2025 Undergraduate Research Showcase

Burn Severity Impacts on Nutrient Availability Through a Soil Profile From the Wapiti Fire

Document Type

Student Presentation

Presentation Date

4-15-2025

Faculty Sponsor

Dr. Anna Bergstrom and Dr. David Huber

Abstract

Wildfires can cause drastic disturbances in the biogeochemical cycles of the landscapes they affect, altering factors such as soil nutrient availability and water chemistry. The ignition of organic material remineralizes nutrients, making them more available for uptake or transport. However, the exact transformation of nutrients in soils and their potential to be transported to downstream systems can be highly dependent on biota, landscape characteristics, and climate. As a result, this project aims to identify the relationship between burn severity and available nutrient concentrations in soils with high likelihood of being transported to downstream systems. The Wapiti Fire, which primarily burned in the watershed of the South Fork Payette River, burned from July to mid-October 2024. We collected surface and subsurface soil samples from within the burn as well as control samples from adjacent areas. We performed nutrient extractions of each soil sample and analyzed them using standard methods, resulting in per-gram concentrations of nitrate, phosphorous, and ammonia. We found that surface soils have greater nutrient concentrations than the subsurface, and that the lowest concentrations are in the stream channel samples. We expect to see a positive relationship between soil nutrient content and burn severity, and for the concentrations of control samples to be an order of magnitude below their burned counterparts. The relationship between burn severity and degree of remineralization will allow us to investigate how post-burn landscape characteristics impact downstream water quality. The chemically altered water exiting burned watersheds can impact the environmental health of downstream ecosystems as nutrients increase primary productivity and change food web dynamics, affecting fish populations and reservoir chemistry. Beyond fish health, the water quality of downstream reservoirs is essential to the health and well-being of humans and animals alike.

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