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The influence of salal on planted hemlock and cedar saplings on northern Vancouver Island Fraser, Lauchlan


Through correlation analyses between 2- and 4-year-old conifer performance (western hemlock (Tsuga heterophylla (Raf.) Sarg.) and western red cedar (Thujaplicata Donn ex D. Don)) and salal (Gaultheria shallon Pursh) leaf area index, and the effect of salal leaf area index on the 2-year growth increment of western red cedar andwestern hemlock, this study determines the influence of salal on poorly growing western red cedar and western hemlock plantations growing on clear-cut and burned old-growth western red cedar and western hemlock stands in the Coastal Western Hemlock biogeoclimatic zone. This study was set up on a pre-existing experimental site involving 8 site x treatment combinations: 2 sites (cedar-hemlock and hemlock-fir) and 4 treatments (control, fertilized, scarified, and fertilized plus scarified). It is shown that increasing salal leaf area index reduces the growth of western hemlock more than western red cedar. When growing with western hemlock, it is inferred that salal is strongly competitive in control plots on CH sites, fertilized plots on CH sites, control plots on HA sites, and fertilized plots on HA sites. When growing with cedar, it is inferred that salal is wealdy competitive on fertilized plots on CH sites,and control plots on HA sites. However, the negative influence of salal on western red cedar only occurred on 2-year-old trees, not 4-year-old trees, suggesting that the influence is waning. For hemlock, the opposite occurred. It is concluded that scarification is the best way to reduce the influence of salal on western hemlock and western red cedar.

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