Figure 2.

Principal component analysis (PCA) based on 11 selected variables characterizing the climate of origin (1961–1990 normals) for 340 Picea rubens seed families used in this study. The common garden sites are also plotted based on the selected climate variables for 2019 (triangles) and 2020 (circles). Selected climate variables are chilling degree-days (DD_0), heating degree days (DD18), mean annual solar radiation (MAR) in MJ m⁻² d⁻¹, precipitation as snow (PAS) in mm, May to September precipitation (MSP) in mm, per cent mean annual relative humidity (RH), extreme maximum temperature (EXT) over 30 years in °C, Hargreaves climatic moisture deficit (CMD) in mm, continentality (TD) in °C, day of the year on which frost-free period ends (eFFP) and annual potential evapotranspiration (PET) in mm.