Seed Rain and Seedling Establishment of Picea glauca and Abies balsamea after Partial Cutting in Plantations and Natural Stands

The conditions for natural regeneration of white spruce (Picea glauca) and balsam fir (Abies balsamea) in 12 natural stands and five plantations containing both species were investigated 9 to 30 years after partial cutting. We estimated seed input on the ground, measured light reaching the understory, and recorded the presence and age of seedlings smaller than 150 cm in height on six different substrates: mineral soil, moss, rotten wood, litterfall, herbaceous, and dead wood. Partial cutting generally prompted the establishment and growth of seedlings. The number of fir and spruce seedlings is always greater in natural stands than in plantations, a trend likely associated with the reduced abundance of suitable substrate for establishment in the latter. White spruce is significantly associated to rotten wood while fir settles on all types of substrates that cover at least 10% of the forest floor. There is a strong relationship between light intensity and the median height of spruce seedlings, but this relationship is non-significant for fir. Seedlings of both species can survive at incident light intensities as low as 3%, but an intensity of 15% or more seems to offer the best growth conditions. The results of this study provide guidelines for successful forest regeneration following partial cuts in spruce-fir stands.