Living without herbicides in Québec (Canada): historical context, current strategy, research and challenges in forest vegetation management

Abstract

Vegetation management is crucial to meeting the objectives of forest plantations. Following public hearing processes, chemical herbicides were banned on Crown forest lands in Québec (Canada) in 2001. Release now mainly relies on mechanical treatments. Our objectives are to review the historical context and the research conducted over the past 15 years that has led to the province's current vegetation management strategy and to identify the major challenges of vegetation management being faced in Québec in the context of intensive silviculture and ecosystem-based management. Research has led to an integrated management model without herbicides, adapted to the ecological characteristics of reforestation sites. The Québec experience illustrates how, on most sites, vegetation management that is based on early reforestation, the use of tall planting stock and intensive mechanical release brings crop trees to the free-to-grow stage without the use of herbicides and without resulting in major effects on vegetation diversity. This vegetation management strategy is an asset in the implementation of ecosystem-based management. However, research demonstrates that mechanical release alone does not promote optimal crop-tree growth, due to rapid resprouting or suckering of competitors and competition from herbaceous species. Therefore, the current strategy poses important challenges in the management of plantations where the objective is to maximise wood production.

Benefit–cost Analysis of Vegetation Management Alternatives: An Ontario Case Study

“…However, in some scenarios a single cutting operation may not be sufficient to suppress the competition (MacDonald andFiddler 1993, Heineman et al 2005) and repeated cutting operations are not cost-effective (Comeau and Harper 2009). Although job creation was a major goal of implementing these labour-intensive methods on a large scale, companies now frequently report a shortage of available (willing) workers to carry out mechanical release treatments (Thiffault and Roy 2010;Wyatt et al 2011). Risks of gasoline and oil spillage, and inhalation of exhaust emissions from brush saws pose potential environmental and health risks (Dubeau et al 2003).…”

“…To deal with these challenges, in Quebec, four alternative strategies are being implemented. These are: preventive silviculture and natural regeneration, mechanical site preparation, early planting of size-adapted stock, and use of mechanical release where and when needed (Thiffault and Roy 2010). The common alternative to herbicides is cutting either by motor-manual or mechanical means (Wiensczyk et al 2011).…”

Scenario analysis of planting density and pre-commercial thinning: will the mixed forest have a chance?

“…Early tending, such as various PCT methods, usually show a positive response for the future yield of target tree species (Johansson 1996;Bokalo et al 2007;Rytter and Werner 2007;Thiffault and Roy 2011;Uotila and Saksa 2014). In general, PCT could also have a long-term impact on the ground vegetation cover since high stocking is a severe limitation due to the reduction in light to the ground and the stocking is more important than the canopy species composition per se.…”

Early performance of planted hybrid larch: effects of mechanical site preparation and planting depth

“…Indeed, a reduced vegetation cover tends to increase resource availability to the newly planted seedlings (Walstad and Kuch 1987). In contexts where the use of chemical herbicides is restricted such as in Québec, Canada (Thiffault and Roy 2011), intensive site preparation can help reduce the need for repeated and expensive manual tending treatments that are used to manage competing vegetation after plantation establishment (Gagné and Paquette 2008). However, non-crop vegetation can also enhance seedling growth and survival under some conditions (Holmgren et al 1997;Brooker et al 2008;Bruno et al 2003).…”