A 250-year-long height-increment chronology for Pinus sylvestris at the northern coniferous timberline: A novel tool for reconstructing past summer temperatures?

A 250-year-long chronology of Scots pine (Pinus sylvestris L.) height increment was reconstructed for the northern timberline based on material collected from four stands in Lapland: Finland and Sweden. The height increment of pine was lower in the 18th and 19th centuries than in the second half of the 20th century. The amount of common variability was 38% in the old material and 44% in the material representing the 20th century. In the latter case, half of the common variability was explained by the mean July temperature of the previous year, but the data representing earlier centuries correlated less strongly with the July temperature. We can conclude that due to a strong common signal, height-increment series are a promising tool for reconstructing summer temperature on the regional scale at the northern timberline. Because of the ongoing global warming, information on past tree-height increment could improve predictions about the possible changes in timberline ecosystems.