Growth and Morphology Differ between Wind-Exposed Families of Sorbus Aucuparia (L.)
Arne Sæbø and Øystein Johnsen
Abstract: Rowan (Sorbus aucuparia), a small and decorative tree with widespread distribution throughout Norway and Europe, is well suited for growth on street verges, parks, and urban woodlands. With a better knowledge of the genetic variation of its important traits, good genotypes could be selected and the appearance of the trees thus improved. The objective of this study was to describe the variation in growth, morphology, and phenology of rowan between and within seed sources and at different wind exposures. Seeds were collected from 10 to 15 trees within each of six populations in a small area of 1,300 km2 (500 mi2) along the southwestern coast of Norway. Three populations were wind-exposed and three were sheltered. From each of the 78 mother trees included, 30 half-siblings were planted in the field at the Sserheim Research Centre (58.8°N, 5.5CE). Height growth, stem diameter, number of stems and branches, branch angle, and growth start and termination were recorded annually in five successive years. Large differences in most traits (estimated heritabilities varied from 0.14 to 1.0) were found among families within the stands. However, no important differences could be observed between progenies from wind-exposed trees and those from sheltered trees, and differences among stands were only minor. The results are discussed in relation to the climatic adaptation of rowan and how this plant material can be used in urban settings.
Keywords: Growth; morphology; phenology; seed source; selection; Sorbus.