Inhibition of Abies concolor Radicle Growth by Extracts of Ceanothus velutinus

Ceanothus velutinus Dougl. ex Hook is a major shrub species that invades recently burned areas and clearcuts at middle elevations in the Sierra Nevada, California, where it competes strongly with natural and planted conifer seedlings. Establishment of natural Abies concolor (Gord. & Glend.) Lindl. seedlings in brush fields with a high cover of Ceanothus velutinus is frequently spotty, and many established seedlings appear somewhat unhealthy for several years. The earlier study by Conard and Radosevich was concerned primarily with competitive interactions. Chemical (allelopathic) effects, however, are also a possible partial explanation for reduced growth of conifers in the presence of Ceanothus velutinus . To investigate this possibility, the authors conducted a series of laboratory and growth chamber experiments.