Sixteen-year survival and growth of red spruce seedlings planted in harvest gaps of partially cut stands

This paper presents the results of a red spruce planting realized under a forest canopy (control) and within harvest gaps of 3 hybrid single-tree and group-selection cuttings described as light, moderate or heavy cut (average gap size: 220±91 m2, 266±123 m2, and 342±85 m2, respectively). A 3-year post-planting mechanical release was applied to half of the planted plots. After 16 years, seedling survival and height were higher in harvest gaps than under canopy, with no difference between gap sizes. The release had positive effects only in some circumstances (e.g., for survival in the smallest gaps, for height in all gap sizes), but overall effects were modest. Survival and growth declined over time, and height/diameter ratio was high. Results suggest that the harvest gaps were likely too small for planted red spruce seedlings in a context of wood production but remain an option to reintroduce the species in the understory. Consequently, another tending treatment would be needed to avoid seedling suppression, increase their robustness and recruitment in the canopy.