Cumulative Impact of Biotic and Abiotic Damage Agents on Lodgepole Pine Tree Form and Stand Structure in Southern British Columbia

Abstract

Not all pests kill trees or compromise final tree form; however, the cumulative effect of one or more damage agents over time can significantly limit final expectations at harvest, severely reducing or compromising wood quality and timber supply expectations going forward. This study highlights the effects of damage agents on young lodgepole pine insouthern British Columbia during the formative years of stand development. Over 4,300ntrees were monitored for up to three decades with over 40 damage agents recorded, causing significant repercussions on stocking, health, and form of potential crop trees. By the final assessment, density of potential crop trees had declined dramatically, with 84% affectedby one or more pests, and 63% of natural ingress dead. Most natural ingress was severely suppressed; thus, it is unlikely to fill in stand gaps caused by mortality and damage agents affecting larger potential crop trees. Lodgepole pine terminal weevil and western gall rust were the predominant damage agents influencing form and quality of potential crop trees. Lodgepole pine terminal weevil attacked up to 73% of pine and over 24% suffered multiple attacks. Results from this study emphasize the need for more short- and long-term monitoring of young stands to inform the development of forest policy and promote healthy, resilient new forests. KEYWORDS: lodgepole pine, damage agents, lodgepole pine terminal weevil, western gall rust, Southern British Columbia