Vegetation Management Improves Early Growth of White Spruce More Than Mechanical Site Preparation Treatments

Abstract

Abstract The Inga Lake trial was one of a series of site preparation trials established in the northern interior of British Columbia during the 1980s to determine effective means of establishing conifer plantations on sites with severe vegetation competition and unfavorable soil conditions. Vegetation control, burned windrows, high-speed mixing, bedding plow, breaking plow, and disk trenching treatments were evaluated on a site with high brush potential, relatively dense soils, and average nutrient availability. This article summarizes impacts of treatments on soil density, soil chemical properties, and tree nutrition 5, 10, and 15 years after treatments and on the growth of planted white spruce (Picea glauca [Moench] Voss) after 15 growing seasons. Mixing, bedding plow, and disk trenching treatments decreased soil density and improved nutrient availability relative to no treatment, and effects were still significant after 15 years. Soil carbon and nitrogen increased substantially over time in treatments where there was a vigorous re-establishment of the plant community after disturbance. Although vegetation control did not improve soil physical or chemical properties relative to no treatment, it ranked among the top four treatments, with burned windrows, mixing, and breaking plow, in terms of white spruce growth after 15 years.