The competitive role of Gaultheria shallon on planted western hemlock and western red cedar saplings on northern Vancouver Island

L. H. Fraser , C. P. Chanway and Roy Turkington Forest Ecology and Management Volume 75, Issues 1-3 , July 1995, Pages 27-39

Abstract The presence of competing vegetation, particularly salal (Gaultheria shallon Pursh), was studied in relation to growth (measured as height and 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 ecosystem type on northern Vancouver Island in British Columbia, Canada. The leaf area indices (LAI) of several non-crop species were both negatively and positively correlated with cedar and hemlock height and root collar diameter, but the abundance of salal was mostly negatively correlated with conifer growth. On control CH, control HA, fertilized CH, and fertilized HA plots, salal LAI accounted for over 31%, 56%, 37%, and 31% respectively, of the variation in conifer growth. Scarification of the soil surface layers reduced the abundance of salal and it appeared 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, fertilization and fertilization plus scarification significantly stimulated cedar growth, particularly when salal cover was sparse. Our results suggest 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 hemlock growth on CH cut-over sites.

Author Keywords: Gaultheria shallon; Salal; Hemlock; Cedar; Competition index