Summer climate and conifer growth in mid-Norway: Chronologies from ancient construction timber compared with historical data

摘要

A tree-ring chronology derived from Norwegian timber structures made from Scots pine at locations near Trondheim dates back to AD 552. A chronology based on Norway spruce building timber from the .same area has been constructed back to AD 1351. Both Trondlicim chronologies, when tested for climatic signals, show a year-to-year pattern that correlates with the annual variation in the May-August letrathcrm from Trondheim dating back to 1870. Particular years in both these chronologies show correspondence with historical notes about the summer weather and harvests from 1575 until the mid-19th century. Especially cold summers resulted in unripe harvests and narrow tree-rings in both chronologies. However, several exceptions suggest that the growth of conifers and harvests sometimes responded differently to the same environmental factors (or more than one factor was important). The spruce chronology does not show reported long-term (decadal, century) climatic trends, probably because many samples had too few tree-rings. The pine chronology also shows little correspondence with longer-term fluctuations, probably because of heterogeneous material and/or too few samples. However, generally narrow ring widths from 1570 to the early 18th century may reflect a cold period. The data are promising, but results suggest that more samples and possibly more powerful statistics are required to extract reliable climatic signals from building timber chronologies.