THE COMPETITIVE ROLE OF GAULTHERIA SHALLON ON PLANTED WESTERN HEMLOCKAND WESTERN RED CEDAR SAPLINGS ON NORTHERN VANCOUVER-ISLAND

The presence of competing vegetation, particularly salal (Gaultherin s hallon Pursh), was studied in relation to growth (measured as height a nd root collar diameter) of western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western red cedar (Thuja plicata Donn) saplings planted in cedar-hemlock (CH) and hemlock-amabilis fir (HA) phases of an ecosyst em type on northern Vancouver Island in British Columbia, Canada. The leaf area indices (LAI) of several non-crop species were both negative ly and positively correlated with cedar and hemlock height and root co llar diameter, but the abundance of salal was mostly negatively correl ated with conifer growth. On control CH, control HA, fertilized CH, an d fertilized HA plots, salal LAI accounted for over 31%, 56%, 37%, and 31% respectively, of the variation in conifer growth. Scarification o f the soil surface layers reduced the abundance of salal and it appear ed to reduce the influence of salal on hemlock growth, perhaps because salal had only recently established on these sites. There was little evidence of a competitive effect of salal on cedar. However, fertiliza tion and fertilization plus scarification significantly stimulated ced ar growth, particularly when salal cover was sparse. Our results sugge st that salal may compete with western hemlock, and to a lesser extent western red cedar, and that it may be an important cause of poor heml ock growth on CH cut-over sites.