Effects of stock type and site preparation on growth to crown closure of white spruce and lodgepole pine

Abstract

Growth of white spruce (Piceaglauca (Moench) Voss) and lodgepole pine (Pinuscontorta Dougl.) seedlings was studied on six installations, each containing different stock types and site-preparation treatments. Stock types included styroplugs from different cavity sizes, bare-root stock, and transplant stock; site preparations included no treatment, scalping, inverting, and mixing. Fertilizer was also used in combination with some of these treatments on some installations. Site-preparation treatments that gave some degree of vegetation control generally led to higher growth rates, but there was considerable variability among and within installations. The slope of the linear relationship of height versus age up to 10 years gave an estimate of early growth which was suitable for comparing treatments, whereas average height increment in a later measurement period gave a better estimate of growth for projection purposes. A normal distribution of growth rates around a mean for a particular stock type and site-preparation method was used in conjunction with height–dbh and crown width–dbh relationships to project growth of trees to crown closure, assuming different densities. The age at crown closure depended on both growth rate and density, and average size at crown closure depended primarily on density.