PNNL

The Science

Wildfires can change how nutrients, such as phosphorus (P), move through the environment. Although P is vital for plants and animals, scientists still don’t fully understand how the burning of vegetation affects the molecular form of P and its movement over or through the landscape, particularly in streams. A multi-institutional team studied P concentrations and composition following experimental burning at different burn severities for vegetation representing two common Pacific Northwest landscapes: Douglas fir forests and sagebrush shrublands. Higher-severity fires increased the amount of P in burned material, changing it into forms that dissolve less easily in water; this effect was considerably greater in the sagebrush shrublands habitat. As a result, following higher-severity wildfires, P primarily moves in the environment in solid particles rather than in the dissolved phase. The findings improve understanding of how P is transported following wildfire, and this helps fill gaps in current model representations of P in the landscape and in streams following fire.

The Impact

This research showed that both the type of vegetation and how severely it burns control the form of P and its potential movement from land to water after wildfires. Advanced instruments from the Department of Energy’s Environmental Molecular Sciences Laboratory at Pacific Northwest National Laboratory (PNNL) and Stanford Synchrotron Radiation Lightsource National Accelerator Laboratory were used to identify how the chemical form of P changed across a range of different burning conditions. These details matter because not only is the amount of P important, but its chemical form affects how easily plants and microbes can use this nutrient. By exploring P chemistry, the research team provided a clearer picture of its environmental fate after a wildfire event.

Summary

Wildfires affect how P, an essential nutrient, cycles through ecosystems. However, it has been unclear how different burn severities and vegetation types influence the chemical forms of P and how P moves through the environment. A multi-institutional team of researchers conducted experimental burns on Douglas fir forest and sagebrush shrubland vegetation to generate charred materials across a range of burn severities. They then analyzed the P content and composition in both solid residues and water-extractable forms. Using nuclear magnetic resonance and X-ray absorption near-edge structure spectroscopy, the team tracked how P compounds transformed during burning.

The team found that P concentration increased in charred material with higher burn severity, but the chemical forms of P became less water soluble. Organic P compounds, like DNA and phospholipids, were thermally broken down and replaced by inorganic compounds containing P that was primarily associated with calcium and magnesium. These changes reduced P concentration in the dissolved phase. Importantly, compared with the Douglas fir forest, the sagebrush shrubland showed stronger responses at lower burn severities, suggesting that vegetation type alters how fire affects nutrient dynamics. This research provides new insights into postfire P dynamics, which should help improve predictions of wildfire impacts on watershed systems.

The initial draft of the text above was created using ChatGPT (version 5.5 or lower, OpenAI). The language and content were subsequently edited by the author for grammar, clarity, and accuracy, and the final document was reviewed by the author.

Research Contact

Allison Myers-Pigg, Pacific Northwest National Laboratory

James Stegen, River Corridor, Pacific Northwest National Laboratory

Funding

This research was supported by the Department of Energy, Office of Science, Biological and Environmental Research program, Environmental System Science program. This contribution originates from the River Corridor Scientific Focus Area project at Pacific Northwest National Laboratory (PNNL). A portion of this research was performed at the Environmental Molecular Sciences Laboratory user facility, located at PNNL. PNNL is operated by Battelle Memorial Institute for the Department of Energy. A portion of this research was performed at the Stanford Synchrotron Radiation Lightsource National Accelerator Laboratory user facility.

Related Links

Grieger, S., P. Aronstein, J. Bailey, M. Barnes, R. Barton, K. D. Bladon, R. Chu, B. Forbes, V. A. Garayburu-Caruso, E. B. Graham, A. E. Goldman, K. Homolka, W. Kew, A. S. Lipton, S. A. McKever, K. M. Munson, C. R. Myers, N. Nieto-Pereira, P. O’Day, O. Otenburg. 2022. Organic matter concentration and composition of experimentally burned open air and muffle furnace vegetation chars across differing burn severity and feedstock types from Pacific Northwest, USA (v3). River Corridor and Watershed Biogeochemistry SFA, ESS-DIVE repository. Dataset. doi:10.15485/1894135 accessed via https://data.ess-dive.lbl.gov/datasets/doi:10.15485/1894135

Barnes, M. E., P. J. Aronstein, J. D. Bailey, K. D. Bladon, B. Forbes, V. A. Garayburu-Caruso, S. Grieger, E. B. Graham, S. A. McKever, C. R. Myers, K. M. Munson, P. A. O'Day, B. Powers-McCormack, L. Renteria, A. Roebuck, T. D. Scheibe, R. P. Young, and A. N. Myers-Pigg. 2024. Data and scripts associated with: “Burn severity and vegetation type control phosphorus concentration, molecular composition, and mobilization.” River Corridor Hydro-biogeochemistry from Molecular to Multi-Basin Scales SFA, ESS-DIVE repository. Dataset. doi:10.15485/2547035 accessed via https://data.ess-dive.lbl.gov/datasets/doi:10.15485/2547035 on 2025-05-22

River Corridor Science Focus Area PNNL web page