Patterns of optimal growth for white spruce provenances in Alberta

This paper describes the pattern of genetic variation for growth potential among white spruce provenances in Alberta, Canada. It uses total height (H27) and diameter at breast height (D27) at 27-yrs from seed to identify provenance differences in relation to latitude and elevation of seed origin. Latitude and elevation are the main variables that adequately describe climatic variability in Alberta. Indirectly, latitude also describes regional variation in day length. Climate and day length are the main natural selection pressures governing genetic differentiation among forest tree populations. The regressions of height and diameter on latitude and elevation of seed origin are used to predict the locaiton from which provenances of the highest growth potential on a specified site or environment are expected to originate. This locaiton is referred to as an optimum seed source. By examining the pattern of provenance variation on similar sites and the correlation of provenance ranks among sites (genotype by environment interaction), it is possible to establish seed transfer guidelines that will enhance efficient use of seed while maintaining provenance climatic adaptation.