Development of a competition index for young conifer plantations established on boreal mixedwood sites

Abstract

A competition index was developed, and then used to examine the relationships between perennial competition and plantation performance. Species included were white spruce, black spruce, and jack pine for both over-wintered containers and bare root stock. A total of fifteen four-year-old plantations were used in this study representing a range of soil textures located on boreal mixedwood sites in northern Ontario.Effective canopy cover, derived from vertical hemispherical photographs taken at the base of seedling leaders, provided an accurate estimate of the perennial woody competition affecting seedling diameter growth. Initial seedling size, defined by the stem volume at time of planting, proved to be an important covariate in the analysis.Using the relationship between effective canopy cover and seedling root collar diameter, the following questions regarding vegetation control decision-making were addressed: 1) jack pine was more sensitive to increased levels of competition, 2) over-wintered container stock were more sensitive than their larger bare root counterparts, 3) minimal differences occurred in the pattern of growth response to competition across the range of soil textures studied, and 4) early tending treatments should be concentrated on jack pine plantations or on spruce plantations with an effective canopy cover in excess of 60. Key Words: competition index, hemispherical photographs, boreal plantations, white spruce, black spruce, jack pine, tending guidelines.