Variation in wood structure of white fir along an elevational transect.

Several wood structural characteristics were measured in 15-year-old Abiesconcolor (white fir) from four populations along an elevational transect in the central Sierra Nevada region. The trees had been growing in a plantation near Placerville, California. Growth rings were narrower at breast height, latewood percentage tended to be greater, and tracheids were shorter in trees from higher elevation populations. Proportion of family variance components was greater than population for specific gravity and spiral grain angle. The characteristics that showed greatest population components of variation would be largely determined by durations and rates of shoot and radial growth. Presumably, length of the growing season would exert stronger selection pressure on these variables than on other characteristics of wood structure.