Genetic variation and productivity of Populus trichocarpa and its hybrids. V: The influence of ramet position on 3-year growth variables

A 3-year study was conducted on the effects of different stem positions (from which cuttings were taken on a stool-bed ortet) on sprouting characteristics and stem growth of Populustrichocarpa Torr. & Gray. In 1986 ramets were collected from five stem positions, evenly distributed from the base to the tip, on three stool-bed ortets of each of 30 clones representing three river valleys in western Washington. Each set of five was planted at 1.22-m spacing in one of three adjacent blocks in an experimental field in Puyallup, Washington. First-year results showed that cuttings from the upper two positions tended to leaf out earlier and develop a single rather than multiple stem as compared with those from the lower positions. Analyses of variance of growth traits showed significant position, position–river, and position–clone within river interaction effects. Positional effects on sprouting and growth were strong primarily for material from the Dungeness River. At the end of the 3rd year, the largest Dungeness ramets (from position 2 near the top) averaged 860 cm in height and 7.3 cm in diameter, whereas the smallest (from position 4) averaged 753 and 5.8 cm, respectively. By this time, it appeared that the shorter trees had begun to suffer from competition associated with crown closure. Thus, the impact of competition in a tightly spaced, multiclonal plantation can influence the ultimate growth and survival of different clones and thereby bias a genetic evaluation.