A high Late Holocene tree-limit and the establishment of the spruce forest-limit – a case study in northern Sweden |
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| Authors: | LEIF KULLMAN OLA ENGELMARK |
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| Institution: | Department of Physical Geography, UmeåUniversity, S-901 87 Umeå, Sweden;Ola Engelmark, Department of Natural Sciences, Swedish Mountain Museum, S-960 40 Jokkmokk, Sweden |
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| Abstract: | Radiocarbon dates of subfossil pines found on dry ground above the present-day tree-limit are reported from northern Sweden. The uppermost and oldest specimen germinated c. AD 300–600. During some shorter part of this interval the tree-limit might have been 235 m higher than it was at the turn of the last century. Based on a current adiabatic lapse rate of 0.7°C per 100m, it may be tentatively deduced that the summers were at least 1.6°C warmer. The pine tree-limit and upper pine populations are inferred to have declined substantially shortly after AD 600. The tree-limit reached a low at the end of the Little Ice Age. In parallel with the warming of c. 1°C during the first half of the 20th century the tree-limit advanced 110m altitudinally. Spruce forest dominance seems to have increased at the study site during the first half of the 19th century, when thermal and hygric conditions may have been optimally balanced. Although basically a direct climatic response, it can be hypothesized that the spruce expansion was facilitated by the pine demise during the Little Ice Age. |
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