Pacific yew (Taxus brevifolia Nutt.) growth and site factors in western Oregon

Conservation biologists in the Pacific Northwest have recently turned their attention to Pacific yew (Taxus brevifolia Nutt.), given past harvest of t his species for taxol and the fragmentation of late-successional forested l andscapes. Understanding yew growth and reproduction patterns is important given interest in the long-term viability of yew populations and important contributions this species makes to stand structure. Our research, based on data from 11 intensively measured 2-ha plots, confirms and quantifies some early qualitative observations of yew tree size and age distributions in t hree forested subregions of western Oregon. These distributions show a gene ral lack of regeneration in the last century which should be of some concer n to land managers given Pacific yew's contribution to late-successional st and structure. Although correlations between size measurements, for example between diameter and height, are strong (coefficients > 0.61 across all pl ots) and consistently positive, correlations between size and site variable s (e.g., aspect) are weaker (coefficients < 0.41 across all plots) and inco nsistent. Most plots demonstrated a weak but consistent relationship betwee n size and age, and yew tree size and age distributions were relatively con sistent within subregions. However, there were substantial differences in d iameter growth rates among subregions.