Methods

All openings selected for this study fall within one of West Fraser Timber Co. Ltd.'s FMA's, including, Blue Ridge, Manning, Hinton, Edson, and Sundre. The sites chosen for this study were operationally treated with herbicide in 2021, and plots were established for measurements during the summer of 2022. Twenty-five treated cut blocks were selected for plot establishment and vegetation sampling (Figure 2). Sample sites were chosen based on road access and spatial variability within and across West Fraser FMA's throughout western Alberta to include sites from multiple natural subregions. The criteria for selecting appropriate sites are as follows:

• Clearcuts that were replanted (either lodgepole pine or white spruce)

• Less than 10 years old

• Sprayed with herbicide by helicopter (all sites were sprayed in 2021)

• Sprayed for stand-tending purposes (competition control)

During the summer of 2023, an additional 13 sites were added to establish sampling plots in untreated cut blocks (Figure 2). These sites were included later in the study because untreated cut-block data from West Fraser were not available at the start of the sampling period in 2022. Due to the limited availability of untreated cut-block data, the majority of new sites were located in the upper and lower foothills subregions (Table 2). To ensure that plant community composition was similar, untreated sites were chosen based on their proximity to treated sites as well as similarity in age. These plots were used to record plant community data prior to herbicide treatment. The sites were then treated with herbicide in August of 2023, and will be re-measured in July 2024 to record post-treatment data (Table 1).  

Throughout each of the selected openings, 10 sampling plots were established. These plots were distributed in a grid pattern across the cut block based on area in order to cover as much of the sampling area as possible (Figure 4). An opening of up to 5 ha had plots spaced 50 m apart. Openings between 5-10 ha had plots spaced 75 m apart, and any openings greater than 10 ha had plots spaced 100 m apart. Sampling area for each opening was constrained to mesic moisture and nutrient regimes using the provincial Derived Ecosite Phase database (DEP). 

Plots were made up of a series of three nested plots, however, for this study only the 1 m2 quadrat data will be analyzed. Two quadrats were placed within each plot, one to the north and one to the south, both 5.64 m from the plot center (Figure 3). Quadrats were used to record plant community data. Any plant whose base fell within the quadrat was identified to the species level and percent (%) cover was visually estimated for each species. Visual estimation was done using a % cover diagram for quick reference (Figure 5). Quadrats were marked with a minimum of two orange pin flags placed at opposite corners to ensure the same area could be remeasured the following year and any changes in the plant community could be recorded.

A group of 18 plant species of interest were selected for glyphosate analysis (Table 3). These plants were chosen based on their cultural significance and value to humans for foraging and medicinal purposes, as well as frequency of use by animals. Any plants of interest that were identified in the 1 m2 quadrats were then destructively sampled outside of the established plots to prevent disturbing the plot. Only the new shoots of these plants were taken to be analyzed for glyphosate residue.   

At each site, 50-150 g of plant tissue was collected for each species of interest identified. Samples were taken across the entire site and combined into one bag per species. Bags were labeled with species and site number, and stored frozen until they could be sent to the Agriculture and Food lab at the University of Guelph to be analyzed for glyphosate residue. Samples were collected one year and two years after treatment to assess any changes in persistent residue.