Introduction

Since the introduction of Roundup® in the early 1970s, glyphosate-based herbicides (GBH) have been frequently used in both agriculture and forestry settings (Henderson et al, 2010; Baylis, 2000). Both industries favor these herbicides as they are cost-effective, broad-spectrum, and degrade relatively quickly in the environment (Baylis, 2000; Botten et al, 2021). The prevalence of Roundup® in agriculture has sparked various scientific studies regarding the long-term environmental impacts of this herbicide. However, there are far fewer studies that focus on the use of GBH within a forestry setting. Similar to Roundup®, Monsanto Company also manufactures the glyphosate-based formulations of Vision® and VisionMax® for use in forestry (Dost, 2003; Botten et al, 2021). Forest managers typically employ these two herbicides because of their non-selective nature, making it easier to control understory vegetation and manage competition in reforested cut-blocks. After harvesting operations are complete, landholders of Forest Management Agreement areas (FMAs) are required by the Alberta government to replant and re-establish the area of land that was cleared. Using GBH improves the establishment of planted conifer seedlings by reducing competition primarily from trembling aspen (Populus tremuloides) and Canadian reedgrass (Calamagrostis canadensis). 

Over the years, frequent questions have been raised regarding the safety of GBH's. Indigenous groups, government, public land users, and other stakeholders have expressed concerns about the long-term effects of glyphosate on ecosystem biodiversity, forest composition, plant species abundance, and human and animal health (Botten et al, 2021; Defarge et al, 2023; Ferreira et al, 2023; Giaccio et al, 2023; Werner et al, 2022). Many hunters, trappers, and gatherers in Alberta have frequently raised concerns about the abundance and quality of traditional plants, as well as the effects of prolonged glyphosate exposure on wildlife (Carnochan & Thomas, 2018; Carnochan, 2019; Brunjes, 2018). Glyphosate is thought to degrade quickly in the environment, either through adsorption to soil particles (Viti et al, 2019) or degradation by soil microbes (Helander et al, 2012), posing little threat to non-target species. However, a recent study done in British Columbia by Botten et al. (2021) revealed that glyphosate residues could still be detected within plant tissues at least one year after initial application, and up to twelve years post-application. These findings have provided evidence that glyphosate remains in the environment for a longer period of time than previously estimated. Climate-related factors have also been shown to influence glyphosate persistence in the environment, causing prolonged retention in northern regions (Botten et al, 2021; Helander, 2012). Colder temperatures and longer winters can hinder the microbial breakdown of glyphosate, potentially leading to its persistence in forestry cut-blocks (Stenrød et al, 2005). 

Although glyphosate residuals can be detected for multiple years after application, the concentrations after one year are generally low (less than 0.02 ppm) (Botten et al, 2021). It is also worth noting that GBH's are typically only applied to harvested blocks once or twice over the course of the rotation period (80-100 years in Alberta), allowing the understory plant species to recover and continue growing once the planted conifers have been established (Figure 1). The minimal residual concentrations and infrequent number of applications to a cut-block could suggest that glyphosate has little effect on species composition and diversity in the understory, only acting to delay initial growth. Therefore, the aim of this research project was to quantify glyphosate residues within multiple natural subregions of Alberta to determine how differing climatic regions impact persistence, and to determine if the operational application of GBH to forest cut-blocks impacts the species diversity and composition of culturally significant plant species. 

As mentioned above, the goal of this research project was to quantify glyphosate residues in multiple natural subregions of Alberta, as well as to see if the operational application of GBH to forest cut-blocks affects the species diversity and composition of culturally significant species. More specifically, my research objectives are as follows: 

1) Analyze glyphosate residuals over a two-year period in multiple natural subregions across Alberta to determine if there is a significant difference in persistence based on climatic region. 

2) Compare untreated cut-blocks to treated cut-blocks in multiple natural subregions to determine how plant species diversity and community composition of culturally important species respond to glyphosate application.