Roots in Fire

In the last couple of years, my community in Northern Manitoba has been threatened by close forest fires. This made me wonder how forest fires affect soil and plant growth. In the summer of 2025, I collected soil samples from three fire areas just north of my house. After collecting soil in the burnt areas, I collected not burnt soil samples from just outside the burnt areas to compare soil composition. After testing the soil samples from each area, I observed bean plants grow in each soil for 8 weeks. The plants in the Norris Lake burnt area grew the tallest. This forest fire happened 17 years ago, and I think it grew better than other burnt areas because the soil has had a longer time to recover and release nutrients back into the soil. It is important to study plant growth in forest fire areas as the occurrence of fires becomes more frequent.

Weather patterns have been changing across the world and Grand Rapids, Manitoba, like other places, has been more at risk of forest fires and increased frequency of fires. Grand Rapids has a large Indigenous population and hunting and fishing is very much a part of the culture. With the increased frequency of forest fires, it made me wonder what effect forest fires have on the soil and plant growth. This plant growth is necessary to support our wildlife which in turn supports the culture of our community. Back in 2008, there was a large fire 52 km from my home. It was located at Norris Lake and it burnt the largest area of my three burnt soil sample areas burning approximately 53 000 hectares. I also had a fire in 2023 just 17 km north of my house at Ochre Lake; this fire burnt approximately 22 000 hectares. Most recently in 2025, a forest fire 12 km north of my house at Footprint Lake, burnt approximately 12 000 hectares. I travelled to each fire area to collect soil samples in the burnt area and just outside the burnt areas. By comparing soil from the same area that was burnt and not burnt and looking at the effects of plant growth and soil composition, a better understanding of the effects of forest fires on plant growth can be made.

In the summer of 2025, I travelled to the three forest fire locations north of my hometown (Grand Rapids, MB) to collect soil samples. Half a kilometre into the burnt area a soil sample for each fire spot was collected and half a kilometre just outside of each burnt area a soil sample was collected for comparison. All soil samples were labelled and kept separate from each other. To test soil composition, I used a soil test kit which measured pH levels, phosphorus levels, potash levels and nitrogen levels before plants were grown. To compare plant growth, I used a cup of soil from each area (3 burnt and 3 not burnt) and grew bean plants. All growing variables stayed the same (amount of water, amount of sunlight/growing light, soil sample size) and the only changing variable was the type of soil. I compared the growth and number of leaves of three plant samples from each burnt/not burnt area totalling 18 bean plant samples over a period of 8 weeks.

Overall, the plants grown in the Norris Lake burnt soil grew the highest of all burnt soils. At Norris Lake the soil composition showed that potash levels for the burnt and not burnt soil at Norris Lake were higher than any other soil samples. Norris Lake had the lowest phosphorus levels of all soil samples. Norris Lake also showed the lowest pH levels in the burnt soil area.

Ochre Lake not burnt soil plants grew taller than the burnt soil plants but had the same number of leaves as the burnt soil plants. The Footprint Lake not burnt soil plants grew higher than the burnt soil plants in height and number of leaves. Both the Ochre Lake burnt soil, and the Footprint burnt soil showed the highest levels of Nitrogen among all samples. For both Footprint Lake and Ochre Lake burnt soil samples the pH level was slightly higher than the not burnt soil samples.

I think the Norris Lake burnt soil grew higher plants because it has had time to release nutrients back into the soil as the fire happened 18 years ago; whereas the Footprint Lake fire was the most recently burnt soil happening only a few months prior.  During my experiment I noticed that many of the leaves of the bean plants started to turn yellow around 7 weeks of growth. I wonder if the yellowing leaves are due to a lack of nitrogen in the soil because nitrogen helps with chlorophyll production (the process that makes leaves green). My soil testing shows that nitrogen was lacking across most soil samples. The three nutrients that plants need for growth are nitrogen which promotes leaf growth, phosphorus which promotes root growth and fruit, potash/potassium which helps plants resist disease and stay hardy and ideal pH levels allow roots to absorb nutrients effectively.

Over time, the soil that has been burnt has the ability to support plant growth. As stated in the article The Good: The Beneficial Role of Fire in Landscapes, “Fires consume dead and decaying matter, returning nutrients to the soil, which promotes new plant growth”. The oldest forest fire area that I collected samples from; Norris Lake grew the tallest bean plants of all the burnt areas but when comparing the not burnt areas the Norris Lake area grew the shortest bean plants. The soil in the Norris Lake burnt area had the best growth of any burnt soil area yet the Norris Lake area showed the lowest levels of Nitrogen.  This made me wonder if testing more soil sample sights within the burnt and not burnt areas would help give more conclusive findings in the future. Soil testing composition showed that all Norris Lake soil samples that were tested had a lack of nitrogen, yet they grew the tallest plants. More testing would help complete this puzzle. More soil samples need to be collected, tested and planted with each burnt and not burnt region to have more results for comparison. Likewise testing soil before, during and after plants growth would help a more detailed map of soil composition.

Most soil supported plant growth. During my experiment, after plants developed beans it became harder to keep the bean plants alive/healthy. If I would have had more soil it would have been beneficial to add another sample of bean plants that were fertilized on a weekly basis. Keeping the plants alive longer may have given me a chance to compare and measure the beans that grew in burnt and not burnt soil. To compare soil composition within each burnt and not burnt area, I could have tested multiple areas within each region.

Thanks to my family for helping and driving me to collect soil samples at different fire sites. Special thanks to my mentors, Science Coaches and teachers for guiding me in this process.

Works Cited

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