Dendroclimatological analysis of seeded and thinned Scots pine (<Emphasis Type="Italic">Pinus sylvestris</Emphasis> L.) stands at the coniferous timberline |
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| Authors: | Samuli Helama Hannu Salminen Mauri Timonen Martti Varmola |
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| Institution: | (1) Department of Geology, University of Helsinki, P.O. Box 64, Helsinki, 00014, Finland;(2) Finnish Forest Research Institute, Rovaniemi Research Unit, Rovaniemi, Finland |
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| Abstract: | Radial growth was examined in two Scots pine stands that were seeded during the 1920s and 1930s due to reforestation and afforestation
activity on the timberline of northern Finnish Lapland. Tree-rings of seeded pines were calibrated against the instrumental
records of local weather and large-scale atmospheric patterns and further compared to pines of natural origin on the timberline.
The studied stands were shown to contain common growth variability that differed from the variability of natural pines. Deviating
growth of seeded pines was attributed to their only moderate growth dependence on mid-summer (July) temperatures and, likewise,
their strong dependence on the autumn climate in the previous year, and linked to the different genetic origin of artificial
stands due to southern seeds. Stands were thinned for different densities in 1985 and 1986. The growth response to thinning
was markedly better than could be expected according to previous studies. We found that the positive growth reaction conceivably
benefited from the ameliorated winter conditions, expressed as warmed (March) temperatures and the prolonged positive phase
of the Arctic Oscillation (February). The results emphasize the determining influence of climatic fluctuations on reforestation
and afforestation near the distributional limits of tree species. |
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| Keywords: | Afforestation Subarctic Tree-rings Arctic Oscillation Northern Annular Mode Lapland |
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