Comparing Disturbance Regimes

USING DENDROCHRONOLOGICAL TECHNIQUES, historical fire regimes and outbreaks of western spruce budworm (Choristoneura occidentalis Freeman) were characterized within a dry mixed-conifer forest to assess whether the current disturbances are outside the historical range of variation. Over the past several centuries, western spruce budworm outbreaks were consistent and occurred approximately every 30 years. In contrast, mixed-severity fires occurred approximately every 15 years until the middle of the last century, and then stopped – as a likely consequence of modern fire suppression efforts. The lack of low- and moderate-severity fires has facilitated increased canopy cover and continuity, and accumulations of ladder and surfaces fuels leaving the forest at increased risk of a high-severity stand-replacing fires.