Site and soil characteristics related to the incidence of Inonotus tomentosus

Inonotus tomentosus (Fr.) Teng causes Tomentosus root disease in spruce trees throughout the boreal and sub-boreal forests of British Columbia. Site and soil characteristics are related to the incidence of this fungus in wet, cool sub-boreal spruce forests located near prince George, British Columbia. Two-hundred and ninety-six plots, 25.2 m in diameter, were examined to determine the incidence of I. tomentosus, and several sire and soil variables were measured. These included soil moisture and nutrient regime, slope position, soil texture, soil coarseness, humus form, spruce density, tree species composition and soil pH. The incidence of I, tomentosus infection ranged from none to 31% of spruce trees per plot. Significant differences (p < 0.05) in percent infection were found between soil moisture regimes, soil moisture by soil nutrient regimes, and slope position. All of these site and soil variables are used, in British Columbia, to determine a 'site series', which is a site specific ecological classification unit used to determine harvest methods and silviculture prescriptions. The most important site variable influencing disease incidence is suggested to be soil moisture regime as influenced by slope position and soil texture. (C) 1999 Elsevier Science B.V. All rights reserved.