LAUSR

Abstract Advanced regeneration of black spruce and white spruce are common in lodgepole pine dominated stands of Alberta. These economically important species have the potential to replace lodgepole pine trees that are killed by mountain pine beetle (MPB). The growth responses of both species of spruce after overstory lodepole pine mortality were examined using data collected from seven sites in the lower foothills of western Alberta, Canada. We sampled understory black and white spruce (>1.3 m in height) and characterize competitive effect of surrounding trees on growth response. Diameter and height growth responses of both species were affected positively by overstory pine mortality with white spruce having a shorter delay in release response than black spruce. While higher mean growth responses were observed for white spruce, both species of spruce increased in growth as initial tree size and understory light increases. Spruce/fir competition around the focal trees resulted in increased height growth and a reduction in diameter growth of both spruces. Overall, our results demonstrate that advance regeneration of both species of spruce can increase in growth and potentially replace pine in the canopy that have been lost to MPB.