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Research article2007Peer reviewed

Long-term vegetation changes in the northern Scandinavian forest limit: a human impact-climate synergy?

Karlsson H, Hornberg G, Hannon G, Nordstrom EM

Abstract

A palaeoecological study was performed in the northern Scandinavian mountain range in Sweden. The aim was to study vegetation changes and shifts in forest limit altitudes during the last 5000 years in a tree-less archaeological site (Adamvalta) situated below the regional forest limit, and in a forested reference area with similar geological features but without archaeological evidence of human presence (Ajdevaratj). The suitability of uncritically using forest limit changes as indicators of climate change is also discussed. The study included analyses of pollen, pollen accumulation rates (PAR), macrofossils and loss-on-ignition. The results indicate vegetation changes in both areas plausibly caused by climate c. 3800 BP and c. 500-400 BP. However, at Adamvalta, settlements were established c. 1300-750 BP, close to the mountain birch (Betula pubescens ssp. czerepanovi) forest limit. About 800 BP, the birch forest cover at Adamvalta decreased and the vegetation developed into an alpine heath, as a result of human-induced deforestation. The following 'Little Ice Age', in combination with human impact from the sixteenth century onwards, prevented forest recovery, and the site remains treeless. Such vegetation changes were not recorded at Adjevaratj. It is deduced that the present position of the forest limit at Adamvalta is governed by a combination of factors where previous human impact and climate have been the major driving forces determining the long-term vegetation development. Hence, a thorough knowledge of the site history is important when forest limits are used as a proxy for climate change

Published in

Holocene
2007, Volume: 17, number: 1, pages: 37-49
Publisher: SAGE PUBLICATIONS LTD