Differences in physiology and growth between coastal and inland varieties of Douglas-fir seedlings in a common garden

In a common garden study, seedlings of Pseudotsuga menziesii (Douglas-fir) var. menziesii (coastal) from Lacomb, Oregon and P. menzeisii var. glauca (interior) from Clearwater National Forest, Idaho, and their F2 hybrids were grown in nursery beds in the coastal climate near Corvallis, OR. The coastal variety was from an elevation of 245 m with a mean annual rainfall of 1400 mm. The interior variety was from an elevation of 871 m and a mean annual rainfall of 600 mm. Height, stem diameter, and bud burst percent were determined. Metabolic heat rate and respiration rate were measured on apical meristems at 30, 35, and 40 °C. Similar tissue was dried, ground, combusted, and analyzed for carbon isotope ratios. The two varieties differed from one another in growth traits, bud burst, carbon isotope ratios, and respiration traits. The F2 hybrid progeny of the varieties had isotope ratios similar to the interior variety, but respiration traits of the hybrids were similar to the coastal variety. Respiratory heat rate and height growth were the only significant trait differences found between families within varieties. The faster growing coastal variety showed less carbon isotope discrimination relative to the slower growing and more stressed (when grown at Corvallis) interior variety.