Adaptive variation in jack pine from north central Ontario determined by short-term common garden tests

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To improve our understanding of adaptive variation in jack pine, Pinusbanksiana Lamb., from north central Ontario, 64 seed sources were grown in three common garden tests, and relationships were determined between seedling performance and environment at seed origin. Twenty-three growth and phenological variables were studied, including seedling heights, needle flushing dates, timing of shoot elongation, fall foliage colour change, and drought survival. Significant components of variation were expressed among seed sources for all growth traits and many phenological characters. Linear regressions were run between seedling traits and climatic variables as well as spatial, soil, and vegetative variables that described the environment at seed origin. Resulting coefficients of determination were as high as 0.30. Principal component analysis was used to summarize the variation, with 33% and 21% of the variation accounted for by the first and second components, respectively. Regressions and mapping of principal component analysis scores indicated that the patterns of variation in this portion of the range of jack pine were clinal in nature; the patterns could be predicted by environment at seed origin. The greater growth potential of seedlings from the southwestern portion of the range, in contrast with those of the north shore of Lake Superior, reflected clinal trends seen in previous studies. Multiple regressions were run on the first and second sets of factor scores produced from principal component analysis against the climate variables, resulting in coefficients of determination of 0.30 and 0.38, respectively. Including soil and vegetative variables in the models resulted in only slightly higher coefficients. Thus, climate at seed origin should be considered as the prime factor when seed transfers are necessary in this area.