Growth and nutrional status of black spruce layers, natural seedlings and planted seedlings following sacrification - Results after 10 years

Careful logging around advance growth (CLAAG) and tree planting following site preparation or not (fill planting),are widely used to regenerate black spruce (Picea mariana (Mill.) BSP) stands in the boreal forest of Quebec, Canada. However, few mid-term studies have compared these different regeneration modes. In this study, we examined height growth and nutrient status of black spruce layers, natural seedlings, and planted seedlings over a 10-year period, in an experimental design combining CLAAG, natural seeding, planting, and two types of scarification (cones and disks). Without scarification, growth of planted seedlings (5.8 cm-year(-1)) was slightly greater than that of layers (4.4 cm-year(-1)) and natural seedlings (4.1 cm-year(-1)). Scarification improved growth of the three types of regeneration, but the treatment was more beneficial for planted seedlings (+7.1 cm-year(-1)) than for natural seedlings (+1.6 cm-year(-1)) and layers (+1,0 cm-year(-1)). Five years after treatment, scarification had increased the current-year needle N concentration of the three types of regeneration, but this beneficial effect on N was still detectable only in foliage of layers after 10 years. The effect of the treatment was variable for P and K contents, for which natural regeneration seems to have taken advantage more than plants. Our results indicate that scarification can improve the initial growth and nutrient status of both natural and artificial regeneration of black spruce and thus accelerate site recovery after cutting in the boreal forest. Furthermore, fill planting without site preparation appeared to be clearly less efficient than planting combined with scarification.