Guest Post by Jacob VanderRoest, 2025-2026 Sustainability Leadership Fellow and Ph.D. Candidate in the Department of Chemistry at Colorado State University 

The 2024 Alexander Mountain Fire was the first wildfire that I ever saw. On July 29^th, 2024, I stood on Colorado State University’s campus and watched billows of smoke emanate from the western foothills. I’m originally from Michigan where wildfire activity is incredibly rare, and wildfires were not a concern at all while growing up. So I was shocked to see a massive plume of smoke streaking across the sky for miles. I was worried about whether the fire-impacted areas would recover and regenerate the vast ponderosa pine forests that stood before the fire. At that moment, I knew that understanding how wildfires impact our ecosystems is imperative.

Wildfires are natural ecosystem disturbances that can be beneficial to adapted environments. Nevertheless, wildfires have become more prevalent during the 21^st century.¹  Within the US, wildfires are burning at hotter temperatures, they are burning are larger areas, and wildfire seasons are becoming longer, too.^1–3 For example, the average wildfire size has increased 4-fold during the 2000s compared to the 1980s through the 1990s.⁴ 2024 was a historically devastating year for wildfires with 3,000 homes destroyed and over 75,000 people evacuated.^5–7 Thus, wildfires can drastically alter our surrounding ecosystems, and it is critical to understand how wildfires influence air-, water-, and soil-quality. Within soil, wildfires can specifically change the soil organic matter: a complex mixture of molecules containing sugars and proteins that serve as food for microbes (such as bacteria and fungi). In a healthy soil, microbes eat the soil organic matter and respire it as carbon dioxide in a similar way to how humans eat sugars and proteins for energy and exhale carbon dioxide.

Our team partnered with the Heart J Center who gave us permission to access burned areas from the Alexander Mountain Fire. We specifically investigated an unburned location near the burned area to use as a reference point as well as a low burn severity area (where the fire was less severe) and a high burn severity area (where the fire was most severe).

At these locations, we measured carbon dioxide respiration using a portable gas analyzer. This instrument features a half-dome made of plastic which is placed on top of the soil. Tubes inserted into the half-dome are connected to our analyzer that directly measures the amount of carbon dioxide being released from the soil.

Our results were very surprising! More carbon dioxide was released from the low burn severity and high burn severity soil samples compared to the unburned soil. These results suggest that there is soil organic matter in burned soil that microbes are readily eating and respiring as carbon dioxide.

Overall, these results are encouraging. The soil burned by the Alexander Mountain Fire likely has active microbes that are eating soil organic matter. Having an active microbial community is essential for soil health and post-fire soil and forest recovery. This study indicates that the forests impacted by the Alexander Mountain Fire may be able to slowly recover. I am continuously studying this system to determine what microbes are in the soil and what specific types of organic matter they are eating.

(1)       Jones, M. W.; Abatzoglou, J. T.; Veraverbeke, S.; Andela, N.; Lasslop, G.; Forkel, M.; Smith, A. J. P.; Burton, C.; Betts, R. A.; Van Der Werf, G. R.; Sitch, S.; Canadell, J. G.; Santín, C.; Kolden, C.; Doerr, S. H.; Le Quéré, C. Global and Regional Trends and Drivers of Fire Under Climate Change. Rev. Geophys. 2022, 60 (3), 1–76. https://doi.org/10.1029/2020rg000726.

(2)       Bowring, S. P. K.; Jones, M. W.; Ciais, P.; Guenet, B.; Abiven, S. Pyrogenic Carbon Decomposition Critical to Resolving Fire’s Role in the Earth System. Nat. Geosci. 2022, 15 (2), 135–142. https://doi.org/10.1038/s41561-021-00892-0.

(3)       Cunningham, C. X.; Williamson, G. J.; Bowman, D. M. J. S. Increasing Frequency and Intensity of the Most Extreme Wildfires on Earth. Nat. Ecol. Evol. 2024, 8, 1420–1425. https://doi.org/10.1038/s41559-024-02452-2.

(4)       Iglesias, V.; Balch, J. K.; Travis, W. R. U.S. Fires Became Larger, More Frequent, and More Widespread in the 2000s. Sci. Adv. 2022, 8 (11), eabc0020. https://doi.org/10.1126/sciadv.abc0020.

(5)       Hoover, K.; Hanson, L. A. Wildfire Statistics. Congr. Res. Serv. 2021, 1-3. https://crsreports.congress.gov.

(6)       Statistics | National Interagency Fire Center. https://www.nifc. gov/fire-information/statistics. Accessed September 15, 2025.

(7)       Kolden, C. A.; Abatzoglou, J. T.; Jones, M. W.; Jain, P. Wildfires in 2024. Nat. Rev. Earth Environ. 2025, 6 (4), 237–239. https://doi.org/10.1038/s43017-025-00663-0.