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The wood is sanded with progressive finer paper to expose the growth rings for counting and measurement of ring width. The fundamental technique in dendrochronology is cross-dating, whereby distinctive series of narrow and wider tree rings are identified and matched among trees of different ages.Calendar years can then be assigned to rings from dead wood.
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.
On the upper valley sides, slump blocks and the associated soil and vegetation commonly remain intact, despite the considerable displacement of bedrock.
The failure is deep below the surface, over a curved plane, causing the block to rotate and the trees to tilt backward towards the scarp face.
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.
Although a belt of aspen parkland extends across the prairie provinces, much of the original aspen polar was removed for crop production and this tree species is much inferior to coniferous trees for tree ring research (Fritts, 1976).
However, conifers in the treed uplands and sheltered coulees tend to be climatically sensitive (Sauchyn and Beaudoin, 1999).
Much of the tree ring research in western Canada has at the Laboratory of Tree Ring research in Tucson, Arizona, including the first studies of Douglas Fir in Alberta (Schulman, 1947), the first regional dendrochronological network for western North America (Drew, 1975), regional climatic reconstructions (Fritts, 1971; Fritts, et al., 1979; Fritts and Lough, 1985), and a dendrohydrological study of the Peace-Athabasca delta (Stockton and Fritts, 1973).