TREE-RING DATING OF EXTREME WATER-LEVEL EVENTS AT LAKE-BIENVILLE, SUB-ARCTIC QUEBEC, CANADA

Disturbances in shoreline forest margins during the past century were dated at Lake Bienville, Quebec, using various dendroecological indica tors. Trees in upper shore positions were disturbed by waves and ice e rosion. These geomorphic events were dated using compression wood, ice scars, and traumatic annual rings. Trees that established during favo rable episodes in the 19th century have been severely destabilized by shoreline disturbances in most decades since 1881; 1881-83, 1912, 1922 , 1936, 1947-48, 1958-59 and 1974-79. The age structure of shoreline s hrubs indicates recent colonization associated with low lake levels (g auged since 1974). The results support a hypothesis of shoreline distu rbances caused by early snowy winters and subsequent high lake levels.