Persistence of suppression effects on peatland black spruce advance regeneration after overstory removal

The persistence of suppression effects on peatland black spruce (Picea mariana (Mill.) BSP) advance regeneration following overstory removal was examined (i) by analyzing post-harvest growth patterns and (ii) by comparing observed post-harvest growth with predictions from an individual-tree growth model. Analysis of growth patterns revealed critical points (inflections or maxima) in annual basal area, diameter, and height growth series, and in specific volume increment. Critical points occurred at different times (ranging from 1 to 29 years after harvest) for different variables and often occurred earlier for trees with greater height at time of harvest. These critical points do not necessarily coincide with the cessation of persisting suppression, however, since postharvest growth patterns also reflect current influences on growth. The comparison of observed basal area and diameter growth with model predictions isolated persisting suppression effects. The effects of suppression on basal area and diameter growth decline linearly with time since harvest and become negligible 12 years after harvest. The persistence of suppression effects on basal area and diameter growth is largely independent of the height of the tree at the time of harvest.