White spruce light rings in northwestern Canada

Light ring chronologies are developed from white spruce (Picea glauca [Moench] Voss) at six sites in the Yukon and western Northwest Territories of Canada in order to evaluate their spatiotemporal distribution and to investigate the climatic factors leading to their formation. The chronologies, produced using both living and subfossil material, vary in length from 350 yr to 800 yr. In several key years during the common interval A.D. 1641-1989, light rings developed in a majority of trees at all or most of the sites, indicating their usefulness for regional cross-dating of tree-ring records. Comparison of light ring records with climate data at the northernmost site suggests white spruce light ring formation is related to below average June to August tempertures, with an emphasis on low August temperatures. Prominent white spruce light ring years in northwestern Canada are different from black spruce light ring years in northern Quebec, probably due to the differences in synoptic circulation patterns between the two regions, and thus cross-dating may be limited to the regional scale.