palynological investigations dating to the 1970s concluded that this was the case throughout the Holocene, with the regular occurrences of Alnus seen in pollen diagrams from this region explained as the result of long distance transport of alder pollen from Canada. Recently, macrofossil evidence from an archaeological site in southern Greenland has emerged that indicates that alder was amongst the fuel resources available to the Norse settlers around AD 1000-1400. In light of this discovery, we present data from thirteen pollen diagrams produced since 2008 to re-examine the past status of Alnus within southernmost Greenland over the last 1500 years. Only at one site with a very large pollen source area do Alnus pollen frequencies regularly exceed a threshold which may be interpreted as indicating a regional presence for the plant. This pattern is argued to be consistent with the presence of a small but variable regional population of the plant, perhaps restricted in its distribution to the inland district of Vatnahverfi.