Range-Wide Genetic Variation in Port-Orford-Cedar (Cupressaceae, Chamaecyparis lawsoniana)

Abstract

Timing of height growth was determined for 54 families of seedlings of Chamaecyparis lawsoniana, Port-Orford-cedar, which represented most of its natural range. Seedlings were grown in plant beds in inland and coastal nurseries. The proportion of early-season growth declined and the proportion of late-season growth increased with changes in seed source location from high to low elevations, from south to north, and from east to west. This pattern was parallel to that of seedling height and of actual elongation in each of three periods during the growing season. The tallest trees (from the Oregon coast near the species' northern range limit) grew more in each period but had the greatest proportion of late-season height growth. Planting such genotypes where late summer drought or early fall frost are common may threaten their survival. Use of breeding zones that limit genotype transfer distance may avoid such damage. Within breeding zones, height growth of families was not related to their prior screening for disease resistance; selection for disease resistance should not affect growth rate or pattern. Seedlings grown at the coastal nursery had a lower proportion of early-season growth and more in late season than seedlings grown inland.