Causes and amelioration of nutrient deficiencies in cutovers of cedar-hemlock forests in coastal British Columbia

Poor growth of conifer regeneration occurred on sites formerly occupied by old-growth cedar-hemlock (CH) forests in coastal British Columbia, 5–8 years after clearcutting and slashburning. Symptoms included chlorotic foliage and growth check of Sitka spruce, western hemlock, western red cedar and amabilis fir, coincident with the expansion of the ericaceous shrub, salal, on the cutovers. Fertilization trials identified N and P deficiencies as the cause of the growth check of conifers, and additions of 300 kg N ha−1 and 100 kg P ha−1 significantly improved tree growth rates. Equivalent growth responses were achieved with additions of sewage sludge and fish silage. Burning, cultivating, liming, higher planting densities or herbicide application, were less effective in promoting conifer growth. The nutrient deficiencies in conifers on CH cutovers were the result of two factors: low nutrient availability in soil and humus, and competition and interference from salal. Salal immobilized substantial amounts of N...