Natural regeneration in Norway spruce and red pine plantations in Dufferin County Ontario - a case study

Abstract

Norway spruce has been demonstrated to be a highly productive species in eastern temperate regions of Canada and is commonly utilized for the afforestation of poor soils. However, literature on the understory regeneration and management of mature Norway spruce plantations in Canada is lacking. Characteristics of natural regeneration were compared under two neighbouring Norway spruce and red pine plantations in southern Ontario. Regeneration counted at plots found large quantities of Norway spruce regeneration which was the dominant species of regeneration at both Norway spruce stands and neighbouring red pine stands. Most of this regeneration was also comprised of saplings greater than 1.3 meters in height. All stands had natural regeneration from outside stands, however regeneration at red pine stands was more diversified, especially in smaller height categories. Average diameters of different species were more normally dispersed than height, and somewhat related to the understory light intensity. Measurements of light intensity using a spherical densiometer were found to be consistently lower for both stands, and likely related to the abundance of tall regeneration instead of the overstory density. One-way analysis of variance (ANOVA) found no significant differences for all parameters between stand types (red pine and Norway spruce), although this was potentially in part due to small sample sizes (n= 8 for most measures). These findings suggest some potential of Norway spruce as an invasive species, however further study is required to make this claim. A review of the European literature on the topics of Norway spruce regeneration and Norway spruce stand conversion suggests Norway spruce exhibits intermediate levels of shade tolerance regenerating best in large gaps and is capable of being outcompeted by shade-tolerant species at low-light environments. Practitioners managing similar stands should target small canopy gaps and should anticipate the potential of the species to regenerate very intensively in large gaps compared to native spruce species.