Douglass (1920) illustrated the relationship between climate and ring width by plotting both against time, and introduced the technique of cross dating by correlating ring-width signatures (sequences of wide and narrow rings) among trees distributed over large areas.In western Canada, dendrochronology has been largely confined to the montane and boreal forests (Case and Mac Donald, 1995; Luckman and Innes, 1991).Dendrochronology, the study of the annual growth in trees, is the only method of paleoenvironmental research that produces proxy data of consistently annual resolution. Initially the cells are thin walled to conduct the abundant spring soil moisture.As soil water declines through the summer, the cells become thicker-walled and more dense.Additional tree-ring material can be obtained from historical buildings.Theory of cross-dating is a key to built composite chronologies from living, historical and subfossil tree-rings.An investigation of fire and insect infestation frequency in the jack pine forests of Manitoba (Gill, 1930) was the first Canadian study to use ring-width data and cross-dating techniques to develop a tree-ring chronology.Shortly afterwards, Powell (1932) compared variation in wheat yields in Saskatchewan to ring-width variation in white spruce and some hardwood species.
However, prior to any proxy-based climate or environmental reconstruction, a calibration between the proxy archive and an instrumental series is required.Thus each annual ring consists of early (light) and late (dark) wood. Douglass, the 'father' of dendrochronology was interested in the affect of sunspots on the earths climate.Tree-ring series can be classified as either complacent (uniform ring widths where moisture and heat are sufficient throughout the growing season) or sensitive (pronounced year to year variation in ring width, where conditions are frequently near the limits of the trees tolerance, e.g. The search for proxy climatic data was the original application of tree rings. In 1901, he noticed ring-width variations on a cut log and reasoned that these were controlled by the tree's environment (Fritts, 1976).The ring widths, the anatomical characteristics of the wood, and other features of their growth vary from year to year with changing environmental conditions.Current tree-ring oriented research at the Department of Geology includes wide spectrum of dendrochronological science.