DEVELOPMENT OF A BLACK SPRUCE (PICEA-MARIANA) SHORELINE STAND IN RELATION TO SNOW LEVEL VARIATIONS AT LAKE BIENVILLE IN NORTHERN QUEBEC

This study proposes a reconstruction of the past development of a fore st stand submitted to long-term variations of snow levels. As of the 1 9th century, a gradient in tree-growth forms developed in a post-fire shoreline stand. This expansion was marked by three stages. (1) Prior to 1845, the effects of fire (between 1806 and 1826) increased the exp osure stress on surviving trees, which started to develop irregular gr owth forms in response to niveo-eolian erosion. Post-fire regeneration expanded progressively toward the inner part of the island. (2) After wards (1845-1880), severe winter and summer conditions were marked by numerous unsuccessful snow-air interface breakthroughs, as shown by fr equent loss of apical dominance. (3) Since 1880, the densification of above-snow tree structures contributed to the overaccumulation of snow that caused many injuries to trees (branch tearing, stem bending). Th e frequent damage (since the 1900s) and the raised level of above-snow erosional features (loss of apical dominance) indicate that increasin g forest density merely exacerbated the rising trend of snowfalls in t he forest studied. This trend, demonstrated earlier in the northern ar eas of the forest-tundra, was not yet documented at the limit of the s outhern boreal forest.