Establishment of white spruce and black spruce in Boreal Ontario: Effects of chemical site preparation and post-planting weed control

Five-year results of a field experiment to evaluate the effects of vegetation control either before or after planting on the performance of planted white spruce (Piceaglauca [Moench] Voss) and black spruce (P. mariana [Mill.] B.S.P.) transplants and black spruce containerized seedlings are reported. Annual vegetation control with and without chemical site preparation significantly (P < 0.05) improved height growth, ground-level stem diameter, and health of the planted seedlings. Survival and seedling growth were significantly (P < 0.05) higher with chemical site preparation than with chemical release in August of the year after planting. From the beginning of June to the first half of August, soil temperatures were higher in the plots with no competing vegetation than in the control plots. The difference in temperature reached a maximum of 5 °C at 5 cm of depth and 4 °C at 12 cm of depth. Key words: black spruce, chemical site preparation, glyphosate, growth response, Picea glauca, Picea mariana, release, tending, vegetation management, weed control, white spruce