Study Site & Methodology

Study Site

Map of Canada's boreal forest range. Image curtesy of Natural Resources Canada 2025

Boreal Forest

Being the second most northern biome, the boreal zone encompasses one of the largest biogeoclimatic areas and features many different habitats within it, including the boreal forest (Brandt et al 2013). Canada contains 28% of the world’s total boreal biome and makes up 8% of the world's total forests, as the biome extends from the Yukon in the west to Newfoundland and Labrador in the east (Kurz et al 2013; Brandt 2009; Boreal Forest 2025). Given the circumpolar nature of the boreal forest, this biome is primarily inhabited by cold-tolerant tree species in the genera Abies, Larix, Picea, and Pinus, but can also include Populus and Betula in some areas (Brandt et al 2013).

Map of Treatment Blocks

Study Site Near Robb, Alberta, Canada

The study site was first established in 2008 by McIntosh and Macdonald (2013) to test the effects of mountain pine beetle (MPB) within Alberta's forests, by experimentally simulating MPB on lodgepole pine forests. The sites consisted of four treatment plots: a moderate (50% kill) MPB attack, a high level (100% kill) MPB attack, a logged salvage plot; the typical treatment for MPB in Alberta, and an undisrupted control. Each plot was then replicated 3 times in 3 replicate blocks, with 9 sampling points within each treatment plot for a total of 108 individual sampling points. For the MPB attack plots, the effects of MPB on the lodgepole pine trees were simulated with glyphosate herbicide injected into either every third tree (50% kill) or every tree (100% kill). These sites were then sampled for a variety of measures the year before the treatment was applied, the year the treatment was applied, and a year post-treatment.

Methodology

Soil Sample Collection

To collect the samples, a one by one meter quadrate was laid out at the sampling point in a predetermined direction (typically having the corners face the cardinal directions), then soil from each corner was taken. Soil was taken by moving aside any plant matter, then with gloved hand sprayed with 70% ethanol the top most soil was taken, placed in a plastic bag, and mixed together with the other corners of that sampling point in order to best represent the soil of that point. This sampling method was completed at the four corners of each treatment plot in all three replicate blocks, creating 48 soil samples for the 2025 year.

Diagram of Sampling Points

Green rectangle represents one treatment block. Each yellow square is the 1x1 meter quadrat making up one soil sample, with the corners (red dots) being where soil was collected for each sample.

Preparation for Analysis

Before pH analysis, soil samples were first put through a 4 mm sieve to remove any large plant matter or other debris present in the soil.

A 0.01 M CaCl2 solution was created by dissolving 14.7 grams of CaCl2 into 10 liters of water to be used in the analysis of pH. (Kalra and Maynard 1991).

Before sieving

After sieving

Analysis of pH

To analyze the pH of the soil samples, I followed the procedure outlined by Kalra and Maynard (1991) for measuring pH of field-moist organic samples. A saturated paste was created using 10 grams of prepared soil and enough 0.01 M CaCl2 to fully saturate the soil, but not enough where CaCl2 collects on top of the soil. Twenty milliliters of 0.01 M CaCl2 was then added to the soil paste to create a suspension, then stirred roughly every 6 minutes for half an hour. The suspension was allowed to rest for another 30 minutes before the pH was measured using a PASCO pH probe.

Saturated Paste

Stirring Suspensions

Soil Suspensions

Statistical Analysis

For statistical analysis, data points from each treatment were combined together, so that there were four groups of treatment data (control, 50% kill, 100% kill, salvage) for each year sampled. The data was found to be normally distributed and have equal variances, based on Shapiro-Wilk test and Levene’s test respectively. Means for each year within each treatment were then calculated, and a two-way ANOVA was conducted to compare the means from before the treatment, during the treatment, one year post treatment, and sixteen years post treatment. Tukey’s post hoc test was conducted on how year affected treatment pH. All statistical analysis was conducted in R Studio, version 4.5.1.

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