Lake Level Changes Indicated by Dendrochronology on Subfossil Pine, Jämtland, Central Scandinavian Mountains, Sweden

Abstract

Not only do high-latitude tree-ring data reveal minor and major Holocene climatic variation, but the distribution in time of subfossil trees provides information about former tree-line fluctuation. Over 152 samples of Scots pine (Pinus sylvestris) were collected and measured from lake Lilla Rörtjärnen, situated close to the present treeline. Five floating chronologies were built spanning 498 B.C.–A.D. 19, A.D. 50–390, A.D. 431–884, A.D. 946–1256, and A.D. 1337–1865. The floating chronologies were crossdated with a dendrochronology from Torneträsk. No trees were dated from 20–49 A.D., 391–430 A.D., 885–945 A.D., and 1257–1336, A.D. The temporal distribution of pines in the lake suggests periods of intensive germination, with each phase occurring within 80 to 100 yr from the beginning of each floating chronology. At the end of each phase higher lake levels drowned trees close to the shore. Both the existence and the preservation of the dead pines is likely to have been controlled by changes in lake level.