X-ray microdensitometry applied to subfossil tree-rings: growth characteristics of ancient pines from the southern boreal forest zone in Finland at intra-annual to centennial time-scales |
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Authors: | Samuli Helama Matti Vartiainen Taneli Kolström Heli Peltola Jouko Meriläinen |
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Institution: | 1.Department of Geology,University of Helsinki,Helsinki,Finland;2.SAIMA Unit of Savonlinna Department of Teacher Education,University of Joensuu,Savonlinna,Finland;3.Mekrij?rvi Research Station,University of Joensuu,Ilomantsi,Finland;4.Faculty of Forest Sciences,University of Joensuu,Joensuu,Finland |
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Abstract: | A collection of subfossil wood of Pinus sylvestris (Scots pine) was exposed to X-ray densitometry. The collection of 64 samples from the southern boreal forest zone was dendrochronologically
cross-dated to a.d. 673-1788. Growth characteristics were determined by performing density profiles including the following parameters: minimum
density, earlywood and latewood boundary density, maximum density, earlywood width, earlywood density, latewood width, latewood
density, annual ring width and annual ring density. Seven out of the nine parameters were found to contain non-climatic growth
trends and six were found to be heteroscedastic in their variance. Tree-specific records were indexed, to remove the non-climatic
growth trends and stabilize the variance, and combined into nine parameter-specific tree-ring chronologies. Growth characteristics
of the pines changed in parallel with the generally agreed climatic cooling from the Medieval Warm Period to the Little Ice
Age: pine tree-rings showed decreasing maximum densities from the period a.d. 975-1150 to a.d. 1450–1625. A concomitant change in the intra-annual growth characteristics was detected between these periods. The findings
indicate that not only the trees growing near the species’ distributional limits are sensitive to large-scale climatic variations
but also the trees growing in habitats remote from the timberline have noticeably responded to past climate changes. |
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Keywords: | Dendrochronology Little Ice Age Medieval Warm Period Pinus sylvestris Tree-ring densitometry Wood anatomy |
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