Grant: CCI Applied Research and Development Grants

Actively managing competing vegetation in young reforestation sites is a silvicultural tool used to improve rates of growth and survivability of planted conifer seedlings. There are a range of potential site and seedling-scale treatments that may be used, and many tested in various ways over the decades. Despite the history of mechanical site preparation and numerous studies on the topic, there remain knowledge gaps in terms of the relationship between historical management approaches and current utilization of these approaches. This is particularly relevant for operators that have leaned heavily on glyphosate-based solutions for last 20+ years and often with limited use of mechanical tools; for many operators, there are strong paradigm shifts and corporate decisions being made with respect to use of glyphosate and in some cases, it is being broadly discontinued. Further – fewer studies have reconciled the potential benefits or trade-offs, in the same investigation, with respect to managing tree productivity and other forest values, such as biodiversity. This project is located within Weyerhaeuser Grande Prairie’s operating forest management area in Alberta. Weyerhaeuser has recently discontinued the use of glyphosate company-wide – this has prompted silviculture staff to explore alternative tools. Ultimately, the proposed study is intended to provide quantitative data that will allow for informed decision making when implementing site treatments and seedling stock for reforestation as there will be trade-offs when managing for multiple forest values and with due consideration for stakeholder and societal concerns on the operating land base. We will test four mechanical site preparation treatments that range in the intensity of disturbance. These treatments will be examined with and without the use of a pre-planting herbicide treatment (Imazypyr). Until recently, Imazypyr was not available for broad cast deployment; this study will provide well-replicated quantitative evidence on where the best-use case is for this treatment versus where mechanical site preparation alone will be sufficient in managing competing vegetation. We will also explore the use of large container stock as an alternative to intensive site preparation in a seedling-scale trial. We aim to collect comprehensive data examining these treatments under the lens of their ability to enhance conifer seedling survival and growth and to restore or enhance plant and arthropod biodiversity.