A DENDROCLIMATIC RECONSTRUCTION OF ANNUAL PRECIPITATION ON THE WESTERN CANADIAN PRAIRIES SINCE AD 1505 FROM PINUS-FLEXILIS JAMES

Tree-ring chronologies from living and sub-fossil Pinus flexilis James (limber pine) trees extend back more than 500 yr on the western edge of the Great Plains in Alberta, Living trees were found to be as old as 526 yr, Tree-ring growth in Pinus flexilis is most sensitive to annual precipitation over the annualization period August to July, The longevity of the trees coupled with their sensitivity to variations in annual precipitation make them an important resource for constructing annually resolved multicentury records of paleohydrology on the northwestern Great Plains, A 487-yr reconstruction of annual precipitation in southwestern Alberta was produced from the tree-ring series, This is the longest dendroclimatological reconstruction of precipitation available from the northern plains, The reconstruction has some similarity to reconstructions from the western Great Plains of the United States, However, there are also many divergences in the timing of droughts, Some of this divergence may reflect the importance of orographic uplift in producing precipitation along the eastern flanks of the Rocky Mountains, Our reconstruction shows that the frequency of droughts in Alberta during the period of instrumental records, about the last 100 yr, has not been appreciably different from conditions of the preceding four centuries, In addition, the most severe drought of this century, which led to,widespread farm abandonment between 1918 and 1922, was not the most severe drought in the past 487 yr. (C) 1995 University of Washington.