STROBILUS PRODUCTION AND GROWTH OF PACIFIC YEW UNDER A RANGE OF OVERSTORY CONDITIONS IN WESTERN OREGON

Strobilus production, growth, and morphology of Pacific yew (Taxus bre vifolia Nutt.) were examined at three sites in the Cascade Mountains a nd one site in the Willamette Valley of western Oregon. Strobilus prod uction on branch segments was positively associated with overstory ope nness for male and female trees at all four sites over 2 years. Strobi lus production was also associated with branch vigor, but not as consi stently as with overstory. Other variables, including tree size and ag e, mass of branches, branch bifurcations, and potential radiation, fai led to explain significant variation in strobilus production. Overstor y openness was also correlated with 5-year growth increment for all tr ees and with mass of 1994 branch growth for female trees, suggesting t hat tree vigor increased with overstory openness. In addition, branch mass and the number of branch bifurcations were positively associated with overstory openness.