Intra-annual dendroclimatic reconstruction for northern British Columbia, Canada, using wood properties

Abstract

Analyses of tree-ring wood properties combined with an understanding of tree physiology provided detailed intra-annual insights into historical and seasonal climate phenomena in sub-boreal forests of northern British Columbia. This study investigated historical climate trends in northern British Columbia, Canada, through the use of tree-ring proxies, and established a means of reconstructing intra-annual climate patterns from wood density, fibre properties and tree-ring width data. Specific attention was given to investigating how dendroclimatological analyses of intra-ring wood and fibre properties could be interpreted to improve the strength of proxy climate records. Trees were sampled at six sites in northern British Columbia. Spruce trees were collected from the Smithers area, whilst Douglas-fir trees were sampled at the northern latitudinal extent of their range near Babine and Francois Lakes, and at a precipitation-limited site near Valemount. Wood cores were analysed by Windendro® software with an ITRAX scanning densitometer, and by the SilviScan system located at the Australian Commonwealth Scientific and Research Organization. A mean June temperature proxy record dating to 1805 and a July–August mean temperature proxy record for Smithers extending from 1791 to 2006 were constructed from spruce ring width and maximum density chronologies. Douglas-fir ring width, spruce minimum density, and Douglas-fir maximum cell-wall thickness chronologies were used to reconstruct a May–June precipitation record extending from 1820 to 2006, and a July–August total precipitation record for Fort St. James that extends from 1912 to 2006. The results of the study demonstrate that a combination of multivariate and single-variate analyses provide detailed insights into seasonal radial growth characteristics. Tree physiological responses to climate at different times throughout the growing season, and temperature and precipitation fluctuations over the historical record are discussed.