White spruce growth to age 44 in a provenance test at the Petawawa Research Forest

Twenty-five provenances of white spruce were planted in 1963 in 144-tree plots and three replications as part of a provenance test series for eastern Canada. The experiment was well maintained and thinned to 50% of its original stocking in 1986 (age 26 years from seed). Measurements at age 44 were subjected to analyses of variance and correlation and compared with height and survival at age 15. The results demonstrated that at age 15, identification of the best provenances is ineffective because of changes in rank and the late expression of survival differences. At age 44, significant differences among provenances were observed for survival, mean height, diameter, basal area, and volume. The greatest volume was produced by a provenance from Cushing in the Ottawa Valley in Quebec, 287 m(3) per ha, which was 11% greater than the volume of the local provenance, Chalk River, Ontario. When ranked on the basis of survival and volume, the best eight provenances included five from Quebec, and one each from New Brunswick, Ontario, and Wisconsin. The experiment shows that at the appropriate stage in a selection program, large plots can yield significant results, which has important implications for the design of experiments.